Performance evaluation of a fixed film 0.4 MLD Sewage Treatment Plant

Abstract

The salient features and performance evaluation of a high rate biomethanation fixed film 0.4 MLD Sewage Treatment Plant installed at RRL Bhubaneswar under UNDP-Global Environment Facility (GEF) Program is discussed. The bio-reactors are packed with high surface area to volume ratio PVC pal rings as fixed film to achieve high mean cell residence time (MCRT). The above plant can serve nearly 3000 people to treat 400 m(3) of sewage to produce 15-20 m(3) biogas per day with methane content varying in the range of 65.5 to 83.2%. Since not more than 240 m(3) of sewage per day was available, the plant could be tested upto 60% capacity. The HRT of the sewage is about 1.5 day. Although the COD reduction varied between of 71.18 to 81.48%, an average of 75.97% could be achieved over the entire operating range of the system. The biogas generated on the other hand was found to be 0.265 m(3)/kg of COD reduced and 0.057 m(3)/m(3) of the sewage fed to the reactor. The performance of the plant can be very well judged by the fact that the suspended solids in the effluent although varied in between 52-93 mg/l, it had an average of 72.72 mg/l which is well within the stipulated standard of the State Pollution Control Board. The biogas produced is being utilised not only for illuminating the plant premises using biogas lamps but also being supplied to a cafeteria located about 180 m away from the plant for cooking. Taking 20 years as the life of the plant, the capital and the operating cost per cubic metre of biogas produced has been found as Rs. 41.97 or $ 0.96 and Rs. 15.12 or $ 0.347 respectively while the ratio of energy output to energy input is 2.07.