AWWA ACE63002

This paper briefly discusses the significance of coliforms in water distribution systems. Many scientists feel that these organisms have little or no health significance and consequently are irrelevant, while others feel that coliform presence is indicative of potential problems within the distribution system. This study of various distribution systems and of one system in particular, indicate that finding coliforms within samples collected from the distribution system can be indicative of problems with the treatment processes, distribution system infrastructure, or management of the system. There can be various reasons for the presence of coliforms within distribution systems and when attempting to control coliform failures, a thorough investigation of likely causes is required. The three most likely causes are regrowth within the distribution system, ingress of contaminated water and failure of the treatment plant to remove all coliforms. In order to determine which of these is responsible for the presence of coliforms, a detailed microbiological investigation was performed together with a complete study of the distribution system and treatment plant.