Quality indicators of water

The composition of natural waters is very diverse and is a complex, constantly changing system that contains mineral and organic matter in suspended, colloidal and truly dissolved.

water quality indicators are divided into:

  • physical (temperature, suspended solids, color, odor, taste, etc.);
  • chemical (hardness, alkalinity, active reaction, oxidation, dry residue, etc.);
  • biological and bacteriological (total number of bacteria and coli index al.).

The quality of water for domestic and drinking purposes is determined by a number of indicators (physical, chemical and sanitary-bacteriological), the limit values ​​which are defined by the relevant regulatory documents.

At the same time, a well-studied the harmful effects of maximum permissible concentration (MPC) of the impurities of chemical elements in the water, but not enough (or not learned) the lack of concentration of impurities for the normal functioning of a living organism.

Thus, mineralization of water (the amount of dissolved salts) is mixed parameter. Studies in recent years have shown an adverse effect on the human body of drinking water with a salinity of more than 1500 mg / l and below 30-50 mg / l

chemical water parameters

Dissolved oxygen.

The main sources of oxygen in water bodies is gas exchange with the atmosphere (atmospheric reaeration), photosynthesis, as well as rain and melt water, which, as a rule, are supersaturated with oxygen. Oxidation reactions are the main source of energy for most aquatic organisms. The main consumers of dissolved oxygen are the processes of respiration of aquatic organisms and oxidation of organic substances. Low dissolved oxygen (anaerobic conditions) affects the whole complex biochemical and ecological processes in the water body, leading to the death of aquatic organisms and poisoning of water decomposition products of organisms.

Chemical oxygen demand ( COD ).

This parameter is defined as the amount of oxygen required for oxidation of the chemical contained in a unit volume of water of organic and mineral substances. COD value gives an indication of water pollution oxidizing agents, both organic and inorganic, but does not provide information on the composition of pollution. Therefore, COD refers to generalized indicators.

Biochemical oxygen demand ( BOD ).

BOD is defined as the amount of oxygen spent in the oxidation of biochemical water contained in a unit volume of organic substances for a certain period of time. In practice, the biochemical oxygen consumption estimated for five days (BOD 5) and twenty days (BPK20). BPK20obychno interpreted as a complete BOD (BOD), which is a sign of the beginning of nitrification processes in the water sample. BOD also refers to generalized indicators, because it provides an estimate of the overall pollution of water easily oxidized organic substances.

PH value (pH).

In natural water the hydrogen ion concentration depends mainly on the ratio of the concentrations of carbonic acid and its ions. The sources of the content of hydrogen ions in the water are also the humic acids present in acidic soils, especially in the marsh water, hydrolysis of salts of heavy metals. Depends on the pH development of aquatic plants, the character of the productive protsessov.Pri room temperature neutral solution pH = 7 in acidic solutions of pH <7, and in the alkaline pH> 7. Around pH of the aqueous solution can be determined using indicators.


Nitrogen may be present in natural waters in the form of free molecules and N2 of various compounds in the dissolved, colloidal or suspended state. In general, nitrogen, natural water taken from the organic and mineral form. The main sources of nitrogen inputs are vnutrivodoemnye processes, gas exchange with the atmosphere, precipitation and anthropogenic sources. Various forms of nitrogen may cross one another in the nitrogen cycle. The high nitrogen content accelerates eutrophication of water bodies, thus worsening the organoleptic and general chemical indicators of quality of water.

dissolved oxygen

Dissolved oxygen

Oxygen is constantly present in dissolved form in surface waters. The content of dissolved oxygen in water characterizes the oxygen regime...

nitrogen in water

Nitrogen level in water

Nitrogen-containing compounds are found in surface waters in a dissolved, colloidal and suspended state and can change from one state to a...

water ph level

Water PH value

PH is the hydrogen index, (from the Latin words "potentia hydrogeni" is the force of hydrogen, or "pondus hydrogenii" is the weight of hyd...

specific water quality indicators

Specific indicators of water quality

The most frequent specific indicators of water quality include: Phenols. The content of phenols in the water, along with the arrival of an...

minerals in water

Mineral composition of water

 Mineral composition is determined by the total content of the seven major ions: K +, Na +, + Ca2, Mg2 +, SO42-, HCO3-. The main source...

physical kind of water

Water temperature.

The temperature of the water bodies is the result of simultaneous action of solar radiation, heat exchange with the atmosphere, the heat transfer flows, mixing of water masses and receipts heated water from external sources. Temperature affects virtually all of the processes that affect the composition and properties of water. The temperature of the surface water sources depends on the air temperature, its humidity, the speed and nature of the water movement, and several other factors. It can vary within wide limits. Water temperature is relatively constant underground sources and is typically 4-8 degrees Celsius or 40-47 degrees Fahrenheit. The optimum temperature of the water for drinking purposes is considered to be 7-11 degrees Celsius or 45-52 degrees Fahrenheit.


Water smell determined by living and dead organisms, plant residues, the specific substances secreted by some algae and microorganisms, as well as the presence in water of dissolved gases - chlorine, ammonia, hydrogen sulfide, mercaptans and organic and organochlorine contaminants. The smell of drinking water may indicate it unfit for consumption due to organic pollution.

There are natural scents: aromatic, marsh, putrid, woody, earthy, musty, fishy, ​​grassy, ​​indefinite, and hydrogen sulfide. Scents of artificial origin called for defining their stuff: phenol, chlorophenol, oil, resin and so on.

The intensity of the smell organoleptically measured on a scale:

  • 0 points - the smell and the taste is not detected
  • 1 point - very slight smell or taste (it detects only an experienced researcher)
  • 2 points - weak odor or taste, attention layman
  • 3 points - noticeable odor or taste, it is easy to detect and are the cause of complaints
  • 4 points - a distinct odor or taste that can make refrain from the use of water
  • 5 points - so a strong smell or taste of the water is unsuitable for drinking completely.


The taste due to the presence of solutes in the water and may be salty, bitter, sweet and sour. Natural waters have, as a rule, only salty and bitter taste. Salty taste is caused by the content of sodium chloride, bitter - magnesium sulphate. Sour taste of the water gives a large amount of the dissolved carbon dioxide. Water may also have an ink or glandular taste caused by iron and manganese salts or astringent taste caused by calcium sulfate.


Transparency of water depends on the sunshine dispersion in water of the organic substances and mineral origin, located in the water in a suspended and colloidal. Transparency determines the course of biochemical processes that require illumination (primary production, photolysis). Opacity is measured in inches.


Turbidity is determined by the content of suspended substances. Comparing with the same coverage of the sample studied water and distilled water samples of the same volume, a certain number of artificial turbid suspension standard, the sample is selected with the most suitable concentration. Turbidity can be expressed in different units NTU, FNU, FTU, FAU, and JTU. Turbidity underground sources, usually small and caused a suspension of iron hydroxide. In most surface water turbidity due to the presence of phytoplankton and zooplankton, clay or silt particles, so the value depends on the time of the flood and the changes during the year.


The color of water is determined by the content of organic colored compounds that may indicate contamination of the water (natural and drinking) or on certain biochemical processes in natural waters. High chroma decreases organoleptic properties of the water reduces the concentration of dissolved oxygen. Colour is measured in gradusah.Tsvetnost water - color intensity, expressed by the platinum-cobalt scale. One degree of the scale corresponds to color 1 liter of water, colored by the addition of 1 mg of salt - chloroplatinate cobalt. Colour of water of groundwater caused by iron compounds, at least - humic substances (primer, peat, permafrost water); color surface - flowering reservoirs.

The content of suspended solids.

Suspended solids impact on the depth of penetration of sunlight, degrade aquatic life activity, leading to siltation of water bodies, causing them to environmental aging deteriorates the organoleptic characteristics of drinking water.

water transparency measurement


Transparency (or light transmission) of natural waters is due to their color and turbidity, i.e. The content of various colored and suspen...

turbidity of water


The turbidity of natural waters is caused by the presence of fine impurities caused by insoluble or colloidal inorganic and organic substa...

suspended solids on water

suspended solids

Suspended solids present in natural waters consist of particles of clay, sand, silt, suspended organic and inorganic substances, plankton...

Chromaticity parameter of water


The water quality index, which characterizes the intensity of the color of water and is caused by the content of colored compounds; Is exp...

water smell

Water smell

Chemically pure water completely devoid of taste and smell. However, the nature of this water does not occur - it always contains in its com...

radon gas in water

Radon and radioactivity of water

It has been established that the basic background radiation on the planet (at least so far) is created due to natural sources of radiation....

bacteria in water

The surface water supply sources bacteria and microorganisms get together with sewage and rainwater, with the animals. Water from artesian sources has a low levels of bacterial contamination .

Bacteria in water are divided into :

  • pathogenic (disease-causing)
  • saprophytic (involved in the processing of dead plant or animal organisms).

The direct detection of water pathogens of infectious diseases is difficult due to the fact that the methods for isolating pathogens, especially viruses, are complex and do not allow in the short term to give an opinion on the epidemiological characteristics of the water.

Therefore, the sanitary-bacteriological evaluation is made based on indirect indicators, which are:

  • Microbial count
  • The content of E. coli.

Both of these indicators are generally accepted on the basis of long-term observations, indicating that the more polluted the water, the more it saprophytic and intestinal microflora and, conversely, the less it is dirty (particularly the secretions of human and domestic waste waters), the less of water and the number of bacteria, in particular E. coli, and hence the weaker expressed possibility of infectious diseases in the use of such water.

Microbial number (the total number of microbes in a certain volume of water) is an indicative figure, as calculated in the sample are all germs without their identification; it refers to the contamination of water any liquid waste, garbage and so on. e., which are not guaranteed by their content of pathogenic bacteria.

Detection of E. coli in water is of great sanitary and indicative value. This is due to the fact that the place of its natural habitat is the large intestine of humans and animals. In the environment, it can only get with the faeces. Therefore, the detection of E. coli in water indicates fecal contamination it, which may contain, in addition to the B. coli, pathogenic enteric bacteria - pathogens of typhoid, dysentery, paratyphoid. E. coli is called the index of fecal contamination of water.

In order to determine the degree of epidemiological danger of water against intestinal infections, it is necessary to establish the intensity of fecal contamination of water, ie. E. To determine the number of coliform bacteria in the water, since the greater the B. coli in the water, the more it is contaminated with faeces.

Quantitatively, the presence of E. coli is characterized by two parameters:

  • Coli titer - the smallest amount of water (in ml), which contains the Escherichia coli one,
  • Coli index - the number of coliform bacteria in 1 liter of water.

Some authors propose the use of sanitary and bacteriological water assessment, in addition to E. coli, fecal streptococcus, Clostridium perfringens Welenii, bacteriophage. Develops methods for detecting pathogenic enteric bacteria using hapten (a non-specific antigen), and others.

In the study of water sources of water, especially open reservoirs, great importance attaches to some other indicators and techniques

For example, in the study of water in water sources, particularly in open water, it is very important sanitary and topographic survey.

The aim of this study is to identify the watershed that feeds the pond, factors that could degrade water quality. We study the terrain, the soil, the presence of forests. Characterized by placing human settlements, industrial, agricultural use of the territory.

Of particular importance is the study of the degree of population of the territory, since the higher the population density, the more waste is formed of organic origin and the more real the possibility of getting them into the body of water and the occurrence of epidemics of water. It is necessary to obtain information on the use of the water body in the economic order, paying particular attention to water transport and fisheries, the use of water bodies for sport, on the incidence of the population of the area.

Of great importance are hydrometric measurements (depth, flow velocity, flow rate, e.t.c.).It plays an important role biological analysis, since it is known that large amounts of water pond plants and animals affect the water quality. By virtue of this aquatic life are used as a demonstration of organisms sensitive to changes in the conditions of life of the reservoir. These biological organisms called saprobity (sapros - putrid).

There are four zones saprobity:

  • Polysaprobic
  • α-mesosaprobic
  • β-mesosaprobic
  • Oligosaprobic

Each of these corresponds to a specific flora and fauna, as well as the degree of the oxygen content in the water.

Detection of helminth eggs and cysts of intestinal protozoa also has a large epidemiological and sanitary-hygienic value.

water saprobity factor

Water saprobity

Among the biological methods of analyzing surface waters, saprobiological analysis occupies one of the main places. Progressive pollution...

biochemical oxygen demand

Biochemical oxygen demand

The degree of contamination of both wastewater and water in reservoirs with organic substances contained in dissolved form and in the form...

e-coli bacteria in water

Koli-index, coli-titer

Koli-index, coli-titer - quantitative indicators of fecal contamination of water, soil, food products and other objects of the external en...