Enhanced biological phosphorus removal in aerated stirred tank reactor using aerobic bacterial consortium

Recently, some studies in the field of enhanced biological phosphorus removal (EBPR) have reported that anaerobic zone is not mandatory and EBPR could be accomplished under fully aerobic conditions. This study investigated the EBPR performance of a bacterial consortium in a fully aerobic continuous stirred tank reactor (CSTR) fed with synthetic wastewater containing molasses as the sole carbon source. Total phosphorus (TP) concentration in the feed was varied between 1.4 and 40 mg/L. The results showed that TP removal efficiency was over 90% up to 20 mg/L of influent TP concentration but decreased to 62% and 30% at 30 and 40 mg/L of influent TP concentrations, respectively. TP removal efficiency was affected more by its own concentration in the influent. COD and NH4+-N removal efficiencies largely remained unaffected by different TP concentrations. Further investigations showed that TP was transformed to intracellular storage of polyphosphate (poly-P) with single stage aerobic process. The primarily reason for TP removal was the synergistic activity among the individual strains of phosphate solubilizing and accumulating microbes. Based on tracer studies, dead space in CSTR was found to range from 1.5-2.5%. The flow pattern in the CSTR was classified as completely mixed.