Total Viable Count

The total bacterial count is a nonspecific size of the microbiological analysis of drinking water by the drinking water regulations. It indicates the number of colonies of microorganisms formed on a standardized for this purpose agar culture medium over 48 hours at a controlled incubation temperature of 22 and 36 ° C when dispersed 1 ml of the water sample on or in the soil.

The medium is designed to the widest possible selection of various microbial species ( active stages as well as resting stages, not just "seeds" ) to be cultivated, which can use a variety of organic substances in the environment as food. Thus, they are indicators of such " organic pollution " in the water.

The two incubation temperatures (22 ° C and 36 ° C) are applied, because in the one culture approach ( at 22 ° C) will prefer the microbial species that live freely in the environment, in other cultural approach ( at 37 ° C) such that are associated with faeces from the intestine of warm-blooded animals. Conclusions are drawn on the proportion of registered fecal microorganisms from the difference of the two results.

All microorganisms present in a sample collected - With this method, not - as the name may suggest the measurand " bioburden ". This is evident from the fact that at different incubation temperatures, different values ​​are obtained. Even with other methods is not possible. Because there is no culture conditions (including composition of the culture medium, incubation temperature, Bebrütungsatmosphäre ), under which multiply all existing in a natural habitat microorganisms, provided the habitat - as usually - contains a biological community with a wide range of physiologically diverse microorganisms.

After the German Drinking Water Ordinance, a limit of 100 cfu / ml ( " colony-forming units per milliliter " ) for line- run drinking water from wells and 1,000 CFU / ml is considered for temporary aufbewahrtes in tanks of drinking water.

• Water quality
• Microbiology