Greywater management through development of effective treatment technology

IRJMST Volume 5 Issue 4 [Year 2014] Online ISSN 2250 - 1959

International Research Journal of Management Science & Technology http://www.irjmst.com Page 47

Greywater management through development of effective

treatment technology

Sandeep Narnaware*, D. B. Patil*,

Pawan Labhasetwar**, Mukta Singh Chandel***,

*Department of Environmental Science,

Institute of Science, Nagpur, India

**National Environmental Engineering Research Institute,

Nagpur, India

***Department of Civil Engineering,

Maulana Azad National Institute of Technology, Bhopal, India

ABSTRACT

In India, many habitations experience severe water scarcity particularly during summer

season. Due to the decline in the availability of freshwater sources, it is important to

explore affordable, implementable and safe solutions to alleviate water problems. The

reuse of greywater is the best alternative and water management practice to preserve

water resource and face water scarcity in rural and urban areas. This laboratory scale

study presents the finest design of greywater treatment system, which is a combination of

natural and physical treatment consist of feed cum collection tank and filtration followed

by storage and disinfection. The greywater reuse system is developed for the treatment of

various sources of greywater. The economical performance of the system were

investigated separately for the treatment of bathrooms, laundries and mixed greywater

collected from different locations in urban and peri-urban areas of Nagpur, Maharashtra,

India.

The cost-effective and efficient technology for treating greywater holds good potential

for removal/reduction of turbidity, total suspended solids along with the chemical oxygen

demand, biochemical oxygen demand), total kjeldahl nitrogen and significant reduction



in total coliforms and fecal coliforms . The treated greywater is collected, treated and

reused for irrigation purpose and in future can be used for toilet flushing, floor washing

and gardening. The performance evaluation of lab scale greywater reuse system initiate

more effective process for urban and peri-urban areas and can be used worldwide for the

conservation of water.

Keywords: greywater, Water Safety Plan, chemical oxygen demand, total kjeldahl

nitrogen

INTRODUCTION

The gap between supply and demand for water is widening and reached on such alarming

level that in some parts of the world poses the threat to human existence with increase in

global population (Pangarkar et al., 2010; Parjane & Sane, 2011). Considering above,

greywater recycle and reuse system is the best water management practice with great

importance and development, to achieve sustainable water consumption in urban and

peri-urban buildings along with rural territories (Santos et al., 2012). Greywater is the

urban wastewater, excluding any contribution from toilets and generally includes sources

from baths, showers, hand washing basins, washing machines, dishwashers and kitchen

sinks (Albury NSW 2012; Gupta 2012). In cases where the balance between non potable

water demand and production allows, a sub division is common by restricting the sources

to the lower polluted ones, such as showers, baths and washing basins (Jefferson et al.,

2004).

In terms of microbiological quality, raw greywater may contain 3.8*104

cfu/100 mL of

FC (fecal coliforms) and 1.6*107 cfu/mL of HPC (heterotrophic plate count) bacteria

(Gilboa & Friedler 2008) which, though much lower than those found in raw sewage,

must be adequately reduced when reuse of treated greywater is desired. Thus, a treatment

system is needed; however, in some cases its configuration and investment costs can

make it impractical (Goddard 2006).

Considering the above mentioned problem the present work is focused on the greywater

reuse through the greywater treatment system. The present article presents a lab sale

study on a low cost and easy maintenance experimental system for greywater reuse with a



collection cum sedimentation tank and a treatment system composed of a filter and

chlorine disinfection. The objectives of this study include analysis of the treatment

efficiency and assessment of the water quality potential of treated greywater. For this

study, raw greywater was collected from washing basin of public and exclusive access to

toilets as well as from showers of a changing room.

MATERIALS AND METHODS

Experimental system

The experimental system of greywater treatment includes a feed cum sedimentation tank,

a filtration system and a disinfection unit. The system was built to provide short residence

time for the collected greywater and to disinfect it immediately before its reuse, in order

to minimize the possibility of the regrowth of microorganisms. The plastic feed cum

sedimentation tank is 100 liters, with 0.3 m high and a diameter of 0.2 m. The water

entrance is through the top of the tank and the solids are accumulated at the bottom of

tank, since there is no mixing device installed. The easily available and natural materials

were used as filter beds in the filtration unit such as coarse particles (equal

size) sand bed and bed of gravels of different mesh size. The bed height of each material

was determined and finalized by the experimentation. In case of clogging, the

backwashing is provided in the filter unit for cleaning purpose. One advantage of this

type of filter is that the cleaning process is automatic and quick, taking only 8 to 12 s to

clean the filter. Cleaning effluent is drained to the wastewater network system. The

disinfection unit consists of a plastic tank where disinfection is done by adding the

chlorine in treated greywater to remove the microbial contamination. A pump of 0.5

horse power is provided to pump the treated greywater for using various non-potable

purposes and the same is used for backwashing phenomenon. In this treatment unit, the

pipes and accessories used of plastic and all the systems, including the collection tank, is

prepared to be easily transported and installed, requiring only electrical supply and a

sewage connection to the filter cleaning discharge. From the previous study (Pangarkar et

al., 2010) the depth of each bed were selected as 0.15 m and 0.2 m for coarse sand and

gravels respectively from bottom to top in the filtration unit.

Sample collection and analysis



Bathroom greywater from main drain of showers from a changing room of swimming

pool located at NEERI colony, laundry greywater from WCL laundry and mixed

greywater from residential complex at Ajni railway colony located in Nagpur,

Maharashtra. The process of collection and treatment of greywater on the experimental

system presented in this study was repeated four to five times in each location, on a

weekly frequency.

Samples of raw and treated greywater were taken, preserved and analyzed in accordance

with Standard Methods for the Examination of Water and Wastewater (APHA 1995; Rao

et al., 2003). Determined parameters include pH, Total Suspended Solids (TSS)), Total

Dissolved Solids (TDS), and Organic Matter (COD and BOD). Additionally, parameters

like Chloride, nitrates (NO3), phosphates (PO4), Sulphates (SO4), sodium (Na),

potassium (K), magnesium (Mg) and calcium (Ca), alkalinity were determined of raw and

treated greywater sample for the performance study of the plant. Samples of raw and

treated greywater were also analyzed for microbial parameters, namely total and fecal

coliforms, according to Membrane Filter Technique (Clesceri et al., 1989), in the

Microbiological Laboratory of the National Environmental Engineering Research

Institute, Nagpur.

RESULT AND DISCUSSION

Raw greywater

Since domestic wastewater is generated as by-product of human activities, its quality, in

terms of constituents and concentrations, is expected to vary widely. Greywater quality is

no exception as it can be seen by the wide range of values for each parameter presented

in Table 1. This variability can be explained by the different uses given to sanitary

installations (bathroom, laundry and mixed greywater) by diverse people and

consequently the amount of dirtiness, soaps, bathing products and other pollutants varies

accordingly with every usage.

The physico-chemical and microbiological characteristics of greywater are presented in

Table 1. It was observed that greywater quality is highly fluctuating. Turbidity of

bathroom, laundry and mixed greywater was found to be 36.2, 132 & 154 NTU in raw


International Research Journal of Management Science & Technology http://www.irjmst.com 1

greywater while in treated greywater; it was 4.61, 27 & 25 NTU respectively. Raw

greywater contains nitrate in bathroom, laundry and mixed greywater 16, 23 & 24 (mg/l)

whereas treated greywater has nitrate 20, 19 & 18 (mg/l) respectively. It was also evident

from the results that COD and BOD were sufficiently reduced during the treatment.

There is a significant reduction in microorganisms after treatment. It was found that the

raw greywater contains total and fecal coliforms but after treatment the count is

substantially reduced.

COD concentrations, ranging from 432 to 560 mg/l, were similar among samples from

the three raw greywater collection places, and were also comparable to the ranges of

value presented in previous studies. (Al-Jayyousi 2003; Friedler & Alfiya 2010; Friedler

et al., 2006; Friedler, et al., 2005; March et al., 2004).

Table: 1 Physical-Chemical Analysis of Greywater

Source Bathroom

greywater

Laundry

Greywater Mixed greywater

Parameter Raw Treated Raw Treated Raw Treated

pH 7.9 7.7 7.6 7.2 7.9 7.6

Conductivity (μS ) 326 306 560 498 553 492

TDS (mg/l) 231 210 380 330 332 295

TSS (mg/l) 38 5 138 28 160 28

Turbidity (mg/l) 36.2 4.61 132 27 154 25

Salinity (mg/l) 166 149 186 164 192 172

Alkalinity (mg/l) 120 128 168 140 184 160

Chloride (mg/l) 32 30 52 48 68 56

Total Hardness (mg/l) 148 208 112 164 168 172

Ca Hardness (mg/l) 48 64 64 88 84 96

Mg Hardness (mg/l) 100 144 48 76 76 86

Sodium (mg/l) 36.8 33.9 198 162 142 128

Potassium (mg/l) 3.5 2.7 7.2 6.4 4.6 4.1

Nitrate (mg/l) 16 20 23 19 24 18

Sulphate (mg/l) 17 79 35 69 28 46

DO (mg/l) 2 5 1.8 4.2 1.2 4.6

COD (mg/l) 448 160 432 156 560 186

BOD (mg/l) 305 109 68 45 180 56

Total Coliform

(cfu/100ml) 8.2*10

3 0 3.6*10

1 0 TNTC 0



Faecal Coliform

(cfu/100ml) 7.2*10

3 0 4.3*10

1 0 TNTC 0

Treatment efficiency of the greywater collection, treatment and reuse system

The parameters such as turbidity, TSS, Nitrate, COD and BOD were considered to

evaluate the performance of greywater treatment in terms of percentage improvement in

water quality. All the physico-chemical parameters along with microbiological result

indicates that water quality parameters are improved significantly after treatment as

shown in Fig. 1. Moreover, Coliform bacteria were considered to evaluate disinfection

efficiency. The results indicated that raw greywater were contaminated with Coliform

and there is significant reduction in Coliform after treatment. pH is not influenced by the

proposed treatment, as it maintains a similar value before and after treatment. Solids,

especially suspended ones, have the highest reduction after treatment however total

dissolved solids are less affected. In general, the reduction of organic matter provided by

this treatment was significant, especially for BOD. It is also verified that the COD/BOD

ratio increases in almost every sample after treatment, indicating that BOD is more

affected by filtration than COD. This result is in accordance with Friedler et al., (2008)

that conclude that greywater contains slowly/non-biodegradable organic matter,

especially in a dissolved form.

Results presented in Table 1 correspond to coliform analysis made to single samples of

raw and treated greywater from each collection site. After complete treatment, no

coliform bacteria were detected in both presumptive and confirmation tests, except for the

bathroom greywater samples in which small numbers of microorganisms were observed,

but, again, negative results were obtained in the confirmations tests, revealing that those

microorganisms are not coliforms. A study, made by Gilboa and Friedler (2008) on

removal and regrowth of FC, HPC, P. aeruginosa sp., S. Aureus, Clostridium perfringes

sp. and also three viral indicators in treated greywater, concluded that FC was the most

resistant bacteria to UV disinfection at low doses (up to 69 mJ.cm-2

). At higher radiation

doses FC were completely removed but HPC remained high which was due to presence

of resistant bacteria.



Fig.1 % Removal in the quality of treated greywater

Reuse potential

To assess the potential of reusing treated greywater from the presented experimental

system, results of quality parameters were compared with the Portuguese technical

specification and other regulatory documents from other countries (Table 1). As it can be

seen, pH, total and fecal coliforms of treated greywater are in accordance with the quality

parameters defined in the checked documents but BOD and TSS are too high. All values

fall within those reported in other literatures consulted about greywater reuse systems.

Besides the quality requirements for greywater reuse, there are other aspects that must be

considered, such as the investment costs, the maintenance needs and the suitability for

on-site application. The experimental system presented in this study is relatively

affordable, does not produce any waste other than those originally presenting in raw

greywater and retained by the filter, and has a small footprint for easy installation. It

justifies further investigation and development in order to accomplish the limits for TSS

and BOD, by:

• Using finer filtration screen;

0

10

20

30

40

50

60

70

80

90

100

% R

emo

va

l

Parameter

% Change in the quality of greywater

Bathroom greywater

Laundry greywater

Mixed greywater



• Applying a coagulant in the sedimentation tank to promote the agglomeration of organic

matter and thus improve the efficiency of the filter.

The experimental treatment system showed potential for greywater recovery, because of

the simple, low-cost and easy maintenance features, and also because it provides high

reduction of SS, COD and BOD. More signifi-cantly, no total or fecal coliforms were

detected in all treated greywater samples. However, concentrations of SS and BOD after

treatment were not low enough to reach the limits presented in legal and reference

documents, hence further improvement procedures are suggested.

CONCLUSION

Greywater reuse is a potential method to reduce potable water consumption in buildings

and, therefore, to reduce wastewater discharged to public sewage systems and treatment

plants. The environmental and economic benefits of such an approach are significant.

Nevertheless, a greywater treatment system must meet those mentioned criteria of

reliability, safety and cost. This study shows that the presented experimental unit, that

uses a conventional process of treatment built with existing technology, can achieve

relatively good results of greywater treatment, particularly in filtration and disinfection.

In terms of set-up, the unit is considered economic, reliable and safe to be implemented

for on-site application. However, unexpectedly lower removal of TDS, COD and BOD

may hinder its acceptance, as the treated water appears turbid and may cause undesirable

odor after a short period of storage in toilet flushing tanks. Since the residual BOD after

filtration is dissolved and colloidal forms, it is suggested that, in future, this treatment

unit should include addition of coagulant in the sedimentation tank and application of

finer filter.

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Greywater management through development of effective treatment technology

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