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Bathing water quality
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Why and How is Bathing Water Quality Assessed?


Table of contents


Interpreting the Results

published on 01/08/2008

Water quality assessment criteria

Water quality is assessed in accordance with the provisions of the Public Health Code.
Bathing water quality is assessed using two types of indicators: microbiological (bacteria) and physico-chemical:
  • The microbiological analyses carried out focus on germ (bacteria) count, as these are indicators of faecal contamination. These are micro-organisms normally present in the intestinal flora of mammals and man in particular. Their presence in water denotes faecal contamination in the bathing areas. In this respect, they are an indicator of pollution from wastewater and reflect the likely presence of pathogens. The higher the concentrations of such germs, the greater the health risk.
    The bacteria sought in laboratory analysis are:
    • total coliforms;
    • Escherichia coli;
    • intestinal enterococci.
    Under certain circumstances, should the threshold quality values be exceeded or wastewater runoff pollution be found, tests may be performed to identify other germs (salmonella, enteroviruses, etc.).
More information:
The presence of Escherichia coli in water denotes recent contamination, while the presence of enterococci denotes older water contamination.
In the event of abnormal water contamination, an investigation is conducted by the DDASS in conjunction with the surrounding towns..
  • The physical and chemical parameters are measured or assessed based on appearance or small, in the field. They cover:
    • the presence of foams, phenols (aromatic chemical compounds, used to manufacture products such as pharmaceutical products, perfumes, essential oils and solvents), and mineral oils (hydrocarbon mixtures),
    • water colour, and
    • water transparency.
  • Based on field observations, other parameters also need to be measured, in particular in a laboratory setting: pH, nitrates, phosphates, chlorophyll, cyanobacteria, micro pollutants (heavy metals, etc.)…
More information:

You can find examples of cyanobacterial monitoring in bathing waters, at the local or regional level (procedures, results, etc.):

While microalgae have been known to be present in freshwater for many years now, the frequency with which they appear seems to have been on the rise these past 30 to 40 years. When it was shown that some of them produced toxins, France’s Minister of Health ordered, via a circular published on 5 July 2005, and drawing on recommendations from the World Health Organisation and France’s Higher Council of Public Hygiene (CSHPF), that procedures be set out for monitoring and managing recreational waters affected by such blooms.
The presence of microalgae can severely diminish water transparency. When water is insufficiently transparent, it can make locating endangered bathers difficult and thereby create safety issues.
Quelles actions à mener en présence de cyanobactéries ?