Water pollution. All pollutants, including anthropogenic, technogenic origin, entering natural waters cause various qualitative changes in them, the main of which are as follows:
change in physical properties (violation of transparency and color, the appearance of unpleasant odors and tastes, etc.);
changes in the chemical composition, in particular, the appearance of harmful substances in the water;
the appearance of floating substances on the surface of the water and sediments on the bottom;
reduction in the amount of dissolved oxygen due to its consumption for the oxidation of organic substances entering the reservoir;
the appearance of bacteria and other microorganisms, including pathogens.
Pollution of natural waters leads to the fact that they are unsuitable for drinking, bathing, and sometimes for technical needs. It has a particularly harmful effect on fish, waterfowl, animals and other organisms that live in the water.
Oil and its derivatives have a harmful effect on waters. They not only form films on the surface of rivers and water bodies, but also deposits on the bottom. Even an insignificant oil content (0.2-0.4 mg / l) is accompanied by the appearance of a specific odor, which does not disappear after chlorination and water filtration. The presence of oil products in the water has a particularly negative effect on fish, causing their massive illness and death. When the content of oil in water is more than 0.1 mg / l, fish meat acquires a taste and a specific smell that cannot be eliminated during technological processing.
Phenolic compounds contained in the wastewater of various enterprises pose a great danger. Possessing strong antiseptic properties, phenolic waters disrupt biological processes in the water, giving it a pungent, unpleasant odor and worsening the conditions for the reproduction of aquatic fauna.
In recent years, water pollution has been noted with synthetic surfactants (surfactants), which are contained in the wastewater of some industries. Surfactants give water tastes and odors, form persistent foam accumulations and worsen its biochemical properties. Already at low concentrations of synthetic surfactants in water, the growth of algae and other vegetation stops.
The descent into natural sources of warm waters from various power plants leads to intensification of evaporation and is accompanied by an increase in mineralization. At the same time, there is an accumulation of organic matter with its subsequent decomposition. The consequence of these processes is a decrease in the content of dissolved oxygen in the water, which negatively affects the flora and fauna.
Significant damage to watercourses is caused by molten timber rafting and dumping of wood waste in the form of sawdust and bark. In addition to direct damage to fish and their spawning grounds by logs, twigs and branches, resin and other harmful substances are released into the water. These products slowly decompose in water, absorbing oxygen and killing fish and their eggs.
The greatest danger to natural waters, human health, animals and fish is posed by various radioactive waste. The processes of biological concentration of radioactive substances take place in the organisms of plants, fish and animals. Small organisms containing these substances in small doses are absorbed by larger ones, in which already dangerous concentrations arise. Therefore, at present, all wastewater with increased radioactivity is discharged into special underground reservoirs or pumped into deep drainless basins. There are other more advanced methods of radioactive waste disposal that prevent the pollution of natural waters.
Self-purification of waters. Open water bodies are almost continuously exposed to a variety of pollution. However, in large reservoirs, a sharp deterioration in water quality is not observed. This is due to the fact that the water of rivers, lakes, etc. has the ability to self-purify from suspended particles, organic matter, microorganisms and other contaminants. The process of self-purification of open water bodies proceeds under the influence of various factors, which act simultaneously in various combinations.
These factors include: hydrological - dilution and mixing of contaminants with the bulk of 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 constituent parts of incoming wastewater; chemical - the transformation of organic matter into mineral (i.e. mineralization).
When wastewater enters the reservoir, the effluent mixes with the reservoir water and the concentration of pollutants decreases. In addition, suspended mineral and organic particles, helminth eggs and microorganisms are partially deposited, the water becomes clarified and transparent.
In the process of self-cleaning, saprophytes and pathogenic microorganisms die off. They die as a result of nutrient depletion of water; bactericidal action of ultraviolet rays of the sun, which penetrate into the water column by more than 1 m; the influence of bacteriophages and antibiotic substances secreted by saprophytes; unfavorable temperature conditions; antagonistic effects of aquatic organisms and other factors. The processes of self-purification of water proceed more intensively in the warm season and in flowing water bodies - rivers.
The so-called saprophytic microflora and aquatic organisms play an essential role in the processes of water self-purification. Some representatives of the microflora of reservoirs 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 trapped in a reservoir also affect disease-causing organisms.
One of the important processes of self-purification of water is the mineralization of organic substances, i.e. the formation of mineral substances from organic ones under the influence of biological, chemical and other factors. With mineralization in water, the amount of organic matter decreases, along with this, organic matter of microbes can also be oxidized, and therefore, some of the bacteria die.
The first mineral product of oxidation of nitrogen-containing organic substances is ammonium ion or ammonia. Ammonia, as a rule, in the presence of oxidants transforms into nitrites, but these acidic compounds are very unstable and, in the presence of oxygen, are oxidized to nitrates, which are the final substance during the mineralization of organic nitrogen-containing products.
Oxidation of fats, fiber, carbohydrates mainly occurs in water with intense formation of carbon dioxide.
The evidence of the organic origin of nitrogen-containing minerals is the high oxidizability of water, the almost complete absence of dissolved oxygen, the presence of chlorides, sulfates, phosphates, etc.
Good aeration of water (oxygen enrichment) activates oxidative, biological and other processes, contributing to water purification.
The rate of self-purification of water depends on the following basic conditions: the amount of contaminants entering the reservoir; the depth of the reservoir and the speed of water flow; water temperature; the amount of oxygen dissolved in water; composition of microfauna and flora of water, etc. However, it must be remembered that the ability of water bodies to self-purify is limited.
Compounds of lead, copper, zinc, mercury, which can get into water bodies with sewage, have a toxic effect on the body of animals, and also slow down the processes of self-purification of water and worsen its organoleptic properties.
In small reservoirs with a significant amount of proteinaceous pollutants, intermediate substances of their decomposition (hydrogen sulfide, nitrites, diamines, etc.), which are highly toxic, can accumulate in the water.
Self-purification of groundwater occurs due to filtration through the soil and due to mineralization processes.
Open water bodies are almost continuously exposed to a variety of pollution. However, in large reservoirs, a sharp deterioration in water quality is not observed. This is due to the fact that rivers, lakes, reservoirs, under the influence of a variety of physicochemical and biological processes, have the ability to self-purify from suspended particles, organic matter, microorganisms and other contaminants.
The process of self-purification of open water bodies proceeds under the influence of various factors, which act simultaneously in various combinations.
These factors include: hydrological - dilution and mixing of contaminants with the bulk of 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 constituent parts of incoming wastewater; chemical - the transformation of organic matter into mineral (mineralization).
In the process of self-cleaning, saprophytes and pathogenic microorganisms die off. They die as a result of the depletion of water in nutrients, the bactericidal action of the ultraviolet rays of the sun, which penetrate into the water column for more than
- m, the influence of bacteriophages and antibiotic substances secreted by saprophytes, unfavorable temperature conditions, antagonistic effects of aquatic organisms and other factors. The processes of self-purification of water proceed more intensively in the warm season, as well as in flowing water bodies - rivers. Low-flow reservoirs (ponds, lakes, reservoirs) are much less self-cleaning, since the water flow is slowed down in them, and suspended particles settle to the bottom, as a result of which the reservoir becomes silted and the water quality deteriorates.
With severe pollution of water bodies with domestic industrial wastewater, self-purification processes usually slow down and even completely stop. Industrial wastewater introduces significant amounts of various chemicals into the reservoir, which impair the organoleptic properties of water and give it an unpleasant taste, smell (chlorobenzene, dichloroethane, styrene, oil, etc.), and also affect the biological and chemical processes of self-purification of water (acetone, methanol, ethylene glycol, etc.).
The so-called saprophytic microflora and aquatic organisms are essential in the processes of self-purification of water. Some representatives of the microflora of reservoirs have antagonistic properties to pathogenic microorganisms, which leads to the death of these microbes.
Protozoa are characterized by the greatest antimicrobial action. Eaters of microbes - bacteriophages trapped in a reservoir also affect pathogenic, pathogenic microorganisms.
Under the influence of natural factors, open water bodies (rivers, lakes and reservoirs), like the soil, have the ability to get rid of contaminants that have got into them. In rivers, for self-cleaning, water must run at least 15 km from the place of pollution, provided that there are no new contaminants in the path of the water flow. The speed of self-cleaning depends on the abundance of water, the speed of the flow of water and wind, contributing to the mixing of water in the reservoir. In lakes and reservoirs, water is purified the more intensively, the larger the sources themselves. In shallow water bodies, self-purification processes are extremely weak.
Self-purification of water occurs as a result of mechanical, physicochemical and biological processes. In this case, the incoming pollution is diluted with the water of the reservoir, the substances suspended in the water gradually settle to the bottom, and the organic substances undergo oxidation due to the oxygen dissolved in the water. In this case, aerobic processes occur mainly in the upper layers of the reservoir, and anaerobic - at the bottom.
Fig. 6
a reservoir where air oxygen does not enter. As a result of these processes, organic substances, decomposing into less complex ones, are gradually mineralized.
The process of mineralization of organic substances in water and the end products of the degradation of the protein substrate are shown in Fig. 6.
The processes of self-purification of water are also facilitated by protozoa feeding on bacteria, rotifers, crustaceans, molluscs and some plant organisms that feed on organic matter. From a sanitary point of view, self-purification of water is a very useful phenomenon in nature. However, this process in open water bodies is not unlimited - with strong and constant pollution, self-purification of water becomes insufficient. This is often observed with the uncontrolled release of household, 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 a massive pestilence of fish.
In practical work, it becomes necessary to determine the age of pollution of water sources with organic waste. To do this, you can use the following scale:
If only organic ammonia is found in the water, then 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 col-titer, its increased oxidizability and general hardness.
When found in water, in addition to ammonia, chlorides indicates that the pollution of the reservoir has occurred relatively recently, because chlorides usually appear during the destruction of protein substances after ammonia.
The presence of ammonia, chlorides, and nitrous acid (nitrites) in the same water sample suggests 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 considerable period of time has passed since the moment of pollution, but fresh pollution has taken place.
The presence of chlorides, nitric and nitrous acids in the water indicates that there is no fresh pollution, but the process of mineralization of organic substances continues.
If a long time has passed since the moment of water pollution with organic substances, then only nitrous and nitric acids can be found in it. The presence of only nitric acid salts in the water indicates that the mineralization process has ended completely and the water can be used for drinking animals.
4.8.
WATER PURIFICATION AND DISINFECTION METHODS
Water used in agricultural enterprises and farms may not meet some of the requirements of SanPiN
- 1074-901, approved by the Chief State Sanitary Doctor of the Russian Federation
- , 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 and 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, purifying it from various impurities, sedimentation, coagulation and filtration are used.
Settling - special closed underground tanks (usually reinforced concrete pools) are filled with water for 4-8 hours. During this time, coarse suspended particles and part of microorganisms (up to 60-70%) settle to the bottom of the tank, and the water becomes transparent.
In the conditions of agricultural production, water can be defended in open reservoirs, reservoirs, dams, if they are well protected from pollution.
Coagulation of water and sedimentation of suspensions is a reagent method for improving water quality using special substances - coagulants. The most commonly used crude aluminum sulfate L12 (804 18H20), containing 33% anhydrous aluminum sulfate, up to 23% of insoluble impurities. At present, purified alumina is produced containing no more than 1% of insoluble impurities. For coagulation, iron sulfate (Fe804-7I20) is also used, which forms iron hydroxide in water, ferric chloride (FeC12), which is highly soluble in water and forms large rapidly settling flakes of iron hydroxide, sodium aluminate (Cal102). Higher precipitation results are obtained with the simultaneous use of ferric chloride in a mixture with aluminum sulphate and lime. Water treatment processes using reagents are more intensive and are accompanied by higher efficiency. If the sedimentation of a mass of suspended solids by the reagent method requires 2-4 hours, then the reagent-free 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. Add it in the form of a powder or in the form of a 2-5% aqueous solution.
Given 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, transparent, colorless water is obtained, the number of microorganisms in it decreases by 60-95%, and Escherichia coli by 9099%.
By the nature (type) of the filtering base, filters are subdivided into mesh (microfilters, microfilters), frame or alluvial and the most common granular (sand, anthracite). The size of the particles of the filtering material, as well as the thickness of the layer, allow granular filters to be subdivided into slow (0.1-0.3 m / h), high-speed (512 m / h) and ultra-high-speed (36-100 m / h).
All types of conditioning most often relate to the normalization of the mineral composition of water. They are divided into two groups: 1) removal of excess amounts of salts and gases from water - softening, desalination and desalination, deferrization, defluorization, 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 (fluorine, etc.) in it. The more common methods for improving the quality of drinking water include the following. The method of ion exchange, which is based on passing water through ion exchangers (anion exchangers and cation exchangers), installations made of special insoluble granular materials (ion exchange resins), which have the property of exchanging their constituent ions for the ions contained in the filtered water. Water softening - 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 the lack of the trace element fluorine is noted. This method is proposed to reduce the incidence of dental caries. With an increased content of fluorine, defluorination of water is done with the help of aluminum or magnesium hydroxide or tricalcium phosphate, which precipitate fluorine.
At the slightest suspicion of water infection, it must be carefully checked and, if necessary, disinfected. All types of water disinfection are divided into two groups: reagent and non-reagent.
Reagent water disinfection methods. Of these methods, the most common is the chlorination of drinking water. 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 (OSH), which can form HOC1 in an aqueous medium. The acid penetrates the bacterial cell membrane and disrupts the function of enzymes that catalyze redox processes that provide this cell with energy. the formation of bactericidal chlorine compounds when used in different forms can be seen from the following reactions: when chlorine is dissolved in water, the reaction C12 + H20 = HOC1 + H * + + CG occurs, the hydrolysis of chlorine gives 99.9% HOC1 at 0 ° C and 99 , 97% at 25 ° C.
Under industrial conditions, bleach with an active chlorine content of 35 to 39% is often used for the chlorination of 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 waterworks, 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. For this, residual chlorine is determined hourly in chlorinated water during the day, and the titer of Escherichia coli is determined daily. The latter in chlorinated water should be at least 300 ml. The chlorine dosage depends on the state of water contamination. It is considered sufficient if the water after chlorination contains not 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 demand of water is determined accurately enough in the laboratory. In case of dangerous contamination of water, it is treated with large doses of chlorine, superchlorination, and excess
the chlorine dose is eliminated by dechlorination. The latter is most often carried out after appropriate calculations with 0.5% solutions of sulfurous acid (hyposulfite) or sodium sulfate.
In addition to chlorination from reagent water disinfection methods, I will use
They also disinfect it with ozone, iodine and silver ions.
Reagent-free methods of water disinfection include ultraviolet irradiation, treatment with ultrasound, gamma radiation, etc. U F-irradiation provides reliable water disinfection, which is achieved by the biologically active part of the ultraviolet spectrum. Many studies have established that rays with a wavelength of 295-200 nanometers have the most active effect on bacteria.
For disinfection of water using UV rays, high-pressure mercury-quartz lamps of the PRK type (direct mercury-quartz), BUV-60 are used.
Disinfection of water by ultrasound is based on the bactericidal action of this physical factor by mechanical destruction of bacteria in an ultrasonic field. With regard to the disinfecting effect of gamma radiation, then, as reported by S. N. Cherkinskiy (1974), at the appropriate dose rate, microorganisms die very quickly. However, this method requires special conditions.
Boiling is also a reagent-free method for water contamination. This is a simple and very reliable method that allows you to neutralize a small amount of water. 
b 7
Self-purification of water in reservoirs is a combination of interconnected hydrodynamic, physicochemical, microbiological and hydrobiological processes leading to the restoration of the initial (background) state of a water body. The decisive role in self-cleaning belongs to biological and physicochemical processes; the latter prevail in the presence of toxic substances in the water that inhibit biological processes. The self-cleaning 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 solids, bottom sediment, silt, etc. One of the main factors of self-cleaning (reducing the concentration of pollution) is dilution, although 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 physicochemical processes take place here, thanks to which the chemical and biological qualities of water are restored. Waste liquid and sewage, getting into water bodies, are diluted with water. Some of the microbes settle to the bottom and are destroyed there. Pathogenic bacteria die under the influence of light, unfavorable temperature for them, bactericidal action of oxygen dissolved in water. A huge number of bacteria are devoured by unicellular protozoa, crustaceans and other zooplankton organisms. [...]
Self-purification of water in open reservoirs from bacterial contamination occurs due to a complex complex of physical, chemical and biological factors, which is facilitated by the dilution of contaminants with a large mass of water, mixing, sedimentation of suspensions, the influence of sunlight, aeration, etc. Under the influence of biochemical processes occurring in water , especially oxidizing, pathogenic microbes die. Bacteria, in addition, are destroyed by protozoa, which swallow them like. food. Bacteriophages, microbes-antagonists and antibiotics of biological origin also have a destructive effect on bacteria.
Self-purification of polluted natural waters occurs with multiple (1: 7 ... 1:12) dilution with clean water. These processes in confined water bodies and groundwaters are slow. Complete self-purification of the water of the World Ocean will occur only after 2600 years, and underground - after 5000 years. [...]
Self-purification of water from oil is a multi-stage process, sometimes stretching for a long time. [...]
The composition of water from natural surface sources is variable. In them, the processes of oxidation, reduction, precipitation of large and heavy particles, as well as biochemical processes, leading to self-purification of water, continuously occur. The composition of the surface waters of the land varies greatly by the seasons of the year, as well as occasionally as a result of atmospheric precipitation. Mineralization of groundwater, especially deep-seated, is subject to much less fluctuations. [...]
The composition of water in natural sources is variable. In it, the processes of oxidation, reduction, precipitation of large and heavy particles, as well as a number of biological processes that lead to self-purification of water are continuously proceeding. [...]
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 the soil lumps. [...]
The process of self-purification of water from pollution by prof. SN Stroganov divides into two stages: 1) mixing of the polluted jet with the entire mass of water, that is, a purely physical phenomenon; 2) self-purification in the proper sense of the word, that is, the processes of mineralization of organic substances and the withering away of bacteria introduced into the reservoir. [...]
The water quality of underground water sources when used for household and drinking purposes without purification and disinfection must comply with the standards GOST 2874-73 "Drinking water", sanitary and microbiological analysis is performed by the methods set forth in GOST 18963-73. To assess the process of microbial self-purification in groundwater, the entire group of Escherichia 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 be, in this case, a reliable indicator of self-purification of waters from enteroviruses (E. I. Molozhavaya et al., 1976). [...]
If wastewater is discharged into a reservoir or soil inhabited by living organisms, then these processes occur naturally. Living organisms that seek food in polluted wastewater are ubiquitous. With an increase in the amount of nutrients, their number increases rapidly, and when the supply of food is 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, it can be assumed that the microorganisms in our water bodies are always provided with the necessary nutrients. After the wastewater pollution has undergone decomposition and degradation as a result of a variety of physical, chemical and biological processes, it is gradually carried down from the wastewater outlet. We call this process self-cleaning of the reservoir. In other words, self-purification of water in a river or lake is a return of water to its natural, original state, which was disturbed as a result of the discharge of wastewater into it. [...]
The intensity of water self-purification from oil products entering them largely depends on the temperature: at 20-25 ° C in 20 days, 50-80% of the total amount of oil entered into the water is oxidized, while at 5 ° C only 10-20%. in water, oil and its decomposition products are sorbed by bottom sediments, and clayey silts have the greatest sorption capacity. [...]
The main mechanism of self-purification of water from individual groups of organic substances, when biochemical effects are most pronounced, is the degradation of oil. The fractionation and cumulative effect of various factors after oil enters water is well known; evaporation plays an important role in the destruction of oil slicks. 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 over C25 practically do not evaporate. In general, evaporation alone can remove up to 50% of hydrocarbons in crude oil, up to 10% of heavy and up to 75% of light fuel oils. [...]
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, of the pathogenic intestinal group occurs as a result of the release of bactericidal substances by algae. Therefore, in the process of additional treatment of wastewater in biological ponds, not only the removal of biogenic and organic substances, but also bacterial contamination takes place. As already mentioned, strictly aerobic biological ponds should be used for the purpose of additional treatment. The prerequisites for the normal operation of such ponds are the observance of the reaction of the medium (pH) and temperature, which are optimal for aquatic organisms, as well as the presence of dissolved oxygen of at least 1 mg / l. Mixing of water is important, which prevents the formation of anaerobic zones and promotes the processes of stabilizing water quality. [...]
A very great contribution to the self-purification of waters of animals - inhabitants of reservoirs. By processing organic matter created by plants in food connections, animal consumers decompose part of this substance to the original simple compounds - water and carbon dioxide, the rest in the form of excrement goes into a form that is most effectively used by microorganisms-reducers. Part of the organic matter is deposited in bottom silts. [...]
Influence on the processes of self-purification of water bodies. The tungsten concentration of 1 mg / l in the experimental reservoir inhibits the MIC, the processes of ammonification and nitrification of organic compounds, and the growth of microflora. The tungsten concentration of 0.1 mg / l inhibits the processes of self-purification of water by 10-20%, and 0.01 mg / l does not affect them. [...]
The entry of pollutants into river water disrupts the physicochemical balance in the river flow. Self-purification of water takes place to restore it in the dispersion halos of pollutants. Self-cleaning is a system of mechanical, chemical and biological processes that reduce the amount of pollutants and change the form of their occurrence. Self-cleaning is carried out by dilution with atmospheric precipitation or water from tributaries. [...]
The main factor in the processes of self-purification of water is its oxygen saturation. Under the influence of dissolved oxygen, organic matter oxidizes and falls to the bottom of reservoirs in the form of mineral sediment. [...]
The conditions for the discharge of return (waste) waters into water bodies are determined taking into account the degree of mixing of return (waste) waters with the water of a water body at a distance from the place of discharge of return (waste) waters to the nearest control point of water use, as well as the background composition of water bodies at places of waste water The natural self-purification of waters from the substances entering them is taken into account if this process is sufficiently pronounced and its laws 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; sedimentation of lumps, especially overloaded with sediment and dust; clumping of lumps suspended in the water column; floating up of lumps, forming a film with inclusions of water and air; reduction of concentrations of suspended and dissolved oil due to sedimentation, 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 in the water of colloids, suspended and entrained plankton particles, etc., air temperature and sunlight. [...]
It is known that when discharging biologically treated wastewater into a reservoir, it is desirable to have the highest possible concentration of dissolved oxygen in these waters. This makes it possible to speed up the processes of self-purification of water in the reservoir 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 is replaced by antagonism. [...]
It should be emphasized that organic substances of domestic 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 pollution of water bodies. At the same time, the end of the process of mineralization of organic substances of domestic wastewater, and, consequently, the weakening or elimination of the danger of pollution of the 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 reservoirs with organic substances of domestic wastewater and its limitation by the value of biochemical oxygen demand (BOD). [...]
According to the first criterion, the influence of harmful substances on the processes of self-purification of water from organic contaminants in wastewater is assessed, for which the amount of oxygen required for the oxidation of organic substances and the development of aquatic microflora is determined. In this case, the characteristics of water pollution are biological and chemical oxygen consumption (MIC and COD - see Section 6.4.2). [...]
In accordance with the regulatory requirements for BOD, when discharging wastewater into water bodies, the total biochemical oxygen demand at 20 ° C should not exceed 3 mg / l in a category I reservoir and 6 mg / l in a category II reservoir. When calculating the permissible BOD total of treated wastewater discharged into the reservoir, along with the possible degree of their dilution in the reservoir water, the rate of biochemical processes, self-purification of water in the reservoir in the area from the wastewater discharge site to the nearest water use point 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 the pollution of the reservoir by sewage, the calculation of organic pollution released into the reservoir is carried out on purpose. [...]
The study of the effect of chemicals on the organoleptic properties of water (color, pricing, smell, taste) is of greater practical importance, since changes in the properties of water that are familiar to people are easily detected and is a kind of danger signaling device, which leads to a sharp decrease in the use of the water source. An experimental study of the effect of chemicals on the general sanitary regime of reservoirs is carried out in order to prevent disruption of the self-purification processes of water in a reservoir. The simultaneous study of the stability and transformation of a substance in water is aimed at determining the duration of its content in an aquatic environment and a hygienic assessment of possible products of its transformation in comparison with the initial substance in accordance with the "Methodological guidelines for the experimental study of the processes of transformation of chemicals during their hygienic regulation in water" ( No. 2968-84). [...]
The usual chemical and technological characteristics of substances in terms of solubility in water should not be mechanically transferred to the field of hygienic research, where, as a rule, one often has to meet with very low concentrations of these substances in water bodies. The methodology for studying the stability of hazardous substances in industrial wastewater is subject to the requirements of sanitary practice, from the point of view of which the slowly proceeding process of self-purification of water loses its importance. [...]
As noted by many authors, all aquatic organisms 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 aquatic organisms, 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 the water so much that it becomes unsuitable for drinking. Many authors proposed to prevent the possibility of water “blooming” by acting on 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 urgent. In this regard, issues related to both the study of sources of pollution of water resources and the development of methods for their purification acquire particular importance. It is known that in the natural self-purification of water, a huge role belongs to the biocenosis of organisms-hydrobionts - 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 the water supply systems of enterprises, as a result of which the pipes become clogged and problems are created with high-quality and timely provision of technological processes. In this regard, the study of the composition of the biocenosis of phyto-growths and the development of measures to combat them is an urgent problem. [...]
Taking into account that in solving equations (26) and (27) it is difficult only to calculate the values 10- "1, which reflect the process of self-purification of water from organic substances, we have compiled an auxiliary table 22. [...]
Since the process of biochemical oxidation of organic substances, accompanied by their mineralization, occurs in the reservoir, the calculation of the permissible discharge of wastewater should take into account not only the possible dilution, but also the degree of self-purification of the reservoir water from organic pollution on the way to the nearest water use point. self-purification, it will depend on the rate of the biochemical process / Ci and the time t - the movement of water from the area of wastewater discharge to the nearest point of water use. [...]
According to the calculations of the State Oceanographic Institute, up to 950 tons of detergents and 80 tons of mercury come from the North Sea to the Baltic every year. Since the intensity of the processes of self-purification of the Baltic Sea waters is rather low, which is associated with a low water temperature, the problem of stabilizing the level of pollution and their elimination is becoming more and more 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 and over 80% of the country's fresh water volume. The ecosystem of Lake Baikal is remarkable for its amazing wealth and originality - the lake is home to at least 2,400 species and varieties of animals and plants. Its unique feature is the presence of a subtle biological mechanism for self-purification of waters. [...]
The hygienic significance of the fact of the development of microflora under the influence of surfactants can be different depending on specific conditions. Obviously, the development of saprophytic bacteria in the reservoir changes the conditions for self-purification of water from organic pollution, in particular, domestic wastewater, and also changes the sanitary-indicative value of these microorganisms. The multiplication of the same bacteria in drinking water can negatively affect the quality of the water. Reproduction of pathogenic microflora is in any case 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 having scientific and practical significance. Thus, the study of the stability of substances in water makes it possible to isolate both substances with pronounced stability and substances that change the composition and properties in water of 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. The study of the protective ability of modern methods of purification and disinfection of drinking water makes it possible to isolate substances that do not linger or are not rendered harmless at water supply facilities. In these cases, hygienic rationing studies should be carried out with extreme caution. [...]
Biological ponds are available with artificial or natural aeration. Recently, a method has been developed for calculating channel-type artificial flowing ponds (Fig. 50). Usually they are built on land unsuitable for agriculture. In artificial biological ponds, it is envisaged to create optimal modes 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, device 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 characterization of these sources. Depending on environmental factors, these microorganisms are divided into marine, freshwater, salt lakes, swamps, streams, rivers, waterfalls, hot springs and mineral springs. In freshwater springs, benthic microorganisms take part in water purification: they mineralize organic substances, and oxidize reduced inorganic substances; the dominant role in these processes belongs to microbes. The richest in bacteria is the surface layer of silt, which has a very significant effect on the development and life of microorganisms in water bodies and watercourses. Filamentous sulfur and iron bacteria play a significant role in the self-purification of waters. The former oxidize hydrogen sulfide in sulfuric acid salts, thereby protecting the fish from death; the second - iron (II) to iron (III). At the bottom of reservoirs, fermentation processes also take place with the formation of methane and carbon dioxide. 1 g of silt 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 amount of aerobic fiber breakers. The sludge also contains bacteria that oxidize methane and hydrogen, fermentation agents, an anaerobic fixer 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 the speed of currents 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 of regulation of water reserves of reservoirs, causes a change in the processes of self-purification of waters in comparison with river ones, determines the thermal regime of the upstream and downstream pool. Water exchange largely determines the main hydrological features of reservoirs, 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, due to the 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, converting forest litter and decaying remains of animals 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 are involved in the biogeochemical cycles of nitrogen, sulfur, phosphorus. Self-purification of water in natural reservoirs, as well as wastewater treatment is performed by aerobic and anaerobic heterotopic bacteria. [...]
An analysis of the quantitative relationships between viruses, E. coli phages, and BGKPs detected in natural conditions also indicates a greater exponential factor of the phage in reflecting viral contamination of both heavily and moderately polluted river water. The same data made it possible to substantiate the quantitative criteria of the E. coli phage, guaranteeing epidemic safety in relation to viral contamination of water from sources of household and drinking water supply - no more than 1000 pfu per 1 liter (T. 3. Artemova et al., 1977). The same value testifies to the completion of the processes of self-purification of the water source from viruses during the establishment of zones of sanitary protection of water pipelines (GA Bagdasaryan, LA Myshlyaeva, 1976). [...]
The discharges of the pollutants under consideration in the designated areas and in large cities were determined according to the reporting data of 2TP (vodkhoz) for 1989 and distributed over the above areas. Discharges of pollutants in the cities of Orel, Kaluga, Aleksin, Serpukhov, Stupino, Kashira, Kolomna, Ryazan, Kasimov, Vyksa, Murom, Pavlovo, Bogorodsk, Dzerzhinsk, standing directly on the trunk of the river. Oka, were taken according to the corresponding reporting table 2TP (vodkhoz) and subtracted from the discharges of pollutants into the trunk of the river. Oki in the corresponding areas. Discharges of pollutants into small rivers, which were not presented in the report of the GKI, were taken as discharges entering directly into the trunk of the river. Oki. This somewhat overestimated their influence on the concentration of pollutants in the river. Oka, since the self-purification of water in the channels of these small rivers was not taken into account. The resulting overestimation of the concentrations of pollutants obtained in the modeling can be attributed to the “safety margin” of measures for wastewater treatment.
From a sanitary point of view, the processes of natural water purification, or self-purification of water bodies, are of great interest. The self-purification process does not occur in clean waters, but develops only in connection with the influx of contaminants.
The factors of self-purification of water bodies from incoming pollution, including from foreign microorganisms (biological self-purification), are numerous and varied. They can be conditionally divided into three groups - physical, chemical, biological.
Physical factors... Among these factors, the dilution, dissolution and mixing of the incoming contaminants are of paramount importance. The sedimentation of insoluble sediments in water also promotes self-cleaning. The microflora of water is influenced by solar radiation, hydrostatic pressure, temperature, etc.
Dilution... Rapid and intensive dilution of polluting waters with clean water of the reservoir leads to a drop in the concentration of organic compounds, i.e. a decrease in the concentration of nutrients, which leads to an acceleration of the death of bacteria that have come from outside, including pathogenic ones. Self-purification of running water in rivers is more intensive than in stagnant waters (lakes, ponds).
As a result of dilution of wastewater that has entered the reservoir with a significant amount of pure water, their transparency increases, which contributes to a deeper penetration of ultraviolet rays of sunlight, which have a detrimental effect on both saprophytic and pathogenic microorganisms. The degree of dilution is also taken into account when standardizing chemical pollutants entering water bodies.
Subsidence in water of insoluble sediments, sedimentation of contaminated water also contributes to the self-purification of water bodies. Microorganisms, due to their own gravity or adsorption on other organic and inorganic particles, gradually settle to the bottom, are subjected to the subsequent action of other self-cleaning factors.
Temperature... There are differences in the intensity of self-purification of water bodies in summer and winter, as well as in hot, temperate and cold climatic zones. In the summertime, microorganisms begin to actively multiply already in the drains, and in the water of reservoirs their number decreases. In winter, the processes of microbial self-purification slow down: the multiplication of bacteria occurs only near the drains, the rate of death decreases, the high content of microorganisms in the reservoir lasts longer than in summer. Therefore, the sanitary condition of reservoirs in winter is worse, moreover, a decrease in temperature contributes to the preservation of enterobacteria in it - pathogens of intestinal infections. The waterway of the spread of intestinal infections is observed more often in winter.
Chemical factors... The self-purification process is affected by the oxidation of some organic and inorganic substances, aeration of water in reservoirs, the presence of some salts (for example, NaCl), halogens (iodine, bromine, etc.), water pH.
The intake of a large amount of harmful chemical compounds (detergents, oil products, pesticides) in the wastewater composition suppresses the reproduction of saprophytic flora, inhibits biocenoses that are actively involved in self-purification processes. All this can contribute to lengthening the survival time of pathogenic microorganisms in water, which increases the epidemic danger of the reservoir.
Biochemical factors... Some chemical factors of self-purification (pH change, the appearance of metabolic products, etc.) are closely related to biological factors, most often they are the next natural stage in the manifestation of their action. These factors are the link between chemical and biological factors. Sometimes they are singled out as an independent group.
Biological factors... The rate of self-purification of water bodies is influenced by the competitive relationship that develops between different groups of microorganisms in the struggle for oxygen and nutrients.
The essence of the antagonistic action of autochthonous microflora against allochthonous bacteria, viruses, microscopic fungi consists in the release of toxic substances and compounds such as antibiotics by antagonist microbes. The water of some lakes and especially sea water has bactericidal properties.
Hydrolytic microorganisms contribute to purification by decomposing proteins, fats, carbohydrates of dead plants and animals. Oil-oxidizing bacteria play a great role in self-cleaning from oil pollution. Microorganisms also participate in the destruction of carcinogenic hydrocarbons.
Biological self-purification is also associated with the action of phages, which in abundance enter water bodies along with the bacteria themselves. An increase in the concentration of phages of pathogenic enterobacteria is found near settlements. However, for the manifestation of the activity of phages, a relatively high temperature is required.
In the process of self-purification of water, some representatives of phytoplankton, protozoa, aquatic plants, animals (for example, biofilter mollusks) take part.
The combination of all these factors leads to the fact that, even in very polluted water bodies, as the distance from the source of pollution and over time, the water becomes cleaner and its hygienic qualities improve.
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