Nutrient removal performance and microbial characteristics of a full-scale IFAS-EBPR process treating municipal wastewater

This work describes the nutrient removal performance and microbial characteristics of a full-scale integrated fixed-film activated sludge-enhanced biological phosphorus removal (IFAS-EBPR) process for municipal wastewater treatment. The polymerase chain reaction-denaturing gradient gel electrophoresis results showed that the presence of bacteria in this process, including Nitrosomonas sp., Nitrospira sp., Nitrobacter sp., Pseudomonas sp. and Acinetobacter sp., clusters. The fluorescence in situ hybridization results implied that there were more nitrifiers and denitrifiers on the biofilm carriers than in the suspended sludge, whereas more phosphorus-accumulating organisms (PAOs) resided in the suspended sludge. With the cooperation of these functional microbial populations both on the biofilm carriers and in the suspended sludge, the chemical oxygen demand (COD), NH₄⁺-N, total nitrogen (TN) and total phosphorus (TP) removal efficiencies were maintained at 84, 97, 70 and 81%, and the effluent concentrations of them averaged 30, 1.0, 11.5 and 0.6 mg/L, which all satisfy the Chinese discharge standard (COD <50 mg/L, NH₄⁺-N <5 mg/L, TN <15 mg/L and TP <1 mg/L), respectively. Therefore, the IFAS-EBPR process is a reliable and effective process for nutrient removal.