Correlation of Coliform Growth Response With Other Water Quality Parameters

bacteria has also been shown to interfere with the detection of coliform bacteria. Further, and perhaps most important, members of the total coliform group of bacteria themselves have been implicated in regrowth problems, thus $ving rise to major compliance violations. Bacterial regrowth is affected by a variety of factors. The temperature of the water has been shown to play a major role in bacterial regrowth. An increase in heterotrophic plate count (HPC) organisms has been associated with increasing temperatures following a late spring-summer-autumn sequence in utilities experiencing coliform problems.3 The type of water treatment that is employed by a utility may have a direct impact on microbial growth. It has been demonstrated that the use of ozone in the treatment of water with high humic content, without the subsequent removal of the oxidation products, increases microbial growth in the distribution system.4 This finding is of particular interest because of the proposed increased use of ozonation by water utilities. The incorporation of biological unit processes in water treatment can also affect the nutrient status of the product water. Biological treatment of drinking water, although rarely used in the United States, is common in Europe where the biooxidation of organic matter and ammonia has been demonstrated to be beneficial and cost-efficient. The velocity of water flowing through the mains is an important factor influencing microbial colonization and growth in the distribution system. Pipe sectionswith high water velocities tend to limit microbial protection and reduce sediment accumulation, thus minimizing nutrient entrap ment and protection from exposure to the disinfectant. Conversely, areas of slow flow and dead-end locations have been statistically correlated with water quality deterioration? The presence of iron tubercles has also been associated with microbial growth, especially with colonization by coliform bacteria.6 The maintenance of an adequate disinfectant residual is universally recom