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1.Reuse of treated sewage in Delhi city: Microbial evaluation of STPs and reuse options
Priyanka Jamwala, Atul K. Mittal
This paper published in the journal Resources, Conservation and Recycling argues that the microbiological quality of the treated wastewater is an important parameter for its reuse. The data on the Fecal Coliform (FC) and Fecal Streptococcus (FS) at different stages of treatment in the Sewage Treatment Plants (STPs) in Delhi watershed is not available, therefore in the present study microbial profiling of STPs was carried out to assess the effluent quality for present and future reuse options. This study further evaluates the water quality profiles at different stages of treatment for l6 STPs in Delhi city. These STPs are based on conventional Activated Sludge Process (ASP), extended aeration, physical, chemical and bio- logical treatment (BIOFORE), Trickling Filter and Oxidation Pond. The primary effluent quality produced from most of the STPs was suitable for Soil Aquifer Treatment (SAT). Extended Hydraulic Retention Time (HRT) as a result of low inflow to the STPs was responsible for high turbidity, COD and BOD5 removal. Conventional ASP based STPs achieved 1.66 log FC and 1.06 log FS removal. STPs with extended aeration treatment process produced better quality effluent with maximum 4 log order reduction in FC and FS lev- els. “Kondli” and “Nilothi” STPs employing ASP, produced better quality secondary effluent as compared to other STPs based on similar treatment process. Oxidation Pond based STPs showed better FC and FS removals, whereas good physiochemical quality was achieved during the first half of the treatment.
Based upon physical, chemical and microbiological removal efficiencies, actual integrated efficiency (IEa) of each STP was determined to evaluate its suitability for reuse for irrigation purposes. Except “Mehrauli” and “Oxidation Pond”, effluents from all other STPs require tertiary treatment for further reuse. Possible reuse options, depending upon the geographical location, proximity of facilities of potential users based on the beneficial uses, and sub-soil types, etc. for the Delhi city have been investigated, which include artificial groundwater recharge, aquaculture, horticulture and industrial uses such as floor washing, boiler feed, and cooling towers, etc.
A copy of the paper can be downloaded from below:
2 .Point and non-point microbial source pollution: A case study of Delhi
Priyanka Jamwal, Atul K. Mittal, Jean-Marie Mouchel
This paper published in the journal Physics and Chemistry of the Earth identifies major point and non-point sources of microbial pollution during dry and wet weather in Delhi watershed which is the first prerequisite for planning and management of water quality of the river Yamuna. Fecal coliforms (FC) and fecal streptococci (FS) levels were determined from two types of sources – point source (effluent from sewage treatment plants) and non-point source (storm- water runoff during dry and wet weather). FC and FS levels in the river Yamuna were also monitored, which is an ultimate sink for all microbial loads in Delhi watershed.
Effluent from sewage treatment plants (STPs) employing different treatment technologies were evalu- ated. FC and FS levels greater than the effluent discharge standard (1000 MPN/100 ml) were observed in the effluents from all STPs except ‘‘oxidation pond Timarpur”. This study also involved field program for characterization of urban runoff from different land-uses. Results indicated that the microbial quality of urban runoff produced during wet weather from different land-uses was similar to that of raw sewage. Sewage overflows along with human and animal sources were responsible for high FC and FS levels in the runoff samples.
Wet weather FC and FS levels in river Yamuna were higher as compared to the dry weather levels sug- gesting that dilution of the river water during wet weather does not affect its microbiological quality. Thus on the basis of this study it was found that urban runoff also contributes to the microbial quality of the river Yamuna.
A copy of the paper can be downloaded from below: