The Effect of Different Boiling and Filtering Devices on the Concentration of Disinfection By-Products in Tap Water

Disinfection by-products (DBPs) are ubiquitous contaminants in tap drinking water with the potential to produce adverse health effects. Filtering and boiling tap water can lead to changes in the DBP concentrations and modify the exposure through ingestion. Changes in the concentration of 4 individual trihalomethanes (THM4) (chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM)), MX, and bromate were tested when boiling and filtering high bromine-containing tap water from Barcelona. For filtering, we used a pitcher-type filter and a household reverse osmosis filter; for boiling, an electric kettle, a saucepan, and a microwave were used. Samples were taken before and after each treatment to determine the change in the DBP concentration. pH, conductivity, and free/total chlorine were also measured. A large decrease of THM4 (from 48% to 97%) and MX concentrations was observed for all experiments. Bromine-containing trihalomethanes were mostly eliminated when filtering while chloroform when boiling. There was a large decrease in the concentration of bromate with reverse osmosis, but there was a little effect in the other experiments. These findings suggest that the exposure to THM4 and MX through ingestion is reduced when using these household appliances, while the decrease of bromate is device dependent. This needs to be considered in the exposure assessment of the epidemiological studies. 1. Introduction Safe drinking water is a vital need for humans. The access to drinking water is becoming more constrained worldwide, by both growing demand and more erratic availability. Disinfection is necessary to have safe drinking water. However, undesired disinfection by-products (DBPs) are formed by reaction of one disinfectant, or a mixture of them, with organic matter. DBPs are ubiquitous contaminants of concern in tap water. Chlorine is the most frequently used disinfectant worldwide, and trihalomethanes (THMs) are usually the most prevalent by-products of chlorination. The four common THMs, depending either on the chlorine or the bromine incorporation, are chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM). THM4 stands for the sum concentration of the 4 individual species of TMHs. Long-term exposure to disinfection by-products has been associated with an increased risk of bladder cancer [1]. Bromate is a DBP formed by ozonation of water containing bromide. Bromate induces neurotoxicity in adults, and some evidences show a possible effect on thyroid hormone levels [2]. Bromate