FIELD AND LABORATORY TESTING TO IDENTIFY CRITICAL FACTORS IN BACTERIAL COMPLIANCE MONITORING

摘要

Findings from AwwaRF Project 2676 - Sample Collection Procedures and Locations for Bacterial Compliance Monitoring are summarized and presented in this paper. The surveys of U.S. regulatory agencies and utilities throughout the United States indicated that there was a general lack of specific guidance in regard to selecting sampling points within distribution systems, and significant variations exist in sample site selection, sample tap configurations, and sample collection procedures. The critical factors affecting microbial sampling results are disinfection residual, materials of construction, service lines and hydraulic conditions, and sample collection and analytical methods. Other significant variables include temperature, corrosion and sediment accumulation, and presence of nutrients.rnAs part of the laboratory testing phase of this project, two parallel laboratory pipe loops were designed and constructed to evaluate bacterial counts in unlined cast-iron and PVC pipe materials. Specific sampling procedures were studied, including flushing, flaming, and disinfectant applications. Conclusions from the pipe loop study indicate that dedicated and non-threaded (soldered) sampling ports accurately reflect bulk water bacterial levels when compared to threaded and plastic sampling taps, and that hydraulic conditions in household copper service and in dead-end segments of the distribution system can have significant influences on heterotrophic bacteria levels. A field study conducted at four drinking water utilities throughout the United States focused on locational aspects of bacterial monitoring. Sampling sites were located within high and low demand