Extraction Of Alginate From EPS And Its Effect On Sludge Performance

Extracellular polymeric substances?EPS?are extracellular polymeric substances produced by microorganisms during metabolic activities,which have a very important influence on the agglomeration,precipitation and dehydration performance of activated sludge.In addition to conventional proteins and polysaccharides,EPS also contains alginate?ALE?,which occupies a large proportion.Alginate easily forms gels with divalent and higher metal ions,which may play an important role in the agglomeration,sedimentation and dewatering performance of activated sludge.Therefore,it is of great significance to study the extraction and separation of alginate from activated sludge and biofilm and its effect on sludge performance.In this study,four types of sludge?Urban sewage treatment plant A²/O process,Landfill leachate A/O treatment process activated sludge;Urban sewage treatment plant A²/O treatment process suspended filler biofilm;Artificial water distribution of A/O granular sludge?is used as the object.The EPS and ALE in the sludge are extracted by the CER method and the Na₂CO₃ method,respectively,and the contents of each component are determined.At the same time,SV,SVI,sludge activity,and CST were measured to explore the relationship between the indicators.The main findings are as follows:?1?There are large differences in the content of alginate in different sludges.The following contents are in order:biological phosphorus removal pellet sludge?29?leachate treatment plant active sludge?29?biofilm?29?municipal wastewater treatment plant activated sludge.The content of granular sludge was the highest,reaching 172.20 mg/g VSS,while the content of activated sludge in urban sewage treatment plants was the lowest,only 82.91 mg/g VSS;the contents of leachate activated sludge and biofilm were 148.28mg/g VSS and 134.99 mg/g VSS,respectively.?2?The culture conditions of biological phosphorus removal granular sludge can easily induce microorganisms to produce higher content of ALE,but its content is still lower than that of pure aerobic granular sludge;higher COD load may be an important reason for inducing live microorganisms to produce more ALE.?3?Alginate,as an important component in extracellular polysaccharides,has an important influence on the agglomeration,sedimentation,and dewatering performance of sludge.The more alginate content in sludge EPS,the longer the corresponding capillary water absorption time?CST?,and the worse the sludge dewatering performance.However,alginate content had no significant effect on sludge oxygen consumption rate and VSS/SS.?4?By comparing the two extraction methods of one-step extraction of Na₂CO₃and two-step extraction of CER+Na₂CO₃,it is found that the CER method still has defects in the extraction of polysaccharides,especially the extraction efficiency of alginate in polysaccharides is low;in contrast,the Na₂CO₃ method can more efficiently extract alginate from the sludge.