5th International Conference on Rain Water Cistern Systems
"Rainwater Catchment for Future Generations"
Keelung, Taiwan, R.O.C. - August 1991

Section 2: Catchment Water Quality Regulation

Page 80

Microbial Levels in Cistern Systems: Acceptable or Unacceptable

Dennis J. Lye
Environmental Protection Agency, USA

Abstract

The acceptance of cistern systems as a source of potable water and as a possible source for non-domestic use is dependent upon the quality maintained within the entire system. Microbial levels measured within a cistern system are reliable indicators of water quality and of deteriorations that may give rise to offensive odors and tastes. The number of microorganisms commonly found within most contemporary cistern systems is usually lower than surrounding surface waters but these microbial levels may still be unacceptable for many alternative uses. Our laboratory is studying the bacterial populations growing and residing within cistern systems. During periods of rainfall collection and heavy usage, the microbial populations of single-chamber cistern systems do not decrease significantly during subsequent storage (self-purify). The storage of rain water in cistern systems may actually.be conducive to the growth of certain bacterial strains in numbers beyond those found in natural water sources. Our studies have shown that certain types of maintenance of individual, single-chamber catchment systems may actually increase the levels of certain microbial strains when compared to similar systems receiving no.treatment at all. More work is required to identify those parameters necessary for the proper storage and maintenance of high quality cistern water.

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