The technological cycle of one of the enterprises requires the consumption of significant amounts of water. The source is a river located near the enterprise. After passing the technological cycle, the water is almost completely returned to the river in the form of wastewater from an industrial enterprise. Depending on the profile of the enterprise, wastewater may contain a variety of chemical components that are harmful in terms of sanitary and toxicological characteristics. Their concentration, as a rule, is many times higher than the concentration of these components in the river. At some distance from the place of wastewater discharge, the water of the river is taken for the needs of local water use of a very different nature (for example, domestic, agricultural). In the task, it is necessary to calculate the concentration of the most harmful component after diluting the wastewater of the enterprise with water from the river at the place of water use and trace the change in this concentration along the fairway of the river. And also to determine the maximum allowable runoff (MPD) for a given component in the runoff.

Characteristics of the river: flow velocity - V, average depth at the site - H, distance to the place of water use - L, water flow rate at the water intake point - Q, step with which it is necessary to trace the change in the concentration of the toxic component along the river fairway - LS. Characteristics of the runoff: harmful component, water consumption by the enterprise (volume of waste water) - q, concentration of the harmful component - C, maximum allowable concentration - MPC.

Method of calculation

Many factors: the condition of the river, banks and wastewater affect the speed of movement of water masses and determine the distance from the place of wastewater discharge (SW) to the point of complete mixing. The release of wastewater into reservoirs should, as a rule, be carried out in such a way that it is possible to completely mix the wastewater with the water of the reservoir at the place of their discharge (special releases, regimes, designs). However, one has to take into account the fact that mixing will be incomplete at some distance below the SW descent. In this regard, the real dilution factor in the general case should be determined by the formula:

where γ is the coefficient, the degree of dilution of wastewater in the reservoir.

It is customary to evaluate the conditions for the discharge of wastewater into a reservoir, taking into account their influence at the nearest water use point, where the dilution ratio should be determined. The calculation is carried out according to the formulas:

where α is a coefficient taking into account hydrological mixing factors. L - distance to the place of water intake.

where ε is a coefficient depending on the place of water flow into the river: when released near the shore ε=1, when released into the core of the river (the place of the highest speeds) ε=1.5; Lf/L pr - coefficient of river meandering, equal to the ratio of the distance along the fairway of the full length of the channel from the outlet of the NE to the place of the nearest water intake to the distance between these two points in a straight line; D - coefficient of turbulent diffusion,

where V is the average flow velocity, m/s; H - average depth, m; g - free fall acceleration, m/s 2 ; m is the Bussinsky coefficient, equal to 24; c is the Shezi coefficient, which is chosen from the tables. However, in this problem it is assumed that the rivers under study are flat, so the approximation

The actual concentration of the harmful component in the reservoir at the nearest water intake is calculated by the formula:

This value should not exceed MPC (maximum permissible concentration).

It is also necessary to determine how much pollutants can be discharged by the enterprise in order not to exceed the standards. Calculations are carried out only for conservative substances, the concentration of which in water changes only by dilution, according to the sanitary-toxicological indicator of harmfulness. The calculation is carried out according to the formula:

where C st.pred. - the maximum (limiting) concentration that can be allowed in the wastewater or the level of wastewater treatment at which, after mixing with water at the first (calculated) water use point, the degree of pollution does not exceed the MPC.

The maximum allowable flow is calculated by the formula:

As a result of calculations, the following characteristics of the SW should be obtained

Dilution factor K;

Concentration at the place of water intake - Sv, mg/l;

Maximum concentration in the runoff - С st.pred. , mg/l;

Maximum allowable flow - MPD, mg / s;

Graph of the function F=C(L).

Table 3.1

Options for completing the task

The technological cycle of one of industrial enterprises The Moscow region requires the consumption of significant amounts of water. The source is a river located near the enterprise. After passing the technological cycle, the water is almost completely returned to the river in the form of wastewater from an industrial enterprise. Depending on the profile of the enterprise, wastewater may contain a variety of chemical components that are harmful in terms of sanitary and toxicological characteristics. Their concentration, as a rule, is many times higher than the concentration of these components in the river. At some distance from the place of wastewater discharge, the water of the river is taken for the needs of local water use of a very different nature (for example, domestic, agricultural). In the task, it is necessary to calculate the concentration of the most harmful component after diluting the wastewater of the enterprise with water from the river at the place of water use and trace the change in this concentration along the fairway of the river. And also to determine the maximum allowable runoff (MPD) for a given component in the runoff.

Characteristics of the river: flow rate - V, average depth in the area - H, distance to the place of water use - L, water flow in the river - Q1; the step with which it is necessary to trace the change in the concentration of the toxic component along the fairway of the river - LS.

Runoff characteristics: harmful component, water consumption -Q2, concentration of the harmful component - C, background concentration -Cf, maximum allowable concentration - MPC.

Options for calculating the characteristics of wastewater discharges from enterprises into water bodies:

ε=1; Lf/Lpr=1

SOLUTION:

Many factors: the state of the river, banks and wastewater affect the speed of movement of water masses and determine the distance from the place of wastewater discharge (SW) to the point of complete mixing.

where γ -coefficient, the degree of completeness of wastewater in the reservoir.

It is customary to evaluate the conditions for the discharge of wastewater into a reservoir, taking into account their influence at the nearest water use point, where the dilution ratio should be determined.

The calculation is carried out according to the formulas:

where is a coefficient that takes into account hydrological mixing factors.

L is the distance to the water intake.

where is a coefficient depending on the place where the runoff is released into the river. =1, when released near the shore.

Lf/Lpr is the coefficient of river sinuosity, equal to the ratio of the distance along the fairway of the full length of the channel from the outlet of the NE to the place of the nearest water intake to the distance between these two points in a straight line.

Based on the fact that in this problem it is assumed that the rivers under study are flat, we find the D-coefficient of turbulent diffusion,

where V is the average flow velocity, m/s;

H-average depth, m

Knowing D, we find:

0.26 > 0.01, this means that this value exceeds the MPC

It is also necessary to determine how many pollutants
substances can be dumped by the enterprise so as not to exceed the standards. Calculations are carried out only for conservative substances according to the sanitary-toxicological indicator of harmfulness. The calculation is carried out according to
formula:

Conclusions: Having solved this problem, we got the real concentration of the harmful component in the reservoir at the nearest water intake, Св = 0.26, it turned out to be more than the maximum permissible concentration of harmful substances in the reservoir, which means that the reservoir is very heavily polluted and requires immediate cleaning, and an enterprise discharging its wastewater into it must be checked for sanitary standards.

Answers on questions:

The main cause of pollution of water basins is the discharge of untreated or insufficiently treated wastewater into water bodies by industrial enterprises, utilities and agriculture. Residues of fertilizers and pesticides washed out of the soil also enter water bodies and pollute them. For neutralization, even after thorough biological treatment, these waters must be diluted with clean water. Dilution rates are sometimes very high. So, for the production of synthetic fibers, the dilution ratio is 1:185, for polyethylene or polystyrene - 1:29. Worldwide, 5,500 km 3 of clean water is spent annually on the disposal of wastewater - three times more than on all other needs of mankind. This value is already 30% of the sustainable flow of all rivers in the world. Consequently, the main threat of water shortages is generated not by irretrievable industrial consumption, but by pollution. natural waters industrial effluents and the need for their dilution. Pollution entering wastewater can be conditionally divided into several groups. So, according to the physical state, insoluble, colloidal and dissolved impurities are distinguished. In addition, pollution is divided into mineral, organic, bacterial and biological. Mineral pollution is usually represented by sand, clay particles , particles of ore, slag, mineral salts, solutions of acids, alkalis and other substances. these are physiological excretions of people and animals, remains of animal tissues, adhesive substances, etc. Bacterial and biological pollution is characteristic mainly of domestic wastewater and the effluents of some industrial enterprises. production, biofactories, enterprises of the microbiological industry, etc. Household wastewater includes water from kitchens, toilets, showers, baths, laundries, canteens, hospitals, household water that is formed during washing of premises, etc. They come from residential and public buildings , from household premises industrial enterprises, etc. In domestic wastewater organic matter in pollution is 58%, minerals - 42% (Table 1).

Threat of infectious diseases.

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CALCULATION OF THE CHARACTERISTICS OF WASTEWATER DISCHARGESENTERPRISES IN WATER

The technological cycle of one of the industrial enterprises of the Moscow region requires the consumption of significant amounts of water. The source is a river located near the enterprise. After passing the technological cycle, the water is almost completely returned to the river in the form of wastewater from an industrial enterprise. Depending on the profile of the enterprise, wastewater may contain a variety of chemical components that are harmful in terms of sanitary and toxicological characteristics. Their concentration, as a rule, is many times higher than the concentration of these components in the river. At some distance from the place of wastewater discharge, the water of the river is taken for the needs of local water use of a very different nature (for example, domestic, agricultural). In the task, it is necessary to calculate the concentration of the most harmful component after diluting the wastewater of the enterprise with water from the river at the place of water use and trace the change in this concentration along the fairway of the river. And also to determine the maximum allowable runoff (MPD) for a given component in the runoff.

Characteristics of the river: flow rate - V, average depth in the area - H, distance to the place of water use - L, water flow in the river - Q1; the step with which it is necessary to trace the change in the concentration of the toxic component along the fairway of the river - LS.

Runoff characteristics: harmful component, water flow rate -Q2, concentration of harmful component - C, background concentration -Cf, maximum allowable concentration - MPC.

Options for calculating the characteristics of wastewater discharges from enterprises into water bodies:

one; Lf/Lpr=1

SOLUTION:

Many factors: the state of the river, banks and wastewater affect the speed of movement of water masses and determine the distance from the place of wastewater discharge (SW) to the point of complete mixing.

where? is the coefficient, the degree of completeness of wastewater in the reservoir.

It is customary to evaluate the conditions for the discharge of wastewater into a reservoir, taking into account their influence at the nearest water use point, where the dilution ratio should be determined.

The calculation is carried out according to the formulas:

where is a coefficient that takes into account hydrological mixing factors.

L is the distance to the water intake.

where is a coefficient depending on the place where the runoff is released into the river. =1, when released near the shore.

Lf/Lpr is the coefficient of river sinuosity, equal to the ratio of the distance along the fairway of the full length of the channel from the outlet of the NE to the place of the nearest water intake to the distance between these two points in a straight line.

Based on the fact that in this problem it is assumed that the rivers under study are flat, we find the D-coefficient of turbulent diffusion,

where V is the average flow velocity, m/s;

H-average depth, m

Knowing D, we find:

So, the real dilution factor is:

The actual concentration of the harmful component in the reservoir at the nearest water intake is calculated by the formula:

0.2 > 0.01, this means that this value exceeds the MPC

It is also necessary to determine how much pollutants can be discharged by the enterprise in order not to exceed the standards. Calculations are carried out only for conservative substances according to the sanitary-toxicological indicator of harmfulness. The calculation is carried out according to the formula:

From senior chairman \u003d K (MPC - C f) + MPC \u003d 2.428 (0.01-0.001) + 0.01 \u003d 0.032 mg / l \u003d 0.000032 mg / m 3

where C st.pred. - the maximum (limiting) concentration that can be allowed in the wastewater, or the level of wastewater treatment at which, after mixing with water in the reservoir at the first (calculated) point of water use, the degree of pollution does not exceed the MPC.

The maximum permissible flow of MPD is calculated by the formula:

PDS \u003d C st. before Q2 = 0.000032 0.7 = 2.24 10 - 5 mg/s

Let us construct a graph of the distribution function of the concentration of a harmful component depending on the distance to the place of WW discharge along the river bed with a step LS = 15 m, Сv =f(L):

Conclusions: Having solved this problem, we got the real concentration of the harmful component in the reservoir at the nearest water intake, Св = 0.2, it turned out to be more than the maximum permissible concentration of harmful substances in the reservoir, which means that the reservoir is very heavily polluted and requires immediate cleaning, and an enterprise discharging its wastewater into it must be checked for sanitary standards.

Answers on questions:

1. Wastewater collection and treatment

The source of pollution of the hydrosphere in the production of communication equipment is mainly wastewater with mechanical and chemical harmful impurities. Straining, sedimentation, separation of mechanical particles in the field of action of centrifugal forces and filtration can be used to purify wastewater from mechanical impurities. Straining is used to isolate large insoluble impurities and fine fibrous impurities from wastewater, preventing normal operation treatment equipment for wastewater treatment. Settling is based on the properties of particle settling in liquid and is designed to separate insoluble and partially colloidal mechanical contaminants from wastewater. Radial settling tanks have high productivity, the principle of operation of which is quite simple. The separation of mechanical impurities in the field of action of centrifugal forces is carried out in hydrocyclones and centrifuges. Wastewater filtration is used when it is necessary to clean it from fine mechanical impurities.

When wastewater is contaminated with oil-containing impurities, in addition to sedimentation, treatment in hydrocyclones and filtration, the flotation process is also used. Water purification by flotation consists in intensifying the process of oil products floating when their particles are enveloped by air bubbles supplied to the waste water. Depending on the method of formation of air bubbles, several types of flotation are distinguished: pressure pneumatic, foam, chemical, etc. Contaminated wastewater through the pipe of the pressure flotation unit enters the reserve, from where it is pumped to the saturator. The saturator mixes water with incoming air. From the saturator, the mixture enters the flotation chamber through nozzles. Elements “oil impurity - air particles” floating up in the chamber are removed by a foam collector, and purified water flows out through the outlet pipe.

Reagent, ion-exchange, sorption, electrochemical methods, biochemical treatment are used to treat wastewater from metals and their salts, and chemical neutralization methods are used to remove acid-base inclusions.

2. Sources of water pollution

The source of pollution of the hydrosphere during the operation of communication enterprises can be industrial, domestic and atmospheric wastewater discharged into the sewer network. Water is widely used for cooling various elements of radio equipment and household services for workers. Atmospheric waste waters are formed as a result of washing away by rain, snow and irrigation waters of pollution present on the territory of communication facilities, roofs and walls of buildings. Therefore, it is necessary to prevent pollution of sewage with harmful impurities. So, at communication enterprises, stationary batteries (acid, alkaline) are widely used as sources of guaranteed DC power for devices and devices, automatic start-up of diesel generators. During the operation of rechargeable batteries, periodic replacement of the electrolyte is inevitable. According to existing regulations, in order to prevent pollution environment the replaced electrolyte must not be drained into the sewer, but into special vessels for its subsequent disposal.

3. Wastewater discharge conditions industrial enterprises in reservoirs

Water bodies are polluted mainly as a result of the discharge of wastewater from industrial enterprises and settlements. As a result of the discharge of wastewater, the physical properties of water change (temperature rises, transparency decreases, color, tastes, odors appear); floating substances appear on the surface of the reservoir, and sediment forms at the bottom; changes chemical composition water (the content of organic and inorganic substances increases, toxic substances appear, the oxygen content decreases, the active reaction of the environment changes, etc.); the qualitative and quantitative bacterial composition changes, pathogenic bacteria appear. Polluted reservoirs become unsuitable for drinking, and often for technical water supply; lose their fishery importance, etc.

The general conditions for the release of wastewater of any category into surface water bodies are determined by their national economic significance and the nature of water use. After the release of wastewater, some deterioration in the quality of water in reservoirs is allowed, however, this should not noticeably affect his life and the possibility of further use of the reservoir as a source of water supply, for cultural and sports events, and fisheries.

Supervision over the fulfillment of the conditions for the discharge of industrial wastewater into water bodies is carried out by sanitary and epidemiological stations and basin departments.

The water quality standards for reservoirs for domestic and domestic water use establish the quality of water for reservoirs for two types of water use: the first type includes sections of reservoirs used as a source for centralized or non-centralized domestic and drinking water supply, as well as for water supply to enterprises Food Industry; to the second type - sections of reservoirs used for swimming, sports and recreation of the population, as well as those located within the boundaries of settlements.

The assignment of water bodies to one or another type of water use is carried out by the bodies of the State Sanitary Supervision, taking into account the prospects for the use of water bodies.

The water quality standards for water bodies given in the rules apply to sites located on flowing water bodies 1 km upstream of the nearest water use point, and on stagnant water bodies and reservoirs 1 km on both sides of the water use point.

Much attention is paid to the prevention and elimination of pollution of the coastal areas of the seas. Sea water quality standards, which must be ensured when discharging wastewater, refer to the water use area within the allotted boundaries and to sites at a distance of 300 m away from these boundaries. When using coastal areas of the seas as a receiver of industrial wastewater, the content of harmful substances in the sea should not exceed the MPC established for sanitary-toxicological, general sanitary and organoleptic limiting indicators of harmfulness. At the same time, the requirements for the discharge of wastewater are differentiated in relation to the nature of water use. The sea is considered not as a source of water supply, but as a medical, health-improving, cultural and household factor.

Pollutants entering rivers, lakes, reservoirs and seas make significant changes to the established regime and disrupt the equilibrium state of aquatic ecological systems. As a result of the processes of transformation of substances polluting water bodies, occurring under the influence of natural factors, in water sources there is a complete or partial restoration of their original properties. In this case, secondary decomposition products of pollution can be formed that have a negative impact on water quality.

Self-purification of water in reservoirs is a set of interrelated hydrodynamic, physicochemical, microbiological and hydrobiological processes leading to the restoration of the original state of a water body.

CALCULATION OF POLLUTANT EMISSION CHARACTERISTICS

SUBSTANCES TO THE ATMOSPHERE

The industrial enterprise is located in one of the regions of Russia, which is characterized by an investment coefficient - BUT, which determines the conditions for horizontal and vertical dispersion of impurities in the atmosphere. The terrain is characterized by slopes that determine the addition to the relief - r. The average outdoor temperature at 1 pm of the hottest month is TV. The temperature of the emissions of the gas-air mixture - Tg. The difference between these temperatures is ? T. Every second emission of gas-air mixture - VG. The most dangerous component (phenol) in the emitted gas-air mixture has a concentration at the mouth of the pipe - St. For this component, the average daily maximum permissible concentration is determined - Spdk. F- characterizes the settling rate of a given component of the gas-air mixture. In this problem, we should limit ourselves to average daily averaging. At the same time, the elongation index of the wind rose R/Ro= 2, and the averaging coefficient ? = 0.5. Pipe diameter at the mouth - D.

The task consists of two parts.

The first part needs:

Determine the maximum concentration of a given component in the surface layer Cm and compare it with the maximum allowable FROM.

Determine distance HM from the source of the release to the point where the maximum concentration is most likely to occur.

3. Formulate conclusions.

In the second part you need:

Construct a graph of the most probable distribution of the concentration of a harmful component depending on the distance to the source.

Determine the size of the sanitary protection zone around the industrial enterprise.

Determine the MAXIMUM PERMISSIBLE EMISSION (MAL).

Options for calculating emissions of pollutants into the atmosphere:

SOLUTION:

Preliminary assessment of the characteristics of emissions of the gas-air mixture into the atmosphere

The conditions for meteorological dispersion of the gas-air mixture emitted by the enterprise into the atmosphere largely depend on whether the emissions are "cold" or "hot". The criterion for "hotness" of emissions is an auxiliary factor

where? 0 - average speed of exit of the mixture from the mouth of the pipe, m/s,

Let's find f:

f > 100, means emissions into the atmosphere are "cold"

PartI

1. Meteorological dilution factor:

The coefficient n is determined depending on the auxiliary parameter V m:

V m<0.3, значит n=3

The coefficient k is calculated by the formula:

Let us determine the maximum concentration of the harmful component in the surface layer

3. When calculating the dispersion of gaseous components, the distance Xm at F<2 определяется по формуле:

where d=11.4, because Vm<2: X m = 11.4 · 60 = 684

1. Plotting the most probable distribution of the concentration of a harmful component depending on the distance to the emission source.

Let us preliminarily calculate the dimensionless coefficient S, which depends on the X/Xm ratio and is determined by the formulas:

a) if X/X m =0.2; 0.4; 0.8, then

S=3(X/Xm) 4 -8(X/Xm) 3 +6(X/Xm) 2 =3

Then Cx is determined by the formula:

For the first part:

1. Meteorological dilution factor - Cr.

2. The maximum concentration of a harmful substance in the surface layer - See

3. The distance at which the concentration of Sm is most likely - Xm.

For the second part:

Maximum allowable emission - MPE.

Maximum concentration at the mouth of the pipe - See t. " f

Graph of the function Cx \u003d F (X).

Variants for the calculation of emissions of pollutants into the atmosphere

TEST QUESTIONS

Purification of emissions into the atmosphere from impurities.

Sources of pollution and pollution control strategy;

Acid precipitation.

The greenhouse effect.

6. Violation of the ozone layer.

CALCULATION OF THE PERMISSIBLE STAY OF A PERSONUNDER THE INFLUENCE OF SOLAR RADIATION(UV RANGE)DEPENDING ON THE THICKNESS OF THE OZONE LAYER

The ozone content in the atmosphere is an important factor in shaping the intensity and spectral distribution of UV - solar radiation in the region B (280-320 nm). Even a relatively small change in the concentration of ozone in the atmosphere leads to significant changes in the intensity of the hard component of UV radiation near the Earth's surface. In this problem, it is necessary: ​​a) to establish the dependence of the level of UV radiation on the thickness of the ozone layer; b) calculate the allowable time for a person to stay under the influence of solar radiation.

Dividing K(L, T) by the area of ​​a sphere with a radius equal to the distance from the Sun to the Earth (Ron = 150 * 10 h m), we obtain Q(n, T) the spectral flux density of the radiant energy of the Sun in the ultraviolet region, reaching the upper layers of the atmosphere Lands:

In this way,

(during calculations! = 6000 K).

Radiation with a wavelength of 280-320 nm (in medical terminology - region B) - the most important for studying the damaging effect of solar radiation, is completely determined by the ozone content in the Earth's atmosphere, without taking into account the influence of molecular and aerosol scattering. Taking into account these factors, solar radiation on the Earth's surface (ultraviolet region) will be determined from the relationship:

where ad is the ozone absorption coefficient, 1/cm;

P is the coefficient of molecular scattering;

o - coefficient of aerosol dispersion;

X is the thickness of the ozone layer, cm.< 65°, nsm = z = secy

To determine the effective energy illumination created by a broadband radiation source, compared with the action of a radiation source with a wavelength of 270 nm, which has the maximum efficiency, we use the formula:

where: Y eff - spectral energy flux density of UV - radiation (UVR) (for each wavelength); bx ~ relative spectral efficiency of radiation, dimensionless value (Table 3.1); OH. - wavelength interval,

The allowable UV exposure time can be determined by dividing 30 J/m (maximum allowable UV exposure energy dose for K = 270 nm) by the effective irradiance:

Task #1

test questions

1. Sources of water pollution.

Pollution can be divided into several groups. According to the physical state - insoluble, colloidal and soluble. In composition - mineral, organic, bacterial and biological.

Minerals are represented by sand, clay, mineral salts, solutions of acids, alkalis, etc.

Organic - can be of plant, animal origin, and also contain oil and products derived from it, synthetic surfactants (surfactants).

Bacterial and biological pollution - effluents from food and light industry enterprises, household effluents (drainage from toilets, kitchens, showers, laundries, canteens, etc.). At many industrial enterprises, water is used as a coolant, solvent, is part of the product, is used for washing, enrichment, cleaning of raw materials and products.

In addition, synthetic surfactants (surfactants) are used in many technological processes. Currently, it is one of the most common chemical pollutants that is difficult to control. Surfactants can have a negative impact on water quality, the self-cleaning ability of water bodies, the human body, as well as enhance the adverse effects of other substances.

An important source of pollution are pesticides, which enter the reservoirs with rain and melt water from the soil surface. During aerial treatment of fields, the preparations are carried away by air currents and deposited on the surface of the reservoir.

The oil industry is a significant source of pollution of water bodies with oil and oil products. The ingress of oil into water bodies occurs when oil products spilled on the surface of the earth are washed away by rain and melt water, when oil pipelines break through, with wastewater from enterprises, etc.

Acid rain is a major hazard to water bodies.

1. Danger of raw sewage.

2. Conditions for the discharge of wastewater from industrial enterprises into water bodies.

Due to the fact that wastewater from industrial enterprises may contain specific contaminants, their discharge into the city drainage network is limited by a number of requirements. Industrial wastewater released into the drainage network should not: disrupt the operation of networks and structures; have a destructive effect on the material of pipes and elements of treatment facilities; contain more than 500 mg/l of suspended and floating substances; contain substances that can clog networks or deposit on pipe walls; contain combustible impurities and dissolved gaseous substances capable of forming explosive mixtures; contain harmful substances that prevent biological wastewater treatment or discharge into a reservoir; have a temperature above 40 C. Industrial wastewater that does not meet these requirements must be pre-treated and only then discharged into the city drainage network.

test questions

The main substances polluting the atmosphere.

1. Purification of emissions into the atmosphere from impurities.

Gas cleaning technology has a variety of methods and apparatus for removing dust and harmful gases. The choice of a method for purifying gaseous impurities is determined primarily by the chemical and physicochemical properties of this impurity. The nature of production has a great influence on the choice of method: the properties of the substances available in the production, their suitability as absorbers for gas, the possibility of recovery (capture and use of waste products) or disposal of captured products.

To purify gases from sulfur dioxide, hydrogen sulfide and methyl mercaptan, their neutralization with an alkali solution is used. The result is salt and water.

To purify gases from minor concentrations of impurities (no more than 1% by volume), direct-flow compact absorption apparatuses are used.

Along with liquid absorbents - absorbents - for cleaning, as well as for drying (dehydration) of gases, solid absorbents can be used. These include various brands of active carbons, silica gel, alumogel, zeolites.

Recently, ion exchangers have been used to remove gases with polar molecules from a gas stream. Gas purification processes with adsorbents are carried out in batch or continuous adsorbers.

Dry and wet oxidation processes, as well as catalytic conversion processes, can be used to purify the gas stream, in particular, catalytic oxidation is used to neutralize sulfur-containing gases of sulphate-cellulose production (gases from the cooking and evaporation shops, etc.). This process is carried out at a temperature of 500--600 ° C on a catalyst, which includes oxides of aluminum, copper, vanadium and other metals. Organosulfur substances and hydrogen sulfide are oxidized to a less harmful compound - sulfur dioxide (MPC for sulfur dioxide 0.5 mg / m 3, and for hydrogen sulfide 0.078 mg / m 3).

The Kiev plant "Khimvolokno" has a unique integrated system for cleaning ventilation emissions from viscose production. This is a complex set of mechanisms, compressor units, pipelines, huge absorption tanks. Every day, 6 million m 3 of exhaust air passes through the machine "lungs", and not only cleaning, but also regeneration is carried out.

Until now, a significant part of carbon disulphide has been emitted into the atmosphere in the viscose production of the plant. The cleaning system allows not only to protect the environment from pollution, but also to save valuable material.

Electrostatic precipitators are widely used to remove dust from emissions from thermal power plants. These are structures as high as a 10-15-storey building. They trap fly ash produced when solid fuels are burned. Specialists are working on improving the design of these devices, increasing their efficiency and reliability. The latest sample is designed for a capacity of more than a million cubic meters of gas per hour, which is used as a raw material for the production of building materials.

4. Acid precipitation

Rain, snow or sleet with high acidity. Acid precipitation is mainly due to emissions of sulfur and nitrogen oxides into the atmosphere from the combustion of fossil fuels (coal, oil and natural gas). Dissolving in atmospheric moisture, these oxides form weak solutions of sulfuric and nitric acids and precipitate as acid rain.

The relative acidity of a solution is expressed by the pH index (acidity is determined by the presence of free hydrogen ions H +; pH is an indicator of the concentration of hydrogen ions). At pH = 1, the solution is a strong acid (like an electrolyte in a battery); pH = 7 means neutral (pure water) and pH = 14 is strong alkali (lye). Since pH is measured on a logarithmic scale, an aqueous environment with pH = 4 is ten times more acidic than an environment with pH = 5, and a hundred times more acidic than an environment with pH = 6.

Normal unpolluted rainwater has a pH of 5.65. Acidic rains are those with a pH less than 5.65. The main sources of sulfur oxides (SO2 and SO3), which cause the formation of sulfuric acid, are thermal power plants running on oil and coal, as well as metallurgical plants. Nitric oxide (NO) and nitrogen dioxide (NO2), from which nitric acid is formed, enter the atmosphere in approximately equal amounts from thermal power plants operating on oil products and coal, and with the exhaust gases of automobile engines. A relatively small amount of hydrochloric acid in atmospheric precipitation is formed as a result of the accumulation of gaseous chlorine from various natural and industrial sources. Acid rain can also occur when sulfuric acid and nitrogen-containing gases (nitrogen dioxide NO2 and ammonia NH3) enter the atmosphere from natural sources (for example, during volcanic eruptions).

Different natural environments react differently to increased acidity. Acid precipitation can change the chemical properties of soil and water. Where the water in rivers and lakes has become quite acidic (pH less than 5), for example, in the Adirondacks (New York, USA) or in the southern regions of Norway and Sweden, fish disappear. When trophic chains are disturbed, the number of aquatic animal species, algae and bacteria is reduced. In cities, acid precipitation accelerates the destruction of marble and concrete structures, monuments and sculptures.

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Waste water composition. Characteristics of wastewater of various origins. The main methods of wastewater treatment. Technological scheme and layout of equipment. Mechanical calculation of primary and secondary settling tanks. Technical characteristics of the filter.

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General information about mechanical wastewater treatment. Mechanical purification, filtration and settling of water. The main parameters of frame-fill filters. The main pollution of wastewater. Separation of suspensions and emulsions in the field of gravitational forces.

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Wastewater generation from settlements, their impact on water bodies. The main categories of wastewater, depending on their origin: domestic, industrial, atmospheric. Examples of treatment facilities in small towns and villages.

Conditions for the discharge of wastewater into water bodies

The work of industrial enterprises is connected with the consumption of water. Water is used in technological and auxiliary processes or is an integral part of manufactured products. In this case, wastewater is generated, which must be discharged into nearby water bodies.

Discharge of sewage into a reservoir is not allowed if FROM f ≥ MPC. According to regulatory documents (for example, SanPiN 2.1.5.980-00 “Hygienic requirements for the protection of surface waters”), it is prohibited to discharge wastewater into water bodies that

· can be eliminated by organizing low-waste production, rational technology, maximum use in circulating and re-water supply systems after appropriate cleaning and disinfection in industry, urban economy and for irrigation in agriculture;

It is prohibited to discharge sewage within the boundaries of the zones of sanitary protection of sources of drinking and domestic water supply, fish protection zones, fishery conservation zones and in some other cases.

Wastewater can be discharged into water bodies subject to compliance with hygienic requirements for the water of the water body, depending on the type of water use.

Types of water use

1. Household and drinking and cultural and domestic water use

(SanPiN 2.1.5.980-00 "Hygienic requirements for the protection of surface waters")

2. Fishery water use

Water bodies of fishery significance include water bodies that are used or can be used for the extraction (catching) of aquatic biological resources.

(GOST 17.1.2.04-77 "Nature protection. Hydrosphere. Indicators of the state and rules for taxation of fishery water bodies")

When wastewater is discharged into water bodies, the water quality standards of the water body in the design section located below the wastewater outlet must comply with sanitary requirements, depending on the type of water use.

Water quality standards for water bodies include:

General requirements for the composition and properties of water in water bodies, depending on the type of water use;

List of maximum allowable concentrations (MPC) of normalized substances in the water of water bodies for various types of water use.

In the design section, the water must meet the regulatory requirements. The maximum allowable concentration (MPC) is used as a standard.

All harmful substances for which MPCs have been determined are subdivided according to limiting hazard indicators (LHI), which is understood as the greatest negative impact exerted by these substances. Substances belonging to the same LP implies the summation of the effect of these substances on the water body.

For water objects of household and drinking and cultural and domestic water use, three types of LPW are used: sanitary-toxicological, general sanitary and organoleptic.

For fishery reservoirs: sanitary-toxicological, general sanitary, organoleptic, toxicological and fishery.

Substances, the concentration of which changes in the water of a water body only by dilution, are called conservative; substances whose concentration changes both under the action of dilution and as a result of various chemical, physico-chemical and biological processes - non-conservative.

Calculation of the values ​​of standard discharges into the reservoir

The conditions for the discharge of wastewater into surface water bodies and the procedure for calculating the standards for the permissible discharge of substances contained in discharged wastewater are regulated by the “Methodology for calculating the standards for permissible discharges (VAT) of substances and microorganisms into water bodies for water users” (2007). Permissible discharge standards (VAT) are developed and approved for a period of 5 years for existing and projected water user organizations. The development of VAT values ​​is carried out both by a water user organization and on behalf of a design or research organization.

VAT values ​​are determined for all categories of water users according to the formula

where qst– maximum hourly flow rate of wastewater, m3/h; VAT INCLUDED– permissible concentration of a pollutant, g/m3.

The value of the permissible concentration of a pollutant for a conservative substance, according to which the assimilative capacity of a reservoir is determined only by dilution, is determined by the formula

where SPDC– maximum allowable concentration of a pollutant in the water of a watercourse, g/m3; SF– background concentration of the pollutant in the watercourse is higher than the discharge of wastewater, g/m3; n- the multiplicity of the total dilution of wastewater in the watercourse.

Imagine a situation where an industrial enterprise discharges wastewater after a technological process (Fig. 1)

Rice. 1. Situational scheme for calculating the conditions for the discharge of wastewater: 0–0 - zero point; I-I - settlement target; PP - industrial enterprise; OS - treatment plant

target - conditional section of a reservoir or watercourse, in which a set of works is carried out to obtain data on water quality.

Checkpoint is the cross section of the flow in which the water quality is controlled.

Background alignment – control point located upstream from the discharge of pollutants.

In the case of simultaneous use of a water body or its section for various needs, the most stringent water quality standards among those established are adopted for the composition and properties of its waters.

Thus, the situational diagram for different types of water use is shown in fig. 2.

Rice. Fig. 2. Situational scheme for the watercourse: a - cultural and domestic (M - settlement); b - fishery water use

When wastewater is discharged into water bodies, the sanitary condition of the water body in the design section is considered satisfactory if the following condition is met:

where FROM rs z– concentration i-th substance in the settlement section under the condition of the simultaneous presence of Z substances belonging to the same limiting hazard indicator (LHI); i = 1, 2, …, Z; Z is the amount of substances with the same LPW; FROMz MPC is the maximum allowable concentration z of a substance.

The main mechanism for reducing the concentration of a pollutant when discharging wastewater into water bodies is dilution.

Waste water dilution - This is the process of reducing the concentration of pollutants in water bodies, caused by the mixing of wastewater with the aquatic environment into which they are released.

The intensity of the dilution process is quantified dilution factor n , which is equal to the ratio of the sum of wastewater costs q st and the surrounding aquatic environment Q to waste water consumption

or the ratio of excess concentrations of pollutants at the place of release to similar concentrations in the considered section of the watercourse ( total dilution Location on):

, (5)

where FROM st is the concentration of pollutants in wastewater, g/m3; FROM f is the concentration of pollutants in water bodies before wastewater discharge, g/m3; FROM is the concentration of waste water pollutants in the considered section of the watercourse after the discharge of waste water, g/m3.

The process of wastewater dilution occurs in two stages: initial and main dilution. The total dilution factor is presented as a product

n= n n n 0, (6)

where n n - the multiplicity of the initial dilution, n 0 - the multiplicity of the main dilution.

The multiplicity of the initial dilution is determined by the method for pressure concentrated and dispersing outlets into the watercourse at absolute velocities of the jet outflow from the outlet of more than 2 m/s or at the ratio v st ≥ 4 v Wed where v Wed and v st - average speeds of river and waste waters.

At lower outlet velocities, the initial dilution calculation is not performed.

Multiplicity of the main dilution n 0 in the watercourse at the settlement site is determined by the method and by the formula

(7)

where γ - mixing coefficient showing what part of the river water is involved in the dilution of wastewater; qst is the maximum flow rate of wastewater, m3/s; Q is the estimated minimum water flow rate of the watercourse in the control section, m3/s.

The spread of impurities occurs in the direction of the prevailing currents, and in the same direction, the dilution ratio tends to increase. So, in the initial section (at the point of release), the dilution ratio n n= 1( Q= 0 or FROM= FROM st, and then, as the flow rate of the liquid increases, the impurity concentration decreases, and the dilution factor increases. In the limit, when all possible water costs for a given water body are involved in the mixing process, complete mixing occurs. Under conditions of complete mixing, the concentration of pollutants tends to the background, i.e. FROM→FROM f.

The section of a reservoir or watercourse from the place of wastewater discharge to the section where they are completely mixed is conditionally divided into three zones (Fig. 3):

1st zone - initial dilution. Here, the dilution process occurs due to the entrainment of the reservoir liquid by the turbulent flow of the waste water jet flowing from the outlet devices. At the end of the first zone, the difference between the velocities of the jet stream and the environment becomes insignificant.

2nd zone - the main dilution. The degree of dilution in this zone is determined by the intensity of turbulent mixing.

3rd zone - in this zone there is practically no wastewater dilution. The decrease in pollutant concentrations occurs mainly due to the processes of water self-purification.

Rice. 3. Scheme of wastewater distribution in the reservoir

Processes that change the nature of substances entering water bodies are called self-purification processes. The combination of dilution and self-purification make up the neutralizing ability of a water body.

Thus, to solve the problem of dilution of wastewater in a watercourse or reservoir means to determine the concentration of one or more pollutants at any point in the local zone of a water body affected by wastewater.

In doing so, you need:

1) establish a picture of the spread of pollutants in the watercourse under the influence of wastewater discharge, taking into account hydrodynamic factors;

2) identify the influence of natural factors on the dilution process in order to make the best use of local conditions for its regulation;

3) determine the possibility of using artificial measures to intensify the dilution of wastewater.

Factors determining the process of dilution of wastewater in watercourses and reservoirs

The dilution of wastewater in watercourses is determined by the complex influence of the following three processes:

- distribution of wastewater in the initial section of the watercourse, which depends on the design of the outlet facility;

– initial dilution of wastewater, flowing under the action of turbulent jets;

- the main dilution of wastewater, determined by the hydrodynamic processes of reservoirs and watercourses.

All factors and conditions characterizing the dilution process can be divided into two groups:

1st group- design and technological features of wastewater discharge (design of the outlet facility; number, shape and size of outlets; flow rate and speed of discharged wastewater; technology and sanitary indicators of wastewater (physical properties, concentration of pollutants, etc.);

Zinc** is not required before discharge into the reservoir. Otherwise, the required degree of wastewater treatment E, %, can be calculated by the formula

(22)

The required degree of wastewater treatment indicates by how many percent it is necessary to reduce the concentration of pollution in the wastewater treatment process to ensure water quality standards in the wastewater receiver.

Knowing the permissible concentration of the pollutant ( VAT INCLUDED), it is possible to calculate the normatively permissible discharge using formula (1).

Calculation of the required degree of wastewater treatment

When discharging wastewater into water bodies, it is necessary that the water of the water body in the design section meets the sanitary requirements in accordance with inequality (1).

To achieve this condition, it is necessary to calculate in advance the maximum permissible concentrations of pollutants in wastewater, with which this water can be discharged into a water body.

Main types of calculations:

Calculation of the required degree of wastewater treatment based on the content of suspended solids. Calculation of the required degree of wastewater treatment by the content of dissolved oxygen. Calculation of the required degree of wastewater treatment according to BODtotal mixture of water from a water body and wastewater. Calculation of the allowable temperature of wastewater before discharging it into water bodies. Calculation of the required degree of wastewater treatment for harmful substances.

Calculation of the required degree of wastewater treatment based on the content of suspended solids

The concentration of suspended solids in treated wastewater allowed to be discharged into a water body is determined from the expression:

(7)

where FROM f is the concentration of suspended solids in the water of a water body before wastewater discharge, mg/l; R- an increase in the content of suspended solids in the water of a water body in the design section permitted by sanitary standards (Rules).

Calculating the required concentration of suspended solids in treated wastewater ( FROM och) and knowing the concentration of suspended solids in the wastewater supplied for treatment ( FROM st), determine the required efficiency of wastewater treatment for suspended solids according to the formula:

(8)

Calculation of the allowable temperature of wastewater before discharging it into water bodies

The calculation is carried out on the basis of the conditions that the water temperature of the water body should not rise more than the value specified by the Rules, depending on the type of water use.

The temperature of wastewater allowed for discharge must satisfy the condition:

T st ≤ n∙T extra + T at 9)

where T add - allowable temperature increase; T c - the temperature of the water body to the place of wastewater discharge.

Example 1 It is planned to discharge wastewater from an industrial enterprise with a maximum flow rate into the watercourse q= 1.7 m3/s. Downstream from the planned onshore discharge of sewage, at a distance of 3.0 km, there is the village of M., which uses the water of the stream for bathing and recreation. The watercourse, according to the State Hydrometeorological Committee, is characterized in this area by the following indicators:

Average monthly discharge of the watercourse 95% probability Q= 37 m3/s;

Average depth 1.3 m;

Average flow velocity 1.2 m/s;

Chezy coefficient on this section FROM= 29 m½/s;

The tortuosity of the channel is weakly expressed.

Determine the multiplicity of dilution of wastewater in the design section. Waste water outlet - onshore.

Solution. Since the watercourse is used as a water body of the second category, intended for cultural and domestic water use, the design target is set 1000 m before the border of the village, where the water must meet the requirements for this type of water use.

In this case, the distance taken to calculate the length of the dilution section:

L= 3000 - 1000 = 2000 m.

Let us determine the coefficient of turbulent diffusion by expression (6):

B. to. 10< FROM < 60, то

M \u003d 0.7 ∙ C + 6 \u003d 0.7 ∙ 29 + 6 \u003d 26.3.

Since the release is coastal, and the tortuosity of the channel is weakly expressed, then by expression (4.4) we determine

To simplify the calculation of the mixing coefficient by expression (4.3), we preliminarily calculate:

The multiplicity of dilution of wastewater from an industrial enterprise in the design section according to expression (4.2) will be

Task #1

Objective: calculate the characteristics of wastewater, namely the dilution ratio, the concentration at the water intake, the maximum concentration in the drain, the maximum allowable flow. Construct a graph of the dependence of the concentration of a harmful component on the distance to the place of water intake.

Table 1. Input parameters

Solution algorithm:

In order to solve the problem, we first need to calculate the turbulent diffusion coefficient:

It is customary to evaluate the conditions for the discharge of wastewater into a reservoir, taking into account their influence at the nearest water use point, where the dilution ratio should be determined. The calculation is carried out according to the formula:

So, many factors, such as the conditions of the river, banks and sewage, affect the speed of movement of water masses and determine the distance from the point of discharge of wastewater to the point of complete mixing. The release of wastewater into water bodies should, as a rule, be carried out in such a way that it is possible to mix wastewater with the water of the reservoir at the place of their discharge.

Next, it is necessary to determine how much pollutants can be discharged by the enterprise so as not to exceed the standards. Calculations are carried out only for conservative substances according to the sanitary and toxicological indicator of water content. The calculation is carried out according to the formula:

Where C senior chairman - the maximum concentration that can be allowed in wastewater, or the level of wastewater treatment at which, after mixing with water in a reservoir at the settlement point of water use, the degree of pollution does not exceed the MPC; MPC - maximum permissible concentration.

The next step is to calculate the maximum allowable flow (MPD) using the formula:

We substitute formula (10) into formula (15):

We substitute formula (16) into the function and get:

Table 4. Final values ​​of phenol concentration

Table 5. Endpoint concentrations of various substances

Conclusions:

The obtained results show that at a distance to the water intake point L = 200 m, the dilution factor is 2.0067, and the concentration of phenol in water will be C B = 9.95 mg/l, which is ten times higher than MPC = 0.35 mg/l. The concentration of the harmful substance should be reduced, for example, by better purifying wastewater or by reducing its consumption.

In order for the concentration of phenol at the place of water intake to be within the MPC, its concentration in wastewater should not exceed C st.pred. = 0.9821 mg/l. The maximum allowable flow of MPD = 1.1785 mg / s.

Based on the results of the calculated data, a graph of the distribution of phenol concentration was plotted depending on the distance between the wastewater discharge point and the water intake point. The graph shows that at a distance of more than 200 km, the concentration of phenol practically does not change - this is due to the fact that at such large distances phenol has dissolved to the maximum and can no longer dissolve even more. The best result in the approximation is shown by a polynomial of the 6th degree.

Also, the analysis of the obtained data showed that the concentration of phenol in the reservoir will never reach the MPC, since the concentration of the harmful substance in the wastewater is too high, and the water flow in the river is too small compared to the wastewater flow. This is also due to the fact that phenol is poorly soluble and lighter than water.

The constructed graph of the solubility of various harmful substances shows that mercury salts are the most soluble, and kerosene is the least soluble. This is probably due to the density of substances (for kerosene it is 800 kg / m³, for mercury 13,500 kg / m 3), as well as from the solubility constants (for mercury salts it is about 10 -15, for kerosene about 10 -20).

The following programs were used to solve the problem and plot graphs: Microsoft Word, Microsoft Excel, MathCAD.

Answers to control questions:

1. Sources of water pollution:

a) Industry - pulp and paper, oil refining, ferrous metallurgy, etc.

b) Agriculture - irrigation of fields, wastewater saturated with salts and chemical residues. substances, organic residues of farms.

c) Household waste - almost all water used in settlements ends up in the sewerage system.

2. Danger of raw sewage:

b) Wastewater may contain chemicals that have a bad effect on living organisms, which is harmful to the biosphere;

c) The content of oxygen dissolved in water is reduced in wastewater, which reduces the activity of putrefactive bacteria and leads to waterlogging of the area.

3. Conditions for the discharge of wastewater from industrial enterprises into water bodies:

After the release of wastewater, some deterioration in the quality of water in reservoirs is allowed, however, this should not noticeably affect his life and the possibility of further use of the reservoir as a source of water supply, for cultural and sports events, fisheries and other purposes.

4. Sedimentation and Nutrient Control:

In the process of wastewater treatment, 9000 m3 of precipitation is treated at Moscow aeration stations during the year. All sediments are disinfected. Of the total amount of precipitation, about 3500 m3 goes to silt pads. Until now, the main method of sludge disinfection was natural drying on sludge beds, where it was dried to a moisture content of about 80%, while decreasing in volume by 7 times.

5. Collection and treatment of wastewater:

The sanitary sewer system connects all sewers from sinks, bathtubs located in buildings, etc., just like a tree trunk connects all its branches. From the base of this “trunk” flows a mixture of everything that has entered the system - the original effluents, or the original wastewater.

6. Pollution of the hydrosphere with pesticides:

It has been established that more than 400 types of substances can cause water pollution. There are chemical, biological and physical pollutants. Among chemical pollutants, the most common ones include oil and oil products, pesticides, heavy metals, dioxides and other pathogens, and physical radioactive substances, heat, etc. Biological pollutants, such as viruses and other pathogens, and physical radioactive substances pollute water very dangerously. heat, etc. Chemical pollution is the most common, persistent and far-reaching. It can be organic (phenols, pesticides, etc.) and inorganic (salts, acids, alkalis), toxic (arsenic, mercury compounds, lead, etc.) and non-toxic.