Enough has been written about pollution and the shortage of drinking water on the planet. In one of the richest countries in water resources, Russia, only one percent of the source water from surface drinking water supplies meets quality standards. In Karelia, a country of rivers and lakes, where the availability of water resources exceeds the Russian average by 2-3 times, about 70% of water samples entering the distribution networks of settlements do not meet the hygienic requirements for drinking water. This is largely due to intensive technogenic and agro-industrial activities aimed primarily at meeting the immediate needs of humanity and insufficient attention to saving water resources for subsequent generations. But not only, “thanks to” this, natural water, which is vital for humanity, is in a state close to critical.
Natural water receives contamination from a variety of areas. Sources of water pollution are extremely diverse. First of all, these are wastewater from cities and industrial enterprises. The most water-intensive industries are mining, steel, chemicals, petrochemicals, pulp and paper, and food processing. They consume up to 70% of all water spent in industry. Also, thermal and nuclear power plants use a huge amount of water for cooling; the discharged water leads to thermal pollution of water bodies, which disrupts the thermal, hydrochemical and hydrobiological regimes of water bodies.
In recent years, in a number of areas, they have been “competed” by wastewater from livestock farms and water coming from irrigation areas and rainfed lands. Agriculture uses 60-80% of all fresh water. In many regions of the world, water pollution is increasingly associated with precipitation. Changes in the regime of rivers and lakes play a certain role in the deterioration of water quality.
Due to the huge problem of pollution of natural waters, there are different methods and methods of water purification. But despite this, one of the most valuable properties of natural waters is their ability to self-purify.
Self-purification of water is the restoration of their natural properties in rivers, lakes and other water bodies, occurring naturally as a result of interrelated physicochemical, biochemical and other processes (turbulent diffusion, oxidation, sorption, adsorption, etc.). The ability of rivers and lakes to self-purify is closely dependent on many natural factors. These factors include: biological - complex processes of interaction of aquatic plant organisms with the components of incoming wastewater; hydrological - dilution and mixing of contaminants with the bulk of the water; physical - the influence of solar radiation and temperature; mechanical - sedimentation of suspended particles; chemical - the transformation of organic substances into mineral substances (i.e. mineralization).
When wastewater enters a reservoir, the wastewater mixes with the water of the reservoir and reduces the concentration of pollutants. A complete change of water in rivers takes on average 16 days, in swamps - 5 days, in lakes - 17 years. The difference in time is associated with different periods of complete water exchange in different watercourses and reservoirs.
The most intensive self-purification of water in reservoirs and streams occurs in the warm season, when biological activity in aquatic ecosystems is greatest. Self-purification occurs faster in fast-flowing rivers. Most of the suspended contaminants are deposited, these are suspended mineral and organic particles, helminth eggs and microorganisms, due to this, the water clarifies and becomes transparent.
Reducing the concentration of inorganic substances polluting water bodies occurs by neutralizing acids and alkalis due to the natural buffering of natural waters, the formation of sparingly soluble compounds, hydrolysis, sorption and precipitation. The concentration of organic substances and their toxicity are reduced due to chemical and biochemical oxidation.
One of the important processes of water self-purification is the mineralization of organic substances, i.e. the formation of mineral substances from organic substances under the influence of biological, chemical and other factors. With mineralization in water, the amount of organic substances decreases, along with this, the organic matter of microbes can also oxidize, and consequently, some of the bacteria die.
During the process of self-purification, saprophytes and pathogenic microorganisms die off. They die as a result of water becoming depleted of nutrients; bactericidal effect of ultraviolet rays of the sun, which penetrate more than 1 m into the water column; the influence of bacteriophages and antibiotic substances secreted by saprophytes; unfavorable temperature conditions; antagonistic effects of aquatic organisms and other factors. A significant role in the processes of self-purification of water is played by the so-called saprophytic microflora and aquatic organisms. Some representatives of the microflora of water bodies have antagonistic properties to pathogenic microorganisms, which leads to the death of the latter. The simplest aquatic organisms, as well as zooplankton (crustaceans, rotifers, etc.), passing water through their intestines, destroy a huge number of bacteria. Bacteriophages that enter a body of water also have an effect on pathogenic organisms.
Self-purification of groundwater occurs due to filtration through the soil and due to mineralization processes.
It must be remembered that the ability of reservoirs to self-purify is limited. Compounds of lead, copper, zinc, and mercury, which can enter water bodies with wastewater, causing a toxic effect on the body of animals, can slow down the processes of self-purification of water and worsen its organoleptic properties.
Of great importance is the distribution of aquatic vegetation (dense thickets of reeds, reeds and cattails along the banks), which acts as a kind of biofilter in them. The high cleaning ability of aquatic plants is widely used in many industrial enterprises, both in our country and abroad. For this purpose, various artificial settling tanks are created, in which lake and swamp vegetation is planted, which effectively purifies polluted waters.
In recent years, artificial aeration has become widespread - one of the effective ways to purify contaminated water, when the self-purification process is sharply reduced due to a deficiency of oxygen dissolved in water. Good water aeration ensures the activation of oxidative, biological and other processes, helping to purify the water. For this purpose, special aerators are installed in reservoirs and watercourses or at aeration stations before discharging contaminated water.
Bibliography
1. Avakyan A.B., Shirokov V.M. Integrated use and protection of water resources: Textbook. allowance. - Mn.: Un-koe, 1999;
2. Bernard Nebel “Science of the Environment” (In 2 volumes), “MIR” M. 1993;
3. Belichenko Yu.P., Shvetsov M.N. Rational use and protection of water resources. - M.: Rosselkhozizdat, 2006
Open water bodies are almost continuously exposed to various types of pollution. However, in large reservoirs there is no sharp deterioration in water quality. This is explained by the fact that rivers, lakes, and reservoirs, under the influence of various physicochemical and biological processes, have the ability to self-purify themselves of suspended particles, organic substances, microorganisms and other contaminants.
The process of self-purification of open reservoirs occurs under the influence of various factors that act simultaneously in various combinations.
These factors include: hydrological - dilution and mixing of pollutants with the bulk of the water; mechanical - sedimentation of suspended particles; physical - the influence of solar radiation and temperature; biological - complex processes of interaction of aquatic plant organisms with the components of incoming wastewater; chemical - the transformation of organic substances into mineral substances (mineralization).
During the process of self-purification, saprophytes and pathogenic microorganisms die off. They die as a result of depletion of water in nutrients, the bactericidal effect of ultraviolet rays of the sun, which penetrate into the water column by more than
- m, the influence of bacteriophages and antibiotic substances secreted by saprophytes, unfavorable temperature conditions, the antagonistic effects of aquatic organisms and other factors. The processes of self-purification of water occur more intensively in the warm season, as well as in flowing reservoirs - rivers. Low-flow reservoirs (ponds, lakes, reservoirs) undergo much less self-purification, since the flow of water in them is slowed down, and suspended particles settle to the bottom, resulting in siltation of the reservoir and deterioration in water quality.
When water bodies are heavily polluted by domestic industrial wastewater, self-purification processes usually slow down and even stop completely. Industrial wastewater introduces significant amounts of various chemicals into the reservoir, which worsen the organoleptic properties of water and give it an unpleasant taste and smell (chlorobenzene, dichloroethane, styrene, oil, etc.), and also affect the biological and chemical processes of water self-purification (acetone, methanol, ethylene glycol, etc.).
The so-called saprophytic microflora and aquatic organisms are essential in the processes of water self-purification. Some representatives of the microflora of water bodies have antagonistic properties to pathogenic microorganisms, which leads to the death of these microbes.
Protozoa are characterized by the greatest antimicrobial effect. Microbe eaters - bacteriophages that enter a body of water also have an effect on pathogenic and pathogenic microorganisms.
Under the influence of natural factors, open bodies of water (rivers, lakes and reservoirs), like soil, have the ability to be freed from contaminants that have entered them. In rivers, self-purification requires a water run of at least 15 km from the place of pollution, provided that there are no new contaminants along the water flow path. The speed of self-purification depends on the abundance of water, the speed of water flow and wind, which contribute to the mixing of water in the reservoir. In lakes and reservoirs, the more intensely the water is purified, the larger the volume of the sources themselves. In small reservoirs, self-purification processes are extremely weakly expressed.
Self-purification of water occurs as a result of mechanical, physico-chemical and biological processes. In this case, the incoming contaminants are diluted with the water of the reservoir, substances suspended in the water gradually settle to the bottom, and organic substances undergo oxidation due to oxygen dissolved in the water. In this case, aerobic processes occur mainly in the upper layers of the reservoir, and anaerobic ones - at the bottom
Rice. 6
a body of water where air oxygen does not reach. As a result of these processes, organic substances, breaking down into less complex ones, are gradually mineralized.
The process of mineralization of organic substances in water and the final products of the breakdown of protein substrates are shown in Fig. 6.
The processes of self-purification of water are also facilitated by protozoa, rotifers, crustaceans, mollusks and some plant organisms that feed on organic matter that feed on bacteria. From a sanitary point of view, self-purification of water is a very useful phenomenon in nature. However, this process in open reservoirs is not unlimited - with severe and constant pollution, self-purification of water becomes insufficient. This is often observed with the uncontrolled release of domestic fecal and industrial wastewater into water bodies, which causes a significant accumulation of rotting sludge, the appearance of toxic chemical compounds, the development of polysaprobic flora and massive fish death.
In practical work, there is a need to determine the duration of contamination of water sources with organic waste. To do this, you can use the following scale:
If only ammonia of organic origin is found in the water, this indicates fresh contamination (usually urine or feces). The organic origin of ammonia is confirmed by the presence in water at the same time of such important indicators as low coli-titer, increased oxidability and general hardness.
If chlorides are found in water, in addition to ammonia, it indicates that the pollution of the reservoir occurred relatively recently, because chlorides usually appear when protein substances are destroyed after ammonia.
The presence of ammonia, chlorides and nitrous acid (nitrites) in the same water sample gives reason to believe that the process of decomposition of organic substances is in full swing.
The appearance in water, in addition to ammonia, chlorides, nitrous acid, and also salts of nitric acid (nitrates), indicates that a significant period of time has passed since the moment of contamination, but fresh contamination is taking place.
The presence of chlorides, nitric and nitrous acids in water indicates that there is no fresh pollution, but the process of mineralization of organic substances continues.
If a long period of time has passed since the water was contaminated with organic substances, then only nitrous and nitric acids can be detected in it. The presence of only nitric acid salts in the water indicates that the mineralization process has completed completely and the water can be used for watering animals.
4.8.
METHODS OF WATER PURIFICATION AND DISINFECTION
Water used in agricultural enterprises and farms may not meet some SanPiN requirements
- 1074-901, approved by the Chief State Sanitary Doctor of the Russian Federation
- g., for centralized water supply, and SanPiN 2.1.4. 1176-02, approved by the Chief Sanitary Doctor of the Russian Federation on November 26, 2002, for neutralized water supply, as well as veterinary, sanitary and hygienic standards.
Measures to improve the organoleptic properties of water. In the practice of water supply to livestock farms and farms, among the measures aimed at improving the quality of water and purifying it from various impurities, sedimentation, coagulation and filtration are used.
Settling - special closed underground containers (usually reinforced concrete pools) are filled with water for 4-8 hours. During this time, coarse suspended particles and some microorganisms (up to 60-70%) settle to the bottom of the tank, and the water becomes clear.
In agricultural production conditions, water can also be settled in open reservoirs, reservoirs, and dams, if they are well protected from pollution.
Coagulation of water and sedimentation of suspended matter is a reagent method for improving water quality using special substances - coagulants. The most commonly used is crude aluminum sulfate L12 (804 18N20), containing 33% anhydrous aluminum sulfate and up to 23% insoluble impurities. Currently, purified alumina is produced containing no more than 1% insoluble impurities. For coagulation, iron sulfate (Fe804-7I20) is also used, which forms ferric hydroxide in water, ferric chloride (FeCl2), which is highly soluble in water and forms large, quickly settling flakes of iron hydroxide, sodium aluminate (CaAl102). Better precipitation results are obtained with the simultaneous use of ferric chloride in a mixture with aluminum sulfate and lime. Water treatment processes using reagents are more intensive and are accompanied by higher efficiency. If sedimentation of a mass of suspended substances using the reagent method requires 2-4 hours, then the non-reagent method may require several days. The dose of the coagulant is determined depending on the turbidity of the water from 30 to 200 mg/l. It is added in powder form or in the form of a 2-5% aqueous solution.
Considering the insufficient effect of water treatment with mineral coagulants, flocculants have recently begun to be used - activated silicic acid, polyacrylamide (PAA), etc.
Filters and water filtration. In addition to purifying water from mechanical impurities, using filters, clear, colorless water is obtained, the number of microorganisms in it is reduced by 60-95%, and E. coli - by 9099%.
Based on the nature (type) of the filter base, filters are divided into mesh (microfilters, microsieves), frame or alluvial and the most common granular (sand, anthracite). The particle sizes of the filter material, as well as the thickness of the layer, allow granular filters to be divided into slow (0.1-0.3 m/h), fast (512 m/h) and ultra-high-speed (36-100 m/h).
All types of conditioning most often concern the normalization of the mineral composition of water. They are divided into two groups: 1) removal of excess salts and gases from water - softening, desalting and desalination, deferrization, defluoridation, removal of manganese, silicic acid, degassing, etc.; 2) adding special salts to water in order to improve the organoleptic properties of water or increase the content of microelements in it (fluorine, etc.). More common methods for improving drinking water quality include the following. The ion exchange method, which is based on passing water through ion exchange filters (anion exchangers and cation exchangers), installations made of special insoluble granular materials (ion exchange resins), which have the property of exchanging the ions included in their composition for ions contained in the filtered water. Water softening is the complete or partial removal of calcium and magnesium cations from water. The latter is achieved both by the reagent method of ionic
exchange and thermal. Water fluoridation is used in certain zones (biogeochemical provinces) of our country, where a lack of the microelement fluorine is noted. This method was proposed to reduce the incidence of dental caries. If the fluorine content is high, water is defluoridated using aluminum or magnesium hydroxide or tricalcium phosphate, which precipitate fluorine.
At the slightest suspicion of water contamination, it must be thoroughly checked and, if necessary, disinfected. All types of water disinfection are divided into two groups: reagent and non-reagent.
Reagent methods for water disinfection. Of these methods, chlorination of drinking water is considered the most common. It is carried out using chlorine gas, hypochlorites and bleach. The bactericidal effect of these substances belongs to hypochlorous acid (HOC1 and its hypochlorite ion (OCH), which in an aqueous environment can form HOC1. The acid penetrates the bacterial cell membrane and disrupts the function of enzymes that catalyze redox processes that provide this cell with energy. Process the formation of bactericidal chlorine compounds when used in different types can be seen from the following reactions: when chlorine is dissolved in water, the reaction C12 + H20 = HOC1 + H* + + SG occurs, hydrolysis of chlorine gives 99.9% HOC1 at 0°C and 99 .97% at 25°C.
In industrial conditions, bleach with an active chlorine content of 35 to 39% is often used to chlorinate water. Since the activity of bleach may decrease during storage, it is necessary to determine the presence of active chlorine in it before use. 
At water supply stations, chlorination is carried out in a gaseous manner using special devices - chlorinators (Fig. 7).
When water is chlorinated, the effectiveness of disinfection is systematically monitored. To do this, the residual chlorine in chlorinated water is determined hourly during the day and the titer of E. coli is determined daily. The latter in chlorinated water should be at least 300 ml. The dose of chlorine depends on the state of contamination of the water. It is considered sufficient if the water after chlorination contains no more than 0.4 mg/l, but not less than 0.2 mg/l.
In the process of water disinfection, it should be borne in mind that the effect of chlorine is achieved only if the dose of chlorine absorption or chlorine requirement of water is determined quite accurately in the laboratory. In case of dangerous contamination of water, it is treated with large doses of chlorine (superchlorination), and excess
the dose of chlorine is eliminated by dechlorination. The latter is most often carried out after appropriate calculations with 0.5% solutions of sodium sulfate (hyposulfite) or sodium sulfate.
In addition to chlorination, reagent methods for water disinfection include:
They also disinfect it with ozone, iodine and silver ions.
Reagent-free methods of water disinfection include ultraviolet irradiation, ultrasound treatment, gamma radiation, etc. F-region teaching ensures reliable water disinfection, which is achieved by the biologically active part of the ultraviolet spectrum. Many studies have found that rays with a wavelength of 295-200 millimicrons have the most active effect on bacteria.
To disinfect water using UV rays, high-pressure mercury-quartz lamps of the PRK type (direct mercury-quartz), BUV-60 are used.
Ultrasonic water disinfection is based on the bactericidal effect of this physical factor through the mechanical destruction of bacteria in an ultrasonic field. As for the disinfecting effect of gamma radiation, as reported by S.N. Cherkinsky (1974), with an appropriate dose rate, microorganisms die very quickly. However, this method requires special conditions
Reagent-free methods for decontaminating water include boiling. This is a simple and very reliable method that allows you to neutralize a small amount of water. 
b 7
Pollution entering a body of water causes a disturbance in its natural balance. The ability of a reservoir to resist this disturbance, to free itself from introduced contaminants, is the essence of the self-purification process.
Self-purification of water systems is due to many natural and sometimes man-made factors. These factors include various hydrological, hydrochemical and hydrobiological processes. Conventionally, three types of self-purification can be distinguished: physical, chemical, biological.
Among physical processes, dilution (mixing) is of paramount importance. Good mixing and a decrease in the concentration of suspended particles is ensured by the intense flow of rivers. The self-purification of reservoirs is facilitated by the settling of polluted waters and the settling of insoluble sediments to the bottom, the sorption of pollutants by suspended particles and bottom sediments. For volatile substances, evaporation is an important process.
Among the chemical factors in the self-purification of reservoirs, the main role is played by the oxidation of organic and inorganic substances. Oxidation occurs in water with the participation of oxygen dissolved in it, so the higher its content, the faster and better the process of mineralization of organic residues and self-purification of the reservoir. When a reservoir is heavily polluted, the reserves of dissolved oxygen are quickly consumed, and its accumulation due to physical processes of gas exchange with the atmosphere proceeds slowly, causing self-purification to slow down. Self-purification of water can also occur as a result of some other reactions in which poorly soluble, volatile or non-toxic substances are formed, for example, hydrolysis of pesticides, neutralization reactions, etc. Calcium and magnesium carbonates and bicarbonates contained in natural water neutralize acids, and carbonic acid dissolved in water neutralizes alkalis.
Under the influence of ultraviolet radiation from the sun, photodecomposition of certain chemicals, such as DDT, occurs in the surface layers of the reservoir, and water is disinfected - the death of pathogenic bacteria. The bactericidal effect of ultraviolet rays is explained by their influence on the protoplasm and enzymes of microbial cells, which causes their death. Ultraviolet rays have a detrimental effect on vegetative forms of bacteria, fungal spores, protozoan cysts, and viruses.
Each body of water is a complex living system inhabited by bacteria, algae, higher aquatic plants, and various invertebrate animals. The processes of metabolism, bioconcentration, and biodegradation lead to changes in the concentration of pollutants. Biological factors of self-purification of a reservoir also include algae, mold and yeast, but in some cases the massive development of blue-green algae in artificial reservoirs can be considered a process of self-pollution. Representatives of the animal world can also contribute to the self-purification of water bodies from bacteria and viruses. Thus, oysters and some amoebas adsorb intestinal and other viruses. Each mollusk filters more than 30 liters of water per day. Common reed, angustifolia cattail, lake reed and other macrophytes are capable of absorbing from water not only relatively inert compounds, but also physiologically active substances such as phenols and toxic salts of heavy metals.
The process of biological water purification is related to the oxygen content in it. With a sufficient amount of oxygen, the activity of aerobic microorganisms that feed on organic substances manifests itself. When organic substances are broken down, carbon dioxide and water are formed, as well as nitrates, sulfates, and phosphates. Biological self-purification is the main link of the process and is considered as one of the manifestations of the biotic cycle in a reservoir.
The contribution of individual processes to the ability of the natural aquatic environment to self-purify depends on the nature of the pollutant. For so-called conservative substances that do not decompose or decompose very slowly (metal ions, mineral salts, persistent organochlorine pesticides, radionuclides, etc.), self-purification is of an apparent nature, since only the redistribution and dispersion of the pollutant in the environment occurs, pollution adjacent objects. A decrease in their concentration in water occurs due to dilution, removal, sorption, and bioaccumulation. With regard to nutrients, biochemical processes are the most important. For water-soluble substances that are not involved in the biological cycle, the reactions of their chemical and microbiological transformation are important.
For most organic compounds and some inorganic substances, microbiological transformation is considered one of the main ways of self-purification of the natural aquatic environment. Microbiological biochemical processes include several types of reactions. These are reactions involving redox and hydrolytic enzymes (oxidases, oxygenases, dehydrogenases, hydrolases, etc.). Biochemical self-purification of water bodies depends on many factors, among which the most important are temperature, active reaction of the environment (pH) and the content of nitrogen and phosphorus. The optimal temperature for biodegradation processes to occur is 25-30ºС. Of great importance for the life of microorganisms is the reaction of the environment, which affects the course of enzymatic processes in the cell, as well as changes in the degree of penetration of nutrients into the cell. For most bacteria, a neutral or slightly alkaline reaction environment is favorable. At pH<6 развитие и жизнедеятельность микробов чаще всего снижается, при рН <4 в некоторых случаях их жизнедеятельность прекращается. То же самое наблюдается при повышении щелочности среды до рН>9,5.
Self-purification of water in reservoirs is a set of interconnected hydrodynamic, physicochemical, microbiological and hydrobiological processes leading to the restoration of the original (background) state of the water body. The decisive role in self-purification belongs to biological and physicochemical processes; the latter predominate in the presence of toxic substances in water that inhibit biological processes. The self-purifying ability of a river also depends on the speed of the river flow, the chemical composition of the water, its temperature, the mass of suspended substances, bottom sediment, silt, etc. One of the main factors of self-purification (reducing the concentration of pollutants) is dilution, although at the same time there is a decrease in the intensity of the process self-cleaning.[...]
Self-purification of water occurs not only in agricultural irrigation fields and filtration fields, but also in the riverbed itself. Biochemical and physical-chemical processes take place here, thanks to which the chemical and biological qualities of water are restored. Waste liquid and sewage entering water bodies are diluted with water. Some microbes settle to the bottom and are destroyed there. Pathogenic bacteria die under the influence of light, unfavorable temperature for them, and the bactericidal effect of oxygen dissolved in water. A huge number of bacteria are consumed by single-celled protozoa, crustaceans and other zooplankton organisms.[...]
Self-purification of water from open reservoirs from bacterial contaminants occurs due to a complex set of physical, chemical and biological factors, which is facilitated by the dilution of contaminants with a large mass of water, mixing, sedimentation of suspended matter, the influence of sunlight, aeration, etc. Under the influence of biochemical processes occurring in water , especially oxidative ones, pathogenic microbes die. Bacteria are also destroyed by protozoa, which ingest them. food. Bacteriophages, antagonist microbes and antibiotics of biological origin also have a destructive effect on bacteria.
Self-purification of polluted natural waters occurs when they are diluted multiple times (1:7...1:12) with clean water. These processes in closed reservoirs and groundwater occur slowly. Complete self-purification of the water of the World Ocean will occur only after 2600 years, and underground water - after 5000 years.[...]
Self-purification of water from oil is a multi-stage process, sometimes extending over a long time.[...]
The composition of water from natural surface sources is not constant. The processes of oxidation, reduction, deposition of large and heavy particles, as well as biochemical processes leading to self-purification of water, continuously occur in them. The composition of surface waters on land varies greatly with the seasons of the year, and also occasionally as a result of atmospheric precipitation. The mineralization of groundwater, especially deep-lying ones, is subject to significantly less fluctuations.[...]
The composition of water from natural sources is not constant. The processes of oxidation, reduction, precipitation of large and heavy particles, as well as a number of biological processes leading to self-purification of water, continuously occur in it. [...]
The process of self-purification of water is carried out in these cases due to the vital activity of various groups of soil organisms - bacteria, fungi, algae, protozoa, worms and arthropods; a biological film forms on the surface of soil lumps.[...]
The process of self-purification of reservoir water from pollutants Prof. S. N. Stroganov divides it into two stages: 1) mixing of the contaminated stream with the entire mass of water, i.e. a purely physical phenomenon; 2) self-purification in the proper sense of the word, i.e. the processes of mineralization of organic substances and the death of bacteria introduced into the reservoir.[...]
The quality of water from underground water sources when used for household and drinking purposes without purification and disinfection must comply with the standards of GOST 2874-73 “Drinking Water”; sanitary and microbiological analysis is carried out using the methods set out in GOST 18963-73. To assess the process of microbial self-purification in groundwater, the entire group of E. coli is determined, including lactose-negative and additionally enterococci, which survive for a long time in groundwater at low temperatures. The absence of E. coli phages can in this case be a reliable indicator of self-purification of water from enteroviruses (E.I. Molozhavaya et al., 1976).[...]
If wastewater is discharged into a reservoir or into soil inhabited by living organisms, then the mentioned processes occur naturally. Living organisms that seek nutrition in polluted wastewater are found everywhere. With an increase in the amount of nutrients, their number increases rapidly, and when food reserves are used up, they die off. Since the discharge of wastewater into water bodies does not occur once, but, as a rule, is of a regular nature, we can assume that the microorganisms found in our water bodies are always provided with the necessary nutrients. Once wastewater contaminants have been decomposed and broken down by a variety of physical, chemical and biological processes, they are gradually carried downstream from the wastewater discharge site. We call this process self-purification of the reservoir. In other words, self-purification of water in a river or lake represents the return of water to its natural, original state, which was disrupted as a result of the discharge of wastewater into it.[...]
The intensity of self-purification of water from oil products entering it largely depends on temperature: at 20-25°C, 50-80% of the total amount of oil entering the water is oxidized in 20 days, while at 5°C only 10-20% of the contained in water, oil and its decomposition products are sorbed by bottom sediments, and clayey silts have the greatest sorption capacity.[...]
The main mechanism for self-purification of water from certain groups of organic substances, when biochemical effects are most pronounced, is the degradation of oil. Fractionation and the cumulative effect of various factors after oil enters water are well known; Evaporation plays an important role in the destruction of oil spills. Hydrocarbons with long chains of carbon atoms up to C15 (boiling point up to 250 ° C) evaporate from the water surface within 10 days, hydrocarbons C15-C25 (250-400 ° C) are retained much longer, and heavy fractions above C25 practically do not evaporate. In general, evaporation alone can remove up to 50% of crude oil hydrocarbons, up to 10% of heavy oil and up to 75% of light fuel oil.[...]
At the beginning of the process of self-purification of water in ponds, a symbiosis of bacteria and algae is observed, which by the end of the process is replaced by antagonism. The death of bacteria and, in particular, pathogenic intestinal bacteria occurs as a result of the release of bactericidal substances by algae. Therefore, in the process of post-treatment of wastewater in biological ponds, not only the removal of biogenic and organic substances, but also bacterial contaminants takes place. As already indicated, strictly aerobic biological ponds should be used for post-treatment purposes. Mandatory conditions for the normal operation of such ponds are compliance with the optimal environmental reaction (pH) and temperature for aquatic organisms, as well as the presence of dissolved oxygen of at least 1 mg/l. Water mixing is important, which prevents the formation of anaerobic zones and contributes to the processes of stabilizing water quality.[...]
The contribution of animals - inhabitants of reservoirs - to the self-purification of waters is very great. By processing organic matter created by plants in food connections, consumer animals decompose part of this substance to the initial simple compounds - water and carbon dioxide, the rest in the form of excrement passes into the form most effectively used by decomposer microorganisms. Part of the organic matter is deposited in bottom silts.[...]
Influence on the processes of self-purification of reservoirs. A tungsten concentration of 1 mg/l in an experimental reservoir inhibits the military-industrial complex, the processes of ammonification and nitrification of organic compounds, and the growth of microflora. A tungsten concentration of 0.1 mg/l inhibits water self-purification processes by 10-20%, and 0.01 mg/l has no effect on them.[...]
The entry of pollutants into river water disrupts the physical and chemical balance in the river flow. To restore it in the pollutant dispersion halos, self-purification of water occurs. Self-purification is a system of mechanical, chemical and biological processes that reduce the amount of pollutants and change the form in which they are found. Self-purification is carried out by dilution with precipitation or influent water.[...]
The main factor in the processes of self-purification of water is its oxygen saturation. Under the influence of dissolved oxygen, organic substances oxidize and fall to the bottom of reservoirs in the form of mineral sediment.[...]
The conditions for the discharge of return (waste) water into water bodies are determined taking into account the degree of mixing of return (waste) water with the water of the water body at a distance from the place of release of return (waste) water to the nearest control point for water use, as well as the background composition of water bodies at the places of waste discharge water The natural self-purification of waters from substances entering them is taken into account if this process is sufficiently pronounced and its patterns have been studied.[...]
Under natural conditions, the complex of physical processes of self-purification of water from oil consists of a number of components: evaporation; settling of lumps, especially those overloaded with sediment and dust; sticking together of lumps suspended in the water column; floating of lumps forming a film with inclusions of water and air; reducing the concentrations of suspended and dissolved oil due to settling, floating and mixing with clean water. The intensity of these processes depends on the properties of a particular type of oil (density, viscosity, coefficient of thermal expansion), the presence of colloids, suspended and transportable plankton particles, etc., air temperature and solar illumination in the water.[...]
It is known that when releasing biologically treated wastewater into a reservoir, it is desirable to have the highest possible concentration of dissolved oxygen in these waters. This allows you to speed up the processes of self-purification of the reservoir water and improve its oxygen regime.[...]
The symbiosis of bacteria and algae takes place at the initial stages of self-purification of water in ponds. By the end of the purification process, symbiosis gives way to antagonism.[...]
It should be emphasized that organic substances in household wastewater are accompanied by abundant saprophytic and very often pathogenic microflora, therefore the concentration of organic substances in water is an indirect indicator of the massiveness of bacterial contamination of water bodies. At the same time, the completion of the process of mineralization of organic substances in household wastewater, and therefore the weakening or elimination of the danger of pollution of a reservoir in epidemiological terms, can be judged to a certain extent by the degree of bacterial self-purification of water. This determines the sanitary significance of pollution of water bodies with organic substances from household wastewater and its limitations in terms of biochemical oxygen consumption (BOD).[...]
The first criterion evaluates the influence of harmful substances on the processes of self-purification of water from organic contaminants in wastewater, for which the amount of oxygen required for the oxidation of organic substances and the development of aquatic microflora is determined. The characteristics of water pollution in this case are biological and chemical oxygen consumption (BOD and COD - see section 6.4.2).[...]
In accordance with regulatory requirements for BOD, when discharging wastewater into reservoirs, the total biochemical demand for oxygen at 20°C should not exceed 3 mg/l in a reservoir of category I and 6 mg/l in a reservoir of category II. When calculating the permissible BOD value of treated wastewater discharged into a reservoir, along with the possible degree of its dilution in the water of the reservoir, the rate of biochemical processes and self-purification of water in the reservoir in the area from the place of wastewater discharge to the nearest point of water use is also taken into account. In addition, it is known that the water of some reservoirs in its natural state has a BOD value that exceeds the standards due to the content of humic substances in it, as well as due to the “blooming” of the reservoir. In these cases, which have nothing to do with pollution of the reservoir by wastewater, the calculation of organic pollutants discharged into the reservoir is carried out specially. [...]
The study of the influence of chemicals on the organoleptic properties of water (color, pricing, smell, taste) is of greater practical importance, since a change in the properties of water familiar to people is easily detected and is a kind of danger indicator, which leads to a sharp decrease in the use of a water source. An experimental study of the influence of chemicals on the general sanitary regime of reservoirs is carried out in order to prevent disruption of the processes of self-purification of reservoir water. Simultaneous study of the stability and transformation of a substance in water is aimed at determining the duration of its content in the aquatic environment and hygienic assessment of possible products of its transformation in comparison with the starting substance in accordance with the “Methodological guidelines for the experimental study of transformation processes of chemical substances during their hygienic regulation in water” ( No. 2968-84).[...]
The usual chemical and technological characterization of substances by solubility in water should not be mechanically transferred to the field of hygienic research, where, as a rule, one often encounters very low concentrations of these substances in water bodies. The methodology for studying the stability of harmful substances in industrial wastewater is subject to the demands of sanitary practice, from the point of view of which the slowly occurring process of self-purification of water loses its significance.[...]
As many authors have noted, all hydrobionts are, to some extent, water purifiers, hence the tendency to place too high hopes on the processes of self-purification of water in natural reservoirs. But all hydrobionts, especially plants and so-called microorganisms, are at the same time water pollutants. After the death of filamentous, green and blue-green algae, the released decomposition products can deteriorate the quality of water so much that it becomes unsuitable for drinking purposes. Many authors proposed preventing the possibility of “blooming” of water by treating it with salts of heavy metals or pesticides (Guseva, 1952; Drachev, 1956, 1964).[...]
In the South Kazakhstan region, characterized by an arid climate, the problem of rational water consumption is extremely relevant. In this regard, issues related to both the study of sources of pollution of water resources and the development of methods for their purification are of particular importance. It is known that in the natural self-purification of water, a huge role belongs to the biocenosis of aquatic organisms - bacteria, algae, protozoa, invertebrates, which in the formed ecological pyramids, depending on the producer-consumer nature, contribute to the process of reducing the concentration of toxic ingredients. However, during mass reproduction, aquatic organisms can form fouling in the pipes of water supply systems of enterprises, as a result of which the pipes become clogged and problems are created with the quality and timely provision of technological processes. In this regard, studying the composition of the biocenosis of phytofouling and developing measures to combat them is an urgent problem.[...]
Considering that in solving equations (26) and (27) it is difficult only to calculate the values of 10-1, which reflect the process of self-purification of water from organic substances, we have compiled auxiliary table 22.[...]
Since biochemical oxidation of organic substances occurs in a reservoir, accompanied by their mineralization, the calculation of the permissible discharge of wastewater must take into account not only possible dilution, but also the degree of self-purification of the reservoir water from organic pollution on the way to the nearest point of water use. As for the real significance of the process self-purification, then this will depend on the speed of the biochemical process /Ci and the time t - the movement of water from the wastewater discharge area to the nearest point of water use.[...]
According to calculations by the State Oceanographic Institute, up to 950 tons of detergents and 80 tons of mercury enter the Baltic Sea annually. Since the intensity of self-purification processes in the Baltic Sea waters is quite low, which is associated with low water temperatures, the problem of stabilizing the level of pollution and their elimination is becoming increasingly important every year.[...]
Lake Baikal basin. Baikal is a unique freshwater lake, ranking first in the world in terms of depth and volume of water masses. It contains about 20% of the world's water and over 80% of the country's fresh water. The Baikal ecosystem is distinguished by its amazing richness and originality - at least 2,400 species and varieties of animals and plants live in the lake. Its unique feature is the presence of a subtle biological mechanism for self-purification of water.[...]
The hygienic significance of the development of microflora under the influence of surfactants may vary depending on specific conditions. Obviously, the development of saprophytic bacteria in a reservoir changes the conditions for self-purification of water from organic pollution, in particular household wastewater, and also changes the sanitary indicative value of these microorganisms. The proliferation of the same bacteria in drinking water can negatively affect the quality of the water. The proliferation of pathogenic microflora in any case is a negative factor from an epidemiological point of view.[...]
The scheme also includes studies, the results of which are not directly taken into account when determining hygienic standards, but have scientific and practical significance. Thus, the study of the stability of substances in water makes it possible to identify both substances with pronounced stability and substances that change the composition and properties of water in reservoirs. Based on the data of such a study, it is possible to predict the degree of self-purification of water from harmful substances of industrial wastewater, and this is essential when determining the conditions for the discharge of wastewater into a reservoir. Studying the protective ability of modern methods of purification and disinfection of drinking water makes it possible to identify substances that are not retained or neutralized in water supply facilities. In these cases, studies on hygienic standards should be carried out with extreme caution.[...]
Biological ponds come with artificial or natural aeration. Recently, a method for calculating artificial channel-type flowing ponds has been developed (Fig. 50). They are usually built on land unsuitable for agriculture. In artificial biological ponds, it is envisaged to create optimal regimes in the processes of self-purification of water: artificial saturation with oxygen, artificial mixing, water exchange between surface and bottom layers of water, planting vegetation on the slopes of canals and along the banks of enclosing dams, arrangement of a biologically active bottom, optimal temperature, constant water flow etc.[ ...]
The presence of benthic organisms in open water sources is very significant for the characteristics of these sources. Depending on environmental factors, these microorganisms are divided into marine, freshwater, microorganisms of salt lakes, swamps, streams, rivers, waterfalls, hot springs and mineral springs. In freshwater sources, benthic microorganisms take part in water purification: they mineralize organic substances, and oxidize reduced substances of inorganic origin; The dominant role in these processes belongs to microbes. The richest layer of bacteria is the surface layer of sludge, which has a very significant impact on the development and vital activity of microorganisms in reservoirs and watercourses. Filamentous sulfur and iron bacteria play a significant role in the self-purification of water. The former oxidize hydrogen sulfide into sulfuric acid salts, which protects the fish from death; the second - iron (II) to iron (III). At the bottom of reservoirs, fermentation processes also occur with the formation of methane and carbon dioxide. 1 g of sludge contains from 100 thousand to 1 million bacteria that reduce sulfates; from 10 to 100 thousand thionic, about 1000 nitrifying, from 10 to 100 thousand. denitrifying bacteria; about 100 anaerobic and the same number of aerobic fiber destroyers. The sludge also contains bacteria that oxidize methane and hydrogen, fermentation agents, an anaerobic fixator of atmospheric nitrogen, etc. [...]
One of the significant consequences of changes in the hydrological regime of rivers in connection with the creation of reservoirs, the elimination of floods and a decrease in current speeds is a slowdown in water exchange in river systems. A slowdown in water exchange leads to changes in hydrophysical, hydrochemical and hydrobiological processes, which, together with the regime for regulating water reserves in reservoirs, causes a change in the processes of self-purification of water compared to river water, and determines the thermal regime of the upper and lower pools. Water exchange largely determines the main hydrological features of reservoirs and is an integral indicator of the intensity of the relationship of river waters with established and emerging ecosystems.[...]
The roles of bacteria in nature are very diverse, which is associated with different energy sources used by different groups of bacteria. Many heterotrophic aerobic bacteria are decomposers in ecosystems. In the soil, they participate in the formation of a fertile layer, transforming forest litter and rotting animal remains into humus. Soil bacteria also break down organic compounds into minerals. It has been established that up to 90% of CO2 enters the atmosphere due to the activity of bacteria and fungi. Bacteria participate in the biogeochemical cycles of nitrogen, sulfur, and phosphorus. Self-purification of water in natural reservoirs, as well as wastewater treatment, is carried out by aerobic and anaerobic heterotrophic bacteria. [...]
Analysis of the quantitative relationships between viruses, E. coli phages and coliforms identified under natural conditions also indicates that the phage is more indicative of viral contamination of both heavily and moderately polluted river water. The same data made it possible to substantiate the quantitative criteria for the phage of Escherichia coli, guaranteeing epidemic safety in relation to viral contamination of water from domestic drinking water sources - no more than 1000 PFU per 1 liter (T. 3. Artemova et al., 1977). The same value indicates the completion of the processes of self-purification of source water from viruses when establishing sanitary protection zones for water pipelines (G. A. Bagdasaryan, L. A. Myshlyaeva, 1976).[...]
Discharges of the pollutants in question in the selected areas and in large cities were determined according to 2TP (vodkhoz) reporting data for 1989 and distributed among the above-mentioned areas. Discharges of pollutants in the cities of Orel, Kaluga, Aleksin, Serpukhov, Stupino, Kashira, Kolomna, Ryazan, Kasimov, Vyksa, Murom, Pavlovo, Bogorodsk, Dzerzhinsk, located directly on the trunk of the river. Oki, were taken according to the corresponding reporting table 2TP (vodkhoz) and were subtracted from the discharge of pollutants into the trunk of the river. Oki in the appropriate areas. Discharges of pollutants into small rivers, not presented in the GHI report, were accepted as discharges entering directly into the river trunk. Okie. This slightly overestimated their influence on the concentration of pollutants in the river. Oka, since the self-purification of water in the beds of these small rivers was not taken into account. The resulting overestimation of the concentrations of pollutants obtained during modeling can be attributed to the “reliability margin” of wastewater treatment measures.
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