Study On Aerobic Granular Sludge Culture And Its Storage Stability In Phenol Solution

Aerobic granular sludge（AGS）has dense structure,excellent settling performance,high impact resistance and diverse microbial populations.Therefore,it has a broad application prospect in the field of wastewater treatment.However,the instability of AGS obtained from different culture conditions,AGS is easy to disintegrate and inactivate during long-term storage,and the long recovery time of AGS after storage limit the application and promotion of AGS technology in practical engineering.Therefore,the whole life cycle of AGS was systematically observed and studied,including AGS culture（formation）,storage and activity recovery after storage,which can provide a theoretical basis for the cultivation technology of AGS and a valuable reference for the selection of AGS storage methods.The main research and results are as follows:（1）AGS was cultivated in sequencing batch reactor（SBR）by adjusting the concentration of oxygen consuming organic pollutants（in terms of COD）,surface rising gas velocity and sludge settling time.Glucose and sodium acetate were used as mixed carbon sources.The results showed that AGS culture was successful on the 110th day,the particle size mainly distributed in the range of 1.43～2.26mm,the sludge volume index(SVI₃₀)was28m L/g,the settling velocity was 94m/h,and the ratio of sludge volatile components（MLVSS/MLSS）was 0.72.The removal rates of COD,total nitrogen（TN）and total phosphorus（TP）by AGS reached 95%,80%and 70%,respectively.（2）The change pattern of extracelluar polymeric substances（EPS）during sludge granulation and the relationship between EPS and sludge surface characteristics was studied.The difference of EPS components between AGS and inoculated sludge was analyzed.The results showed that the protein（PN）content in EPS increased from 13.98mg/g to 41.86mg/g and the polysaccharide（PS）content was maintained at 15.88～26.74mg/g during aerobic sludge granulation.The PN content was negatively correlated with zeta potential and positively correlated with relative hydrophobicity of sludge surface（RH）.The correlation coefficients（r）were 0.950 and 0.934,respectively.Compared with inoculated sludge,the fluorescence intensity of proteins representing tyrosine and tryptophan-like proteins was enhanced in the EPS of AGS,and aromatic proteins and fulvic acid-like substances as well as proteins containing N—H functional groups were present.（3）At room temperature,AGS was stored in phenol solutions with concentrations of 30,60,100,150,200 and 300mg/L and distilled water,respectively.The effects of different concentrations of phenol solutions on the stability of AGS were investigated,and the best storage method for maintaining the stability of AGS was determined.It was found that AGS in 60mg/L phenol solution had better granular structure and compactness after 150 days storage,it released less contaminants into the storage solution.The abundance of dominant bacteria（Flavobacteria,Alphaproteobacteria and Actinobacteria）in AGS decreased,while that of Clostridia increased.Depending on the length of storage time,different concentrations of phenol solutions were selected for storage of AGS.For short-term（1～70d）and long-term（70～150d）storage of AGS,30mg/L and 60mg/L phenol solution were selected as storage solution respectively,which was beneficial to maintain the microbial activity of AGS.（4）The activity of AGS stored in 60mg/L phenol solution was recovered.The results showed that the structure integrity and microbial activity of AGS could be restored to the level before storage after 28d of re-cultivation.During the recovery period,AGS had experienced an evolution from"fragmentation"to"remodeling".After recovery,SVI₃₀and SVI₅of AGS were 26.1 and 27.6m L/g,respectively,MLSS and MLVSS were 16903 and12001mg/L,respectively,MLVSS/MLSS was 0.71,and dehydrogenase activity（DHA）was71.36μg TF/（g·h）.The removal rates of COD,TP and TN reached 97.34%,89.88%and64.37%respectively.