SEWAGE TREATMENT PLANT

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1. Introduction CHAPTER-I

1.1 General

Water, food and energy securities are emerging as increasingly important and vital

issues for India and the world. Most of the river basins in India and elsewhere are

closing or closed and experiencing moderate to severe water shortages, brought on

by the simultaneous effects of agricultural growth, industrialization and

urbanization. Current and future fresh water demand could be met by enhancing

water use efficiency and demand management. Thus, wastewater/low quality water

is emerging as potential source for demand management after essential treatment.

An estimated 38354 million liters per day (MLD) sewage is generated in major cities

of India, but the sewage treatment capacity is only of 11786 MLD. Similarly, only

60% of industrial waste water, mostly large scale industries, is treated. Performance

of state owned sewage treatment plants, for treating municipal waste water, and

common effluent treatment plants, for treating effluent from small scale industries, is

also not complying with prescribed standards. Thus, effluent from the treatment

plants, often, not suitable for household purpose and reuse of the waste water is

mostly restricted to agricultural and industrial purposes. Wastewater- irrigated

fields generate great employment opportunity for female and male agricultural

laborers to cultivate crops, vegetables, flowers, fodders that can be sold in nearby

markets or for use by their livestock. However, there are higher risk associated to

human health and the environment on use of wastewater especially in developing

countries, where rarely the wastewater is treated and large volumes of untreated

wastewater are being used in agriculture. Sewage is a major point source of

pollution. The target of “NirmalDhara” i.e. unpolluted flow can be achieved if

discharge of pollutants in the river channel is completely stopped. Also, sewage can

be viewed as a source of water that can be used for various beneficial uses including

ground water recharge through surface storage of treated water and/or rain/flood

water in an unlined reservoir. This may also help achieving “AviralDhara”. In order to

reduce substantial expenditure on long distance conveyance of sewage as well as

treated water for recycling, decentralized treatment of sewage is advisable. As a good

practice, many small sewage treatment plants (STP) should be built rather than a few

of very large capacity. All new developments must build in water recycling and zero

liquid discharge systems. Fresh water intake should be restricted only to direct

human‐contact beneficial uses of water. For all other uses properly treated

sewage/wastewater should be used wherever sufficient quantity of sewage is

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available as source water for such purposes. All new community sanitation systems

must adopt recycling of treated water for flushing and completely isolate fecal matter

until it is converted into safe and usable organic manure. The concept of

decentralized treatment systems and water/wastewater management will be

covered in detail in subsequent reports.

1.2 Purpose of Selection of this project

Bharuch is one of the historical towns in Gujarat state and is as district head quarter.

This very old town was mentioned in historical records nearly 2000 years ago. The

industrial activity in the town dates back to the 17th century when the English and

Dutch established factories here. In fact Bharuch is one of the oldest cities in India

and was a flourishing port in earlier times. Bharuch was also very important to the

sultans and other Muslim rulers who ruled Gujarat. It is an important place of

pilgrimage. Later on with construction of Dutch colony at Bharuch it has grown

significantly over decades.

With the expansion of Bharuch city there is rapid expansion of population too.

Previously there was less population so there was no need of waste water treatment

plant, but looking to the present scenario it became very important for govt. body to think

about it. As per 2011 census data the population was 15, 51,019 and it is growing every

year at the rate of 2.5% - 3.0% annually. at present, average daily water supply is 20

MLD in Bharuch municipality out of this 6 MLD from ground water and 16 bulk

purchase of raw water, out of this total water supply Bharuch supply 1.5 MLD to

outgrowth areas having river Narmada right at the edge of this city can benefit to its

people a lot if the river water use is effectively and economically. When we talk about

utilizing the river water the first question comes out of a sudden blink is that, how

about the water that we used?? Well, for that we at 7th sem. project work decided to

take upon the topic of “Planning & Designing of waste water treatment plant for

Bharuch City regulated by Bharuch Nagarpalika” With the implementation of this

project we can reuse & recycle the water consumption effectively and efficiently also

keeping the environment in mind.

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1.3 Necessity of treating Waste Water

There is tremendous increase in the population of Bharuch city since last 10 years.

There has been a considerable increase in population due to migration, urbanization

and industrialization. With the increase in the volume of population there has also

been increase in land use also. Along with it, there rose the need for water supply too.

It is good that the population of Bharuch city has some natural resource right as its

neighbor, so that the ever ending resource can be met easily whenever & however.

Every day we consume water supplied to us by Municipal authorities to us. We utilize

it, but very few think about the succeeding step or next step. One easily walks out of

bathroom after finishing bath or washing utensils.

In the same way the clean palatable & potable water is also supplied to hospitals,

Industries big refractory. They utilize it and then dispose the water directly to the

river without thinking for even once.

All this cause a great damage and creates a negative impact on environment. There is

life ab0ve water and another below to it. We humans try to keep one side intact by

damaging other. We all in our unawareness fall in the same ecological cycle, which

shows us that we have to be dependent on each other to sustain. River Narmada can

unpollute all the wastes that have been discharged into it. But it will take decades to

go. So, it became important rather necessity to establish or construct waste water

treatment plant for the conservation and preservation of natural resource.

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2. Literature Review

Jillies and Kushwaha (1990) reported that liquid digested sludge can be used as

soil amendment to provide low cost fertilizer and improve tilth. Dried digested

sewage sludge was mixed with soil in test plot near Saskatoon, Canada at application

rate of 75 tones sludge/hectare. The plots were irrigated with decent water from the

sludge drying bed.

Tripathi and Dwivedi (1990) reported that the effect of irrigation with raw urban

sewage effluents mixes with industrial effluents, treated sewage effluents and tube

well water potato yield plant and soil heavy metal content was studied in a field

experiment at Banaras Hindu university, Varanasi. Very low concentrations of heavy

metals were observed in rubbers from the raw sewage irrigation treatment, although

Cu, Zn, Fe in soil increased.

Korentajer (1990) reported the application of sewage sludge on agricultural land

may provide an economical way to dispose of the increasing amount of sludge

application may be limited by its potential health.

Hundal and Sandhu (1992) reported that soil sample at varying distance along the

sewage from three tiers of field sewage waste water irrigated and tube well irrigated

were collected and analyzed for total and DTPA extractable toxic metal content.

Maiti et al. (1992) reported that the sewage effluent and sludge of Calcutta city was

made to assess their manorial values. Sewage were natural to slightly alkaline in

reaction and contained high level basic tons, particularly in winter, bicarbonate and

chloride Ions were at toxic levels. Although sewage effluents and slugged were rich in

nutrient the toxicity levels.

Welch et al. (1992) reported the zinc movement in sludge treated soils as

influenced by soil properties water quality and soil moisture level.

Hundal et al (1993) reported that the surface soil samples were collected from field

along a sewage drains which were irrigated with sewage effluents sewage effluents

plus tube well water or tube well water and their chemical properties were

investigated. Zinc and copper contents increased 3 and 8 times respectively in the

sewage effluents treated soils reaching toxic levels to plants.

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Azad (1995) reported that the fate of Fe in sewage wastewater irrigated soil was

investigated in Punjab India. Total Fe content of normally irrigated soil ranges from

1.4-3.2% in the 0-15 cm layer with mean value of 2.03% in soils receiving sewage

wastewater total Fe ranges from 2.2-4.1% with an average value 2.78% which was

36.9% higher than in normal soils.

Mathan (1995) reported that the study conducted in a sewage farm of the Madurai

Corporation in India to compare the effect of sewage effluent properties. The soil was

sandy loam and had been irrigated for 10-15 years. Soil irrigated by canal fed well

water had the highest bulk density.

Kuba et al. (1997) examined the role of denitrifying phosphorus removing bacteria

(DPB) in wastewater treatment plants using batch tests with activated sludge from

two plants in the Netherlands. DPBs appeared to be of little importance in one plant,

but contributed substantially to P removal in the other

Singh and Varloo (1997) studied the accumulation and bioavailability of metals in

semi arid soil irrigated with the sewage effluent, the sewage had slightly lower pH

but higher organic carbon as compared to those receiving irrigation with tube well

water.

Antil et al. (1998) reported that the raw sewer water sample was collected from

various Sewer disposal sites in Haryana India where these waste water are directly

used for irrigating the crops. The chemical composition of sewer water varied from

site to site. The physicochemical properties DTPA extractable and total macro and

micronutrients and toxic the composition metals icons (CD,Ni) varies according to

composition of the sewer water.

Wiger and Hamedi (1999) reported that accumulation and mobility heavy metals

in soils irrigated with sewage effluent in Haryana India.

Bednared and Tkaczy (1999) reported that the influence of treated municipal on

occurrence of soluble form of phosphorous potassium and magnesium in peat muck

soil. Municipal sewage did not change in reaction and value of hydrolytic acidity.

Treated municipal sewage caused contents of soluble potassium in upper layer (0-

20) of soil.

Joshi and Pathak (2000) reported that the effect of sewage assessing the effect if

sewage application on sewage application on soil properties identified the problem.

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Song et al. (2002) using thermodynamics, modeled the effects of P and Ca

concentration, pH, temperature, and ionic strength on theoretical removal.

Tchobanoglous et al (2003) Chemical precipitation has long been used for P removal. The chemicals most often employed are compounds of calcium, aluminum, and iron. Bradford et al. (2003) In the villages near Hubli-Dharwad in Karnataka, the main

wastewater irrigated agro forestry land uses are orchards and agrosilviculture which

consists of spatially mixed tree–crop combinations.

Zeng et al. (2004) High phosphate removal (> 95% in 10 min, batch system) was

obtained from a 33 mg/L P solution, but direct applicability to wastewater treatment

(lower concentrations, possible interferences) was not investigated. The gas

concrete’s removal efficiency can be regenerated at low pH, with the resulting

concentrated phosphate solution potentially a source of recycled phosphate.

Similarly, iron oxide tailings were found to be effective for phosphorus removal from

both pure solutions and liquid hog manure

Chattopadhyay (2004) The East Calcutta sewage fisheries are the largest single

wastewater use system in aquaculture in the world. The wetland ecosystem of

Kolkata supports 100,000 direct stakeholders and 5,100 ha of cultivation. Annually, it

provides direct employment for about 70,000 people, produces 128,000 quintals of

paddy, 69,000 quintals of fish and 7.3 quintals of vegetables.

Neethling et al. (2005) examined the factors that influence the reliability of EBPR in

full- scale plants. They concluded that P “concentrations <0.1 mg/L can be achieved

for extended periods (more than a month), 0.03 mg/L for a week, and even below

0.02 mg/L for several sequential days. Excursions above these levels are common.” A

sufficient BOD/P ratio (>25:1) is one requirement for reliable high removal

efficiencies. This might be achieved by BOD augmentation through fermentation or

addition of a fermentable substrate. Control of recycle streams is also necessary, so

that they do not bring too much P back to the EBPR process. They also concluded that

while GAOs can be problematic, their presence does not preclude good P removal.

Mekala (2006) In Hyderabad, along the Musi River about 10,000 ha of land is

irrigated with wastewater to cultivate Para grass, a kind of fodder grass.

Randall (2006) discussed the use of carbon augmentation in EBPR. Short chain

volatile fatty acids (VFAs), particularly acetic and propionic acids, are most desirable.

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Some carbon sources, such as some sugars and alcohols, may lead to production of

GAOs, bulking, or excessive exocellular polymer production. VFAs may be generated

in the sewer system, arise from industrial discharges, be added directly, or be

generated on-site. For many plants, on-site generation in the anaerobic zone may be

sufficient. Alternatively, fermentation of the primary sludge, primary effluent, or

some of the activated sludge might be practiced. In the PhoStrip process,

fermentation also occurs in the stripping tank.

Reardon (2006) reported on several plants achieving <0.1 mg/L TP in their effluent,

and suggested the current reliable limits of technology are 0.04 mg/L for MBRs and

tertiary membrane filtration, and 0.008 mg/L for RO.

Reardon, (2006) in plants with EBPR the P content is even higher. Thus sand

filtration or other method of TSS removal (e.g., membrane, chemical precipitation) is

likely necessary for plants with low effluent TP permits.

Strom, (2006) Assuming that 2-3% of organic solids is P, then an effluent total

suspended solids (TSS) of 20 mg/L represents 0.4-0.6 mg/L of effluent P

Neethling and Gu, (2006) Chemical addition points include prior to primary

settling, during secondary treatment, or as part of a tertiary treatment process.

Neethling and Gu, (2006) the process is more complex than predicted by laboratory

pure chemical experiments, and that formation of and sorption to carbonates or

hydroxides are important factors. In fact, full-scale systems may perform better than

the 0.05 mg/L limit predicted.

Strom, (2006) Use of alum after secondary treatment can be predicted to produce

much less sludge, but the increase could still be problematic.

Moller (2006) reported on an iron reactive filtration system achieving <0.01 mg/L

TP at a 1.2 MGD (average flow) plant. Woodard (2006) described a magnetically

enhanced coagulation process that may achieve <0.03 mg/L TP based on long term

pilot tests.

James Barnard (2008) developer of the Bardenpho process, recently moderated a

session on the capabilities and constraints of EBPR, and discussed the requirements

for achieving effluent P concentrations <0.1 mg/L. He emphasized the need for

production of volatile fatty acids by fermentation in order to assure their availability

for the PAOs. Some of the factors contributing to the difficulty of achieving very low

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levels of both N and P simultaneously were pointed out, including secondary release

of P in anoxic zones. The need to select for PAOs over the competing glycogen

accumulating organisms (GAOs) was also discussed, with the following factors

favoring GAOs: high sludge age, high temperature, longer un-aerated detention times,

stronger wastes with low organic N, polysaccharides fed to the anaerobic zone, and

low pH.

Narayanan (2009) There is some concern about the effects of solids management

processes and returns side streams on the ability to remove P to low levels.

Processes that destroy organic material (such as digestion) have the potential to

release the particulate organic-P present as soluble organic or inorganic P. In

particular, anaerobic conditions are likely to release soluble P from EBPR sludge and

iron precipitates (ferrous phosphate is much more soluble than ferric phosphate).

Any released P may then be returned to the main wastewater treatment process in

high concentrations through recycle side streams, thus requiring removal a second

time. Non-continuous processes may also lead to variable loadings from side

streams.

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3. Patent Search Analysis Report

3.1 Bio-augmentation composition and use thereof for improving efficiency of effluent treatment in hydrocarbon processing plant

Their study stated that a bio-augmentation composition for improving the

hydrocarbon degradation efficiency of effluent treatment plant for hydrocarbon

degradation in wastewater generated from hydrocarbon processing industry and a

method thereof. The composition comprises a synergistic combination of selective

microorganisms to develop a consortium enabling effective degradation of

hydrocarbons present in wastewater and converting thereof into harmless and

environment friendly substances. The invention also provides for the said

microorganisms and their isolations

3.2 A water clarifier

According to their invention, it comprises a chamber (C) accommodating a plurality

of spaced plates (P), placed one against the other, each plate having an aperture (A)

at the center, the plates (P) fully spanning the chamber (C); a grill (G) fixed, at an

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inclination, to each piate (P), over the aperture (A), for enabling the water, required

to be clarified, to pass there through and cause the solids in the water to be

separated, while the space (S) between the plates (P) creates a turbulence in the

water as it passes from one grill (G) to another, the turbulence simultaneously

flocculating the water in the said space (S); an inlet for the entry of the water to be

clarified into the chamber (C), and an outlet for the exit of the clarified water from

the chamber (C).

3.3 An apparatus for removing solid particles from a liquid

An apparatus for removing solid particles from a liquid, comprising: a round shell

having an inlet located within said shell and an outlet located within said shell, said

outlet being elevated from said inlet, said shell deforming a particle extraction area;

an outlet fume extending from said outlet and having a floor overhanging at least a

portion of the particle extraction area; and a particle collection area located centrally

of said particle extraction area; wherein said inlet comprises a vertical inner wall

that extends upwardly a distance within said shell so as to direct liquid tangentially

into said shell and preclude communication between the liquid in the inlet and the

liquid in the particle extraction area.

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3.4 Scraper Raising system

This invention relates to the scrapper raising system of settling tanks. The scrapper

- raising system for a settling tank comprising a vertical suspension having an

upper member and lower member wherein said upper member is rigidly fixed to a

rotating bridge of the settling tank and said lower member is pivotally adapted to

the upper member, a scrapper connected to the lower member, and a lifting means

attached at or near the lower end of the lower member for raising and lowering the

scrapper wherein said lifting means raises the scrapper in a direction substantially

orthogonal to thrust developed by the scrapping force of the scrapper.

3.5 Self-sustained bio-digester for onboard degradation of human waste

This invention relates to the field of human waste handling, treatment and disposal in mobile public carriers. In particular the invention is directed to a self- sustained bio- digester for onboard degradation of human waste. Said bio-digester comprising

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at least three components; biological treatment component, chemical treatment component; and non-biodegradable materials elimination component

3.6 A biogas digester cover with brackets

A biogas digester cover with brackets, includes: a cover body with a gas nozzle,

wherein: at least two brackets for fixing the cover body inside the opening of the

digester are provided on the lower edge of the cover body. The biogas digester

cover with brackets of the present invention is scientific in design, reasonable in

structure, and convenient in application. By making use of the brackets that are

installed around the opening of the cover body, the gas cover can be handily fixed

inside the opening of the digester with pins. Not only does the present invention

have the functions of the removable gas covers in prior art and satisfy the

requirements of normal use, but also overcomes the defects of the removable gas

covers in the prior art, such as overall strict requirements of material, high

production cost and short life-span. The present invention is a removable gas cover

that better satisfies the application requirements.

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4. Bharuch Town Profile

4.1 Town Profile

Bharuch town is the headquarters of Bharuch district and one of the historical towns

in Gujarat state and is as District Head Quarter. This very old town was mentioned in

historical records nearly 2000 years ago. The industrial activity in the town dates

back to the 17th century when the English and Dutch established factories here. In

fact Bharuch is one of the oldest cities in India and was a flourishing port in earlier

times. The oldest dockyard in the country was developed in this town for import and

export of precious stones available in the region.

Bharuch was once but a small village on the banks of the Narmada River but that

rivers inland access to central and northern India and with a location in the sheltered

Gulf of Khambat in the era of coastal sea travel grew and prospered as a trading

transshipment centre and ship building port. Until very modern times the only

effective way to move goods was by water transport, and Bharuch had sheltered

waters in a era without weather forecasting, compasses, and when shipping was

necessarily limited to coastal navigation, and the general East-West course of the

Narmada gave access to the rich in land empires at the upper reaches of the

Narmada, including easy caravan access to the Ganges valley and Delhi plain,

4.2 Geography

Topographic Map of India, clearly showing the rare West to East access given to the

North and Central river line valleys by the Narmada River from Bharuch. The

Narmada River outlets into the Gulf of Khambat through its lands and that shipping

artery gave inland access to the kingdoms and empires located in the central and

northern parts of the subcontinent of India. Level of difference of the city is from 33

m to 5 m in city.

4.3 History and Culture of Bharuch

This Bharuch is one of the historical towns in Gujarat state and is as District Head

Quarter. This very old town was mentioned in historical records nearly 2000 years

ago. The industrial activity in the town dates back to the 17th Century when the

English and Dutch established factories here. In fact Bharuch is one of the oldest

cities in India and was a flourishing port in earlier times. The oldest dockyard in the

country was developed in this town for import and export of precious stones

available in the region. Bharuch was also very important to the sultans and other

Muslim rulers who ruled Gujarat. There is an ancient mosque called Masjid-U-Jani in

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Bharuch. It is an important monument to study Islamic Architecture in Gujarat.

Shukaltirth and Kabirvadare two important picnic spots which are located at a

distance of 16 and 18 Kms. respectively from Bharuch. On Janmastami, huge fairs are

organized here. At present, there is a temple of Lord Shiva located near the Sardar

Bridge built on river Narmada near Jhadeshwar on the eastern part of Bharuch. It is

an important place of pilgrimage. Devotees flock this place during the month of

Shravan. The Golden bridge constructed by British ruler, is famous engineering

structure of Bharuch. The first British colony was established in Bharuch in 1616 and

then in 1617, the Dutch colony was established. Thereafter, Aurangzeb built a strong

protective wall around the city and gave it the name Shukabad. In 1772, it came

under the British Rule.

Bharuch has been situated at Narmada river so it has nos. of religious place within it

including temples, churches, mosques, Jain shrines &Parsi Agiyari. Temples like

Kotilingeshwar Mahadev, Kapileshwar mahadev, Mota Baliyadev, these temples are

not very old. In Dandia bazaar Swaminarayan temple was built in V.S. 1891 (A.D.

1835), it was built up in memory of Sahjanand Swami. In the middle of the town

there is a temple of Bhrugu Bhargeshwar which is known as Nava Dera, houses

Vaishnav Haveli of Narayan Dev. In Ali area, famous temple of Sindhavai Mata is

situated. Behind Sewashram there is an ancient temple of Nilkanth Mahadev and it is

believed that it was constructed in 19th century. Near Pakhali Ovara area, a famous

temple of Kamnath Mahadev and here nine planets‟ statues are there, so it is also

famous as a “Nine planets temple”

Besides above places mention, the other heritage monuments which exist in Bharuch

city are:

a) Grave of Sufi –Saint “Dada Rehan”

b) Ancient Farsi stone with inscriptions of Umad-Ui-Mulk

c) Fort of King Siddhraj Jay Sinhji – constructed during the Solanki period (1094 to

1143)

d) 400 year old LalluChowk’s Haveli famous for its wooden carvings.

The temple of 4 Veds (oldest sacred books of the Hindus) – Ruguvved, Atharvved,

Yajurvved, Samved and the only temple having the statues of four Veds with

iconography In Bharuch city the Jain shrines of Kavi, Gandhar and Zagia are situated.

Bharuch city Jama Masjid which was founded in 1326 AD is still in existence and near

civil hospital there is mosque founded by Murtazkhan in the year 1609 AD is also in

existing with good wooden columns and the windows having wooden carvings. In

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Bharuch city, Parsi people have noticeable population and for their prayer and

worship purpose there are seven Agiyaris in the town. Among all seven Agiyaris,

Pestanji‟sagiyari is the oldest.

In the year 1814, Roman Catholic Church scent was founded, called “Our lady of

Health”, this was destroyed in the year 1860 and the same Church was reconstructed

in the year 1887. In the year 1856, Protestant people had founded their church.

4.4 City Map

Fig.1 Bharuch City Map

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5. Present Scenario Of Bharuch city

It is absolutely necessary to go for establishing Sewage Treatment Plant to upgrade

the status of sanitation of the municipality area from the consideration of health

ground. As in Bharuch town, there is no underground drainage system in city and the

system of septic tanks and soak pits for latrines in the household is being used for the

disposal of sludge at the household level. For slum areas, the toilets having low cost

sanitation are being provided by constructing the soak pits and septic tanks and the

subsidy provided by the municipality.

The amount of sewage generated in Bharuch is about 37.91 MLD i.e. approximately

80% of the daily water supply of 47.41 MLD. At present Bharuch city has no

sewerage system and most of the houses have their own septic tanks and soak pits.

Most of which are located below the road levels in gametal areas. The existing

sewerage system in Bharuch city is open and unhygienic within the city and having

high population density. Due to presence of black cotton soil, the permeability is low

hence over flow from the septic tanks and soak pits is common problem. The flow

from these soak pits is discharged into the nearby natural nalla (ravine) and finally

the untreated wastewater is directly flowing into the river Narmada. The undulating

topography of gametal area, the sewage water and sludge is not effectively drained

off. The natural drains passing through the city get filled up during the development

process and together with storm water; and also the drainage problem turns out to

be a major issue during the rainy season. During rainy seasons the water overflows

on the roads, which are already uneven, the traffic movement is greatly affected and

damages to the properties also occur in gametal area. Due to the unhygienic disposal

of sewage, mosquito / flies nuisance is prevailing in most of the areas. The Bharuch

municipality is constructing the open drain system for disposal of sewage water in

gametal area. The rubbish of the city and human excreta are disposed off outside the

city through night soil tankers. There are 327 public latrines in different areas of the

city.

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6. Waste water Treatment

The principal objective of wastewater treatment is generally to allow human and

industrial effluents to be disposed of without danger to human health or

unacceptable damage to the natural environment. However, some degree of

treatment must normally be provided to raw municipal wastewater before it can be

used for agricultural or landscape irrigation or for aquaculture. The quality of treated

effluent used in agriculture has a great influence on the operation and performance

of the wastewater-soil-plant or aquaculture system. In the case of irrigation, the

required quality of effluent will depend on the crop or crops to be irrigated, the soil

conditions and the system of effluent distribution adopted. Through crop restriction

and selection of irrigation systems which minimize health risk, the degree of pre-

application wastewater treatment can be reduced.

6.1 Composition of waste water and its effect Domestic Wastewater (from homes, offices, hotels, institutions) comprises sewage

(human waste) and grey-water from bathrooms, kitchens, laundries.

Industrial Wastewater is the liquid discharge from manufacturing processes; for

example soft drink and beer companies; sugar processing; metal processing; photo

finishing.

Waste water is a mixture of wastes from industrial, domestic, pharmaceutical, hotels

and commercial areas.

The Composition of sewage refers to the actual amount of various constituents of

waste water. The composition of waste water largely depends on the source from

which it is obtained. Those compositions of domestic sewage which comprises spent

water from kitchen, bathroom, laboratory, etc. will be different from that of

industrial sewage which in turn will depend on the type of industry. Moreover,

depending on the concentration of various constituents, the domestic sewage maybe

classified as strong, medium an weak. Table 4.1 shows typical composition of

untreated domestic sewage. Both the constituents and the concentration vary with

the hour of the day, the day of the week, the month of the year and other local

conditions. Therefore their data in table below, is only to serve only as a guide and

not as a basis for a design.

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Table 1: Typical Composition of Untreated Domestic Sewage

They are composed of Biological, Chemical & Physical wastes constituting various

toxic substances and harmful chemicals.

Constituent Concentration

Strong Medium Weak

1. Solids, total: (mg/l)

Dissolved , total (mg/l)

Fixed (mg/l)

Volatile (mg/l)

Suspended, total (mg/l)

Fixed (mg/l)

Volatile (mg/l)

1200

850

525

325

350

75

275

720

500

300

200

220

55

165

350

250

145

105

100

20

80

2. Settleable solids (mg/l) 20 10 5

3. Biochemical oxygen demand,

5-day, 20.c, (BOD520.c)

(mg/l)

400

220

110

4. Total organic carbon (TOC) (mg/l) 290 160 80

5. Chemical oxygen demand (COD) (mg/l) 1000 500 250

6. Nitrogen, total as N: (mg/l)

Organic (mg/l)

Free ammonia (mg/l)

Nitrites (mg/l)

Nitrates (mg/l)

85

35

50

0

0

40

15

25

0

0

20

8

12

0

0

7. Phosphorus, total as P: (mg/l)

Organic (mg/l)

Inorganic (mg/l)

15

5

10

8

3

5

4

1

3

8. Chlorides (mg/l) 100 50 30

9. Alkalinity (as CaCO3) (mg/l) 200 100 50

10. Grease 150 100 50

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6.2 Characteristics of waste water

Table 2: Physical, Chemical and Biological Characteristics of Sewage and their

Sources

Characteristic Sources

1. Physical properties:

Colour

Odour

Solids

Temperature

Domestic and industrial wastes, natural decay of organic

materials

Decomposing wastewater, industrial waste

Domestic water supply, domestic and industrial wastes, soil

erosion, inflow-infiltration

Domestic and industrial wastes

2. Chemical constituents:

(a) Organic

Carbohydrates

Fats, oils and

grease

Pesticides

Phenols

Proteins

Surfactants

Others

(b) Inorganic

Alkalinity

Chlorides

Heavy metals

Nitrogen

Ph

Phosphorus

Sulphur

Toxic compounds

(c) Gages:

Hydrogen sulphide

Domestic, commercial and industrial wastes

Domestic, commercial and industrial wastes

Agricultural wastes

Industrials wastes

Domestic and commercial wastes

Domestic and industrial wastes

Natural decay of organic materials

Domestic wastes, domestic water supply, groundwater

infiltration

Domestic wastes, domestic water supply, groundwater

infiltration

Industrial wastes

Domestic and agricultural wastes

Industrial wastes

Domestic and industrial wastes, natural runoff

Domestic wastes, domestic water supply, industrial wastes

Industrial wastes

Decomposition of domestic wastes

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Methane

Oxygen

Decomposition of domestic wastes

Domestic water supply, surface water infiltration

3. Biological constituents:

Animals

Plants

Protista

Viruses

Open watercourses and treatment plants

Open watercourses and treatment plants

Domestic wastes, treatment plants

Domestic wastes

Table 3: Components of waste water characteristics

Main components of waste water characteristics

Physical-Chemical Parameters Importance

Temperature ̊C Affects chemical reactions and reaction rates. Low temperature affects bacterial growth.

Turbidity pH Affects chemical biochemical reactions as biological activities

pH

Turbidity Due to presence of colloidal matter. When high SS concentration present in WW, it could be resistant to removal when treating under anaerobic conditions..

Suspended Solids

Hydrolysis of suspended solids may be the rate limiting step under anaerobic conditions especially at low temperatures. They also cause disintegration of granular sludge and results in lower methanogenic activity.

Particle Size Distribution Affects conversion kinetics of the suspended solids

Polymeric Constituents (COD)

They consist mainly of carbohydrates, constituents’ proteins and lipids and should be removed with treatment. They constitute. The main part of the COD of wastewater.

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Refractory organics

These compounds tend to resist conventional wastewater treatment. Typical examples are surfactants, phenols and agricultural pesticides. The presence of surfactants also affects stabilization of colloids and the surface properties of particles.

Priority Pollutants

Organic and inorganic compounds selected on the basis of their known or suspected carcinogenic, high acute toxicity. Many of these compounds are found in wastewater.

Sulphate High concentration causes inhibition of methanogenesis.

Chloride It may have an impact on the final use of treated wastewater.

Heavy Metals Toxic to bacterial impact on environment.

Nutrients Macro (N,P,K) and micronutrients

Important for biological treatment processes.

Biological parameters Includes pathogenic microorganisms, and all other organisms participating in biological conversions.

6.3 Ill effects of waste water on human & Environment and related FAQ’s

Why Every Community Needs Wastewater Treatment?

Even if controlling gases and odors from sewage weren't reason enough, every community needs to treat its wastewater because of the serious health problems it can cause. Although this may seem obvious, untreated wastewater is still the root cause of much environmental damage and human illness, misery, and death around the world. Sometimes it is useful to reexamine basic ideas like why wastewater treatment is important, especially today when so many communities need to save money and reprioritize their needs and funding for public projects.

What is in wastewater?

Sources of wastewater from small communities include homes, farms, hospitals, and businesses. Some communities have combined sewers that collect both wastewater and storm water runoff from streets, lawns, farms, and other land areas. So wastewater can include any debris from streets and waste oils, pesticides, fertilizers, and wastes from humans and animals. Wastewater from a typical household might

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include toilet wastes; used water from sinks, baths, showers, washing machines, and dishwashers; and anything else that can be put down the drain or flushed down the toilet.

What makes wastewater so dangerous?

Feces and urine from both humans and animals carry many disease-causing organisms. Wastewater also may contain harmful chemicals and heavy metals known to cause a variety of environmental and health problems. Disease-causing organisms (pathogens) from humans can enter a community's wastewater from patients at hospitals, or from anyone who is sick or a carrier of disease. Carriers may not have symptoms or even know they have a disease. Animal wastes often enter from farms, meat packing and processing facilities, and from rats and other animals found in or around sewage or sewers.

Much of our wastewater, treated or untreated, eventually ends up in our rivers, streams, lakes, and oceans-sometimes via groundwater, the underground water source we tap for well water. We often assume that groundwater is pure-and it usually is-but unfortunately, well water contaminated by sewage is a common cause of outbreaks of wastewater-related diseases.

When untreated wastewater reaches water used as a drinking water source for the community, there can be significant health risks. The effectiveness of drinking water treatment can be reduced when water is heavily contaminated with waste. To ensure safe drinking water, communities need both effective water and wastewater treatment. In addition, communities need to make sure that untreated wastes are not disposed of improperly on land where people can come in direct contact with it or where it can attract disease-carrying insects or animals.

How are Diseases Spread from Wastewater?

Humans "catch" diseases from wastewater in a variety of ways. Pathogens in wastewater may be transmitted by direct contact with sewage, by eating food or drinking water contaminated with sewage, or through contact with human, animal, or insect carriers.

For example, direct contact might accidentally occur as a result of walking in fields fertilized with untreated wastes, playing or walking in a yard with a failed septic system, touching raw sewage disposed of in open areas, swimming or bathing in contaminated water, or working with or coming into contact with animals or wastewater and not following proper hygiene.

Houseflies can be used to illustrate the dangers posed by disease carriers. Flies, which have tastebuds on their feet, always land directly on the food they eat-and on any given day, that could mean raw sewage (a fly favorite) followed by picnic food. The hairs on a housefly's body can carry millions of pathogens, which then brush off on anything the fly touches. By making sure that wastewater is treated and disposed of properly, communities can control the spread of disease by flies and other disease

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carriers, such as rats, lice, cockroaches, and mosquitoes. By controlling the population of these animals and insects, communities also help to control the other, non-wastewater related diseases they may carry. But by far the most common way that people contract diseases from wastewater is through the fecal-oral route, or in other words, by eating food or drinking water contaminated by sewage or by not washing hands after contact with sewage.

In communities where wastewater treatment is inadequate or nonexistent, the opportunities for people to become infected seem endless. For example, people have become ill by doing the following:

Drinking contaminated water, juices made with water, or other beverages made with contaminated water or ice

Eating food improperly handled by infected people or carriers (often workers in restaurants or food processing facilities)

Eating vegetables and fruits contaminated by irrigation with polluted water or fertilized with untreated sewage or sewage sludge

Eating meat or drinking milk from animals that grazed on contaminated pasture or drank contaminated water

Eating fish or shellfish grown, caught, or harvested in contaminated water Eating food exposed to flies or vermin that feed on or come into contact with

sewage

Diseases contracted by drinking contaminated water or eating contaminated food are often referred to as waterborne and food borne diseases.

What Diseases Are Commonly Caused By Wastewater?

Bacteria, viruses, and parasites (including worms and protozoan’s), are the types of

pathogens in wastewater that are hazardous to humans. Fungi that can cause skin,

eye, and respiratory infections also grow in sewage and sewage sludge. Scientists

believe there may be hundreds of disease-causing organisms present in sewage and

wastewater that have yet to be identified.

Diseases Caused by Bacteria

Bacteria are microscopic organisms that are responsible for several wastewater

related diseases, including typhoid, paratyphoid, bacillary dysentery, gastroenteritis,

and cholera. Many of these illnesses have similar symptoms, which vary in severity.

Most infect the stomach and intestinal tract and can cause symptoms like headache,

diarrhea (sometimes with blood), abdominal cramps, fever, nausea, and vomiting.

Depending on the bacteria involved, symptoms can begin hours to several days after

ingestion. Often, infected people will experience only mild symptoms or no

symptoms at all. However, anyone experiencing frequent diarrhea and vomiting

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should seek medical attention immediately. Severe dehydration and death can result

with serious cases, sometimes within a day.

Typhoid

Early in this century, typhoid fever was a major cause of death from outbreaks of

waterborne disease in this country. Today, water and wastewater treatment has

almost eliminated this highly infectious disease in developed countries, but it

continues to be a problem in many areas of the world. Typhoid symptoms often

include fever, constipation, loss of appetite, nausea, diarrhea, vomiting, and

abdominal rash. An outbreak of typhoid fever was reported in Ain Taya, Algeria, with

910 suspected cases. The cause was traced to sewage contaminating the water

reservoirs after a sewage pipe had been damaged during construction work.

Cholera

Cholera is another waterborne bacterial disease that used to be responsible for

recurring outbreaks in the U.S. It is again a threat in much of the world. Cholera

spreads quickly, especially in areas where people live in crowded conditions without

toilets or clean water. Outbreaks also result from people eating contaminated

seafood.

Since 1961, there has been a devastating global epidemic of cholera, which spread to

this part of the world in 1991. A Chinese freighter that dumped its wastewater into

the harbor at Lima, Peru, is suspected of having brought the disease to Latin America

for the first time in more than 100 years. The epidemic quickly spread to Ecuador,

Colombia, Chile, and north to Mexico. At least 10,000 deaths and 1 million cases have

been reported to the Pan American Health Organization from Latin America alone.

Because cholera can be controlled with water treatment and boil-water advisories, a

massive outbreak is unlikely in the U.S. However, smaller, isolated outbreaks have

occurred. Oyster beds contaminated with cholera bacteria were found in Mobile,

Alabama, in 1991 and were closed by health officials. Other small outbreaks in the

U.S. originated from travelers eating contaminated seafood or seafood brought home

in suitcases.

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Diseases Caused By Viruses

Viruses are microscopic parasitic organisms. They are smaller than bacteria and can

be seen only with an electron microscope. Some can infect people through

wastewater. Viruses can't multiply outside their hosts, and wastewater is a hostile

environment for them. But enough viruses can survive in water to make people sick.

Hepatitis A, polio, and viral gastroenteritis are a few of the diseases that can be

contracted from viruses in wastewater. Viral gastroenteritis is thought to be one of

the leading causes of illness in the U.S.

There may be as many as 100 different virus types present in raw sewage, but they

are difficult to identify. Much is still not known about the viruses and other

pathogens in wastewater or their exact behavior and effect on humans. According to

the U.S. Environmental Protection Agency, tests using DNA to help detect and identify

viruses are being developed.

Parasites in Wastewater

Until recently, most Americans haven't been concerned about parasites in their

drinking water. But in the past few years, well-publicized outbreaks of giardiasis

(caused by the protozoan Giardia lambia), and cryptosporidiosis (caused by the

protozoan Cryptosporidium) have brought attention to these organisms.

The types of parasites found in wastewater include protozoan’s and helminthes

(parasitic worms). When people drink water contaminated with protozoan’s, they

can multiply inside the body and cause mild to severe diarrhea. Another protozoan,

Endamebahistolytic a, is the cause of amebiosis, also known as amebic dysentery.

Amebiosis used to be a major cause of illness in the U.S. before the days of

widespread water and wastewater treatment. Bloody diarrhea is a major symptom.

Infected people become carriers of protozoans and shed them in feces. The

protozoan’s can form a protective covering (called cysts) and become inactive when

in hostile environments, like water and wastewater. In this stage, they are often

resistant to disinfection and water treatment methods. While outbreaks can be

controlled by boiling water, the best strategy is to prevent pollution by limiting the

amount of untreated wastes released to water sources.

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Parasitic worms can also dwell in untreated sewage. Tapeworms and roundworms

are the most common types found in the U.S. Their eggs are found in untreated

wastewater and can be ingested. Hookworms are still present in the southeastern

U.S. They usually enter through the skin or bare feet. Symptoms from parasitic

worms vary, but can include abdominal pain, weight loss, anemia, and fatigue.

Who is most at risk?

Whether or not someone will get sick after being exposed to untreated wastewater is

hard to predict. There are enough disease causing organisms in wastewater,

however, to make contact with it always very risky.

Many people who are infected with pathogens or pollutants in water never even

develop symptoms. How healthy you are to begin with, whether or not you have built

up a resistance to a specific disease, how the organism or substance enters your

body, how potent or toxic it is, and the size of the dose all contribute to how severely

you will be affected.

People who have suppressed immune systems because of HIV/Aids, chronic disease,

chemotherapy, or other conditions are especially at risk from wastewater-related

diseases. Children, the elderly, and the urban and rural poor are also significantly

more at risk than the general population.

Other Wastewater-related Health Concerns

Because of inadequate wastewater treatment, excessive amounts of the nutrients

nitrogen and phosphorus sometimes invade water sources causing algae blooms.

Algae blooms are dangerous to fish because they use a lot of the oxygen in the water.

They can also have a strong, objectionable smell and can affect the taste of water.

Too much nitrogen in water can also be dangerous for humans. It is the cause of

methemoglobinemia, or blue baby syndrome-a condition that prevents the normal

uptake of oxygen in the blood of young babies. It is also suspected of causing

miscarriages. Excess nutrients in coastal waters may also be related to certain "red

tides," which kill fish and other aquatic life and can cause shellfish poisonings and

certain respiratory illnesses in humans.

Metals, such as cadmium, copper, lead, nickel, and zinc, can also be found in

wastewater. Some of these metals are needed in trace amounts by our bodies, but

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can be harmful in larger doses. Acute poisoning from heavy metals in water is rare in

the U.S., but whether ingesting small amounts over an extended period of time has

any accumulative effects is unknown. Other potentially toxic substances can enter

wastewater from various sources, such as local business, industry, or storm water

runoff. These substances can include pesticides and chemicals like chlorinated

hydrocarbons, phenol, PCBs (polychlorinated biphenyls), and benzene.

Preventing potentially harmful substances from polluting water in the first place is

always the best strategy for protecting health and the environment and preserving

valuable water resources for community use and recreation. Communities can help

through programs that ensure local businesses and industries properly pretreated

and dispose of the wastewater they generate. Communities can also educate and

encourage homeowners to properly dispose of hazardous household chemicals, such

as paints, varnishes, photographic solutions, pesticides, and motor oil. Some

communities set up special dates and locations for collecting these substances.

How Wastewater Treatment Helps Prevent Disease

Wastewater treatment consists of a combination of processes used in steps to

remove, kill, or "inactivate" a large portion of the pollutants and disease-causing

organisms in wastewater.

Most treatment methods include a preliminary step in which the solid materials are

filtered out or allowed to settle and separate from the rest of the wastewater. Helpful

bacteria grow naturally in the solids or "sludge," which provide some initial

treatment for the sludge and the wastewater that comes in contact with it.

The wastewater receives further treatment often through a combination of filtration

and biological and chemical processes. Liquids are often stored for a period of time to

allow further settling and bacterial treatment. The sludge is then treated further by

applying lime or chemicals, air drying, heat drying, or composting. For final disposal,

it is burned, buried in landfills, used as commercial fertilizer, spread on forested land,

or disposed of in the ocean.

Soil can also be used to help treat wastewater. If conditions are right, liquid wastes

can be applied to soil, and most of the pollutants are either removed, inactivated by

bacteria, adhere to certain materials in the soil, or filtered out before reaching the

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groundwater. Sand or other media can sometimes be used in place of soil in areas

where the natural soil or geographical conditions are not suited for this purpose.

Disinfection is normally the final treatment step for wastewater being discharged

from municipal treatment facilities near or directly into surface water or for

groundwater recharge. Chlorine, ozone, ultraviolet light, or other chemical agents

inactivate many pathogens that manage to survive previous treatment processes.

(Wastewater discharge to Indiana waters from individual residential on-site disposal

systems is not permitted.)

However, while wastewater treatment is essential for protecting water quality, it is

only one barrier against disease. Additional treatment is usually needed to ensure

that water is safe to drink.

Community Awareness Is Needed

The potential for outbreaks of wastewater related illnesses in many small

communities across the U.S. is significant, and to protect public health, water and

wastewater treatment projects need to be given priority and community leaders and

residents need to be aware of potential problems.

Rural homeowners need to learn about what is good and bad for their onsite

systems, what maintenance is needed, and how to identify possible problems.

Homeowners with wells need to be informed about well water testing and

preventing contamination.

Communities also need to regularly monitor local water quality. Sometimes illegally

dumped wastes can threaten water and groundwater resources. Strategies are

needed for identifying and solving local pollution problems, and residents,

businesses, and industry need to be educated about the health dangers associated

with untreated wastewater.

Table 4: Variation in Rate of Water Supply and Rate of Sewage Produced with Population Population Rate of Water Supply

(litres/capita/day) Rate of Sewage Produced

(litres/capita/day) Upto 20000 110 90 20000 to 50000 110 to 150 90 to 120 50000 to 200000 150 to 180 120 to 150 200000 to 500000 180 to 210 150 to 170 500000 to 1000000 210 to 240 170 to 190 Above 1000000 240 to 270 190 to 200

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7. Stages of Waste water treatment plant

7.1 Receiving Chamber

Fig.2 Receiving Chamber

7.1.1 Function

Receiving chamber is a chamber which receives wastewater that is generated from

house hold, industries and commercial buildings and after that it further goes to

various units operating of wastewater like screening, grit chamber, etc.

7.1.2 How It Works

Receiving chamber is the structure to receive the raw sewage collected through Under Ground Sewage System. It is a rectangular shape tank constructed at the entrance of the sewage treatment plant. The main sewer pipe is directly connected with this tank.

7.1.3 Operation and Maintenance Considerations

Receiving chamber is the structure to receive the raw sewage collected through Under Ground Sewage System. The main sewer pipe is directly connected with this tank, so we have to avoid the clogging of the main pipe by daily cleaning of receiving chamber.

30

7.1.4 Design Criteria For the design of receiving chamber of the primary sewage treatment plant the influent

volume has been estimated as 4.864 cumec with an assumed detention period of 60 sec

and 4.8m depth .The planned cross-section of the designed chamber. The detention period

for receiving chamber was calculated 60 seconds. The volume of sewage water required at

receiving chamber was estimated 311.81 m3. The ratio of depth and width is taken as 2:1.

The design dimensions of receiving chamber to carry the required volume was calculated

width of the chamber is 5.8 m, length of the chamber 11.20 m and the depth was 4.80 m

with total cross-section area of 60.80 m2 . A free board of 0.5 m was provided for the

safety purpose to avoid the overflow.

7.2 Coarse Bar Screen

7.2.1 Coarse Bar Screen (manual)

Fig.3 Manual Coarse Bar Screen

7.2.1.1. Function

Manual Bar screens were more widely used in the past at the headwork’s of most

wastewater treatment plants. Today you will usually see manual bar screens at older,

smaller (< 4000 m3/day) wastewater treatment plants, pump stations and

mechanically cleaned bar screens at larger WWTP's. Manual bar screens have been

replaced with more robust mechanical bar screens. The shift away from the manual

bar screens can be attributed to the inefficiencies and manual labor requirements.

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7.2.1.2 How It Works

Manual bar screens have little or no motorized cleaning equipment therefore must

be periodically cleaned manually by hand. Not only is maintaining the manual bar

screen lab intensive, but when removal of screenings from the bar screen is

infrequent, flooding and overflow occurs due to clogging. If the bar screen does

become clogged, the head accumulated from hair pinning and solids matting on the

bar screen between cleanings, creates a massive surge when the screenings are

removed.

The high velocity flow produced from the backed up head may compromise solids

capture effectiveness of downstream equipment. When excessive head loss is

anticipated, a bypass channel with a trash rack (bar spacing between 3 to 4 inches)

may be utilized. Sometimes cleaning the bar screen may produce some undesirable

results, as minor as it may be you should be aware. When bar screens are cleaned,

whether manual or mechanical, positively engaging the screen will cause some

screenings to shear, resulting in breakthrough.

7.2.1.3 Operation and Maintenance Considerations

As previously stated, some manual bar screens are major "work horses" at smaller

plants. The manual bar screens that are still being utilized commonly have bar

spacing between 25 mm to 50 mm (or 1 to 2 inches) schedule cleaning as often as

necessary (each situation may be different) to ensure unobstructed flow of the waste

stream. Screenings removed manually from the bar screen are conveyed to a

perforated plate to drain excess water before being disposed of. This may be very

important depending on the method of disposal as it may reduce transportation cost.

For these bar screens, it is important that the bar length not exceed a distance that

can be manually cleaned conveniently, use 3 m (or 10 feet) as a "rule of thumb".

7.2.1.4 Design Criteria

1. Approach velocity of the waste water in the screening channel shall not fall below a

self cleaning velocity of 37.5 cm/sec, or rise to a magnitude at a magnitude in which

screenings will be dislodged from the bars.The suggested approach velocity in the

screening channel is 60 cm/sec to 75 cm/sec, for all the grit bearing waste water. The

32

slope of the floor of the channel may be adjusted to maintain the velocity.The

suggested maximum velocity through the screen is 30 cm/sec at average rate of the

flow for hand cleaned bars screens.

2. Head losses resulting from the screening operation must be controlled so that back

water will not cause the entrant sewer to operate under pressure. Head loss can be

calculated from the following empirical relationship give by Kirschmer:

h= β(w/b)4/3 hυ sinθ

In which,

h=head loss, in m,

β=bar shape factor,

w=width of the bars facing the flow.

b=clear spacing between the bars,

hv=velocity head of flow approaching the rack, in m,

& θ=angle of the rack with the horizontal.

In the above equation β may be taken as 2.42 for sharp edged rectangular bars, 1.83

for rectangular bars with semi-circular upstream face, and 1.79 for circular rods.

Normally head losses in excess of about 8 cm for clogged screens are not tolerated.

3. The slope of the hand cleaned screens should be in between 30° and 45° with the

horizontal

4. The submerged area of the surface of the screen, including bars and opening should

be 200% of the cross-sectional area of the entrant sewer for separate sewers, and

300% for combined sewers. The net submerged area of the opening of the screen

should be about 500 cm2 per MLD of flow for separate sewerage and 750 cm2 for

MLD of flow for combined sewerage system.

7.2.2 Coarse Bar Screen (mechanical)

Fig. 4 Mechanical Coarse Bar Screen

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7.2.2.1 Function

Mechanical bar screens (or mechanical screens) have been used at the headworks of

most medium to large wastewater treatment plants for the past 50+ years.

More recently, mechanical bar screens are appearing in pump stations and combined

sewer systems. In WWTP applications such as these, it is very common to provide

two bar screens. At smaller treatment facilities where is mechanical bar screens are

used, they are usually the duty bar screen while manual bar screens are used as

standby units.


The standby bar screen will be brought online when the mechanical bar screen is

inoperable or down for routine maintenance. At larger treatment facilities there may

be more than two mechanical bar screens, having two or more duty as well as

standby units. Stop logs should be installed to allow each channel to be isolated, so

that the channel can be dewatered and the bar screens maintained.The clear bar

spacing for mechanically cleaned bar screens is usually between 6 mm to 38 mm (or

1/2 to 1 1/2 inches ). The amount of debris removed from the bar screen can be

directly linked to the bar space opening. The bar screen should be positioned at a 45

to 90 degree angle from the horizontal, with 60 degree being the most common

configuration. This will increase the screening surface area, which in turn will

expedite cleaning and eliminate clogging. This configuration will augment screening

surface area up to 100%, it will also facilitate cleaning and eliminate escalating head

from matting on the bar screen.


The mechanical device that cleans the bar screen is activated by a manual start-stop

Switch, a timer, a overload switch, a actuator which sense pressure differential

between points upstream and downstream of the bar screen, and a float that turns on

when head across the bar screen is greater than some predetermined elevation. In

wastewater treatment process combustible gases such as methane are emitted. To

avoid catastrophic failure, all motors and controls are to be explosion proof.

Mechanical bar screens offer several advantages over the trash rack or manual bar

Screen. With mechanical bar screens labor cost from maintenance are usually allot

34

Lowers, screening capture is more efficient, and larger debris are removed with less

hastle. These are a few ways mechanical bar screens show improvement over manual

bar screens. More recent bar screens are using more robust materials such as

Stainless steel to stand up against resist corrosion.


1. Approach velocity of the waste water in the screening channel shall not fall below a self

cleaning velocity of 37.5 cm/sec, or rise to a magnitude at a magnitude in which

screenings will be dislodged from the bars.

2. The suggested maximum velocity through the screen is 75 cm/sec at normal maximum

flow for mechanically cleaned screens.

3. The mechanically cleaned screen, the head loss is specified by the manufacturers.

4. The slope of the mechanically cleaned screens may have a slope between 45° and 80°.

5. Clear spacing of bars may be from 25 to 50 mm for hand cleaned bar screens. This may

range from 15 mm to 75 mm in case of mechanically cleaned bar screens. The width of

the bars facing the flow may be from 8 mm to 15 mm, and the depth may vary from 25

mm to 75 mm; but the sizes less than 15mm × 50 mm are normally not used. They are

welded together at rear face.

Table 5: Usual Bar Sizes and Openings

Dimension of the Bar facing flow, mm

Clear spacing between bars, mm

Area f the opening/ gross surface area of the screens, %

6 18 75 6 24 80 6 30 83.3 6 36 85.6 9 18 66.7 9 24 72.8 9 30 77 9 36 80 12 18 60 12 24 66.7 12 30 71.5 12 36 75

35

7.3 Raw Sewage Lift Pumps

Fig. 5 Raw Sewage Pump

7.3.1 Function

Pumping stations in sewage collection systems, also called lift stations, are normally

designed to handle raw sewage that is fed from underground gravity pipelines (pipes

that are laid at an angle so that a liquid can flow in one direction under gravity).

Sewage is fed into and stored in an underground pit, commonly known as a wet well.

The well is equipped with electrical instrumentation to detect the level of sewage

present. When the sewage level rises to a predetermined point, a pump will be

started to lift the sewage upward through a pressurized pipe system called a sewer

force main or rising main from where the sewage is discharged into a gravity

manhole. From here the cycle starts all over again until the sewage reaches its point

of destination – usually a treatment plant. By this method, pumping stations are used

to move waste to higher elevations. In the case of high sewage flows into the well (for

example during peak flow periods and wet weather) additional pumps will be used.

If this is insufficient, or in the case of failure of the pumping station, a backup in the

sewer system can occur, leading to a sanitary sewer overflow – the discharge of raw

sewage into the environment.

7.3.2 How It Works

Sewage pumping stations are typically designed so that one pump or one set of

pumps will handle normal peak flow conditions. Redundancy is built into the system

so that in the event that any one pump is out of service, the remaining pump or

36

pumps will handle the designed flow. The storage volume of the wet well between

the 'pump on' and 'pump off' settings is designed to minimize pump starts and stops,

but is not so long a retention time as to allow the sewage in the wet well to go septic.

Sewage pumps are almost always end-suction centrifugal pumps with open impellers

and are specially designed with a large open passage so as to avoid clogging with

debris or winding stringy debris onto the impeller. A four pole or six pole AC

induction motor normally drives the pump.

The interior of a sewage pump station is a very dangerous place. Poisonous gases

such as methane and hydrogen sulfide can accumulate in the wet well; an ill-

equipped person entering the well would be overcome by fumes very quickly. Any

entry into the wet well requires the correct confined space entry method for a

hazardous environment. To minimize the need for entry, the facility is normally

designed to allow pumps and other equipment to be removed from outside the wet

well.


The system is mostly computer- or electronically monitored. Sensors check the

sewage level of the wet wells and start/stop the pumps. The pumps and its

monitoring unit should be maintained periodically by the supplier.

7.3.4 Design Criteria

There are certain locations where it is possible to convey sewage by gravity to a central

treatment facility or storm water is conveyed up to disposal point entirely by gravity.

Whereas, in case of large area being served with flat ground, localities at lower elevation

or widely undulating topography it may be essential to employ pumping station for

conveyance of sewage to central treatment plant. Sewage and storm water is required to be

lifted up from a lower level to a higher level at various places in a sewerages system.

Pumping of sewage is also generally required at the sewage treatment plant.

Pumping of sewage is different than water pumping due to polluted nature of the

wastewater containing suspended solids and floating solids, which may clog the pumps.

The dissolved organic and inorganic matter present in the sewage may chemically react

with the pump and pipe material and can cause corrosion. The disease causing bacteria

present in the sewage may pose health hazard to the workers. Sedimentation of organic

37

matter in the sump well may lead to decomposition and spreading of foul odour in the

pumping station, requiring proper design to avoid deposition. Also, variation of sewage

flow with time makes it a challenging task.

Pumping stations are often required for pumping of (1) untreated domestic wastewater, (2)

stormwater runoff, (3) combined domestic wastewater and stormwater runoff, (4) sludge

at a wastewater treatment plant, (5) treated domestic wastewater, and (6) recycling treated

water or mixed liquor at treatment plants. Each pumping application requires specific

design and pump selection considerations. At sewage treatment plant pumping is also

required for removal of grit from grit chamber and pumping may be required for

conveying separated grease and floating solids to disposal facility.

Generally pumping station should contain at least three pumping units of such capacity to

handle the maximum sewage flow if the largest unit is out of service. The pumps should

be selected to provide as uniform a flow as possible to the treatment plant. All pumping

stations should have an alarm system to signal power or pump failure and every effort

should be made to prevent or minimize overflow. Flow measuring device such as

venturimeter shall be provided at the pumping station. In all cases raw-sewage pumps

should be protected by screens or racks unless special devices such as self cutting grinder

pumps are provided. Housing for electric motors should be made above ground and in dry

wells electric motors should be provided protection against flooding. Good ventilation in

dry well should be provided, preferably of forced air type, and accessibility for repairs and

replacements should be ensured.

The site selection for the pumping station is important and the area selected should never

get flooded. The station should be easily accessible in all weathers. The stormwater

pumping station should be so located that the water may be impounded without causing

damage to the properties. Location of the pumping station should be finalize considering

the future expansion and expected increase in the sewage flow. There need to be enough

space in the pumping station to replace low capacity pump with higher capacities as per

the need in future. The capacity of the pumping station is based on the present and future

sewage flow. Generally design period up to 15 years is considered for pumps. The civil

structure and the pipelines shall be adequate to serve for the design period of 30 years.

Types of Pumps Following types of pumps are used in the sewerage system for pumping

of sewage, sewage sludge, grit matter, etc. as per the suitability: a. Radial-flow centrifugal

pumps b. Axial-flow and mixed-flow centrifugal pumps c. Reciprocating pistons or

plunger pumps d. Diaphragm pumps e. Rotary screw pumps f. Pneumatic ejectors g. Air-

lift pumps Other pumps and pumping devices are available, but their use in environmental

engineering is infrequent.

38

Radial-Flow Centrifugal pumps: These pumps consist of two parts: (1) the casing and (2)

the impeller. The impeller of the pump rotates at high speed inside the casing. Sewage is

drawn from the suction pipe into the pump and curved rotating vanes throw it up through

outlet pipe because of centrifugal force. Radial-flow pumps throw the liquid entering the

center of the impeller out into a spiral volute or casing. The impellers of all centrifugal

pumps can be closed, semi open, or open depending on the application.

Open impeller type pumps are more suitable because suspended solids and floating matter

present in the sewage can be easily pumped without clogging. These pumps can have a

horizontal or vertical design. These pumps are commonly used for any capacity and head.

These pumps have low specific speed up to 4200.

Axial- flow Centrifugal pumps: Axial-flow designs can handle large capacities but only

with reduced discharge heads. They are constructed vertically. The vertical pumps have

positive submergence of the impeller. These are used for pumping large sewage flow,

more than 2000 m3/h and head up to 9.0 m. These pumps have relatively high specific

speed of 8000 – 16000. The water enters in this pump axially and the head is developed by

the propelling action of the impeller vanes.

Mixed flow pumps: These pumps develop heads by combination of centrifugal action and

the lift of the impeller vane on the liquid. They are having single impeller. The flow

enters the pump axially and discharges in an axial and radial direction into volute type

casing. The specific speed of the pump varies from 4200 to 9000. These are used for

medium heads ranging from 8-15 m.

Most water and wastewater can be pumped with centrifugal pumps. They should not be

used for the following: 1) Pumping viscous industrial liquids or sludges, where the

efficiencies of centrifugal pumps are very low, and therefore positive displacement pumps

are used for such applications. 2) Low flows against high heads. Except for deep-well

applications, the large number of impellers needed is a disadvantage for the centrifugal

design.

The rotational speed of impeller affects the capacity, efficiency, and extent of cavitation.

Even if the suction lift is within permissible limits, cavitations can be a problem and

should be checked. Centrifugal pumps are classified on the basis of their specific speed

(Ns) at the point of maximum efficiency. The specific speed of the pump is defined as

speed of the impeller in revolution per minute such that it would deliver discharge of 1

m3/min against 1.0 m of head.

The pumps with low specific speed are suitable for more suction lift than the pumps with

high specific speed. The axial flow pumps with high specific speed will not work with

any suction lift; rather these pumps require positive suction head and some minimum

39

submergence for trouble free operation. It is advisable to avoid suction lift for the

centrifugal pumps. Hence pumps are generally installed either to work submerged in the

wet well or installed in the dry well at such a level that the impeller will be below the level

of the liquid in the wet well.

Positive displacement pumps: These pumps include reciprocating piston, plunger, and

diaphragm pumps. Almost all reciprocating pumps used in environmental engineering are

metering or power pumps. A piston or plunger is used in a cylinder, which is driven

forward and backward by a crankshaft connected to an outside driving unit. Adjusting

metering pump flow involves merely changing the length and number of piston strokes. A

diaphragm pump is similar to a reciprocating piston or plunger, but instead of a piston, it

contains a flexible diaphragm that oscillates as the crankshaft rotates. Plunger and

diaphragm pumps feed metered amounts of chemicals (acids or caustics for pH

adjustment) to a water or wastewater stream. These are not suitable for sewage pumping

because solids and rugs present in the sewage may clog them. These pumps have high

initial cost and very low efficiency.

Rotary Screw Pumps: In this type, a motor rotates a vane screw or rubber stator on a shaft

to lift or feed sludge or solid waste material to a higher level or the inlet of another pump.

These are used in the square grit chamber for removal of grit.

Air Pumps: These pumps include pneumatic ejectors and airlifts. In pneumatic ejector

wastewater flows into a receiver pot and an air pressure system then blows the liquid to a

treatment process at a higher elevation. The air system can use plant air (or steam), a

pneumatic pressure tank, or an air compressor. This pumping system has no moving parts

in contact with the waste; thus, no clogging of impeller is involved. Ejectors are normally

maintenance free and operate for longer time. Airlift pumps consist of an updraft tube, an

air line, and an air compressor or blower. Airlifts blow air at the bottom of a submerged

updraft tube. As the air bubbles travel upward, they expand reducing density and pressure

within the tube. Higher flows can be lifted for short distances in this way. Airlifts are used

in wastewater treatment to transfer mixed liquors or slurries from one process to another.

These pumps have very low efficiency and can lift the sewage up to small head.

Efficiencies of Pumps range from 85% for large capacity centrifugals (radial-flow

centrifugals and axial-flow and mixed-flow centrifugals) to below 50% for many smaller

units. For reciprocating pistons or plunger pumps efficiency varies from 30% onward

depending on horsepower and number of cylinders. For diaphragm pumps, efficiency is

about 30%, and for rotary screw type, pneumatic ejectors type and air-lift pumps it is

below 25%.

Materials for Construction of Pumps For pumping of water using radial-flow centrifugals

and axial-flow and mixed-flow centrifugal type pumps normally bronze impellers, bronze

40

or steel bearings, stainless or carbon steel shafts, and cast iron housing is used. For

domestic wastewater pumping using radial-flow centrifugals and axial-flow and mixed-

flow centrifugal type pumps similar material is used except that they are often made from

cast iron or stainless steel impellers. For industrial wastewater and chemical feeders using

radial-flow centrifugal or reciprocating piston or plunger type pumps, a variety of

materials depending on corrosiveness are used. In diaphragm pumps the diaphragm is

usually made of rubber. Rotary screw type, pneumatic ejectors type and air-lift pumps

normally have steel components.

7.4 Stilling Chamber

Fig.6 Stilling Chamber

7.4.1 Function

Sewage is oxygenated and clarified in a tank having an open-bottomed stilling

chamber located above an open-topped chamber. Oxygenated sewage is discharged

into the stilling chamber where its velocity is reduced, with sewage passing from the

stilling chamber into the open-topped chamber being precluded from flowing

horizontally along the tank bottom, and upwardly into the clarified sewage.

7.4.2 How it works

A typical sewage treatment process includes the stage in which the sewage is aerated

and contacted with "activated sludge" containing the necessary aerobic micro-

41

organisms and a subsequent stage in which the treated sewage is allowed to settle

into two layers, one being of clear, treated water, the other containing the activated

sludge. Pure water is run-off from the upper layer. Typically, in the treatment of

municipal sewage, there is also a preliminary settling stage in which coarse solids are

removed before the activated sludge treatment is carried out. Since the sewage is

agitated to help dissolve air therein, the activated sludge and settling stages are

conventionally performed in separate vessels.


If properly designed, engineered and constructed, clarifiers call for very little

attention in terms of operation and maintenance. Indeed, the un-mechanized

(hopper-bottom) settling tanks may be said to be zero- maintenance units. Some

parts of the mechanical rake (such as the motor, gearbox etc.) call for only routine

maintenance. The sacrificial rubber squeegees sweeping the floor of the clarifier

need to be checked and replaced, possibly once in two years.


1. The primary sedimentation tanks are designed using the average dry weather flow.

2. The number of tanks is determined mainly by the limitations of tanks size. Normally

all the treatment plants should have at least two tanks in parallel.

3. The depth of mechanically cleaned tanks should be as shallow as practicable, but with

a minimum of 2.15 m. In addition to this theoretical depth or liquid depth, it should

have a space of about 0.25 m for sludge zone, and 0.3 to 0.45 m as free board.

4. The diameter of the circular tanks may range from3.7 m to 60 m, but the usual range is

from 12 m to 30 m. The diameters of the mechanically cleaned tanks are dictated by

the structural requirements of the trusses which support the scrapers.

5. The rectangular tanks may have a length of 92 m, but usually a length more than 30 m

is not provided. This length includes 1.3 m each for inlet and outlet zones, in addition

to the calculated theoretical length. The width of mechanically cleaned tanks is

dictated partly by the available size of the scrapers; the width may be around 6 m.

6. The floor of the tank should have gentle slopes. It should be around 1% and

8%respectively for circular and rectangular tanks.

7. In rectangular tanks, the minimum slope of side walls of the sludge hoppers shall be

1.7 vertical to 1 horizontal; the hopper floors shall have a maximum dimension of 0.6

m.

42

8. Inlets for both rectangular and circular tanks are to be designed to distribute the flow

equally across the cross-section, or, in all directions. There are several alternatives.

9. The scum removal arrangement also is to be made ahead of the effluent weir on all

primary settling tanks.

7.5 Fine Bar screen

7.5.1 Fine Bar screen (manual)

Fig.7 Manual Fine Bar Screen

7.5.1.1 Function

Screening is carried to out by a manually cleaned bar screen (large in size, in order to

reduce the frequency of screenings collection operations) or, preferably, by an

automatically cleaned bar screen (essential in cases of high flow rates of for water

with a high solids content).


Where coarse screens use bars or rods to remove solids, fine screens employ wire

cloth, wedge wire elements or perforated plates. Fine screens are used to remove

particles that may cause maintenance issues for process equipment and/or

operational problems to the treatment process. Typically in smaller treatment

facilities, fine screens can be used in place of primary clarification.

Fine screen openings typically range from 0.06 to 0.25 inches. The smaller size

openings allow the fine screens to remove 20 to 35 percent of suspended solid and

BOD. Depending on your specific situation, static wedge wire, rotary drum, or step

43

fine screens may be used. Static wedge wire screens are typically used in industrial

wastewater treatment facilities and small municipal plants.


Screening is the first treatment station, both for surface and wastewater. Its purpose

to:

Protect the structure downstream against large objects which could create

obstructions in some of the facility's units,

Easily separate and remove large matter carried along by the raw water,

which might negatively affect the efficiency of later treatment procedures or

make their implementation more difficult.

The efficiency of the screening operation depends of the spacing between screen

bars:

Fine screening, for a spacing under 10 mm

Medium screening, for spacing of 10 to 40 mm

Coarse screening, for spacing of over 40 mm

Usually the fine screening is preceded by a preliminary screening operation for

purposes of protection.

Manually cleaned screens require frequent raking to prevent clogging. Cleaning

frequency depends on the characteristics of the wastewater entering a plant. Some

plants have incorporated screening devices, such as basket-type trash racks, that are

manually hoisted and cleaned.


A bar screen is composed of vertical or inclined bars spaced at equal intervals across the

channel through which sewage flows. It is usual to provide a bar screen with relatively

large openings of 75 to 150 mm ahead of pumps for raw sewage while those proceeding

the primary sedimentation tanks have smaller opening of 50 mm. Hand cleaned racks are

set usually at an angle of 45° to the horizontal ot increase the effective cleaning surface

and also to facilitate the racking operations.

44

Table 6: Design Information For Bar Racks Items Hand Cleaned Mechanically cleaned

Bar size: Width (mm) Depth (mm)

5-15

27-75

5-15

25-75 Clean spacing between

bars (mm) 25-50 15-30

Slope from vertical (deg.) 30-45 0-30 Approach velocity (m/s) 0.3-0.6 0.6-1.0

Allowable head loss (mm) 150 150

7.5.2 Fine Bar screen (mechanical)

Fig.8 Mechanical Fine Bar Screen

7.5.2.1 Function

The automatic bar screen is usually protected by a sturdy preliminary bar screen,

which should also be provided with an automatic cleaning systems in large facilities

and in case of raw water containing a high volume of coarse matter.

To reduce manual operations as much as possible, screening procedures have

become increasingly automated, even in small facilities. Automation is essential in

situations where large amounts of plant matter are carried by the water and arrive

all at once at the bar screen, tending to mat the bars and completely clogging the

screen in a few minutes. Fine screens must be automated.

45


Mechanical cleaning of bar screen is accomplished with the help of mechanically

operated rakes. The mechanically operated rakes may be (a) revolving type (for

curved screening) (b) reciprocating type (for straight vertical or inclined screen )

which move up and down (c) endless revolving type (for straight vertical or inclined

screens) and in each case rake arm teeth are so formed as to mesh with screen. the

rake speed is less than 3m/min. The inclination of the mechanically cleaned bar

screens is between 60-90 degree with the horizontal.


Mechanically cleaned screens usually require less labor for operation than manually

cleaned screens because screenings are raked with a mechanical device rather than

by facility personnel. However, the rake teeth on mechanically cleaned screens must

be routinely inspected because of their susceptibility to breakage and bending. Drive

mechanisms must also be frequently inspected to prevent fouling due to grit and

rags. Grit removed from screens must be disposed of regularly.


Mechanically cleaned coarse screens should precede some type of fine screens.

Newer designs of internally fed rotary screens that use wedge wire instead of screen

fabric are structurally more rugged. These designs can handle coarse solids that are

transported through wastewater pumps; thus upstream protective device may not

require.

An installation should have a minimum of two screens, each with the capacity of

handling peak flow rates. Flushing water should be provided nearby so that the

building of grease and other solids on the screen can be removed periodically. In

colder climates hot water or steam is more effective for grease removal.

The calculation of head loss through fine screen differs from that of coarse screen.

The clear water head loss through fine screen may be obtained from manufactures

rating tables or calculated using below eq.

h = ( ) 2

Where, h = headloss, m

46

C = coefficient of discharge for the screen (a typical value for a clean

screen is 0.06)

g = acceleration due to gravity, 9.81 m/s2

Q = discharge through screen, m3

A = effective open area of submerged screen, m2

Values of C and A depend on screen factors, such as the size and milling of slots, the

wire diameter and weave, and particularly the percent of open area, and must be

obtained from the screen manufacture or determine experimentally. The important

determination is the head-loss during operation; head-loss depends on the size and

amount of solids in the wastewater, the size of the aperture and the method and

frequency of cleaning.

7.6 Grit Chamber

Fig.9 Grit Chamber

7.6.1 Function

Wastewater usually contains a relatively large amount of inorganic solids such as

sand, cinders and gravel which are collectively called grit. The amount present in a

particular wastewater depends primarily on whether the collecting sewer system is

of the sanitary or combined type. Grit will damage pumps by abrasion and cause

serious operation difficulties in sedimentation tanks and sludge digesters by

accumulation around and plugging of outlets and pump suctions. Consequently, it is

common practice to remove this material by grit chambers. Grit chambers are

usually located ahead of pumps or comminuting devices, and if mechanically cleaned,

should be preceded by coarse bar rack screens.

47

7.6.2 How it works

Grit chambers are generally designed as long channels. In these channels the velocity

is reduced sufficiently to deposit heavy inorganic solids but to retain organic material

in suspension. Channel type chambers should be designed to provide controlled

velocities as close as possible to 1.0 foot per second. Velocities substantially greater

than 1.0 foot per second cause excessive organic materials to settle out with the grit.

The detention period is usually between 20 seconds to 1.0 minute. This is attained

by providing several chambers to accommodate variation in flow or by proportional

weirs at the end of the chamber or other flow control devices which permit

regulation of flow velocity.


Manually cleaned grit chambers for combined wastewater should be cleaned after

every large storm. Under ordinary conditions these grit chambers should be cleaned

when the deposited grit has filled 50 to 60 percent of the grit storage space. This

should be checked at least every ten days during dry weather.

When mechanically cleaned grit chambers are used, they must be cleaned at regular

intervals to prevent undue load on the cleaning mechanism. Recommendations of

the manufacturer should be rigidly observed. This plus experience, will determine

the cleaning schedule.

A grit in which marked odors develop indicates that excessive organic matter is being

removed in the grit chamber. Alternately, if sludge from a settling tank is excessively

high in grit, or if there is excessive wear in pumps, comminutors, sludge collectors or

other mechanical equipment, the reason is likely to be inefficient functioning of the

grit removing process. In either case, a study of this unit should be made.


The design of the horizontal-flow grit chambers should be such that under the most

adverse conditions, all the grit particles of size 0.2 mm or more in diameter will reach the

bed of the channel prior to their reaching the outlet end.

The length of the channel will be gravened by the depth required which is again governed

by the settling velocity. A minimum allowance of approximately twice the maximum

48

depth should be given for inlet and outlet zones. An allowance of 20% - 50% of the

theoretical length of the channel may also be given.

A value within between 1 m and 1.5 m may be assumed. The depth of flow is normally

kept shallow. For total depth of the channel, a free board of about 0.3 m and grit space of

about 0.25 m should be provided.

For larger plants two or more number of grit chambers in parallel may be provided.

Detention time 30 to 60 seconds are recommended in the grit chamber.

7.7 Sequencing Batch Reactor (SBR) Basins

Fig.10 SBR Basin

7.7.1 Function

SBR facilities commonly consist of two or more basins that operate in parallel but

single- basin configurations under continuous-flow conditions. In this modified

version of the SBR, flow enters each basin on a continuous basis.

7.7.2 How it works

The influent flows into the influent chamber, which has inlets to the react basin at the

bottom of the tank to control the entrance speed so as not to agitate the settled

solids. Continuous-flow systems are not true batch reactions because influent is

constantly entering the basin. The design configurations of SBR and continuous-flow

systems are otherwise very similar. Plants operating under continuous flow should

operate this way as a standard mode of operation. Ideally, a true batch-reaction SBR

should operate under continuous flow only under emergency situations. Plants that

have been designed as continuous-inflow systems have been shown to have poor

operational conditions during peak flows. Some of the major problems of continuous-

49

inflow systems have been overflows, washouts, poor effluent, and permit violations.


Communities that have combined collection systems or that are subject to sanitary-

sewer overflows during wet weather should consider developing wet-weather

operating plans or standard operating procedures (SOPs). A wet-weather operating

plan or SOP also benefits facilities subject to process upset during wet-weather

periods. This plan provides operators with a guide to minimize the discharge of

pollutants during wet weather and protect their facility from upset.


a.

(1) The design of a sequencing batch reactor (SBR) involves the same factors

commonly used for the flow-through activated sludge system. The aspects of a

municipally treated waste which require de-ntrification as well as nitrification plus

biological phosphorous removal need additional design considerations. Pretreatment

of the wastewater before influent in the SBR reactor system is also required.

(2) The following example should be considered an outline to identify reactor

volume elements, a diffused aeration system, the basis for signing effluent decanter

units, and waste sludge systems for a system receiving 378,500 L/d (100,000 gal/d)

of wastewater.

(3) Food-to-mass (F/M) ratio typically ranges from 0.05 to 0.30 with domestic waste

F/M ratios typically ranging from 0.10 to 0.15. At the end of the decant phase, the

MLSS concentration may vary between 2,000 and 5,000 mg/L. A typical value for a

municipal waste would be 3500 mg/L. The MLSS concentration changes

continuously throughout an SBR operating cycle from a maximum at the beginning of

a fill phase to a minimum at the end of the react phase.

b. Reactor volume

Calculate the reactor volume based on the desired BOD removal, the F/M ratio, and

the MLSS.

50

c. Decant volume

Calculate the decant volume as the difference between the reactor volume and the

low water volume, as shown in Table E-10. Each operating cycle is normally

composed of mixed fill, react fill, settle, decant, sludge waste, and idle. The number of

cycles dictates the number of decants per day or the volume of liquid to be decanted

for each cycle. The volume per decant per cycle must be selected based on the

maximum sustained daily flow.

d. Detention time

Calculate the maximum detention time based on the reactor volume. Calculate the

minimum detention time based on the decant volume, as shown in Table E-10.

e. SBR dimensions

Estimate the required unit process dimensions, as shown in Table E-10. The basin

length can be estimated based on a recommended minimum depth. The minimum

depth after decant is determined as the depth of a clarifier in a flow-through system,

i.e., quiescent settling and a large settling area. A minimum depth of 2.75 m (9 ft) is

typically recommended by designers.

7.8 Chlorination Tank

Fig.11 Chlorination Tank

51

7.8.1 Function

Chlorination of wastewater is the application of chlorine to a wastewater to

accomplish some definite purpose. The purpose of chlorination may not always be

disinfection and may, in fact, involve odor control or some other objective which will

be noted. Chlorine may be applied in two general ways, gaseous and liquid. In

general, the effective chemical form of chlorine that either destroys the microbe or

acts against odor, etc., is the same. Gaseous forms of chlorine are generally first

dissolved in water prior to addition to the wastewater stream, while liquid forms of

chlorine (called hypochlorite) are sold in the form of water soluble salts. Because

chlorine gas generally costs less than hypochlorite’s, it is normally used in treatment

plants except in rare instances where only a relatively small amount of chlorine is

needed or where the possible danger from gaseous chlorine overrides economic

considerations. The application of chlorine is usually controlled by special devices

which are known as chlorinators, chlorinizers or by similar names.

7.8.2 How It Works

Disinfection of urban waste water is the destruction of disease bearing micro-

organisms or pathogens. It is distinct from sterilization which involves the complete

destruction of all organisms in the liquid being treated. Disinfection has not been

extensively practiced in Europe to date; in the USA a large proportion of discharges

are disinfected using chlorine. However, in order to comply with EU directives such

as:

• The shellfish directive (79/923/EEC), as implemented by S.I. 200 of 1994, and

• The bathing water directive (76/160/EEC), as implemented by S.I. 155 of

1992 and S.I. 230 of 1996,

Sanitary authorities may in future have to consider the use of disinfection. Activated

sludge and biofilm systems will disinfect the waste water to some degree but few

achieve greater than 90% -removal of pathogenic micro-organisms. For complete

disinfection, further treatment is necessary. The pathogenic micro-organisms to be

removed include faecal coliforms and streptococci, salmonella and enteric viruses.

52

The main techniques for the disinfection of urban waste water fall into three main

categories:

Chemical;

Physical; and

Irradiation.

Chemical disinfectants include chlorine, ozone and hydrogen peroxide. The factors

influencing the performance of chemical disinfectants are the contact time, the

efficiency of mixing, the type and concentration of chemicals used, the residual

remaining, the pH and the concentration of interfering substances which may reduce

the effectiveness of the disinfectant.

The principal physical methods rely on enhanced removal of solids and membrane

technologies. Ultra-violet (UV) light is the principal method of irradiation used.


Chlorine is widely used in drinking water treatment for the disinfection of surface

and groundwater. It is a strong oxidizing agent and reacts with any organic matter

present in the water. As a result of the large concentrations of organic matter in

waste waters, higher doses are required (than in drinking water treatment) in order

to achieve similar levels of disinfection. Chlorine may be applied in a number of

forms such as chlorine gas, sodium hypochlorite or chlorine dioxide. On contact with

water, elemental chlorine is hydrolyzed and ionizes to hypochlorite acid (HOCI) and

the hypochlorite ion (OCI). HOCI is by far the more potent disinfectant, therefore the

lower the pH, the more effective is the process. Chlorine will also react rapidly with

ammonia in the waste water to produce a series of chloramines in solution as

follows:

NH3 + HOd - NH2CI+H2O

(monochloramine) NH2C1 + HOC1 - NHC12 + H2O

(dichioramine) NHCI2 + HOC1 - Nd3 + H20 (nitrogen trichloride)

Monochloramine and dichloramine are the dominant species and are less potent

disinfectants than hypochlorous acid. Gray (1989) quotes dosing rates ranging from

2 to 15 mg C12/1, depending on how much treatment the waste water has received

(that is, on how much organic matter is remaining), and contact times of 20-30

minutes.

Chlorination of treated urban waste water can result in the production of toxic

compounds including trichloromethanes and chloramines that can have long term

53

adverse effects on the beneficial uses of the waters to which they are discharged.

Dechlorination of discharges is possible but cost comparisons will be required due to

additional process equipment and their associated costs.


1. Rapid initial mixing of the chlorine solution and waste water should be accomplished

within three seconds and prior to entering the contact chamber.

2 .The hydraulic jumps are considered the best method of obtaining rapid mixing in an

open channel.

3. Mechanical mixers are considered second best in accomplishing rapid mixing. The

mixer should be located at or immediately downstream from the point of chlorine injection

and the mixing chamber should be as small as possible.

4. Injecting the chlorine solution into a full flowing pipe is probably the least efficient.

When this method is used, the inner surface of the pipe shall be irregular so as to create a

sufficient turbulence to accomplished complete mixing within a distance of 10 pipe

diameters. This method will not be acceptable for pipe diameters of 76.2 cm (30 inches)

and larger.

7.9 Sludge Sump

Fig.12 Sludge Sump

7.9.1 Function

Stirring and scraping mechanisms are installed in sludge thickener tanks to reduce

the water content of sledges’ and to continuously remove the still fluid and pumpable

sludge to the central sludge sump.

54

7.9.2 How It Works

The raw, mixed or digested sludge is fed through a central influent cylinder mounted

to the thickener mechanism into the thickener tank.

The thickening process is intensified with the application of vertically mounted

stirring members. By means of an echelon type scraper blade assembly the thickened

sludge on the tank bottom is removed to a center hopper from where it is drawn off

by hydrostatic pressure or pumped off to further treatment facilities


Daily discharges made from property into a sludge tank will affect the efficiency of

system. Discharges of disinfectants and storage chemicals will kill bacteria in the

tank and hence prevent the decomposition of the solids. It is therefore necessaries to

consider certain points.

(a) Discharges of rain water to the sludge are not recommended because it causes

considerable dilution of the bacterial matter thereby reducing the efficiency of

tank.

Periodically the sludge will build-up to such and extend that it need removing.

Frequency of sludge removable is dependent on the use, size and type of sludge tank.

As general guide older bricks or concrete structure will require emptying

approximately once every two years, will fiber glass tanks will need emptying at least

every 12 months. Traditional sludge tank contains no mechanical parts and should

not required any other regular maintenance unless problems occur.


The rate of return sludge flow, Qr depends on the volatile suspended solids concentration

in the secondary settling tank underflow, Xr, and the mixed liquor volatile suspended

solids (MLVSS), X, and is given by the following equation:

(Q + Qr ) X = Qr x Xr

The oxygen requirement of the system can be estimated using the equation:

O2 requirement/day =Ultimate BOD removed/day – 1.42 (Excess sludge wasted per day)

Wt. of O2 required per day = (ultimate BOD consumed/day) - 1.42 (production of

VSS/day)

55

The actual quantity of air to be supplied is estimated considering the fraction of oxygen in

air, and the oxygen transer efficiency of the aerators.

(wt. ofoxygenrequired)(sp. wt. ofairatstandardtemp. )X(fractionofoxygeninair, bywt. )

The specific weight of air, at Mean Sea Level, is 1.2 kg/m3 at 20°c, 1.16 kg/m3 at 30°c.

The fraction of oxygen in air is 23.2%.

Now, the volume of actual air requiremen

(theoreticalrequirement)(oxygentransferef iciency)

For porous tube diffusers, used in conventional activated sludge units, oxygen transfer

efficiency may be assumed as 8%. The oxygen transfer efficiency for coarse bubble

diffusers is around 6%.

General requirements

1. More than one tank is to be provided, if total tank volume exceeds 150 m3.

2. Normally liquid depth should be between 3 m and 4.3 m; a free board of 0.3-0.6 m is

also to be provided.

3. Width to depth ratio may vary from to 1 to 1 to 2.2

4. Length may go upto 150 m. In diffused air aeration conventional system the length is

dictated by the air flow requirement to some extent.

5. A minimum air flow of approximately 0.3 m3/min/metre length of tank is required for

adequate mixing velocities and to avoid deposition of solids. (porous diffuser tubes

can deliver a volume of air of 0.114-0.425m3/min/unit).

6. Air supplied should not be less than 62.50 m3/kg of BOD removed.

56

Table 7: Design Specifications for Activated Sludge Process Systems

Parameters Conventional ASP Complete Mix ASP Y,

0.5-0.67 0.5-0.67

kd,day-1 0.056-0.01 0.055-0.07

Θc, days 5-15 5-15

U,

perday

0.2-0.4 0.2-0.6

Volumetric loading, kg BOD5 /1000m3

320-640 800-1925

MLSS,mg/l (MlVSS=80% of MLSS)

1500-3000 3000

Hydraulic retention time, t, hr

4-8(higher value for lower rate of flow)

3-5

Recirculation ration 0.25-0.5 0.25-1

57

8. Calculations and Results

8.1 Introduction

This project include designing of waste water treatment plant for residential community with a population of (185,545 person), and with a design periods of (30 years).

Geometrical Increase Method

Pn=P0(ퟏ + 풓ퟏퟎퟎ

) n Pn= population in year 2044 P0 = present population is 1, 85,545 (design area population year 2014) r = 30% assume (year 2014 to 2044) n = number of decades (3) Pn=185545(ퟏ + ퟑퟎ

ퟏퟎퟎ)3

Therefore according to mathematical calculation

Pn= 451906 person

Table 8 : Different location and their sewage collected

Sr. No. Location of Tank

Area for water supply Covered Population 2014 (person)

Population 2044 (person)

1 Maktampur filter plant

PritamSociet, Dipali Society, Avadhat Nagar, Gayatrinangr Kask, rachana Nagar etc.

47048 103364

2 Station Tank

Dhokikooi, Dandia Bazar, falshrutinagar,gheekudi, station Road, chingaspura andsoci, etc

14543 31950

3 Soneri Mahal Tank

Hajikha Bazar, Bahadur Buras, ChaklaSoneriMahal, Adus Road, Vhorvad, panchBatti, Ali etc.

19199 42180

4 Towar Tank PhataTalav, dabhoiVad, OcudaFaliya,Peerkanthi, Furja, Bazar etc.

44334 97401

5 Vejalpur Tank

VejalpurNayanachowak, Alisjin Kali,Talawadi etc.

23635 51926

6 Gujarat housing Board Tank

Ssiddhnath Nagar, Gita park, Anank Nagar, Narayan Nagar, Yogeshwar Nagar, G.H.B is all schemes

36786 80818

7 Dungri 20149 44267

Bharuch 185545 451906

58

620*0.75 = 465 ℓ/c.day Average flow = (465 X 451906) / 1000

= 213484.29 m3/day

= 2.432 m3/sec

Calculate the ratio of the maximum sewage flow to the average (M)

M = 1+

√

= 1 +

√

= 1.42

Say M = 2 Max. flow = M * average flow

= 2 * 2.432

= 4.864 m3/sec

59

8.2 Design Calculation of Receiving Chamber

DESIGN:

• Design flow = 4.864 cumec

• Detention time = 60 sec

• Volume required = flow X detention time

• = 4.864 x 60

• Vrqd = 291.84 m3

• Provide, depth = 4.8 m

• Area = 60.80 m2 because( . .

)

• Length: Breadth = 2:1

• L x B = 2B x B =2B2 = 60.80

• B = 5.51 m ≅ 5.80 m

• L = 11.03 m ≅ 11.20 m

Provide: 11.20 m X 5.80 m X 4.80 m = 311.81 m3

Check

Volume designed = 11.20 m X 5.80 m X 4.80 m Vdes= 311.81 m3 Vrqd= 291.84 m3 Vdes > Vrqd

Receiving chamber is designed for the size of 11.20 m X 5.80 m X 4.80 m + 0.5 (FB)

60

8.3 Design Calculation of Coarse bar Screen

8.3.1 Coarse Bar Screen (Manual)

Design Criteria Used

a. Velocity through rack at max flow = 0.6m/sec b. Bar spacing (clear) = 3.0 cm c. Provide two identical barracks, each capable of handling max flow Conditions

and each equipped with mechanical cleaning device, θ = 50˚ d. One screen champers could be taken out of service for routine maintenance

without interrupting the normal planet operation. e. Max. flow = 4.864 m3/sec

Average flow = 2.432 m3/sec

Design of Rack (Screen) Chamber

a. Assume that the depth of the flow in Rack Chamber = 1.00 mt b. Clear area through the Rack = Qave / velocity through rack chamber

=

..

= 3.90 mt

c. Clear width of the opening = Area / Depth of flow

= ..

= 3.90mt

d. Assume the width of each Bar = 0.5 cm And the Clear space = 3.0 cm

e. No. of spacing =

= 130 space

f. Provide bars with 5 mm width

g. Width of chamber = 3.90 +

= 4.55 mt

h. Calculate the efficiency =

= 0.86

61

Head Loss Calculation

The head loss through the bar rack is calculated from equation (1) and (2).

Equation (1) is used to calculate head loss through clean screen only, while

equation (2) is used to calculate head loss through clean or partly clogged bars.

hL = β ( ) / X hr Sin Ɵ ....(1)

hL = (1/0.7) . ... (2)

Where: hL = Head loss through the rack , m

Vv = Velocity through the rack and in the channel upstream of the rack, m /s ( = 0.4 m/sec )

g = Acceleration due to gravity, 9.81 m/s2 w = Maximum width of the bar= 5 mm b = Minimum clear spacing of bars = 30 mm h r = Velocity head of the flow approaching the bars

=

θ = Angle of bars with horizontal. β = Bar shape factor = 1.79

a. Case 1 : When the screen is clean:

hL = β ( ) / X hr Sin Ɵ

hL = 1.79 ( ) / X 0.008 Sin50̊

hL = 0.0031 mt

b. Case 2 : When the screen is partly or completely clogged bars:

hL= X .

hL= . .( . ) X .

62

hL= 0.05mt

8.3.2 Coarse Bar Screen (Mechanical)

Design Criteria Used

a. Velocity through rack at max flow = 0.9m/sec b. Bar spacing (clear) = 2.5cm c. Provide two identical barracks, each capable of handling max flow Conditions

and each equipped with mechanical cleaning device, θ = 75˚ d. One screen champers could be taken out of service for routine maintenance

without interrupting the normal planet operation. e. Max. flow = 4.864 m3/sec

Average flow = 2.432 m3/sec

Design of Rack (Screen) Chamber

a. Assume that the depth of the flow in Rack Chamber = 1.18 mt b. Clear area through the Rack = Qave / velocity through rack chamber

=

..

= 2.70 mt c. Clear width of the opening = Area / Depth of flow

= .

.

= 2.29 mt

d. Assume the width of each Bar = 1 cm

And the Clear space = 2.5 cm

e. No. of spacing =

= 92 space

f. Provide bars with 10 mm width

g. Width of chamber = 2.29 +

= 3.21 mt

h. Calculate the efficiency = = 0.72

63

Head Loss Calculation

The head loss through the bar rack is calculated from equation (1) and (2). Equation (1) is used to calculate head loss through clean screen only, while equation (2) is used to calculate head loss through clean or partly clogged bars.

hL = β ( ) / X hr Sin Ɵ ....(1)

hL = (1/0.7) . ...(2)

Where: hL = Head loss through the rack , m

Vv = Velocity through the rack and in the channel upstream of the rack , m /s ( = 0.5 m/sec )

h = Acceleration due to gravity, 9.81 m/s2 x = Maximum width of the bar= 10 mm c = Minimum clear spacing of bars = 100 mm i r = Velocity head of the flow approaching the bars

=

θ = Angle of bars with horizontal. β = Bar shape factor = 2.42

c. Case 1 : When the screen is clean:

hL = β ( ) / X hr Sin Ɵ

hL = 2.42 ( ) / X 0.025 Sin75̊

hL = 0.0027 mt

d. Case 2 : When the screen is partly or completely clogged bars:

hL= X .

hL= . .( . ) X .

hL= 0.05mt

64

8.4 Raw Sewage Lift Pump Calculation

Estimation of sewage flow considering sewage generation equal to 80% of the water

supply

Average sewage flow = 0.54 m3/s

Peak sewage flow, considering peak factor of 3 = 3 X 0.54 m3s/s = 1.62 cumec

Considering velocity of 1 m/s in rising main, diameter required

D= . = 1.436 m ≅ 1.44 m 퐷

Provide diameter of 1.44m, hence actual velocity = 0.991 m/s ≅ 1 m/s

Design of sump well

Design the sump for minimum time of 15 min for any pump to run continuously.

Quantity of sewage = 1.62 * 60 * 15 = 145.8 m3

Quantity of sewage in rising main = (πD2)*L/4 = .

= 162.86 m3/s

Net storage capacity of the sump = 145.8 + 162.86 = 308.66 m3

Provide 3 sump units, two for storage of sewage and one as standby, with effective water

Depth of 3.0 m. Hence the surface area of each sump = 308.66/(2 * 3) = 51.43 m2

Provide circular or rectangular shaped three sump wells each having surface area of

51.43 m2 and depth of 3.0 m.

Design of Pump

Capacity of each pump = 51.43 / (15 x 60) = 0.057 cumecs.

Frictional loss of Head in the rising main = = .

. . = 0.14 m

Assuming the loss in bends = 0.3

0.3 + 0.14 = 0.44

Total lift against the pump has to work

0.44 + 15 = 15.44 m

H.P of pump

= = . . = 11.73 ≅ 12 H.P.

Assuming the pump efficiency to be 60%, Brake Horse power of Motor required

= 12/0.6 = 20

65

8.5 Stilling Chamber

8.5.1 Design Criteria used

a. Six rectangular units shall be designed for independent operation .A bypass to the

aeration basin shall be provide for emergency conditions when one unit is out of

service .Most regulatory agencies will allow such bypass.

b. Overflow rate and detention time shall be based on an average design flow of

2.432 m3/sec

c. The overflow rate shall be less than 36 m3 /m2. day (at average design flow). d. The detention time shall be not less than 1.5 h. e. All side streams shall be returned to aeration tanks.

f. The weir loading shall be less than 186 m3/m.d at average flow. g. The liquid depth in the basin shall be no less than 2m

h. In flute BOD5, and TSS, to the plant = 250 mg/ℓ, 260 mg/ℓ respectively. 8.5.2 Design Calculations: a. Basin Geometry:

Average design flow through each basin

= 2.432/6 = 0.41 m3/sec

Overflow rate at average flow = 36 m3/m2.day

Surface area = 0.41m3 / sec*86400sec/ day

36m3 / m2.day

= 972.8 m2

Use length to width ratio (4:1) → A = 4W2

Wide of each basin =15.59m

Length of each basin =4*15.59 =62.38 m

Provide average water depth at mid. length of the tank. = 3.2 m

Provide Freeboard

=0.6m Average depth of the basin

= 3.2+0.6 = 3.8 m

66

b. Check Overflow Rate

0.41m3 / s *86400sec/ day

Overflow rate at = 15.59*62.38

Average design flow = 36.42 m3/m2.d

67

Overage rate at max. design flow = 0.536m3 / sec*86400sec/ day 15.59 X 62.38 = 47.62 m3/m2d

c. Detention Time

Average volume of the basin

= 3.2* 15.59*62.38 = 3112m3

Detention time of = 3112m2

0.41m3 / sec*3600s / h Average design flow

= 2.10 hr

Detention time at =

3112m3 0.536m3 / sec*3600s / h

max design flow = 1.61 hr

68

8.6 Fine Bar Screen 8.6.1 Fine Bar Screen (Manual) A bar screen is composed of vertical or inclined bars spaced at equal intervals across

the channel through which sewage flows. It is usual to provide a bar screen with

relatively large openings of 75 to 150 mm ahead of pumps for raw sewage while those

proceeding the primary sedimentation tanks have smaller opening of 50 mm. Hand

cleaned racks are set usually at an angle of 45° to the horizontal ot increase the effective

cleaning surface and also to facilitate the racking operations.

8.6.2 Fine bar Screen (Mechanical) Mechanically cleaned coarse screens should precede some type of fine screens. Newer

designs of internally fed rotary screens that use wedge wire instead of screen fabric are

structurally more rugged. These designs can handle coarse solids that are transported

through wastewater pumps; thus upstream protective device may not require.

The calculation of head loss through fine screen differs from that of coarse screen. The

clear water head loss through fine screen may be obtained from manufactures rating

tables or calculated using below eq.

ℎ = ( ) 2

Where,

h = headloss, m

C = coefficient of discharge for the screen (a typical value for a clean screen 0.60)

g = acceleration due to gravity, 9.81 m/s2

Q = discharge through screen, m3 (drum screen)

A = effective open area of submerged screen, m2

Now,

ℎ = ( ) 2

ℎ = . ( . . .

)2 = 0.05 m

69

8.7 Grit Chamber 8.7.1 Geometry Provide three identical grit chambers for independent operation. Maximum design flow through each chamber

= (4.864m3/sec)/3 = 1.62 m3/sec

Volume of each chamber for 4-min detention period

= 1.62 m3/s * 4 min * 60 sec/min = 389 m3

Provide average water depth at mid width

= 3.8 m

provide freeboard = 0.8 m

Total depth of grit chamber

= 3.8+0.8=4.6 m

Surface area of chamber = 389 m3 /3.8m = 103 m2

provide length to width ratio

= 4:1 ⇒ area = 4w2 Width of the chamber

= 5.1 m Length of the chamber

= 20.4 m

8.7.2 Select Diffuser Arrangement: Locate diffusers along the length of the chamber on one side and place them 0.6 m

above the bottom. The upward draft of the air will create a spiral roll action of the liquid

in the chamber. The chamber bottom is sloped toward a collection channel located on

the same side as the air diffusers. A screw conveyor is provided to move the girt along

the channel length to a hopper at the downstream end. 8.7.3 Design the Air Supply System: Provide air supply at a rate of 7.8 ℓ/s per meter length of the chamber. Theoretical air required per chamber.

= 7.8 ℓ /s.m X 20.4 m = 159.12 ℓ/s

Provide 150 percent capacity for peaking purpose. Total capacity of the diffusers

= 1.5 X 159.12 = 238.68 ℓ/s per chamber

70

8.8 Sequencing Batch Reactor (SBR) The design of a Sequencing Batch Reactor (SBR) involves the same factors commonly

used for the flow through activated sludge system. The aspects of a Municipality treated

waste which requires denitrification as well as nitrification plus biological phosphorus

removal need additional design considerations. Pre treatment of the waste water before

influent in the SBR reactor system is also.

Design Calculations a. Reactor Volume

BOD5 removed (kg/d)= [(BODinfluent – BODeffluent ) (mg/L)] x Flow(l/d) 10-6 (kg/mg) (Considering flow (l/d) =140 l/d) BOD5 removed = (250-25) x 140 x 10-3 =31.5 kg/day Required aerobim mass(kg) = ( / )

( )

Assume F/M ratio = 0.13 Required arobic mass = 31.5/0.13 =242.30 kg MLSS Rector volume(low water level) (m3)= ( )

( / ) x ( / )

( )

(Assume concentration 3500 mg/l)

71

= (242.30/ 3500) x 103 = 69.22 Since the decant volume represents 60% of the total volume, Total rector volume = 69.22/ (1-0.6) = 173.07 m3

b. Decant volume Total decant volume = Total rector volume (m3)- Rector volume (low water level) (m3) = 173.07 – 69.22 = 103.85 m3

c. Detention time

Maximum detention time (hr) = ( ) ( / ) ( / )

x 24(hr /d ) = (173.07 x 24)/((140 x 103 ) x 10-3 ) = 29.66 hr Minimum detention time = = ( )

( / ) ( / ) x 24(hr /d )

= (103.85 x 24) / ((140 x 103) x 10-3) = 17.80 hr

d. SBR dimension Basin area (m2) = ( )

( )

( Assume minimum depth = 2.75 m ) = 69.22/ 2.75 = 21.17 m2 Basin length = √21.17 = 5.01 m Basin depth = ( )

( )

= 173.07/ (5.01)2 = 6.922 m

e. Aeration power ( data assume by assumption table ) Nitrogenous O2 demand (kg. O2 / d) – NH3 - Noxidzed (kg/d) x Kg O2/ kg BOD5 NH3 - Noxidzed (kg/d) – TKN removed (kg/d) – synthesis N (kg/d) TKN removed = (40-5) x 140 x 10-3 = 4.9 kg/d Synthesis N = 5% waste activated sludge of total daily sludge production Sludge production (kg/d) = net sludge yield (kgMLSS / kg BOD5 ) x BOD5 removed ( kg/d ) (Assume net sludge yield = 0.76)

72

= 0.76 x 31.5 = 23.94 kg/d

Synthesis N = 0.05 x 23.94 = 1.197 kg/ d NH3 – Noxized = 4.9 – 1.197 = 3.703 kg/ d (assume kg O2 / kg NH3 - Noxidized = 4.6 ) Nitrogenous O2 demand = 3.703 x 4.6 = 17.03 kg O2 /d Carbonaceous O2 demand ( kgO2 / d ) = BOD mass (kg/d) x(kg O2/ kg BOD5) = 1.197 x 1.28 = 1.53 kgO2/d AOR (kgO2/d) = carbonaceous O2 demand (kgO2 / d) + Nitrogenous O2 demand ( kgO2/d) = 1.53 + 17 .03 = 18.56 kgO2 / d Where AOR = actual oxygen requirement SAOR ( kgO2 / hr ) = Ɵ( )

α (β – ) ( / )

= . . . ( )

. ( . . ) = 2.23 kgO2/ hr

Where, SAOR = standard actual oxygen requirements Ɵ( temperature correction factor) = 1.024 Cs ( O2 saturation concentration at slandered temp. and pressure) = 9.02 mg/ L Csw = concentration correction for elevation (1000 ft) = 9.02 – 0.0003 x elevation = 9.02 – 0.0003 x 1000 = 8.72 mg/L Co = 2 mg/L α = 0.85 ; β = 0.95 ; T = 20 ̊ C blower uses = 14 hr/d ( based on 4 cycles per day ( 6 hr/cycle ) , 1.0 hr fill time , 3.5 hr react time , 0.75 hr settle time , 0.5 hr decant time , and 0.25 hr idle time ) motor requirements ( kW ) = ( / )

( / )

= 2.23/ 1.25 = 1.784 kW Since blowers typically have an efficiency of 50% or less, select 2 aerators with 11.2 kW ( 15 hp) motors . Blower size depends on the standard air flow rate. Blowers: rotary positive displacement.

Diffuser : 4-10 tube coarse bubble retriever diffuser assembly ( 2 per basin)

Mixer : 2 at 3.73 kW (5 hp)

Sludge pupms :2 at 1.49 kW (2hp)

73

Decanter sizing : cycle per day = 4

Volume per decant = 70.5 m3

Decant time = 30 min .

Decant flow rate = 2.35 m3 / min

Influent valves: 2,each 150 mm dia.

Air blower valves: 2,each 150 mm dia.

74

8.9 Chlorination Tank 8.9.1 General Chlorine is used in various ways for odor control. Dechlorination of chlorinated effluent

should be provided when water quality requirements dictate the need. Capability to

add dechlorination systems should be considered in all new treatment plants that will

use chlorine for disinfection. The design of all disinfection facilities utilizing chlorine as

the disinfectant agent should ensure that the dechlorination requirements are met.

Two problems are associated with chlorination as disinfection: effluent toxicity

(chlorine residual) and safety. A dechlorination facility would address the toxicity issue

and containment and scrubbing facility would address the safety issue. The

dechlorination and containment and scrubbing facilities increase the cost of chlorine-

based disinfection.

8.9.1.1 Forms of Chlorine Dry chlorine is defined as elemental chlorine existing in the liquid or gaseous phase,

containing less than 150 mg/L water. Unless otherwise stated, the word “chlorine”

wherever used in this section refers to dry chlorine.

8.9.1.2 Chlorine Feed Equipment Chlorinators are used to convert the gaseous chlorine from a positive pressure to a

vacuum and to regulate or meter the flow rate of the gas. The principal components of a

conventional chlorinator are as follows:

• Inlet chlorine pressure-reducing valve.

• Indicating meter such as a rotameter.

• Chlorine metering orifice, changeable for various ranges of flow.

• Manual feed rate adjuster.

• Vacuum differential-regulating valve.

A few other variations also exist, such as sonic flow and remote vacuum chlorinators.

Conventional vacuum-type chlorinators are most commonly utilized for dry chlorine.

Liquid chlorine evaporators should be considered where manifolding multiple one-ton

containers would otherwise be required to evaporate sufficient chlorine.

8.9.1.3 Chlorine Supply

75

Cylinders should be considered where the average daily chlorine use is 150 pounds or

less. Cylinders are available in 100- or 150-pound sizes. One-ton containers of chlorine

should be considered where the average daily chlorine consumption is more than 150

pounds. Large-volume shipments of chlorine should be considered where the average

daily chlorine consumption is more than two tons. Large volumes of chlorine can be

secured by tank truck, rail car, or barge.

8.9.2.1 General Chlorination system design should consider the following design factors:

• Contact time.

• Level of disinfection required.

• Volume of wastewater being treated.

• Concentration and type of residual.

• Mixing with the effluent.

• pH.

• Suspended solids.

• Industrial wastes.

• Temperature.

• Concentration of organisms.

• Type and age of organisms.

• Ammonia and nitrogen compounds concentration.

Design of facilities for effluent disinfection must consider the above factors such that

reliable disinfection is achieved at all times. Modifications to disinfection system

designs and criteria may be considered by ecology on a case-by-case basis.

8.9.2.2 Capacity

Required chlorinator capacity will vary depending on the use and point of application of

the chlorine. Chlorine dosage should be established for each Disinfection

8.9.3 Type of Treatment Dosage range, mg/L Pre-chlorination for odor control 1.5 to 10

Primary effluent 5 to 10

Trickling filter effluent 3 to 10

Activated sludge effluent 2 to 8

Sand filter effluent 1 to 5

76

The design should provide adequate flexibility in the chlorination equipment and

control system to allow controlled chlorination doses at both minimum and peak

demands. The system should be easily expandable to increase capacity over the entire

life of the treatment plant. Special consideration should be given to the operation to

ensure the chlorination system is readily operable at minimum flows and low chlorine

demand without over-chlorination of the effluent. Several sizes of rotameters must be

supplied if necessary to ensure proper dosage throughout the life of the plant. Other

inplant uses of chlorine such as odor control, spray water disinfection, sludge bulking

control, and scum disinfection should be added to the chlorine use and demand

calculations if they are also served by the system.

TYPE OF TREATMENT DOSAGE RANGE (mg/L)

Pre-chlorination for odor control 1.5 to 10 Primary effluent 05 to 10

Trickling filter effluent 3 to 10 Activated sludge effluent 2 to 8

Sand filter effluent 1 to 5

8.9.4 Reliability For reliability it is necessary to have redundant chlorine feed equipment (such as a

minimum of two chlorinators and two evaporators). Generally the chlorine demands

should be divided into disinfection and non-disinfection uses, and separate equipment

provided for each group. Appropriate piping and controls shall be provided so that the

equipment used for non-disinfection purposes may also serve as backup for the

disinfection equipment.

Five criteria must be met to ensure reliable chlorine supply at all times:

(1) Adequate reserve supply to meet demands and delays in delivery.

(2) Scales to accurately weigh chlorine inventory and monitor use rate.

(3) Manifolded system to handle high demands and to utilize backup equipment.

(4) Automatic switchover from empty containers to full ones.

(5) Alarms to alert operators of an imminent loss of supply.

8.9.5 Mixing All chlorination systems shall include a way to thoroughly mix the chlorine solution

with the effluent water stream. Mixing will significantly influence coliform destruction

77

and achieve viral and pathogen kills. Mixing will also help minimize chlorine use. The

mixing may be accomplished in almost any type of hydraulic vessel (such as open

channel, closed pipe, tank, or baffled chamber). The mixing of chlorine (in water

solution) and wastewater effluent can be accomplished by hydraulic or mechanical

mixing. Hydraulic mixing should be done according to the following criteria:

a. Pipe Flow

• A Reynolds number of greater than or equal to 1.9 x 104 is required. Hydraulic jumps

for baffles may be used to create turbulence.

• A diffuser with orifice velocities of 15 ft/sec (minimum) to 26 ft/sec at peak flows

must be used.

• The diffuser must be set as deep as possible and at least two feet below minimum

wastewater level at low flows.

• Turbulent flow after mixing must be prevented in order to avoid chlorine

volatilization.

b. Open Channel Flow

A hydraulic jump with a minimum Froude number of 4.5 is necessary to provide

adequate hydraulic mixing. The point of chlorine injection should be just upstream of

the hydraulic jump because the location of the jump itself will change with variations in

flow rate. A Parshall flume is not a satisfactory location for hydraulic chlorine mixing.

c. Mechanical Mixing Mechanical mixing should be done according to the following criteria:

• A mixer-reactor tank is necessary that provides 0.1 to 0.3 minutes contact time.

• Inject chlorine just upstream from the mixer with a diffuser.

• Mixer speed should be a minimum speed of 50 revolutions per minute (rpm).

• The diffuser should be set at least 2 feet below the minimum water flow level at low

flow rate.

• Turbulent flow after complete chlorine mixing must be prevented in order to avoid

chlorine stripping.

78

DESIGN OF CHLORINATION TANK

• Design flow = 4.864 cumec

• Detention time = 60 sec

• Volume required = flow X detention time

• = 4.864 x 60

• Vrqd = 291.84 m3

• Provide, depth = 4.8 m

• Area = 60.80 m2 because( . .

)

• Length: Breadth = 2:1

• L x B = 2B x B =2B2 = 60.80

• B = 5.51 m ≅ 5.80 m

• L = 11.03 m ≅ 11.20 m

Provide: 11.20 m X 5.80 m X 4.80 m = 311.81 m3

79

8.10 Sludge Tank 8.10.1 Biological kinetic Equations Used V= Q2 Q Y (S-S0) .... (1) X (1 + kdQc)

∆= ....(2)

Qr .Xr = (Q+Qr)x ....(3) Q2 demand = 1.47 (So – S) Q - 1.4 X r (Q w) .... (4) Where, V = Volume of aeration basin, m3 Qc = Mean cell residence time based on solids in the aeration basin , day Q = Influent wastewater flow rate, m3/d Y = Yield coefficient over finite period of log growth, g/g So = Influent soluble BOD5 concentration mg/ℓ S = Effluent soluble BOD5 concentration mg/ℓ X = Concentration of MLVSS maintained in the aeration basin mg/ℓ (g/m3) Kd = Endogenous decay coefficient, d-1

∆∆

= Growth of biological sludge over time period

∆t, mg/ℓ (g/m3)

Q r = Waste sludge flow rate from the sludge return line, m3/d Xr = Concentration of sludge in the return sludge line, mg/ℓ (g/m3) Qw =Waste sludge flow rate from aeration tank, m3/d

80

8.10.2 Design Criteria used 1. Provide complete mix activated sludge process using diffused aeration system. 2. The effluent shall have BOD5 and TSS of 20 mg/ℓ or less. 3. Provide eight aeration basins with common wall. Each unit may be removed from

operation for repairs and maintenance while other units shall continue to operate under normal operating procedures.

4. The biological kinetic coefficients and operational parameters for the design purpose

shall be determined from carefully controlled laboratory Studies. The following kinetic

coefficients and design parameters shall be used.

Qc = 10 d

Y = 0.5 mg/mg X = MLVSS = 3000 mg/ℓ

Kd = 0.06 d-1

Ratio of MLVSS/MLSS = 0.8 Return sludge concentration (Xr) = 15000 mg/ℓ (TSS) BOD5 for the effluent (SS) = 0.63 Influent BOD5 and TSS = 200 and 150 (mg/ℓ) respectively. Average flow = 2.432 m3/s = 210124.8 m3/day. 8.10.3 Design Calculations for the Aeration Basins: Dimensions of aeration basin and sludge growth.

1. The concentration of soluble BOD5 in the effluent BOD5 exerted by the = 20 mg/ℓ * 0.63 Solids in the effluent = 12.6 mg/ℓ Soluble portion of = 20 mg/ℓ - 12.6 mg/ℓ = 7.4 mg/ℓ the BOD5 in the effluent

2. Treatment efficiency of biological treatment

eff. = ((200 mg/ℓ - 7.4 mg/ℓ) /200 mg/ℓ) * 100 eff. = 96% (percent)

81

3. Calculate the reactor volume

V= Q Qc Y (SO − S) X (1+ kdQc )

V = 210124.8m3/ d *10d * 0.5(200 −7.4)g / m3

3000g / m3 * (1+ 0.06d −1 *10d)

V= 202350144 = 42156.28 m3

4800

82

4. Dimensions of aeration basin: Provide eight rectangular aeration basins with common walls.

Water depth = 5 m

Volume for each basin = 42156.28 8

= 5269.58 m3

Surface area for each basin = 5269.58

5

= 1053.29

Provide length to width ratio = 2:1 ∴ A = 2W 2

Provide width for each basin =22.95 m

Provide length for each basin = 2 x 22.95

= 45.91 m Provide freeboard = 0.8 m

Total depth for each basin = 5+0.8

= 5.8 m

83

Calculations for the detention time:

Detention time = volume /Q

= 44126.20 X 24 = 5.04 hr 210124.8 Calculations of Qw and Qr : Calculate the growth of biological sludge over time period:

∆x/∆t = = ( ℓ ∗ . ∗ ℓ )

( ∗ / )

=12646.88 kg/day Assume (SS) contain 80 percent volatile matter

= . .

=15808.6kg / day

Qw = (15808.6*10 mg/day) / (15000 mg/ℓ *10 ℓ/m3) Qw = 1053.9m3/day (for all basins)

Qw = for each basin = 1053.9

8 = 131.73 m3 day.

Qr will be calculated from eq. (3) Qr . Xr = (Q + Qr) x

Qr = X .Q

=3000 *210124.8

(Xr − X ) (15000 −3000)

Qr = 52531.2 m3/day (for all basins) Qr for each basin = 52531.2 8

= 6566.4 m3/day

84

= ..

=0.25⇒OK d. Calculations of Oxygen Requirements

Average flow for each basin = 210124.8 8

= 26265.6 m3 /d

Qw for each basin = 1053.9

= 131.73m3 / d O2 demand

= 1.47 (So - S) Q - 1.14 Xr ( Qw ) O2 demand = 1.47 ( 200 -7.4) * 26265.6 * 1000 - 114 * 15000*131.73* 1000 = 5.18*109 mg/d

= 5183.7kg/d (for each basin).

Compute the volume of air required :

Assuming that air weights 1.2kg/m3 and contains 23.2 percent oxygen weight.

Theoretical air Required under = .

0.232푔푄2/푎푖푟∗1.2푘푔/푚3 Filed

condition = 18619.6 m3/d

Assume that the Efficiency of air Diffusers = 7 percent

85

Theoretical air = 1861.9 cu. Mt. / 0.07 = 265994.45 m3/d = 184.71 m3/min per basin Provide design air at 150 percent of the theoretical air Total design air = 265994.45*1.5 = 398991.67m3 /d =277.07m3/min per basin.

86

9. Canvas Presentation

88

10. Progress made in 8th semester

There are around 66,780 houses in Bharuch City, out of which 65% houses have soak pit and 35% discharge in open. There are around 327 public latrines located all around Bharuch city.

The amount of water which is being supplied to Bharuch city is 47.41 MLD, and the amount of wastewater generated is 80% of water being supplied or water demand (i.e. 37.91 MLD).

The per capita water supply is 140 LPCD and per capita sewage contribution is 112 LPCD (i.e. 80%) and there is also some unaccounted flow of water which makes 155.25 LPCD overall.

The year – 2014 is taken as Base year

Intermediate stage - 2029

Ultimate stage - 2044

The Total water supply for design area is 17.25 MLD, so according to calculation

Total sewage generated for design area would be 16.20 MLD (i.e. 80% of water supply)

Table. 9 Different location and their sewage collected

Sr. No. Location of Tank Area for water supply Covered

Total

(MLD) Sewage Generation

(MLD)

1 Maktampur Filter Plant


7.62 6.096

2

Station Tank Dhokikooi, Dandia Bazar, falshrutinagar, gheekudi, station Road, chingaspura and soci, etc

1.13 0.904

3

Sonerimahal Tank Hajikha Bazar, Bahadur Buras,

ChaklaSoneriMahal, Adus Road, Vhorvad, panchBatti, Ali etc.

1.25 1

4 Tower tank PhataTalav, dabhoiVad,

OcudaFaliya, Peerkanthi, Furja, Bazar etc.

2.8 2.24

5 Vejalpur Tank VejalpurNayanachowak, Alisjin Kali,

Talawadi etc. 1.45 1.16

89

6

Gujarat housing board Tank

Ssiddhnath Nagar, Gita park, Anank Nagar, Narayan Nagar, Yogeshwar Nagar, G.H.B in all schemes

3 2.4

7 Dungri 3 2.4

Total Bharuch 17.25 16.2

Population forecasting: When the design period is fixed the next step is to

determine the population in various periods, because the population of the

towns generally goes on increasing. The population is increased by births,

decreased by deaths, increased by migration, and increased by excession. These

are four factors which effect the change in population. The correct, present and

past population can be obtained from census office.The future development if

the town mostly depends on trade expansion, development of industries and

surrounding country, discoveries of mines, construction of railway station, etc.

These elements may produce rises, sow growths, stationary condition or even

decrease the population. For the prediction of population, it is better to study

the development 0f other similar towns which have developed under the same

circumstances because the development of the predicted town will be more or

less on the same lines.

The following are the standard methods for which forecasting of population are done are:

1) Arithmetical increase method

2) Geometrical increase method

3) Incremental increase method

4) Decreasing rate method

5) Simple Graphical method

6) Comparative graphical method

7) Master plan method

8) The logistic curve method

9) The apportionment method

90

We have chosen the Geometric increase method from the above method and will simultaneously verify it with other methods to the check the consistency of results and its variation.

Year 2001 - 167117 person (Bharuch city)

(30 years) 1971 to 2001 year- 20.20% to 25.27% growth rate

(1) Geometrical Increase Method Pn=P0(ퟏ + 풓

ퟏퟎퟎ) n

Pn= population in year 2044 P0 = present population is 1,85,545 (design area population year 2014) r = 30% assume (year 2014 to 2044) n = number of decades (3) Pn=185545(ퟏ + ퟑퟎ

ퟏퟎퟎ)3

Therefore according to mathematical calculation

Pn= 451906 person

Table.10 Different location and their sewage collected Sr No. Location of

Tank Area for water supply Covered Population

2014 (person)

Population 2044 (person)

1 Maktampur filter plant


47048 103364

2 Station Tank

Dhokikooi, Dandia Bazar, falshrutinagar,gheekudi, station Road, chingaspura andsoci, etc

14543 31950

3 Soneri Mahal Tank

Hajikha Bazar, Bahadur Buras, ChaklaSoneriMahal, Adus Road, Vhorvad, panchBatti, Ali etc.

19199 42180

4 Towar Tank PhataTalav, dabhoiVad, OcudaFaliya, Peerkanthi, Furja, Bazar etc.

44334 97401

5 Vejalpur Tank

VejalpurNayanachowak, Alisjin Kali, Talawadi etc.

23635 51926

6 Gujarat housing Board Tank

Ssiddhnath Nagar, Gita park, Anank Nagar, Narayan Nagar, Yogeshwar Nagar, G.H.B is all schemes

36786 80818

7 Dungri 20149 44267

Bharuch 185545 451906

91

The various data that are needed is collected in this semester by visiting various Government bodies and Literature review of various dignitaries are studied and analysed to project out with a best solution that would be beneficial for the Bharuch city.

All the datas have veen collected and calculations are done as per the design criteria.The waste water treatment plant designed is for the ultimate year 2044.It can be said that this treatment plant will work effectively till 2044 with no need of expansion of any unit.

The initial cost of this project maybe high,but in long run its economic.This treatment plant can be applied to any land area where thr river flows nearby has high Tubidity and BOD5.

92

11. Expected Outcome

Water is a renewable resource because it gets purified through evaporation

and rain; however, only about 3 percent of the earth's water is potable.

Although nature slowly cleans wastewater over time, the main benefit of

wastewater treatment is maintaining clean water for reuse. So,

implementation of our proposal would be a helping hand to nature in

maintaining the ecology of our environment. and on the other hand looking to

the future expansion of Bharuch city from population as well as pollution

point of view ,the establishment of waste water treatment plant is very

essential to sustain human life which is dependent on river Narmada, as this

is a precious resource and after all “water is life”.

In this present semester we have done

Identification of the problem

Solution generation

Solution analysis

Evaluation and choice,

Recommending the plan

Implementation work can be carried out thereafter.

Various data such as household and population data has been procured from

Government bodies. We also had a good interaction with many of Bharuch

Nagarpalika’s executive and city engineers and discussed the various ill-effects

of wastewater disposal.

At present the waste water of this city is directly being discharged in to the

river Narmada which significantly damaging the natural source. As it is a

natural source and also the and also a reason for human lives existing in this

planet, it becomes utmost important to preserve it.

The outcome of this project will be that the life span of this city will be

increased, unhygienic conditions will be diminished, better environment for

the people to survive, Healthier city.

93

We at this stage designing the wastewater treat plant to cleanup this city from

all unhygienic conditions and to present this population an infrastructure that

will offer them a better way to discharge the water efficiently.

For this we, approached to Bharuch Nagarpalika with the intention to gather

some information to availability of Government land. There are many barren

lands available, but the most efficient one was selected for our project. Our

tentative location is Ghelani Kuva vistaar which is at outskirt to this city and

also nearby to river Narmada, So that disposal of river becomes easy and

economic.

By implementation of this project we would be able to serve the population of

Bharuch city with safe and hygienic disposal of Waste water in to the Natural

stream. This will also add to the safe and pleasant living conditions of people of

this city.

1. District Profile CHAPTER - II

1.1. District Profile

The Bharuch district is part of South Gujarat, it is bounded by Vadodara district

and Kheda district in the North, Narmada district in the East, the Gulf of

Khambat in the West and Surat in the South. City is situated on the banks of

river Narmada. Bharuch is situated 182 km from Ahmedabad and 210 km away

from state capital of Gandhinagar. Bharuch is located at 21.7° N 72.97° E. It has

an average elevation of 15 meters (49 feet). It is Class-I town as per census 2001

with a total size of population 167117. Bharuch city has high potential for

growth and development as revels made available by the census 2001. Bharuch

city has shown moderate growth of population from 1971 till the year 2001

with growth rate operation wearing from 20.20% to 25.27%. Bharuch city has

all 100% urban population with no rural population. The population density of

district has grown from 176 persons/ km2 in 1991 to 210 persons/ km2 in 2001.

The decadal growth rate of the district was 19.37 for 1991-2001, which is below

the decadal population growth rate of the Gujarat state (22.48). The urban

population of the district accounts for 25.74% of the total population of the

district. The urban population is spread over 10 towns whereas the rural

population is spread over 1178 villages. Owing to its prime location between

Ahmedabad and Surat districts and the location of the industrial township of

Ankleshwar,

Bharuch has

immense potential

for economic

development.

Bharuch Town

95

Fig: 1 BASE MAP OF BHARUCH CITY

96

2. Bharuch Town Profile

2.1 Town profile

Bharuch town is the headquarters of Bharuch district and one of the historical

towns in Gujarat state and is as District Head Quarter. This very old town was

mentioned in historical records nearly 2000 years ago. The industrial activity in

the town dates back to the 17th century when the English and Dutch established

factories here. In fact Bharuch is one of the oldest cities in India and was a

flourishing port in earlier times. The oldest dockyard in the country was

developed in this town for import and export of precious stones available in the

region.

Bharuch was once but a small village on the banks of the Narmada River but that

rivers inland access to central and northern India and with a location in the

sheltered Gulf of Khambat in the era of coastal sea travel grew and prospered as

a trading transshipment centre and ship building port. Until very modern times

the only effective way to move goods was by water transport, and Bharuch had

sheltered waters in a era without weather forecasting, compasses, and when

shipping was necessarily limited to coastal navigation, and the general East-West

course of the Narmada gave access to the rich in land empires at the upper

reaches of the Narmada, including easy caravan access to the Ganges valley and

Delhi plain.

2.2 Demographics

Bharuch city has population of 167117 as per the census 2001 having an area of

17.35 km2. Highest decadal growth rate was recorded in 1961-1971 to be

25.27% and next highest growth rate 23.55% has been shown during 1981-

1991. Presently the city is facing a decreasing growth rate and the growth rate

has decreased from 23.55% to 20.20% which is less than that of State as 22.66%

Sex ratio which on average is 932 as compared to state level average which is

919. Literacy rate of Bharuch is 78.01%. The concentration of population was

approximately 175 persons/ha. The female literacy rate in the city of Bharuch is

83%.

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2.3 Geography

Topographic Map of India, clearly showing the rare West to East access given to

the North and Central river line valleys by the Narmada River from Bharuch. The

Narmada River outlets into the Gulf of Khambat through its lands and that

shipping artery gave inland access to the kingdoms and empires located in the

central and northern parts of the subcontinent of India. Level of difference of the

city is from 33 m to 5 m in city.

2.4 Rainfall

The district has a history of highly erratic rainfall although it receives a fairly

good quantity of rains annually. The rainfall data for the district as recorded at

Bharuch center is summarized below:

(Table 1: Rainfall data)

RAINFALL DATA FOR BHARUCH DISTRICT

DISTRICT CENTRE NORMAL

RAINFALL 2004 2005 2006 2007 2008 2009 2010

BHARUCH BHARUCH 891 523 536 885 1023 889 890 1478

2.5 Connectivity/Linkage

Bharuch is located on 21.40 northern latitude and 72.55 eastern longitudes. It is

situated on the right bank of river Narmada. It is at a distance of 28.80 km from

the sea and at a height of 17.92 mt from the sea level. The Dahej port is located at

a distance of 30 km. In the peripheral areas, mineral rich talukas like

Ankleshwer, Vagara, Amod are located within the city. Bharuch is connected with

Mumbai and Ahmedabad by broad-gage railway line, National Highway as well

as state transport service. It is connected with Jambusar Kavi village by narrow-

gauge railway line. Bharuch is a Junction station located on a Broad-gauge

railway line. It is connected with important cities of the state by rail and road as

motioned below.

98

(Table 2: Distances by rail & road)

NAME OF THE CITY DISTANCE FROM BHARUCH

BY RAILWAYS (k.m.) DISTANCE FROM BHARUCH

BY ROAD (k.m.)

MUMBAI 321 351

SURAT 60 67

VADODRA 70 75

AHMEDABAD 168 193

GANDHINAGAR nil 225

Bharuch has good network of roads including state and national highways that

connect the city with other parts of the state and the country. The state highway

passes through the city and provides high degree of connectivity of the city with

surrounding settlements. Another major road, from Mojampur to Dhorikui

Market and Palej-Nandeva road, also carries lot of importance in terms of

connectivity of the town with other areas. The under pass constructed near

railway station (which was in a very bad condition earlier has now been repaired

with the help of ONGC / GNFC organizations) has improved the movement of

goods traffic movements within and outside the city.

2.6 History and Culture of Bharuch

This Bharuch is one of the historical towns in Gujarat state and is as District

Head Quarter. This very old town was mentioned in historical records nearly

2000 years ago. The industrial activity in the town dates back to the 17th

Century when the English and Dutch established factories here. In fact Bharuch

is one of the oldest cities in India and was a flourishing port in earlier times. The

oldest dockyard in the country was developed in this town for import and export

of precious stones available in the region. Bharuch was also very important to

the sultans and other Muslim rulers who ruled Gujarat. There is an ancient

mosque called Masjid-U-Jani in Bharuch. It is an important monument to study

Islamic Architecture in Gujarat. Shukaltirth and Kabirvad are two important

picnic spots which are located at a distance of 16 and 18 Kms. respectively from

99

Bharuch. On Janmastami, huge fairs are organized here. At present, there is a

temple of Lord Shiva located near the Sardar Bridge built on river Narmada near

Jhadeshwar on the eastern part of Bharuch. It is an important place of

pilgrimage. Devotees flock this place during the month of Shravan. The Golden

bridge constructed by British ruler, is famous engineering structure of Bharuch.

The first British colony was established in Bharuch in 1616 and then in 1617, the

Dutch colony was established. Thereafter, Aurangzeb built a strong protective

wall around the city and gave it the name Shukabad. In 1772, it came under the

British Rule.

Bharuch has been situated at Narmada river so it has nos. of religious place

within it including temples, churches, mosques, Jain shrines &ParsiAgiyari.

Temples like KotilingeshwarMahadev, Kapileshwarmahadev, MotaBaliyadev,

these temples are not very old. In Dandia bazaar Swaminarayan temple was built

in V.S. 1891 (A.D. 1835), it was built up in memory of Sahjanand Swami. In the

middle of the town there is a temple of BhruguBhargeshwar which is known as

Nava Dera, houses Vaishnav Haveli of Narayan Dev. In Ali area, famous temple of

Sindhavai Mata is situated. Behind Sewashram there is an ancient temple of

NilkanthMahadev and it is believed that it was constructed in 19th century. Near

PakhaliOvara area, a famous temple of KamnathMahadev and here nine planets‟

statues are there, so it is also famous as a “Nine planets temple”

Besides above places mention, the other heritage monuments which exist in

Bharuch city are:

a) Grave of Sufi –Saint “Dada Rehan”

b) Ancient Farsi stone with inscriptions of Umad-Ui-Mulk

c) Fort of King Siddhraj Jay Sinhji – constructed during the Solanki period (1094

to 1143)

d) 400 year old LalluChowk’s Haveli famous for its wooden carvings.

The temple of 4 Veds (oldest sacred books of the Hindus) – Ruguvved,

Atharvved, Yajurvved, Samved and the only temple having the statues of four

Veds with iconography

In Bharuch city the Jain shrines of Kavi, Gandhar and Zagia are situated. Bharuch

city Jama Masjid which was founded in 1326 AD is still in existence and near civil

hospital there is mosque founded by Murtazkhan in the year 1609 AD is also in

existing with good wooden columns and the windows having wooden carvings.

100

In Bharuch city, Parsi people have noticeable population and for their prayer and

worship purpose there are seven Agiyaris in the town. Among all seven Agiyaris,

Pestanji‟sagiyari is the oldest.

In the year 1814, Roman Catholic Church scent was founded, called “Our lady of

Health”, this was destroyed in the year 1860 and the same Church was

reconstructed in the year 1887. In the year 1856, Protestant people had founded

their church.

Fig 2: Corridor and Boundary map

101

2.7 City map

Fig 3: Base map of Bharuch City

2.8 Existing water supply arrangement of Bharuch town

At present average daily water supply is 20 MLD in Bharuch municipality out of

this 6 MLD from ground water and 16 Bulk purchase of raw water, Out of this

total water supply Bharuch supply 1.5 MLD to Outgrowth areas.

(Table 3: Existing situation in water supply in Bharuch)

S.NO WATER SUPPLY UNIT VALUE

Access and Coverage Bharuch

1 Total connections no 23607

2 Coverage of water supply connections % 45.7

3 Total water supply MLD 20.0

4 Total storage capacity MLD 17.25

102

SrNo. Location of Tank Area for water supply Covered

CapacityGLSR (MLD)

Capacity ESR (MLD) Total(MLD)

CoveredPop.

1Maktampurfilter plant

Pritam Society, Dipali Society,A vadhat Nagar, Gayatri nagar,Kask, Rachana Nagar etc. 6.27 1.35 7.62 47,048

2 Station tank

Dhokikooi, Dandia Bazar, Falshruti nagar,Gheekudi, Station Road, Chingas pura & Soci, etc 0.23 0.9 1.13 14,543

3 Soneri Mahal Tank

Hajikha Bazar, Bahadur Buras,Chakla Soneri Mahal, Adus Road,Vhorvad, Panch Batti, Ali etc. 0.35 0.9 1.25 19,199

4 Towar TankPhata Talav, Dabhoi Vad, Ocuda Faliya,Peerkanthi, Furja, Bazar etc. 2.8 2.8 44,334

5 Vejalpur TankVejalpur Nayana chowak, Alisjin Kali,Talawadi etc. 0.45 1 1.45 23,635

6Gujarat Housing BoardTank

Ssiddhnath Nagar, Gita park, Anank Nagar, Narayan Nagar,Yogeshwar Nagar, G.H.B is all schemes 2 1 3 36,786

7 Dungri 2 1 3 20149Bharuch 12.1 5.15 17.25 185545

BH

AR

UC

H

Service levels and Quality

5 Per capita supply of water Lpcd 56.0

6 Continuity of water supply hours 4.0

Source: Municipality

Drinking water is being supplied by Gujarat Narmada Fertilizer Corporation (GNFC),

since 1983. GNFC supplies water tapped from Narmada river canal at Zanor near

Ankleshwar village for Bharuch city which is having undulating terrain with steep slopes

area and city is having small stretches of plain areas. This poses a unique challenge for

the water distribution system and network system as many households have to undergo

either with non-availability of water or at very low pressures despite of the fact that

they have the properties have water connections.

Existing water supply arrangement is based on local tube wells drilled in the vicinity of

the town. Details of tube wells, pumping machinery, connecting ESR is as under.

(Table 4: Location of OH water tank and their capacity)

Quality of Water

Narmada river water is tapped by GNFC at Zanor near Ankleshwar village at 21

km from Bharuch through 3.5 mt. dia. RCC intake well. The water is treated by 2

nos. of rapid gravity filtration plant with clariflocculators. The 2 treatment plants

are of capacities 9 MLD and 13.5 MLD. Water is stored in 2.27 ML RCC clear

water sump at Maktampur. The water supplied from 10 nos. of bore wells also

have the chlorination facilities for the treatment of water before it is being

103

distributed to the Bharuch city. The quality of water is potable, chlorinated PH

level and quality is maintained for the use of population needs. The water

pollution is eradicated when found contaminated by changing the pipeline or

repairing the leakages whatever the case may be. As per the chemical analysis

reports, the water quality as per ISI 10500:1991 is found to be fit for

consumption. During summer season, the water level goes down substantially

reducing yield from the tube wells. Hence the quality concerns are higher in this

season. The comparative quality standard of water as per the national and

international standard is given below.

As per the report, the Bharuch municipality is taking care to make the drinking

water potable for the consumption of population. The treatment by Chlorination

and the alum are the main tools used for treatment of water. There are 2 nos. of

water filter plant existing in Bharuch with capacity 9 MLD and 13 MLD

respectively. These treatment plants are 30 and 20 years old which have expired

there useful life of 15 years.

(Table 5: Borewell Location)

LOCATION OF BOREWELLS Nos.

Gujarat Housing Board 5

Sabugadh 1

Dungri 1

Limbu Chhabadi 1

Limdi Chow/Matadia Talav 1

Maktampur 1

Water which is supplied from these bore wells are fitted with pumps connected

to the local distribution system. The bore well at Maktampur is discharging the

clear water directly to the sump. There are two conventional type of treatment

plants having 9.0 MLD and 13.5 MLD capacities constructed by GWSSB were

commissioned in year 1981 and 1990 respectively. The treatment plants consists

of circular type presettlement tank, pump house, channels for mixing Alum,

clarifiocculators, rapid sand filter beds, chlorination house and clear water sump.

The tube well (ground water) system of water is not acceptable by the municipal

104

authority as the quality of water is not potable and hence these tube wells are

not in use presently. Also the pumps are very old and poorly maintain which has

affected their efficiency.

Water storage

The water storage available for the distribution system at GSR (Ground storage

reservoirs) and ESRs (Elevated storage reservoirs) are given below. The storage

facility of new reservoirs at GHB (Gujarat Housing Board) and Dungari are

nearing completion and hence are considered as existing. The work is going on

and connecting mains are being laid at present. Considering the existing total

available storage and total demand of 34 MLD, the storage capacity appears to

around 60% of the total need which is fairly good. But this distribution of supply

for the city is not meeting the total requirements, hence there is need to create

more storage system which may be provided at Jadeshwar area with new

reservoir.

Distribution system

The distribution system is mainly through the reservoirs at five locations with

75.0 km length of pipeline. The distribution pipes were laid in the year 1963 and

extended as and when funds were made available, along with the improvements

schemes taken up from time to time. The materials for pipes used for

distribution are AC, PVC and Cast iron. However, the length of distribution

system is substantially less compared to the number of household connection

and in connection to road length; the actual length available is on the higher side.

The details of the age, pipeline material and length of pipes are given as under:

(Table 5: Pipe Network and material made of)

Sr. No Network Pipe Material Length of pipe (k.m.) Age

1 Main Flow (from source to city) Cast Iron 16 50 yrs

2 Feeder (main) flow (transition)

main from source to storage place Hume steel 5 40 yrs

3 Distribution Network (from storage to customer/standpost)

Cast Iron 27 40 yrs

Source: Municipality

105

Frequency of water supply

As per the information made available by the municipality, the frequency of

water supply is normally 2 to 11 hours a day, out of which 2 to 6 hours are in the

morning and 2 to 5 hours in the evening time. However, most of the consumers

get water for less numbers of hours due to their location at tail end or at higher

levels. Inequitable distribution is a common problem particularly faced by the

residents in old town due to steep slopes and ineffective valves operations.

(Table 6: Details of water distribution from existing source)

Water tank/ Tube Well Morning Time

Evening Time Service areas

Station Tank 7:00 - 11:30 6:30 - 11:30

Dholikui area,Narmada society,Pushpakunj ,Baranpura,Railway

sump & 24 Hours supply to S.T.depot and fire brigade Tanks

Soneri Mahal 3:00 - 9:30 4:00 - 9:00 Swaminarayn Slope to vhorwad area,Paanch Batti Fatatalavo areas

Tower Tank 3:00 - 7:00 5:00 - 7:00 Entire tower areas of PriKanthi

Vejalpur tank 4:00 - 6:30 5:00 - 7:00 Machinate,Kumbhariya dholav,Suthar faliya & Vejalpur area

GHB Tube well No. 1 5:00 - 11:00 3:00 - 8:00 Krishnanagar,rangavarsha,Valshruti,Sindh

unagar,Gandhigram,gayatri nagar,Mukti Nagar

GHB TW2 5:00 - 11:30 2:00 - 1:30 Siddhnath Nagar,maruti nagar,Neelkanth nagar,Green park, Narain nagar

GHB TW3 6:00 - 10:00 4:00 - 8:00 Ayodhya nagar area Part- I

GHB TW4 6:00 - 11:00 4:00 - 8:00 Mukti nagar, Bahumali upto Anand mangal

society GHB TW5 5:00 - 11:30 3:00 - 8:30 Matariya talav surrounding area

Sabugadh Tubewell 8:00 - 11:00 3:00 - 6:00 Mundafaliya,khatkivad,Dabhoiyavad,Ali

patel faliya,garijanavad

Dungri Tubewell 5:00 - 7:30 3:00 - 5:30 Nanidungri,MotiDungri areas

Limbu Chhapri Tubewell 5:00 - 7:30 Due less yield frfom this well water is supplied during morning hours only

Limdi Chowk 7:00 - 9:00 3:00 - 5:00 Limdi chowk,Vejalpiur tank area

2.9 Existing Sewerage system

As Bharuch city has undulating terrain, storm water drainage is special problem

for disposal. Presently the city has uncovered open drains resulting in overflow

and choking. These open drains are not cleaned regularly. Also due to the

proximity of sea, the city also has tides coming into the city areas. This adds to

the problem of drainage and storm water disposal. During the heavy rains and at

the times of high tides, the water remains for a longer period, particularly in the

low lying areas. The Station-Jambusar road is situated on the rain-water flow of

surrounding villages which is always full of problems. The 4 Nallas located in this

area are not cleaned up regularly and this also causes inundation. Bharuch city

receives rainwater flow from 20-25 villages which causes the flooding to the city

areas. Even 4 to 5 inches of rains during the rainy season causes heavy floods in

the city areas.

(Fig:4 Present drainage problem)

2.10 Design Criteria

Table 7: Calculation

Project Area Bharuch town

Base year 2014

Intermediate stage 2029

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Ultimate stage 2044

Per capita sewage contribution 112 lpcd i.e. 80% of Water demand

Ground water infiltrates -

Peak factor 3.00, depending upon contributory population

Co-efficient of Roughness: Salt glazed stone ware, Good / Fair – 0.012/0.015, for

coller joint n=0.011

Sewer Net work Minimum velocity 0.80 m/s

Maximum velocity 2.40 m/s

Man hole spacing @ 30 m along straight length

@ deviations @ Branch @ tail end

Depth of flow 0.80 full @ ultimate peak

Invert drops: For sewer less then 400mm 1: 100 to 1:1500

Man hole Type A Type (150 to 600 dia.) Up to 1.50 m.

B Type (150 to 600 dia.) 1.51 to 4.00 m.

C Type (150 to 1500 dia.) 4.01 to 6.00m.

Scraper MH (150 to 1500 dia) 2.50 to 9.00m

S Type sewer Above 950 mm 100 to 300 m. spacing

Self Cleaing velocity 0.6 meter/second

Maximum permitted depth of

flow up to 400 mm dia

0.80 d

Spacing of manholes 30 mt or junctions

Software Manual Hydraulics Design

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Pumping machinery non clog Sewer Submersible pump

Rising Main DI pipes

Treatment SBR TYPE STP

2.11 Need for Project

It is absolutely necessary to go for establishing underground piped sewerage

system to upgrade the status of sanitation of the municipality area from the

consideration of health ground. As in Bharuch town is no underground drainage

system in city and the system of septic tanks and soak pits for latrines in the

household is being used for the disposal of sludge at the household level. For

slum areas, the toilets having low cost sanitation are being provided by

constructing the soak pits and septic tanks and the subsidy provided by the

municipality.

The amount of sewage generated in Bharuch is about 37.91 MLD i.e.

approximately 80% of the daily water supply of 47.41 MLD. At present Bharuch

city has no sewerage system and most of the houses have their own septic tanks

and soak pits. Most of which are located below the road levels in gamtal areas.

The existing sewerage system in Bharuch city is open and unhygienic within the

city and having high population density. Due to presence of black cotton soil, the

permeability is low hence over flow from the septic tanks and soak pits is

common problem. The flow from these soak pits is discharged into the nearby

natural nalla (ravine) and finally the untreated wastewater is directly flowing

into the river Narmada. The undulating topography of gamtal area, the sewage

water and sludge is not effectively drained off. The natural drains passing

through the city get filled up during the development process and together with

storm water; the drainage problem gets aggravated during the rainy season.

During rainy seasons the water overflows on the roads, which are already

uneven, the traffic movement is greatly affected and damages to the properties

also occur in gamtal area. Due to the unhygienic disposal of sewage, mosquito /

flies nuisance is prevailing in most of the areas. The Bharuch municipality is

constructing the open drain system for disposal of sewage water in gamtal area.

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The rubbish of the city and human excreta are disposed off outside the city

through night soil tankers. There are 327 public latrines in different areas of the

city.

The following in general inference, which established the need of project:

The sewage is disposed off into River Narmada or nearby natural streams

without treatment. So to stop the pollution of natural water bodies, a need

is there to provide a treatment plant for Bharuch town.

Sewage treatment is absolutely necessary to bring the sewage to desired

standards before its disposal into the river.

Where the water supply status will be improved, there will be improvement

in the adequate availability of water in the municipal area releasing

increase wastewater flow. If no downstream facilities like underground

drainage facilities are provided, unsanitary conditions will definitely

increase by way of overflowing drains, flow of wastewater on roads,

ultimately inducing health hazard.

At present, the wastewater is released in the river and natural streams

without any treatment. Large cesspools are formed, which putrefy and give

foul smell. These are places where mosquitoes breed. The wastewater also

pollutes the ground water. Large numbers of well and tube-wells provided

are also affected by this way due to pollution.

Around 66780 houses are in Bharuch.

Around 65% houses are having soak pits and 35% defecate in open.

In Bharuch town, existing open drains carry sullage causes bridging of

mosquitoes and unhygienic atmosphere.

In view of above, Bharuch Nagarpalika, Bharuch has taken up the project for the better environment of the town people.

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3. Bharuch Sewerage system Augmentation

3.1 Waste water quantity for Bharuch

Per Capity Water Supply 140 lpcd

UN Accounted Flow of Water (UPF) 15%

Total 155.25 lpcd

80% of 140 lpcd is considered as daily dry weather flow i.e. 112 lpcd

3.2 Proposed Augmentation

(Table 8: Design Criteria)

Project area Bharuch town

Base year 2014

Intermediate stage 2029

Ultimate stage 2044

Per capita sewage contribution 112 lpcd i.e. 80% of Water demand

Peak factor 3.00, depending upon contributory population

Co-efficient of Roughness: Salt glazed stone ware, Good / Fair –

0.012/0.015,RCC pipes for coller joint n=0.011

Sewer Net work Minimum velocity 0.80 m/s

Maximum velocity 2.40 m/s

Man hole spacing @ 30 m along straight

length

@ deviations @ Branch @

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tail end

Depth of flow 0.80 full @ ultimate

peak

Invert drops: For sewer less then 400mm 1: 100 to 1:1500

Man hole Type A Type (150 to 600 dia.) Up to 1.50 m.

B Type (150 to 600 dia.) 1.51 to 4.00 m.

C Type (150 to 1500 dia.) 4.01 to 6.00m.

Scraper MH (150 to 1500 dia) 2.50 to 9.00m

S Type sewer Above 950 mm 100 to 300 m.

spacing

Self Cleaing velocity 0.6 meter/second

Maximum permitted depth of flow up to

400 mm dia

0.80 d

Spacing of manholes 30 mt or junctions

Software Manual Hydraulics Design

Pumping machinery non clog Sewer Submersible pump

Rising Main DI pipes

Treatment STP

Collection and Conveyance System

The collection and conveyance of sewage system is explained in detail.

I) Sewer Network

Design of sewer network will be divided as under:

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1 Hydraulic Design

2 Structural Design

3 Selection of Pipe Material

3.2.1 Hydraulic Design

3.2.1.1 Adopted Design Criteria –

The design of Bharuch sewerage system has based on the design criteria given in

the manual on Sewerage and Sewage Treatment (Second Edition) 1993

published by CPHEEO, Urban Development Department, and Govt. of India and

prevailing standard engineering design practices.

3.2.1.2 Design Period

The planning for sewerage network of Bharuch is done considering 2044 as the

ultimate year.

3.2.1.3 Design Population

The network has been designed for the projected population of year 2044.

3.2.1.4 Flow Assumption

As intended by city planners, it is assumed that the NagarPalika will find ways

and means to supply water to the city at a uniform rate of 112 LPCD in all

command areas. This includes extraction of water from private bore-wells. The

rate of sewage generation is taken as 80 % of the water supply. The estimated

peak flow adopted for hydraulic design depends upon contributory population.

3.2.1.5 Peak Factors

Based on the recommended value of peak factor as per CPHEEO’S manual on

Sewerage and Sewage Treatment the peak factors adopted for contributory

populations of drainage area. Depending upon the contributory population, the

peak factor changes, it being higher for less population and lower for high

population.

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(Table 9 presents CPHEEO’s criteria for peak factors)

Contributory

Population

Peak Factor as per

CPHEEO

Recommended Peak

Factor

Upto 20,000 3.0 3.0

20,000 – 50,000 2.5 2.5

50,000 – 7,50,000 2.25 2.25

Above 7,50,000 2.0 2.0

3.2.1.6 Flow Friction Formulae

For design purpose, the flow of sewage in pipes is presumed to be a steady and

uniform flow. The most popular equation for calculation of velocity and head loss

for flow conditions like gravity sewers is the Manning’s formula and Darcy-

Weisbach formula respectively. The Manning’s equation has most widespread

application.

Recommended Equation

Manning’s formula given below is commonly used for design of sewers.

V = 1/n (3.968 x 10-3) D2/3 S1/2

Q = 1/n (3.118 x 10-6) D8/3 S1/2

Where,

Q = Quantity of flow in lps.

S = Slope of hydraulic gradient line.

D = Internal diameter of pipeline in mm.

V = Velocity in m/s.

n = 0.015 for pipes upto 600 mm diameter

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= 0.013 for pipes above 600 mm diameter will be adopted for design.

(Table 10 Coefficient of Roughness used In Manning’s Formula)

Type of Pipe Material Condition n

Salt glazed stone ware

pipes

(a) Good

(b) Fair

0.012

0.015

Cement concrete pipes

(with collar joint)

(a) Good

(b) Fair

0.013

0.015

Asbestos cement 0.011

Plastic (smooth) 0.011

3.2.1.7 Depth of Flow

It is necessary to size the sewer to have adequate capacity for the peak flow to be

achieved at the end of design period, so as to avoid steeper gradients and deeper

excavation. For the ultimate design period, the sewers are designed flowing 80%

full (d/D = 0.8).

3.2.1.8 Velocity of Flow

The flow in sewers varies widely from hour to hour and also seasonally, but for

purpose of hydraulic design peak flow is adopted. However, it is to be ensured

that a minimum velocity is maintained in the sewers even during minimum flow

conditions. At the same time the velocity should not be excessive to cause

erosion.

Velocity of Minimum flow

It is necessary to size the sewer to have adequate capacity for the peak flow to be

achieved at the end of design periods, so as to avoid steeper gradient and deeper

excavations. For design of sewers, minimum velocity should be 0.60 mps. To

avoid erosion in the sewer network, velocity more than 3.0 m/sec is not allowed

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in the present design. As per CPHEEO manual minimum velocity and slope

recommended are presented in Table 9 for peak flows up to 30 LPS.

(Table 11 Recommended Slopes for Minimum Velocity)

Present Peak flow in lps Slope per 1,000

2 6.0

3 4.0

5 3.1

10 2.0

15 1.3

20 1.2

30 1.0

The minimum diameter of 200 mm is used for public sewers.

Erosion and Maximum Velocity

Maximum velocity in sewer is not to exceed 3.0 mps. However, in the initial

sections where very less population is served by sewer the minimum velocity of

0.6 mps is not available. For cleaning of such sewers/sections the flushing is

required. The provision for flushing the sewer is made in the project equipment.

Depth of flow and velocity of collecting pipeline should be checked for its

minimum and maximum values as per the CPHEEO Manual.

3.2.1.9 Sizing of Pipes and Slopes

The size of pipes and slope is calculated for contributory population based on the

population density of the respective administrative wards forecasted for the

design year 2044. The pipe diameter is selected by considering pipe flowing 80

% full for the ultimate flow. The corresponding flattest slope is provided so as to

achieve the minimum required self-cleaning velocity with an aim to minimize

sewer depth thus ensuring reduced cost.

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Minimum Pipe Size:

The sewerage system for Vapi has been designed considering the minimum size

of sewer as 200 mm.

3.2.1.10 Minimum Depth of Cover

The starting manhole depth of the proposed sewers ranges from 1m to 2.5m

depending upon the topography and detail of road planning network available.

The minimum depth of cover depends on the depth of the starting manhole and

subsequent ground level of the road along the sewer.

3.2.1.11 Sewer System Layout Planning

City is divided in to 5 zones for convenience of sewer system Planning. Sewer

System is planned according to falling of contour and ground levels.

Software Used

Sewer CAD software is used for designing of pipe line, partially.

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4. Manholes

Man holes form one of the essential structures in any sewerage system. They are

generally provided at every change of alignment of sewer at every junction of

two or more sewers at head of all sewers or branches, wherever there is a

change in size of sewer and at regular intervals in the sewers and other

maintenance operations.

Spacing of manholes (CPHEEO Manual Page 74) sewer which are to be cleaned

manually, which can not be entered for cleaning or inspection, the maximum

distance between manholes should be 30 m.The spacing of manholes on large

sewers above 900 mm diameter is governed by the following for the sewers to

be cleaned manually.

(a) The distance up to which silt or other obstruction may have to be

conveyed along the sewer to the nearest manhole for removal.

(b) The distance up to which material for reports may be conveyed through

the sewer and

(c) Ventilation requirements for men working in the sewer. CPHEEO Manual

recommends further as under spacing on straight run may be allowed as

under:

(i) 900 mm to 1500 mm dia - 90 to 150 m.

(ii) 1.5 m. to 2.0 m. dia - 150 to 200m.

(iii) Over 2.0m. dia - 300m.

However, manhole spacing is adopted as under for this sewerage system.

(a) For sewers upto 450 mm dia -30 m. c/c

(b) For sewers 500 to 900 mm dia -40 m.c/c

(c) For sewers 1000 to 1600 mm dia - 50 m. c/c

(d) For sewers 1800 mm dia & above – 60 m c/c

4.1 Type of Manholes

The CPHEEO Manual on sewerage and sewerage treatment (Second Edition)

provides consideration of following type manholes.

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4.1.1. Rectangular manholes- The minimum internal sizes of rectangular

manholes between brick faces should be as follows.

For depth of manhole less 0.9m. 900x800mm.

For depth of manholes form 0.9m. and upto 2.5m., 1200x900mm.

4.1.2. Arch type manholes – for depths of 2.5 m and above, arch type manholes

can be provided and the internal sizes of chambers between brick faces

shall be 1400 x 900 mm the width of manhole chamber on besides and

junctions of pipes with diameter greater than 450 mm should be suitably

increased to 900 mm or more so that benching width on either side of

channel is at least 200mm.

4.1.3 Circular manholes – Type circular manholes may be constructed as

alternative to rectangular and arch type manholes. Circular manholes are

stronger than rectangular and arch type manholes and thus these are

preferred over rectangular as well as arch type manholes.

The internal diameter of circular manholes may be kept as following for

varying depths.

i) For depths above 0.9m. and up to 1.65m – 900 mm dia.

ii) For depth above 1.65 and up to 2.30 m - 1200 mm dia

iii) For depth above 2.30m. and up to 9.0m – 1800 mm dia

iv) For depth above 9.0 m and up to 14.0 m – 1800 mm dia

4.2 Gujarat Water Supply and Sewerage Board uses Sewer Manholes of

following types:

a) Manhole type ‘A’ circular type having inside diameter of 1200 mm for

depth up to 1.5 m depth (for 150mm to 500 mm dia sewer).

b) Manhole type ‘B’ circular type having inside diameter of minimum

1500 mm and for depth from 1.5 m to 4.0 m (For 150 mm to 500 mm

dia sewer)

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c) Manhole type ‘C’ circular type having inside diameter of 1500 mm and

for depth beyond 4.0 m to 6.0 m (For 150 m to 500 mm dia sewer)

d) Manhole type ‘D’ circular type having inside diameter of minimum

1500 mm and for depth beyond 6 m to 10 m.

4.3 Vent shafts

In well designed sewerage system, there is no need to provide ventilation. The

ventilating columns are not necessary where intercepting traps are not provided.

However, nominal provisions for vent shafts are suggested for the escape of air

to take care of the exigencies of full flow.

4.4 House Connection and Chamber

Necessary provision for house connection with chambers and 100 mm dia stone

ware pipe is in the project. The one chamber will be provided between two

houses. At present in Vapi city residential building and non residential building

40,000. Considering fast development of city the approximate no of building will

be 64000 in intermediate stage. Thus, considering 10% approx. for poor people

above 57600 building will require house connection against which existing

house connected are 40000. Thus, approximately 17600 building will have to be

provided with sewer facility. For immediate stage 32,000 additional buildings

will be provided with facility of house connections. Considering one connection

between two houses the 16,000 additional house connections are proposed in

the project. Provision for resurfacing the roads damaged during the excavation

of pipelines is made in the estimate of sewer collecting system.

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5. Sewage Pumping Station

5.1 Civil Works

5.1.1 General

The area in which the pumping station is situated is fixed generally by the duty it

has to perform, but the precise site varies so as to take into account the following

considerations:

a) As pumping station are frequently low-lying areas, consideration should

be given to the possibility of flooding and information should be obtained

as to the highest recorded flood levels in the area.

b) The pumping station site should be above the highest recorded flood

level, but when construction on ground liable to flood is unavoidable, it

should be so designed that motors are well above the highest recorded

flood level and above the coping of the wet well or suction chamber.

c) The site should be selected if possible so that in the event of power failure

any overflow which occurs may be diverted or will find its way into

watercourse without causing flooding or serious damage to property;

however, this should not pollute any water course used for drinking

water purpose.

5.1.2 Nuisance

A pumping station should be located at a distant as possible from the residential

properties on account of possibility of complaints for noise or smell.

5.1.3 Capacity of pumping stations

The capacity of the pumping station is designed considering present and future

sewage flows for a design period of 15 years as per CPHEEO manual. The civil

structure & pipeline of wet well is designed for a flow of 30 years. Therefore, the

pumping station is designed based on needs of future expansion especially in

respect of provision of additional space for pumping units.

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5.1.4 Type of pumping stations

Generally, pumping station has two wells – the wet well receiving the incoming

sewage, having alongside a dry well housing the pumps. Uses of wet pit pumps

need not the dry well. However, in designing the pumping station, either both

wells or only wet well are required is decided based on the design period of the

project space available and the types of the pumps selected.

There are four types of the pumping arrangements as mentioned in the CPHEEO

manual:

A) Pumping station with Vertical Pumps in Dry Well:

In this option, Centrifugal pumps with bottom suction are installed in dry

well. The motor are installed on the floor which are separately casted

below the loading – unloading platform. In this way we are avoiding the

losses due to the shaft extension up to loading-unloading platform and

also unnecessary cost of the shaft length. The maintenance of the

pumping machinery is very easy and hence the life of the pumping

machinery is long. In flooded condition, the motor are not damaged as

motor are installed on the higher level. However, in this option

periodically maintenance of the extended shaft is very difficult. The cost

of civil construction of the dry well is recovered as the operational and

maintenance cost of the pumping machinery is less with respect to other

type of pumping arrangement.

B) Pumping station with Vertical Pumps in Wet Well

In this option Vertical turbine pumps are installed in wet well. The motor

are installed on the floor above the ceiling of the wet well. As the pumps

are installed in the wet well, the dry well is not necessary.

C) Pumping Station with Submersible Sewage Pumps in Wet Well

In this option, pump-motor sets are installed in wet well. As the pump-

motor sets are installed in the wet well, the dry well is not necessary.

D) Pumping Station with Horizontal Pumps in Dry Well:

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In this option, Horizontal non clog Centrifugal pumps with side suction

are installed in dry well. The motor are installed on the same foundation

on the pumps are installed. Hence, in this option, during flooded condition

there is possibility of the damage of the motor. Also, the width of the

pumping station is also more as compare to above two options. So this

option is not feasible.

5.1.5 Design considerations for wet well

5.1.5.1 Wet Well

The size of the wet well is influenced by the storage capacity to be provided. The

storage capacity is required to be designed, especially for all sewage pumping

stations, where automatic controls and variable speed drives are not provided to

match pumping rates exactly with inflow rates to the station. The selection of the

proper storage capacity is critical because it affects:

a) The time for which the liquid will be retained in the pumping station, and

b) The frequency of operation of the pumping equipment.

The shape of the wet well and the detention time provided shall be such that

deposition of solids is avoided and sewage does not turn septic. The capacity of

the wet will is also concerned with the difference between the highest level of

the liquid in the wet well and the minimum level after the depletion by pumping.

This should be such that the pump of minimum duty also would run for at least 5

minutes. The capacity of the well is to be so kept that with any combination of

inflow and pumping, the cycle of operation for each pump will not be less that 5

minutes and the maximum detention time in the wet well will not exceed 30

minutes of average flow. This is as per CPHEEO Manual.

Considering the above requirements of CPHEEO Manual, the wet well for 30

minutes of average flow is provided. Whenever possible, grit removal

ahead of pumping should be adopted to increase the life of the pumps. Coarse

screen before the wet well will be provided having a clear opening of 25 mm

between the bars for the manually cleaned type. The screening units will be

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provided in duplicate. The screens will conform to IS 6280. The coarse screen

with opening of 25 mm between the bars will be provided for manually cleaned

screen. The detail design of screen is appended vide Annexure-3(a), 3 (b), 3(c)

The details of pumping stations provided are presented in Table.15

The plinth level of pumping station and sub-pumping stations are kept

considering highest flood level in monsoon for protecting pumping main and

electrical equipments. Considering site situation, by pass arrangement is

provided to divert the sewage flow in nearby drain in emergency for main

pumping station.

5.2 Plant machinery

5.2.1 Pumps

5.2.1.1 Requirement of sewage pumps

As per CPHEEO manual, the capacity of a pump is usually stated in terms of dry

weather flow (DWF) estimated for the pumping station. The general practice is

to provide 3 pumps for a small capacity pumping station comprising 1 pump of 2

DWF, 2 of 2 DWF for large capacity pumping stations. 4 pumps are usually

provided, compromising 2 of 1 D.W.F. and 2 of 2 D.W.F. capacities. Overall

capacity of pumping machinery is proposed as per manual.

For protection against clogging the suction and delivery openings of the pumps is

not be less than 100 mm and the pumps to be capable of passing a ball of at least

100 mm dia.

5.2.1.2 Pumping Station

Generally, the pump capacity is decide on the basis of the following factors:

Average and Peak Flow

Capacity of the wet well available.

Carrying capacity of the receiving sewer.

The capacity of the pumps shall be adequate to meet the peak rate of flow with

50% standby. To obtain the least operating cost the pumping equipment shall be

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selected to perform efficiently at all flows including the peak flow. The effect of

the minimum flow during initial stage is also to be considered for the designing

of the capacity of the pumps. The size and number of the pumps are so selected

that the variation of inflow can be handled efficiently without starting and

stopping the pumps too frequently and long retention of sewage in wet well.

The number of different sized units is to be selected after studying the overall

economy and should be kept as low as possible to facilitate repairs and to reduce

the number of necessary spares to a minimum.

Though ideally required pumps are recommended, in many cases where the

inflow is more, the average capacity pumps become very large and are beyond

the range of pumps manufactured. In such cases, more numbers of smaller

capacity pumps are recommended. In case the capacity of the wet well is large

enough, and inflow is relatively less, lesser number of higher capacity pumps can

be installed. Both the above option have a limitation that the receiving sewer

shall be of adequate size to carry the sewage flow.

5.3 Selection of type of pump

A sewage pump should be reliable and unchockable and accessible for quick

maintenance, robust and wear resisting and some measure of overall efficiency

may have to be sacrificed to secure these properties.

The type of pumps to be installed at each pumping station should be judge on its

merits in relation to the rate of pumping the total head, physical-composition of

the sewage, preliminary treatment before pumping as per CPHEEO manual.

The type of pumps available for handling of sewage may be divided broadly in to

three groups:

a) Centrifugal pumps

b) Submersible pumps

c) Pneumatic ejectors

Pneumatic ejectors are not recommended unless other types of pumps are

impractical as may be is small installation.

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Initially Submersible pumps are economic as for the installation of submersible

pumps single well is to be constructed. But the operational cost of the

submersible pumps is high as compare to vertical non-clog pumps. In

submersible pump-motor sets, the removal of heat due to electric losses from

submersible motor is achieved by natural & forced convection through the water

flowing over the motor case. Hence, greater the motor case surface area, more

heat is removed but the rotor diameter is increased which will lead to greater

friction – loss and hence power. Therefore for larger capacity, the overall

efficiency of the submersible pump-motor sets is less as compared to vertical dry

well mounted pumps.

For vertical non-clog dry well mounted, the initial cost is high due to dry well is

to be constructed. However, the operational and maintenance cost per annum is

low as compare to submersible cost, therefore the initial investment is to be

recovered within the life of pumping machinery.

It is proposed to provide submersible pumps for the three pumping station consisting of wet well only. Pumps will be provided SETC submersible type.

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6. Sewage Pumping main

6.1 Requirement for Pumping the Sewage

A sewerage system is designed for collection, treatment and disposal. The design

of the system to be used depends on both technical and financial considerations.

Gravity lines, as the proceeds towards downstream end, the depth of sewer line

increases to maintain the required gradient. Sometimes the gravity sewer line

depth becomes too large to maintain required gradient. In such situation, apart

from the difficulty faced during installation, the cost of lying becomes prohibitive

due to high excavation/maintenance cost. In such cases a pumping main at

nominal depth reduces excavation/maintenance cost.

The flow in sewers is not constant & generally varies considerably at different

hours of the day. It also varies seasonally. Also during the early life of the

pumping stations the flow in the sewers may be substantially below the design

flow. For this type of irregular flow, the discharge from the pumping stations

provides a beneficial flushing effect in the sewers.

Following benefits are there by providing the pumping of the sewage.

Avoidance of excessive depths of sewer

The drainage of low lying parts of an area

A flushing effects for the irregular flow i.e. below the design flow

The development of areas not capable of gravitational discharge to a

sewage treatment works.

Avoiding an inverted siphon

The centralization of sewage treatment

6.2 Design of Economic size of pumping main

The cost of pipe material & its durability for design life are the two major

governing factors in the selection of pipe material. The pipeline may have very

long life but may also be relatively expensive in terms of capital & recurring costs

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& therefore, it very much necessary to carry out a detailed economic analysis

before selecting a pipe material.

To determine the most economical choice, the principles of economics must be

applied through long term cost benefit analysis known as ‘Life Cycle Cost

Analysis’. In this analysis a time value is placed on money, future expenditures

are discounted and brought back to the present period. A direct comparison of

the total present values or present work, reveals which alternate is lower in cost.

The economical size of pumping main will be based on for the following analysis

factor.

1) The pipe size will be consider such that during average flow 0.6 m/s

velocity may achieve and during peak flow velocity may be more than 0.8

m/s and not exceeded than 3 m/s will be considered.

2) Design horizon of 30 year (as stipulated by CPHEEO) divided in two

phases.

1st Phase – 1st 15 years

2nd Phase – 2nd 15 years

And the volume of sewage to be conveyed during two phases.

3) Different pipe sizes are considered to calculate the least cost in design

life.

4) The capacity & installed cost of the pump set required against the

corresponding sizes the pipeline under consideration.

5) The energy cost at Rs. 5 per KW will be considered. The interest rate will

be considered at 8% as per prevailing bank rate.

6) The capitalized cost will be worked out for the capital cost and energy

cost.

From the above the most suitable pipe material and size form techno economic

point of view will be considered as a pumping main.

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SEWAGE TREATMENT PLANT

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