Introduction

Energy and environment

Wastewater characteristics

Justification for the choice of a wastewater treatment scheme

Wastewater treatment scheme

Conclusion

Literature

application

Introduction

For millennia, mankind exerted an extremely limited impact on the environment, but in the second half of the twentieth century, due to a sharp increase in anthropogenic load on it and severe environmental consequences, the most acute problem of environmental protection, finding a balance between ensuring the economic and social needs of society and preserving environment. In the context of the growing threat to the environment and public health, practically all countries of the world have adopted legislative acts limiting and regulating anthropogenic pressure on nature. At the same time, new technologies are being developed and introduced that exclude or minimize the harmful effects of production processes on air, water and soil.

The problem of utilization of rinse water is relevant for large water treatment plants in Russia. In the process of water treatment at filtering stations, a large amount of wash water for filters and contact clarifiers is formed (15 - 30% of the volume of treated water). The rinse water discharged from the stations is characterized by high concentrations of aluminum, iron, suspended solids, oxidizability, which negatively affects the state of water bodies receiving this type of wastewater.

According to SNiP 2.04.02-84, the wash water should be sent for reuse, however, in practice, it is not possible to completely utilize the wash water in this way for a number of reasons: worsening of flocculation and sedimentation processes, and a reduction in the duration of filter cycles. At present, most (~ 75%) of rinsing water is either discharged into the domestic sewer, or, after preliminary settling (or without it), into a natural reservoir. At the same time, in the first case, the load on the sewer networks and biological treatment facilities increases significantly, their normal operation is disrupted. In the second case, natural water bodies are polluted with toxic sediment, which negatively affects their sanitary condition.

Thus, new approaches are needed that exclude environmental pollution and allow obtaining an additional amount of treated water without increasing water intake.

In this work, we investigate the scheme of wastewater treatment of thermal power plants and their impact on the environment.

Problems of this work: study of wastewater emissions from industrial enterprises, the impact of wastewater on the environment.

1. Energy and environment

The modern period of human development is sometimes characterized through three parameters: energy, economics, ecology.

Energy takes a special place among these indicators. It is a defining indicator for both the economy and the environment. The economic potential of states and the well-being of people depend on energy indicators.

The demand for electricity and heat is growing every year, both in our country and abroad, respectively.

There is a need to increase the capacity of existing industries and modernize equipment in order to increase the production of energy and heat.

Meanwhile, getting more electricity negatively affects natural resources.

Large scale power generation affects:

atmosphere;

hydrosphere;

lithosphere;

biosphere.

At present, energy needs are met mainly from three types of energy resources: fossil fuel, water and the atomic nucleus. The energy of water and nuclear energy is used by humans after converting it into electrical energy.

Main types of electricity production in the Russian Federation

The modern energy complex of the Russian Federation includes almost 600 power plants with a unit capacity of over 5 MW. The total installed capacity of power plants in Russia is 220 thousand MW. The installed capacity of the park of operating power plants by types of generation has the following structure: 21% are hydropower facilities, 11% are nuclear power plants and 68% are thermal power plants.

Thermal energy

Thermal power plants are a complex of structures and equipment for generating electricity and heat.

Thermal power plants are distinguished:

By the degree of loading:

· Basic;

· Peak.

By the nature of the fuel consumed:

· On solid;

· Liquid;

· Gaseous.

These types of power plants, of high capacity, require a huge amount of water to cool the steam.

In this case, the incoming cooling water passes through the cooling devices and returns to the source.

In the Russian Federation, steam turbine types of thermal power plants are used.

Energy Yekaterinburg

The main type of electric power development in Yekaterinburg will fall on thermal power plants.

Energy saving in Yekaterinburg is provided by 6 thermal power plants and 172 boiler houses of various capacities from 0.1 to 515 Gcal / hour.

The installed electric capacity of the CHPP is 1,906 MW (generation of more than 6.1 billion kWh per year).

The total heat capacity of power sources is 9,200 Gcal / hour. More than 19 million Gcal of thermal energy are produced per year, including:

56% - at the Sverdlovenergo stations;

39% - boiler houses of industrial enterprises;

5% - by municipal boiler houses.

The annual fuel consumption is 3 million tons of fuel equivalent, more than 99% of which is natural gas, the rest is coal, fuel oil (the latter is used as a backup fuel).

The length of the main heating networks in Yekaterinburg is 188 km, distribution and district heating networks - more than 3200 km.

Wastewater characteristics

It is customary to call waste water fresh water that has changed its physical, chemical and biochemical properties as a result of household and industrial activities of a person. By origin, wastewater is divided into the following classes: domestic, industrial and rainwater.

The degree of uniformity of distribution (frequency) of the polluting component.

Table 1 Composition and concentration of contaminants in waste water from CHPP

Indicators		Wastewater receiver water quality	Hydraulic ash removal system
			Before cleaning	After cleaning	Cleaning method	Further use		Increase in the concentration of water pollutants in wastewater after treatment
Suspended substances
Petroleum products					There are no treatment facilities	Discharge into water bodies
Total alkalinity	meq / dts3
General hardness	meq / dts3
Sulphates
Dry residue

Table 2 Indicators of waste water from CHP

Indicators	Substance concentration	Before cleaning	After cleaning	Cleaning method	Further use	Increase in the concentration of water pollutants in wastewater before treatment
Suspended substances
Petroleum products		8.64 × 10-4 / 1.44 × 10-4	2.16 × 10-3 / 0.36 × 10-3	8.64 × 10-41.44 × 10-4
Total alkalinity	meq / dts3
General hardness	meq / dts3
Sulphates
		2.05 × 10-4 / 0.34 × 10-4	2.16 × 10-4 / 0.36 × 10-4	2.05 × 10-4 / 0.34 × 10-4
		6.48 × 10-4 / 1.08 × 10-4	8.64 × 10-4 / 1.44 × 10-4	6.48 × 10-4 / 1.08 × 10-4
Dry residue

Justification for the choice of a wastewater treatment scheme

As we have already found out, the main type of electricity development in Yekaterinburg is thermal power plants. Therefore, in this work we analyze the impact of the development of thermal power plants and their impact on the environment.

The development of heat power engineering has an impact on:

atmosphere;

hydrosphere;

lithosphere;

biosphere.

Currently, this impact is acquiring a global character, affecting all structural components of our planet.

The most important factors in the functioning of the environment is the living matter of the biosphere, which plays an essential role in the natural circulation of almost all substances.

The impact of TPPs on the environment

Nitrogen compounds practically do not interact with other substances in the atmosphere and their existence is almost unlimited.

Sulfur compounds are a toxic gaseous release from a thermal power plant, and when in the atmosphere, in the presence of oxygen, it is oxidized to SO 3 and reacts with water, and forms a weak solution of sulfuric acid.

In the process of combustion in an atmosphere of atmospheric oxygen, nitrogen, in turn, forms a number of compounds: N 2 O, NO, N 2 O 3, NO 2, N 2 O 4 and N 2 O 5.

In the presence of moisture, nitric oxide (IV) easily reacts with oxygen, forming HNO 3.

The growth of emissions of toxic compounds into the environment, first of all, affects the health of the population, worsens the quality of agricultural products, reduces productivity, affects the climatic conditions of certain regions of the world, the state of the ozone layer of the Earth, and leads to the death of flora and fauna.

Physicochemical cleaning methods

These methods are used for cleaning from dissolved impurities, and in some cases from suspended solids. Many methods of physicochemical purification require preliminary deep separation of suspended solids from wastewater, for which the coagulation process is widely used.

At present, in connection with the use of circulating water supply systems, the use of physical and chemical methods of wastewater treatment is significantly increasing, the main of which are:

flotation;

ion exchange and electrochemical cleaning;

hyperfiltration;

neutralization;

extraction;

evaporation;

evaporation, evaporation and crystallization.

Industrial waste water

Industrial wastewater is mainly polluted with industrial waste and emissions. The quantitative and qualitative composition of such effluents is diverse and depends on the industry sector and its technological processes. By composition, wastewater is divided into three main groups, containing:

Inorganic impurities (including toxic ones);

Organic impurities;

Inorganic and organic contaminants.

Waste water from thermal power plants

Wastewater treatment methods

Wastewater treatment - treatment of wastewater with the aim of destroying or removing harmful substances from it.

Wastewater treatment methods can be divided into:

mechanical;

chemical;

physical and chemical;

biological.

Wastewater treatment scheme

Wastewater treatment is carried out sequentially.

At the initial stage, wastewater is purified from undissolved contaminants, and then from dissolved organic compounds.

Industrial wastewater is treated with chemical treatment (chemical production, thermal power plants).

Physicochemical methods of wastewater treatment can be carried out before biochemical treatment and after biochemical treatment.

Disinfection is usually carried out at the end of the waste water treatment process.

power plant waste water

Figure: 1. Scheme of mechanical and biochemical wastewater treatment

The sediment is fermented in digesters, dewatered and dried in sludge pads.

Mechanical cleaning consists in filtering waste liquid through grates.

Contaminants caught on the screens are crushed on special crushers and returned to the stream of purified water before or after the screens.

Biochemical cleaning is carried out by aerobic microorganisms.

The sediment from the secondary clarifiers is also sent to digesters.

Chlorine is used to disinfect water.

Disinfection of water takes place in contact tanks.

Figure: 2. Scheme of mechanical and biochemical wastewater treatment

In this scheme, aerotanks are used for biochemical treatment.

The principle of water purification in them is the same as in biological filters. Instead of a biological film, activated sludge is used here, which is a colony of aerobic microorganisms.

According to this scheme, the precipitate is dehydrated in vacuum filters and dried in thermal ovens.

The scheme of chemical treatment of industrial wastewater, along with the structures used for mechanical treatment of wastewater, includes a number of additional structures: reagents, as well as mixing them with water.

Conclusion

In this work, we investigated wastewater treatment schemes.

It is customary to call waste water fresh water that has changed its physical, chemical and biochemical properties as a result of household and industrial activities of a person. By origin, wastewater is divided into the following classes: domestic, industrial and rainwater.

Industrial waste water is generated during the production activities of enterprises, factories, complexes, power plants, car washes, etc.

The main characteristics of wastewater are:

Types of pollution and their concentration (content) in wastewater;

The amount of wastewater, the rate of their entry, consumption;

The degree of uniformity of distribution (frequency) of the polluting component.

As we found out, the production of electricity leads to massive emissions of harmful compounds, which in turn adversely affect the atmosphere, hydrosphere, lithosphere and biosphere.

In the appendices, there are regulatory indicators for the composition and lists of substances that are discharged into the reservoir.

To reduce emissions of harmful substances into the environment, humanity needs to switch to alternative energy sources.

Alternative energy sources are aimed at solving global - environmental problems.

The cost of alternative energy sources is significantly lower than the cost of traditional sources, and the construction of alternative power plants pays off faster. Alternative energy sources will save the country's fuel resources for use in other industries, so the economic reason is being solved here.

Alternative energy sources will help preserve the health and life of many people.

Literature

1. V.I. Kormilitsyn, M.S. Tsitskshivili, Yu.I. Yalamov "Fundamentals of Ecology", publishing house - Interstyle, Moscow 1997.

2. N.A. Voronkov "Ecology - General, Social, Applied", publishing house - Agar, Moscow 1999.

3. V.M. Garin, I.A. Klenov, V.I. Kolesnikov "Ecology for technical universities", publishing house - Phoenix, Rostov-on-Don 2001.

4. Richter L.A. Thermal power plants and protection of the atmosphere. - M .: Energiya, 1975.-131 p.

5. Romanenko V.D. et al. Methodology for environmental assessment of surface water quality according to the relevant criteria. - K., 1998.

6. Guidelines for organizing monitoring of the state of the natural environment in the area of \u200b\u200bthe NPP location. Control over radioactive contamination of the natural environment in the vicinity of NPP / Ed. K.P. Makhonko. - Obninsk: NPO Typhoon, 1989. - 350 p.

7. Semenov I.V. et al. Monitoring in the system of ensuring the ecological safety of hydraulic engineering facilities // Hydraulic engineering. - 1998. - No. 6.

8. Skalin F.V., Kanaev A.A., Koop L.Z. Energy and Environment. - L .: Energoizdat, 1981 .-- 280 p.

9. Tarkhanov A.V., Shatalov V.V. New trends in the development of the world and Russian mineral resource base of uranium // Mineral raw materials. Geological and economic series. - M .: VIMS, 2008. - No. 26. - 79 p.

10. Explanatory dictionary of environmental terms / G.А. Tkach, E.G. Bratuta and others - K .: 1993 - 256 p. Tupov V.B. Environmental protection from noise in the energy sector. - M .: MPEI, 1999 .-- 192 p. Khodakov Yu.S. Nitrogen oxides and heat power engineering. - M .: OOO "EST-M", 2001. - 370 p.

application

List of pollutants removed from wastewater at biological treatment facilities

Substance

Max. conc. for a biologist. purification mg / l

Removal efficiency,%

When clearing, wastewater into a water body of drinking and cultural and household water use

When clearing, wastewater into a water body for fishery water use

Hazard Class

Hazard Class

Acrylic acid

Acrolein

Allyl alcohol

Aluminum

Ammonium nitrogen (ion) xx)

Acetaldehyde

Benzoic acid

Butyl acrylate

Butyl acetate

Butyl alcohol is normal.

- "- secondary

- "- tertiary

Vinyl acetate

Hydrazine

Hydroquinone

Glycosin

Glycerol

Dibutyl phthalate

Dimethylacetamide

Dimethylphenylcarbinol

Dimethylphenol

Dinitrile adipic acid

Dicyandiamide

Diethanolamide

Diethylamine

IronFe + 3

Fats (grows and animals)

Normalized by BOD

normalized by BOD

Isobutyl alcohol

Isopropyl alcohol

Caprolactam

Carbomethyl cellulose

Carbomol

Crotonic aldehyde

Normalized by BOD

Maleic acid

Manganese2 +

Butyric acid

Methacrylamide

Methacrylic acid

Methyl methacrylate

Methylstyrene

Methyl ethyl ketone

Molybdenum

Lactic acid

normalized by BOD

Monoethanolamine

Ethylene glycol monoethyl ether

Urea (carbamide)

Formic acid

Oil and oil products in sol. and emulsifier. form

Nitrobenzene

Nitrates (by NO3)

Nitrite (by NO2)

Octanol (octyl alcohol)

Pyrocatechol

Polyacrylamide

Polyvinyl alcohol

Propylene glycol

Propyl alcohol

Resorcinol

Carbon disulfide

Syntamide

Surfactant (anionic)

Strontium

Sulfides (sodium)

Thiourea

Tricresyl phosphate

Triethanolamine

Acetic acid

Formaldehyde

Phosphatex)

tox san tox

2 (by P) 00.5-0.2

Phthalic acid

Fluorides (anion)

Chromolan

Cyanides (anion)

Ethanol

Emukril C

Etamon DS

2-ethylhexanol

Ethylene glycol

Ethylene chlorohydrin

x) LPV - the limiting hazard indicator: "s-t" - sanitary and toxicological; "tox" - toxicological; "org." - organoleptic; "common." - general sanitary; "fish-host." - fishery; "san" - sanitary. xx) the removal efficiency of ammonia nitrogen and phosphorus is given for the existing conventional biological treatment technology. When using special technologies (schemes with nitrification-denitrification, reagent or biological removal of phosphates, etc.), requiring the reconstruction of treatment facilities, the removal efficiency can be increased to 95-98%. MPC for fishery reservoirs depends on the trophicity of reservoirs, a dash means the lack of data

LIST of pollutants not removed from wastewater at biological treatment plants

	Substance	When discharged into a water body of household drinking and cultural and household water use			When discharged into a fishery water use object
				Hazard Class			Hazard Class
	Anisole (methoxybenzene)
	Acetophenone
	Butylbenzene
	Hexachloran (hexachlorocyclohexane)
	Hexachlorobenzene
	Hexachlorobutadione
	Hexachlorobutane
	Hexachlorocyclopentadiene
	Hexachloroethane
	Hexogen
	Dimethyldioxane
	Dimethyldithiophosphate
	Dimethyldichlorovinyl phosphate
	Dichloroaniline
	Dichlorobenzene
	Dichlorobutene
	Dichlorohydrin
	Dichlorodiphenyltrichloroethane (DDT)
	Dichloronaphthoquinone
	Sodium dichloropropionate
	Dichlorvos
	Dichloroethane
	Diethylaniline
	Diethylene glycol
	Diethyl ether
	Diethyl ester of maleic acid
	Diethylmercury
	Isopropylamine
	Karbofos
	B-mercaptodiethylamine
	Methyl nitrophos
	Nitrobenzene
	Nitrochlorobenzene
	Pentaerythritol
	Petrolaum (mixture of solid hydrocarbons)
	Picric acid (trinitrophenol)
	Pyrogallol (trioxybenzene)
	Polychloropinene
	Polyethyleneimine
	Propyl benzene
	Tetrachlorobenzene
	Tetrachloroheptane
	Tetrachloromethane (carbon tetrachloride)
	Tetrachlornonane
	Tetrachloropentane
	Tetrachloropropane
	Tetrachlorundecane
	Tetrachloroethane
	Thiophene (thiofuran)
	Tributyl phosphate
	Triethylamine
	Phosphamide
	Furfural
	Chlorobenzene
	Chloroprene
	Chlorophos
	Chlorocyclohexane
	Ethylbenzene
	Cyclohexane
	Cyclohexanol
	Sulphates

List of substances and materials prohibited for discharge into the sewage systems of settlements

1. Substances and materials that can clog pipelines, wells, gratings or be deposited on their walls:

metal shavings;

construction waste and garbage;

solid household waste;

industrial waste and sludge from local (local) treatment facilities;

floating substances;

insoluble fats, oils, resins, fuel oil, etc.

colored wastewater with an actual dilution ratio exceeding the standard indicators of the general properties of wastewater by more than 100 times;

biologically hard surfactants (surfactants).

Substances that have a destructive effect on the material of pipelines, equipment and other structures of sewage systems:

alkalis, etc.

Substances that can form toxic gases, explosive, toxic and flammable gases in sewer networks and structures:

hydrogen sulfide;

carbon disulfide;

carbon monoxide;

hydrogen cyanide;

vapors of volatile aromatic compounds;

solvents (gasoline, kerosene, diethyl ether, dichloromethane, benzenes, carbon tetrachloride, etc.).

Concentrated and mother liquors.

Wastewater with a fixed toxicity category "hypertoxic";

Wastewater containing microorganisms that cause infectious diseases.

Radionuclides, the discharge, removal and neutralization of which is carried out in accordance with the "Rules for the Protection of Surface Waters" and the current radiation safety standards

Average characteristics of the quality of household wastewater discharged by subscribers of the housing stock of settlements

	List of pollutants	Average characteristic of domestic wastewater (concentration, mg / l)
	Suspended substances
	BOD full
	Ammonia nitrogen
	Sulphates
	Dry residue
	Petroleum products
	Surfactant (anionic)
	Iron total
	Aluminum
	Manganese
	Phosphorus phosphates

Note: If necessary, the data given in the table can be revised and corrected based on the conducted field studies.

waste water mechanical treatment

Wastewater discharged from the territory of industrial enterprises, according to its composition, can be divided into three types:

industrial - used in the technological process of production or obtained during the extraction of minerals (coal, oil, ores, etc.);

household - from sanitary facilities of production and non-production buildings and buildings;

atmospheric - rain and snow melting.

Contaminated industrial wastewater contains various impurities and is divided into three groups:

contaminated mainly with mineral impurities (metallurgical, machine-building, ore and coal mining enterprises);

contaminated mainly with organic impurities (enterprises of meat, fish, dairy and food, chemical and microbiological industries, plants for the production of plastics and rubber);

contaminated with mineral and organic impurities (enterprises of the oil production, oil refining, petrochemical, textile, light, pharmaceutical industries).

By concentrationindustrial waste water pollutants are divided into four groups:

• 1 - 500 mg / l;
• 500 - 5000 mg / l;
• 5000 - 30,000 mg / l;

more than 30,000 mg / l.

Industrial waste water may vary by the physical properties of pollutants their organic products (for example, by boiling point: less than 120, 120 - 250 and more than 250 ° C).

By the degree of aggressiveness these waters are divided into mildly aggressive (slightly acidic with pH \u003d 6h6.5 and slightly alkaline pH \u003d 8h9), highly aggressive (strongly acidic with pH6 and strongly alkaline with pH\u003e 9) and non-aggressive (with pH \u003d 6.5h8).

Uncontaminated industrial wastewater comes from refrigeration, compressor and heat exchangers. In addition, they are formed when the main production equipment and products are cooled.

At different enterprises, even with the same technological processes, the composition of industrial wastewater is very different.

To develop a rational drainage scheme and assess the possibility of re-using industrial wastewater, their composition and drainage regime are studied. At the same time, the physicochemical indicators of wastewater and the mode of entering the sewer network not only of the general flow of an industrial enterprise, but also of wastewater from individual workshops, and, if necessary, from individual devices are analyzed.

The analyzed wastewater should determine the content of components specific to this type of production.

The operation of TPPs is associated with the use of natural water and the formation of liquid waste, some of which, after processing, are sent to the cycle again, but the main amount of consumed water is discharged in the form of wastewater, which include:

Cooling systems waste water;

Slurry, regeneration and flushing waters of water treatment plants and condensate purifiers;

Wastewater from hydraulic ash removal systems (HSS);

Waters contaminated with oil products;

Spent solutions after cleaning stationary equipment and its conservation;

Water from washing the convective surfaces of TPPs burning fuel oil;

Water from hydraulic cleaning of premises;

Rain and melt water from the territory of the power facility;

Waste water from dewatering systems.

The compositions and quantities of the listed effluents are different. They depend on the type and capacity of the main equipment of the TPP, the type of fuel used, the quality of the source water, water treatment methods, the perfection of operating techniques, etc. When entering watercourses and reservoirs, sewage impurities can change the salt composition, oxygen concentration, pH value, temperature and others. water indicators that complicate the processes of self-purification of water bodies and affect the viability of aquatic fauna and flora. To minimize the effect of waste water impurities on the quality of surface natural waters, standards for maximum permissible discharges of harmful substances have been established, based on the conditions for not exceeding the maximum permissible concentrations of harmful substances in the control section of the reservoir.

All of the listed types of wastewater from TPPs are divided into two groups. The first group includes effluents from the circulating cooling system (RCC), TLU and hydraulic ash removal (HSS) of operating TPPs, characterized by either large volumes or increased concentration of harmful substances that can affect the water quality of water bodies. Therefore, these effluents are subject to mandatory control. The remaining six types of waste water from TPPs must be reused after treatment within the TPP or by agreement at other enterprises, or they may be injected into underground layers, etc.

The water supply system has a significant impact on the amount and composition of industrial wastewater: the more circulating water is used for technological needs in the same or other operations of a given or a neighboring enterprise, the less the absolute amount of wastewater and the greater the amount of pollution it contains.

The amount of industrial wastewater is determined depending on the productivity of the enterprise according to the enlarged standards of water consumption and disposal for various industries.

During the operation of the TLU, wastewater is generated in the amount of 5 - 20% of the treated water consumption, which usually contains sludge consisting of calcium and magnesium carbonates, magnesium, iron and aluminum hydroxide, organic substances, sand, as well as various salts of sulfuric and hydrochloric acids. Taking into account the known maximum permissible concentration of harmful substances in water bodies, the effluents of the TLU should be properly treated before they are discharged.

5.21.1. The main problems of wastewater in the energy sector

The operation of modern thermal power plants is associated with the appearance of a number of liquid waste water. These include water after cooling of various devices - turbine condensers, oil and air coolers, moving mechanisms, etc .; waste water from hydraulic ash removal systems (HSS); spent solutions after chemical cleaning of heat-power equipment or its conservation; regeneration and sludge water from water treatment plants; oil-contaminated sewage; solutions arising from washing the external heating surfaces, mainly of air heaters and water economizers of boiler units operating on sulphurous fuel oil. The compositions of all these effluents and their quantities are very different; they are determined by the type of TPP and the equipment installed on it, its capacity, the type of fuel used, the composition of the source water, the adopted method of water treatment in the main production and other less significant circumstances. In recent years, significant work has been carried out in the energy sector to reduce the amount of wastewater, the content of various pollutants in them, and to create circulating water use systems. The ways of creating completely internal drainage thermal power plants are outlined, which requires solving a number of complex technical and organizational problems, as well as certain capital investments.

The creation of TPPs that do not pollute natural water bodies is possible in two ways - deep purification of all effluents to maximum permissible concentrations (MPC) or the organization of wastewater reuse systems. The first way is not promising, since the bodies of water bodies protection are constantly increasing the requirements for the degree of purification of waters discharged by industrial enterprises. So, several years ago, the purification of effluents from oil products to a residual content of 0.3 mg / l was considered sufficient. Later it was adopted as the maximum permissible concentration of 0.1 mg / l. Now this norm has been reduced to 0.05 mg / l, and it is possible that for fishery reservoirs, it will be further reduced. It should also be borne in mind that the use of new materials and reagents in water treatment technology will also require setting MPC for them. An increase in the depth of wastewater treatment will require a significant increase in costs both for the construction of the corresponding installations and for their operation. All these circumstances make the first way very unpromising. The second way is more realistic - the creation of circulating systems with repeated use of water. At the same time, deep purification of effluents is no longer required; it is enough to bring their quality to a level acceptable for the implementation of the corresponding technological processes. This way gives a significant reduction in water consumption, that is, the amount of water that the company takes from the water source sharply decreases. In addition, this approach sharply reduces the number of issues to be agreed with the authorities that control the quality of effluents. That is why the development of drainless TPPs is going on.

The amount of water formed after cooling the equipment is mainly determined by the amount of exhaust steam entering the turbine condensers. Water after cooling the condensers of turbines and air coolers, as a rule, carry only the so-called thermal pollution, since their temperature is 8-10 ° C higher than the temperature of water in the water source. However, in some cases, cooling waters can introduce foreign substances into natural water bodies. This is due to the fact that the cooling system also includes oil coolers, the violation of the density of which can lead to the penetration of oil products (oils) into the cooling water.

The most reliable way to solve this problem is to separate the cooling of such devices as oil coolers and the like into a special autonomous system, separated from the cooling system of "clean" devices.

At TPPs using solid fuels, significant amounts of ash and slag are usually removed hydraulically, which requires a lot of water. Thus, a TPP with a capacity of 2400 MW, operating on Ekibastuz coal, burns up to 2500 t / h of this fuel, while forming up to 1000 t / h of ash and slag. To evacuate this amount from the station to ash and slag fields, at least 5000 m 3 / h of water is required. Therefore, the main direction in this area is the creation of a recirculating system of the GZU, when the clarified water freed from ash and slag particles is again sent through the return pipeline to the TPP to perform the same function. Part of the water during this circulation leaves the system, as it is retained in the pores of the settled ash, enters into chemical compounds with the components of this ash, and also evaporates and in some cases seeps into the ground. At the same time, water flows into the system mainly due to atmospheric precipitation. Therefore, the most important issue in the creation of recirculating systems of the MS is to ensure a balance between the flow and consumption of water, which must be taken into account in various technological processes, including ash collection. For example, when using wet ash collectors, the main role in solving this problem is played by the organization of their supply with clarified water. The lack of balance creates the need for a systematic discharge of part of the water from the MS system.

The need to create recirculating systems for hydraulic control systems is also due to the fact that such waters in some cases contain an increased concentration of fluorides, arsenic, vanadium, less often mercury and germanium (Donetsk coals) and some other elements with harmful properties. MS waters also often contain carcinogenic organic compounds, phenols, etc.

Effluents after chemical washing or conservation of heat-power equipment are very diverse in their composition due to the abundance of recipes for washing solutions. In addition to mineral acids - hydrochloric, sulfuric, hydrofluoric, sulfamic, many organic acids are used (citric, orthophthalic, adipic, oxalic, formic, acetic, etc.). Along with them, trilon and various mixtures of acids, which are production waste, are used, and captax, surfactants, sulfonated naphthenic acids, etc. are introduced as corrosion inhibitors. Thiourea is introduced into the copper complex for binding to the copper complex. Preservation solutions contain hydrazine, nitrites, ammonia.

Most of the organic compounds used in flushing solutions are biologically recyclable and, therefore, can be sent together with domestic wastewater to appropriate installations. Before that, it is necessary to remove from the spent washing and conservation solutions toxic substances that have a detrimental effect on the active microflora. These substances include metal nones - copper, zinc, nickel, iron, as well as hydrazine and captax. Trilon refers to biologically "hard" compounds, moreover, it suppresses the activity of biological factors, but in the form of calcium complexes it is permissible in rather high concentrations in wastewater sent for biological processing. All these conditions dictate a specific technology for processing wastewater from chemical treatment of equipment. They should be collected in a container in which the acid mixture is neutralized, and hydrates of iron, copper, zinc, nickel, etc. oxides are precipitated. zinc and nickel are not destroyed even at high pH values. Therefore, to destroy these strong complexes, the precipitation of metals in the form of sulfides is used by introducing sodium sulfide into the liquid.

The precipitation of sulfides or hydrates of oxides occurs slowly, therefore, after adding reagents, the liquid is kept for several days. During this time, complete oxidation of hydrazine with atmospheric oxygen also occurs. Then a clear liquid containing only organic substances and an excess of precipitating reagents is gradually pumped out into the mains of household wastewater.

The vacated container is filled with effluents from the next washing and the deposition operation is repeated. Sediments accumulated after several cleanings are evacuated; these deposits often contain significant amounts of valuable metals that can be recovered by metallurgists. In cases where a TPP is located far from settlements that have devices for biological treatment of domestic wastewater, the clarified liquid can be sent for irrigation of sites or into a closed cooling system as additional water. At TPPs with hydraulic ash removal, wastewater after chemical cleaning of equipment, often even without preliminary precipitation of metals (iron, copper, zinc, etc.), can be discharged into the slurry pipeline. Crushed ash particles have a high absorption capacity in relation to impurities in spent solutions after chemical cleaning of equipment.

Water from washing the outer heating surfaces is formed only at TPPs using sulfurous fuel oils as the main fuel. Ash elements formed during the combustion of fuel oil have a high stickiness and settle mainly on the surface of air heater elements, which, as a result, have to be regularly cleaned. Periodically cleaning is done by washing; the result is a wash fluid containing free sulfuric acid and sulfates of iron, vanadium, nickel, copper and sodium. Other metals are present as minor impurities in this liquid.

Neutralization of these washing solutions is accompanied by the receipt of sludge containing valuable substances - vanadium, nickel, etc.

During the operation of water treatment plants at power plants, effluents arise from the washing of mechanical filters, from the removal of sludge water from clarifiers and as a result of the regeneration of cationic and anionic materials.

The flushing water contains only non-toxic sediments - calcium carbonate, magnesium, iron and aluminum hydroxides, silicic acid, organic, mainly humic substances, clay particles. Since all these impurities are not toxic, these effluents can be discharged after the separation of the sludge into water bodies. At modern thermal power plants, these waters, after some clarification, are returned to water treatment, namely, to its head part.

Regeneration effluent contains a significant amount of calcium, magnesium and sodium salts in the solution.

In order to reduce saline discharges from chemical water purification, various methods of preliminary treatment of water supplied to water purification are proposed. For example, in electrodialysis plants or in reverse osmosis plants, the mineralization of the source water can be slightly reduced. However, the amount of saline effluents even with these methods remains significant, since in all cases pure water is taken, and the salts contained in it are returned to the reservoir with one or another amount of reagents.

It is proposed to replace chemical desalination with evaporators or to use them for evaporation of saline effluents. The installation of evaporators instead of chemical desalination is possible at purely condensing TPPs, but it is very burdensome at TPPs with a high steam output to its industrial consumers. Evaporation of saline wastewater, obviously, does not solve the problem of their removal, but only reduces the volume of objects to be evacuated.

The following scheme of waste treatment seems to be somewhat more attractive: after mixing acidic (from H-cationite) and alkaline (from anionite) wastewater, they are treated with lime and soda to precipitate calcium and magnesium ions. The solution after separation from the formed sediments contains only sodium salts, chlorides and sulfates. This solution is subjected to electrolysis, thus obtaining acidic and alkaline solutions. They are sent instead of imported acids and alkalis for the regeneration of the corresponding filters. Calculations show that in this way the amount of excess salts can be reduced several times.

Previous

Technological cycles of production of chemical, metallurgical, energy and defense enterprises use, in addition to basic materials and raw materials, ordinary water, which plays an important role in production technology. Large volumes of fresh water used for the preparation of reagent solutions and as auxiliary cooling operations contain simply a huge amount of chemical impurities and additives that make such water dangerous even in the form of industrial effluents.

The problem of purifying such waters, their use in the further technological cycle or discharge into the general sewage system, today, is fully handled by the equipment for chemical wastewater treatment, which provides not only the preparation of water to the standards of domestic wastewater, but even bringing the purification to standards of purified fresh water suitable for technical use.

The main methods of chemical treatment of industrial wastewater

Chemical methods of industrial wastewater treatment are today mainly used to bind and remove hazardous chemical elements from the volume of industrial water and bring the main parameters of such wastewater to the standards, allowing in the future to carry out conventional biological treatment.

Literally in the process of such cleaning, the main types of chemical reactions are used:

• Neutralization of hazardous compounds and elements;
• Oxidative reaction;
• Reduction reaction of chemical elements.

In the technological cycle of treatment facilities of industrial enterprises, chemical treatment is applicable:

• To obtain purified industrial water;
• Purification of industrial effluents from chemical compounds before discharge into the sewage system for further biological treatment;
• Extraction of valuable chemical elements for further processing;
• When carrying out additional treatment of water in sedimentation tanks for discharge into open reservoirs.

Chemical treatment of waste water before discharge into the general sewage system can significantly increase safety and speed up the process of biological treatment.

Industrial wastewater neutralization

The majority of industrial enterprises using chemical treatment of industrial wastewater most often use in their treatment facilities and complexes means of neutralizing acid and alkaline indicators of water to an acceptable acidity level of 6.5–8.5 (pH) for further processing. A decrease or, on the contrary, an increase in the level of acidity of effluents allows further use of the liquid for technological processes, since such an indicator is no longer dangerous for humans.

Water brought to such an indicator can be used for the technological needs of enterprises, in auxiliary industries or for further purification using biological agents.

It is important that chemical normalization of water carried out at enterprises effectively neutralized acids and alkalis dissolved in wastewater and prevented them from entering the ground and aquifers.

Excessive amounts of acid and alkali indicators in the discharged waste lead to accelerated aging of equipment, corrosion of the metal of pipelines and valves, cracking and destruction of reinforced concrete structures of filtering and treatment plants.

In the future, to normalize the acid-base balance of waste in sedimentation tanks, tanks and filtration fields, more time is needed to carry out biological treatment, 25-50% more than neutralized wastewater.

Industrial technologies for the neutralization of liquid waste

Carrying out measures for the chemical treatment of liquid waste by neutralization is associated with the alignment of the required indicator of the acidity level of a certain volume of wastewater. The main technological processes involved in neutralization are:

• determination of the level of pollution by chemical compounds of effluents;
• calculation of the dosage of chemicals required for neutralization;
• clarification of water to the required level of norms for liquid waste.

The selection of equipment for cleaning means, its location, connection and operation depends, first of all, on the level of pollution and the required volumes of waste treatment.

In some cases, mobile chemical treatment units are sufficient for this, providing cleaning and neutralization of a relatively small amount of liquid from the storage of the enterprise. And in some cases it is required to use a permanent chemical cleaning and neutralization unit.

The main type of technological equipment for such stations is a flow-through cleaning unit or a contact type. Both installations allow you to provide:

• pollution control;
• the possibility of using a scheme for mutual neutralization of acid and alkaline components in the technology;
• the possibility of using the natural process of neutralization in technological reservoirs.

Technological schemes for chemical cleaning by neutralization should provide the ability to remove or remove solid, insoluble sediment particles from the cleaning tanks.

The second important point in the operation of purification plants is the ability to timely adjust the required amount and concentration of reagents for the reaction, depending on the level of pollution.

Usually, in the technological cycle, equipment is used that has several storage tanks, which make it possible to ensure the timely reception, storage, mixing and discharge of effluents brought to the required condition.

Chemical neutralization of effluents by mixing acid and alkaline components

Using the method of neutralizing effluents by mixing acidic and alkaline components allows a controlled neutralization reaction without the use of additional reagents and chemicals. Controlling the amount of acidic and alkaline wastewater discharged allows timely accumulation of both components and dosing during mixing. Usually, the daily volume of discharges is used for the continuous operation of this type of treatment plant. Each type of waste is checked and, if necessary, brought to the required concentration by adding a volume of water or determining the volume of the proportion for the cleaning reaction. Directly at the treatment plant, this is carried out in the storage and control tanks of the station. The use of this method requires the correct chemical analysis of the components of the acid and alkaline components, carrying out a salvo or multi-stage neutralization reaction. For small enterprises, the use of this method can be carried out both in local treatment facilities of a workshop or site, and with the help of a treatment plant as a whole.

Purification by adding reagents

The method of cleaning liquid waste with reagents is used mainly for the purification of waters containing a large amount of contaminants of one type, when the normal ratio of the alkaline and acid components in the water is significantly in one direction.

Most often this is necessary when the contamination has a pronounced appearance and cleaning by mixing does not give results or is simply irrational due to the increased concentration. The only and most reliable method of neutralization in this case is the method of adding reagents - chemicals that enter into a chemical reaction.

In modern technology, this method is most often used for acidic wastewater. The simplest and most effective method of neutralizing acid is usually the use of local chemicals and materials. The simplicity and efficiency of the method lies in the fact that waste, for example, from blast furnace production, perfectly neutralizes pollution with sulfuric acid, and slag from thermal power plants and central heating plants is often used to add to tanks with acid waste.

The use of local materials can significantly reduce the cost of the cleaning process, because slag, chalk, limestone, dolomite rocks perfectly neutralize a large amount of heavily polluted wastewater.

Waste from blast furnace production and slag from thermal power plants and central heating plants does not require additional preparation, except for grinding, the porous structure and the presence of many compounds of calcium, silicon and magnesium in the composition allow the use of materials without preliminary treatment.

Chalk, limestone and dolomite used as reagents must undergo preparation and grinding. In addition, for cleaning in some technological cycles, the preparation of liquid reagents is used, for example, using lime and ammonia solution of water. In the future, the ammonia component perfectly helps in the process of biological water purification.

Wastewater oxidation method

The wastewater oxidation method makes it possible to obtain wastewater toxicity that is safe in its characteristics in hazardous chemical industries. Most often, oxidation is used to obtain effluents that do not require further solids extraction and can be discharged into the general sewer system. Chlorine-based oxidizers are used as additives and are the most popular cleaning materials today.

Materials based on chlorine, sodium and calcium, ozone and hydrogen peroxide are used in a multi-stage wastewater treatment technology, in which each new stage can significantly reduce toxicity by binding hazardous toxic substances into insoluble compounds.

Oxidation plants with multi-stage purification systems make this process relatively safe, but the use of toxic oxidants such as chlorine is gradually being replaced by safer, but no less effective, waste oxidation methods.

High-tech methods of wastewater treatment include methods that use new developments in their technological cycle, which make it possible, using specific equipment, to purify a wide range of pollutants from harmful and toxic impurities.

The most progressive and promising method of purification is the method of waste ozonization. Ozone, when released into wastewater, affects both organic and inorganic substances, exhibiting a wide spectrum of action. Wastewater ozonation allows:

• discolor the liquid, significantly increasing its transparency;
• shows a disinfecting effect;
• almost completely eliminates specific odors;
• eliminates third-party tastes.

Ozonation is applicable for water pollution:

• petroleum products;
• phenols;
• hydrogen sulfide compounds;
• cyanides and substances derived from them;
• carcinogenic hydrocarbons;
• destroys pesticides;
• neutralizes surfactants.

In addition to this, dangerous microorganisms are almost completely destroyed.

Technologically, ozonation as a cleaning method can be implemented both in local treatment plants and in stationary treatment plants.

The use of various methods of chemical treatment of wastewater leads to a 2 to 5-fold decrease in emissions of substances harmful and hazardous to humans and ecosystems, and today it is chemical treatment that makes it possible to achieve the highest degree of water purification.

In industry, water is used as a raw material and energy source, as a refrigerant, solvent, extractant, for the transportation of raw materials and materials.

In industry, 65 ... 80% of water consumption is consumed for cooling liquid and gaseous products in heat exchangers. In these cases, the water does not come into contact with material flows and is not polluted, but only heats up. Process water is subdivided into environment-forming, washing and reaction water. Environment-forming water is used to dissolve and form slurries, when enriching and processing ores, hydrotransporting products and production wastes; flushing - for flushing gaseous (absorption), liquid (extraction) and solid products and products; reactionary - in the composition of reagents, as well as during distillation and other processes. Process water is in direct contact with the medium. Energy water is used to generate steam and heat equipment, premises, products.

According to its purpose, water in industrial water supply systems can be divided into four categories:

category I water is used for cooling liquid and condensation of gaseous products in heat exchangers without contact with the product; the water heats up and is practically not polluted; only emergency leaks of liquid and gaseous products into water with faulty heat exchangers can be observed, polluting it;

category II water serves as a medium absorbing various insoluble (mechanical) and dissolved impurities; water is not heated (mineral processing, hydrotransportation), but is polluted by mechanical and dissolved impurities;

Waste water is water that has been in domestic, industrial or agricultural use, as well as passed through a contaminated area. Depending on the conditions of formation, wastewater is divided into household (BSV), atmospheric (ASV) and industrial (PSV).

Domestic water is wastewater from sanitary units of industrial and non-industrial buildings and buildings, showers, laundries, canteens, toilets, from washing floors, etc. They contain impurities, of which approximately 58% are organic substances and 42% are minerals.

Atmospheric waters are formed as a result of atmospheric precipitation and flowing down from the territories of enterprises (rain and from melting snow). They are contaminated with organic and mineral substances.

Industrial waste water is used in the technological process of production or obtained during the extraction of minerals (coal, oil, ores, etc.);

With direct-flow water supply to enterprises (Fig. 3.1, a), all water taken from the reservoir (Q ist after participating in the technological process (in the form of waste) returns to the reservoir, with the exception of the amount of water that is irretrievably consumed in the production of Q sweat. wastewater reservoir is.

About sbr \u003d Q ist - Q pot (3.1)

Wastewater, depending on the type of pollution and other conditions, must pass through a treatment plant before being discharged into a reservoir. In this case, the amount of wastewater discharged into the reservoir decreases, since part of the water is discharged with sludge.

With a water supply scheme with sequential use of water (Fig. 3.1.6), which can be two or three times, the amount of discharged wastewater decreases in accordance with losses at all industries and at treatment facilities, i.e.

Fig. 3.1. Water supply schemes for industrial enterprises:

1 - fresh, clean water, not heated; 2 - waste water, heated; 3 - the same, heated and contaminated; 4 - the same, purified; PP, PP-1, PP-2 - industrial enterprises; OS - treatment facilities; Q ist - water supplied from a source for production needs; Q pot, Q pot1 and Q pot2 - water that is irretrievably consumed at industrial enterprises; Q sl - water removed with sludge; Q sbr - water discharged into the reservoir

The reuse of wastewater after appropriate treatment is now widespread. In a number of industries (ferrous metallurgy, oil refining), 90 ... 95% of wastewater is used in circulating water supply systems and only 5 ... 10% is discharged into a reservoir.

To reduce the consumption of fresh water, circulating and closed water supply systems are created. With recycling water supply, the necessary treatment, cooling, treatment and reuse of waste water are provided. The use of recycled water supply allows you to reduce the consumption of natural water by 10 ... 15 times.

The quality of water used for technological processes must be higher than that of water in circulating systems.

If in the recycling water supply system of an industrial enterprise water is a heat carrier and only heats up during use, then before reuse it is pre-cooled in a pond, a spray pool, a cooling tower (Fig. 3.2, a); if water serves as a medium absorbing and transporting mechanical and dissolved impurities, and in the process of use is contaminated with them, then before reuse, waste water is treated at treatment facilities (Fig. 3.2, b); with complex use, wastewater is purified and cooled before reuse (Figure 3.2, c).

Fig. 3.2. Circulation water supply schemes for industrial enterprises:

a - with waste water cooling; b - with wastewater treatment; c - with wastewater treatment and cooling; 1 - fresh, clean, unheated water; 2 - waste water, heated; 3 - also, unheated and contaminated; 4 - the same, purified; 5 - waste water, polluted; b - circulating water; ОУ - cooling units; Q - water supplied for production needs; Q about - circulating water; Q un - water lost for evaporation and entrainment from cooling units (other designations of mc are the same as in Fig. 3.1)

With such recirculating water supply systems, to compensate for irreversible water losses in production, at cooling plants (evaporation from the surface, blown away by the wind, spraying), at treatment facilities, as well as water losses discharged into the sewage system, recharge is carried out from reservoirs and other sources of water supply. The amount of make-up water is determined by the formula

Q source \u003d Q pot + Q un + Q shl + Q sbr. (3.3)

Recharge of recycling water supply systems can be carried out continuously and periodically. The total amount of added water is 5 ... 10% of the total amount of water circulating in the system.

Drainage rates in various industries vary widely. So, for example, when 1 ton of oil is extracted, 0.4 m 3 of waste water is formed, when 1 ton of coal is mined in mines - 0.3 m 3; when smelting 1 ton of steel or cast iron - 0.1 m; in the production of 1 ton of viscose staple fiber - 233 m 3; 1 ton of fertilizers - 3.9 m 3; 1 ton of synthetic surfactants - 1 m; 1 ton of sulfite cellulose - 218 m 3; 1 ton of paper - 37 m 3; 1 ton of cement - 0.1 m 3; 1 ton of linen or silk fabrics - 317 or 37 m 3, respectively; 1 ton of meat - 24 m 3; 1 ton of bread - 3 m 3; 1 ton of oil - 2.6 m 3; 1 ton of refined sugar - 1.2 m 3; in the manufacture of one passenger car - 15.5 m 3; one bus - 80 m 3; one mainline diesel locomotive - 710 m 3. When generating 1 MWh of electricity at thermal and nuclear power plants with recycling water supply systems, an average of 5 m 3 of wastewater is generated.

In the absence of drainage standards, the amount of wastewater is determined according to technological calculations in accordance with the production regulations. The amount of wastewater from large industrial enterprises reaches 200 ... 400 thousand m 3 / day, which corresponds to the amount of wastewater from cities with a population of 1 ... 2 million people.

Industrial waste water is divided into two main categories: polluted and unpolluted (relatively clean).

Uncontaminated industrial wastewater comes from refrigeration, compressor, heat exchangers. In addition, they are formed when the main production equipment and products are cooled.

Contaminated industrial wastewater contains various impurities and is divided into three groups:

contaminated mainly with mineral impurities (metallurgical, machine-building, ore and coal mining; factories for the production of mineral fertilizers, acids, construction products and materials, etc.);

contaminated mainly with organic impurities (enterprises of meat, fish, dairy, food, pulp and paper, chemical, microbiological industries; factories for the production of plastics, rubber, etc.);

contaminated with mineral and organic impurities (enterprises of the oil production, oil refining, petrochemical, textile, light, pharmaceutical industries; factories for the production of canned food, sugar, organic synthesis products, paper, vitamins, etc.).

For an objective assessment of water quality, the indicators are classified according to the nature of the impact of pollutants. Based on the proposed classification, five groups are distinguished, including the following indicators:

quality group (smell, color, temperature, amount of suspended particles);

the presence of organic substances (biochemical oxygen demand (MIC), hydrogen index (pH), oxygen dissolved in water, chemical oxygen demand or bichromate oxidizability (COD), phosphates, nitrates);

the presence of sanitary-toxic substances (chlorides, sulfates, Ca, Mg, Na, K);

the presence of microbiological substances (coli-index, etc.);

the presence of toxic substances.

The last group is divided into four subgroups: low-toxic substances, the maximum permissible concentration of which is in the range of 0.1 ... 0.9 mg / l (ammonium, synthetic surfactants (surfactants), V, Mo, Cr, Fe, Ti);

medium toxic substances, the maximum concentration limit of which is 0.01 ... 0.09 mg / l (nitrites, Zn, Ni, Co);

highly toxic substances, the maximum permissible concentration of which falls in the range of 0.001 ... 0.009 mg / l (Cu, Hg, Cd, phenols);

especially poisonous substances with MPC 0.0001 ... 0.0009 mg / l (pesticides, sulfides).

According to the concentration of pollutants, industrial wastewater is divided into four groups: 1 ... 500, 500 ... 5000,

5000 ... 30,000, more than 30,000 mg / l.

Industrial waste water can differ in physical properties of polluting organic products (for example, boiling point: less than 120, 120 ... 250 and more than 250 ° C).

According to the degree of aggressiveness, these waters are divided into slightly aggressive (slightly acidic with pH 6 ... 6.5 and slightly alkaline with pH 8 ... 9), highly aggressive (strongly acidic with pH< 6 и сильнощелочные с pH > 9) and non-aggressive (with pH 6.5 ... 8).