Testing laboratory for microbiological drinking water tests
Testing laboratory for microbiological drinking water tests
This laboratory tests drinking water samples for the presence of Escherichia coli and enterococci. It also determines the aerobic, mesophilic total viable count. All tests follow procedures set out in the Swiss Food Compendium.
Detection of aerobic, mesophilic bacteria
Cast iron plate procedure:
1 ml water is placed in a sterile petri dish. It is then mixed with liquid agar and cooled to 45 °C. Once the agar has frozen, the plates are incubated. The next step is to count the colonies of bacteria which have subsequently developed.
Identification of Escherichia coli and enterococci
Membrane filter testing procedure:
Using sterile filtration equipment, 100 ml water is passed through a membrane filter (pores of 0.45 mm in diameter). The micro-organisms are retained in the filter, which is then placed in a solid medium and incubated. The next step is to count the number of colonies (cell communities) which have grown in the filter.