- Original Research
- Open Access
Grey water pollutant loads in residential colony and its economic management
© Shankhwar et al; licensee Springer. 2015
Received: 17 July 2014
Accepted: 7 November 2014
Published: 20 January 2015
The present paper deals with the organic loadings of grey water with its average and maximum flow rate on an hourly and daily basis generated from the residential colony of G.B. Pant University of Agriculture and Technology, Pantnagar, India. For reliable quantification, the study was conducted at the interval of 1 h for eight consecutive days in each season during the year 2012 to 2013. Following parameters viz biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrogen, phosphorus, and potassium analyses were used to calculate grey water pollutant load. The observed annual average organic pollutant loading in terms of BOD was found to be 29.44 kg/day with maximum load in the summer season. However, this organic loading at maximum flow rate basis (in peak hours) was varied seasonally from 55.3, 52.0, and 83.3 kg/day, respectively, during the monsoon, winter, and summer seasons. The grey water discharge flow rate reveals the need of a treatment system compatible with fluctuating pollutant loads. The bioefficacy of phytoremediation-based technology was assessed and found to be maximum in the summer season. Hence, it is found to be the best suited green alternative for combating the fluctuating pollutant load.
These days' technology involved in wastewater treatment uses innovative, efficient, and advanced methods. However, these need to be economically viable, especially in the rural part of India in order to support wastewater treatment and reuses. Freshwater scarcity is a worldwide challenge for sustainable development. Human interference, inadequate freshwater supply, and inappropriate management leads to more pollutant load of water. Thus, the reuse of municipal wastewater is becoming an important issue with increasing water demand for human consumption and agricultural production (Shankhwar and Srivastava 2012). Vis-à-vis, the green technology based on the short rotation-plantation fertigation system worked like a panacea. For this purpose, the quantification of generated wastewater and its pollutant load is a prerequisite asset. Domestic wastewater is often categorized into black water (from toilets) and grey water (from bathrooms and kitchen). The drivers of wastewater generation from the nonpoint sources of pollution are multiple, and consequently, grey water characteristics and discharge flow rate also varied greatly and are tedious to predict (Piao et al. 2010; Koutsouris et al. 2010; Wagener et al. 2010; Bring and Destouni 2011; Destouni et al. 2013). Besides this, due to population explosion, the grey water generation escalates in a multifold ratio. The unequal generation of wastewater with a continuous variation in time series from hour to hour, day to day, and month to month (Henze et al. 2000) creates a major hurdle in the preparation of a blueprint for any wastewater treatment strategy. Therefore, in the current scenario, there is an emergent and urgent need for accurate information about generated wastewater with its hourly, daily, and seasonal variation as a major prerequisite prior to designing and establishing any wastewater treatment plant and reuse plan. This calls for a time-to-time update about the flow rate and pollutant load of generated wastewater. Grey water represents 70% of total domestic wastewater which has relatively fewer loads of pollutants in comparison to black water and negligible amounts of heavy metals and pathogens (Pandey et al. 2014). Thus, grey water enables optimum concentration of pollutants to harness as nutrients and holds a great potential of recycle and reuse as well. Keeping in view all these factors, the main goal of present research was exclusively to investigate the grey water discharge pattern and organic pollutant load generated from hostels and residential colonies of a university campus. Mitigation of grey water pollution by harnessing the available nutrients through green management technology like the Short Rotation Intensive Cultural Plantation System (SRICPS) can be further introduced for sustainable use of wastewater as a resource.
Project site description
Geographically, the study location lies about 30 km southwards of the Shivalik range of the Himalayan foothill at 29° 1′55″ N latitude, 79° 28′ 25″ E longitude and at an altitude of 243.8 m above the MSL. The site was selected in the residential area of G.B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, India for grey water assessment. The area has humid, subtropical climatic conditions with 1,608 mm mean annual rainfall.
Selection of location for grey water quantification
The location was selected in the main drainage channel from the residential colonies of Shastri Enclave and Shivalik Enclave, etc. near Shri Maha Kaleshwar Nath Temple, Pantnagar. The grey water samples were collected from the drain before it joins the Barur River which is around 200 m away. The analysis of discharged grey water for pollutant load and flow rate estimation was intentionally done at the same location for more accuracy of results.
Grey water quality analyses
Grey water composite samples were analyzed in triplicates with the flow rate measurement and sampling for other analyses also done simultaneously. The selected water quality parameters were pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total solids (TS), total suspended solids (TSS), total dissolved solids (TDS), total carbon (TC), total nitrogen (TN), total phosphorus (TP), and total potassium (TK). For the qualitative analysis, one composite sample was taken into triplicates for representing each individual day characteristics of grey water. All of the mentioned water quality parameters except total carbon and total nitrogen were analyzed as per the standard method (APHA 1998). TC and TN were analyzed through total organic carbon (TOC) analyzer instrument.
Grey water flow measurement
The values of a and b were taken as 1.34 and 2.48, respectively, and defined on the basis of observations for overhead height H, in the range of 0.06 to 0.13 m, respectively (Robert 1986).
Grey water in organic loading
Where OL is organic load (kg/day), Q is daily flow (m3/day), BOD5 is BOD taken at 5 days (mg/l), and 1,000 is used to convert in kilogram per day from gram per day.
Green management technology for grey water recycling
The green management of grey water pollutant load can be done by harnessing the phytoremediation ability of short rotation trees. Crops require a high quantity of nutrients to harvest their potential yields. The system overall is input intensive (Jeet et al. 2014). This ability provides the new avenue of biomass production even at marginal wastelands and bunds. Furthermore, it facilitates the more resilient ecosystem on economic basis. Hence, the SRICPS was assessed for the treatment of grey wastewater. A Eucalyptus hybrid (clone K-413) was fertigated with grey domestic wastewater for biomass production trial under SRICPS. For the dual purpose of biomass production and phytoremediation, the saplings of Eucalyptus hybrid (clone K-413) were transplanted in November 2010 in an experimental trial field of University farmland. The Eucalyptus hybrid (clone K-413) is a hybrid product selected by virtue of its wide adaptability of climatic conditions, phytoremediation potential, and timber wood yield as well as resistance against various insects, pests, and diseases. In the trial, the plantation was intensively fertigated with the grey water in serpentine and channel irrigation regimes. The bioefficacy of SRICPS to remediate grey water was assessed with the tree biomass productivity as well (Shankhwar and Srivastava 2014).
Results and discussion
The quantification of grey water generation was calculated in terms of average values of hourly, monthly, daily, and annual basis. The average value of observed grey water generation was recorded to be 86.76 (l/person/day (lpd)) liters per capita per day. However, this value was around 64% of that recommended by the Indian Standards (IS: 1172-1963), i.e., water consumption requirement of 135 lpd. Generally, 75% to 85% of wastewater discharge is considered sewage water which includes black and grey water, but in the present case, the black water is allowed to go into the septic tanks of each house, hostel, and college because the University campus has no sewage treatment facility.
G rey water characteristics and seasonal discharge pattern
Grey water quality a (mg/l except pH)
Grey water organic load (kg/day)
Water quality parameters
Average flow rate basis
Maximum flow rate basis
7.3 to 8.1
30.85 ± 13.59b
55.3 ± 35.28b
52 to 68.5
252 to 319
646 to 802
24.05 ± 12.37b
52.00 ± 33.43b
Total suspended solids
218 to 337
Total dissolved solids
392.0 to 495.25
206.2 to 221.0
33.31 ± 15.79b
83.34 ± 57.77b
33.5 to 42.0
7.9 to 8.72
3.5 to 3.85
29.44 ± 4.80b
62.71 ± 17.22b
The pollutant loads pertaining to the drain system due to the magnitudes of grey water flow rate at maximum and average low rate basis and its difference varied time to time. The result negotiates that annual pollutant loads in terms of BOD, COD, N, P, K, TS, TDS, SS, and TC also change with the magnitudes of grey water. The variation pattern depicts fluctuation in pollutant loads pertaining to the treatment facility.
The fertigation trial of this grey water in Eucalyptus hybrid (clone K-413) revealed higher above-ground biomass (AGBM) production per tree. The data obtained from the grey water fertigation trial was found to be 34.19 kg/tree in treatment plots as compared to 25.69 kg/tree in control plots. This field observation envisages higher economic returns by fertigation due to higher biomass production per unit area as compared to control irrigation with ground water (Shankhwar and Srivastava 2014). This higher economic return was obtained in the initial 2 years of the experiment which is promising at a greater rate; in the upcoming year, more and more biomass accumulation would take place by already well-established plantations/trees. Moreover, the phytoremediation-based green technology is a solar-driven system; hence, it required a higher rate of water in the summer season due to transpiration loss which reveals the higher potential of grey water remediation in summer season.
Test of significance
Interpretation of grey water data recorded on hourly and seasonal basis were analyzed statistically using ANOVA to determine the variation at 0.05, 0.01, and 0.001 levels of significance and f-calculated values were found to be 16.45 and 10.55, respectively. P values for grey water data recorded on hourly and seasonal basis were calculated about 1.58 and 3.12, respectively; however, critical difference values were found about 1.86 and 6.55, respectively. In a nutshell, a significant variation among hourly and seasonal basis of grey water generation was recorded (Table 1).
The results concluded that the pollutant loading explicitly varied along with the magnitude of grey water. The pollutant load was found maximum in the summer season. The bioefficacy of phytoremediation-based SRICPS is also found to be at its maximum value in the summer season. SRICPS is socially accepted, economically viable, and even provides economic returns with higher grey water recycling potential. SRICPS-based eco-friendly green treatment system is compatible with fluctuating pollutant loads of grey water. Hence, it is found to be the best-suited green technology for mitigating the grey water pollutant loads. The long-term study about the mechanism of tree against various pollutants at different concentrations still needs to be explored.
This research was conducted in the framework of the RCUK-DST India Science Bridge, Bioenregy: Technology and Business Solutions for the UK and India, and authors extend special thanks to Dr. P.K. Sen, Department of Applied Mechanics, IIT Delhi; Dr. Padma Vasudevan, Retd. Professor, Centre for Rural Development and Technology, IIT Delhi, India; and Dr. Philip Davies, Aston University, Birmingham, UK for their technical support. The senior author of the manuscript extends their thankfulness to the University Grant Commission, Government of India, for providing financial support during the PhD research work.
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