Water analysis

Water for analysis is classified by the method of its use:

• Drinking water .
• Drinking water, packaged in containers ( bottled ).
• Natural water :
  • surface water - water permanently or temporarily located in surface water bodies (rivers, lakes, ponds, streams, swamps, precipitation (rain and snow water)),
  • unpaved (springs, wells),
  • drainage water - water that is discharged by drainage facilities for discharge into water bodies (except for landfills for household and industrial waste),
  • groundwater - water, including mineral water, located in groundwater bodies (wells);
• Process water :
  • distilled water
  • bidistilled water
  • deionized water
  • boiler room water and cooling circuits,
  • dialysis water
  • purified water (solutions).
• Wastewater .

Accordingly, each type of classification has its own recommended measurement methods, maximum permissible concentrations (MPC) of contained substances, established by sanitary rules and norms (SanPiN) . Each measurement method has its own set of indicators, which are used to study water samples.

The content of a substance dissolved in water, not exceeding the established standards, is not a pollutant. This applies to any water - from distilled to untreated sewage. Only if the MPC is exceeded, is the substance a pollutant. The norms for the content of various substances for different types of water are different. Substances that may be contained in water can be classified in different ways:

• By the type of compounds - organic and inorganic .

Today, most of the pollutants are organic compounds, since most of them are of artificial origin, and the lists of substances requiring rationing are replenished with organic compounds.

• By source of release into water - natural or man-made .

If a substance is present in the earth's crust, it will also be present in water. Contaminants entering the water as a result of human activities can increase the content of an existing ingredient or introduce a substance that was not previously present in the water. The concentration of these substances may be different.

• According to its content in water (and in living organisms, first of all) - macro - and microelements .

The salinity or salinity of water is composed of macroelements present in tens or even hundreds of mg per liter. These are, as a rule, chlorides , sulfates , bicarbonates ( anions ), calcium , magnesium , potassium , sodium ( cations ). Macronutrients have optimal ionic and atomic radii, electronic structure for the formation of biomolecules. The ratio of these substances in water may vary.
Trace elements are contained in water in very low concentrations from tenths of a mg in a liter to micrograms, and are divided into essential, toxic and essential . Trace elements, for example, include heavy metals; the MPC of some of them is very hard. Their effect on a living organism can be manifested even in very small doses, safe concentrations are too small, so the additional ingress of toxic and essential elements into the water can adversely affect the health of consumers. Some heavy metals (and not only), on the contrary, are part of vitamins, as substances necessary for health.

• By limiting hazard indicators - organoleptic , general sanitary and sanitary-toxicological.

Organoleptic include not only those indicators that can be estimated by the sensory organs, but also those that can change the organoleptic properties of water, for example, cause odor, the appearance of foam or film on the surface of the water. By hazard class - from low hazard to extremely dangerous.
There are other classifications, but the above conditions are taken into account in the rationing of water.

Iron

In groundwater, mainly dissolved ferrous iron is present in the form of Fe2 + ions.
Ferric iron appears after the contact of such water with air and in worn-out water distribution systems when water contacts the surface of the pipes. In surface waters, iron is already oxidized to a trivalent state and, in addition, is part of organic complexes and iron bacteria.
The standard content of total iron in drinking water is not more than 0.3 mg / l . The iron content in water above the norm contributes to the accumulation of sediment in the water supply system, intensive painting of plumbing equipment.
Iron imparts an unpleasant red-brown color to water, impairs its taste, causes the development of iron bacteria, sedimentation in the pipes and their clogging. A high iron content in water leads to adverse effects on the skin, can affect the morphological composition of the blood, and contributes to allergic reactions. Also, iron adversely affects the reproductive system.

Water hardness

(total content of calcium and magnesium salts) According to WHO standards, the optimal hardness of drinking water is 1.0-2.0 mEq / l .
As a rule, the hardness level of natural waters is much higher than these values. In everyday conditions, an excess of hardness salts leads to overgrowing of heating surfaces in boilers, teapots, pipes, the deposition of salts on plumbing fixtures and their failure, and also leaves a deposit on the hair and skin of a person, creating a feeling of their “hardness”. When washing, interacting with the surfactants of soap or washing powders, hardness salts bind them and require a greater consumption. In the food industry, hard water degrades the quality of products, causing salt to precipitate during storage.
In the energy sector, accidental short-term hard water entering the system very quickly destroys heat-exchange equipment and pipelines. Even a small layer of salt deposits on the surface of heat exchange equipment leads to a sharp decrease in the heat transfer coefficient and an increase in fuel consumption. Therefore, the water hardness for these purposes is limited by very small values ​​of 0.03-0.05 mEq / L.

Copper

Copper and its compounds are widespread in the environment, so they are often found in natural waters. Concentrations of copper in natural waters usually amount to tenths of mg / l, in drinking water they can increase due to leaching from pipes and fittings from materials. Copper gives water an unpleasant astringent taste in low concentrations, which limits its content in drinking water. This circumstance must be taken into account when choosing a source of water supply for the production of bottled drinking water. If copper is found in drinking water in an amount of more than 1.0 mg / l , the composition of the water is adjusted using cation exchange resins.

Organic Compounds

Several thousand organic substances of various chemical classes and groups were found in the water of water supply sources.

Organic compounds of natural origin (humic substances, various amines) and technogenic origin (surfactants) are able to change the organoleptic properties of water (smell, taste, color, turbidity, foaming ability, film formation), which allows them to identify and limit the content in drinking water. At the same time, a huge number of organic compounds are very unstable and prone to continuous transformation, therefore, direct determination of the concentration of organic substances in drinking water is difficult, which is why it is customary to characterize their content indirectly in mg O ₂ / L, determining, for example, permanganate oxidation drinking water.

The value of permanganate oxidation above 20 mg O ₂ / L indicates the content of easily oxidized organic compounds in water, many of which adversely affect the liver, kidneys, and reproductive function of the body. When disinfecting such water by chlorination, chlorohydrocarbons are formed, which are significantly more harmful to public health.

If, when analyzing a water sample, it was found that the value of permanganate oxidation is higher than 5, and even more so, 20 mg O ₂ / L, such water requires purification from organic contaminants.

Nitrates

Nitrogen compounds in the form of nitrates and nitrites are present in surface and underground water sources. Currently, there is a constant increase in their concentration due to the widespread use of nitrate fertilizers, the excess of which with groundwater enters water sources. According to sanitary rules and regulations, in centralized water supply, the nitrate content should not exceed 45 mg / l , nitrite - 3 mg / l .
Nitrates in a concentration of more than 20 mg / l have a toxic effect on the human body. The constant use of water with a high content of nitrates leads to diseases of the blood, cardiovascular system.
If nitrates are detected in the water sample in an amount higher than the norm, they resort to water purification using reverse osmosis or ion exchange.

Maximum permissible discharge (MPD or DS) .

There are a number of measurement procedures that are entered in the Federal RegisterMVI , they were developed by the Center for Research and Control of Water. Examples of methods:

• CV 1.01.11-98 “A” - Methodology for measuring alkalinity in samples of drinking and natural water by the titrimetric method
• CV 1.01.14-98 “A” - Methodology for the measurement of permangent oxidation of samples of drinking and natural waters
• CV 1.01.15-00 “A” - Methodology for measuring biochemical oxygen consumption (BOD5) in samples of drinking and natural waters by the titrimetric method

A complete list of methods can be found on the Methodological Help page. There you can also see the principles of the methods, measurement ranges, error characteristics and designations according to the federal register of MVI, the State Register of Methods of the KHA Ministry of Natural Resources of Russia

To assess the quality of water in rivers and reservoirs, they are divided according to pollution into classes from 1 (conditionally clean) to 5 (extremely dirty). Class 3 has subclasses a and b , and class 4 has subclasses a, b, c, d .

Classes are based on the intervals of the specific combinatorial index of water pollution ( UKIZV ) depending on the number of critical indicators of pollution (KPZ). The value of UKISV is determined by the frequency and frequency of exceeding the MPC for several indicators and can vary in waters of various degrees of pollution from 1 to 16 (for pure water 0). A higher index value corresponds to worse water quality.