Microbiological and chemical changes in drinking water systems caused by increased temperature during the summer months
Abstract
As part of a continuing effort to diminish the incidence of persistent microbiological and chemical violations, the Missouri Department of Natural Resources, Division of Public Water Supplies, has enlisted the assistance of eighty-three Missouri water suppliers in a comprehensive study of chemical and microbiological problems in public drinking water systems. These studies were initiated, in part, because there are some 950 public groundwater supplies in Missouri, about 75 percent of the total, which do not disinfect. Most of these supplies serve small rural communities where the neighboring farm houses and stock-watering troughs increase the possibility of microbial contamination due to cross-connections and back-siphonage. In many instances, Missouri's rural areas are served by regional water systems where water is pumped from system to system to system for miles without rechlorination. The effect of long residence times on chlorine residuals and microbiological growth is of concern in such systems. Sti11 other water systems are converting from hypochlorous acid to chloramine residuals as a means for controlling trihalomethane formation. The effect of this change on the total bacterial population in the distribution system is of special interest. Finally, Missouri has a pool of about 300 community public water supplies which tend to drift in and out of compliance with microbiological standards. Better microbiological methodologies are sought for these systems which will better identify the causes of persistent violations. The present studies were undertaken to help the Missouri Department of Natural Resources to formulate policies for bringing these supplies into compliance.