THE EFFECT OF COD/TP RATIO ON INTRACELLULAR STORAGE MATERIALS, SYSTEM PERFORMANCE AND KINETIC PARAMETERS IN A BNR SYSTEM

A UCT type pilot plant fed with synthetic wastewater was operated with influent COD/TP ratios of 18, 12 and 8 to investigate the role of intracellular storage products on EBPR mechanisms. Acetate was the sole carbon source and other nutrients were provided in excess during plant operation at an SRT value of 10 days and at 200C temperature. COD utilization, P-release and –uptake, PHA and glycogen storage and utilization of the system were monitored. The steady state data showed that PHA storage, glycogen production and system performance were influenced by the COD/TP ratio. System P removal performance decreased as COD/TP ratio decreased and some deterioration in overall performance occurred at the lowest COD/TP ratio. Very good stoichiometry was obtained between both organic storage and its utilization, and P release and P uptake. Glycogen production and P-uptake were observed in the absence of extracellular organics and in the presence of NO3-N. The consumption and production of glycogen in anaerobic and aerobic reactors favored the Mino model over the Comeau/Wentzel model for EBPR. At the lowest COD loading, glycogen was not generated and energy obtained through PHA utilization apparently was used for maintenance energy needs.