Effects of operating conditions on trihalomethanes formation and speciation during chloramination in reclaimed water

Abstract

In this study, a hybrid powdered activated carbon-membrane bioreactor (PAC-MBR) system was used to treat municipal wastewater in northern China intended for recycle. In order to control microbiological hazards in PAC-MBR effluent, chloramine was chosen as the disinfectant which could reduce the disinfection by-product yields. Effects of reaction time, chloramines dose, pH value, and bromide ion concentration on trihalomethanes (THMs) formation and speciation during chloramination of the reclaimed effluent were investigated. Study results indicated that the yield of total THMs (TTHM) increased at higher reaction time and chloramines dose. The trend of growth showed that slow reacting precursors were the main components of dissolved organic matter (DOM) in PAC-MBR effluent. THMs formation potential of PAC-MBR effluent achieved the maximum at chloramines dosage of 20 mg/L. Meanwhile, THMs formation was enhanced evidently under alkaline conditions. The yields of THMs species were in following order: CHCl3 > CHBrCl2 > CHBr2Cl > CHBr3, although in different reaction time, chloramines dose, and pH value. Furthermore, the formation of Br-THMs was promoted by the increasing concentration of bromide ion.

Formation of typical disinfection by-products (DBPs) during chlorination and chloramination of polymyxin B sulfate

“…1(b) that the effect of monochloramine dose on DBPs formation showed different characteristics. The yields of CF, DCAN and TCNM all increased with disinfectant dosage (the same trend as previous studies 22,23 ) and CF could catch up with DCAN during chloramination. Particularly, TCNM only can be detected when [Cl 2 ]/[PBS] ≥50.…”

Enhancement of UV disinfection of urine matrixes by electrochemical oxidation

“…Likewise, the presence of chloramines minimizes the production of trihalomethanes (THMs) and trihalogenated haloacetic acids as disinfection by-products [61,62] and, hence, decreases the accumulation of hazardous organochlorinated compounds in treated effluents. The formation of chloramines follows a sequential reaction that starts with the generation of monochloramine (Eq.…”

Temperature dependence of hydroxyl radical reactions with chloramine species in aqueous solution

“…However, the application of chlorine leads to the formation of halogenated disinfection by-products (DBPs) that are toxic to the environment and show evidence of human toxicity through chronic exposure (Rook, 1974; Krasner et al, 2006; Richardson et al, 2007; Krasner, 2009; Krasner et al, 2009a, 2009b). Consequently, many water utilities are now considering the use of monochloramine as an alternative water disinfectant because its reaction with dissolved organic matter (DOM), in general, promotes lower formation of regulated DBPs such as haloacetic acids and trihalomethanes (EPA, 1999; Diehl et al, 2000; Vikesland et al, 2001; Hua and Reckhow, 2008; Zha et al, 2014; Wang et al, 2016).…”

“…However, the simultaneous presence of chloramines and chlorine reacting with DOM can increase overall DBP production (Wang et al, 2016), and the reaction of monochloramine with DOM and other trace chemical contaminants can produce N -nitrosodimethylamine and other species such as aromatic halogenated DBPs (Pan and Zhang, 2013; Hua et al, 2015; LeRoux et al, 2016; Pan et al, 2016; LeRoux et al, 2017; Jiang et al, 2017; Tian et al, 2017) that can be more toxic than trihalomethanes and haloacetic acids, but are currently not as widely regulated (Krasner et al, 2013; Pan et al, 2013; Gong et al, 2016; Guo et al, 2016; Nihemaiti et al, 2016; Zeng et al, 2016; Spahr et al, 2017). The specific timing of chloramination in the water treatment train is thus very important; chloramines need to be generated at specific times that allows for maximum microbial inhibition while minimizing harmful DBP formation (Carlson and Hardy, 1998; Hua and Reckhow, 2007; Wang et al, 2016). In post-treated wastewaters, levels of monochloramine (NH 2 Cl) can exceed 2 mg L −1 (measured as equivalent Cl 2 ) (Johnson et al, 2002).…”