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Project Background

All drinking water supplies contain some background organic matter. Usually these organics result from naturally-occurring plant product or their derivatives. Thus, we call this material natural organic matter (NOM). Until the early 1970s this NOM was considered nothing more than a benign nuisance; NOM was known to consume chemical additives or foul granular activated carbon adsorbents.

In the early 1970s NOM became a focus of concern as its central role in the formation of potentially carcinogenic disinfection byproducts (DBPs) was recognized. DBPs, including the trihalomethanes (THMs) and haloacetic acids (HAAs) were found to result from the reaction of chlorine with NOM. Alternative disinfectants were explored, but these also were found to produce potentially harmful DBPs.

Starting in the late 1970s, regulations were established by the US EPA with the intention of minimizing these compounds. These regulations accompanied extensive occurrence studies (e.g., the Information Collection Rule or ICR) and stimulated the development of in-plant control strategies. While somewhat successful, these strategies have not completely solved the DBP problem. In addition, it is recognized that NOM contributes to the growth of bacteria in distribution systems. Biodegradable dissolved organic matter (BDOM) in raw waters is supplemented by newly formed BDOM in treated waters to provide stimulus for microbial growth. Different watersheds are known to result in waters with different levels of BDOM, however the factors that lead to these differences are not well understood. It is now clear that more attention must be paid to the upstream processes that give rise to NOM in raw waters.

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