Treatment of Polluted Urban Surface Waters by Sponge Based Aerobic Biofilm Reactor: Purification Performances and Resilience

Abstract

Surface waters are suffering continuous discharging of pollutions, and low DO and black-odorous were easily formed, especially in those slow-flowing urban lakes and enclosed small ponds. In-situ treatment by artificial aeration or water cycling with a combination of polyurethane sponge as biofilm carriers can disentangle this situation without any land occupation. Long-term continuous experiments (187 days) showed that indigenous microorganisms in urban surface waters could form biofilms in the novel style of sponge-based aerobic biofilm reactors (SABRs). In urban lake waters treatment, the purification performances of SABRs were stable and resilient as the NH4+-N and NO2−-N removals were steady, even facing the abrupt increase of NH4+-N and NO2−-N concentrations in influent. Enhancing the polyurethane sponge filling ratios in SABRs can reduce DO but did not affect NH4+-N removal. SABRs were also able to treat enclosed surface waters or black-odorous waterbodies. Combined SABRs with water cycling, NH4+-N removal time was shorter than the time needed by water cycling when biodegradable organic matter was not present. The massive biodegradable organic matter could inhibit nitrification and prolong the purification time. Further results showed that organic matter could be used as carbon sources to eliminate the produced NO3−-N in SABRs. Therefore, the developed new bioreactor could act as one effective way for treating N-polluted urban surface waters.