Water quality

Although mankind has long been aware of its dependence on water, we realize that supply is not unlimited, and that we must value it accordingly. ISSeP acts as a sentinel for the environment, meeting the requirements of regional, federal and European authorities and contributing to the implementation of the WFD by operating water body monitoring networks. ISSeP is responsible for the sampling, physico-chemical and microbiological analysis and ecotoxicological characterization of various types of aqueous samples. This expertise is also put to good use as part of our mission as a Reference Laboratory for water, in the implementation of new analytical methods and as part of research projects. Water pollution and scarcity threaten human health and quality of life. But broader ecological concerns also come into play. A shortage of quality water harms aquatic, terrestrial and wetland environments, exerting additional pressure on flora and fauna, which are already suffering the consequences of urbanization and climate change. Water management is linked to a number of policies. Integration is the only way to guarantee water sustainability. This is why, in Europe, Directive 2000/60/EC (Water Framework Directive or WFD) and its daughter directives cover all aspects of water use and consumption. Their purpose is to prevent, preserve and improve aquatic ecosystems, and to reduce and prevent groundwater pollution and overexploitation. Let’s work together to achieve maximum protection for the biodiversity that surrounds us.

Surface water

The Walloon network for monitoring the physico-chemical quality of surface waters comprises almost 400 sampling points spread across the 15 sub-watersheds defined in the Walloon Government decree of September 13, 2001 delimiting the river basins and sub-watersheds in the Walloon Region (AGW 13/09/2001).

In order to monitor the ecological and chemical status of surface waters in accordance with Directive 2000/60/EC, known as the Water Framework Directive (WFD), the monitoring program comprises four types of control, each of which meets specific objectives:

  • Monitoring is a global control, intended to give an image of the general state of water bodies (particularly on a European scale) and to reflect their long-term evolution.
  • The main aim of operational control is to monitor all bodies of water identified as being at risk of failing to meet environmental objectives, in particular by assessing the effectiveness of actions implemented as part of management plans.
  • Investigative control is carried out on a case-by-case basis where the reasons for failure to meet targets remain unknown, but also to determine the extent and impact of accidental pollution.
  • Additional monitoring is carried out on water bodies that are not at risk, to monitor protected areas (water catchment points, Natura 2000 areas, etc.).

The frequency and frequency of site visits varies from one site to another.

Generally speaking, monitoring sites are visited 13 times a year, while operational and additional monitoring sites are sampled 6 to 13 times every 3 years.

Surveys are spot checks (limited in time and space).

The analytical program for the surface water network (ESU) is defined annually by SPW ARNE (list of points, lists of parameters per point and sampling frequency for each point).

He presents:

  • General sampling parameters ;
  • macropollutants such as major metals;
  • nutrients ;
  • and mineral and organic micropollutants.

All the parameters required by the directive are normally provided for at least at the monitoring sites (parameters divided between the ESU and biota matrices).

For other sites, the program is defined according to the status of the water body.

Physico-chemical data are transmitted to SPW ARNE, which compiles physico-chemical data (ESU + biota), biological data (DEMNA data), flow rate, etc. in order to assess the status of water bodies and define action plans to achieve or maintain good status objectives.


ISSeP also monitors the quality of heritage groundwater on behalf of SPW ARNE.

This monitoring network has two main themes:

  • qualitative aspect ;
  • the quantitative aspect.

The qualitative component involves water samples taken at different frequencies, either for complete SEQ-ESO (Système d’évaluation de la qualité des eaux souterraines) type analyses, or for more thematic analyses such as nitrates.

Some sites, deemed sensitive, require continuous monitoring of a few simple physico-chemical parameters (pH, t°, conductivity, pressure, turbidity, fluorescence). These sites are then equipped with monitors for this purpose.

Resurgences deemed sensitive are continuously monitored for a few simple physico-chemical parameters.

The quantitative component involves measuring accessible piezometric levels at active and passive structures, as well as flow measurement at naturally active sites.

Recreational waters

Pool water

ISSeP carries out self-monitoring of Walloon swimming pools in coordination with the Police and Control Department of the Walloon Public Service (DPC). In addition to administrative supervision of the facility, the inspection includes in situ measurements (chlorine, pH…) and taking water samples from the pools for laboratory analysis for the parameters listed in the decrees relating to the management of swimming pools (M.B. 12.07.2013). From time to time, shower water is tested for the presence of Legionella pneumophila. Trichloramine is measured in the air in the pool hall in the event of a “pungent” atmosphere, or at the request of the Police and Control Department of the Walloon Public Service (DPC).

Bathing water

During the summer, ISSeP also monitors bathing water quality. This inspection takes place over a minimum of 15 weeks, between the beginning of May and the end of September. All zones are monitored for intestinal enterococci and Escherichia coli. In the event of occasional exceedances of the quality standards set out in European Directive 2006/7/EC, an additional inspection is carried out within 72 hours of the initial inspection, to check whether the pollution is short-term and possibly due to unfavorable weather conditions.

For bathing areas located on bodies of water, the ISSeP monitors cyanobacteria (microscopic algae) and the cyanotoxins they produce under certain conditions. Cyanobacteria are monitored by measuring chlorophyll A (biomass assessment) and identifying potentially toxin-producing cyanobacteria by optical microscopy. Microcystins are measured using the Elisa technique.

During the season and at RW’s request, the ISSeP can use automatic samplers to assess the impact of proximity to WWTPs, drought periods, storm events, etc. This equipment is switched on and samples every 2 hours. Samples collected in this way are analyzed for intestinal enterococci and Escherichia coli.

Industrial water and wastewater

Industrial effluents

Among the industrial effluents and wastewater treatment plant discharges selected by SPW ARNE, priority and priority hazardous substances are subject to a specific inventory to meet the requirements of the Environmental Quality Standards (EQS) directive, the daughter directive of the Water Framework Directive. All this information enables us to take better account of the objectives to be achieved for the good status of water bodies, and is a valuable decision-making aid when revising companies’ environmental permits.

ISSeP implements a battery of physico-chemical tests as well as bioassays (bacteria, algae, rotifers, daphnia, YES/YAS tests) to assess the impact on ecosystems of a series of complex industrial wastewater discharges with high toxic potential and flow rates. These releases are designated by SPW-ARNE. Receiving water bodies are also monitored.

Bioassays are excellent tools for assessing the effectiveness of measures (actions) taken as part of management plans for industrial or other discharges. They enable the various parties (government, industry, etc.) to estimate and visualize the results of the efforts made (action under the measurement program), directly on the biological organisms characteristic of the receiving environment and the different trophic levels of aquatic ecosystems. Certain bioassays (YES-YAS) are deployed to determine the (anti-) estrogenic and (anti-) androgenic activities of samples (surface water and wastewater). They are highly relevant screening tools for the presence of endocrine disruptors, which are a growing source of concern for public managers and the European Union.

Cooling towers.

ISSeP carries out inspections of air-cooled towers located on company premises, in coordination with the Police and Inspections Department of the Walloon Public Service (DPC). Controls include legionella analysis, as well as in situ measurements (conductivity, turbidity, pH, etc.) and water sampling.


Some highly hydrophobic substances accumulate in biota (fish and invertebrates living in rivers) and are difficult to detect in water, even using the most advanced analytical techniques. For such substances, Directive 2013/39/EU has established Environmental Quality Standards (EQS) that apply to biota. Monitoring of priority substances on this matrix has therefore been developed at ISSeP.

The “Biote” network has been set up with the aim of obtaining biota analysis data for all water bodies in Wallonia, as well as temporal monitoring of results at monitoring stations. Fish (chub, loach, gudgeon, bream, goby or sculpin) and invertebrates (crustaceans or molluscs) sampled in situ are analyzed for the priority substances currently stipulated in the EQS directive for these matrices (benzo-a-pyrene, fluoranthene, mercury, HCB, HCBD, PBDEs, heptachlor and heptachlor epoxide, dioxins and dioxin-like PCBs, PFOS, dicofol and HBCDD). Invertebrates are also introduced by caging at certain sites where these organisms are absent.

Monitoring based on the effects and modes of action of certain families of substances: biomarkers on sentinel species

The Ecotoxicology unit uses the Gammaruspulex as a model species for biomonitoring. Indeed, the use of gammarids offers a number of advantages: they are abundant in many watercourses and have a very wide distribution in Europe, they are sensitive to many pollutants but sufficiently resistant to survive when these pollutants are present in the environment, their life cycle is entirely aquatic and, what’s more, numerous bibliographical studies are available on their subject. They can easily be induced in situ using populations of organisms from reference sites. In addition to the determination of bioaccumulable substances (PAHs) in this biota, this organism is also used for the determination of two biomarkers: acetylcholinesterase (AChE) which detects the exposure of aquatic organisms to inhibitors such as neurotoxic pesticides (organophosphates and carbamates) and glutathione-S-transferases (GSTs) which are involved in the phase II detoxification of hydrophobic xenobiotics (PAHs, PCBs, pesticides, ….). Other enzyme activities will be used as biomarkers in the near future to complete the tool. The feeding rate of gammarids is also monitored during caging or in the laboratory. This parameter is in fact inhibited by a wide range of contaminants (heavy metals, biocides, drugs and other organic compounds) and therefore provides information on the state of health of individuals and therefore of the environment.

Bioindication based on macroinvertebrates and their biological, physiological and ecological traits for a triad approach.

The complementary use of bioindicators based on the composition of macroinvertebrate communities in the rivers studied (inventory of taxa present and their abundance in order to develop a triad approach) provides a global (holistic) view of the state of the rivers considered. Indeed, taken separately, each of the components making up the triad (chemical analyses, effects-based methods, population impact studies) provides relevant but incomplete information. On the other hand, combining the three approaches and relating the results obtained from each of them allows us to better define the impact of the pressures exerted at a given station, by highlighting the factors that most affect the quality of the ecosystems under consideration. This will make it possible to identify with greater certainty the causes of ecosystem deterioration (the weight of evidence) and to act more effectively to reduce the impact on the ecosystem. Developments in the synthetic analysis of biological, physiological and ecological traits of taxa open up interesting prospects for describing and interpreting the structure and functioning of aquatic ecosystems, and for assessing their biological quality.


Sediment toxicity

Sediments are the ultimate reservoir for many chemical pollutants, both point source (industrial or urban effluents, disused economic sites) and non-point source (agricultural pesticides). They are thus the “memory” of contamination. Conversely, they can also be a source of contamination. Bioassays are very useful for assessing the actual state of sediments in which both known and unknown contaminants are present at concentrations sufficient to cause toxicity to the test organisms. The combination of three assessment methods (chemical, bioassay and ecological – the “triad” approach) provides an answer that could not be given by any of the methods taken individually. The Ecotoxicology Unit :

  • performs whole-sediment tests with sediment-dependent organisms;
  • applies a battery of aquatic ecotoxicological tests on pore water and sediment leachates.