DBP formation and toxicity alteration during UV/chlorine treatment of wastewater and the effects of ammonia and bromide. (1st January 2021)

• Record Type: Journal Article
• Authors: Hua, Zhechao; Li, Dan; Wu, Zihao; Wang, Ding; Cui, Yonglin; Huang, Xiongfei; Fang, Jingyun; An, Taicheng
• Is Part Of: Water research. Volume 188(2021)
• Publication Date: 2021-01-01
• Subjects: UV/chlorine -- Disinfection by-products -- Toxicity -- Ammonia -- Bromide -- Wastewater; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2020.116549
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: The UV/chlorine treatment efficiently degraded diverse components in wastewater. HAcAms, HANs and TCNM significantly increased after UV/chlorine treatment. Acute and geno- toxicities of wastewater decreased after UV/chlorine treatment. Bromide reduced acute and geno- toxicities of wastewater during UV/chlorine. Ammonia enhanced TCNM formation but reduced HAcAm and HAN formation in UV/chlorine. Abstract: The UV/chlorine process is efficient for the abatement of micropollutants; yet, the formation of disinfection by-products (DBPs) and the toxicity can be altered during the treatment. This study investigated effluent organic matter characterization, DBP formation and toxicity alteration after the UV/chlorine treatment of wastewater; particularly, typical water matrix components in wastewater, namely, ammonia and bromide, were studied. The raw wastewater contained low levels of ammonia (3 µM) and bromide (0.5 µM). The UV/chlorine treatment efficiently eliminated 90 – 94% of fluorescent components. Compared with chlorination alone, a 20 min UV/chlorine treatment increased the formation of trihalomethanes (THMs), haloacetic acids (HAAs), chloral hydrate (CH), haloacetonitriles (HANs), trichloronitromethane (TCNM) and haloacetamides (HAcAms) by 90 – 508%. In post-chlorination after the UV/chlorine treatment, the formation of CH, HANs, TCNM and HAcAms increased by 77 – 274%, whereas the formation of both THMs and HAAs increased slightly by 11%. Meanwhile, the calculated cytotoxicity and genotoxicity of DBPs increased considerably after the UV/chlorine treatment and in post-chlorination, primarily due to the increased formation of HAAs and nitrogenous DBPs (N-DBPs). However, the acute toxicity of the wastewater to Vibrio fischeri and genotoxicity determined by the umu test decreased by 19% and 76%, respectively, after the 20 min UV/chlorine treatment. An additional 200 µM ammonia decreased the formation of all detected DBPs during the UV/chlorine treatment and 24 h post-chlorination, except that TCNM formation increased by 11% during post-chlorination. The acute toxicity of wastewater spiked with 200 µM ammonia was 32% lower than that of raw wastewater after the UV/chlorine treatment, but the genotoxicity was 58% higher. The addition of 1 mg/L bromide to the UV/chlorine process dramatically increased the formation of brominated DBPs and the overall calculated cytotoxicity and genotoxicity of DBPs. However, the acute toxicity and genotoxicity of the wastewater decreased by 7% and 100%, respectively, when bromide was added to the UV/chlorine treatment. This study illuminated that UV/chlorine treatment can decrease acute and geno- toxicities of wastewater efficiently. Graphical abstract: Image, graphical abstract