Biological treatment of public water supplies

A relatively recent development in drinking‐water technology is the use of biological treatment to produce a biologically stable water. Biological stability is achieved by removing biodegradable substances — mainly naturally occurring organic polymers, specific organic micropollutants, and ammonium‐through the action of selected bacteria. The technology involves immobilization and accumulation of the desired bacteria through natural attachment to solid particles as biofilms. The critical review describes the constituents making up biological instability and how their presence adversely affects drinking‐water treatment and the quality of the water supplied to the consumer. Particularly important is a critical analysis of methods to measure the low concentrations of biodegradable organic matter (i.e., less than 1 mg/1). The fundamentals and practice of biological drinking‐water treatment are thoroughly explored. Finally, the future of biological processes in drinking‐water treatment is examined in light of new trends in process technology and regulation of drinking‐water quality.