Lexicon Drinking water
Filtration : is a technique in which particles, present in a liquid, are retained by a porous (permeable) body.
Hardness levels : The hardness of the water is determined by the calcium and magnesium content of the water. It is expressed in three ways:
- German grade (1° D) corresponds to 10 mg calcium oxide (CaO). This corresponds to 7.14 mg of calcium or 4.28 mg of magnesium per liter of water.
- French grade (1°F) corresponds to 10 mg of calcium carbonate (CaCO3) which is equivalent to 4.0 mg of calcium or 2.4 mg of magnesium per liter of water.
- mmol : 1 mmol corresponds to 40 mg of calcium or 24 mg of magnesium per liter of water, which is therefore equivalent to 10 French degrees.
- Recommended min. hardness of cold tap water is 15°F, Soft water - 20°F Medium water 20°F – 30°F, Hard water +30°F
Acidity: or pH value of a solution fluctuates between 1 and 14. In neutral water, the pH value or acidity is equal to 7. If the pH value of a solution is between 7 and 14, the solution is basic. If the pH value is between 1 and 7, the solution is acidic. The standard value for the pH of drinking water is between 6.5 and 9.2.
Microgram: 1 microgram (1 µg) is equal to 1 thousandth of a milligram (mg).
Microorganisms: is the collection of very small living things of various degrees of development. They are so small that they usually cannot be seen with the naked eye. To distinguish them one needs a microscope with a high magnification.
Salts: Formed from the reaction of an acid with a base. Numerous salts are known in chemistry. With salts, a distinction is made between highly soluble and less soluble salts. Table salt is an example of the readily soluble salts. Scale (calcium carbonate) is formed in water heaters and this is an example of an insoluble salt.
Scale deposits: water containing calcium and magnesium salts can under certain circumstances lead to the formation of scale or “scale” on tube walls, resistors and heating elements. When the water is aerated and the temperature is increased, limescale deposits are accelerated. In addition to the hardness of the water, the concentrations of carbon dioxide and bicarbonate in the water, as well as its alkalinity, are also important.
Calcium: Calcium (chemical symbol Ca) is a metal that is abundant in nature. In limestone rocks it is in the form of calcium carbonate. Calcium is the main component that determines the hardness of the water. The human organism needs about 700 to 900 mg per day. The maximum permissible concentration in drinking water is 270 mg/l.
Iron: (chemical symbol Fe) Highly dispersed metal. The diet provides 15 to 25 mg of iron per day. The maximum permitted concentration in drinking water is 0.2 mg/l.
Corrosion: is an interaction between a material (usually metal) and its environment (e.g. water), whereby the material, usually by oxidation, is wholly or partly converted into inferior substances, so that its original properties deteriorate (e.g. loss of mechanical strength ). The most common form is rust.
Oxidation: is a chemical process in which oxygen reacts with other substances. Combustion of coal is an oxidation: this requires oxygen as the reactant and gives rise to the formation of reaction products such as carbon dioxide. In oxygenated water, oxygen also behaves as an oxidizing agent. Examples include rusting iron, oxidizing copper, etc.
Rust: is a compound of oxygen with iron. Rust is caused by slow combustion (oxidation) of iron in a humid environment.
Phosphates: (chemical formula : PO4) are salts derived from phosphoric acid (H3PO4). Phosphorus in the form of phosphate is essential for plants and animals. For surface water, the phosphate is of particular importance because high phosphate concentrations lead to more algae growth. Phosphate salts are also used in the treatment of drinking water as a corrosion inhibitor.
Polyphosphates: are made up of various phosphate molecules, which in turn are salts of phosphoric acid. Their structure allows them to form soluble compounds (called complexes) with calcium or magnesium. The maximum permitted concentration in drinking water is 5 mg/l (expressed in P2O5).
Silicates: are salts of silicon, the chemical element (Si), which is most abundant in the earth's crust. The most well-known siliceous materials in nature are quartz sand and clay.
Chlorine: (chemical symbol Cl) is a chemical element that is present in nature in the form of salts. In free form it is a green-yellow gas. It owes its name to this (chloros is the Greek word for green). Even in low concentrations in water, it is highly bactericidal. The maximum permissible concentration in drinking water is 0.25 mg/l.
Fluorine: (chemical symbol F) occurs in nature in a bound form (in minerals and organic molecules). Fluorine is found in almost all foods. We take in 0.5 to 2 mg daily through food. An excess of fluorine can lead to fluorosis. The maximum permitted concentration in drinking water is 1500 µg/l.
Lead: (chemical symbol Pb). This metal was widely used in industry. Until the end of the Second World War, this metal was used for house connections and indoor installations for drinking water. The maximum permitted concentration in drinking water is 0.05 mg/l. The new European guideline will reduce this concentration to 0.01 mg/l (weekly average).
Asbestos: is the name of a rock consisting of tough, non-combustible fibers that is mainly found on the American continent. Because of their strength and incombustibility, asbestos fibers were used for the production of all kinds of materials, such as in non-flammable clothing and in combination with cement in plates and pipes. It is no longer produced because of the health risks.
Magnesium: (chemical symbol Mg). This is one of the most widespread metals in nature. Magnesium is a component of the hardness of the water. The human organism needs about 420 mg per day. The maximum permitted concentration in drinking water is 50 mg/l.
Manganese: (chemical symbol Mn). Metal that is common in nature. Some groundwaters contain up to 3 mg/l. In most cases, manganese is present along with iron. Due to oxidation it precipitates and can form a black layer in the pipes. The maximum permitted concentration in drinking water is 0.05 mg/l.
Sodium: (chemical symbol Na) plays an important role in food and industry in the form of sodium chloride (table salt). Sodium is an essential component of water. The concentration in it is a few mg to 500 mg per liter and even more. An adult needs about 2000 mg of sodium per day. Our diet already provides 3000 to 5000 mg per day. So it is unnecessary to add salt to our diet. Water intended for human consumption legislation sets a limit of 150 milligrams of sodium per liter of water at the point of delivery. At the tap, a value of 200mg/l must be taken into account as an indicator parameter.
Sodium hypochlorite: (chemical formula NaClO: sodium hypochlorite) also called JAVEL water, is an industrial chlorine product that is used for the disinfection of drinking water.
Nitrate: (chemical formula NO3-) is a chemical compound, namely a salt derived from nitric acid (HNO3). Nitrates are used in agriculture as fertilizer and are all readily soluble in water. As a result, this connection poses a threat to groundwater quality, especially in shallow water abstractions. The maximum permitted concentration in drinking water is 50 mg/l (expressed in NO3-).
Nitrite: (chemical formula NO2-) is a chemical compound, namely a salt derived from nitrous acid (HNO2). It occurs in water as a result of bacterial oxidation of ammonium; this intermediate product of the oxidation of ammonium is quickly further oxidized to nitrate. Nitrate is converted into nitrite in the gastrointestinal tract, especially in young babies. The maximum permitted concentration in drinking water is 0.1 mg/l (expressed in NO2-).
Nutrients: Nutrients such as nitrogen (N) and phosphorus (P) are nutrients for plants. When present in excess in the surface water, they cause algal blooms or eutrophication. Further removal of nitrogen and phosphorus in the water treatment plants is imposed for WWTPs > 10,000 I.E.
Nitrogen: (chemical symbol N taken from "Nitrogen"). Our atmosphere (the air) is formed by 1/5 oxygen gas (O2) and 4/5 nitrogen gas (N2). Both gases are soluble in water. The solubility depends on physical factors such as pressure and temperature. Nitrogen is a very important element in the structure of living matter and this explains the application of nitrogenous fertilizers in agriculture. Carbon dioxide (chemical symbol CO2). Carbon dioxide is an odorless gas that occurs in nature (cfr. greenhouse effect) and is also present in the breath of humans and animals. Groundwater is generally rich in carbon dioxide. It is added to sparkling bottled water. This gas is responsible for corrosion and deterioration of materials in contact with drinking water.
Bacteria: are very small single-celled microorganisms, often rod-shaped. After all, in Greek "bakteria" means stick, rod. Some of them are the cause of many infectious diseases. Many other bacteria are harmless or even useful to humans.
Legionella: is a bacterium that causes a kind of pneumonia, especially in weakened people. The word is derived from the English "Legionnaire" (veteran or former combatant), because the disease first broke out en masse at a former combatant meeting in the United States of America. It is therefore sometimes also referred to as "legionnaires' disease".
Virus: is derived from Latin and means poison, contaminant. The word refers to small organisms, which can develop only in foreign living cells.
Membrane: is a natural or synthetic membrane (thin sheet) that separates two environments. Synthetic membranes can be used in water purification. The membrane types are characterized by their pore size. The current membrane techniques are micro- and ultrafiltration (removal of suspended solids) on the one hand and nanofiltration and hyperfiltration or reverse osmosis (removal of dissolved salts) on the other. The application of the latter requires a lot of energy.
Reverse osmosis: also called hyperfiltration, is a drinking water treatment technique in which pre-purified (sea) water is pressed under very high pressure (25 to 45 bar) through a semi-permeable (semi-permeable) membrane that only allows the water to pass through. This creates on the one hand a water stream with a very low salt content and on the other hand a waste stream, called "brine", with a very high salt content. This technique requires a lot of energy and is used for the desalination of seawater and brackish water. The high energy price and the high cost price of the membranes form an obstacle to the breakthrough of this technology.
U.V. radiation: is a radiation with which reliable disinfection of drinking water can be carried out. The nucleic acids inside the bacterial cell are broken down and the bacteria are killed. This disinfection technique is mainly applied to clear groundwater because the content of UV-absorbing substances (humic acids) must be very low for efficient operation . However, it has no lasting effect.
Ozone: (chemical formula O3). Ozone is a strong-smelling and oxidizing gas. It is produced at the point of use in drinking water preparation because it is not stable.
Ozonation: is the process of bringing ozone into contact with water. This happens in ozone contact chambers.
Water hammer: When the flow of water (or another liquid) in a pipe is suddenly slowed down or interrupted, this can lead to pressure surges. Water hammer can be caused by closing a valve too quickly or by the presence of air in the pipes. These sudden pressure surges can cause serious damage to pipes and equipment.
Consequences of limescale in pipes:
| Scale deposit thickness (mm) | Yield loss (%) |
|---|---|
| 0,4 | 4 |
| 0,8 | 7 |
| 1,8 | 11 |
| 3,2 | 18 |
| 4,8 | 27 |
| 6,4 | 28 |
| 9,6 | 48 |
| 12.7 | 60 |
| 16 | 74 |
| 19 | 90 |
Source: Belgian Federation for the Water Sector vzw