Publisher's Synopsis
The validity of monthly bacterial compliance sampling results is critical in determining compliance with the Total Coliform Rule (TCR) and determining the need for changing disinfection strategies or other mitigation techniques. Consequently, the protocol used in sample site selection and sample collection and handling can impact the test results. Although significant resources have been expended nationally in rule and method development, utilities have had very little guidance for sampling siting and collection protocols. The objective of the project was to develop scientifically based approaches in selecting sampling locations and develop guidelines for utilities on collection and handling of routine bacteriological samples from the distribution system. The initial three phases involved a summary of current regulations and guidance documents; tailored questionnaires to 15 state regulatory agencies and to 20 utilities throughout the United States representing a variety of water sources and qualities; a comprehensive literature review identifying critical factors within distribution systems that affect bacterial monitoring results; and characterization of the participating utilities? distribution systems. The subsequent project phases included a laboratory pipe loop study and a field-monitoring program at four U.S. drinking water utilities, and incorporated comprehensive data evaluations and statistical analyses to assess several variables associated with bacterial monitoring and the development of sampling protocols. Finally, a guidance manual was written for use by drinking water utilities in planning and implementing bacterial water quality monitoring programs. All critical factors must be considered in monitoring bacterial water quality. A successful monitoring program correctly detects microbial contamination in the distribution system when it occurs, and provides the necessary information to mitigate the problem. High HPCs observed from a long copper connection could be a cumulative effect of the length of the service line and the frequency of use of the sampling port. Absences of coliforms as measured by routine assay do not necessarily ensure a microbially safe water, as coliforms could be present in an ?injured? form, which may carry a regrowth potential. In the field study, poorer water quality (i.e., higher HPCs) occurred (1) in an area of low demand compared to a nearby area of higher demand, (2) at a point served by old cast iron pipes when compared to a location in the same district served by newer pipe materials, (3) at a location away from a system reservoir compared to a location at the reservoir, and (4) typically at locations with low chlorine residual disinfectant. There were no significant differences in measured microbial water quality in samples collected after flushing only, flushing and flaming, and flushing, flaming, and disinfecting. Changing the order of flaming and disinfection also did not affect results. Originally published by AwwaRF for its subscribers in 2004. This publication can be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below
