After reading this article you will learn about the microbiological examination of water.
Microbiological examination of water includes both bacteriological and biological examinations. Bacteriological examination of water is necessary for determining its fitness for use for human consumption, and for use in industries such as food processing and dairy, photo film etc.
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Water used for drinking, food processing and dairying should be free from faccal or sewage contamination because micro-organisms causing water-borne disease such at typhoid and paratyphoid fevers, food poisoning, gastroenteritis, cholera, dysentery and diarrhoea are excreted in the faeces of individuals suffering from the disease.
The presence of organisms belonging to the groups such as iron bacteria, sulphur bacteria, sulphate reducing bacteria, slime forming bacterial and gelatin liquefying bacteria is undesirable in water used for drinking purposes, air conditioning, paper manufacture and many other industrial uses. Some of these organisms are known to cause corrosion.
Algae and other microscopic plants and animal-life in water may cause odour and taste problems and also affect suitability of the water for use in various industries. However, this standard includes only microscopic examination and enumeration of these organisms.
The revision incorporates the two amendments issued to IS: 1622-1964 the membrane filter technique for coliforms and faecal streptococci, test for feecal coliforms, delayed incubation method for total coliforms and spore staining technique for Clostridium welchii. This standard prescribes laboratory preparation of culture media.
However, dehydrated media commercially available may also be employed. Since preparation of culture media and solutions is a critical aspect of water quality testing, the date of receipt of media (dehydrated powder medium) and the date of opening should be recorded. Practically 125 bottles should be purchased to ensure minimum exposure.
When a new log of media is used, the contents should be tested for expected performance. It should be stored in a cool, dry place away from sunlight.