PERFORMANCE EVALUATION OF SEWAGE TREATMENT PLANTS

Abstract

Sewage is correctly the subset of wastewater that is contaminated with feces or urine, but is often used to mean any waste water. "Sewage" includes domestic, municipal, or industrial liquid waste products disposed of, usually through a pipe or sewer. Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater and household sewage, both runoff (effluents) and domestic. It includes physical, chemical, and biological processes to remove physical, chemical and biological contaminants. Since 1985, more than 70 sewage treatment plants have been constructed under the GAP and Yamuna Action Plan (YAP). These plants are based on a range of technologies involving varying levels of mechanization, energy inputs, land requirement, skilled manpower, etc. In the early stages, the selection of technology was based on past experience and its perceived performance efficiency. Moreover, at different stages of these Action Plans a number of technologies have been tried out on pilot scale and some of them have been scaled up for larger capacity plants. Over the last 20 years a considerable experience and expertise has been developed within the country in this sector. However, the level of performance of these plants with regard to effluent quality, energy consumption, process stability, resource recovery, capital and O&M costs, etc. There are many Sewage Treatment technologies available for the treatment and reuse of sewage in India. Sometimes, it is difficult to select a technology that is appropriate for the desired treatment in the specific region such as rural, urban or metropolitan area. The important factors affecting the selection of STP technology are the volume of daily flow, sewage characteristics, degree of treatment needed, disposal of the effluent, area of land required for the plant, capital cost of installation, power required for the treatment, annual operation and maintenance cost. Actual performance of the STP can differ from that of design mainly due to differences in sewage characteristics & local conditions. Thus knowing actual performance and capacity of the STP becomes very important. The current study is an attempt in this direction. After evaluating the performance of different technologies based sewage treatment plant in term of different parameter, From life cycle cost analysis it is conclude that the Waste Stabilization Pond is the most economical and cost effective technology to treat sewage where the cost of land is low i.e. approx. in the range upto Rs. 200 Lacs per ha. In WSP daily power requirement is also very low so in villages where power is not available WSP is only suitable. Where land cost is high and land is not available the UASB and ASP both are suitable. In ASP treated effluent quality is best among UASB & WSP. The average BOD & TSS removal efficiency of ASP are more than 90% which is very high in comparison to UASB & WSP. Where land cost is high, land scarcity areas where huge area is not available, ASP are found to be economical in order, a suitable option in Mega & Metropolitan areas. The revenue generation potential from UASB with FPU is the highest among ASP & WSP, its projected energy production capacity of 56 MLD STP is 11.08 MWh/day which very high in comparison to ASP & WSP, the cost of electricity saving per MLD ASP STP is 072 lakhs/year and the UASB STP is 2.88 lakhs/year which very high in comparison to ASP, in WSP energy generation through biogas is not available.