Performance And Microbial Characteristics Of Aerobic Granular Sludge In Response To Alternating Salinity

It is difficult to treat high-salinity wastewater effectively by traditional biological treatment.In the past few years,abundant achievements have been made on inoculation and application of aerobic granular slucdge(AGS)in treating high-salt xwastewater.Compared with conventional activated sludge,AGS has many advantages.Its good settling performance is effective to overcome the washout of biomass,and the dense and special compact structure provides a good shielding effect for microorganisms Salt concentrations generally fluctuate in wastewaters.However,the behavior of AGS in response to the stress of alternating salt condition remains unclear.In this study,we ran 6 identical sequencing batch reactors(SBRs)to explore the degradation performance and microbial characteristics of AGS under 1%,2%,4%salinity and corresponding sequentially salt fluctuation in 50%range,respectively.The results showed that the contents of polysaccharides with stable salinity of 1%,2%and 4%were 130±9,53±10,121±10mg·g-1,respectively.Under the condition of salinity fluctuation,165±8?86±12?171±10 mg·g-1.The removal rates of COD of 1%,2%and 4%were 92.7±1.5%,72.3±11.6%and 41.8±5.9%,respectively.Under the condition of salinity fluctuation,the removal rates of COD of 1%,2%and 4%were 95.1 1.5%,81.2 7.3%and 50.0 4.8%,respectively.Pearson correlation analysis showed that the microorganism used intracellular second messenger molecules bis(3'-5')-cyclic dimeric guanosine monophosphate(c-di-GMP)to regulate extracellular polymeric substance(EPS)content.Specifically,the increase of extracellular polysaccharide was conducive to the cohesive strength of the granules and carbon removal efficiency.Additionally,microbial community analysis showed that the relative abundance of c-di-GMP pathway-dependent community,especially Propionibacterium(13.6%-50.9%),was absolutely more dominant in alternating salt condition.The prediction of PICRUSt function indicates that the abundance of alginate anabolism enzymes under alternating salinity is significantly higher than that under the stable salinity.The results can provide reference for the application of aerobic granular sludge technology in the treatment of high salt wastewater.