Water is essential to life, but many people do not have access to clean and safe drinking water. Microbiological water quality is mainly based on the concept of fecal indicator bacteria. In general terms, the greatest microbiological risks are associated with ingestion of water that is contaminated with human or animal feces. Wastewater discharges in fresh waters or surface waters are the major sources of fecal microorganisms, including pathogens. [1]

The microbiological quality of drinking water in municipal water distribution systems depends on several factors. Free residual chlorine and/or chloramines are typically used to minimize bacterial recontamination or regrowth in water distribution system. Despite such preventive measures, regrowth of heterotrophic bacteria and opportunistic bacteria in bulk water and biofilm has yet to be controlled completely. No approach has shown complete success in eliminating biofilms or heterotrophic bacteria from bulk water and pipe surfaces. Biofilms can provide shelter for pathogenic bacteria and protect these bacteria from disinfectants. [2]

Monitoring and control technologies are indispensable for the production of safe drinking water. [3]

Various government or non-government organizations have prescribed limits for physico-chemical and microbiological safety parameters of drinking water. The microbiological quality of water is measured by the analysis and enumeration of indicator microorganisms. [2]

The microbiological indicators normated by drinking water law are: total colony count at 220C and 370C, total coliforms, Escherichia coli, Enterococcus, Pseudomonas aeruginosa and Clostridium perfringens. [4]

Total coliforms are Gram negative, oxidase negative, non-sporeforming rods that ferment lactose with gas production. E. coli, a member of Enterobacteriaceae are oxidase negative, catalase positive straight rods that ferment lactose. Cells are positive in the Methyl-Red test, but negative in the Voges-Proskauer assay. E. coli is a natural and essential part of the microbiota in the gut of human and animals. Most E. coli are non-pathogenic.

References

1. Joao P. S. Cabral – Water microbiology. Bacterial pathogens and water – International Journal of Environmental Research and Public Health, 2010.

2. Shakhawat Chowdhury – Heterotrophic bacteria in drinking water distribution system: a review – Environmental Monitoring Assessment, 2012.

3. Margreet Mons / Monitoring and control of drinking water quality – Inventory and evaluation of monitoring technologies for key-parameters, Techneau, 2008.

4. Law 458/2002