CEW 542 WATER AND

WASTEWATER ENGINEERING

INFRASTRUCTURE

TOPIC 4

WASTEWATER

TREATMENT

INFRASTRUCTURE

-overview of ww -

LECTURER: MDM SALINA BINTI ALIAS

ROOM: 5.23 PERDANA BLOCK

LESSON OUTCOME

Able to explain the source of wastewater

and differentiate the types of wastewater

Able to determine the population

equivalent (PE) and what it represent for.

Able to estimate the quantity and quality

of wastewater based on PE

Source of wastewater

Wastewater

Domestic Industrial Municipal Infiltration and Inflow

SOURCES

Domestic or sanitary wastewater

- refers to liquid discharge from residences, business buildings and institutions.

Industrial wastewater

- is the liquids discharge from manufacturing plants.

Municipal wastewater

- liquid collected in sanitary sewers and treated in a municipal plant

Infiltration

- flow of groundwater into sanitary sewers

Inflow

- storm water flows into sanitary sewers

DOMESTIC WASTEWATER

Volume – varies depending on sewer uses. - normally 50 – 250 gal per capita per day

Quantity and strength of ww from schools, offices factories and other commercial establishments depend on hours of operation and available eating facilities.

In selection of data for design, the quantity of organic strength of wastewater should be based on actual measurements taken throughout the year to account for variations resulting from seasonal climatic changes and other forces.

The organic matter contributed per person per day in domestic ww is approximately 11 g of suspended solid and 90 g of BOD in communities where a substantial portion of the household kitchen wastes is discharged to the sewer system.

INDUSTRIAL WASTEWATER Ordinarily discharge their wastewater to the city’s sewer system after

pretreatment.

Pretreatment at the industrial site must be considered for wastewater having strength or characteristics significantly different from sanitary wastewater

The majority of manufacturing wastes are more amenable to biological

treatment after dilution with domestic wastewater.

It characteristics vary from industry to industry, treatment process also vary.

- food processing wastes - contains sufficient nitrogen and phosphorus for biological treatment but discharge from chemical and materials industries is deficient in growth of nutrients.

- petroleum, handling animal fats and plant oils – contains lot of grease. - metal finishing, battery manufacturing plants and electroplating

processes – contains toxic chemicals, such as cyanide, lead, oil, chromium and other heavy metal.

Industrial wastewater expressed it quantity of flow and pound of BOD

(quantity and strength) related to the number of persons that would be required to contribute an equivalent quantity of wastewater.

MUNICIPAL WASTEWATER

The flow in sanitary sewers is a composite of domestic and industrial wastewater, infiltration and inflow, and from intercepted flow from combined sewers (Figure 4.1 shown a schematic system of municipal wastewater).

Design criteria

– pipe must be sized to carry peak flow.

- waste strength ( organic matter) greatest during workday.

- at night – amount of organic matter is reduce – slow velocities in pipes permit settling of solids.

- quantity and it characteristics of ww fluctuate with season of the year and between weekdays and holidays.

Infiltration

groundwater entering sewers and building connections through defective joint – broken or cracked pipe/manhole.

depends on

- condition of pipe and pipe joints,

- groundwater level and

- permeability of the soil.

Inflow water discharge into sewer pipes or

service connection from

- foundation drains,

- roof leaders,

- cooling water from air conditioner and

- yard area drain.

Main Composition of Pollutants in

Wastewater

Although wastewater can be polluted by many materials, the most common contaminations found that cause damage to natural watercourses or create human health problems are:

- organic materials - organic loading (BOD, COD)

- nitrogen (N)

- phosphorus (P)

- suspended solids, SS (dissolved/suspended & biodegradable)

- pathogenic organisms (bacteria, viruses etc)

Table 5.1 (from pg 209) gives the sources of municipal

wastewater along with their contaminants.

The composition of wastewater

from a given collection system

may change depend on:

* season,

* dilution,

* fluctuation in quality.

Factors Affect the Flowrate of

Wastewater

1. Amount of water supplied

2. Population

3. Leakage

4. Type of sewer

5. Loss of water

6. Season

7. Socio-economy and religion

PURPOSE OF WASTEWATER TREATMENT

Prevent pollution at the receiving water

Prevention of disease, protecting the health and

well-being of community

To obtain permissible/allowable quality of effluent

(final quality of wastewater after treatment) which

meet with Standard A or Standard B.

EFFLUENT STANDARD

GUIDELINES

Malaysian Standard MS 1228:1991. Code of

Practice For Design And Installation of

Sewerage Systems

Malaysian Sewerage Industry Guidelines by

SPAN

i. Volume III ( Sewer Networks and Pumps Stations)

ii. Volume IV ( Sewage Treatment Plants)

iii. Volume V (Septic Tanks )

Says, influent quality is 280mg/L BOD dan 360mg/L SS.

If Standard B is needed, thus the effluent value for BOD dan SS must be <50mg/L dan <100mg/L

Therefore engineer must design suitable wastewater treatment plant

Residential

Area

Wastewater

treatment

plant

BOD5 = 280mg/l

SS = 360 mg/l

Standard A

<20 ?

<50 ?

River

Volumetric Flowrate (Q) vs

Population Equivalents (PE)

Volumetric flow rate is the main parameter to

design sewage treatment plants, sewerage

network or sewer system and pump stations.

Thus volumetric flow rate must be estimated.

Population Equivalents (PE) is one of the

method to estimate flowrate

Type of Establishment Population Equivalent

Residential 5 per house

Commercial : Includes offices, shopping complex,

entertainment / recreational centres, restaurants, cafeteria and theatres

3 per 100m2 gross area

School / Educational Institutions : - Day schools / Institutions

- Fully residential - Partial residential

0.2 per student 1 per student

0.2 per non-residential student 1 per residential student

Hospitals 4 per bed

Hotel with dining and laundry facilities 4 per room

Factories, excluding process water 0.3 per staff

Market (Wet Type) 3 per stall

Market (Dry Type) 1 per stall

Petrol kiosks / Service stations 15 per toilet

Bus Terminal 4 per bus bay

Taxi Terminal 4 per taxi bay

Mosque / Church / Temple 0.2 per person

Stadium 0.2 per person

Swimming Pool or Sports Complex 0.5 per person

Public Toilet 15 per toilet

Airport 0.2 per passenger/day

0.3 per employee

Laundry 10 per machine

Prison 1 per person

Golf Course 20 per hole

The PE may be converted to a flow rate using a simple formula such as set out in Malaysian Standards 1228 (MS1228).

Exercise1 Determine the population equivalent from

the following data.

i. Shopping complex and commercial building each

with 2 blocks of buildings and floor area of 10

000 m2/floor and a height of 3 storeys.

ii. Two primary school with 400 students of each

school

iii. A secondary school with 1200 students

iv. A bus station with 20 public toilets and 30 bus

bays

v. Residential with 2500 houses

vi. Hospital with 300 beds

MS 1228

Flowrate (𝑚3/𝑑𝑎𝑦) =𝑃𝐸 𝑥 1000 𝑥 0.077 𝐵𝑂𝐷 𝑘𝑔/ 𝑑𝑎𝑦 /𝑝𝑒𝑟𝑠𝑜𝑛

𝐵𝑂𝐷 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛, 𝑚𝑔/𝐿

PE =𝐵𝑂𝐷 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛, 𝑚𝑔/𝐿

0.17𝐵𝑂𝐷/ 𝑑𝑎𝑦 /𝑝𝑒𝑟𝑠𝑜𝑛

PE =𝑂𝑟𝑔𝑎𝑛𝑖𝑐 𝑙𝑜𝑎𝑑 𝑓𝑟𝑜𝑚 𝑝𝑟𝑒𝑚𝑖𝑠𝑒𝑠 , 𝑚𝑔/𝐿

𝑜𝑟𝑔𝑎𝑛𝑖𝑐 𝑙𝑜𝑎𝑑 𝑓𝑟𝑜𝑚 𝑜𝑛𝑒 𝑝𝑒𝑟𝑠𝑜𝑛

Organic loading

Organic loading = Q(m3/capita.day) X BOD(gram/m3)

Organic Loading = 𝐹𝑙𝑜𝑤𝑟𝑎𝑡𝑒, 𝑄 𝑥 𝐵𝑂𝐷

Calculate the organic loading of

wastewater if the BOD5 concentration is

300 mg/L and quantity of water is 200

L/unit

Exercise 2

If the organic loading for a sewage is 60

gram/day and has a flowrate of 182

liter/capita.day, calculate

a) BOD concentration

b) BOD if the flowrate is 100 liter/capita.day

c) Comment?

Solution 2

Organic loading = (300 x 10-3)(200)

= 60 g/unit

a) BOD concentration = (60)/182

= 0.3297 g/L/capita

= 329.7 mg/L/capita

b) BOD concentration = (60)/100

= 600 mg/L

Exercise 3

If an industry has a flow of 1500 liter/day and

BOD 2000 mg/L, convert into PE. Assume

organic loading BOD for one person is 70

gram/day.

Solution 3 If an industry has a flow of 1500 liter/day and BOD 2000

mg/L, convert into PE. Assume organic loading BOD for one person is 70 g/day.

Q = 1500 L/day

BOD = 2000 mg/L

Organic loading = Q x BO

= (1500) x (2000) = 3 000 000 mg/day

= 3000 g/day

PE = 3 000 /70 = 42.857 = 43