The PEMMC process for land-limited small wastewater-treatment plants

Abstract

In order to develop a suitable biological-treatment unit component for a prefabricated small wastewater-treatment package plant, a packed-entrapped-mixed microbial cell (PEMMC) process was investigated for settled-screened and anaerobically treated pig wastewaters. It was found that high nitrification efficiency (95–97%) could be achieved at an HRT of 10 h for the anaerobically treated pig wastewater. For settled-screened pig wastewater, an intermittent aeration (1:1 h for aeration and non-aeration) could achieve the removal efficiency of TCOD and T-N of 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 with the conventional biological-treatment alternatives for settled domestic sewage. The land cost is lowest for the PEMMC process, but the capital cost is the highest. The net present values for settled domestic sewage (1000 people) and settled-screened pig wastewater (1000 pigs) are US$426114 and US$136248, respectively. Because of its high treatment 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.