BIOLOGICAL TREATMENT OF DOMESTIC WASTEWATER FOR AQUACULTURE

Domestic sewage contains important nutrients for the growth of plants and is used for aquaculture in several parts of the world. The campus of Indian Institute of Technology (IIT), Kharagpur generates 14.29 lakh liters day-1 of sewage. Only 17 % of the total sewage is going to the existing ponds while the remaining 83 % is wasted due to leakage in the underground drainage system. There is a possibility of pollution of soil and ground water around the IIT, Kharagpur campus. A study was initiated to assess the present situation and to design a sewage-fed aquaculture farm on the campus. The area was physically surveyed, soil samples and meteorological data collected and analysed. Based on the collected information, a model of sewage-fed aquaculture farm was designed. This would utilize the nutrients present in the sewage and would reduce the risk of pollution of soil and ground water in the area. The data collected from the proposed sewage treatment aquaculture farm show that the desired dissolved oxygen level (> 5 mg/l) was achieved on 4th day from 1 mg/l, COD concentration (< 50 mg/l) on 6th day from 350 mg/l, TSS (80 mg/l) on 5th day from 350 mg/l, BOD concentration (<20 mg/l) on 6th day from 180 mg/l and ammonium-nitrogen concentration (0.2-3 mg/l) was achieved on 5th day. Economic analysis of the model sewage-fed aquaculture farm shows that there will be an annual profit of Rs. 766,014/- on an annual investment of Rs. 677,986/- (excluding cost of land and sewage water). The farm will produce 35,000 kg of fish per year and will also generate employment of 2,545 men-days per year