How do different species of Disinfection By-Products compare to water quality guidelines?

Water treatment is a critical component to ensure safe drinking water provisions for Canadians. In particular, chlorine is commonly used to disinfect drinking water supplies. However, chlorine can react with dissolved organic carbon (DOC) to form carcinogenic disinfection by-products (DBPs). Although thousands of different types of DBPs can form (ranging in abundance and toxicity) it is too difficult to measure, let alone regulate, every single compound. For that reason, drinking water guidelines generally use the total concentration of two groups (trihalomethanes and haloacetic acids), encompassing various combinations of carbon, chlorine, and bromine (termed DBP species). However, these guidelines are chemically confusing (adding up different concentrations on a weight basis rather than a molar basis) and group together a number of different species with different levels of health concerns.

This poster will start a conversation about DBP water quality guidelines. First, we provide a tool to easily calculate and convert DBP guideline values to various DBP molar concentrations. Second, we compare DBP data collected from various lakes (covering 15º of latitude, from the IISD-Experimental Lakes Area in Ontario, to the Northwest Territories) to examine how differing amounts and mixtures of DOC result in changes in the relative formation of various DBP species. Finally, we discuss how different species may vary in toxicity. These components all help to continue a conversation that discusses DBP formation, risk, and water quality guidelines.