Development of a prefabricated treatment plant for diluted pig wastewater

In order to develop a prefabricated treatment and reuse plant for diluted p ig wastewater. an entrapped-mixed-microbial-cell (EMMC) process was evaluat ed for its process performance and economic analysis. At the hydraulic rete ntion time (HRT) of 30 hrs (loading rate of 1.0 g TCOD/L/d) and intermitten t aeration of 1 hr of aeration and 1 hr of non-aeration, it was found that, by using the pretreatment of the ammonium crystallization, both the medium and large carriers were able to reduce TCOD, SCOD, and T-N by 83.51, 84.11 , and 95.10%, respectively. The EMMC unit and lime posttreatment followed b y ammonium crystallization can reduce BOD5, TCOD, SCOD, TSS, T-N, and T-P, respectively by 99.22, 93.85, 92.67, 97.73, 96.43, and 97.27%. The treated wastewater, after disinfection, is able to meet the requirements of the sta ndards issued by the USEPA for reuse of food crops. The economic analysis i ndicates that based on the process performance of the EMMC unit, a prefabri cated wastewater treatment plant for 2000 pigs has comparable net present w orth (NPW) comparing intermittent aerated biological sq-stems and less oper ation and maintenance and land requirement than conventional biological pro cesses for removal carbon and nitrogen. A farm operation of more than 2000 pigs meets the unit cost of US$4.91/pig/yr. This will minimize the problems pertaining to technical factors or considerations that heavily influence p lanning, construction and operation of a pig wastewater treatment system.