The Performance and Extracellular Polymeric Substances Variations of an Anaerobic-Anoxic-Oxic Wastewater Treatment Process Subjected to Organic Carbon and Ammonia Nitrogen Shock Loadings

Sudden changes in influent organic carbon (OC) and ammonia nitrogen (AN) concentrations were performed to evaluate the resistance of A 2 O process against shock loadings. The influent organic loading rate was increased from 11 gCOD/(gMLSS·d) to 48 gCOD/(gMLSS·d) with low OC shocking loading and to 125 g COD/(gMLSS·d) with high OC shock loading. The influent NH4 + -N was increased from 55 mg/L to 110 mg/L as AN shock loading. The results showed that the augmented OC concentration was beneficial for nitrogen removal and high AN concentration had slight influences on COD removal, but was detrimental to nitrogen removal in the A 2 O system. The performance of the A 2 O system restored rapidly from the shock loadings once the normal influent conditions were provided. The loosely bound extracellular polymeric substances (LB-EPS) and total extracellular polymeric substances (EPS) increased at the initial stage of shock loadings and then declined with the prolonged shock loading, whereas the tightly bound EPS (TB-EPS) experienced smaller variations. The SVI value varied in a similar trend with LB-EPS and total EPS and their low values indicated a good settleability of the activated sludge. In conclusion, the A 2 O process produced high-quality effluents once the shock loading ceased.