Koliformitaso

Koliformitaso is a term used in Finnish water quality testing to describe the concentration of coliform bacteria in a water sample. It is an indicator of sanitary quality and potential fecal contamination, helping to assess whether water is safe for use. Coliforms are a broad group of Gram-negative, lactose-fermenting bacteria that includes genera such as Escherichia, Klebsiella, Enterobacter, and Citrobacter. A distinction is commonly made between total coliforms and fecal coliforms, with the latter—especially Escherichia coli—being of particular concern as they more directly indicate recent fecal pollution.

Measurement of koliformitaso is typically reported as colony-forming units per 100 milliliters (CFU/100 ml) or as most probable number per 100 ml (MPN/100 ml). Standard methods often involve membrane filtration or multiple-tube fermentation, followed by incubation and detection of lactose fermentation to identify coliform growth. Results may be subdivided into categories (e.g., total coliforms and fecal coliforms) to provide more specific information about contamination.

Interpretation of the result depends on the context and regulatory framework. A low or undetectable koliformitaso generally indicates good sanitary quality, while detectable coliforms suggest potential contamination and trigger further investigation, water treatment adjustments, or other corrective actions. For drinking water, many guidelines require the absence of fecal coliforms or E. coli in a defined sample volume; for recreational waters, threshold values vary by country and use.

Limitations include that coliforms are indicators rather than direct pathogens and that environmental sources can contribute to counts without indicating fecal contamination. Koliformitaso is typically used alongside other indicators and testing to provide a broader assessment of water safety and quality.