Interaction of denitrification and P removal in anoxic P removal systems

This paper compares municipal wastewater (MWW) as a carbon source with other volatile fatty acids (VFAs) such as acetic acid, propionic acid and butyric acid in biological nutrient removal (BNR) processes. Biomass specific denitrification rates (SDNR) using acetic acid, butyric acid, propionic acid, MWW and primary effluent from batch studies were 107.2, 77.1, 37.9, 31.1 and 30.0 mg NO3–N/g VSS·d respectively. SDNR for acetic acid derived from batch experiments and respirometric studies were identical while for the MWW the discrepancy between the two methods was about 31%. Phosphorus (P) release was observed only after nitrate concentration dropped to < 1 mg/L. The extent of P release and subsequent uptake was highest with acetic acid and lowest with propionic acid. P release correlated negatively with nitrate uptake under anaerobic conditions.