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Content and Species of Extracellular Phosphorus
in Activated Sludge of Biological Phosphorus
Removal Systems

Extracellular polymeric substances (EPS) contain a large amount of phosphorus, but the content of extracellular phosphorus in activated sludge and the decomposition of extracellular polyphosphate (polyP) in extraction process is still unclear. In this study, the extraction efficiencies of extracellular phosphorus using sonication, cation exchange resin (CER) and sonication-CER methods were investigated and compared, taking the aerobic sludge from four lab-scale A/O-SBR reactors at different temperatures and in different matrices as the objects. The sonication-CER method was an efficient and reliable method for extracting EPS and extracellular phosphorus, which could avoid the decomposition of extracellular polyP and the massive lysis of a bacterial cell. Importantly, utilizing CER with two successive alkaline washes was a key factor for efficiently extracting extracellular phosphorus. The extracellular phosphorus content of aerobic-activated sludge in 4 A/O-SBR reactors was 28.17~73.13 mg P/g VSS, accounting for 59.6~74.1% TPsludge. Thereby phosphorus of sludge floc was mainly located in EPS. Furthermore, polyP was the main species of extracellular phosphorus in EBPR sludge, which mainly existed in the inner layer of sludge floc. There was a close relationship between the content and species of extracellular phosphorus and the EBPR performance of activated sludge.