Assessment of the microbial integrity, sensu G.S. Wilson, of piped and bottled drinking water in the condition as ingested.
The second half of the 20th century witnessed substantial progress in the assurance and verification of microbiological integrity, i.e., safety and sensory quality, of drinking water. Enteropathogenic agents, such as particular viruses and protozoa, not previously identified as transmitted by industrially provided water supplies, were demonstrated to cause disease outbreaks, when ingested with piped water. The potential harm posed by carry-over of orally toxic metabolites of organisms, producing 'algal' (cyanophytic) blooms, was considered. In addition, earlier observations on the colonization of attenuated drinking water bodies by a variety of oligotrophic Gram-negative bacteria were confirmed and extended. This new evidence called for updating both water purification technologies and analytical methodology, serving to verify that goals had been attained. For the former purpose, the hazard analysis empowering control of critical practices (HACCP) strategy, introduced about 1960 in industrial food processing, was successfully adopted. Elimination, devitalization or barrier technologies for the more recently identified water-borne pathogens were elaborated, taking account of the hazard of production of chlorinated compounds with alleged adverse health effects. Biofilm formation throughout water distribution networks was brought under control by strict limitation of concentrations of compounds, assimilable by oligotrophic bacteria. Upon acknowledging that direct detection tests for pathogens were futile, because of their most sporadic and erratic distribution, Schardinger's marker organism concept was anew embraced, rigorously revised and substantially enlarged. Misleading designations, like searches for 'faecal coliforms' were replaced by boundary testing for Escherichia coli and appropriate Enterococcus spp. In addition, though still to be perfected, detection protocols for relevant bacteriophages or index viruses and, to a certain extent, also for spores of aerobic and anaerobic sporing rods were also elaborated. In all monitoring account was taken of sublethally injured target organisms, surviving purification technologies, though not deprived of their ecological significance. A need remains for a rigorously standardized operating procedure (SOP) for colony counts of psychrotrophic, oligotrophic Gram-negative rod-shaped bacteria ('heterotrophic plate count'), which constitute a useful criterion of indicator value. As in the contemporary HACCP approach to food safety, guidelines for assessing success or failure in control of integrity (Water Safety Objectives) were empirically elaborated. These rely on surveys on water samples, originating from drinking water supplies, previously verified as complying with longitudinally integrated HACCP-based purification technologies. Structured Academic dissemination of these innovations, through professional microbiologists to operator and executive levels, is recommended. Web based Distance Learning MSc Programmes, like the one, since the academic year 2003-2004, offered by the University of Hertfordshire, Hatfield, UK, may contribute to such endeavours. Though the complete Course is centered around Food Safety, the Modules in-Residence Practicals and Science and Technology of Drinking Water can be studied as an entity while being employed.
Mossel
David A A
DA
Eijkman Foundation for Postgraduate Education and Research in Public Health Microbiology of Food and Drinking Water at Utrecht University, P.O. Box 6024, 3503 PA Utrecht, The Netherlands.
Struijk
Corry B
CB
D001419:Bacteria / Q000302:isolation & purification*; D003257:Consumer Product Safety; D004784:Environmental Monitoring / Q000379:methods; D006801:Humans; D014871:Water Microbiology; D014881:Water Supply / Q000032:analysis / Q000592:standards*