TERTIARY TREATMENT OF CETP TREATED EFFLUENT FOR REUSE /RECYCLE AT AHMEDABAD

Abstract

The rapid pace of industrialization and urbanization have been causing unprecedented demand on water resources making availability of this commodity more and more scare. Thus, there is a great need to search for alternative sources of water to maintain the pace of development. Reuse of wastewater has emerged as a practical supplemental strategy towards achieving this objective. Reuse of municipal wastewater after treatment is common because of its uniform composition, continuous availability and easy amenability to treatment. Industries use large quantities of water and generate almost the same amount of wastewater which are heterogeneous in nature and show high degree of variation in quantity as well as quality. The treatment of industrial wastes therefore requires application of specific treatment processes to facilitate its reuse. Visualizing the future requirement of water in industries and the constraints that would be encountered due to its limited availability, it was thought fit to examine feasibility of its reuse after appropriate treatment. With the introduction of CETP for cluster of industries predominantly in small- scale group, availability of industrial wastewater in large quantities at a central point is possible whiCh in turn facilitates its treatment and possible reuse in the industrial estates itself. An operational CETP at Vatava, Ahmedabad with a design capacity of 16 MLD receives about 10 MLD of industrial waste, for treatment, to comply with the statutory requirement. The treatment sequence at the CETP comprises of neutralization, equalization, physico-chemical treatment. The treated effluent is conveyed through a pipe line and let out to the river Sabarmati after mixing with treated sewage at the municipal corporation owned sewage treatment plants. The effluent from this CETP was selected for further treatment through tertiary treatment techniques viz., physicochemical treatment, sand filtration and activated carbon adsorption in order to make it fit for reuse in the industries. The characteristics of the final effluent after tertiary treatment showed that the quality requirement for its reuse is satisfied for cooling tower (a major water consumption area in an industry and or other purposes) except TDS. TDS removal would need application of reverse osmosis, which would appreciably increase the cost. However, in a situation where no alternative sources of water are available, the reuse of wastewater will be the only option if the industry to run. Therefore further optimization of treatment techniques together with input cost of treatment must be exercised.