Dewaterability enhancement and sulfide mitigation of CEPT sludge by electrochemical pretreatment

• Published in: Water research (Oxford) 2020-06, Vol.176, p.115727-115727, Article 115727
• Main Authors: Zeng, Qian, Hao, Tianwei, Yuan, Zhiguo, Chen, Guanghao
• Format: Article
• Language: English
• Subjects: Dewaterability enhancement; Electrochemical pretreatment; Filtration; Hydrogen Sulfide; Sewage; Sludge treatment; Sulfate reduction; Sulfides; Sulfur; Water
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2020.115727

Dewatering and sulfide control are the key challenges in treating chemically enhanced primary treatment (CEPT) sludge. In this study, an electrochemical pretreatment (EPT) approach with the input of 10 V/800 mA was explored for simultaneously improving the dewaterability of CEPT sludge and eliminating its sulfide production. The effects of different electrode materials (carbon and titanium) and EPT durations (from 5 to 15 min) were documented to reveal the underlying EPT mechanism. EPT with titanium electrodes (titanium-EPT) led to limited improvement in dewaterability and sulfide control. EPT with carbon electrodes (carbon-EPT) for 15 min, however, led to decreases in capillary suction time and specific resistance in filtration of over 80% and the suppression of about 99% of hydrogen sulfide (H2S(g)) production over 5 days of anaerobic storage. Analysis of the characteristics of treated CEPT sludge revealed that carbon-EPT disintegrated sludge flocs with ∼70% reduction in sludge particle sizes and release of aromatic and tyrosine protein-like substances, thus enhancing sludge dewaterability. The sulfur balance in the liquid and gaseous phases showed that most of the sulfur-containing compounds remained in the solid phase as aliphatic sulfur and sulfonic acid after carbon-EPT, thereby mitigating sulfide emission. While the pattern of sulfur distribution in sludge with titanium-EPT was dominated by sulfide, it was similar to the control sample. Reduction in bacteria associated with sulfide production (i.e., Lachnospiraceae) in CEPT sludge after carbon-EPT also contributed to sulfide elimination. This study demonstrates that EPT can be a superior option for simultaneously enhancing the dewaterability of CEPT sludge and mitigating its sulfide production. [Display omitted] •Two types of electrodes (carbon and titanium) were tested for sludge pretreatment.•Only carbon-EPT can enhance dewaterability and mitigate sulfide of CEPT sludge.•Carbon-EPT disintegrated CEPT sludge flocs and enhanced dewaterability by over 80%.•Carbon-EPT removed ∼99% of sulfide while Ti-EPT slightly increased sulfide production.•Sulfur compounds were stored in the solid phase, mitigating H2S emission.