Pilot-scale anoxic/aerobic biofilter system combined with chemical precipitation for tertiary treatment of wastewater

Abstract

In this study, a pilot-scale anoxic/aerobic biofilter system combined with chemical precipitation was devised and applied for the tertiary treatment of nitrogen, and post-treatment of phosphorus and residual organics in effluent from existing wastewater treatment facilities. When the system operated under a system hydraulic retention time (HRT) of 5.98 h, nitrified effluent recirculation ratio of 0.5, average methanol-supplement concentration of 23.2 mg/L, and average aluminum-sulfate concentration of 2.37 mg/L, the average concentration of BOD5, COD, SS, TN, and TP in the system effluent were 3.3, 10.4, 4.2, 6.1, and 0.43 mg/L, respectively. Despite the shorter HRT of 1.35 h in the anoxic filter packed with media, noticeable denitrification was achieved rapidly. A perfect nitrification rate was achieved and no clear deterioration in performance by chemical addition was observed. Thus, the system achieved not only outstanding nitrogen-removal performance, but also the additional removal of residual organics and phosphorus.