Influence of varying COD and total phosphorus loading on EBPR performed in aerobic baffled reactor using dried powdered sludge

Abstract

Previous research has indicated that enhanced biological phosphorus removal (EBPR) can be achieved under fully aerobic conditions. In this study, EBPR was performed for 384days using dried powdered sludge in an aerobic baffled reactor fed with medium strength (COD ∼400–500mg/L) and then high strength (COD ∼900–1000mg/L) synthetic wastewater. Total phosphorus (TP) concentration in the feed was varied between 1.4–40mg/L. The results showed that for medium strength influent, TP removal efficiency was over 90% up to 20mg/L of influent TP but decreased to 68% and 33% at 30 and 40mg/L of influent TP, respectively. For high strength influent, TP metabolism weakened and EBPR activity inhibited as biomass TP content was reduced. Experimental results also showed that TP release levels increased with biomass TP content and TP uptake occurred in the presence of carbon source. COD and NH4+-N removal efficiencies largely remained unaffected by different TP concentrations. TP removal efficiency was affected by its own concentration. 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 release of extracellular enzymes by microbes due to the addition of dried powdered sludge. Based on tracer studies, dead space in AeBR was found to range from 12.8 to 19.3%. The flow pattern in the AeBR was classified as an intermediate between plug and completely mixed flows. This study could provide an alternative for stable aerobic EBPR for medium strength wastewater.