Predicting the effect of climate change on THM formation

Climate change will change every aspect of our lives, including our water supply. Predicting what effects may occur is imperative, and quantitative data is necessary to understand the extent and how big adaptations will need to be.

STREAM researcher Maria Valdivia-Garcia investigated one such effect – that of carcinogenic trihalomethanes (THMs). THMs form when chlorine and other disinfectants used in water interact with naturally occurring organic and inorganic matter in water. THMs can cause many health issues, including cancer and reproductive issues, so higher levels would mean a higher health risk. 

Monitoring data was collected from five full-scale Scottish drinking water treatment plants. The data showed a significant correlation between THMs and water temperature, and a separate significant correlation between THMs and dissolved organic carbon concentration. These two correlations were clearly seasonal, which demonstrates that climate can influence THMs formation. 

Laboratory tests were done to quantify the sensitivity of THMs formation to water temperature and dissolved organic carbon concentration. The results of these experiments reproduced the real-world data from the treatment plants, which implies that the quantitative data from the laboratory tests was accurate to real-world conditions. These tests were then combined with existing information about future trends in mean summer temperatures and surface water dissolved organic carbon in the British Isles, so we can estimate global warming’s impact on THMs formation. 

An increase in mean summer temperature will likely increase THMs formation. The mid-range scenario had a 1.8°C temperature increase by 2050, and a 39% THMs formation increase. This escalation would have major implications to potable water around the world. THMs pose a real health risk, which means such an increase would require either accepting the higher risk to human health, or a rise in water treatment costs to maintain the current quality in the potable water supply. If water companies begin to prepare now, lower cost methods could be investigated and put into practice before it becomes a public health concern. 

Full article: Predicted Impact of Climate Change on Trihalomethanes Formation in Drinking Water Treatment, M Valdivia-Garcia, P Weir, DW Graham, D Werner, Scientific Reports