Improving primary sludge dewaterability by oxidative conditioning process with ferrous ion-activated peroxymonosulfate
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pISSN: 0256-1115 eISSN: 1975-7220
INVITED REVIEW PAPER
INVITED REVIEW PAPER
Improving primary sludge dewaterability by oxidative conditioning process with ferrous ion-activated peroxymonosulfate Xu Zhou*, Wenbiao Jin*, Lan Wang*, Wanqing Ding*, Chuan Chen**,†, Xijun Xu**, Renjie Tu*, Song-Fang Han*, Xiaochi Feng*, and Duu-Jong Lee***,**** *Shenzhen Engineering Laboratory of Microalgal Bioenergy, Harbin Institute of Technology (Shenzhen), 518055 Shenzhen, China **State Key Laboratory of Urban Water Resource and Environment (SKLUWRE), Harbin Institute of Technology, 150001, Harbin, China ***Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan ****Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (Received 20 November 2019 • Revised 11 February 2020 • Accepted 17 February 2020) AbstractEnhancement of sludge dewaterability is key for sludge management and disposal of wastewater treatment plants (WWTP). In this study, the Fe2+-peroxymonosulfate (PMS) conditioning approach was first used to oxidize the primary sludge from the primary sedimentation tank of a full scale WWTP. The combination of Fe2+ (0.05-0.5 g/g TSS) and PMS (0.05-0.5 g/g TSS) could significantly improve the dewaterability of primary sludge. The optimal addition amount of Fe2+ and PMS was 0.1 g/g TSS and 0.25 g/g TSS, respectively, under which the capillary suction time (CST) and specific resistance to filtration (SRF) of the sludge was reduced by 79% and 95%. The physicochemical properties (particle size, zeta potential, EPS composition) of the primary sludge before and after oxidative conditioning were measured. Results showed that sulfate radicals generated from Fe2+-PMS system effectively reduced organic matter in different EPS fractions, further destroying sludge floc cells. Then the bound water in the sludge flocs was released, thereby improving the sludge dewaterability. The microscopic morphology also indicated that the sludge flocs have a blocky structure with tight texture before conditioning. After conditioning, the sludge flocs become smaller, and many irregular pores are formed on the surface, which facilitates the passage of internal moisture. Economic analysis showed that Fe2++PMS conditioning is more economical than the traditional Fenton method. Keywords: Dewaterability, Oxidative Conditioning Process, Peroxymonosulfate, Primary Sludge, Ferrous
ising sludge conditioning method because of its remarkable effect on improvement of sludge dewaterability. The method generates strong oxidizing free radicals through a series of reactions, such as hydroxyl radical ∙OH and sulfate radicals SO4·, destroying microbial cells, degrading EPS, and releasing bound water to change the structure of sludge flocs [15]. The traditional Fenton method can improve the dewaterability of sludge by the formation of ∙OH by Fe2+ catalyzed H2O2 under acidic conditions [16,17]. However, H2O2 is chemically unstable in the Fenton reaction, so the reaction needs to be carried out
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