Abstract
Appropriate low-cost treatment technologies are a prerequisite for sound management of natural water resources against pollution in developing countries. Among the existing technologies available, UASB is found to be economically viable for India when considering all factors including operation and maintenance cost and treatment efficiency. However, this technology suffers setbacks in meeting the effluent guidelines prescribed by the government of India. Post treatment is supplemental to this process to meet the effluent standards in terms of removal of organic matter, suspended solids, pathogens and nutrients. Recent stringent effluent guidelines notified by the Ministry of Environment, Forests and Climate Change, Government of India has further reduced the limits of BOD by 3 times, COD and TSS by 5 times, NH4-N and total Nitrogen by 10 times as compared to the previous guidelines. Fecal Coliforms has been specified as <100MPN/100mL. In this paper, the present scenario of UASB based STPs and their role in river conservation is reviewed against the backdrop of stringent effluent guidelines. The minimum removal rates of BOD, COD and TSS in these plants are around 42 – 44% and the average removal rates are reported to be 66%, 61% and 65% respectively. The enhanced removal of BOD (97%), COD (98%) and TSS has been reported in STPs in conjunction with post treatment facilities such as facultative aerated lagoons, aeration tanks and polishing ponds.
Highlights
India is the second most populous country in the world with an estimated population of over 1.3 billion during 2017
The maximum BOD and COD removal efficiency has been found in Upflow Anaerobic Sludge Blanket (UASB) based Sewage Treatment Plants (STPs) in Hyderabad. 97% BOD removal efficiency is reported from 30MLD Nallacheruvu plant with 9hrs HRT in UASB reactor followed by 1 day HRT in facultative aerated lagoons
Minimum BOD removal efficiency of 44% is reported from 14MLD STP in Jaganpur, Agra with UASB technology followed by Polishing Ponds for post treatment whereas 56MLD STP in Ghaziabad has a minimum COD removal efficiency of 42%
Summary
India is the second most populous country in the world with an estimated population of over 1.3 billion during 2017. According to CPCB, the estimated sewage generation in the country during 2015 was 61,948Million Litres per Day (MLD) against available treatment capacity of 23,277 MLD. There are 816 Sewage Treatment Plants (STPs) in the country out of which 522 are operational, 79 are non-operational, 145 are under construction and 70 are under planning stage. The National River Conservation Directorate (NRCD) which functions under MOEF & CC provides assistance to various State Governments for implementing the River Action Plans in 29 identified grossly polluted stretches of various rivers of India under the National River Conservation Plan (NRCP). The standards for FeCal Coliform may not be applied for use of treated sewage in industrial purposes
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