Performance and metabolic aspects of a novel enhanced biological phosphorus removal system with intermittent feeding and alternate aeration

A novel enhanced biological phosphorus removal (EBPR) system, which combined the intermittent feeding design with an anaerobic selector, was examined using on-line oxidation reduction potential (ORP), nitrate and ammonium probes. Two experimental periods were investigated: the aerobic and anoxic phases were set at 40 and 20 minutes respectively for period I, and set at 30 and 30 minutes for period II. Chemical oxygen demand (COD), biochemical oxygen demand (BOD₅) and P removal were measured as high as 87%, 96% and 93% respectively, while total Kjeldahl nitrogen (TKN) and NH₄⁺ removal averaged 85% and 91%. Two specific denitrification rates (SDNRs), which corresponded to the consumption of the readily biodegradable and slowly biodegradable COD, were determined. SDNR-1 and SDNR-2 during period I were 0.235 and 0.059 g N g⁻¹ volatile suspended solids (VSS) d⁻¹ respectively, while the respective rates during period II were 0.105 and 0.042 g N g⁻¹ VSS d⁻¹. The specific nitrate formation and ammonium oxidizing rates were 0.076 and 0.064 g N g⁻¹ VSS d⁻¹ for period I and 0.065 and 0.081 g N g⁻¹ VSS d⁻¹ for period II respectively. The specific P release rates were 2.79 and 4.02 mg P g⁻¹ VSS h⁻¹ during period I and II, while the respective anoxic/aerobic uptake rates were 0.42 and 0.55 mg P g⁻¹ VSS h⁻¹. This is the first report on an EBPR scheme using the intermittent feeding strategy.