Parameter overview
Here you will find detailed information on the key parameters we use to assess water quality. Our analysis methods are state of the art to ensure precise and reliable results.
In addition, other parameters are examined if certain requirements are placed on the water.
Total colony count
Bacteria that are predominantly detected at an incubation temperature of 22°C are usually found in the environment, water, and soil (psychrophiles).
Bacteria that grow at an incubation temperature of 36°C are increasingly found in the intestines of living organisms (mesophiles) and can therefore be assigned to possible fecal contamination.
Examination procedure
Drinking water ordinance §15 paragraph 1c*
Procedure
To determine the total colony count, the sample is incubated at 22°C and 36°C in an agar culture medium and then analyzed.
Limit value/requirement
Depending on use, usually 100 cfu/ml
Causes for overruns
- poor general hygienic condition of the system
- influence of tapping fittings
- stagnation in the pipe network
- Insufficient treatment processes and disinfection measures
Measures in the event of exceedances
- inform users / do not dispense the water as drinking water
- flush pipes
- further investigation of the drinking water system
- no supply to consumers
Coliform bacteria
Coliform bacteria are indicator parameters and can indicate both faecal and non-faecal contamination.
These include the following genera: Citrobacter, Enterobacter, Escherichia and Klebsiella
Coliform bacteria do not multiply in the drinking water pipe network can survive for an extended period and can therefore be detected over a longer timeframe.
Examination procedure
DIN EN ISO 9308-2*
(in the current version)
Implementation
Für die Bestimmung von Coliformen Bakterien wird das Alternativverfahren Colilert Quantitray von IDEXX genutzt.
Limit value/requirement
0 cfu/100 ml
Causes for exceedances
- contamination usually comes from outside the drinking water installation
- Biofilm-forming coliform bacteria are difficult to remove. Detection quantity can increase when biofilm is broken up
Measures in the event of exceedances
- inform users / do not dispense the water as drinking water
- flush pipes
- further examination of the drinking water system
- disinfection
- no supply to consumers
Escherichia coli
Escherichia coli (E. coli) serves as an indicator parameter for the detection of fecal contamination and pathogenic germs.
E. coli belongs to the genus of coliform bacteria and, like these, does not multiply in the drinking water pipe network, but can survive for a longer period and can therefore be detected over a longer period.
Examination procedure
DIN EN ISO 9308-2*
(in the current version)
Procedure
The alternative method Colilert Quanti-Tray from IDEXX is used for the determination of Escherichia coli (E. coli).
Limit value/requirement
0 cfu/100 ml
Causes of exceedances
- contamination usually comes from outside the drinking water installation
- Biofilm-forming coliform bacteria are difficult to remove. Detection quantity can increase when biofilm is broken up
Measures in the event of exceedances
- inform users / do not dispense the water as drinking water
- flush pipes
- further examination of the drinking water system
- disinfection
- no supply to consumers
Intestinal enterococci
Enterococci are faecal streptococci, which also serve as faecal indicators. Just like coliform bacteria, they do not multiply in the drinking water pipe network. However, they can survive over a longer phase and can therefore be detected for longer than coliform bacteria.
Examination procedure
DIN EN ISO 7899-2*
(in the current version)
Procedure
For the determination of enterococci, the sample is filtered, and the membrane filter is then incubated at 36°C on a special agar culture medium and then analyzed.
Limit value/requirement
0 cfu/100 ml
Reasons for exceeding the limit
- they are more resistant to environmental influences and indicate contamination from outside the drinking water installation that occurred some time ago
Measures in the event of exceedances
- inform user / do not dispense water as drinking water
- flush pipes
- further investigation of the drinking water system
- no supply to consumers
Legionella spec.
Legionella are bacteria found in the environment, especially in water sources such as rivers, lakes, and ponds. However, some species of Legionella can also thrive in artificial water systems, such as those found in buildings, air conditioning systems, hot water systems and other industrial facilities.
The most well-known type of this bacteria is Legionella pneumophila, which can be responsible for a serious lung infection known as Legionnaires’ disease. This disease can be caused by inhaling fine droplets of water or aerosols contaminated with the bacteria.
It is important to monitor and control Legionella in water systems to minimise the risk of Legionella infections, especially in facilities such as hospitals, hotels, and other public buildings where people may be present. There are guidelines and regulations for the control of Legionella in certain water systems to protect public health.
Examination procedure
DIN EN ISO 11731:2019-03 Water quality – Legionella count
Procedure
For the determination of Legionella spec., the methods membrane filtration and direct preparation are used. The incubation time is 10 days at 36°C.
In membrane filtration, the water sample is filtered through a special membrane to concentrate bacteria and placed on a special culture medium that promotes the multiplication of Legionella. In direct preparation, the water sample is placed directly on a suitable culture medium without prior filtration.
Limit value / requirement
The limit values vary depending on the area of application. In the field of drinking water, the limit value is referred to as the technical measure value. This value defines the point at which countermeasures must be taken to eliminate the contamination, in accordance with the Drinking Water Ordinance at 100 cfu / 100 ml. In bathing areas with nebulization systems, where aerosol formation occurs, the limit value is 0 cfu/100 ml.
Causes for overruns
- incorrect temperature range (25 to 45°C)
- stagnant water in pipes and storage tanks
- biofilms, deposits, and sediments in hot water systems
- lack of maintenance, defective circulation
Measures in the event of exceedances
- inform users / restriction of supply to persons depends on the level of contamination
- further investigation of the drinking water system
- disinfection
- flush pipes
Pseudomonas aeruginosa
Pseudomonas aeruginosa is a gram-negative, rod-shaped bacterium that is widespread in the environment. Normally, Pseudomonas aeruginosa does not cause illness in healthy people. However, under certain circumstances, Pseudomonas aeruginosa can directly cause disease, especially in people with weakened immune systems or other health problems.
Environmental spread Pseudomonas aeruginosa is found in various environments, including soil, water, and hospital environments. It can survive in moist environments, such as in pipes, pools or on surfaces.
Opportunistic pathogen It is an opportunistic pathogen that does not normally cause disease in healthy people. However, it can cause infections in people with weakened immune systems, severe burns, cystic fibrosis, or other serious illnesses.
Antibiotic resistance Pseudomonas aeruginosa can often be resistant to many antibiotics, making the treatment of infections more difficult.
Biofilm formation The bacterium can form biofilms, which can protect it from attack by the immune system and from the effects of antibiotics. This contributes to the chronicity of infections.
Due to its importance as a pathogen in clinical settings and its resistance to many antibiotics, Pseudomonas aeruginosa is an important topic in medical research and clinical practice. It requires careful monitoring and appropriate hygiene measures to prevent and treat infections.
Examination procedure
DIN EN ISO 16266:2008-05 Water quality – Detection and enumeration of Pseudomonas aeruginosa – Membrane filtration method
Procedure
For the determination of Pseudomonas aeruginosa, the sample is filtered, and the membrane filter is then incubated at 36°C on a selective culture medium and then analysed.
Limit value / requirement
Pseudomonas aeruginosa should not be present in drinking water and other waters.
The limit value is 0 cfu/100 ml.
Causes for exceedances
- stagnant water in storage tanks, tanks, and pipes
- favorable temperature conditions in hot water systems
- Biofilms, deposits, and sediments in hot water systems
- natural inputs from the environment
Measures in the event of exceedances
- inform users / do not supply the water as drinking water
- disinfection
- flush pipes
Clostridium perfringens
Clostridium perfringens is a gram-positive, spore-forming bacterium that is widespread in the environment. It belongs to the genus Clostridium and is anaerobic, which means that it thrives in the absence of oxygen.
Spore formation Clostridium perfringens forms resistant spores that allow the bacterium to survive unfavorable conditions.
Environmental distribution The bacterium is found in soils, sediments and the intestinal flora of animals and humans. It is frequently found in the environment.
Food poisoning Clostridium perfringens is a frequent cause of food poisoning, especially when food is undercooked or improperly stored. The toxic substances it produces can cause gastrointestinal discomfort.
Gas gangrene It is also associated with the disease “gas gangrene” (clostridial myonecrosis), which is a serious and potentially life-threatening soft tissue infection.
In drinking water Clostridium perfringens is not normally considered a direct indicator of fecal contamination in drinking water. However, its detection in drinking water may indicate environmental contamination or problems with water treatment.
It is important to note that Clostridium perfringens does not usually have the same significance as certain other bacteria when it comes to drinking water quality. However, it is considered a sign of environmental problems or potential food poisoning risks.
Examination procedure
DIN EN ISO 14189:2016-11
Water quality – Counting of Clostridium perfringens – Method using membrane filtration
Procedure
For the determination of Clostridium perfringens, the sample is filtered, and the membrane filter is then incubated at 36°C on a selective culture medium and subsequently analysed.
Limit value / requirement
The limit value is 0 cfu/100 ml.
Causes for exceeding the limit
Contamination from the environment
- contamination from unclean groundwater
- entry of surface water into the drinking water system
Problems in water treatment
- insufficient filtration and disinfection during water treatment
- lack of chlorination or disinfectant in the water system
Leaks in the water system
- leaks in water pipes can allow contaminants to enter
Measures in the event of exceedances
Notify the responsible authorities
- immediately report the detection of Clostridium perfringens to the local health authorities and other responsible bodies
General
- trace the contamination through further investigation
- thorough flushing of the entire water supply system to remove contaminated water
- isolation of the contaminated areas
- disinfection of the water system
- review of the water treatment processes
- implementation of preventive measures
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