A pilot-scale study of a down-flow hanging sponge reactor as a post-treatment for domestic wastewater treatment system at short hydraulic retention times

Abstract

This study proposes a down-flow hanging sponge (DHS) reactor as a post-treatment process for sewage treatment systems. A pilot-scale DHS reactor was operated over 1000 days under relatively short hydraulic retention times (HRT) of 1–3 h to evaluate its effectiveness as a post-treatment technology. The DHS reactor consistently achieved superior effluent water quality with total suspended solid <10 mg/L, biochemical oxygen demand < 10 mg/L, and ammonium nitrogen < 5 mg/L. The effective removals (> 2-log10 reduction) of Escherichia coli, a fecal contaminant indicator, and Arcobacter spp., a potentially pathogenic bacterial group, were achieved. The treatment performance was compared with the previous operation treating raw domestic wastewater under long HRTs of 4 and 5 h. As a result, the DHS reactor under short HRT conditions showed advantages for biological oxidation and fecal contaminant removal. These results indicate that the DHS reactor could be a compact post-treatment technology.