Effects of beneficial microorganisms on nutrient removal and excess sludge production in an anaerobic-anoxic/oxic (A2O) process for municipal wastewater treatment

Abstract

The performances of anaerobic-anoxic-oxic processes with (A²O-B) and without (A²O-C) beneficial microorganisms were compared to provide valuable insights on how they are affected by changes in the microbial biomass and community composition. Although the A²O-B process showed lower concentrations of mixed liquor suspended solids and mixed liquor volatile suspended solids than the A²O-C process under identical operating conditions, the A²O-B process was more effective for the removal of organic materials and nutrients compared with the A²O-C process. Furthermore, the compressibility and settleability of the activated sludge were significantly better in the A²O-B process than in the A²O-C process due to the enhanced decomposition of extracellular polymeric substances. These results indicated that the inoculation of beneficial microorganisms may increase the proportions of microorganisms in relation to the removal of organic materials, nutrients (i.e., Zoogloea, Dechloromonas, Nitrospira, and Nitrosomonas) and the reduction of the excess sludge (i.e., Proteobacteria and Bacteroidetes).

Keywords: Beneficial microorganisms; Excess sludge reduction; Microbial community; Nutrient removal; Wastewater treatment.