Performance comparison of biofilm and suspended sludge from a sequencing batch biofilm reactor treating mariculture wastewater under oxytetracycline stress

Abstract

ABSTRACTThe performance, extracellular polymeric substances (EPS) and microbial community of a sequencing batch biofilm reactor (SBBR) were investigated in treating mariculture wastewater under oxytetracycline stress. The chemical oxygen demand and –N removal efficiencies of the SBBR decreased with the increase of oxytetracycline concentration, and no obvious –N and –N accumulation in the effluent appeared at less than 10 mg L−1 oxytetracycline. The specific oxygen utilization rate of the suspended sludge was more than that of the biofilm at different oxytetracycline concentrations. The specific ammonium oxidation rate (SAOR) of the biofilm was more easily affected by oxytetracycline than that of the suspended sludge, whereas the effect of oxytetracycline on the specific nitrite oxidation rate (SNOR) of the biofilm was less than that of the suspended sludge. The specific nitrate reduction rate of both the biofilm and suspended sludge was higher than the sum of the SAOR and SNOR at different oxytetracycline concentrations. The protein and polysaccharide contents in the EPS of the biofilm and suspended sludge increased with the increase of oxytetracycline concentration. The appearance of oxytetracycline in the influent could affect the chemical composition of the loosely bound EPS and tightly bound EPS. The amino, carboxyl and hydroxyl groups might be involved with interaction between EPS and oxytetracycline. The denaturing gradient gel electrophoresis profiles indicated that the variation of oxytetracycline concentration in the influent could affect the microbial communities of both the biofilm and suspended sludge.