Lack of access to drinking water is the leading cause of death in the world.
Without water, there can be no life and no development, because water is needed for agriculture and most economic activities.
The United Nations (UNESCO and UN WATER) report published in 2019 states that: "Three out of ten people, or 2.1 billion people, do not have access to safe drinking water services. Nearly half of the people who draw their drinking water directly from surface water live in sub-Saharan Africa. Six out of ten people do not have access to safely managed sanitation facilities, and one in nine practise open defecation. However, these global figures mask the profound inequalities that exist within and between regions, countries, communities and neighbourhoods".
Access to sanitation is a question of dignity, but also of hygiene and health.
If surface water (rivers, ponds, etc.) is polluted by animal or human faeces, it becomes dangerous for the people who drink it. This is why water is the leading cause of death in the world.
Solidarity tools exist to give the most disadvantaged populations, particularly in Africa and Asia, better access to water and sanitation.
Belgium is developing cooperation initiatives in various countries around the world to drill boreholes, install pumps or develop sanitation (installation of latrines).
The SPGE is also heavily involved in Africa in order to provide a better standard of living for local people and to raise awareness of the importance of doing the right thing.
Head office and administration: Rue des écoles, 17/19, 4800 Verviers - Technical office: Avenue de Stassart 14-16, 5000 Namur
The production of drinking water refers to any action or treatment that makes it possible to produce drinkable water from natural water that is more or less polluted. The treatment required depends very much on the quality of the water resource. It also varies with the level of requirements and standards applied, which differ from country to country. It is either carried out by the local authority ("en régie", by the municipality or a group of municipalities) or delegated to a private company (public service delegation), with costs varying widely depending on the context.
Some of the micropollutants (pesticides, nitrates, drug residues, etc.), some of which are endocrine disruptors in small doses, are still difficult to eliminate. In arid regions, this also involves "scarcity management".
Origin of water
There are four available sources of natural water:
groundwater: aquifers, water tables, seepage ;
captive or flowing surface water: glaciers, lakes, ponds, rivers; sea water;
Groundwater is contained in a wide variety of aquifers, defined by the porosity and structure of the ground. These parameters determine the type of aquifer and how the water circulates.
The geological nature of the ground has a decisive influence on the chemical composition of the water. A balance is established at all times between the composition of the soil and that of the water:
sandy or granitic soils provide acidic water with low mineral content; limestone soils provide calcic water with high mineral content and a high incrustation rate.
Groundwater has long been synonymous with clean water, naturally meeting drinking standards. This water is less sensitive to accidental pollution, but surface treatment can make it unfit for consumption.
Unconfined aquifers are more sensitive, being fed by surface water infiltration, than confined aquifers, which are separated by an impermeable layer. The most sensitive are alluvial aquifers, which are directly influenced by the quality of river water.
When an underground resource has been polluted, it is difficult to recover its original purity, as the pollutants have contaminated not only the water but also the surrounding soil (fixation and adsorption on the rocks and minerals in the subsoil).
Depending on the terrain in which it originates, groundwater may contain elements that exceed drinking water standards. These include iron, manganese, H2S, fluoride, arsenic, etc. All water that exceeds these standards must be treated before distribution.
Certain legislation in France and Europe, among others, defines specific characteristics for mineral waters5. When distributed in bottles, these ground waters may contain elements in concentrations higher than those authorised for drinking water. The
characteristics are defined by another standard5.
Surface water originates either from groundwater (through a resurgence or spring) or from run-off. These waters are grouped together in watercourses and are characterised by a free surface, the contact surface between the water and the atmosphere, which is always in motion, with variable speed. Surface water can be stored in natural reservoirs (lakes) or artificial reservoirs (dams) of varying depth. The exchange surface is then virtually immobile.
The composition of surface water is extremely variable, linked to the nature of the ground through which it flows and to water/atmosphere exchanges (water is loaded with dissolved gases: oxygen, CO2, nitrogen, etc.). Note the following
presence of dissolved oxygen ;
high concentration of suspended matter; presence of organic matter ;
presence of plankton;
daily or seasonal variations (temperature, snow melt, leaf fall, etc.).
Because of the influence of all these parameters, surface water is rarely drinkable without treatment. It is generally bacteriologically polluted and may contain several sources of pollution:
urban (discharge from sewage treatment plants) ;
industrial (solvents, hydrocarbons, synthetic products, heavy metals, toxic products, etc.); agricultural (pesticides, herbicides, nitrates, organic waste, etc.).
Seawater and brackish water
These waters are characterised by high salinity. Depending on where they come from (open sea, foreshore, estuary), their physical characteristics vary widely: turbidity, suspended solids, presence of plankton, sand content, pollution from urban or industrial waste, influence of rivers, influence of the tide, water temperature, etc.
Because of its high salt content, seawater is undrinkable and requires extensive desalination6. However, as Alain Bombard has shown, the juice extracted from fish is perfectly drinkable.
Condensation of air humidity
Water is present in the atmosphere in gaseous form unless its concentration has increased to the dew point where it becomes mist and then liquid. The saturation point, defined in a Mollier diagram, also varies according to temperature and pressure (see Psychrometry, Moist air for more information). The coolness of the night precipitates it at dawn onto the leaves of trees or any surface forming a suitable receptacle. This is how some insects can collect tiny droplets in the Sahara desert in the morning. Water can also be precipitated onto cold bodies. A large quantity of drinking water can be collected at sea using a floating metal mass. Certain processes involving the loss of energy by thermal radiation also allow water to condense in the atmosphere (cooling).
In certain desert areas, the moisture contained in the clouds or in the air can be captured by a simple, slightly cooled metal plate7.
In this way, the fog can be "trapped" to produce drinking water on mountaintops, using large fine-mesh nets hung between wooden poles, like screens in the open air. Below, a cistern feeds a tap. This system is used in South America and Africa (schools, villages, etc.).
Africa (schools, villages, etc.). The supply of water by this means is irregular and unpredictable, but is becoming increasingly popular in poor regions or those with no other drinking water resources8.
Air condensation can also be used to produce drinking water from wind or solar energy9, 10.
Degreasing and de-oiling operations consist of separating products with a density slightly lower than water (oil, grease, petroleum products) by natural or assisted flotation using floating obstacles or sets of vertical baffles.
Screening and sand removal
Treatment carried out on raw water to remove objects carried by a watercourse (branches, leaves, etc.) as well as all suspended solid particles such as sand.
Coagulation and flocculation
Coagulation and flocculation are at the heart of drinking water treatment. The first step is to add a coagulant, which neutralises the charge of colloidal particles (responsible for colour and turbidity, among other things), so that they no longer repel each other. It is added just before, or in a rapid-mix tank for a faster effect. We then inject a flocculant or coagulant aid, which has the effect of agglutinating all the particles that have become neutral, i.e. bringing them together to form flakes large enough to settle (sink to the bottom). This stage takes place in a slower mixing tank to avoid breaking up the flakes once they have formed, but still achieve a diffusion effect.
The settling stage follows coagulation and flocculation and precedes filtration. Once the flocculant or coagulant aid has been injected and mixed with the water, the latter is sent to the sedimentation tanks, also known as "decanters". These are large basins with a retention time high enough to allow the flakes that formed the turbidity and colour to sink to the bottom of the basin and accumulate to form sludge, which must be removed regularly to prevent build-up. The water will then be sent to the filters, which will remove the smallest particles that did not settle or settle during the previous stage.
The water is passed through a filter that intercepts small particles. The smaller the filter mesh, the smaller a particle must be to pass through. Filtration can be carried out as a tertiary treatment of raw water, as a secondary treatment of wastewater or as the sole treatment, in the case of transmembrane filtration. The most common filters used in water treatment plants are sand and anthracite filters. Filters ensure that the water leaving the plant complies with current standards (or better) in terms of turbidity (the colour having been removed by the previous stage).
However, viruses and bacteria can pass through the filters, which is why the final disinfection stage is compulsory.
Instead of disinfection, ultrafiltration can be used. Ultrafiltration can be used to produce drinking water from, for example
surface water (river water, ponds, wells or brackish water). Ultrafiltration systems were developed in the 20th century for the production of drinking water, but they remain costly and unsuitable for the rapid production of large volumes of drinking water17. New purely mechanical systems can produce up to 1,000 litres of water per hour, or 150,000 litres per month18.
Activated carbon filtration
Activated carbon, a compound with a high carbon content, adsorbs many other compounds, some of which are toxic. Chlorine is eliminated by catalysis and organelles are eliminated by adsorption. Activated carbon is used in granular or powder form. In granular form, the water percolates through a bed of activated carbon, derived from coconut or mineral coal, to purify it of these compounds. When activated carbon is used in powder form, it is added to the water as a suspension and then decanted or filtered. This method is also used to filter household water and aquarium water.
There is a straw for individual use that uses two textile filters (one made of polyethylene and the other of polyester) to retain particles larger than fifteen micrometres. It then has a third partition containing resin beads impregnated with iodine, which destroys
microbes, including those responsible for cholera, typhoid and dysentery. It is capable of filtering around 700 litres of water, equivalent to the annual consumption of a human being. This LifeStraw straw lets you drink directly from a river or stagnant water19.
Disinfection is used to eliminate bacteria and viruses. Some drinking water production plants use ozone (O3). The weak bond between the three oxygen atoms in the ozone molecule gives this gas great oxidising power: by oxidising all organic substances, ozone inactivates pesticides and pathogenic micro-organisms20.
Disinfection is most often carried out using chlorine. According to the WHO, 2 to 3 mg/L of chlorine should be added to water, with a maximum of 5 mg/L21.
In the United States, the maximum residual quantity of chlorine is 4 mg/L22, to enable water distributors to comply with the minimum residual quantity of 0.02 mg/L (measured at the end of the line) set by law.
There is no European standard for the amount of chlorine used to disinfect tap water, but some European countries have national standards:
in Belgium, the maximum is 0.25 mg/L ;
in France, the maximum is defined as follows: "Absence of unpleasant odour or taste and no abnormal change 23".
Other purification techniques
Water is kept at boiling point long enough to inactivate or kill microorganisms that live in water at room temperature. Boiling does not eliminate solutes that have a higher boiling point than water; on the contrary, their concentration may increase if water evaporates. The autoclave or pressure cooker refines and improves the process by adding high pressure, which prevents the water from leaking and increases its boiling temperature.
In distillation, water is boiled to produce vapour, which rises and is brought into contact with a cooled surface where the vapour condenses back into liquid water, which can be collected. The solutes do not normally vaporise and therefore remain in the boiling solution. That said, even distillation does not completely purify the water, due to contaminants having roughly the same boiling temperature as water, and non-vaporised water droplets carried along with the steam.
Distillation by still.
In reverse osmosis, high pressure (thousands of hectopascals) is applied to an impure solution to force the water through a semi-permeable membrane. This process is called 'reverse osmosis' because normal osmosis would see pure water moving in the other direction to dilute the impurities. In theory, reverse osmosis is the best method for large-scale water purification, but it is difficult to create good semi-permeable membranes. Depending on the type of membrane, 85-98% of inorganic ions are removed, 99% of colloids, bacteria, pyrogens and viruses, and 80-98% of silica. This method, sometimes called "hyperfiltration", is used, for example, to produce around 90% of the drinking water distributed along the Belgian coast by treating wastewater in a wastewater treatment plant.
reverse osmosis undergoes photo-oxidation using ultraviolet radiation, then is filtered in sand dunes for around forty days before being pumped and distributed as drinking water24.
This is a non-polluting physical demineralisation process, with no added chemicals.
The reverse osmosis process uses a semi-permeable membrane to separate dissolved solids, organic matter, viruses and bacteria from the water.
In operation, water is pressed onto the module. It penetrates through the layers of the membrane, and is collected in the porous support (permeate). The salts retained are discharged directly (concentrate/brine).
Conventional commercial equipment produces 9 litres of concentrate for every 1 litre of demineralised water produced. This concentrate can be used to a certain extent for other purposes, but when it is thrown away, the result is a certain waste of water, in a ratio of one to ten. More recent appliances - with booster pumps to optimise pressure - reduce this ratio to as little as 1 L to 1 L.
Demineralisation by ion exchange
For demineralisation by ion exchange, the water is passed through a column loaded with ion exchange resin, which captures the ions, releasing hydroxide ions (for negatively charged ions: sulphate, carbonates, etc.) or hydronium ions (for positive ions: calcium, magnesium, other metals, etc.), which recombine to reform water. In many laboratories, this purification method has replaced distillation because it produces a large volume of very pure water more quickly and with lower energy consumption. The water obtained in this way is called "deionised water" or "demineralised water". Unlike distillation, demineralisation allows production on demand. Ion exchange resins are sometimes combined with post-filtration to remove particles from the resin.
Electrodialysis uses ion exchange membranes. The driving force is the electric current that removes the ions from the solution that needs to be desalinated (seawater, brackish water, etc.): the saltier the water, the greater the power consumption.
In photo-oxidation, the water is exposed to high-intensity ultraviolet radiation. This cleaves and ionises organic compounds, which can then be eliminated in ion exchange columns. It also produces oxidising compounds that can destroy micro-organisms and certain molecules.
Notes and references
1. Carpentier, A., Nauges, C., Reynaud, A. and Thomas, A. (2007), Effets de la délégation sur le prix de l'eau potable en France, Économie & Prévision, (3), 1-19.
2. Bouscasse, H., Destandau, F. and Garcia, S. (2008), Analyse économique des coûts des services d'eau potable et qualité des prestations offertes aux usagers (http://rei.revues.org/3819), Revue d'économie industrielle, (122), 7-26.
3. Janex-Habibi, M. L., Bruchet, A. and Ternes, T. (2004), Effet des traitements d'eau potable et d'épuration des eaux usées sur les résidus médicamenteux. Résultats du projet Poseidon, TSM (Techniques sciences méthodes), génie urbain génie rural, (11), 59- 67 (abstract (http://cat.inist.fr/?aModele=afficheN&cpsidt=16347994)).
4. Darmame, K. (2004), Gestion de la rareté : Le service d'eau potable d'Amman entre la gestion publique et privée (http://www.iwmi. cgiar.org/assessment/files/word/ProjectDocuments/Jordan/RapportDarmame%281%29.pdf) [PDF], 68 p., in "Programme de recherche international", conducted by IWMI (International Water Management Institute), entitled "évaluation intégrée de la gestion de l'eau en agriculture".
5. See Natural mineral water.
6. See Potability of seawater.
7. "Trois solutions pour transformer l'humidité de l'air en eau potable" (http://avauleau.acwed.net/post/2015/04/03/Trois-solutions-p our-transformer-l-humidit%C3%A9-de-l-air-en-eau-potable), on avauleau.acwed.net, 3 April 2015 (accessed 3 May 2016).
8. Fog trap (http://www.idrc.ca/fr/ev-26965-201-1-DO_TOPIC.html), on idrc.ca.
9. Turning air into water and intellectual property into added value (http://www.wipo.int/ipadvantage/fr/details.jsp?id=3108).
10. Eole Water, "Eole Water - Give us wind, we give you water" (http://www.eolewater.com/), on eolewater.com (accessed 15 February 2017).
11. WHO, Guidelines for drinking-water quality, 3rd edn (2004), WHO (http://www.who.int/water_sanitation_health/dwq/gdwq3rev/f r/index.html).
12. United States Environmental Protection Agency USA, Drinking Water Contaminants (http://water.epa.gov/drink/contaminants/ind ex.cfm).
13. EEC, Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption, EEC (http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:1998:330:0032:0054:FR:PDF) [PDF].
14. Germany, Bundes ministerium der justiz, Regulation on the quality of water intended for human consumption (http://bunde srecht.juris.de/trinkwv_2001/index.html).
15. Great Britain, OPSI, The Water Supply (Water Quality) Regulations 2000 (http://www.opsi.gov.uk/si/si2000/20003184.htm).
16. France, Décret no 2001-1220 du 20 décembre 2001 relatif aux eaux destinées à la consommation humaine, Normes françaises (ht tp://admi.net/jo/20011222/MESX0100156D.html).
17. Gourgues, C. (1991), Ultrafiltration de suspensions de bentonite par des fibres creuses : production d'eau potable (http://cat.inist.f r/?aModele=afficheN&cpsidt=148344) (Doctoral dissertation).
18. Read online (http://www.safewatercube.com/safe-water-cube/) at safewatercube.com.
19. Sciences et Avenir, no 704, p. 16, October 2005.
20. Ozonation (http://www.traitement-eau-annet.veoliaenvironnement.com/technologies/ozonation.aspx), on
21. Guidelines for Drinking Water Quality (http://www.who.int/water_sanitation_health/dwq/gdwq3_8.pdf) [PDF], 3rd ed. at
22. Drinking Water Contaminants (http://www.epa.gov/safewater/contaminants/index.html), on epa.gov.
23. Decree no. 2001-1220 of 20 December 2001 on water intended for human consumption, excluding natural mineral water (http://www.sante.gouv.fr/adm/dagpb/bo/2001/01-51/a0513394.htm), on sante.gouv.fr.
24. Torreele station (https://www.aquaduin.be/drinkwater/waterwinning/torreele_fr.pdf) [PDF], on iwva.be.
Are microwaves dangerous to your health? Some scientists have set out to answer this question.
Food is impoverished by waves
Microwaves are either your thing or your thing of the past. Ever since it was invented, this household appliance has been the subject of endless debate. For some, it represents a real danger to health, while others couldn't do without it. So what's really going on? A number of studies have been carried out on the subject and have come up with an answer that will not necessarily please fans of fast cooking.
From a strictly nutritional point of view, microwaves reduce the quality of food. A Swiss scientist, Hans Hertel, put forward this theory during a study in which he proved that the transformation of food molecules under the effect of waves impoverished their nutrient content. A second study, conducted by Search for Health, found that people who ate food cooked or reheated in a microwave oven experienced a rapid increase in cholesterol levels, white blood cells and a reduction in haemoglobin.
To be safe, a microwave must be well insulated
Why is microwave cooking responsible for these transformations? The answer lies at the very heart of the appliance, in the magnetron. This is the generator of electromagnetic waves which, when activated, acts on the molecules, causing them to stir. By colliding with each other, the molecules produce energy that is translated into heat.
If a microwave is poorly insulated, these waves can be deployed close to you and it is at this point that effects on your health can be felt. Some studies have shown that this radiation can cause insomnia, migraines and depression. They could also encourage the development of cancer or weaken the immune system. Microwaves should therefore be used with caution. When in use, it's best to stay away from the appliance and make sure it is always well sealed.
Demineralised water is a substance stripped of all its minerals. After processing, it is also known to remove most of the chemical elements present in conventional water. But is this enough to make demineralised water drinkable?Consequences for the intestinal mucosa
That's the question we're going to answer.
Can you drink demineralised water?
Yes and No!
If you want to try it, you can drink a glass of demineralised water. In fact, a can of demineralised water is nothing like a bottle of bleach or any other similar product, which is extremely dangerous to your health. You should be aware, however, that demineralised water does not taste good. This is hardly surprising, since it is not primarily intended for drinking. If you drink a glass of demineralised water from time to time, you won't see any real change in your body. At the very most, you may feel a slight stomach ache because your body is not used to it, but nothing really serious for your body.
Drinking demineralised water: what are the health risks?
If you risk drinking demineralised water on a more regular basis, you are exposing yourself to real risks to your health (even more so if it becomes your primary source of water consumption). If your body doesn't get enough mineral salts, it can quickly become deficient. By drinking large quantities of demineralised water, the body will be drained of its mineral salts, which are essential to its proper functioning. The cells will then gradually deplete of their mineral salts.
Health risks of demineralised water
Bear in mind that demineralised water is tap water from which the limescale has been removed. During this process, the water may stagnate in the open air, sometimes for up to several days. During this time, the water can become infested with bacteria, which are themselves pathogens that are incompatible with our bodies.
Generally speaking, when water penetrates the body, a balance is formed between the salts. Since demineralised water contains no salts, it will recover the cations from our cells and then eliminate them. Note that the loss of salts is not an optimal situation for our body. To find out more, F. Koziek, in a book entitled "The health risks of drinking demineralised water", identifies the main consequences of drinking demineralised water for our bodies:
Consumption of water low in calcium and magnesium, essential for the body
Consumption of water with a low concentration of other elements
Possibility of increased toxic metal indigestion
Possible increase in the presence of bacteria