Bacteria Escherichia coli  (E. coli) belong to the family of bacteria Enterobacteriaceae. They are motile, ciliated gram-negative rods measuring 0.5-3.0 µ. These bacteria live in the human large intestine as well as in the digestive tract of warm-blooded animals, and their numbers in fresh feces can be up to 10⁹ cells per gram. In the group of bacteria cola we distinguish two basic types of bacteria: the fecal type Escherichia coli and earth type Aerobacter aerogenes.

Escherichia coli belongs to the "coliform group" as well Citrobacter, Enterobacter and Klebsiella and the remaining 40 genera of the class Proteobacteria. The coliform bacteria count is the number of coliform bacteria colonies in 100 ml of tested water. In accordance with the currently applicable regulation of the Minister of Health of 7 December 2017 on the quality of water intended for human consumption (Journal of Laws 2017, item 2294), according to Annex No. 1, bacteria Escherichia coli, coliforms and a Fecal enterococci cannot be present in drinking water.

In order to exclude potential health risks for recipients and immediately eliminate water contamination, it is necessary to:

• inform recipients about the ban on drinking water,
• determine the source of contamination by testing water from:
• each well separately
• treatment plant points (drainage before filters, after filters, after the treated water tank),
• critical network nodes
• the recipient's draw-off point where contamination was detected
• Immediately after sampling and before obtaining the test results (the results will only be available after 72 hours at the earliest), the disinfection systems at the water treatment plant should be turned on, i.e. UV lamps (voluntary installation) and the chemical disinfection system (mandatory installation), such as the dosing of sodium hypochlorite, chlorine dioxide or chlorine gas.

After receiving positive results of microbiological tests of water at previously established control points, it is recommended to maintain further chemical disinfection, remembering that maintaining proper water quality does not involve a compromise between microbiological and chemical purity of water, i.e. the elimination of dangerous bacteria is more important than only temporarily impaired taste of water caused by the presence of chemical disinfectants, which are very quickly decomposed and disappear, and the taste, smell, turbidity and colour of water acceptable to the consumer return.

coli bacteria in drinking water - download pdf.

Family Legionella contains over 50 species and 70 serotypes of bacteria, but the most common is Legionella Pneumophila (Legionella). This bacterium lives in natural and artificial water reservoirs and with extraordinary ease colonizes water supply networks, cooling towers, water spraying devices, bathing and air conditioning installations. Legionella is facilitated by the presence of calcium, magnesium and ferrous bacteria, which are quite common in the filtration and preparation systems of domestic hot water. This bacterium is part of the so-called bacterial biofilm, which is why the growth of bacteria is facilitated by stagnant hot water, e.g. in water supply systems, dead-end sections of pipes, in heaters, tanks (in particular on the internal walls under deposits of iron compounds or calcium "boiler scale").

In accordance with § 3 of the Regulation of the Minister of Health of 7 December 2017 on the quality of water intended for human consumption (Journal of Laws 2017, item 2294), water is fit for use if it is free from pathogenic microorganisms and parasites in numbers constituting a potential threat to human health, any substances in concentrations constituting a potential threat to human health and does not exhibit aggressive corrosive properties and meets the requirements of:

• microbiological specified in Part A of Annex 1 to the Regulation;
• chemicals specified in Part B of Annex 1 to the Regulation.

In addition to the requirements specified in Parts A and B of Annex No. 1, domestic hot water should meet the requirements specified in Part A of Annex No. 5 to the regulation.

In accordance with the microbiological requirements specified in the above-mentioned annex Legionella may be present in water in amounts below 100 cfu/100 ml of tested water.

Systematic testing for the presence of Legionella should perform:

• companies of entities performing medical activities such as stationary and 24-hour health care services,
• collective housing buildings, e.g. social welfare homes, children's homes,
• public utility buildings in which water and air aerosol is generated during their use, e.g. schools that allow students to use showers after PE lessons or organize summer camps, sports camps, etc. during the holiday period.

Legionella in drinking water - download pdf.