Industrial and economic development is usually accompanied by an increase in environmental pollution. Most large cities are characterized by a significant concentration of industrial facilities in relatively small areas, which poses a danger to human health.
One of the environmental factors that has the most pronounced impact on human health is air quality. At present, emissions of pollutants into the atmosphere pose a particular danger. This is due to the fact that toxicants enter the human body mainly through the respiratory tract.
Air emissions: sources
There are natural and anthropogenic sources of air pollutants. The main impurities that contain atmospheric emissions from natural sources are dust of cosmic, volcanic and plant origin, gases and smoke generated as a result of forest and steppe fires, products of destruction and weathering of rocks and soils, etc.
Levels of air pollution from natural sources are background. They change quite little over time. The main sources of pollutants entering the air at the present stage are anthropogenic, namely industry (various industries), agriculture and motor transport.
Emissions from enterprises into the atmosphere
The largest “suppliers” of various pollutants into the air are metallurgical and energy enterprises, chemical production, the construction industry, and mechanical engineering.
During the combustion of various types of fuel by energy complexes, large amounts of sulfur dioxide, carbon and nitrogen oxides, and soot are released into the atmosphere. A number of other substances, in particular hydrocarbons, are also present in emissions (in smaller quantities).
The main sources of dust and gas emissions in metallurgical production are melting furnaces, casting plants, pickling departments, sintering machines, crushing and grinding equipment, unloading and loading of materials, etc. The largest share among the total amount of substances entering the atmosphere is occupied by carbon monoxide, dust, sulfur dioxide, Nitric oxide. Manganese, arsenic, lead, phosphorus, mercury vapor, etc. are released in slightly smaller quantities. Also, during the steelmaking process, emissions into the atmosphere contain steam-gas mixtures. They contain phenol, benzene, formaldehyde, ammonia and a number of other hazardous substances.
Harmful emissions into the atmosphere from chemical industry enterprises, despite their small volumes, pose a particular danger to the natural environment and humans, since they are characterized by high toxicity, concentration and significant diversity. The mixtures entering the air, depending on the type of product being manufactured, may contain volatile organic compounds, fluorine compounds, nitrous gases, solids, chloride compounds, hydrogen sulfide, etc.
During the production of building materials and cement, emissions into the atmosphere contain significant amounts of various dusts. The main technological processes leading to their formation are grinding, processing of charges, semi-finished products and products in streams of hot gases, etc. Around factories producing various building materials, contamination zones with a radius of up to 2000 m can form. They are characterized by a high concentration of dust containing particles of gypsum, cement, quartz, as well as a number of other pollutants.
Vehicle emissions
In large cities, a huge amount of pollutants into the atmosphere comes from vehicles. According to various estimates, their share accounts for from 80 to 95%. consist of a large number of toxic compounds, in particular nitrogen and carbon oxides, aldehydes, hydrocarbons, etc. (about 200 compounds in total).
The greatest volumes of emissions are observed in areas where traffic lights and intersections are located, where cars move at low speeds and in idling mode. Calculation of emissions into the atmosphere shows that the main components of the exhaust in this case are hydrocarbons.
It should be noted that, in contrast to stationary sources of emissions, the operation of motor vehicles leads to air pollution on city streets at the height of human growth. As a result, pedestrians, residents of houses located near roads, as well as vegetation growing in adjacent areas are exposed to harmful effects of pollutants.
Agriculture
Impact on humans
According to various sources, there is a direct link between air pollution and a number of diseases. For example, the duration of respiratory diseases in children who live in relatively polluted areas is 2-2.5 times longer than in those living in other areas.
In addition, in cities characterized by unfavorable environmental conditions, children have functional deviations in the immune system and blood formation, and violations of compensatory and adaptive mechanisms to environmental conditions. Many studies have also revealed a connection between air pollution and human mortality.
The main components of emissions entering the air from various sources are suspended substances, oxides of nitrogen, carbon and sulfur. It was revealed that zones exceeding the maximum permissible concentrations for NO 2 and CO cover up to 90% of the urban area. The given macrocomponents of emissions can cause serious illnesses. The accumulation of these contaminants leads to damage to the mucous membranes of the upper respiratory tract and the development of pulmonary diseases. In addition, increased concentrations of SO 2 can cause degenerative changes in the kidneys, liver and heart, and NO 2 - toxicosis, congenital anomalies, heart failure, nervous disorders, etc. Some studies have revealed a relationship between the incidence of lung cancer and the concentrations of SO 2 and NO 2 in the air.
conclusions
Pollution of the natural environment and, in particular, the atmosphere, has adverse consequences for the health of not only the present, but also subsequent generations. Therefore, we can safely say that the development of measures aimed at reducing emissions of harmful substances into the atmosphere is one of the most pressing problems of humanity today.
MINISTRY OF EDUCATION AND SCIENCE
RUSSIAN FEDERATION
STATE EDUCATIONAL INSTITUTION
HIGHER PROFESSIONAL EDUCATION
"MOSCOW STATE UNIVERSITY
FOOD PRODUCTION"
O.V. Gutina, Malofeeva Yu.N.
EDUCATIONAL AND METHODOLOGICAL MANUAL for solving problems in the course
"ECOLOGY"
for students of all specialties
Moscow 2006
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1. Monitoring the quality of atmospheric air in the area of industrial enterprises. | |
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Task 1. Calculation of flue gas dispersion from a boiler room pipe | |
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2. Technical means and methods of protecting the atmosphere. | |
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Task 2. | |
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3. Pollution control. Regulatory and legal framework for nature conservation. Payment for environmental damage. | |
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Task 3. “Calculation of technological emissions and payment for pollution of hazardous pollutants using the example of a bakery plant” | |
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Literature | |
Dispersion of emissions from industrial enterprises in the atmosphere
Emissions are the entry of pollutants into the atmosphere. The quality of atmospheric air is determined by the concentration of pollutants contained in it, which should not exceed the sanitary and hygienic standard - the maximum permissible concentration (MAC) for each pollutant. MPC is the maximum concentration of a pollutant in the atmospheric air, related to a certain averaging time, which, with periodic exposure or throughout a person’s entire life, does not have a harmful effect on him, including long-term consequences.
With existing technologies for obtaining target products and existing methods for purifying emissions, reducing the concentrations of hazardous pollutants in the environment is ensured by increasing the dispersion area by removing emissions to a greater height. It is assumed that only such a level of aerotechnogenic environmental pollution is achieved at which natural self-purification of the air is still possible.
The highest concentration of each harmful substance is C m (mg/m 3) in the ground layer of the atmosphere should not exceed the maximum permissible concentration:
If the emission includes several harmful substances with a unidirectional effect, i.e. mutually reinforce each other, then the inequality must be satisfied:
(2)
C 1 - C n – actual concentration of a harmful substance in the atmosphere
air, mg/m3,
MPC - maximum permissible concentrations of pollutants (MP).
Scientifically based MPC standards in the surface layer of the atmosphere must be ensured by control of standards for all emission sources. This environmental standard is maximum permissible emission
MPE - the maximum emission of a pollutant, which, when dissipated in the atmosphere, creates a ground-level concentration of this substance that does not exceed the maximum permissible concentration, taking into account the background concentration.
Environmental pollution due to dispersion of industrial emissions through high chimneys depends on many factors: the height of the pipe, the speed of the emitted gas flow, the distance from the emission source, the presence of several nearby emission sources, meteorological conditions, etc.
Emission height and gas flow velocity. As the height of the pipe and the speed of the emitted gas flow increase, the efficiency of contaminant dispersion increases, i.e. dispersion of emissions occurs in a larger volume of atmospheric air, over a larger area of the earth's surface.
Wind speed. Wind is the turbulent movement of air over the surface of the earth. The direction and speed of the wind do not remain constant; the wind speed increases as the difference in atmospheric pressure increases. The greatest air pollution is possible with weak winds of 0-5 m/s when emissions are dissipated at low altitudes in the surface layer of the atmosphere. For emissions from high sources least e dispersion of contaminants occurs at wind speeds of 1-7 m/s (depending on the speed of exit of the gas stream from the mouth of the pipe).
Temperature stratification. The ability of the earth's surface to absorb or radiate heat affects the vertical distribution of temperature in the atmosphere. Under normal conditions When you rise up 1 km, the temperature decreases by 6,5 0 : temperature gradient is 6,5 0 /km. In real conditions, deviations from a uniform decrease in temperature with height may be observed - temperature inversion. Distinguish surface and elevated inversions. Surface ones are characterized by the appearance of a warmer layer of air directly at the surface of the earth, elevated ones are characterized by the appearance of a warmer layer of air (inversion layer) at a certain height. In inversion conditions, the dispersion of pollutants worsens; they are concentrated in the surface layer of the atmosphere. When a polluted gas stream is released from a high source, the greatest air pollution is possible with an elevated inversion, the lower boundary of which is located above the source of the release and the most dangerous wind speed is 1 - 7 m/s. For low emission sources, the combination of a surface inversion with weak winds is most unfavorable.
Terrain. Even in the presence of relatively small elevations, the microclimate in certain areas and the nature of the dispersion of pollution change significantly. Thus, in low places, stagnant, poorly ventilated zones with an increased concentration of pollutants are formed. If there are buildings in the path of the polluted flow, then above the building the air flow speed increases, immediately behind the building it decreases, gradually increasing with distance, and at some distance from the building the air flow speed takes on its original value. Aerodynamic shadow – a poorly ventilated area formed when air flows around a building. Depending on the type of building and the nature of the development, various zones with closed air circulation are formed, which can have a significant impact on the distribution of pollution.
Methodology for calculating the dispersion of harmful substances in the atmosphere contained in emissions , is based on determining the concentrations of these substances (mg/m 3) in the ground layer of air. Danger level pollution of the ground layer of atmospheric air by emissions of harmful substances is determined by the highest calculated value of the concentration of harmful substances, which can be established at some distance from the source of the emission under the most unfavorable weather conditions (wind speed reaches a dangerous value, intense turbulent vertical exchange is observed, etc.).
Calculation of emission dispersion is carried out according toOND-86.
The maximum surface concentration is determined by the formula:
(3)
A – coefficient depending on the temperature stratification of the atmosphere (the value of coefficient A is taken equal to 140 for the Central region of the Russian Federation).
M – emission power, mass of pollutant emitted per unit time, g/s.
F is a dimensionless coefficient that takes into account the rate of deposition of harmful substances in the atmosphere (for gaseous substances it is equal to 1, for solid substances - 1).
is a dimensionless coefficient that takes into account the influence of terrain (for flat terrain - 1, for rough terrain - 2).
H – height of the emission source above ground level, m.
– the difference between the temperature emitted by the gas-air mixture and the temperature of the surrounding outside air.
V 1 – flow rate of the gas-air mixture leaving the emission source, m 3 /s.
m, n – coefficients taking into account the release conditions.
Enterprises that emit harmful substances into the environment must be separated from residential buildings by sanitary protection zones. The distance from the enterprise to residential buildings (the size of the sanitary protection zone) is established depending on the amount and type of pollutants emitted into the environment, the capacity of the enterprise, and the features of the technological process. Since 1981 The calculation of the sanitary protection zone is regulated by state standards. SanPiN 2.2.1/2.1.1.1200-03 “Sanitary protection zones and sanitary classification of enterprises, structures and other objects.” According to it, all enterprises are divided into 5 classes according to their degree of danger. And depending on the class, the standard value of the sanitary protection zone is established.
Enterprise (class) Dimensions of the sanitary protection zone
I class 1000 m
II class 500 m
III class 300 m
IV class 100 m
V class 50
One of the functions of the sanitary protection zone is the biological purification of atmospheric air using landscaping. Trees and shrubs for gas absorption purposes (phytofilters) capable of absorbing gaseous pollutants. For example, it has been established that meadow and woody vegetation can bind 16-90% of sulfur dioxide.
Task No. 1: The boiler room of an industrial enterprise is equipped with a boiler unit that runs on liquid fuel. Combustion products: carbon monoxide, nitrogen oxides (nitrogen oxide and nitrogen dioxide), sulfur dioxide, fuel oil ash, vanadium pentoxide, benzopyrene, and sulfur dioxide and nitrogen dioxide have a unidirectional effect on the human body and form a summation group.
The task requires:
1) find the maximum ground concentration of sulfur dioxide and nitrogen dioxide;
2) the distance from the pipe to the place where S M appears;
Initial data:
Boiler room productivity – Q rev =3000 MJ/h;
Fuel – sulphurous fuel oil;
Efficiency of the boiler installation – k.u. =0.8;
Chimney height H=40 m;
Chimney diameter D=0.4m;
Release temperature T g =200С;
Outside air temperature T = 20С;
Quantity of exhaust gases from 1 kg of burned fuel oil V g = 22.4 m 3 /kg;
Maximum permissible concentration of SO 2 in atmospheric air –
With PDK a.v. =0.05 mg/m3;
Maximum permissible concentration of NO 2 in atmospheric air –
With PDK a.v. =0.04 mg/m3;
Background concentration of SO 2 – C f =0.004 mg/m 3 ;
Heat of combustion of fuel Q n =40.2 MJ/kg;
The location of the boiler room is Moscow region;
The terrain is calm (with a height difference of 50m per 1km).
The calculation of the maximum surface concentration is carried out in accordance with the regulatory document OND-86 “Methodology for calculating concentrations in the atmospheric air of pollutants contained in emissions from enterprises.”
C M = 
,
=Т Г – Т В = 200 – 20 = 180 о С.
To determine the consumption of the gas-air mixture, we find the hourly fuel consumption:
In h = 
V 1 = 
m – dimensionless coefficient depending on the conditions of the release: the exit velocity of the gas-air mixture, the height and diameter of the release source and the temperature difference.
f = 
the exit speed of the gas-air mixture from the mouth of the pipe is determined by the formula:
o = 
f= 1000 
.
n – dimensionless coefficient depending on the release conditions: volume of the gas-air mixture, height of the release source and temperature difference.
Determined by characteristic value
V M = 0.65 
n = 0.532V m 2 – 2.13V m + 3.13 = 1.656
M = V 1 a, g/s,
M SO 2 = 0.579 3 = 1.737 g/s,
M NO 2 =0.8 0.579 = 0.46 g/s.
Maximum ground concentration:
sulfur dioxide -
C M = 
nitrogen dioxide -
Cm = .
We find the distance from the pipe to the place where C M appears using the formula:
X M = 
where d is a dimensionless coefficient depending on the emission conditions: the exit velocity of the gas-air mixture, the height and diameter of the emission source, the temperature difference and the volume of the gas-air mixture.
d = 4.95V m (1 + 0.28f), at 0.5 V M 2,
d = 7 V M (1 + 0.28f), with V M 2.
We have V M = 0.89 d = 4.95 0.89(1 + 0.280.029) = 4.7
X M = 
Because If the ground-level concentration of sulfur dioxide exceeds the maximum permissible concentration of sulfur dioxide in the atmospheric air, then the value of the maximum permissible concentration of sulfur dioxide for the source in question is determined, taking into account the need to fulfill the summation equation
Substituting our values, we get:
which is greater than 1. To satisfy the conditions of the summation equation, it is necessary to reduce the mass of sulfur dioxide emission, while maintaining the emission of nitrogen dioxide at the same level. Let's calculate the ground level concentration of sulfur dioxide at which the boiler house will not pollute the environment.
=1-
= 0,55
C SO2 = 0.55 0.05 = 0.0275 mg/m 3
The efficiency of the purification method, ensuring a reduction in the mass of sulfur dioxide emissions from the initial value M = 1.737 g/s to 0.71 g/s, is determined by the formula:
%,
where СВХ is the concentration of the pollutant at the inlet to the gas treatment plant
installation, mg/m 3,
C OUT – concentration of the pollutant at the outlet of the gas
treatment plant, mg/m3.
Because 
, A 
, That
then the formula will take the form:
Therefore, when choosing a cleaning method, it is necessary that its efficiency be at least 59%.
Technical means and methods of protecting the atmosphere.
Emissions from industrial enterprises are characterized by a wide variety of dispersed composition and other physicochemical properties. In this regard, various methods for their purification and types of gas and dust collectors - devices designed to purify emissions from pollutants - have been developed.
M 
methods for cleaning industrial emissions from dust can be divided into two groups: dust collection methods "dry" method and dust collection methods "wet" method. Gas dust removal devices include: dust settling chambers, cyclones, porous filters, electric precipitators, scrubbers, etc.
The most common dry dust collection installations are cyclones various types.
They are used to capture flour and tobacco dust, ash formed when burning fuel in boiler units. The gas flow enters the cyclone through pipe 2 tangentially to the inner surface of housing 1 and performs a rotational-translational motion along the housing. Under the influence of centrifugal force, dust particles are thrown to the wall of the cyclone and, under the influence of gravity, fall into the dust collection hopper 4, and the purified gas exits through the outlet pipe 3. For normal operation of the cyclone, its tightness is necessary; if the cyclone is not sealed, then due to suction outside air, dust is carried out with a flow through the outlet pipe.
The tasks of cleaning gases from dust can be successfully solved by cylindrical (TsN-11, TsN-15, TsN-24, TsP-2) and conical (SK-TsN-34, SK-TsN-34M, SKD-TsN-33) cyclones, developed by the Research Institute for Industrial and Sanitary Gas Purification (NIIOGAZ). For normal operation, the excess pressure of gases entering the cyclones should not exceed 2500 Pa. In this case, in order to avoid condensation of liquid vapors, the temperature of the gas is selected to be 30 - 50 o C above the t dew point, and according to the conditions of structural strength - no higher than 400 o C. The productivity of the cyclone depends on its diameter, increasing with the growth of the latter. The cleaning efficiency of cyclones of the TsN series decreases with increasing angle of entry into the cyclone. As the particle size increases and the cyclone diameter decreases, the cleaning efficiency increases. Cylindrical cyclones are designed to collect dry dust from aspiration systems and are recommended for use for pre-cleaning of gases at the inlet of filters and electric precipitators. Cyclones TsN-15 are made of carbon or low-alloy steel. Canonical cyclones of the SK series, designed for cleaning gases from soot, have increased efficiency compared to cyclones of the TsN type due to greater hydraulic resistance.
To purify large masses of gases, battery cyclones are used, consisting of a large number of parallel installed cyclone elements. Structurally, they are combined into one housing and have a common gas supply and outlet. Experience in operating battery cyclones has shown that the cleaning efficiency of such cyclones is somewhat lower than the efficiency of individual elements due to the flow of gases between the cyclone elements. The domestic industry produces battery cyclones such as BC-2, BTsR-150u, etc.
Rotary Dust collectors are centrifugal devices that, while moving air, clean it from dust fractions larger than 5 microns. They are very compact, because... the fan and dust collector are usually combined in one unit. As a result, during the installation and operation of such machines, no additional space is required to accommodate special dust collection devices when moving a dusty flow with an ordinary fan.
The design diagram of the simplest rotary type dust collector is shown in the figure. When the fan wheel 1 operates, dust particles, due to centrifugal forces, are thrown towards the wall of the spiral casing 2 and move along it in the direction of the exhaust hole 3. The dust-enriched gas is discharged through a special dust receiving hole 3 into the dust bin, and the purified gas enters the exhaust pipe 4 .
To increase the efficiency of dust collectors of this design, it is necessary to increase the portable speed of the purified flow in the spiral casing, but this leads to a sharp increase in the hydraulic resistance of the device, or to reduce the radius of curvature of the casing spiral, but this reduces its productivity. Such machines provide a fairly high efficiency of air purification while capturing relatively large dust particles - over 20 - 40 microns.
More promising rotary dust separators, designed to clean air from particles 5 µm in size, are counter-flow rotary dust separators (RPD). The dust separator consists of a hollow rotor 2 with a perforated surface built into the casing 1 and a fan wheel 3. The rotor and fan wheel are mounted on a common shaft. When the dust separator operates, dusty air enters the housing, where it swirls around the rotor. As a result of the rotation of the dust flow, centrifugal forces arise, under the influence of which suspended dust particles tend to separate from it in the radial direction. However, aerodynamic drag forces act on these particles in the opposite direction. Particles whose centrifugal force is greater than the aerodynamic drag force are thrown toward the walls of the casing and enter hopper 4. The purified air is thrown out through the perforation of the rotor using a fan.
The efficiency of PRP cleaning depends on the selected ratio of centrifugal and aerodynamic forces and theoretically can reach 1.
A comparison of PDPs with cyclones demonstrates the advantages of rotary dust collectors. Thus, the overall dimensions of the cyclone are 3–4 times, and the specific energy consumption for cleaning 1000 m 3 of gas is 20–40% higher than that of the PRP, all other things being equal. However, rotary dust collectors are not widely used due to the relative complexity of the design and operating process compared to other devices for dry gas purification from mechanical contaminants.
To separate the gas flow into purified gas and dust-enriched gas, use louvered dust separator On the louvre grille 1, the gas flow with flow rate Q is divided into two flow paths with flow rates Q 1 and Q 2. Usually Q 1 = (0.8-0.9)Q, and Q 2 = (0.1-0.2)Q. The separation of dust particles from the main gas flow on the louvre grille occurs under the influence of inertial forces that arise when the gas flow turns at the entrance to the louvre grille, as well as due to the effect of reflection of particles from the surface of the grille upon impact. The dust-enriched gas flow after the louvered grille is directed to a cyclone, where it is cleaned of particles, and is reintroduced into the pipeline behind the louvered grille. Louvre dust separators are simple in design and are well arranged in gas ducts, providing a cleaning efficiency of 0.8 or more for particles larger than 20 microns. They are used to clean flue gases from coarse dust at temperatures up to 450 – 600 o C.
Electric precipitator. Electrical cleaning is one of the most advanced types of gas purification from suspended particles of dust and fog. This process is based on impact ionization of gas in the corona discharge zone, transfer of ion charge to impurity particles and deposition of the latter on collecting and corona electrodes. Precipitation electrodes 2 are connected to the positive pole of the rectifier 4 and grounded, and the corona electrodes are connected to the negative pole. The particles entering the electrostatic precipitator are connected to the positive pole of the rectifier 4 and are grounded, and the corona electrodes are charged with ion impurity ions. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 usually already have a small charge obtained due to friction against the walls of pipelines and equipment. Thus, negatively charged particles move towards the collection electrode, and positively charged particles settle on the negative discharge electrode.
Filters widely used for fine purification of gas emissions from impurities. The filtration process consists of retaining impurity particles on porous partitions as they move through them. The filter consists of housing 1, separated by a porous partition (filter-
Air pollution from industrial waste during disposal. The food industry is not one of the main air pollutants. However, almost all food industry enterprises emit gases and dust into the atmosphere, which worsen the condition of the atmospheric air and lead to an increase in the greenhouse effect. The flue gases emitted by boiler houses found in many food industry enterprises contain products of incomplete combustion of fuel; the flue gases also contain ash particles. Process emissions contain dust, solvent vapors, alkalis, vinegar, hydrogen, and excess heat. Ventilation emissions into the atmosphere include dust not captured by dust collection devices, as well as vapors and gases. Raw materials are delivered to many enterprises, and finished products and waste are transported by road. The intensity of its movement in a number of industries is seasonal - it increases sharply during the harvest period (meat and fat enterprises, sugar factories, processing factories, etc.); in other food production facilities, the movement of vehicles is more uniform throughout the year (bakery plants, tobacco factories, etc.) In addition, many technological installations of food industry enterprises are sources of unpleasant odors that irritate people, even if the concentration of the corresponding substance in the air does not exceed MPC (maximum permissible concentrations of harmful substances in the atmosphere). The most harmful substances entering the atmosphere from food industry enterprises are organic dust, carbon dioxide (CO 2), gasoline and other hydrocarbons, and emissions from fuel combustion. CO concentrations exceeding the maximum permissible concentration lead to physiological changes in the human body, and very high concentrations even lead to death. This is explained by the fact that CO is an extremely aggressive gas, easily combines with hemoglobin, resulting in the formation of carboxyhemoglobin, the increased content of which in the blood is accompanied by a deterioration in visual acuity and the ability to estimate the duration of time intervals, changes in the activity of the heart and lungs, and disruption of some psychomotor functions of the brain , headaches, drowsiness, respiratory failure and mortality, the formation of carboxyhemoglobin (this is a reversible process: after the inhalation of CO stops, its gradual removal from the blood begins). In a healthy person, the CO content decreases by half every 3-4 hours. CO is a stable substance; its lifetime in the atmosphere is 2-4 months. High concentrations of CO2 cause deterioration in health, weakness, and dizziness. This gas mainly affects the state of the environment, because is a greenhouse gas. Many technological processes are accompanied by the formation and release of dust into the environment (bakery factories, sugar factories, oil and fat factories, starch factories, tobacco, tea factories, etc.).
The existing level of atmospheric air pollution is assessed taking into account the background concentrations of pollutants in the atmospheric air of the area where the workshop is planned to be reconstructed. Approximate values of background concentrations of pollutants in atmospheric air. The average estimated values of background concentrations for the main controlled substances in the atmospheric air do not exceed the established maximum one-time MPC (maximum concentrations of impurities in the atmosphere, related to a certain averaging time, which, with periodic exposure or throughout a person’s entire life, does not affect him and the environment in generally direct or indirect effects, including long-term consequences) and amount to:
a) 0.62 d. MPC for solid particles in total,
b) 0.018 d. MPC for sulfur dioxide,
c) 0.4 d. MPC for carbon oxide,
d) 0.2 d. MPC for nitrogen dioxide,
e) 0.5 d. MPC for hydrogen sulfide.
The main sources of impact on atmospheric air on the territory of the poultry farm are:
a) Poultry houses,
b) Incubator,
c) Boiler room,
d) Feed preparation workshop,
e) Feed warehouse,
f) Meat processing shop,
g) Slaughter and meat processing workshop,
h) Grease drainage treatment station.
According to the Veterinary and Sanitary Rules for the collection, disposal and destruction of biological waste, waste incineration must be carried out in earthen trenches (pits) until a non-combustible inorganic residue is formed. A violation of this legislation is burning in the open ground outside of earthen trenches and not until a non-combustible inorganic residue is formed. Due to the spread of pathogenic viruses, such as avian influenza, limiting the degree of disease in animals in areas adjacent to the outbreak of the disease involves the complete destruction of sick animals, possible carriers of the disease.
Using a cremator for animals is one of the simplest and most effective ways to ensure sanitary cleanliness - dead animals are disposed of as they accumulate, and the risk of spreading diseases is reduced to zero, since after burning there is no waste left that can attract disease carriers (rodents and insects).
A poultry farm for 400 thousand laying hens or 6 million broiler chickens annually produces up to 40 thousand tons of placenta, 500 thousand m 3 of wastewater and 600 tons of technical poultry processing products. A large amount of arable land is used for waste storage. At the same time, the storage residue is a strong source of unpleasant odors. Waste heavily pollutes surface and groundwater. The biggest problem here is that drinking water purification equipment is not equipped to remove nitrogen-containing compounds, which are present in large quantities in the liquid afterbirth. That is why finding ways to effectively dispose of placenta is one of the main problems in the development of industrial poultry farming.
Emission inventory (GOST 17.2.1.04-77) is a systematization of information on the distribution of sources by territory, the quantity and composition of emissions of pollutants into the atmosphere. The main purpose of the inventory of pollutant emissions is to obtain initial data for:
- assessing the degree of impact of pollutant emissions from the enterprise on the environment (atmospheric air);
- establishing maximum permissible standards for emissions of pollutants into the atmosphere both for the enterprise as a whole and for individual sources of air pollution;
- organizing control over compliance with established standards for emissions of pollutants into the atmosphere;
- assessing the condition of the enterprise’s dust and gas cleaning equipment;
- assessing the environmental characteristics of technologies used at the enterprise;
- assessing the efficiency of using raw materials and waste disposal at the enterprise;
- planning air protection work at the enterprise.
All poultry farms are enterprises that emit dust, harmful gases and specific odors into the environment. Substances that pollute atmospheric air are numerous and varied in terms of harmfulness. They can be in the air in different states of aggregation: in the form of solid particles, vapor, gases. The sanitary significance of these pollutants is determined by the fact that they have a widespread distribution, cause volumetric air pollution, cause obvious harm to residents of populated areas and cities, and to poultry farms themselves, since they affect the deterioration of poultry health, and therefore its productivity. When deciding on the placement of livestock complexes, the choice of systems for processing and using livestock waste, experts proceeded from the fact that the leading components of the environment - atmospheric air, soil, water bodies - are practically inexhaustible from an environmental point of view. However, the operating experience of the first built livestock complexes testified to the intense pollution of environmental objects and their unfavorable impact on the living conditions of the population. Protection of the environment from pollution, prevention of infectious, invasive and other diseases of people and animals are associated with the implementation of measures to create effective systems for the collection, removal, storage, disinfection and use of manure and manure waste, improvement and effective operation of air purification systems, proper placement of livestock complexes and manure treatment facilities in relation to populated areas, sources of domestic and drinking water supply and other objects, i.e. with a complex of measures of hygienic, technological, agricultural and architectural and construction profiles. The intense and diverse impact of agriculture on the environment is explained not only by the growing consumption of natural resources necessary for the continuous growth of agricultural production, but also by the generation of significant waste and wastewater from livestock farms, complexes, poultry farms and other agricultural facilities. Thus, in the area where large poultry farms operate, atmospheric air may be polluted by microorganisms, dust, foul-smelling organic compounds that are products of the decomposition of organic waste, as well as oxides of nitrogen, sulfur, and carbon released during the combustion of natural energy carriers.
In connection with the existing problem, it is necessary to develop measures to reduce the level of air pollution in the area of influence of poultry farms. In general, measures to protect the air basin of poultry farms can be divided into general and private. General measures to combat air pollution include a high sanitary culture of the industry, uninterrupted operation of microclimate systems (primarily ventilation), removal of litter, thorough cleaning and disinfection of premises, organization of a sanitary protection zone, etc. At the same time, the allocation of sanitary protection zones is of particular importance in protecting the environment and human health from adverse effects from complexes (poultry farms). According to the standards SN 245-72, sanitary protection zones separate objects that are a source of harmful and unpleasant-smelling substances from residential buildings. The sanitary protection zone is the territory between places where harmful substances are released into the environment and residential and public buildings. Rational placement of poultry farm facilities, sanitary protective zoning and other measures make it possible to protect the atmospheric air of the residential area.
However, the amount of microorganisms and dust remains at a fairly high level, so the layout of poultry complexes cannot be considered as the only means of protecting the environment in order to create favorable conditions for places where the population lives. Along with this, private measures are also necessary (technological, sanitary and technical measures) aimed at cleaning, disinfecting and deodorizing the air and helping to reduce the flow of pollutants into the environment.
Measures to reduce air pollution with foul-smelling substances at large poultry farms include the construction of facilities for the disposal of poultry waste and heat treatment of manure. When manure is stored anaerobically (without access to air) in the same room as the bird, the air may contain ammonia, hydrogen sulfide and such volatile compounds. Thus, in the area where large poultry farms operate, atmospheric air may be polluted by microorganisms, dust, foul-smelling organic compounds that are products of the decomposition of organic waste, as well as oxides of nitrogen, sulfur, and carbon released during the combustion of natural energy resources. Based on the amount of pollutants emitted and their specificity, industrial poultry farming enterprises can be classified as sources that have a significant impact on the atmospheric air. In connection with the existing problem, it is necessary to develop measures to reduce the level of air pollution in the area of influence of poultry farms. However, it should be emphasized that air purification and disinfection are economically expensive and should be used where it is practical and necessary. Often, general means of combating air pollution are sufficient to protect the air flow of poultry farms and the surrounding area. In this regard, the creation of effective programs aimed at regulating the quality of atmospheric air in the area where enterprises operate requires an adequate assessment of its observed state and a forecast of changes in this state.
Industrial waste
Industrial enterprises transform almost all components of nature (air, water, soil, flora and fauna). Solid industrial waste, hazardous wastewater, gases, and aerosols are released into the biosphere (water bodies and soil), which accelerates the destruction of building materials, rubber, metal, fabric and other products and can cause the death of plants and animals. These chemically complex substances cause the greatest damage to the health of the population.
Air purification from harmful emissions from enterprises
Dust suspended in the air adsorbs poisonous gases, forming dense, toxic fog (smog), which increases the amount of precipitation. Saturated with sulfur, nitrogen and other substances, these sediments form aggressive acids. For this reason, the rate of corrosion destruction of machinery and equipment increases many times.
Protection of the atmosphere from harmful emissions is achieved by rational placement of sources of harmful emissions in relation to populated areas; dispersing harmful substances in the atmosphere to reduce concentrations in its ground layer, removing harmful emissions from the source of formation through local or general exhaust ventilation; using air purification agents to remove harmful substances.
Rational placement provides for the maximum possible removal of industrial facilities - air pollutants from populated areas, the creation of sanitary protection zones around them; taking into account the terrain and the prevailing wind direction when placing sources of pollution and residential areas in relation to each other.
To remove harmful gas impurities, dry and wet type dust collectors are used.
To dust collectors dry types include cyclones of various types - single, group, battery (Fig. 1). Cyclones at
change at inlet dust concentrations up to 400 g/m 3, at gas temperatures up to 500°C.
Filters that provide high efficiency in collecting large and small particles are widely used in dust collection technology. Depending on the type of filter material, filters are divided into fabric, fiber and granular. Highly efficient electrostatic precipitators are used to purify large volumes of gas.
Dust collectors wet type are used for purifying high-temperature gases, capturing fire and explosive dusts, and in cases where, along with dust collection, it is necessary to capture toxic gas impurities and vapors. Wet type devices are called scrubbers(Fig. 2).
To remove harmful gas impurities from exhaust gases, absorption, chemisorption, adsorption, thermal afterburning, and catalytic neutralization are used.
Absorption - dissolution of a harmful gas impurity with a sorbent, usually water. Method chemisorption is that. that the gas to be purified is irrigated with solutions of reagents that react chemically with harmful impurities to form non-toxic, low-volatile or insoluble chemical compounds. Adsorption - trapping of molecules of harmful substances by the surface of a microporous adsorbent (activated carbon, silica gel, zeolites). Thermal afterburning - oxidation of harmful substances by air oxygen at high temperatures (900-1200°C). Catalytic neutralization is achieved by using catalysts - materials that accelerate reactions or make them possible at much lower temperatures (250-400°C).
Rice. 1. Battery cyclone
Rice. 2. Scrubber
In case of severe and multi-component contamination of exhaust gases, complex multi-stage systems are used
cleaning systems consisting of devices of various types installed in series.
Water purification from harmful emissions and discharges from enterprises
The task of cleaning the hydrosphere from harmful discharges is more complex and large-scale than cleaning the atmosphere from harmful emissions: dilution and reduction of concentrations of harmful substances in water bodies occurs worse, since the aquatic environment is more sensitive to pollution.
Protection of the hydrosphere from harmful discharges involves the use of the following methods and means: rational placement of discharge sources and organization of water intake and drainage; dilution of harmful substances in water bodies to acceptable concentrations using specially organized and dispersed releases: use of wastewater treatment products.
Methods of wastewater treatment are divided into mechanical, physico-chemical and biological.
Mechanical cleaning wastewater from suspended particles is carried out by filtering, settling, processing in the field of centrifugal forces, filtration, flotation.
Straining used to remove large and fibrous inclusions from wastewater. Advocacy based on the free settling (floating) of impurities with a density greater (less) than water. Cleaning of drains in the field of centrifugal forces is implemented in hydrocyclones, where, under the influence of the centrifugal force arising in a rotating flow, a more intensive separation of suspended particles from the water flow occurs. Filtration used to purify wastewater from fine impurities both at the initial and final stages of purification. Flotation consists of enveloping impurity particles with small bubbles of air supplied to the branch water, and raising them to the surface, where a layer of foam is formed.
Physico-chemical methods purification is used to remove soluble impurities (salts of heavy metals, cyanides, fluorides, etc.) from wastewater, and in some cases to remove suspended matter. As a rule, physical and chemical methods are preceded by a stage of purification from suspended substances. Of the physicochemical methods, the most common are electroflotation, coagulation, reagent, ion exchange, etc.
Electroflotation carried out by passing an electric current through wastewater, which occurs between pairs of electrodes. As a result of the electrolysis of water, gas bubbles are formed, primarily light hydrogen, as well as oxygen, which envelop suspended particles and contribute to their rapid ascent to the surface.
Coagulation - This is a physical and chemical process of enlargement of the smallest colloidal and dispersed particles under the influence of molecular attraction forces. As a result of coagulation, water turbidity is eliminated. Coagulation is carried out by mixing water with coagulants (substances containing aluminum, ferric chloride, ferrous sulfate, etc. are used as coagulants) in chambers, from where the water is sent to settling tanks, where the flakes are separated by settling.
Essence reagent method consists of treating wastewater with chemical reagents that, when reacting chemically with dissolved toxic impurities, form non-toxic or insoluble compounds. A variation of the reagent method is the process of neutralizing wastewater. Neutralization of acidic wastewater is carried out by adding water-soluble alkaline reagents (calcium oxide, sodium hydroxides, calcium, magnesium, etc.); neutralization of alkaline wastewater - by adding mineral acids - sulfuric, hydrochloric, etc. Reagent cleaning is carried out in containers equipped with mixing devices.
Ion exchange purification wastewater treatment involves passing wastewater through ion exchange resins. When wastewater passes through the resin, the mobile ions of the resin are replaced by ions of the corresponding sign of toxic impurities. Toxic ions are sorbed by the resin, toxic impurities are released in concentrated form as alkaline or acidic wastewater, which are mutually neutralized and subjected to reagent purification or disposal.
Biological treatment wastewater is based on the ability of microorganisms to use dissolved and colloidal organic compounds as a source of nutrition in their life processes. In this case, organic compounds are oxidized to water and carbon dioxide.
Biological treatment is carried out either in natural conditions (irrigation fields, filtration fields, biological ponds), or in special structures - aeration tanks, biofilters. Larotenki - These are open tanks with a system of corridors through which wastewater mixed with activated sludge slowly flows. The effect of biological treatment is ensured by the constant mixing of wastewater with activated sludge and the continuous supply of air through the aeration tank aeration system. The activated sludge is then separated from the water in settling tanks and sent back to the aeration tank. Biological filter is a structure filled with loading material through which wastewater is filtered and on the surface of which a biological film develops, consisting of attached forms of microorganisms.
Large industrial enterprises have various production facilities, which produce different compositions of wastewater pollution. The water treatment facilities of such enterprises are designed as follows: individual production facilities have their own local treatment facilities, the hardware of which takes into account the specifics of contaminants and completely or partially removes them, then all local wastewater is sent to the homogenizing tanks, and from them to a centralized treatment system. Other options for the water treatment system are possible, depending on specific conditions.