Modelling of haloacetic acid concentrations in a United Kingdom drinking water system Yanping Zhang, David Martinez, Christopher Collins, Nigel Graham, Michael R. Templeton, Jin Huang and Mark Nieuwenhuijsen ABSTRACT Haloacetic acids (HAAs) are formed during the chlorination of water containing organic matter but predictive models for their formation are not well established at present and have not been applied to UK water systems. In this paper two different modelling approaches have been applied and evaluated to a selected UK drinking water system. The first approach involved the development of statistical predictive models for the HAA formation by using multiple linear regression with appropriate water quality and operational parameters obtained from sampling, and the second approach employed the simulated distribution system (SDS) test. Statistically significant predictors were trihalomethane (THM) levels, pH, temperature, total chlorine total organic carbon, UV 254 , bromide concentration and residence time, but the importance of each varied with HAA species. The models that generally explained most of the variance of individual and total HAAs included THMs as a predictor variable. The use of the SDS-HAA test included quantification of individual HAA species. The concentration of total HAA and individual compounds in the SDS test and field samples were comparable immediately after chlorination, but with increasing residence time the concentration of HAAs in the selected water distribution system were greater than those found in the SDS test. Yanping Zhang Nigel Graham (corresponding author) Michael R. Templeton Jin Huang Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK E-mail: n.graham@imperial.ac.uk Yanping Zhang Christopher Collins Department of Soil Science, University of Reading, Reading, RG6 6DW, UK David Martinez Mark Nieuwenhuijsen Centre for Research in Environmental Epidemiology (CREAL), 08003 Barcelona, Spain IMIM, 08003 Barcelona, Spain and CIBERESP, 08003 Barcelona, Spain Key words | disinfection by-products, distribution system, drinking water, haloacetic acids, multiple linear regression models INTRODUCTION Disinfection is an important process in the treatment of drink- ing water supplies as it removes or inactivates pathogenic microorganisms responsible for waterborne disease such as cholera and dysentery (Uyak et al. ). Chlorination is a widely used disinfection method because of its efficient and cost-effective properties. However, disinfection by-products (DBPs) are generated during water disinfection due to the reaction of chlorine with natural organic matter (NOM) con- tained in the raw water and in treated water at the point of final disinfection. Because of their potential health risks, four groups of DBPs are regulated currently under the United States Environmental Protection Agency (USEPA) Stage 1 Disinfectant and Disinfection By-products (D/DBP) Rules (USEPA ). These four groups are trihalomethanes (THMs), haloacetic acids (HAAs), chlorite and bromate. The maximum contaminant levels (MCLs) established by the D/DBP Stage 1 Rules are 80 μg/l for total THMs, 60 μg/l for HAA 5 , 1 mg/l for chlorite and 10 μg/l for bromate. The term HAA 5 describes the group of the following five HAA compounds, monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), monobromoace- tic acid (MBAA), and dibromoacetic acid (DBAA). In the United Kingdom HAA compounds are not regulated, but there is considerable interest in their occurrence and for- mation since regulation may be introduced soon; recently a standard of 80 μg/l for HAA 9 has been suggested for the 275 © IWA Publishing 2011 Journal of Water Supply: Research and Technology—Aqua | 60.5 | 2011 doi: 10.2166/aqua.2011.047 Downloaded from https://iwaponline.com/aqua/article-pdf/60/5/275/401788/275.pdf by guest on 14 June 2020