Migration and transformation of nitrogen in a HRAP treating domestic wastewater in rural area
高效藻类塘对农村生活污水的处理及氮的迁移转化

Abstract:The migration and transformation of nitrogen was studied in a high-rate algal pond (HRAP) treating domestic wastewater. Total nitrogen varied from 17.23 to 133.2 mg/L while ammonia ranged from 1.85 to 108.3 mg/L in domestic wastewater. At HRT of 8 days, the annual average removal efficiency for TN and ammonia were 29.4% and 91.6%, respectively in the two-stage HRAP. The treatment performance ranked in a descending order as follows: summer, autumn, spring, winter. The major mechanism for the migration and transformation of nitrogen in HRAP were nitrification, assimilation by algae and others such as ammonia evaporation. Nitrification contributed to more than 50% of ammonia removal. Despite the possibility, the contribution of ammonia precipitation was negligible in HRAP. The total nitrogen was mainly removed through assimilation into particular organics and subsequent separation. The contribution of ammonia evaporation to total nitrogen removal was marginal. The overall removal of TN can be improved by recycling some treated effluent to the upstream septic tank or by upgrading a polishing hydrophyte pond.