AWWA WQTC62487

Small water systems (population 500-9,999), in many cases, have limited resources and may not be able to employ modeling software and other advanced technologies to locate points with the highest disinfection byproduct (DBP) concentrations. Nonetheless, many small systems will be required to perform these evaluations in the near future. More information on the variation of DBP levels in distribution systems is needed in order to aid small systems in performing these evaluations. With this in mind, the objectives of this research were to: determine DBP level trends throughout the distribution system in the small water systems chosen for the study; determine whether simple water quality data and system parameters, such as free chlorine residual and distance from the distribution inlet can be used as indicators of DBP levels in the distribution system; and, provide the operators of the small water systems that participated in the study with system specific information and data that may aid them in preparing to perform an IDSE and comply with future regulations. Three drinking water utilities were selected for participation in this study. The criteria used to select the participants was as follows: System Size, this study was intended to aid small water systems in understanding and complying with upcoming DBP regulations and, therefore, systems serving a population of less than 10,000 people were selected for this study; DBP Concentration, systems with significant DBP levels were chosen to participate in this study; and, location and relationship, systems located in close proximity to Penn State Harrisburg, and those that had a previously established relationship with the University were preferable. These qualities made communication and project startup more convenient and productive. The system characteristics were as follows: System A - the plant servicing system A is a 1.2 million gallon per day (MGD) plant, uses surface water as its raw water supply, uses chlorine gas as a disinfectant, and population served by the utility is approximately 4,300 (Sample point 6, the most remote location included in the sampling campaign, is currently used as the maximum residence time sample point); System B - serves a population of approximately 2,100 people, produces approximately 450,000 gallons per day, uses surface water as its raw water source and chlorine gas as the disinfectant (Location 4 is currently used as the maximum residence time sample point); and, System C - serves a population of approximately 2,300 people, uses surface water as its raw water supply, chlorine gas is used as the disinfectant in the water plant which produces approximately 400,000 gallons per day (the point currently used as the maximum residence time location for the system is a blow-off point). Because many small systems do not have an extensive DBP data history or hydraulic modeling capabilities the only tool that was used when selecting sampling points for this study was distribution system maps. At each point chosen for sampling, analysis was performed to determine the trihalomethane (THM) and Haloacetic Acid (HAA) concentrations at that point. The free chlorine residual, total chlorine residual, water temperature, and pH were measured as well. The samples were analyzed according to the following methods: THMs - USEPA method 551.1 (USEPA, 1995); HAAs - USEPA method 552.3 (USEPA, 1995); Total Chlorine Residual - HACH method 8167 based on Standard Method 4500-Cl G; Free Chlorine Residual - HACH method 8021 based on Standard Method 4500-Cl G; and, pH and Temperature - portable HACH Sension1. Includes 4 references, figures.