CP-1994-14
Guidelines and microbial standards for cistern waters.
Fujioka, Roger S.
Despite the availability of information on how best to design, build, and maintain rainwater cistern systems to ensure adequate water quality, few people follow these guidelines. Studies in Hawaii and elsewhere reveal that most cistern owners have not heard of foul-flush devices, do not clean their water collection/resevoir tanks at regular intervals, and do not disinfect their waters. In addition, many do not use filters. As a result of these practices, most cistern waters don not meet the U.S. Environmental Protection Agency bacteriological standards for drinking water. The poor quality of cistern waters in Hawaii is not due to insufficient education of the owners, to poor sanitary conditions, or to the use of makeshift materials to construct the cistern systems. Worldwide, the quality of most cistern waters has not been determined, as such systems are regarded as private and many countries do not require the monitoring of cistern water quality. However, available information indicates that most cistern waters cannot meet microbial standards. Implementation of guidelines for cistern systems will improve water quality, but waters may never consistently meet EPA drinking-water standards. Most cistern waters can be determined to be free of ontamination from human fecal wstes, and the risks associated with water containing nonhuman sources of indicator bacteria should be less than that of water containing indicators of human origin. Under these conditions, a realistic microbial standard for cistern water of 10 fecal coliforms/100 ml is proposed.