AWWA JAW10248 ✓ Most Recent

In this study the two separate and distinct water distribution systems of Salem and Beverly, Massachusetts are examined, using standard plate count (SPC) and membrane filtration, to determine if certain aspects of the drinking water standards employed control adequately the quality of finished water in the distribution system. A variety of organisms was isolated from both distribution systems. Organisms identified included coliform, streptococcus, and yeast. These findings suggest that such organisms have established an ecosystem within the pipe network. The SPC exhibited no relationship with coliform count when the SPC was less than 50 organisms/mL. The SPC was not dependent on low-level turbidity and varied with respect to free chlorine residuals. The frequency of coliform isolation was independent of turbidity and free chlorine. Specifically, encapsulated coliforms which gave typical coliform results exhibited the ability to survive a free chlorine residual of 0.2 mg/L or more. A polysaccharide capsular coat, known as glycocalyx, was a major factor in these results. Includes 49 references, tables. See more