AWWA WQTC52898

Despite significant improvements over the past ten years in the quality ofwater leaving treatment facilities, the detection of coliform organisms in distribution systems still causes problems for water suppliers. Determining the cause of coliform failuresin distribution systems is difficult. Much of the research in the past has concentrated on the survival and/or growth of coliform organisms within biofilms on pipe walls. However,much of this work has been laboratory based and has not been proven in the field. There are a number of factors that can affect the quality of water in distribution systems, includingthe condition of the assets, network activity, integrity of treated water reservoirs, and the condition of the customers' plumbing. This paper presents the results of studies carried out over the past two years which take a holistic approach to determining the causes of coliform failures in distribution systems by considering all the "risk" factors in conjunction with the use of network modeling techniques. Includes 19 references, figures.