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

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 ach-ieved 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.

Automated summary

This study introduces a novel post-treatment process for sewage treatment systems, the down-flow hanging sponge (DHS) reactor. Through a pilot-scale experiment, it is demonstrated that the DHS reactor can effectively remove suspended solids, biochemical oxygen demand, and ammonium nitrogen in sewage, as well as reduce the concentration of fecal indicator bacterium Escherichia coli and potentially pathogenic bacterial group Arcobacter spp. under relatively short hydraulic retention times (HRT).