Water microbiology addresses various types of water that do not have the same requirements as:
Drinking water, intended for human consumption, in which the presence of certain germs can be harmful to human health. Problems linked to the presence of these germs are well controlled thanks to microbiological quality controls and systematic disinfection treatments.
Bathing waters must comply with European Directive 2006/7/EC on the quality of bathing water, which mainly requires testing for intestinal enterococci(standard NF EN 7899-1 ) and Escherichia coli(standard NF EN 9308-3 ).
Public swimming pools are governed by the French Public Health Code, which lays down hygiene and safety rules for the installation, layout and operation of swimming pools. A certain number of physical, chemical and microbiological standards must be met: pool water must be filtered, disinfected and disinfectant(article D.1332-2 of the Public Health Code).
Industrial cooling waterneeds to be treated to keep corrosion at an acceptable level, maintain good heat exchange and eliminate bacteria, some of which can be fatal, such as Legionella.
Problems encountered
Pollution by micro-organisms is a major problem in industrial cooling circuits and can cause :
- Reduced heat transfer in heat exchangers due to micro-organism deposits
- Reduced water circulation in condensation pipes
- Clogged pipes in heat exchangers can lead to breakdowns and reduced productivity.
- The corrosion of metal by micro-organisms has become the main problem for manufacturers.
- Development oflegionellosis
- Relatively insoluble minerals such as calcium carbonate, calcium phosphate and magnesium silicate can precipitate out of the water, forming deposits.
Microbiological deposits can occur over a very short period of time (between 4 and 8 hours). These are mainly fast-growing, heavily encapsulated bacteria, such as Aerobacter, ArthrobacterProteus, Bacillus, Pseudomonas...
Originally, there are non-microbiological substances (silt, various debris contained in the cooling water). Microorganisms, especially filamentous ones, cause the non-microbiological debris to become suspended.
It is therefore necessary to be able to monitor the level of microbial pollution in the circuit water in order to better identify any potential problems that may arise, and to plan treatment with an effective bactericide or fungicide.
Full identification of the microbial flora and fauna present is not necessary.
The MICROTEST A counts total aerobic bacteria, fungi and yeasts as a good indicator of system cleanliness. The values given in the table below are generally accepted for assessing circuit cleanliness and the effectiveness of biocidal treatment.
In most cases, counting aerobic bacteria, fungi and yeasts as well as semi-quantitative testing for sulfate-reducing bacteria with the MICROTEST SR is sufficient to check whether the circuit has been treated with a biocide.