TECHNO – ECONOMIC EVALUATION OF SEWAGE TREATMENT TECHNOLOGIES IN INDIA

Abstract

In last two decades, large number of sewage treatment technologies got implemented in our country. Some of them are very good from point of view of treatment efficiency, while some others are low cost but unable to meet effluent standards. India is a developing country with lot of resource constraints, so performance levels can not be the sole criteria for selection of sewage treatment technology for any specific site. We have to give due weightage to life cycle cost and local limitations affecting operation & maintenance. There can also be constraints on account of availability of adequate land particularly in big cities. According to the report of CPCB the estimated sewage generation from class1 cities and class 2 towns is 38254.82MLD, out of which only 17787.38MLD which is 35% is being treated and the remaining is disposed of into water bodies without any treatment. The manual on sewerage and sewage treatment published by the ministry in 1993 lays emphasis on conventional sewage treatment technologies such as ASP, WSP etc. but over the last two decades many new technologies have emerged . These technologies which are being used in other parts of the world have not been deployed in India on a large scale. Therefore their techno-economic viability under Indian conditions needs to be proven. Each of these technologies has its own merits and demerits. The following treatment technologies though these have been randomly tried out so far, need to be investigated under Indian conditions to arrive at their techno economic viability. As per the compendium of sewage treatment technologies issued by the national river conservation directorate (NRCD), ministry of environment and forest, published in 2009, the cost aspects based on capital cost, O&M cost, reinvestment cost, energy and land cost based on data of STPs in the Ganga river basin and elsewhere in India indicates that unlined WSPs has the lowest treatment cost but the highest land requirements. The conventional ASPs ha moderate treatment cost and moderate land requirement. This study aims to develop a methodology for selecting most appropriate technology suitable for a particular location taking into account all the constraints specific to the site. No universal solution to be adopted for different sites. Current decision support tools for selection of sewage treatment alternative focus primarily on effluent quality, treatment efficiency& indirectly the environmental consequences of receiving water bodies For the purpose of the study, performance data of 21 STPs (spread over the length and breadth of the country) was analysed. The initial capital cost / operation &maintenance cost per unit MLD incurred in the past for the different STPs mentioned in this report were converted to a common base year 2011. For computation of above, Cost Inflation Indices were used. It is necessary to compute the above costing data of all STPs for same year because construction year of all STPs are different