WATER QUALITY: "Microbiological Monitoring for Water-Quality Assessment" by Phillip E. Greeson. July 10, 1978 QUALITY OF WATER BRANCH TECHNICAL MEMORANDUM NO. 78.13 Subject: WATER QUALITY: "Microbiological Monitoring for Water- Quality Assessment" by Phillip E. Greeson. For several years, the Quality of Water Branch has emphasized the importance of representative sampling in the production of water- quality data (refer to Quality of Water Branch Technical Memorandums Nos. 73.16, 74.88, 75.25, and 76.17). In practice, however, a notable exception to this emphasis on representative sampling has been the collection of water samples for the determination of indicator bacteria. The reasons for the exception are several, but the primary reason has been the unavailability of a depth-integrating sampler that could be readily sterilized. The problems associated with microbiological sampling and the need for standardization are thoroughly reviewed in the accompanying article by P. E. Greeson of the Quality of Water Branch staff. The article, entitled "Microbiological Monitoring for Water-Quality Assessment," was presented originally at the Seminar on Microbiological Standards for Water that was held at the 1977 Annual Meeting of the American Society for Microbiology. The Quality of Water Branch currently is coordinating efforts to develop a depth-integrating sampler that will meet the requirements for representative microbiological sampling and satisfy other needs as well. We hope to be able to announce the availability of such a sampler within the next few months. Please circulate the attached article as widely as possible to those involved in the collection and interpretation of water- quality data. Thank you. R. J. Pickering Attachment Distribution: SL (2 copies to each District Chief) (l copy to each Regional Hydrologist) Reprinted from Journal of Food Protection VoL 41, No. 4, Pages 309-313 (April, 1978) Copyright 1978, International Association of Milk, Food, and Environmental Sanitarians Microbiological Monitoring for Water-Quality Assessment PHILLIP E. GREESON U.5. Geological Survey National Center, Reston, Virginia 22092 (Received for publication October 26, l977) ABSTRACT The weakest link in the chain of events leading to production of reliable microbiological-monitoring data is a poor or inadequate sample. This results primarily from diversity of environmental conditions from which a sample must be collected. In surface waters, affinity of microbiologlcal organisms for suspended particles necessitates that sampling procedures be designed to collect a representative sample of the water-sediment mixture. The key problem and the challenge to microbiological monitoring is production of a sterilizable, depth-integrating sampler that will accommodate the disparity of sediment distribution as related to variations in depth and cross-section and the changes in streamflow. Until such a sampler has been designed, tested, and made readily available, the data produced in microbiological- monitoring programs involving surface waters can be considered of questionable accuracy, regardless of the notable advances that are taking place in the state-of-the-art of analytical procedures.