AWWA JAW17313

This article emphasizes the importance of enumerating injured coliforms in drinking water. Sources of injury to indicator bacteria resulting from a variety of sources including chlorine and other disinfectants, heat, freezing, sunlight, pH, transition metals such as copper, antagonistic plate count organisms, and interactions of standard plate count bacteria are reviewed. Factors that can influence the extent or severity of injury include time and temperature of exposure, strain of organism, physiological state, concentration of nutrients, neutralization technique, diluent, and method of enumeration are discussed. The authors describe methods for enumerating stressed coliforms and recommend performing parallel coliform analyses using mEndo and m-T7 agars to assess the extent of occurrence of injured coliforms. Includes 105 references, figures.