Study on the action of extracellular polymeric substances (EPS) in biological phosphorus removal from wastewater

The mechanisms of biological removal of phosphorus are discussed and the influence of extracellular polymeric substances (EPS) is investigated. EPS plays an important role in phosphorus removal by storing phosphorus. During an alternating anaerobic-aerobic process, a periodic variation was observed. The phosphorus content increased under aerobic conditions but decreased under the anaerobic conditions. Approximately 82% of P in the sludge was absorbed by the poly-phosphate accumulating organisms (PAOs) and the remaining 18% were enriched in the EPS. During a cycle, approximately 84.3% of the reduced phosphorus in the substrate was absorbed by the PAOs while 15.7% of it was stored in the EPS. The removal of phosphorus by EPS was positively correlated with the EPS content. The sludge retention time (SRT) affected the content of EPS and hence its phosphorus removal ability. Higher SRT resulted in higher EPS and higher phosphorus content. Phosphorus loads showed marginal impact on phosphorus removal.