Historically drinking water utilities in the United States (U.S.) have played a major role in protecting public health through the reduction of waterborne disease. These reductions in waterborne disease out-breaks were brought about by the use of sand filtration, disinfection and the application of drinking water standards. Coincident with the passage of the SDWA of 1974, it was discovered that chloroform was a disinfection by-product (DBP) resulting from the interaction of chlorine with natural organic matter in water. Chloroform is one of a class of compounds called trihalomethanes. This finding posed a serious dilemma because it raised the possibility that chemical disinfection, which clearly reduced the risk of infectious disease, might also result in the formation of potentially harmful chemical by-products. Although disinfection of public drinking water had dramatically reduced outbreaks of diseases attributable to waterborne pathogens, the identification of chloroform in drinking water raised questions about possible health risks associated with these exposures. In the United States, since 1974, additional DBPs have been identified and concerns have intensified about health risks resulting from exposures to them. Although a causal relationship between DBP exposures and these health risks has not been conclusively established, risk managers have responded, in the interest of protecting public health, by developing alternative treatment systems and issuing rules and regulations designed to maintain protective levels of disinfection while reducing potentially harmful levels of DBPs. In 1981, the USEPA issued a report intended to summarize the state-of-the-art regarding the control of disinfection by-products in drinking water. However, EPAs current drinking water research program is more sophisticated than it was twenty years ago. For example, when the treatment technology manual was published in 1981, it reported primarily on treatment oriented re-search.
Twenty years later, the technology research program includes source water protection, treatment technology and distribution system studies. The research also reflects a concern over balancing the risks of potential carcinogenic exposure against the risks from microbial infection.This document is intended to summarize the research that has been conducted in technology research by EPA since the publication of the 1981 treatment technology document.