Predicted Impact of Climate Change on Trihalomethanes Formation in Drinking Water Treatment

Maria Valdivia-Garcia,David W Graham,Paul Weir,David Werner

doi:10.1038/s41598-019-46238-0

Maria Valdivia-Garcia, David W Graham + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-46238-0

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Abstract

Quantitative predictions of impacts on public water supplies are essential for planning climate change adaptations. Monitoring data from five full-scale Scottish drinking water treatment plants (DWTPs) showed that significant correlations exist between conditionally carcinogenic trihalomethanes (THMs) levels, water temperature (r = 0.812, p = 0.0013) and dissolved organic carbon (DOC) (r = 0.892, p < 0.0001), respectively. The strong seasonality of these parameters demonstrated how climate can influence THMs formation. We quantified with laboratory experiments the sensitivity of THMs formation to changes in water temperature and DOC concentration. The laboratory data accurately reproduced real-world THM formation in the DWTPs. We then combined these validated relationships with information from the literature about future trends in mean summer temperatures and surface water DOC in the British Isles, to estimate future global warming impacts on THMs formation in DWTPs that use chlorine for disinfection. An increase in mean summer temperatures will likely increase THM formation, with a 1.8 °C temperature increase and 39% THMs increase by 2050 representing our mid-range scenario. Such an increase has major implications to potable water around the world, either an increased health risk or increased water treatment costs to maintain an equivalent quality potable supply.

Highlights

Climatic conditions are changing[1], and this appears to be altering surface water quality with potential public health implications, especially water treatability in drinking water treatment plants (DWTPs)[2,3]
No clear seasonal trends in these indicators of organic carbon quality were apparent in potable water (Fig. 1b) that would correspond to the seasonality observed for the THMs (Fig. 1a), and there were no statistically significant Pearson correlations between monthly averages of the percentage of total organic carbon (TOC) belonging to each of the hydrophobic organic fraction (HPO)/transphilic organic fraction (TPI)/hydrophilic organic fraction (HPI) fraction and total THMs
To exclude the possibility that these correlations observed in full-scale water treatment data are spurious, we separately investigated, with controlled laboratory experiments, the effects of variations in organic carbon concentration and temperature, and potential seasonal changes in organic carbon quality on THMs formation

Summary

Introduction

Climatic conditions are changing[1], and this appears to be altering surface water quality with potential public health implications, especially water treatability in drinking water treatment plants (DWTPs)[2,3]. The dramatic increase in DOC as a THM formation precursor in UK surface waters has implications for drinking water providers, which are challenged to adapt their treatment trains and operations to maintain compliance with drinking water standards into the future[16,17]. In this context, water providers need to anticipate the likely magnitude of further climate change effects in order to effectively plan their investment strategy and adaptations[18]. To the best of our knowledge no study has yet attempted to reproduce seasonal trends in THMs in treatment works based on independent laboratory experiments

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