Visions of the future in drinking water microbiology

Abstract

In recent years, drinking water microbiology has seen a rapid emergence in new directions beyond the basic concepts in vogue at the turn of the century. No longer does the laboratory characterize the microbial quality of water by bacterial growth detected on gelatin plates (12) or gas production in lactose bile fermentation tubes (15). Today, the emphasis is on monitoring treatment effectiveness and distribution system integrity, not just focusing on the general bacteriological quality of water leaving the treatment plant. Part of this change in emphasis has resulted from the increasing reports of waterborne outbreaks, largely, a problem in small water systems using minimal treatment of raw surface waters; no treatment of groundwaters or poor protection of water supply in the distribution system. Source water quality has deteriorated in many respects because of man's activities on the watershed. Gone is the notion that the utility can reley on ownership of a watershed and restricted human access to protect source water quality from chemical and fecal contaminants. Wildlife on the watershed are also a substantial reservoir of intestinal pathogens and should not be ignored. These animals are substantial contributors to waterborne outbreaks, for which some causative agents (Giardia, Cryptosporidium) are very disinfectant-resistant. This microbial concern is further complicated by the knowledge that controlling disinfectants react with organic material in raw waters to form various by-products of potential health impact. How effective the disinfection barrier will remain as a result of treatment modifications to minimize by-product formation, is a microbiological concern for the future.