Effects of acid, acid-ZVI/PMS, Fe(II)/PMS and ZVI/PMS conditioning on the wastewater activated sludge (WAS) dewaterability and extracellular polymeric substances (EPS)

The effects of four conditioning approaches: Acid, Acid-zero-valent iron (ZVI)/peroxydisulfate (PMS), Fe(II)/PMS and ZVI/PMS, on wastewater activated sludge (WAS) dewatering and organics distribution in supernatant and extracellular polymeric substances (EPS) layers were investigated. The highest reduction in bound water and the most WAS destruction was achieved by Acid-ZVI/PMS, and the optimum conditions were pH 3, ZVI dosage 0.15 g/g dry solid (DS), oxone dosage 0.07 g/g DS and reaction time 10.6 min with the reductions in capillary suction time (CST) and water content (Wc) as 19.67% and 8.49%, respectively. Four conditioning approaches could result in TOC increase in EPS layers and supernatant, and protein (PN) content in tightly bound EPS (TB-EPS). After conditioning, organics in EPS layers could migrate to supernatant. Polysaccharide (PS) was easier to migrate to supernatant than PN. In addition, Acid, Acid-ZVI/PMS or Fe(II)/PMS conditioning promoted the release of some polysaccharides containing ring vibrations v P]O, v C-O-C, v C-O-P functional groups from TB-EPS. ESR spectra proved that both radicals of SO4-. and center dot OH contributed to dewatering and organics transformation and migration. CST value of WAS positively correlated with the ratios of PN/PS in LB-EPS and total EPS, while it negatively correlated with TOC, PN content and PS content in TB-EPS, as well as PS content in supernatant and LB-EPS. BWC negatively correlated to zeta potential and TOC value, PN content, and HA content in supernatant. (C) 2020 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.