Optimizing waste activated sludge disintegration by investigating multiple electrochemical pretreatment conditions: Performance, mechanism and modeling

• Published in: The Science of the total environment Vol. 870; p. 162025
• Main Authors: Lin, Qingshan, Dong, Xinlei, Xi, Shihao, Cheng, Boyi, Zan, Feixiang, Ma, Jie, Liu, Xiaoming, Hao, Tianwei, Guo, Gang
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 20.04.2023
• Subjects: Cost-effectiveness; Electrochemical pretreatment; Reactive chlorine species; Waste activated sludge disintegration; Electrochemical pretreatment; Waste activated sludge disintegration; Cost-effectiveness; Reactive chlorine species
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.162025

The complex and rigid floc structure often limits the reutilization of waste activated sludge (WAS). Electrochemical pretreatment (EPT) is one of the most effective technologies that can enhance WAS disintegration. But a comprehensive investigation into how multiple EPT conditions work was rarely reported. The study evaluated the effects of multiple EPT conditions, i.e., different electrolytes (NaCl, Na2SO4, and CaCl2), electrolytes dosage (0 g/L, 0.5 g/L, 1.0 g/L, and 3.0 g/L), EPT current (0 A, 0.5 A, 1.0 A, and 3.0 A) and EPT time (0 min, 30 min, 60 min, and 90 min) on WAS disintegration. The results showed that NaCl was outstanding from other electrolytes in promoting more WAS disintegration. Besides, a relatively higher NaCl dosage, a higher EPT current, and a longer EPT time promoted more reactive chlorine species (RCS), thus enhancing WAS disintegration in terms of extracellular polymeric substances (EPS) structure destruction and biodegradable organic matter release. After EPT for 60 min at NaCl dosage of 1.0 g/L and current of 1.0 A, the EPS multilayer structure destruction, biodegradable organic matters release, and soluble chemical oxygen demand (SCOD) increase in the supernatant were enhanced by 17.2 %, 130.5 %, and 238.7 %, respectively. Then a predictive quadratic model was established and the impact significance of the above EPT factors for enhancing WAS disintegration followed dosage of NaCl > current > EPT time. Furthermore, response surface methodology (RSM) suggested NaCl dosage of 2.75 g/L, current of 2.0 A, and EPT time of 30 min were the optimal EPT conditions, bringing a 42.0 % increase in the net economic benefit of WAS treatment compared to without EPT. [Display omitted] •Effect of electrolyte dosage, current and time on WAS disintegration were studied.•Quadratic model and response surface methodology revealed optimal EPT conditions.•The mechanism about WAS disintegration under multiple EPT conditions was revealed.•An application potential of WAS treatment via EPT was proposed.•The optimal EPT conditions brought more net economic benefit of WAS treatment.