According to current standards, drinking water (including tap water) must be safe in epidemiological, radiation, harmless in its chemical composition and have favorable organoleptic properties. The quality of water is determined by a number of indicators (the content of certain impurities), the maximum permissible values of which are established by the relevant regulatory documents. Since 2010 the Ministry of Health of Ukraine approved the State Sanitary Standards and Rules “Hygienic Requirements to Drinking Water for Human Consumption” (GSanPiN 2.2.4-171-10).
Knowing your water’s specific characteristics can help you, with the help of experts, find ways to improve the quality of your water and handle the problems associated with it.
In this section, based on the above-mentioned current regulations, we would like to introduce you to the existing indicators and their values.
Taste and odor
These indicators are called organoleptic. In addition to the fact that an unpleasant taste and smell can cause unpleasant feelings or even nausea, they are indirect signs of the presence of many toxic pollutants in water. For example, a salty taste is determined by an excess of sodium chloride; bitter – by sodium sulfate or magnesium; astringent – by sulfuric iron and aluminum, excess of lime; metallic – by sulfuric iron, manganese and copper; soapy – by sodium carbonate; sweetish – by sodium bicarbonate; astringent, irritating – by styrene, while putrefactive and vegetable – by microbiological impurities multiplying in water.
Read in detail here.
The aftertaste and odour impede the use of the water for drinking purposes. In potable water, the taste and odour at a temperature of +20 °C must not exceed 2 points on a scale of 20.
Turbidity is a visually detectable parameter which is based on the quantity of suspended solids. Turbidity can be caused by inclusions of sand, clay, silt, flakes of oxidized iron, as well as fine colloidal impurities, which can only be removed by chemical coagulation or membrane separation. Read a detailed description of this parameter here
It prevents from using water both for drinking and for household purposes (allowed value – not more than 0.58 mg/l), also for feeding steam boilers and some types of production.
Such water usually has a characteristic yellowish or brownish color that is caused by natural organic substances – humic acids. They are formed in the process of natural decomposition of plant and animal raw materials and leach into natural water bodies in small amounts. Also the cause of the chromaticity can be increased concentration of iron and some organic substances of industrial origin. Prevents the use of water for some industries (e.g., high-grade paper production).
The value of oxidation more than 5,0 mg O2/The pH value indicates a high organic content and can indicate possible pollution of a source by wastewater or poor general condition of the water body (algae growth, lowering of the level, flooding, etc.). Such water is generally contaminated with microorganisms and causes foaming in steam boilers and indicates the possibility of organic growth in water-cooled heat exchangers. It cannot be used for drinking water, it requires preliminary clarification.
This parameter determines the total amount of mineral inorganic salts of calcium, magnesium, potassium, sodium, heavy metals dissolved in the water, as well as a large percentage of organic substances. A parameter used primarily to determine the total mineralization of water.
Its value in the water of a source used for drinking purposes should not exceed 1000 mg/l. An increased content of dissolved substances in the water prevents its use for feeding steam boilers due to the reduced efficiency of their operation (increased blowdown), prevents the use of water for some industries (synthetic rubber, kapron, film, condensation paper).
High hardness when used for a long time causes metabolism disorders in the human body, diseases of urogenital and cardiovascular systems; in domestic and industrial processes it causes soap overuse, increased wear of laundry, deterioration of meat and vegetables cooking, impedes water use in steam boilers and some kinds of productions (fabric dyeing, production of artificial fiber, etc.).д.). Increased carbonate hardness of supplementary water in recycled water supply systems leads to calcium carbonate deposition in heat exchangers and cooling devices (cooling towers, splash tanks).
Read more about water hardness here.
The hardness of drinking water pipes must not exceed 7 mg-eq/l and in special cases up to 10 mg-eq/l. The requirements may be more stringent for various technologies – e.g. the hardness of boiler feed water must not exceed 0.02 mg-eq/l.
Hydrogen Index (pH)
The pH value of drinking water must be between 6,5 and 8,5.
pH less than 6.5 indicates an acidic environment, which in the long term can have a negative effect on the gastrointestinal tract, pH over 8.5 indicates an alkaline environment, which can also cause some problems.
pH values along with other indicators of water quality (temperature, total alkalinity, calcium content and dry residue) indicate the ability of water to deposit calcium carbonate in water pipes and cooling equipment or cause corrosion of washed metal surfaces. Read about alkaline water and its properties.
Iron is usually characteristic of well water because it is a natural impurity in groundwater. Due to the lack of air, it does not oxidize and can reach exorbitant values in well water. Tap water is more prone to secondary contamination by iron in the pipeline, rust flakes and organofluid compounds are flushed down the pipes in the process.
Read more about iron compounds here.
Iron content in drinking water should not exceed 0.2 mg/l. Too much iron in drinking water affects its taste, causes flatulence and constipation. In domestic use can cause damage to linen and rust stains on plumbing, prevents the use of water for some industries (dyeing fabrics, film production, etc.).д.), in some cases is the cause of formation of glandular deposits in water pipes.
Sulfates and chlorides
Chlorides and sulfates are among the most abundant anions in water, and most of these inorganic compounds are completely soluble in water.
When consumed systematically, chlorides can cause abnormalities in the urinary system and, consequently, edema. This in turn leads to high blood pressure and resultant cardiovascular problems.
Sulfates cause an unpleasant bitter-salty taste to water, they can irritate the mucosa of the gastrointestinal tract, some have a laxative effect, for example, magnesium sulfate is one of the common laxatives with a rapid effect.
Sulfates and chlorides in drinking water should not exceed 250 mg/l.
Fluoride compounds affect the musculoskeletal system – the bone skeleton. More than half of the fluoride consumed is deposited in bones and teeth.
The content of fluorides in drinking water should be 0.7-1.5 mg/l. Lack of fluoride in drinking water – less than 0.5 mg/l, as well as its excess – more than 1.5 mg/l – is harmful.
Fluoride plays a role in the thyroid gland and in the absorption of trace elements, such as calcium. In the case of this element, both deficiency and excess are equally dangerous. For example, a deficiency can cause bone destruction, particularly of the teeth, and an over-abundance accumulates in the aorta and can cause calcification. Read more.
Ammonia, nitrates, nitrites
Their presence is a warning signal that a source of drinking water may have been contaminated by household or industrial wastewater.
Ammonia in high concentrations causes irritation of mucous membranes. In laboratory rabbits, sexual dysfunctions and retarded fetal growth were observed in pregnant females. At the genetic level there are changes in the structure of chromosomes, including lethal mutations.
Nitrates cause disruption of the nervous system, headaches, swelling, and as a consequence, hypertension.
Long-term exposure of rats to drinking water with high levels of ammonium resulted in decreased calcium levels in the body, changes in blood pH, and decreased body weight. As for people, people with reduced ammonia metabolism caused by liver, kidney, and kidney dysfunction are especially vulnerable. Here’s more about nitrates.
Prevents the use of water to feed high-pressure boilers (due to the deposition of silicate scale on the walls of boilers and turbine blades).
People who have long used to drink water containing high levels of silicon compounds, showed the development of pulmonary fibrosis, the formation of kidney stones and tumors. Rarely signs of chronic poisoning are fatigue, development of depression, anemia.
Introduction to Water Quality modeling
In industry, causes precipitation on pipeline surfaces.
Free Carbon Dioxide
Carbon dioxide is partially soluble in water. Carbon dioxide is its dissolved form: CO2 + H2O = H2CO3.
Despite its bactericidal properties, it can cause flatulence and stomach wall irritation.
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In industry, can cause corrosion of metals (including water pipes) and concrete structures.
The characteristic sign of the high hydrogen sulfide content in water is an unpleasant smell of rotten eggs. This pollutant is unique to oxygen-poor well water, as it quickly oxidizes in the air.
Despite the fact that it does not exhibit high toxicity for the human body, to drink such water is at least not pleasant. Irritation of the stomach walls, flatulence and other diseases of the gastrointestinal tract may be observed as a consequence of drinking such water for a long time.
Microorganisms in water
The total microbial count quantifies the presence of microorganisms in water, for drinking water it is the number of colonies of aerobic and anaerobic bacteria in 1 ml of water. It is determined by introducing a water sample into a growth medium and allowing the colonies to grow for a fixed period of time – from three days to a week. The permissible value for drinking water is 100 bacteria in 1 ml of water. One of the most dangerous pollutants is E. coli. Its presence is evidence of fecal contamination of water and is not permissible for drinking water sources. The consequence of drinking such water can be acute diarrhea, which is especially dangerous for small children.