Requirements for reservoirs for fishery purposes. Standardization of water quality in reservoirs and streams. the background composition and properties of water in the reservoir in the places of wastewater discharge

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RULES FOR THE PROTECTION OF SURFACE WATER (STANDARD PROVISIONS) (approved by the State Committee for Nature Protection of the USSR 21-02-91) (2017) Actual in 2017

2. Rationing the quality of water in reservoirs and watercourses

2.1. Rationing of water quality consists in establishing for the water of a water body a set of permissible values of indicators of its composition and properties, within which the health of the population, favorable conditions for water use and the ecological well-being of the water body are reliably ensured.

These Rules establish the standards for the quality of water in reservoirs and watercourses for the conditions of economic - drinking, communal - household and fishery water use.

Note. As the development and approval of environmental requirements and standards for the state of water bodies, as well as special requirements for the protection of waters used for the purposes Agriculture, these requirements will be taken into account, and the Rules will be supplemented with the corresponding sections at the next revision.

2.1.1. Economic and drinking water use includes the use of water bodies or their sections as a source of economic and drinking water supply, as well as for water supply to food industry enterprises.

Communal - domestic water use includes the use of water bodies for bathing, sports and recreation of the population. Requirements for water quality established for municipal water use apply to all sections of water bodies located within the boundaries of populated areas, regardless of the type of their use.

2.1.2. Fishery water use includes the use of water bodies for habitation, reproduction and migration of fish and other aquatic organisms.

Fishery water bodies or their sections can belong to one of three categories:

the highest category includes the locations of spawning grounds, mass feeding and wintering pits of especially valuable and valuable species of fish and other commercial aquatic organisms, as well as protection zones of farms of any type for artificial breeding and rearing of fish, other aquatic animals and plants;

2.1.3. Types of water use at a water body within a region (krai), union (autonomous) republic are determined by the bodies of the State Committee for Nature Protection together with the bodies of state sanitary supervision and are subject to approval by the regional (territorial) executive committees of the Councils of People's Deputies or the Councils of Ministers of the Union (autonomous) republics.

On the water bodies bordering between territorial - administrative units, the type of water use is established by a joint decision of the relevant authorities.

2.2. Water quality standards for water bodies include:

General requirements for the composition and properties of water in streams and reservoirs for different types water use (Appendix 1);

The list of maximum permissible concentrations (MPC) of standardized substances in the water of water bodies used for household - drinking and communal - household needs of the population (Appendix 2);

The list of maximum permissible concentrations (MPC) of standardized substances in the water of water bodies used for fishery purposes (Appendix 3).

Notes. 1. The lists of MPCs must contain: the full name of the substance and its synonyms (if they exist), the limiting sign of hazard, the hazard class, the normative numerical value indicating the unit of measurement. In the absence of MPCs for substances contained in waste water of enterprises designed or under construction, at the stage of preventive control, indicative permissible levels (TAC) of the content of these substances in water are established, developed on the basis of calculated and express - experimental methods for predicting toxicity.

2. Lists of standardized substances and their MPC values in water of water bodies used for economic - drinking and communal - household needs of the population are approved by the USSR Ministry of Health, for fishery purposes - by the USSR Ministry of Fisheries.

Lists of standardized substances and their MPC values are published as additions to these Rules as they are developed and updated.

Methods for analyzing the content of substances in surface and return (waste) waters are developed by competent organizations, approved and recommended for use by the USSR State Committee for Nature Protection.

2.3. For all standardized substances for fishery water use and for substances belonging to 1 and 2 hazard classes for economic and drinking and cultural and domestic water use, when several substances enter water bodies with the same limiting hazard sign and taking into account impurities entering water body from upstream sources, the sum of the concentration ratios (C1, C2 ... Cn) of each of the substances in the control section to the corresponding MPC should not exceed one:

C1 / MPC1 + C2 / MPC2 + ... + Сn / MPCn<= 1.

2.4. When discharging return (waste) waters or other types of economic activity affecting the state of water bodies used for economic - drinking and communal - domestic purposes, the standards for the quality of water of reservoirs and watercourses or its natural composition and properties in case of exceeding these standards must be observed in watercourses on a site one kilometer above the nearest water use point upstream (water intake for domestic and drinking water supply, bathing places, organized recreation, the territory of a settlement, etc.), and in water bodies - in the water area within a radius of one kilometer from the water use point ...

When discharging return (waste) waters or other types of economic activity affecting the state of fishery watercourses and reservoirs, the norms of water quality in water bodies or its natural composition and properties in case of exceeding these norms must be observed within the entire fishery site, starting from the control section, determined in each specific case by the republican (regional) Councils of People's Deputies on the proposal of the State Committee for Nature Protection, but no further than 500 m from the place of wastewater discharge or the location of other sources of impurities that affect the quality of water (places of extraction of minerals, production of work on water body, etc.).

Note. In reservoirs and in the downstream of the dam of a hydroelectric power plant operating in a sharply variable mode, it is necessary to take into account the possibility of impact on the points of water use of the reverse flow in the event of a sharp change in the operating mode of the power plant or the termination of its operation.

2.5. A water body or its section is considered contaminated if the water quality standards in the water body are not observed in the places of water use. In the case of the simultaneous use of a water body or its section for various needs of the population and the national economy, the most stringent standards from among the established ones are imposed on the composition and properties of water.

2.6. If in a water body, under the influence of natural factors, the maximum permissible concentration is exceeded for certain substances, then for these water bodies the USSR State Committee for Nature Protection, together with the USSR Ministry of Health and / or the USSR Ministry of Fisheries, can establish regional water quality standards in accordance with natural background concentrations. Information on regional water quality standards is published as supplements to these Rules.

2.7. For unique water bodies of ecological, scientific, historical or cultural value, special requirements for water quality may be established. Such water bodies can be given the status of a nature reserve or wildlife sanctuary in the manner prescribed by law.

2.8. Separate watercourses, reservoirs or their sections can be provided for separate water use for use mainly for certain economic purposes, for example, for fish farming, cooling heated waters (cooling ponds), creating logging bases and other purposes.

The provision of a water body for separate water use is carried out in the manner prescribed by law.

Surface water protection

The importance of water in the life of living organisms. Water reserves in the world. Distribution of water resources. Uneven distribution.

Water consumption by industry, agriculture. For household and drinking purposes. Irrational spending.

Sources of pollution of water bodies. What properties of surface waters change during the discharge of wastewater.

The composition and properties of wastewater.

Self-cleaning of reservoirs. The role of physical and biological factors in this process.

Processes of mixing and dilution of wastewater in a reservoir. Mixing ratio and dilution ratio.

Water quality standards for sanitary water bodies.

Rules for the discharge of wastewater into water bodies. Maximum permissible discharges (MPD).

Consideration of the harmful effects of a number of substances with their simultaneous presence in the water of reservoirs. Conditions for the harmlessness of water.

Wastewater treatment methods.

The main measures for the protection of water bodies.

one . The importance of water in the life of living organisms. Water reserves in the world. Distribution of water resources. Uneven distribution. The importance of water in life processes is determined by the fact that it is the main medium in the cell, where metabolic processes take place, and serves as the most important initial, intermediate or final product of biochemical reactions. The special role of water for terrestrial organisms (especially plants) is the need for constant replenishment due to evaporation losses. Therefore, the entire evolution of terrestrial organisms went in the direction of adaptation to the active extraction and economical use of moisture. Finally, for many species of plants, animals, fungi and microorganisms, water is their immediate habitat. 97.2% of the water on Earth belongs to salty oceans, seas and saline groundwater bodies. The remaining 2.8% are fresh water reserves. On Earth, it is distributed as follows: - 2.15% of fresh water is frozen in mountain glaciers, icebergs and ice shells of Antarctica and the Arctic; - 0.001% of fresh water is contained in the atmosphere; - 0.65% is contained wherever a person can get it: in rivers, freshwater lakes and springs.

2. Water consumption by industry, agriculture. For household and drinking purposes. Irrational spending. Agriculture accounts for more than 2/3 of the world's water consumption, and approximately 17% of the cultivated area worldwide is irrigated. Now in the world about 15 mln. quad. km. Industrial water consumption has now reached enormous proportions. According to experts, the irretrievable water consumption was about 150 cubic meters. km per year, that is, 1% of sustainable freshwater flow. According to calculations, the demand for water on Earth until 2000 will increase by an average of 3.1% per year. Currently, people consume 3000 km of fresh water annually. Irrigated agriculture is one of the main consumers of water - 190 m3 / year. To grow 1 ton of cotton, 4-5 thousand m3 of fresh water is required, 1 ton of rice - 8 thousand m3. During irrigation, most of the water is consumed irretrievably. Irrigation water consumption depends on three factors: irrigated area, crop composition and irrigation technique. Municipal water consumption exceeds 20 km3 / year. The level of development of municipal water supply is determined by two indicators: the provision of the population with centralized water supply and the amount of specific water consumption. An important task is to reduce the consumption of tap water for technical needs. Water consumption in industry is high (about 90 km3 / year). Smelting 1 ton of steel requires 200-250 m For example, at old petrochemical plants for processing 1 ton. oil consumption is 18-22 m3 of water, while at modern plants with recycled water supply and air cooling systems - about 0.12 m3 / year. At present, the situation is aggravated by the fact that after the privatization of the bulk of enterprises, including environmentally dirty enterprises, the new owners do not have enough money to build or modernize treatment facilities.

3. Sources of pollution of water bodies. What properties of surface waters change during the discharge of wastewater. The main sources of pollution and contamination of water bodies are insufficiently treated wastewater from industrial and municipal enterprises, large livestock complexes, production wastes from the development of ore resources; water of mines, mines, processing and alloying of timber; discharges of water and rail transport; flax primary processing waste, pesticides, etc. Pollutants entering natural reservoirs lead to qualitative changes in water, which are mainly manifested in changes in the physical properties of water, in particular, the appearance of unpleasant odors, tastes, etc.); in the change in the chemical composition of water, in particular, the appearance of harmful substances in it, in the presence of floating substances on the surface of the water and their deposition at the bottom of reservoirs. Waste water is divided into three groups: waste water, or fecal; household, including drains from the galley, showers, laundries, etc.; sub-seam, or oil-containing. As a result

discharging waste water, the physical properties of water change (increases

temperature, transparency decreases, color, tastes appear,

smells); floating substances appear on the surface of the reservoir, and at the bottom

a precipitate is formed; the chemical composition of water changes (increases

substances, the oxygen content decreases, the active reaction changes

environment, etc.); the qualitative and quantitative bacterial

composition, pathogenic bacteria appear. Polluted bodies of water become

unsuitable for drinking, and often for technical water supply;

lose their fishery value, etc.

4. Composition and properties of waste water. Many waste waters of chemical industries, in addition to dissolved organic and inorganic substances, may contain colloidal impurities, as well as suspended (coarse and finely dispersed) substances, the density of which may be greater or less than the density of water. In some cases, wastewater contains dissolved gases (hydrogen sulfide, etc.). Most often, wastewater is a complex system containing a mixture of various substances.

The degree of hazardousness of wastewater depends on the toxicity of its pollutants. Impurities such as salts of heavy metals, hydrogen sulfide, carcinogenic substances and others cause high toxicity. Waste water can contain flammable and explosive substances. The presence of a large amount of suspended solids that can polymerize in an aqueous solution can lead to clogging of pipelines and collectors. Waste water often contains substances with a strong unpleasant odor (sulphides, hydrogen sulphide). Many waste water from chemical plants is colored due to contamination with dyes and other colored substances. The ingress of household water into industrial water leads to biological pollution of the latter. The wastewater temperature can fluctuate within different limits.

5. Self-cleaning of reservoirs. The role of physical and biological factors in this process. Self-cleaning is a complex complex of physical, physicochemical, chemical and biochemical phenomena. The hydrodynamic processes of mixing the runoff with the water of the reservoir largely determine the intensity of self-purification, since they reduce the concentration of pollutants. The physical factors of self-purification also include the processes of precipitation of insoluble impurities entering the reservoir with wastewater. The physical phenomena of sedimentation are closely related to the vital activity of aquatic organisms - filter feeders and sedimentators. They extract huge amounts of suspended solids from the water and throw away undigested material in the form of fecal lumps, which easily settle to the bottom. The process of formation of pseudofeces by mollusks is even more important. Thus, aquatic organisms accelerate the sedimentation process, helping to purify water from suspended solids and their deposition into bottom sediments. Purely chemical reactions of neutralization, hydrolysis, and oxidation also take place in the reservoir. For example, during self-purification from Fe, Mg, Al ions, the predominant process is the reaction of the formation of hydroxides of these metals, followed by their precipitation. Self-purification from heavy metal ions occurs due to a number of processes: coprecipitation with hydroxides of the above metals, sorption of ions by organic colloids, and the formation of complex organometallic complexes with humic acids. The share of participation of each of these processes in the removal of heavy metals depends on pH, redox conditions in the reservoir, and the concentration of metals. As a result, the water is freed from heavy metals, and their accumulation occurs in the bottom sediments. Changes in redox conditions in bottom sediments can lead to the transfer of metal ions into the water layer, i.e. to secondary water pollution

6. Processes of mixing and dilution of wastewater in a reservoir. Mixing ratio and dilution ratio.Dilution of waste water is the process of reducing the concentration of impurities in water bodies caused by mixing of wastewater with the aqueous medium into which they are discharged. The intensity of the dilution process is quantitatively characterized by the dilution ratio "A".

For reservoirs with a directed flow, the dilution ratio is determined by the formula:

m = (mQ in + Q v) / Q v,

where Q v is the volumetric flow rate of wastewater discharged into the reservoir with the volumetric flow rate of water Q in;

m is the mixing ratio, showing what part of the water flow in the reservoir is involved in mixing.

The mixing ratio is determined by the formula:

where k = - coefficient characterizing the hydraulic mixing conditions;

y - coefficient characterizing the location of the wastewater outlet (for onshore outlet y = 1, for discharge into the channel section y = 1,5);

j = L / Ln - coefficient of channel tortuosity;

L is the length of the channel from the outlet section to the design alignment;

Ln is the distance between the same parallel sections in the normal direction;

D T - coefficient of turbulent diffusion, determined by the Karaushev formula:

D T = gHw x / Mc w,

where g is the acceleration of gravity;

H is the average depth of the channel along the mixing length;

w x is the average river flow velocity over the channel section at a distance L from the place of wastewater discharge;

S w - 40 ... 44 m 0.5 / s - Shezi coefficient;

M is a function of the Shezi coefficient, for water M = 22.3 m 0.5 / s.

7. Standards for water quality for water bodies for sanitary water use.

2.1. The standards for the composition and properties of water in water bodies, which must be ensured when using them for various economic purposes, are established in relation to certain categories of water use.

The first category includes the use of a water body as a source of centralized or non-centralized drinking water supply, as well as for water supply to food industry enterprises.

2.2. The water use points of the first and second categories closest to possible sources of pollution are determined by the bodies and institutions of the sanitary and epidemiological service, with the obligatory consideration of official data on the prospects for using the water body for domestic drinking water supply and cultural and domestic needs of the population.

2.3. The composition and properties of water in water bodies must meet the requirements in the section located on watercourses one kilometer above the nearest water use points (water intake for domestic and drinking water supply, bathing places, organized recreation, the territory of a settlement, etc.), and on stagnant reservoirs and reservoirs - one kilometer in both directions from the point of water use.

2.4. The composition and properties of water of a reservoir or watercourse at points of drinking and cultural and domestic water use should not exceed the standards given in Appendices No. 1 and 2 ... By SanPiN  4630-88

8. Rules for the discharge of wastewater into water bodies. Maximum permissible discharges (MPD). In accordance with GOST 17.1.01.77 (clause 39), under the maximum permissible discharge (MPD) of substances into a water body, the mass of a substance in wastewater is taken, the maximum permissible water quality at the control point.

The MPD is set taking into account the maximum permissible concentrations of pollutants in the places of water use and the assimilating capacity of the facility. The values of the standards are determined in accordance with the water legislation of the Russian Federation and the current regulatory and methodological documents.

For project development Maximum allowable discharges (draft PDS) an inventory of the sources of discharges is being carried out. At this stage, methods of drainage of wastewater from the territory, the presence of storm sewers and treatment facilities, and ways of disposal of domestic wastewater are determined. Water protection restrictions are identified in the area of the object under study (zones of sanitary protection of sources of drinking water supply, water protection zones of water bodies).

After artificial full or partial cleaning and disinfection, wastewater is discharged into reservoirs. The water of reservoirs contains a certain amount of dissolved oxygen, which can contribute to the oxidation of organic matter in wastewater. These oxygen reserves, spent on the biochemical processes of oxidation of organic substances, are restored by its absorption from the atmosphere by the water mirror (reaeration) and by the assimilation of carbon from carbon dioxide by aquatic plants. The smallest amounts of soluble oxygen in the water of reservoirs occur in the hot season, when warm water loses oxygen, and in winter, in the absence of re-aeration due to the covering of the reservoir mirror with ice. Therefore, a powerful reservoir, which has large amounts of water and oxygen reserves in it, has some self-cleaning ability.

Correct use of this ability of self-purification of water bodies to purify organic wastewater contaminants makes it possible to reduce the degree of artificial wastewater treatment at treatment facilities before being discharged into a water body and sharply reduce the cost of processing them without deteriorating the quality of the water in the reservoir.

Many enterprises have drained and some continue to release contaminated waste water without proper treatment, relying on the self-cleaning capacity (capacity) of the reservoir. As a result, the quality of the natural properties of water in many reservoirs changed for the worse and this excluded the possibility of their normal water use. In some cases, the release of untreated wastewater led to the poisoning of the water of reservoirs, their clogging with silt deposits, oil products, dyes, which led to the death of fish.

In order to stop the practice of pollution of water bodies, the Council of Ministers of the USSR by Decree No. 425 of 22 / 1V-1960 "On measures to streamline the use and enhance the protection of water resources in the USSR" prohibited the discharge of wastewater into water bodies without the consent of the State Sanitary Supervision Authority.

In accordance with this Decree, the Ministry of Health of the USSR on 15 / VII-1961, under No. 372-61, introduced new increased "Rules for the protection of surface waters from sewage pollution." According to these rules, the degree and methods of wastewater treatment, and, consequently, projects for the construction of sewerage of enterprises and settlements must be agreed with the republican bodies of "Protection of surface and ground waters".

9. Taking into account the harmful effects of a number of substances with their simultaneous presence in the water of reservoirs. Conditions for the harmlessness of water. It is important to observe the principle of hygienic regulation with the simultaneous presence of several harmful substances in the water. According to this principle, the substances of one LPV exhibit an additive effect. This means that the total effect of two or more substances of one LPV (contained in the maximum permissible concentration each) will be the same as if any of them, being present in the water in the singular, were contained in two or more MPCs. This provision in the Rules for the Protection of Surface Waters is fixed in the following form: when several substances with the same LPV enter a water body, the sum of the ratios of these concentrations of each of the substances in the calculated section to the corresponding MPCs should not exceed one, i.e.

The aforementioned composition and properties of water in water bodies for domestic drinking and cultural and domestic water use must comply with the regulatory requirements in the alignment located on watercourses one kilometer above the nearby water use point (water intake for domestic and drinking water supply, bathing places, organized recreation, inhabited territory item, etc.). Indicators of water safety by chemical composition, they are determined by chemicals that can negatively affect human health, causing the development of various diseases. They are divided into chemicals of natural origin; substances that are added to water as reagents; chemical substances that enter water due to industrial, agricultural or domestic pollution of water supply sources.

10. Methods of wastewater treatment.Wastewater treatment - treatment of wastewater with the aim of destroying or removing harmful substances from it. The release of wastewater from pollution is a complex production. In it, as in any other production, there are raw materials (waste water) and finished products (purified water)

Wastewater treatment methods can be divided into mechanical, chemical, physicochemical and biological, but when they are used together, the method of treatment and disposal of wastewater is called combined. The application of this or that method in each specific case is determined by the nature of the pollution and the degree of harmfulness of impurities.

The essence of the mechanical method is that mechanical impurities are removed from wastewater by settling and filtration. Coarse particles, depending on their size, are captured by grids, sieves, sand traps, septic tanks, manure catchers of various designs, and surface contamination - by oil traps, oil separators, sedimentation tanks, etc. up to 95%, many of which are used as valuable impurities in production.

The chemical method consists in the fact that various chemical reagents are added to the wastewater, which react with pollutants and precipitate them in the form of insoluble sediments. Chemical cleaning achieves a reduction of insoluble impurities up to 95% and soluble impurities up to 25%.

With the physicochemical method of treatment, finely dispersed and dissolved inorganic impurities are removed from wastewater and organic and poorly oxidizable substances are destroyed, most often from physicochemical methods, coagulation, oxidation, sorption, extraction, etc. are used. Electrolysis is also widely used. It consists in the destruction of organic substances in wastewater and the extraction of metals, acids and other inorganic substances. Electrolytic treatment is carried out in special facilities - electrolyzers. Wastewater treatment using electrolysis is effective at lead and copper plants, paint and varnish and some other areas of the industry.

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Literature

Hydrosphere protection. Standardization of water quality in reservoirs

Water quality is a characteristic of the composition and properties of water, which determines its suitability for specific types of water use.

Water use is understood as the procedure, conditions and forms of water resources use. Rationing of water quality in reservoirs is carried out in accordance with the “Rules for the Protection of Waters” (1991), which establish standards for water quality in reservoirs for conditions: domestic drinking, household and fishery water use.

Domestic and drinking water use includes the use of water bodies or their sections as sources of domestic and drinking water supply, as well as for water supply to food industry enterprises.

Domestic water use includes the use of water bodies for bathing, sports and recreation of the population. Requirements for water quality established for municipal water use apply to all sections of water bodies located within the boundaries of populated areas, regardless of the type of their use.

Fishery water use includes the use of water bodies for habitation, reproduction and migration of fish and other aquatic organisms.

Fishery water bodies or their sections can belong to one of three categories:

the highest category includes the location of spawning grounds, mass feeding of especially valuable and valuable species of fish and other commercial aquatic organisms, as well as protective zones of farms for their artificial breeding;

the first category includes water bodies used for the preservation and reproduction of valuable fish species that are highly sensitive to oxygen content;

the second category includes water bodies used for other fishery purposes.

Water quality standards include:

general requirements for the composition and properties of water in reservoirs for various types of water use, which include indicators such as: the presence of suspended solids, floating impurities, odor and taste, color, dissolved oxygen, pathogens, toxic substances, as well as water temperature, pH, mineralization of water, biochemical oxygen demand (BOD total), (see Appendix G);

a list of maximum permissible concentrations (MPC) of standardized substances in the water of water bodies used for household and drinking and household needs of the population, which are approved by the Ministry of Health of the Russian Federation (see Appendix I);

a list of maximum permissible concentrations (MPC) of standardized substances in the water of water bodies used for fishery purposes, which are approved by the Ministry of Fisheries of the Russian Federation.

For water, MPCs have been established for more than 960 chemical compounds, which are combined into three groups according to the following limiting hazard indicators (LPV): sanitary and toxicological (s. - t.); general sanitary (general); organoleptic (org.). In the lists of MPCs, LPV, hazard class, standard numerical value with an indication of the unit of measurement must be indicated.

Organoleptic indicators are understood as those that determine the appearance of water and are perceived by the senses (vision, smell). The description and definition of organoleptic properties is important for the sanitary characteristics of water: the presence of foreign odor and color indicates water pollution; turbid water is unpleasant in appearance and suspicious of a bacterial relation; humic acids, which determine the color of water, can adversely affect mineral metabolism in the body, etc.

For all standardized substances for fishery water use and for substances belonging to 1 and 2 hazard classes for household and drinking and municipal water use, when several substances with the same LPV enter water bodies and taking into account impurities entering the water body from upstream sources , the condition must be met:

<=1, (4.1)

where C1, C2, C n - concentration of each of the substances in the control section, mg / dm 3;

PDK1, PDK2 ,. MPC n - maximum permissible concentration of the same substances, mg / dm 3.

Note: The control gate is the cross-section of the flow in which the water quality is monitored.

For unique water bodies of ecological, scientific, historical or cultural value, special requirements for water quality may be established. Such water bodies can be given the status of a nature reserve or wildlife sanctuary in the manner prescribed by law.

The highest demands are placed on drinking water. Sanitary standards for water used for drinking and in the food industry determine the organoleptic characteristics of water that are favorable for humans: taste, smell, color, transparency, as well as the harmlessness of its chemical composition and epidemiological safety. The same requirements apply to water from any source of water supply, regardless of the method of its processing and the design of the intake and water supply system. For drinking water, GOST 2874-82 establishes the following standards for organoleptic indicators:

odor at 20 o C and at 60 o C not more than 2 points (weak, not attracting attention, but one that can be noticed);

smack at 20 o С - no more than 2 points;

chromaticity - no more than 20 degrees; turbidity on a standard scale - no more than 1.5 mg / dm 3.

the presence of mineral impurities (mg / dm 3) should not exceed: chlorides (Cl -) - 350; sulfates (SO 2 - 4) - 500; iron (Fe 3+ + Fe 2+) - 0, 3; manganese (Mn 2+) - 0.1; copper (Cu 2+) - 1.0; dry residue-1000;

reaction of the medium pH 6, 5 - 8, 5.

Thus, water is suitable for drinking if its mineralization does not exceed 1000 mg / dm 3. A very low mineralization of water (below 100 mg / dm 3) also impairs its taste, and water, generally devoid of salts (distilled), is harmful to health, since its use disrupts digestion and the activity of the endocrine glands. The question of the good quality of drinking water is solved by determining the number of Escherichia coli in 1 dm 3 of water. E. coli is a microbe that constantly lives in the intestines of humans and animals and, therefore, is harmless. However, its presence in water indicates the presence of human or animal excreta in it and the possibility of water contamination with pathogenic bacteria. According to GOST, 1 dm 3 of drinking water can contain no more than three bacteria of the Escherichia coli group (BGKP). This number is called the coli-index.

The general sanitary indicators of water in reservoirs include: suspended solids (coarse impurities), dry residue, hydrogen index (pH), hardness, content of calcium, magnesium, chlorides, sulfates, ammonium salts, nitrates, nitrites, dissolved oxygen, hydrogen sulfide and some other inorganic and organic matter.

Harmful substances with sanitary and toxicological LPV include inorganic substances: beryllium, arsenic, mercury, thiocyanates, selenium, cyanides, lead, molybdenum, fluorides and others, organic substances: benzene, benz (a) pyrene, aniline, DDT, formaldehyde , methanol, polyacrylamide and others.

The general requirements for the composition and properties of water in water bodies used for drinking and cultural purposes are given in Appendix G, and the MPCs for some harmful substances in the aquatic environment are given in Appendix I.

Protection of water bodies during wastewater discharge

Classificationsewagewaters

In accordance with the "Rules for the Protection of Waters", water returned in an organized manner with the help of technical structures and means from the economic link of the water cycle to natural links (oceans, lakes, rivers, lithosphere) is called return water - this is a generalized name for waste water, waste water discharged into a water body, drainage water.

Waste water is a type of return water; includes household waste water of populated areas, rain (snow) waste water flowing down from built-up areas, industrial waste water.

Waste water - irrigation and irrigation water diverted from irrigated farmland and built-up areas, respectively; a kind of return water.

Drainage water - groundwater discharged from irrigated and drained land areas.

When discharging return (waste) water into water bodies, the standard water quality in the control sections should not be violated.

In accordance with the "Rules for the Protection of Waters", it is prohibited to discharge into water bodies:

return (waste) waters containing substances for which MPC or TAC (indicative permissible levels) are not established, as well as substances for which there are no analytical control methods, with the exception of those substances that are contained in the water of the reservoir;

return (waste) water, which, taking into account their properties and local conditions, can be sent to the recycling water supply systems, for reuse, for irrigation in agriculture, subject to sanitary requirements or for other purposes;

industrial, household waste water, rain and melt water, discharged from the territories of industrial sites and populated areas, which have not been purified to meet the established requirements;

wastewater that has a toxic effect on living organisms (based on the results of biotesting);

return (waste) waters within the sanitary protection zones of sources of domestic and drinking water supply, to water bodies used for medicinal purposes, in places of spawning, artificial breeding of fish and other aquatic organisms, to reserved water bodies;

return (waste) waters containing pathogens of infectious diseases, as well as substances whose concentrations exceed the MPC and their background values in the reservoir, if the maximum permissible discharge (MPD) norms are not established for them, specified in the permit for the discharge of return (waste) waters;

it is prohibited to discharge into water bodies, onto the surface of the ice cover and catchment area, as well as into the sewage system of sediments formed in the course of wastewater treatment, including those containing radionuclides, technological and domestic waste;

no leakage into water bodies from oil and product pipelines, oil fields, as well as the discharge of garbage, untreated sewage, ballast water, as well as the discharge of other substances from floating water vehicles is allowed;

it is not allowed to wash vehicles in the reservoir and on their banks, as well as to carry out any work that may be a source of water pollution.

The discharge of return (waste water) into water bodies is one of the types of special water use and is carried out on the basis of permits issued in the prescribed manner by the State Committee for Ecology in agreement with the State Sanitary and Epidemiological Supervision authorities, and taking into account the requirements of the fisheries industry. 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 water of a water body at a distance from the place of their release to the nearest control point of water use;

the background composition and properties of the reservoir water in the places of wastewater discharge.

Based on the calculation, for each wastewater outlet, maximum permissible discharges (MPD) of substances are established, the observance of which should ensure the standard water quality in the control sections of the reservoir or the non-deterioration of the composition and properties of water formed under the influence of natural factors, the quality of which is worse than the standard.

The MPD is set for each monitored indicator, taking into account the background concentration, category of water use, water quality standards in the reservoir, its assimilating capacity and the optimal distribution of the mass of substances discharged with wastewater between water users. It is advisable to calculate the MPD simultaneously for all water users of the river basin with consideration of the mutual influence of wastewater discharges.

Notes (edit) Assimilative capacity of a water body - the ability of a water body to accept a certain mass of substances per unit of time without violating the water quality standards in the control section of water use;

Background concentration - the concentration of a substance in water, calculated with respect to a given source of impurities in the background section of a water body under calculated hydrological conditions, taking into account the influence of all sources of impurities with the exception of this source;

Background section - the cross-section of the flow, in which the background concentration of substances in the water is determined.

The place of wastewater discharge of a settlement should be located below its border along the river at a distance that excludes the influence of surge phenomena.

Types of pollution and control of wastewater composition

Wastewater is a complex heterogeneous system contaminated with substances that can be in all states - dissolved, colloidal and undissolved. Colloidal and undissolved substances form coarse and finely dispersed suspensions, emulsions, and foam.

Wastewater always contains both organic and inorganic components of pollution.

Organic substances in household waste are in the form of proteins, carbohydrates, fats, products of physiological processing. In addition, domestic wastewater contains large impurities - rags, paper, organic waste, as well as synthetic surfactants (surfactants). Of the inorganic components in this category of effluents, potassium, sodium, calcium, magnesium, chlorine, carbonates, sulfates are always present in the form of ions. Thus, domestic wastewater is characterized by the presence of all the main biogenic elements: C, N, P, S, K.

Household wastewater, in addition, necessarily contains biological pollution, which is represented by bacteria, mainly isolated from the human intestine, helminth eggs, yeast and mold fungi, small algae, viruses, and therefore, these wastewaters pose a significant epidemiological danger to humans, animals, plants, as well as for natural communities in general.

The composition of industrial wastewater is very diverse and individual, depending on the type of products, the type of technological equipment, used raw materials and materials and many other factors.

In the water of domestic drinking and industrial water supply, color, odor, transparency, acidity, alkalinity, dry residue, pH, nitrogen content, oxidizability, biochemical oxygen demand (BOD), the content of dissolved oxygen, chlorides, free chlorine (in the case of wastewater disinfection chlorine), phosphates, fluorides, iron, nitrates, nitrites, hardness and other components. All of these components are also monitored in industrial wastewater. However, they also determine specific components characteristic of specific samples associated with the peculiarities of production, for example, in the wastewater of petrochemical, most machine-building and metallurgical industries, the content of oil products is determined; in production effluents using electrolysis and galvanization - the content of metals, cyanides.

To characterize the composition of wastewater, a large number of different types of analyzes are used - chemical, physicochemical, sanitary and bacteriological, as well as the determination of the organoleptic properties of water using the senses of the researcher.

Difficulties in determining specific impurities in wastewaters of various industries are due to the inconstancy of the composition of the effluents, low concentrations of components, the simultaneous presence of many diverse substances that interfere with and complicate selective determination. To solve this complex problem, modern physicochemical research methods are widely used - photocolorimetry, spectrophotometry, methods of spectral, chromatographic, polarographic analysis.

A systematic analysis of the composition of wastewater discharged by industrial enterprises and public utilities is necessary to check the efficiency of treatment facilities, assess the impact of discharged wastewater on water bodies, develop measures to improve the operation of treatment facilities and to implement additional measures to protect water bodies.

Sewage treatment

The methods used for wastewater treatment can be divided into three groups:

1. Mechanical;

2. Physicochemical;

3. Biological.

To eliminate bacterial contamination of wastewater, they are disinfected (disinfected).

Domestic waste water treatment

Through numerous underground arteries, domestic wastewater flows day and night to the city sewage treatment plant.

Domestic (fecal) wastewater includes wastewater entering the sewerage system from kitchens and toilet rooms, baths, laundries, after washing floors, as well as from household premises of industrial enterprises.

Methods for treating domestic wastewater are divided into mechanical and biological.

A complex multi-stage path of purification and revival of water at treatment facilities begins with a receiving chamber, then various mechanical structures filter it, freeing it from dirt, debris, and harmful impurities. During mechanical treatment of wastewater, their liquid and solid phases are separated. For this purpose, gratings, grate-crushers, sand traps, various sedimentation tanks, etc. are used. Mechanical purification serves as a preliminary stage before biological purification, since, while purifying water, all these grids, sand traps and other mechanisms cannot revive it. This water is dead, there are no salts, no microorganisms, or other necessary components in it.

Water is restored to life by microorganisms, familiar to us from the school textbook of zoology - ciliates, shoes, rotifers, etc., the so-called "activated sludge", which contains all these microorganisms and which is the main mechanism for biological treatment of the liquid part of wastewater. oxidation or reduction of organic substances in the wastewater in the form of thin suspensions, colloids and in solution, and which are a source of nutrition for microorganisms, occurs, as a result of which wastewater is purified from organic contaminants.

Biological treatment facilities can be divided into two types:

Facilities where cleaning takes place under conditions close to natural (natural biological treatment);

Facilities where cleaning takes place under artificially created conditions (artificial biological treatment).

Natural biological wastewater treatment is carried out in filtration fields, irrigation fields, biological ponds, etc. (see Figure D.4).

For artificial biological treatment, special structures are used: aeration tanks, biofilters, air filters. In these structures, the treatment proceeds more intensively than in irrigation fields, filtration fields, and ponds, because better conditions are created artificially for the active vital activity of microorganisms.

Biological filters are structures in which waste water is filtered through a feed material covered with a biofilm formed by colonies of microorganisms. Gravel, expanded clay, slag, coarse sand, crushed stone, as well as gratings, rings, bags made of polymer materials are used as the loading material. Leaking through the biofilter loading, wastewater leaves on it undissolved impurities that have not settled in the primary sedimentation tanks, as well as colloidal and dissolved organic substances adsorbed by the biological film. The biofilm looks like mucous fouling with a thickness of 1 - 3 mm and more. Its color changes with a change in the composition of wastewater from grayish yellow to dark brown. Microorganisms densely populating the biofilm oxidize organic matter and derive energy from here for their vital activity. Part of the organic matter is used by microorganisms to increase their biomass. Thus, organic substances are removed from the waste water and, at the same time, the mass of the active biological film in the body of the biofilter increases. The spent and dead film is washed off by the flowing waste water and taken out of the biofilter body. Air oxygen, necessary for the biochemical process, enters the load through natural and artificial ventilation of the filter.

Aeration tanks are long reinforced concrete reservoirs of rectangular cross-section, in which a mixture of activated sludge and waste water slowly moves. For the normal life of microorganisms, air is continuously supplied to the aerotank, which is not only a source of oxygen, but also maintains the activated sludge in suspension. The water here is black from silt flakes; it boils violently, saturated with oxygen from the blowing station. It seems even dirtier and blacker than it was in the receiving chamber, but it is here, in the aerotanks, that the metamorphosis of revival takes place. Creatures visible only through a microscope, whose vital activity requires oxygen, decompose harmful impurities, eat everything that could not be removed from the water during mechanical cleaning.

After aeration tanks or biofilters, wastewater purified from organic impurities enters secondary sedimentation tanks, which serve to retain activated sludge or biological film that flows along with the wastewater.

In the secondary sedimentation tanks, silt flakes easily settle, clean living water runs into the river, and the sludge is again sent "to work".

The concentration of various substances in wastewater is constantly changing, which complicates the acclimatization of microorganisms. Activated sludge is not capable of decomposing some harmful substances at all, and they pass in transit into the reservoir. And in the case of a salvo discharge into the sewage system of a large amount of toxic impurities, microorganisms may die altogether, and the biological treatment plant will be out of order for several months.

That is why, in order not to ruin biological treatment, not to create emergency situations in the operation of the city sewage system, special standards for the content of harmful substances in wastewater have been developed for industrial enterprises. Specific pollution should be captured at the local treatment facilities of enterprises, and wastewater should be supplied to the city sewage system that meets the above standards.

Due to the fact that the wastewater of any settlement contains pathogenic microbes, it is necessary to disinfect them in all cases of using artificial biological treatment. In the practice of wastewater treatment, disinfection (disinfection) is carried out by the same methods and means as in the purification of natural waters. The most commonly used water chlorination or ozonation. Chlorination of waste liquid is carried out in special contact tanks, arranged as horizontal and vertical settling tanks. The duration of contact of chlorine with liquid is at least 30 minutes. If the waste liquid contains at least 1.5 mg / dm3 of residual active chlorine, then it can be considered disinfected.

During wastewater treatment, sediment is formed due to the precipitation of undissolved substances in the primary sedimentation tanks. In addition, as a result of biological treatment, a large amount of sludge is formed, which is released in the secondary sedimentation tanks. The sediment consists of solids highly diluted with water. In its raw state, during the treatment of domestic wastewater, this sludge has an unpleasant odor and is dangerous from a sanitary point of view, since it contains a huge amount of bacteria, including pathogens. To reduce organic matter in the sludge and give it better sanitary indicators, the sludge is exposed to anaerobic microorganisms (fermentation) and aerobic stabilization of the sludge in the appropriate structures. Anaerobic facilities include two-tier clarifiers - decanters, digesters. Aerobic stabilization can be carried out simultaneously for a mixture of primary settler sludge and surplus activated sludge. The efficiency of the process is determined by its duration, temperature, intensity of aeration, and also depends on the composition and properties of the oxidized sludge. The stabilized sludge is subjected to coagulation, using sulphates of iron, aluminum, iron chloride, lime as coagulants. This process of changing the structure of the sediment and improving its water-releasing properties is called conditioning, which can also be carried out using heat treatment, freezing followed by thawing, and electrocoagulation. The moisture content of the conditioned sludge decreases from 92 - 94 to 70 - 75%, further dehydration of sludge is carried out on sludge plots - plots of land heaped from all sides.

quality water waste treatment

Dehydrated sewage sludge can be used as organic fertilizer if it does not contain heavy metals or other toxic substances.

The general scheme of a domestic wastewater treatment plant is shown in Figure D.5.

Industrial waste water treatment

A significant proportion of the water reserves of industrialized countries are used for technical needs. The main direction in solving the problem of protecting water bodies is the maximum reduction in the amount of industrial wastewater, as well as the maximum reduction of waste, loss of raw materials and finished products discharged with wastewater into the sewage system. Losses can be reduced by improving technological processes and recovering valuable substances that enter the wastewater.

The amount of wastewater discharged into the sewerage system can be reduced by reusing waste water in the same production operations where it was formed or using such water for other technological needs, where it is possible to use water of a lower quality than the water from the main water supply system.

A significant reduction in water consumption is provided by the introduction of a circulating water supply system, when once taken from a reservoir, water is no longer excluded from the system "water supply - sewerage - treatment facilities - industrial water supply". At the same time, of course, water losses from a closed system occur due to evaporation, leaks in various parts of the system and extraction with sediment formed during wastewater treatment, which are replenished by taking fresh water, but recycling water supply allows you to reduce the consumption of fresh water and prevent pollution of reservoirs. At modern oil refineries and metallurgical plants, the turnover of water has been brought to 97%.

Along with the circulating water supply systems of individual enterprises, industrial water systems are being created on the scale of industrial centers and districts. Wastewater is treated at treatment facilities, and then additionally processed at city-wide (district) treatment facilities and again sent to consumers through technical water supply systems. At the same time, on the scale of an industrial hub, the task of introducing a waste-free, closed-circuit technology is being solved, the withdrawal of water from reservoirs is sharply reduced and the discharge of waste water there completely stops.

In industrial plants, as a rule, there are three main types of wastewater that have to be diverted:

industrial, which is water that was spent in the technological process of production or obtained during the extraction of minerals (for example, water from coal mines, mines, stratal water from oil fields, etc.);

household - from sanitary facilities of administrative and production buildings, from cleaning floors in these buildings, as well as from shower facilities located in production shops;

atmospheric - rain and snow melting.

The amount, composition and concentration of wastewater pollution from industrial enterprises depend on many factors: the type of processed raw materials, the technological process of production, the quality of water consumed for production purposes, waste water recycling systems and a number of other factors.

The type of processed raw materials has a significant impact on the composition of industrial effluents; often the components of raw materials are an integral component of wastewater pollution. For example, coal particles are the main pollutant in coal preparation plants; in refineries, such pollutants are oil and oil products; at chemical enterprises - acids, alkalis, etc. In addition, in the same industry at enterprises of the same profile, the amount of wastewater is not the same, and they have a different concentration of pollution. Therefore, for the purification of industrial wastewater, depending on the composition of their contamination, various purification methods are used. They can be roughly subdivided into destructive and regenerative.

Destructive treatment methods are reduced to the destruction of water pollutants by oxidation or reduction. The resulting decomposition products are removed from the water in the form of sediments or gases, or remain in the form of soluble mineral salts. These methods are used for waste water with organic impurities of no technical value, or as a post-treatment after regeneration methods. The main destructive method is the method of biological oxidation under aerobic or anaerobic conditions. Industrial effluents treated by this method meet sanitary - hygienic and fishery standards and can be released into a reservoir or reused for technological needs.

Regenerative methods allow the recovery and disposal of valuable substances in water. Regenerative methods do not always purify water to the point where it can be discharged into water bodies. In these cases, the water is purified by destructive methods.

In all cases of wastewater treatment, the first stage of this process is mechanical treatment, designed to free water from suspended and colloidal particles. The next stage of purification is the removal of chemical compounds dissolved in it from the water by physicochemical, chemical, electrochemical, biological methods. In many cases, combinations of methods are used.

The most commonly used methods are:

to remove coarse particles - filtering, settling, flotation, clarification, centrifugation;

for the removal of fine and colloidal particles - coagulation, flocculation, electrical deposition methods;

for purification from inorganic compounds - distillation, ion exchange, reverse osmosis, reagent precipitation, cooling methods, electrical methods;

for purification from organic compounds - extraction, absorption, flotation, ion exchange, reagent methods, biological oxidation, liquid-phase oxidation, ozonation, chlorination, electrochemical oxidation;

for cleaning from gases and vapors - stripping, heating, reagent methods;

for the destruction of harmful substances - thermal decomposition.

Mechanical wastewater treatment - (filtering, settling, filtration) is used to separate undissolved mineral and organic impurities from wastewater. The advantage of these processes is that they can be used at normal temperatures and without the addition of chemicals. This treatment, as a rule, is a preliminary, less often - the final method of processing industrial wastewater.

The filtering method is used to remove suspended particles larger than 15 - 20 mm. For this purpose, a variety of grids, meshes and sieves are used, which can be mobile or stationary, they are often combined with crushers to crush contaminants.

After filtering, the wastewater goes into sand traps, designed to separate smaller mineral impurities with a relatively high density. When water moves in the tank of the sand trap, suspensions with a grain diameter of more than 0.25 mm settle on its bottom. The sludge is moved with the help of scrapers into a special bunker, from where it is removed to a sand platform for neutralization. Sand traps facilitate the operation of facilities for further wastewater treatment (sedimentation tanks, digesters, etc.) and are installed in circuits that pass at least 100 m 3 of wastewater per day.

The settling method is used to separate smaller organic and mineral suspensions; for these purposes, various types of sedimentation tanks are used. Distinguish between sedimentation tanks of periodic and continuous action. In the direction of water movement, they are divided into horizontal, vertical and radial. In addition, sedimentation tanks are primary, which are installed in front of biological water treatment facilities, and secondary ones - they are used to clarify wastewater that has already passed biological treatment. Sediment ponds can be used as independent treatment facilities if, due to sanitary conditions, it is sufficient to isolate only mechanical pollution from wastewater.

To separate oils, fats, resins, oil and oil products floating on the surface of wastewater, oil catchers, grease traps, and oil traps are used of various designs.

Oil traps are used to treat wastewater containing coarsely dispersed oil and oil products at a concentration of more than 100 mg / dm 3 in wastewater. They are rectangular, elongated reservoirs, in which the separation of these impurities from water is carried out due to the difference in their densities. Oil floats to the surface, it is collected using slotted pipes, and mineral impurities contained in the wastewater settle to the bottom of the oil trap. The water freed from oil enters the discharge manifold and can be returned to production.

Fat removal. Fats and oils, as well as oil products, are not allowed to be released into water bodies, since they, covering large areas of the water surface with a thin film, impede the access of air oxygen and thereby inhibit the self-purification process of the water body. In addition, these pollutants released from wastewater can be used for technical needs. Grease traps, like oil traps, can be installed directly at individual production workshops, the wastewater of which contains a lot of fat or directly on the general drain of greasy water.

The wastewater filtration method is used to isolate finely dispersed substances from them that did not settle during settling (oils, resins, fibers, dust, etc.); in the post-treatment of wastewater after biological or other treatment methods. After the aeration tanks, filters are provided to retain fine particles of activated sludge, which has adsorbed organic pollution of wastewater on its surface. To filter wastewater, filters with mesh elements and filters with a filtering granular layer are used. Perforated metal sheets and meshes made of acid-resistant steel, aluminum, nickel, brass, etc., various fabric partitions - asbestos, glass, cotton, woolen, artificial fiber, ceramic plates are used as mesh elements. Quartz sand, finely ground granite, coke breeze, peat, brown and black coal, etc. are used as a granular filtering layer. The filter material must have the required porosity, sufficient mechanical strength against abrasion and chemical resistance.

Chemical wastewater treatment is used in cases where the release of pollutants from wastewater is possible only as a result of chemical reactions between these pollutants and reagents introduced into the wastewater. In this case, the oxidation and reduction of impurities dissolved in water occurs with the receipt of non-toxic or low-toxic products; conversion to water-insoluble compounds; neutralization of acids and alkalis. The most widely used reagents are: oxidizing agents - chlorine, potassium permanganate, ozone; alkalizing substances - lime, soda; acidifying substances - sulfuric and hydrochloric acids. All chemical cleaning methods require reagent consumption and are therefore expensive. Chemical methods of purification include neutralization, oxidation, ozonation, electrochemical oxidation, etc.

Oxidation of wastewater pollutants is used in cases where these substances are impractical or cannot be removed or destroyed by other means, including by biochemical oxidation. These substances include arsenic compounds, cyanide compounds that pollute the wastewater of many industries, for example, wastewater from plants for enrichment of lead-zinc and copper ores, galvanic coating workshops at machine-building plants.

To purify wastewater from cyanide compounds, the oxidation of cyan - ion (CN -) to harmless cyanate (CNO -) is used or toxic compounds are converted into a non - toxic complex or sludge (in the form of insoluble cyanides), which is removed from the wastewater by settling or filtration.

The oxidation of cyanides to low-toxic cyanates can be performed with a relatively inexpensive oxidizing agent - hypochlorite in an alkaline medium at pH = 10.11. The reagent containing the hypochlorite ion (O Cl -) is bleach, calcium hypochlorite or sodium hypochlorite.

The chlorination process is carried out in chlorinators of periodic or continuous action, pressure or vacuum (Figure I.2). In these installations, wastewater is purified from hydrogen sulfide, hydrosulfides, methylsulfur compounds, phenols, cyanides.

Ozone (O 3) is a very promising oxidant for waste water. Ozonation not only cleans wastewater from phenols, oil products, hydrogen sulfide, arsenic compounds, surfactants, cyanides, carcinogenic aromatic hydrocarbons, pesticides and many other toxic impurities, but also simultaneously discolors and disinfects water and eliminates its odors and tastes. When water is treated with ozone, pathogenic microorganisms die several thousand times faster than when it is chlorinated. Ozone is supplied to waste water in the form of an ozone-air or ozone-oxygen mixture, in which the ozone content usually does not exceed 3%. Ozonation of industrial wastewater is carried out in bubbling, packed, disc columns and other contact devices (Figure D.3).

The cleaning process can be accelerated by the combined application of ozone and ultrasonic treatment or ultraviolet irradiation of wastewater. Thus, ultraviolet irradiation accelerates the oxidation of impurities in industrial wastewater by 10 2 - 10 4 times.

Recovery as a treatment method is used when industrial effluents contain easily recoverable substances. These methods are often used to remove chromium, mercury, and arsenic compounds from wastewater. Chromium (IV) contained in industrial effluents is reduced to Cr 3+, followed by its precipitation in an alkaline medium in the form of hydroxide (Cr (OH) 3.). Activated carbon, organic waste (for example, newsprint), iron sulfate (Fe SO 4), sodium hydrosulfite (Na HSO 3), sulfur dioxide (SO 2), hydrogen are used as reducing agents.

Mercury of inorganic compounds contained in wastewater is relatively easily reduced to metallic mercury, which is then released by settling, filtration or flotation. Iron sulfide (Fe S), sodium hydrosulfite (Na HSO 3), powdered iron, aluminum powder, and hydrogen sulfide are used as reducing agents for trapping mercury. Organic compounds of mercury are first destroyed with the help of strong oxidants, and then its cations are reduced: Hg 2+ to Hg 0.

Wastewater neutralization. Industrial wastewater from many industries contains acids and alkalis. The intensity of an acidic or alkaline reaction is determined by the pH value. To prevent corrosion of materials of sewage structures and disruption of biochemical processes occurring in treatment facilities and in water bodies, such waters are neutralized. Neutralization is often also carried out in order to precipitate heavy metal salts from wastewater.

In all cases, the possibility of mutual neutralization of acids and alkalis discharged with wastewater is taken into account. A mixture with a pH value in the range of 6, 5 - 8, 5 is considered to be practically neutral, therefore wastewater, the pH of which is below 6.5 or above 8.5, must be neutralized before being released into the reservoir.

The neutralization process is carried out in flow-through or contact neutralizers, which can be structurally combined with sedimentation tanks. Under favorable local conditions, the clarification of neutralized waste water can be carried out in sludge collectors in the open air. To neutralize acidic wastewater, use any alkaline reagent that gives OH - ions in solution; most often used are caustic, carbonic and bicarbonate alkalis. The cheapest reagents are Ca (OH) 2 (in the form of fluff or milk of lime), as well as calcium or magnesium carbonates (in the form of crushed chalk, limestone and dolomite). Sodium hydroxide and soda are used only when these reagents are local waste.

When neutralizing, for example, hydrochloric acid wastewater from pickling shops with milk of lime, the following reactions occur:

4 H Cl + Ca (OH) 2 + Ca CO 3 2 Ca Cl 2 + CO 2 + 3 H 2 O 2 Fe Cl 2 + Ca (OH) 2 + Ca CO 3 Fe (OH) 2 + Fe CO 3 + 2 Ca Cl 2

As a result of neutralization, only iron precipitates in the form of nitrous oxide or carbonate hydrate. The rest of the neutralization products remain in the solution, increasing the salt content of the neutralized effluents. The schematic diagram of the neutralization plant is shown in Figure 4.1. The main structures include: tanks - acid and alkaline waste equalizers 1; reaction chambers - neutralizers 6; sedimentation tanks for neutralized wastewater or storage tanks 7, which are both sedimentation tanks and a tank for sludge; facilities for sludge dewatering 8; reagent facilities (5 dispensers; 4 mortar tanks, 2 lime slaking devices, 3 quicklime storage).

The use of quicklime for neutralization is provided in the form of lime milk of 5% concentration of active calcium oxide. Dosing of lime is carried out by an automatic dispenser, depending on the flow rate or pH value of the treated waste water. Clarified water after settling tanks can be used in recycling water supply systems. Sediments (sludge) released in the sedimentation tanks are dewatered at sludge sites - sludge collectors.

Physicochemical methods of wastewater treatment are used to purify industrial wastewater from finely dispersed suspensions that are not captured by filtration, soluble gases, inorganic and organic compounds. These methods are based on the use of a number of processes: coagulation, sorption, extraction, flotation, crystallization, dialysis, deactivation, desalination, etc. and allow you to remove toxic, biochemically non-oxidizable organic compounds from wastewater and achieve a deep and stable level of purification. Physicochemical methods make it possible to fully automate the purification process, and the modern level of knowledge in the field of kinetics of many physicochemical processes creates the basis for their mathematical modeling and optimization, which makes it possible to correctly select and calculate the parameters of the equipment. In most cases, the use of physicochemical methods for the separation of pollutants from wastewater allows them to be recovered in the future.

Coagulation is the process of enlarging dispersed particles and combining them into aggregates under the influence of chemical and physical processes that spontaneously occur in a solution, or under the influence of special substances introduced into the solution - coagulants. Salts of iron, aluminum, silicic acid, polyacrylamide are used as coagulants for wastewater treatment. In addition, for the coagulation of wastewater impurities, substances with high adsorption properties are used: clay, ash and slag, activated carbon, etc. The coagulation method is widely used to purify wastewater from textile enterprises, artificial fiber plants, oil refineries and chemical plants.

The process of aggregation of suspended particles when high molecular weight compounds are added to wastewater is called flocculation. Flocculation is carried out to intensify the formation of flakes of iron and aluminum hydroxides and to increase the rate of their precipitation. The use of flocculants allows you to reduce the dose of coagulants and, at the same time, accelerate the process of clarifying wastewater.

Extraction is the process of separating dissolved organic impurities, for example, phenols, fatty acids, oils in wastewater, by treating the latter with some kind of water-immiscible solvent - an extractant, in which impurities that pollute water dissolve better than in water ... For example, the amount of dissolved phenol in butyl acetate is 12 times that of water. Organic solvents insoluble in water are used as extractants for wastewater treatment: benzene and some of its derivatives, carbon disulfide, carbon tetrachloride, mineral oils. A good esthetic agent must meet a number of requirements:

dissolve the extracted substance much better than water, i.e. have a high distribution ratio;

have good selectivity (selectivity) in relation to the recoverable impurities;

have low solubility in waste water and do not form stable emulsions with it;

differ significantly from waste water in terms of density, since a significant difference in density ensures fast and complete phase separation;

regenerate in a simple and cheap way;

do not interact with the extracted substance, as this can complicate the regeneration of the extractant and increase its losses;

as far as possible not to be toxic, explosive or corrosive to the material of the device.

The feasibility of using extraction for wastewater treatment is determined by the value of the extracted substances and their concentration. For each substance, there is a "concentration limit" of the profitability of its extraction. The process is considered economically profitable if the cost of the extracted substances compensates for all the costs of its implementation. It is generally accepted that at a concentration higher than 3 - 4 g / dm 3, it is advisable to extract impurities by extraction.

Flotation is the separation of impurities from wastewater by making them buoyant due to a flotation reagent that envelops the particles of impurities and is removed from the water along with it. In flotation purification, waste water is saturated with finely dispersed air bubbles. Particles contained in waste water (emulsified oil, cellulose and paper fiber, wool, etc.) adhere to air bubbles and float with them to the surface of the water, and then are removed from the water. To enhance the flotation effect, surfactants (surfactants) are added to the water, which lower the surface tension of the liquid and weaken the bond of water with the floating substance, as well as foaming agents that increase the dispersion of air bubbles and their stability. Flotation processes run continuously, have a high selectivity for the separation of impurities at a high rate of the process, do not require complex and expensive equipment, the degree of purification reaches 95 - 98%.

Sorption is used to separate organic substances and gases (phenols, pesticides, aromatic nitro compounds, surfactants, dyes, etc.) from wastewater dissolved in them by concentrating them on the surface of a solid (adsorption), or by absorbing a substance from a solution or mixture of gases by liquids (absorption), or by chemical interaction of solutes with a solid (chemisorption).

The efficiency of processes, for example, adsorption, depends on the chemical nature of the adsorbent, the size of the adsorbing surface, as well as on the structure and properties of the trapped impurities. Peat, sawdust, slags and other low-value substances are used as adsorbents, which are usually removed or burned after a single use. If the pollutant or adsorbent is of a certain value, then the adsorbent is regenerated by extracting the absorbed substance from it. The most effective, but also the most expensive sorbent used in water purification schemes is activated carbon.

Ion exchange treatment is used to extract metals (zinc, copper, chromium, nickel, lead, mercury, cadmium, vanadium, manganese) from waste water, as well as compounds of arsenic, phosphorus, cyanides. This method of purification allows not only to clean the effluent from toxic elements, but also to capture a number of valuable chemical compounds for reuse. Natural mineral compounds are used as ion exchangers, such as zeolites, clay minerals, fluorapatite F 2, hydroxylapatite, organic compounds - humic acids of soils and coals; synthetic ion exchangers are also used: inorganic (silica gels and sparingly soluble oxides and hydroxides of aluminum, chromium, zirconium) and organic (mainly organic resins). The most widely used are ion exchange resins - high molecular weight compounds. The ion exchangers do not dissolve in water, but they swell, and the sizes of their micropores increase from 0.5 - 1.0 nm to 4 nm, and the volume of the ion exchanger increases 1.5 - 3 times. Swelling affects the selectivity of the ion exchanger, since with a small pore size, large ions cannot reach internal functional groups.

The process of ion-exchange wastewater treatment is carried out in installations of periodic (Figure I.1) and continuous operation.

Industrial effluents that cannot be treated by the methods described above, or if these methods are not applicable for technical and economic indicators, are subjected to evaporation, incineration or injection into deep reservoir formations.

Literature

1. Vernadsky V.I. Living Substance and the Biosphere. - M .: Nauka, 1994 .-- 670 p.

2. Lozanovskaya I.N., Orlov D.S., Sadovnikova L.K. Ecology and protection of the biosphere in case of chemical pollution: Textbook. pos .: M: Higher. shk., 1998 .-- 287 p.

3. Odum Y. Fundamentals of ecology. M .: Mir, 1975 .-- 740 p.

4. Radkevich V.A. Ecology: Textbook. - M .: Higher. shk., 1997 .-- 159 p.

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Natural gases are emitted according to the conditions of being in the environment, according to their chemical composition, forms of manifestation (foci, accumulations), according to their origin (biochemical, radioactive, space). In chi

Biological resources and food security
Biological resources include plants, animals and microorganisms. The main task of the protection and rational use of biotic resources is their conservation and

Protection of Nature. Rational use of natural resources. Low-waste and zero-waste technologies
Nature protection is understood as a set of measures that ensure the possibility of preserving the natural resource and nature-reproducing functions, the gene pool, as well as preserving

The traditional energy industry, which uses fossil fuels (oil, coal), is one of the main sources of environmental pollution and a consumer of non-renewable nature.

Urbanization problem
The Latin word "Urbs" - city - has been known for a long time. But the terms "urbanism" and "urbanization" appeared relatively recently. Urbanization is a process of population migration to a resident

Principles and methods of environmental protection
Basic principles. Each state, while exercising the right to pursue the policies it needs with respect to the national environmental system, must comply with the general

Protected areas as a form of environmental protection
To preserve the biological diversity of the state, there is a need for further development of specially protected natural areas of the Republic of Kazakhstan (hereinafter - SPNA). According to

Protection of genetic diversity. Biosphere reserves. The Red Book and its Role in Biodiversity Conservation
Nature has constructed in the process of evolution an innumerable variety of life forms. One of the priority tasks of nature conservation is the preservation of this biological diversity. Under

The processes of destabilization of the natural environment of the Republic of Kazakhstan, causes and consequences
Kazakhstan, being a participant in world processes and phenomena, also strives to achieve sustainable development and makes considerable efforts to this: from the identification of processes destabilizing the natural environment

Methods and criteria for assessing the state of the environment
Criteria for assessing the state of the environment are divided into direct and indirect, partial and integral, or form a system of criteria. Direct criteria reflect direct impact

Environmental monitoring, principles of its organization
Environmental monitoring is called regular observation of natural environments, natural resources, flora and fauna, carried out according to a given program, allowing

Legislation of the Republic of Kazakhstan in the field of environmental protection
Environmental law is a branch of law, the norms of which regulate social relations in the field of interaction between society and nature, that is, relations associated with the use and

The concept of maximum permissible emissions
To assess the quality of atmospheric air and for the purpose of state regulation of emissions of harmful (polluting) substances into the atmospheric air, specific emission standards are established

How the cyclone works
Cyclones of various types are widely used for dry cleaning of gases (Figure 3.1). The gas flow is introduced into the cyclone through the nozzle 2 tangentially from the inner surface

Radial dust collector
In radial dust collectors (Figure 3.4), the separation of solid particles from the gas flow occurs due to the combined action of gravitational and inertial forces. The latter arise

Rotary dust collector
Rotary dust collectors (Figure 3.2) refer to centrifugal apparatus and are a machine that, simultaneously with the movement of air, cleans it from

Wet methods for cleaning dust and gas emissions
Wet dust collectors. Devices for wet cleaning of gases are widespread, since they are characterized by a high efficiency of cleaning from fine dust with a diameter of

The principle of operation of the Venturi scrubber
Among wet cleaning devices with dust deposition on the surface of droplets, Venturi scrubbers have found the greatest practical application (Figure 3.8). The main part of the scrubber is the Be nozzle

Nozzle scubber
Nozzle scrubbers are a type of apparatus for collecting dust by settling particles on liquid droplets (Figure 3.9a). The dusty gas stream enters the scrubber according to p

The principle of operation of the bubble-foam dust collector
Wet dust collectors include bubble-foam dust collectors with failure and overflow grates (Figure 3.10). In such devices, the gas for cleaning enters the grate 3, pass

There are several types of water pollution: - microbial - the entry of pathogenic microorganisms into water bodies; - thermal - heat entering the water bodies together

The principle of operation of the sump
The sedimentation tanks are vertical, radial and horizontal. The vertical settler is a cylindrical or square tank with a conical bottom. Waste water is supplied through the central

The principle of the clarifier
Figure 3.15 shows a schematic diagram of the clarifier. Water with a coagulant is fed to the bottom of the clarifier. The coagulant flakes and suspended particles entrained by it rise rise

How filters work
Filtration is used to separate finely dispersed impurities from wastewater, the removal of which is difficult by settling. The separation is carried out using porous partitions, p

Wastewater treatment by coagulation
Coagulation is the process of coarsening of dispersed particles as a result of their interaction and aggregation. This method is used to accelerate the deposition of finely

Biological cleaning methods
Biological methods are used to purify household and industrial wastewater from a variety of dissolved organic and some inorganic (hydrogen sulfide, ammonia, etc.)

Aerobic wastewater treatment methods. The principle of operation of aeration tank, filtration fields and irrigation fields.
The aerobic method is based on the use of aerobic microorganisms, whose vital activity requires a constant supply of oxygen and a temperature within 20 ... 40 0

Anaerobic Wastewater Treatment Principle of Digestion Tank Operation
The anaerobic cleaning method takes place without air access. It is mainly used to neutralize solid sediments that are formed during mechanical, physical and chemical

The concept of soil and soil-forming factors
Underground resources are understood as lands that are systematically used or suitable for use for specific economic purposes. Of particular importance to humans is

Soil erosion
One of the types of negative impact on the soil is its erosion.

Desertification of the soil
Desertification is a process that leads to the loss of a continuous vegetation cover by the natural ecosystem with the further impossibility of its restoration without human participation. Origin

Waterlogging of the soil
Swamping is a hydrogenic succession of natural landscapes as a result of natural and anthropogenic factors. Occurs due to the rise of ground and surface waters, abundant in

Soil salinization
Soil salinization is also caused by natural (primary salinization) and anthropogenic (secondary salinization) factors. It may be due to soil salinity, pr

Methods and means of protection against noise
Noise is a disorderly combination of sounds of varying frequency and intensity. Sound is the vibrational motion of particles of an elastic medium, propagating in

Methods of protection against non-ionizing electromagnetic radiation
Sources of electromagnetic radiation are natural and artificial. The magnetic field of the Earth is natural. It is characterized by tense