title: Enhancement of waste activated sludge dewaterability using calcium peroxide pre-oxidation and chemical re-flocculation.
abstract: The effects of combined calcium peroxide (CaO2) oxidation with chemical re-flocculation on dewatering performance and physicochemical properties of waste activated sludge was investigated in this study. The evolutions of extracellular polymeric substances (EPS) distribution, composition and morphological properties were analyzed to unravel the sludge conditioning mechanism. It was found that sludge filtration performance was enhanced by calcium peroxide oxidation with the optimal dosage of 20 mg/gTSS. However, this enhancement was not observed at lower dosages due to the absence of oxidation and the performance deteriorated at higher dosages because of the release of excess EPS, mainly as protein-like substances. The variation in soluble EPS (SEPS) component can be fitted well with pseudo-zero-order kinetic model under CaO2 treatment. At the same time, extractable EPS content (SEPS and loosely bound EPS (LB-EPS)) were dramatically increased, indicating sludge flocs were effectively broken and their structure became looser after CaO2 addition. The sludge floc structure was reconstructed and sludge dewaterability was significantly enhanced using chemical re-flocculation (polyaluminium chloride (PACl), ferric iron (FeCl3) and polyacrylamide (PAM)). The inorganic coagulants performed better in improving sludge filtration dewatering performance and reducing cake moisture content than organic polymer, since they could act as skeleton builders and decrease the sludge compressibility.
authors.affiliation: School of Environmental Studies, China University of Geosciences, Wuhan 430074, Hubei, China; State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; School of Civil Engineering, Inner Mongolia University of Technology, Hohhot 010051, China.
authors.forename: Zhan
authors.initials: Z
authors.lastname: Chen
authors.affiliation: School of Environmental Studies, China University of Geosciences, Wuhan 430074, Hubei, China. Electronic address: zhwj_1986@126.com.
authors.forename: Weijun
authors.initials: W
authors.lastname: Zhang
authors.affiliation: School of Environmental Studies, China University of Geosciences, Wuhan 430074, Hubei, China; State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. Electronic address: wgds@rcees.ac.cn.
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Wang
authors.affiliation: School of Environmental Studies, China University of Geosciences, Wuhan 430074, Hubei, China.
authors.forename: Teng
authors.initials: T
authors.lastname: Ma
authors.affiliation: School of Civil Engineering, Inner Mongolia University of Technology, Hohhot 010051, China.
authors.forename: Runying
authors.initials: R
authors.lastname: Bai
authors.affiliation: School of Chemistry and Environmental Engineering, Wuhan Institute of Technology, 430073 Hubei, China.
authors.forename: Dezhong
authors.initials: D
authors.lastname: Yu
mesh_terms: D005374:Filtration; D005427:Flocculation; D010084:Oxidation-Reduction; D011108:Polymers / Q000737:chemistry; D012722:Sewage / Q000737:chemistry*
chemical_list: D011108:Polymers; D012722:Sewage
keywords: Calcium peroxide pre-oxidation; Chemical flocculation; Dewatering behavior; Extracellular polymeric substances; Waste activated sludge