WATER QUALITY: "Microbiological Monitoring for Water-Quality Assessment" by Phillip E. Greeson.

                                                   July 10, 1978


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


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


U.5. Geological Survey
National Center, Reston, Virginia 22092

(Received for publication October 26, l977) 


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.