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Findings from AwwaRF Project 2676 - Sample Collection Procedures and Locations for BacterialCompliance Monitoring are summarized and presented in this paper. The surveys of U.S. regulatoryagencies and utilities throughout the United States indicated that there was a general lack of specificguidance in regard to selecting sampling points within distribution systems, and significantvariations exist in sample site selection, sample tap configurations, and sample collectionprocedures. The critical factors affecting microbial sampling results are disinfection residual,materials of construction, service lines and hydraulic conditions, and sample collection andanalytical methods. Other significant variables include temperature, corrosion and sedimentaccumulation, and presence of nutrients.As part of the laboratory testing phase of this project, two parallel laboratory pipe loops weredesigned and constructed to evaluate bacterial counts in unlined cast-iron and PVC pipe materials.Specific sampling procedures were studied, including flushing, flaming, and disinfectantapplications. Conclusions from the pipe loop study indicate that dedicated and non-threaded(soldered) sampling ports accurately reflect bulk water bacterial levels when compared to threadedand plastic sampling taps, and that hydraulic conditions in household copper service and in dead-endsegments 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 onlocational aspects of bacterial monitoring. Sampling sites were located within high and low demandareas of the distribution system, close to and away from reservoirs and storage tanks, before andafter booster chlorination, in areas of predominately high and low chlorine residual, and in areascontaining specific pipe materials (old cast-iron, PVC, and AC). Dedicated sampling stations werecompared to residential and commercial customer taps. Both interior and exterior residential andcommercial customer taps were also evaluated. The results of the laboratory pipe loopinvestigations and field studies are presented in this paper. Includes tables, figures.

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Edition: Vol. - No. Published: 06/16/2002 Number of Pages: 14File Size: 1 file , 340 KB