Basic physical water quality indicators:
Water temperature. In water bodies, temperature is the result of the simultaneous action of solar radiation, heat exchange with the atmosphere, heat transfer by currents, mixing of water masses and the flow of heated water from external sources. Temperature affects almost all processes, on which the composition and properties of water depend. Water temperature is measured in degrees Celsius (°C).
Scent. The smell of water is created by specific substances, entering the water as a result of the vital activity of hydrobionts, decomposition of organic matter, chemical interaction of components contained in water and intake from external sources. The smell of drinking water may indicate that it is unfit for drinking due to contamination with organic substances.. The smell of water is measured in points.
Transparency. The transparency of water depends on the degree of scattering of sunlight in the water by substances of organic and mineral origin., suspended and colloidal in water. Transparency determines the course of biochemical processes, requiring illumination (primary production, photolysis). Transparency is measured in centimeters.
Chroma. The color of water is determined by the content of organic colored compounds, which may indicate water contamination (natural and drinking) or on certain biochemical processes in natural waters. High color reduces the organoleptic properties of water, reduces dissolved oxygen content. Color is measured in degrees.
Suspended solids content. Suspended solids affect the penetration depth of sunlight, impair the life activity of aquatic organisms, lead to siltation of water bodies, causing their environmental aging, sharply worsens the organoleptic characteristics of drinking water. Suspended solids content is measured in g/m3 (mg/l).
Basic chemical water quality indicators:
Dissolved oxygen. The main sources of oxygen supply to water bodies are gas exchange with the atmosphere (atmospheric reaeration), photosynthesis, as well as rain and melt water, which, usually, oversaturated with oxygen. Oxidative reactions are the main sources 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 entire complex of biochemical and ecological processes in a water body, leading to the death of aquatic organisms and water poisoning by decomposition products of organisms.
Chemical oxygen demand. COD is defined as the amount of oxygen, necessary for the chemical oxidation of organic and mineral substances contained in a unit volume of water. The COD value allows us to judge the contamination of water with oxidizable substances, as organic, and inorganic, but does not provide information about the composition of the pollution. Therefore, COD is classified as a general indicator.
Biochemical oxygen demand (BPC). BOD is defined as the amount of oxygen, spent on the biochemical oxidation of organic substances contained in a unit volume of water over a certain period of time. In Ukraine, in practice, BOD is assessed in five days (BPC5) and twenty days (BPK20). BOD20 is usually interpreted as total BOD (BPKfull), a sign of which is the beginning of nitrification processes in a water sample. BOD also refers to general indicators, since it serves as an assessment of the total water pollution by easily oxidized organic substances.
pH value (pH). In natural waters, the concentration of hydrogen ions depends, mainly, on the ratio of concentrations of carbonic acid and its ions. Humic acids are also sources of hydrogen ions in water., present in acidic soils and, especially, in swamp waters, hydrolysis of heavy metal salts. The development of aquatic plants depends on pH, nature of production processes.
Nitrogen. Nitrogen can be found in natural waters in the form of free N2 molecules and various compounds in dissolved, colloidal or suspended state. In the total nitrogen of natural waters, it is customary to distinguish organic and mineral forms. The main sources of nitrogen input are intra-reservoir processes, gas exchange with the atmosphere, precipitation and anthropogenic sources. Different forms of nitrogen can change from one another to another during the nitrogen cycle. High nitrogen content accelerates the processes of eutrophication of water bodies, thereby worsening the organoleptic and general chemical indicators of water quality.
Mineral composition.
Mineral composition is determined by the total content of seven main ions: K+, Na+, Sa2+, Mg2+, SO42-, HCO3-. The main sources of increased mineralization are groundwater and wastewater. From the point of view of the impact on humans and aquatic organisms, unfavorable are both high, and excessively low levels of water mineralization.
Nitrate. With prolonged consumption of drinking water and food products, containing significant amounts of nitrates (от 25 до 100 mg/dm3 for nitrogen), the concentration of methemoglobin in the blood increases sharply. Methemoglobinemia is extremely severe in infants (first of all, artificially fed formula milk, cooked in water with increased – order 200 mg/dm3 – nitrate content) and among people, suffering from cardiovascular diseases.
In the effects on humans, the primary toxicity of the nitrate ion itself is distinguished; secondary, associated with the formation of nitrite ion, and tertiary, caused by the formation of nitrosamines from nitrites and amines. The lethal dose of nitrates for humans is 8-15 Mr; acceptable daily intake according to FAO/WHO recommendations – 5 mg/kg body weight.
Sulfate. The concentration of sulfate in natural water varies widely. In river waters and fresh lake waters, the content of sulfates often varies from 5-10 до 60 mg/dm3, in rainwater – от 1 до 10 mg/dm3. In groundwater, the content of sulfates often reaches significantly higher values.. Elevated sulfate contents worsen the organoleptic properties of water and have a physiological effect on the human body. Because sulfate has laxative properties, its maximum permissible concentration is strictly regulated by regulations.
Fluorides. Increased amounts of fluoride in water (more 1,5 mg/dm3) have harmful effects on people and animals, causing bone disease (fluorosis). Fluoride content in drinking water is limited. However, very low levels of fluoride in drinking water (less 0,01 mg/dm3) also harmful to health, causing the risk of dental caries.
Rigidity. Increased amounts of fluoride in water (more 1,5 mg/dm3) have harmful effects on people and animals, causing bone disease (fluorosis). Fluoride content in drinking water is limited. However, very low levels of fluoride in drinking water (less 0,01 mg/dm3) also harmful to health, causing the risk of dental caries. Hardness usually predominates, due to calcium ions (до 70%); however, in some cases magnesium hardness can reach 50=60%. The hardness of sea water and oceans is much higher (tens and hundreds of mEq/dm3). The hardness of surface waters is subject to noticeable seasonal fluctuations, usually reaching its highest value at the end of winter and its lowest during high water.
High water hardness worsens the organoleptic properties of water, giving it a bitter taste and affecting the digestive organs.
The most common specific indicators of water quality include:
Phenol. Phenol content in water, along with input from anthropogenic sources, can be determined by the metabolism of hydrobionts and the biochemical transformation of organic substances. The source of phenols is humic substances, formed in soils and peat bogs. Phenols have a toxic effect on hydrobionts and worsen the organoleptic properties of water.
Petroleum products. Petroleum products include fuels, масла, bitumens and some other products, representing a mixture of hydrocarbons of various classes. Sources of petroleum products are leaks during their production, processing and transportation, as well as wastewater. A small amount of petroleum products may be released as a result of intra-reservoir processes. The hydrocarbons contained in petroleum products have toxic and, in some ways, narcotic effects on living organisms, affecting the cardiovascular and nervous systems.
PAV and SPAV. To surfactants (PAV) include organic matter, having a pronounced ability to adsorb on the interface “air-liquid”. The vast majority of surfactants released into water are synthetic. (SLEEP). Surfactants have a toxic effect on aquatic organisms and humans, worsen the gas exchange of a water body with the atmosphere, reduce the intensity of intra-reservoir processes, worsen the organoleptic properties of water. Surfactants are classified as slowly decomposing substances.
Pesticides. Pesticides are understood as a large group of artificial organochlorine and organophosphorus substances, used for weed control, insects and rodents. The main source of their supply is surface and drainage runoff from agricultural areas. Pesticides are toxic, mutagenic and cumulative effect, are destroyed slowly.
Heavy metals. The most common heavy metals include lead, copper, zinc. Heavy metals have mutagenic and toxic effects, sharply reduce the intensity of biochemical processes in water bodies.
Chemical indicators are measured in g/m3, mg/dm3 (mg/l).