Adsorption Of Perfluorooctane Sulfonate(PFOS) On Activated Sludge And Toxic Effects Of PFOS/Cu Combined Pollution On Sludge Microorganism

Perfluorooctane sulfonate(PFOS)and copper(Cu)were detected widely in wastewater treatment plants(WWTPs),and caused potential adverse impacts on sewage treatment process,such as decreasing the efficiency of nitrogen and phosphorus removal,interfering with the community structure of activated sludge microorganisms,even destroying the biological treatment system.In this study,the adsorption mechanism of PFOS on activated sludge and the toxic effects of PFOS and Cu on activated sludge microorganisms were explored.The adsorption of PFOS on activated sludge and extracellular polymeric substance(EPS)removed sludge was conducted to investigate the adsorption mechanism of PFOS on activated sludge.The results suggested that adsorption efficiency performed better on normal activated sludge compared to EPS removed sludge,indicating that EPS components played a vital role in PFOS adsorption.Chemisorption played an important role in the adsorption of PFOS on activated sludge.There was electrostatic attraction effect between PFOS and activated sludge.Adsorbing capacity of PFOS decreased with the increasing of pH.Ca2+ and Cu2+ contributed to PFOS adsorption on activated sludge through ion-bridging effect.FTIR and XPS results showed that carboxyl and amidogen contained in proteins of EPS provided reaction sites for PFOS adsorption.Long-term exposure experiments with single and combined pollutants of Cu and PFOS were conducted to explore the influence on pollutants removal in sequencing batch reactors(SBRs),microbial activity and variations of microbial community structure.Compared with the control,the removal of chemical oxygen demand(COD)concentration,ammonia nitrogen(NH4+-N),total nitrogen(TN)and total phosphorus(TP)in the presence of PFOS exhibited no apparent difference,while the removal rates decreased when Cu and PFOS/Cu combined pollutants existed,but improved after 17 d in PFOS/Cu combined pollution.PFOS exposure deteriorated the settling performance of activated sludge with microbial biomass,SVI value and amount of EPS increasing,but microbial biomass decreased under Cu and combined pollutants exposure.Meantime,PFOS posed little impacts on microbial activity(dehydrogenase,protease)and antioxidant activity(SOD,CAT).Under the influence of Cu and combined pollutants,however,dehydrogenase and protease activity were observed to decrease as well as SOD and CAT.After 20 d,antioxidant capacity began to recover gradually under Cu/PFOS loading.The high-throughput sequencing results revealed that single PFOS had little influence on bacterial richness and community diversity of activated sludge microorganisms,of which community structure was similar to control.Bacterial richness and community diversity apparently reduced under single Cu exposure compared to that under combined pollutants exposure.Amounts of functional flora with the capacity of nitrogen and phosphorus removal decreased.Overall,adverse effect of single Cu loading was higher than that of single PFOS and PFOS/Cu combined pollution in long-time,and Cu played a vital role in joint pollution.Antagonistic effect,rather than synergistic effect of toxicity existed in Cu and PFOS.