Study On EBPR By Using Food Waste Hydrolyte As External Carbon Source

Enhanced biological phosphorus removal (EBPR) process plays an important role in the control of eutrophication through reducing phosphorus discharge from municipal sewage treatment plants. However, the performance of EBPR was frequently confronted by inadequacy of short-chain organic acids present in municipal sewage. The objective of the present research was to explore the feasibility of EBPR using food waste hydrolyte as external carbon source.In the present study EBPR was first initiated in four aerobic-anaerobic SBRs which were fed with acetic acid, propionic acid, butyric acid and lactic acid as sole influent carbon source. Excellent phosphorus removing efficiencies were achieved in all SBRs after an acclimation period, but the length of acclimation period varied with different carbon sources. For example, EBPR could be achieved after an accilimation period of 8 d and 11 d in SBRs fed with acetic acid and propionic acid as the influent carbon source, while a longer period of 18 days or 30 days were required for SBRs fed with butyric acid and lactic acid as the influent carbon source. EBPR was also successfully achieved in an aerobic-anaerobic SBRs fed with a mixture of acetic, propionic and lactic acids as influent carbon sources after a 9-day acclimation period. Maximum phosphorus loads suitable for SBRs fed with acetic acid, propionic acid, butyric acid, lactic acid and mixed acids as influent carbon source were 24 mg/L% 18 mg/L、18 mg/L、12 mg/L and 18 mg/L, respectively. EBPR sludges obtained in SBRs with different carbon sources all showed characteristic metabolic behaviors typical to PAOs.Effects of influent pH and temperature on the performance of EBPR process were investigated during a long-term operation period. The results showed that high phosphorus removal efficiencies of ≥99% could be maintained in the influent pH range of 6.5-8.5 whereas it showed a significant decrease in phosphorus removal efficiencies to around 60%. Process stability was also affected by temperature. Phosphorus removal efficiency maintained to be 99% when the reactor was operated at 22～28℃. However, when the temperature was raised to 33℃ phosphorus removal efficiency decreased significantly to 51% after 5 days of operation, indicating a deterioration of the EBPR process.EBPR-associated bacterial community was analyzed through PCR-DGGE method. The results showed there were significant changes in the microbial community between the seed sludge and EBPR sludges acclimated in SBRs fed with various single organic acid or mixed acids as the influent carbon source. DGGE profiles also differed between various EBPR sludges acclimated with different carbon source. Microbial community was also influenced by influent pH values. When influent pH value increased from 7.5 to 8.5 a significant decrease in the number of DGGE bands was observed reflecting a decrease in the diversity of bacterial community. In contrast there was a significant increase in the number of DGGE bands when influent pH value decreased from 6.5 to 6.0 and this implied more severe competition occurred between PAOs and other bacterial present in this artificial microbial ecological system.