Biological Characteristics Indicators

The wide variety of waterborne diseases is the most important concern about water quality. The pathogens concerned involved several kinds of viruses, protozoa, bacteria, and helminths, that differ hugely in size, structure and composition. This denotes that their survival in the environment and resistance to water treatment processes differs significantly. Therefore, the waterborne transmission of infectious diseases could be controlled effectively through practical and economic techniques. The approach have to be based on protection of the source, fail-safe application of the treatment methods, selection of appropriate treatment techniques, well-protected distribution networks and appropriate quality monitoring. Relatively easy and inexpensive indicator techniques are available for routine monitoring of the microbiological safety of water and the efficiency of treatment processes.

Most reliable results are obtained by high frequency testing for indicator organisms selected for particular purposes. For example, routine-monitoring programmes for drinking water might be based on tests for faecal streptococci, thermo tolerant coliform organisms and Escherichia coli. Under some circumstances, tests for the heterotrophic plate count and coliphages may be included. These tests are simple, inexpensive and yield results in an associative short time. More complicated and costly tests such as those for human viruses and protozoan parasites are needed only for particular purposes, involving research and assessment of the efficiency of treatment procedures.