Approaches to regulating organic carbon and the necessity of its obligatory monitoring in drinking water

Background: Current accumulation of organogenic elements in surface waters is mainly attributed to intensive anthropogenic activities. Waterborne organic matter may endanger human health when using surface waters for drinking and recreational purposes. Applied techniques of water treatment fail to ensure complete water purification and part of organic substances (their low molecular weight fraction) still remains. Chlorination of drinking water can generate a variety of halogenated by-products having adverse health effects in humans including carcinogenic ones. Our objective was to substantiate the reference value for total organic carbon (TOC) in water disinfected by chlorine. Materials and methods: We analyzed the results of laboratory testing of surface and treated water samples taken in Yekaterinburg in 2013-2014 and 2017, carried out health risk assessment, and built predicative models of by-products formation. Results: We established that, following chlorination, TOC concentrations became 1.5 times lower while chloroform and total trihalomethane concentrations became 24.5-80.2 and 22.9-54.5 times higher than initial values, respectively. The most significant non-carcinogenic risks were estimated for children aged 0-6 years from exposures to chloroform (HQ = 1.150). Individual carcinogenic risks from exposures to bromoform and dibromochloromethane as measured in water before its supplying to the distribution system, referred to the first value range (less than 1x10^-6) while risks from bromodichloromethane and chloroform exposures fell in the second range (from 1x10^-6 to 1x10^-4). The mathematical model of the correlation between predictors (temperature, reaction time, pH, and certain chemical compounds) and levels of by-products was built. Conclusions: Our model makes it possible to predict generation of organochlorine compounds at the design stage of water treatment technique. Total organic carbon is an important indicator that should be monitored at the stages of water treatment to ensure safety of drinking water and efficiency of its disinfection.

total organic carbon, regulation, drinking water, trihalomethanes

1. Рижинашвили А.Л. Показатели содержания органических веществ и компоненты карбонатной системы в природных водах в условиях интенсивного антропогенного воздействия // Вестник Санкт-Петербургского университета. 2008. Сер. 4. Вып. 4. С. 90-101.

2. Кремлева Т.А., Хорошавин В.Ю. Особенности ионного состава природных вод малых озер Западной Сибири и их классификация по кислотности и содержанию органического вещества. В сб.: Биогеохимия химических элементов и соединений в природных средах: материалы II Междунар. школы-семинара для молодых исследователей, посвященной памяти проф. В.Б. Ильина. Тюмень, 2016. С. 153-164.

3. Vinçon-Leite B., Casenave C. Modelling eutrophication in lake ecosystems: A review. Sci Total Environ. 2019; 651 (Pt 2):2985-3001. DOI: https://doi.org/10.1016/j.scitotenv.2018.09.320

4. Avnimelech Y. Carbon/nitrogen ratio as a control element in aquaculture systems. Aquaculture. 1999; 176(3-4):227-235. DOI: https://doi.org/10.1016/S0044-8486(99)00085-X

5. Frumin G.T., Gildeeva I.M. Eutrophication of water bodies - A global environmental problem. Russ J Gen Chem. 2014; 84(13):2483-2488. DOI: https://doi.org/10.1134/S1070363214130015

6. Yel E., Ahmetli G. Environmental dilemma of humic substances: being adsorbents and being carcinogens. Int J Environ Sci Dev. 2015; 6(1):73-76. DOI: https://doi.org/10.7763/IJESD.2015.V6.564

7. Ashworth DJ, Alloway BJ. Influence of dissolved organic matter on the solubility of heavy metals in sewage-sludge-amended soils. Commun Soil Sci Plant Anal. 2008; 39:538-550.

8. Chowdhury S., Champagne P., McLellan P.J. Factors influencing formation of trihalomethanes in drinking water: results from multivariate statistical investigation of the Ontario Drinking Water Surveillance Program database. Water Qual Res J Can. 2008; 43(2-3):93-102.

9. Garcia-Villanova R.J., Garcia C., Gomez J.A., et al. Formation, evolution and modeling of trihalomethanes in the drinking water of a town: I. At the municipal treatment utilities. Water Res. 1997; 31(6):1299-1308. DOI: https://doi.org/10.1016/S0043-1354(96)00335-1

10. Weisel C.P., Jo W.K. Ingestion, inhalation, and dermal exposures to chloroform and trichloroethene from tap water. Environ Health Perspect. 1996; 104(1):48-51. DOI: https://doi.org/10.1289/ehp.9610448

11. Kogevinas M., Villanueva C.M., Font-Ribera L., et al. Genotoxic effects in swimmers exposed to disinfection by-products in indoor swimming pools. Environ Health Perspect. 2010; 118(11):1531 - 1537. DOI: https://doi.org/10.1289/ehp.1001959

12. Di Cristo C., Esposito G., Leopardi A. Modelling trihalomethanes formation in water supply systems. Environ Technol. 2013; 34(1-4):61-70.

13. Chowdhury S., Champagne P., McLellan P.J. Models for predicting disinfection byproduct (DBP) formation in drinking waters: a chronological review. Sci Total Environ. 2009; 407(14):4189-4206.

14. Tinkiliç N., Korkmaz H., Özcimder M. Effect of the chlorine dose and total organic carbon level on trihalomethane formation in water. S. Ü. Fen-Edebiyat Fakültesi Fen Dergisi. 2000; 17:15-21.

15. Hassani A.H., Jafari M.A., Torabifar B. Trihalomethanes concentration in different components of water treatment plant and water distribution system in the north of Iran. Int J Environ Res. 2010; 4(4):887-892.