THE PEMMC PROCESS FOR LAND-LIMITED SMALL WASTE-WATER-TREATMENT PLANTS

In order to develop a suitable biological-treatment unit component for a prefabricated small wastewater-treatment package plant, a packed-en trapped-mixed microbial cell (PEMMC) process was investigated for sett led-screened and anaerobically treated pig wastewaters. It was found t hat high nitrification efficiency (95-97%) could be achieved at art HR T of 10 h for the anaerobically treated pig wastewater: For settled-sc reened pig wastewater; an intermittent aeration (I:I h for aeration an d non-aeration) could achieve the removal efficiency of TCOD and T-N o f 80.92 +/- 3.2% and 89.89 +/- 2.2%, respectively, at an HRT of 30 h. The economic analysis indicated that the PEMMC process is comparable w ith the conventional biological-treatment alternatives for settled dom estic sewage. The land cost is lowest for the PEMMC process, but the c apital cost is the highest. The net present values for settled domesti c sewage (1000 people) and settled-screened pig wastewater (1000 pigs) are US$426114 and US$136248, respectively. Because of its high treatm ent efficiency for carbon and nitrogen removals and low operation and maintenance costs, the PEMMC process is very suitable for integration into a prefabricated small, packaged plant for wastewater treatment in land-limited applications. Thus, the reuse of treated wastewater from small wastewater-treatment systems may become feasible. (C) 1997 Else vier Science Ltd.