Hydrolysis and biological release mechanisms of phosphorus from phosphorus-rich waste activated sludge during anaerobic digestion

The release mechanisms of phosphorus from phosphorus-rich waste activated sludge are discussed based on anaerobic digestion experiments.The sludge used in this study was obtained from a sewage treatment plant in which the A/O process was used.The results indicated that the ratio of soluble orthophosphates(SOP) release to polyhydroxy-alkanonates(PHA) production obtained from anaerobic digestion experiments of waste activated sludge was higher than that from the anaerobic process of activated sludge in an EBPR,which suggested that hydrolysis is a contributing mechanism to phosphorus release.The ratio of PHA production to consumed hepatin in waste activated sludge was less than that in enhanced biological phosphorus removal(EBPR) activated sludge,which suggested that the hepatin was consumed to not only release phosphorus but also for other reasons.The presence of a bacterial inhibitor was a disadvantage to both the hydrolysis and biological release mechanisms in the anaerobic digestion system.