Journal of Hazardous Materials 190 (2011) 645–651 Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Formation of disinfection by-products in the chlorination of ammonia-containing efﬂuents: Signiﬁcance of Cl 2 /N ratios and the DOM fractions Hua Zhang a , Huijuan Liu a,b,∗ , Xu Zhao a , Jiuhui Qu a , Maohong Fan b a State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China b School of Energy Resources & Department of Chemical & Petroleum Engineering, University of Wyoming, Laramie, WY 82071, USA article info Article history: Received 16 September 2010 Received in revised form 22 March 2011 Accepted 26 March 2011 Available online 6 April 2011 Keywords: Ammonia nitrogen Disinfection-by products Dissolved organic matter Chlorination breakpoint abstract The presence of ammonia nitrogen (NH 3 –N) in the efﬂuent strongly affected the formation of disinfection by-products (DBPs) during its chlorination. The effect of chlorine (as mg/L Cl 2 ) to NH 3 –N (as mg/L N) mass ratios (Cl 2 /N) and the chemical fractions of dissolved organic matter (DOM) in the efﬂuent on the DBPs formation was investigated. Results indicated that the formation of DBPs increased with increasing Cl 2 /N. The concentration and speciation of DBPs varied among different DOM fractions at different zones of chlo- rination breakpoint curves. The formation rate of total haloacetic acids (THAA) and total trihalomethanes (TTHM) was promoted after the chlorination breakpoint, whereas the reaction of monochloramine with HOCl to dichloramine may cause a decrease in the DBPs formation potential thereafter. Organic acids were found to be the dominant precursors of DBPs with or without the presence of NH 3 –N, which indicated that the C C, C O and C–O structures contributed to the formation of DBPs signiﬁcantly. In addition, the incorporation of bromine in THMs of the HiA fraction increased with the increasing of Cl 2 /N mass ratios before the chlorination breakpoint, but decreased sharply after the breakpoint. A 280 (absorbance at 280 nm), deﬁned as A 280,initial - A 280,ﬁnal , was proved to be linearly related to the TTHM and THAA of wastewater without containing Br - during chlorination or chloramination. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Chlorination is a well-developed and widely used process for wastewater disinfection because of its broad spectrum germici- dal potency, low cost, and well-established practices. However, the reactions between chlorine and dissolved organic matter (DOM) produce numerous disinfection by-products (DBPs), of which tri- halomethanes (THMs) and haloacetic acids (HAAs) are the most prevalent ones by weight [1,2], which is found in most wastewa- ter efﬂuents, could inﬂuence the disinfection process. First, NH 3 –N may result in the formation of highly toxic nitrogenous DBPs, which were reported to serve as intermediates to yield dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), and chloroform [3–7]. Second, the chloramines formed by reactions of NH 3 –N and chlorine could interfere in the formation of THMs and HAAs. The formation of by- products will be affected by the ratios of Cl 2 and NH 3 –N, resulting in different DBPs with different species and structure. In addition, the reactions between DOM fractions and chlorine at different Cl 2 /N ∗ Corresponding author at: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. Tel.: +86 10 62849160; fax: +86 10 62849160. E-mail address: hjliu@rcees.ac.cn (H. Liu). ratios will also vary the DBP species and their formation condi- tions. Yang et al. [8] demonstrated that there existed breakpoint curves in chlorination of wastewater containing NH 3 –N and the THM and HAA formation showed signiﬁcantly different inclination below and beyond the breakpoint dosing level. DOM in efﬂuents from sewage treatment plants (STPs) is com- posed of recalcitrant natural organic matter (NOM) due to surface runoff of rain water, synthetic organic chemicals added during anthropogenic use and soluble microbial products [9–12]. The com- plex composition of total DOM poses a great challenge in research of the mechanism of DOM reactions with chlorine. Therefore, the resin adsorption chromatography (RAC) technique [9,13] is quite useful for isolating DOM into different fractions. With the applica- tion of RAC, Wang et al. [14] demonstrated that NH 3 –N signiﬁcantly inﬂuenced the genotoxicity of DOM fractions during chlorina- tion. To our best knowledge, no report is available about the DBP speciation in chlorination at different Cl 2 /N ratios, or about the effect of the chemical characteristics of DOM fractions on DBP formation. The main objectives of this study were (1) to investigate the effect of NH 3 –N on the concentrations and species of DBPs during chlorination of DOM fractions; (2) to illuminate the relationship of the characteristics of DOM fractions and the DBP formation at different Cl 2 /N ratios. This work should shed light on the removal 0304-3894/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2011.03.098