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. 2025 Dec 8;198(1):22.
doi: 10.1007/s10661-025-14877-8.

Formation of disinfection by-products (DBPs) in water and wastewater treatment systems in Tamil Nadu: evaluating chlorination alternatives for safer water quality

Sellappa Kanmani  1 , Pandian Ganesh Kumar  2 , Albert Mariathankam Nizzy  3 , Annenewmy B  3
Affiliations

Formation of disinfection by-products (DBPs) in water and wastewater treatment systems in Tamil Nadu: evaluating chlorination alternatives for safer water quality

Sellappa Kanmani et al. Environ Monit Assess. .

Abstract

Disinfection is a critical process in water and wastewater treatment to pathogen control and achieve Sustainable Development Goal (SDG-6). However, the formation of intermediate compounds during disinfection, known as disinfection byproducts (DBPs), poses adverse effects to human health. Trihalomethanes (THMs) and haloacetic acids (HAAs) are the major regulated halogenated DBPs formed during chlorination. In India, chlorination remains the conventional disinfection method in water and wastewater treatment systems. This study investigated the formation of THMs and HAAs in chlorinated water and wastewater samples from selected treatment facilities in Tamil Nadu, South India. Results indicated that regulated THMs (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) were consistently detected across all seasons, with chloroform being the predominant species (226 µg/L). Trace amounts of HAAs were also detected, with elevated THM formation observed during summer. Additionally, the disinfection efficiency of alternative methods-chloramination, ozonation, UV irradiation, and sequential addition of disinfectants were evaluated. Lab-scale studies on DBP formation reveal distinct trends among different treatment methods. This study comparatively evaluated the formation of total trihalomethanes (TTHMs) in water treatment plant (WTP) and sewage treatment plant (STP) effluents under different disinfectants. In WTP samples, chlorine disinfection at a 5 mg/L dosage generated the highest TTHM concentration (197 µg/L), followed by chloramine (171 µg/L). This result was consistent in lab-scale studies with STP samples, where chlorination also resulted in the maximum TTHM formation, reaching 135.2 µg/L. In contrast UV irradiation generates significantly lower THMs and HAAs levels, while ozonation results in even fewer byproducts. Notably, the combination of chloramine with UV light proved most effective, yielding the lowest TTHMs concentrations of 32.2 and 35 µg/L. The lowest concentrations are observed with UV/ozone treatment with turbidity reduction. This hierarchy (chlorine (Cl2) > chloramine (NH2Cl) > UV > ozone > UV/ozone) highlights THMs and HAAs mitigation in water treatment processes. These findings highlight the necessity of adopting alternative disinfection strategies to minimize DBP-related health risks while ensuring effective microbial inactivation. The study also assessed the THMs and HAAs formation potential and bromine incorporation factor to optimize chlorine disinfectant dosage and emphasize the need for bromine removal in source water.

Keywords: Bromine incorporation factor; Chloramination; Disinfection byproducts; Formation potential; Ozonation.

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Conflict of interest statement

Declarations. Competing interests: The authors declare no competing interests.

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