A two-step approach of ozonation pre-oxidation and re-flocculation to regulate drinking water treatment sludge: Sludge reflux and enhanced coagulation

• Published in: Separation and purification technology Vol. 335; p. 126130
• Main Authors: Li, Shizhao, Li, Xing, Zhou, Zhiwei, Wang, Changyu, Yang, Yanling, Feng, Jianyong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.05.2024
• Subjects: Drinking water treatment sludge; Enhanced coagulation; Ozonation pretreatment; Sludge re-flocculation; Sludge recycling; Enhanced coagulation; Ozonation pretreatment; Sludge recycling; Sludge re-flocculation; Drinking water treatment sludge
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2023.126130

[Display omitted] •Ozonation with PACl and PAM re-flocculation first regulated recycled DWTS.•Ozonation pre-oxidation reduced enrichment of organics in DWTS recycling process.•The floc morphology of recycling sludge was improved by re-flocculation.•Coagulation behavior of DWTS recycling process was improved by two-step regulation. The characteristics of drinking water treatment sludge (DWTS) are important factors limiting the coagulation effect after sludge recycling. To enhance the coagulation performance of DWTS recycling, a two-step pretreatment strategy was employed, including ozonation pre-oxidation and the re-flocculation of polymeric aluminum chloride (PACl) and polyacrylamide (PAM). Ozonation pre-oxidation transformed insoluble organic matter into dissolved organic matter (DOM), reducing the organic content by 12.58% for UV254 and 8.94% for dissolved organic carbon (DOC) in the DWTS recycling process. Following re-flocculation with PACl and PAM, the size, zeta potential, and settling velocity of the ozonated sludge were further increased from 30.27 μm, −12.57 mV, and 2.06 mm/s to 187.6 μm, −3.49 mV, and 6.42 mm/s, respectively, which exhibited higher turbidity removal in DWTS recycling process. Following the two-step method, larger, denser, and more reversible flocs were observed during the recycling process, and the settling efficiency of the flocs was enhanced, which enabled achieving better water quality in a shorter duration. These findings provide innovative insights into drinking water plant optimization and sludge management.