Regulated and emerging disinfection by-products in recycled waters

Disinfection is an integral component of water treatment performed daily on large volumes of water worldwide. Chemical disinfection may result in the unintended production of disinfectant by-products (DBPs) due to reactions between disinfectants and natural organic matter present in the source water. Due to their potential toxicity, levels of DBPs have been strictly regulated in drinking waters for many years. With water reuse now becoming more common around the world DBPs are increasingly becoming a concern in recycled waters, where a much larger amount and variety of compounds may be formed due to a higher abundance and diversity of organic material in the source waters. Regulation of DBPs in recycled waters is limited; generally, drinking water regulations are applied in place of specific guidelines for recycled waters. Such regulations are set for only 11, commonly observed, compounds of the 600+ that may, potentially, be found. In this review an overview of current research in this area is provided, the types of compounds that have been observed, methods for their analysis and possible regulation are also discussed. Through this review it is evident that there is a knowledge gap for the occurrence of DBPs in recycled waters, especially when comparing this information to that available for drinking waters. The concentrations of DBPs observed in recycled waters are seen to be higher than those in drinking water, though still within potable threshold limits. It is clear that there is a need for the analysis and understanding of a larger suite of compounds in recycled waters, as these will most likely be the source of future, global renewable water.