Insight into the fenton-induced degradation process of extracellular polymeric substances (EPS) extracted from activated sludge

Although EPS in microbial aggregates are importance in successful implementation of biological wastewater treatment systems, they also exhibit detrimental role on certain circumstance, such as excess sludge dewatering. Extensive efforts have been put into the disruption of EPS for improving the dewaterability of excess sludge and Fenton's reagent treatment has been demonstrated to be a very promising sludge conditioning method for EPS destruction. However, the information regarding detailed degradation process of EPS during Fenton's reagent treatment is limited. In this study, EPS were extracted from activated sludge and treated with different concentrations of Fenton's reagent. The physicochemical characteristic changes of EPS under different treatment were investigated in terms of components, EEM, molecular weight (MW), UV-Vis and FTIR. The results showed that EPS were prone to be disintegrated, but hard to be fully mineralized. Humic substances in EPS were more resistant to Fenton's reagent than other components. Low MW components of EPS were preferentially degraded prior to the disruption of high MW components. Besides, the disintegration of EPS into lower MW ones was accompanied by the formation of higher MW compounds caused by the bridge interaction of Fe ions. The cleavage of protein's backbone in EPS was mainly through destruction of amide II (N–H and C–N) in –CO–NH–. Fenton's reagent treatment also led to a significant increase of oxygen-containing functional groups in EPS molecules. This paper may pave a path to deeply understand the mechanisms of dewatering improvements of excess sludge by Fenton's conditioning.