Danger of solid waste disposal. Solid waste disposal process
The cheapest way to get rid of waste is to bury it. This method goes back to the simplest way - throwing something out of the house into a landfill. History has shown that simply throwing out unusable items from the house cannot solve the problem. In the 20th century, we had to move from the spontaneous creation of landfills to the design and implementation of special engineering facilities and landfills for disposal of household waste. The project provides for minimizing damage to the environment and strict compliance with sanitary and hygienic requirements.
Construction of a landfill and disposal of solid waste
Solid waste storage sites contain waste from residential buildings, public buildings and institutions, trade enterprises, public catering establishments, street, garden and park waste, construction waste and some types of solid industrial waste of III - IV hazard class.
Typically, a landfill is constructed where the base can be clay and heavy loam. If this is not possible, a waterproof base is installed, which leads to significant additional costs. The area of the land plot is selected based on its service life (15-20 years) and, depending on the volume of buried waste, can reach 40-200 hectares. The height of waste storage is 12-60 m.
Landfills can be low-load (2-6 t/m²) and high-load (10-20 t/m²). The annual volume of waste received can range from 10 thousand to 3 million m³. The technological process of waste disposal is carried out, as a rule, using the card method, which makes it possible to gradually introduce environmental protection measures without waiting for the completion of the operation of the landfill as a whole. The technology for storing solid waste at landfills involves the installation of waterproof screens to protect groundwater and daily external insulation to protect the atmosphere, soil, and adjacent areas. All work on storing, compacting and isolating solid waste at landfills is carried out mechanized.
Post-cultivation use of solid waste landfill territories is possible by various directions- forestry, recreational (ski hills, stadiums, sports grounds), civil engineering, commercial or industrial creation. The nature of such use and the costs of reclamation must be taken into account at the design stage of the landfill.
The organization and construction of the landfill is carried out in accordance with the legislation in the field of environmental protection and waste management, sanitary-epidemiological and urban planning legislation, as well as in the presence of a positive conclusion of the state urban planning examination for the construction project.
A modern solid waste landfill is a complex of environmental structures designed for the centralized collection, neutralization and disposal of solid waste, preventing the release of harmful substances into the environment, pollution of the atmosphere, soil, surface and groundwater, the spread of rodents, insects and pathogens.
The landfill should include:
- waste disposal site;
- site for a waste sorting and recycling workshop;
- composting site;
- administrative and economic zone;
- engineering structures and communications for the life support of the landfill and environmental safety;
- express laboratory;
- waste radiation control area.
A landfill for waste disposal along its perimeter must have a fence with a height of at least 180 cm. At the landfill along its perimeter, starting from the fence, the following must be placed sequentially:
- ring channel;
- ring road with high-quality hard surface;
- storm drainage trays along the road or ditches.
The building density of the administrative and economic zone of the landfill must be at least 30%. The administrative and economic zone houses:
- administrative premises, laboratory;
- warm parking for special vehicles and mechanisms (shed);
- workshop for routine repair of special vehicles and mechanisms;
- fuel materials warehouse;
- truck scales (at landfills over 100 thousand tons/year);
- checkpoint;
- boiler room (if necessary);
- control and disinfection bath;
- transformer substation (diesel power plant);
- artesian well (reservoir for drinking water);
- treatment facilities (if necessary);
- waste radiation monitoring area, including: automated radiation monitoring frame; site of in-depth radiation survey; a site for equipment storage with a background exceeding the requirements of the NRB (radiation safety standards); place for placing containers (SP 2.6.1.758-99).
The main structure of the landfill is the solid waste storage area. It occupies the main area of the landfill, depending on the volume of solid waste received. The storage area is divided into operational stages, taking into account the provision of waste reception for 3 - 5 years; the first stage includes a start-up complex for the first 1 - 2 years. Operation of the next stage consists of increasing the solid waste embankment to the designed level. The breakdown of the storage area into queues is carried out taking into account the terrain.
Storage areas must be protected from surface water runoff from upstream land masses.
To intercept rain and flood waters, a drainage ditch is designed along the border of the site. Along the perimeter of the landfill on a strip 5 - 8 m wide, it is planned to plant trees, lay engineering Communication(water supply, sewerage), electric lighting masts are installed; in the absence of engineering structures on this strip, cavaliers (warehouses) of soil are poured to be used for isolating solid waste, in any case, no more than 5% of the total area of the landfill.
Legend: A - groundwater, B - dense clay layer, C - plastic layer, D - drainage pipe system, E - geotextile layer, F - gravel, G - drainage layer, H - soil layer, I, J - layers soil where garbage is stored K - drainage ditch (pond).
Processes occurring with solid waste at landfills
During the operation of a solid waste landfill, as well as for a long time after its reclamation, landfill gases are released into the atmospheric air, filtration water (filtrate) is formed, and the geo-indicators of the soil under the body of the landfill change, which leads to an increase in the filtration capacity of the soil and, as a consequence, , to groundwater pollution.
The reactions occurring in the solid waste disposal body under aerobic conditions can be schematically represented as follows:
With further oxidation, the transformation of cellular substance begins:
In a typical landfill, the process of aerobic oxidation most often ends with the formation and accumulation of high concentrations of fatty acids, which limits the process of aerobic decomposition.
Anaerobic biodegradation requires the presence of microorganisms different types members of a mixed population. A group of hydrolytic or acidogenic bacteria provides the initial hydrolysis of the substrate to low molecular weight organic acids and other compounds, including methane.
It is also known that methanogenic bacteria synthesize methane as a result of the reduction of the methyl group of acetic acid and methyl alcohol:
Most of the operating and closed landfills in Russia are not sufficiently equipped with engineering structures to ensure maximum reduction of environmental pollution. The adopted system of unitary collection of solid waste (without separation into organic, inorganic, hazardous, etc. components) also reinforces the shortcomings of waste storage technology at landfills.
The first step in the development of environmental protection measures at solid waste landfills should be the assessment of data on the following characteristics:
- location of the solid waste landfill or landfill;
- landfill type;
- period of operation;
- types, characteristics and quantities of disposed waste;
- storage method;
- thickness of storage layers;
- the presence of screens, drainage and gas collection systems;
- chemical and biological characteristics of the landfill mass;
- hydrogeological conditions of adjacent territories.
In real conditions, obtaining most of the above data is difficult due to a complete or partial lack of information. Information on unauthorized dumps today can only include data on their size and location.
In such a situation, it will be necessary to conduct geotechnical surveys and study landfill masses in laboratory conditions to obtain information on the following issues:
- what is the state of the landfill or solid waste landfill (activity, degree of biodegradation) at the current time and the forecast for the next 20-40 years;
- is there a danger of biogas emissions and fire in the landfill
- is there a danger of contamination of the adjacent areas of the landfill due to leachate emissions;
- will the processes of biodegradation of landfills lead to soil subsidence;
- How effective is the landfill insulation used during its construction and closure?
The behavior of waste in a landfill is complex, as new material is periodically layered at irregular intervals. The process of inerting landfill soil is subject to gradients in temperature, gas concentration, liquid concentration, pH, enzyme activity, and fluid flows. More complex factors include the physicochemical properties of waste, such as water solubility, volatility, molecular size, as well as biological ones: the ability to sorb microorganisms, interspecies interaction of microorganisms, etc.
There are three main stages in the existence of a landfill:
- the first stage is the period of operation of the landfill, which lasts 15-20 years. During this time, the landfill capacity is filled with waste;
- the second stage (it can be conditionally called a bioreactor) is the period after the closure of the landfill until the biochemical processes in the landfill body attenuate. During this period, the processes of biochemical decomposition of matter in the body of the landfill, in the absence of special technological solutions, proceed naturally;
- the third stage is the period of adaptation of the landfill to the environment.
During the operational period, the operation of the landfill is financed by payments from waste suppliers. After the landfill is fully adapted to environmental conditions, it will become a technogenic territory that will become the property of the local administration. The problem is the period of the bioreactor. There is no clear mechanism for regulating financial support for the operation of the landfill during this period to protect the environment from pollution. It is necessary to develop not only protective measures to reduce possible polluting emissions, but also to organize control (acceleration or inhibition) of the processes of natural biodegradation of matter in the landfill body, in order to reduce the time of its natural adaptation and operating costs. The total duration of the bioreactor and adaptation periods can reach hundreds of years. More than one generation of people will change until a solid waste landfill or landfill adapts to the natural landscape.
Currently, in world practice, the most advanced method of storing solid waste, which allows reducing the negative impact on the environment, is the arrangement of “managed” landfills. When choosing a site for waste storage, the characteristics of the area where the solid waste landfill is located are taken into account: climate, topography, geology, hydrological processes, water balance, etc. Preparation of the landfill includes compaction and waterproofing of the bed, installation of a drainage system for drainage of seepage water, laying of pipes for collecting biogas . To manage such a landfill, a number of technological measures are recommended.
There are two approaches to managing the processes of anaerobic inertization of landfill soil to achieve an environmental effect for the long term - through acceleration (intensification) or slowdown (suppression) of biodegradation processes. The first approach is characterized by intense emissions, but adaptation of the landfill to the natural environment in this case takes place short term. With the second approach, the life cycle of the landfill is significantly extended, but pollution of the natural environment by toxic emissions is minimized.
Methods for inerting landfill soil:
- pre-treatment of solid waste before disposal at a landfill, for example, mechanical and biological pre-treatment, mixed disposal (design of composite mixtures), > introduction of a complex of enzymatic preparations before disposal (acceleration of biodegradation), combustion;
- impact on landfill soil, for example, moistening of landfill soil, recirculation of surface wastewater filtrate, waste treatment effluent, etc., forced aeration of landfill soil and through natural air flow (semi-aerobic landfill), introduction of additives into landfill soil - catalyst enzymes, microorganisms, supply of additional nutrients.
Practical experiences using the listed methods in many cases lead to a positive effect, but some problems may still require solutions. For example, residual biogas emissions may remain high, clogging (siltation) of the drainage of an aerobic landfill may occur, hydrocirculation may be difficult (difficulty in achieving high flow rates of liquids through a mass of waste), there is the possibility of the formation of a compacted soil layer, etc.
The choice of a particular technology should be preceded by a comprehensive study of landfill soils. Due to the labor intensity and high cost of field surveys, the importance of research conducted on a laboratory scale is increasing.
As a result of the research, a conclusion is given on the state of the landfill or solid waste landfill in terms of environmental pollution, on the need for control to prevent dangerous situations: biogas explosion, contamination of ground and surface waters with toxic leachate components, deterioration of the sanitary and hygienic situation.
Landfilling waste is, unfortunately, one of the most common methods. It is produced in areas specially designated for this purpose, landfills, and using a certain technology.
Separate landfills for solid waste - municipal solid waste and separate landfills for industrial and construction waste.
The standard landfill is a dug pit, but natural lowlands, ravines and quarries can also be used for these purposes.
Located in relative proximity to settlements, but away from residential areas and bodies of water.
Their area can vary from several tens to hundreds of hectares. The selected area should not be subject to flooding or be swampy.
Special materials and films are laid on the bottom of the boiler as a substrate, which will prevent the penetration of harmful substances into the soil layers and groundwater. In addition, such methods help prevent the excessive spread of rodents and insects in the area. A layer of sand is poured onto the substrate, and only after this comes debris.
The imported waste is distributed evenly over the entire area with the help of other equipment. When the waste layer reaches several meters, it is covered with about a half-meter layer of soil, usually of any composition, easily accessible in the immediate vicinity. Next, the layer of soil is again alternated with a layer of waste, and until such a semblance of a layer cake rises to 40 meters (in accordance with European standards).
For a higher degree of waste compaction, in addition to bulldozers and.
When using a compactor, 2-4 times more waste can be placed in a landfill than when using a conventional crawler bulldozer. Compactors are often equipped with spiked rollers to crush debris.
After reaching the above height threshold, the landfill is closed for further use and reclamation is carried out. The burial is covered with soil, sand, a meter-long layer of soil is poured on top, and the resulting hill is gradually overgrown with grass and bushes.
Often entire mountains are made from garbage; they are compacted with special equipment. equipment, they are covered with soil, when shrinkage occurs (the garbage rots, the temperature inside such formations is high), then the territory is sometimes even equipped with ski resorts.
The main disadvantage of landfilling is that unsorted waste ends up in landfills. Along with household waste, which freely decomposes naturally, there is also plastic, polyethylene and other achievements of the chemical industry that end up in the general heap. However, the period of their decomposition can take tens or hundreds of years. Moreover, landfills also end up hazardous waste, and completely different methods of disposal are provided for them.
Burial does not allow materials to be reused and also eliminates their recycling. In an ideal state of affairs, landfill should be used only for rapidly decomposing food waste, everything else should be recycled or reused.
Opinion: the downside is insufficient control over landfills and widespread violation of waste disposal rules. The business is very profitable and often the owners and managers of such landfills bypass sanitary and other standards. Even a closed landfill often allows trucks with garbage to enter, for a fee, of course.
The invention is intended for recycling organic waste at the places of their direct generation or collection, in particular at solid waste landfills. A landfill for solid waste disposal contains a base and a waste embankment built on it, a forest protection belt located around the landfill at a distance of no more than 50 m and having a width of at least 10 m, and also has a natural or artificial waterproof base connected to a drainage pipe system , connected by a collector, from which drainage flows into the apparatus for its processing as harmful and hazardous waste. On the waterproof base of the landfill, a pyramid-shaped artificial mound of waste is erected with edges covering it with an outer plant layer of bulk soil. The embankment is reinforced with horizontal intermediate insulating layers and inclined ones made, for example, from recycled scrap metal waste in the form of nets or gratings. On the upper layers of the embankment, the insulating layers are made cross-sloping in order to keep waste transporting and landfill servicing equipment at the top of the embankment. The implementation of this invention makes it possible to increase the productivity of the neutralization and disposal of organic waste at the places where they are directly located or collected. 1 ill.
The invention is intended for the disposal of organic waste at the sites of its direct generation or collection, in particular at municipal solid waste landfills.
Currently, there is a need to dispose of these wastes in the field, at landfills for their collection, and in places of their temporary storage. For example, to disinfect an area in the event of livestock death from an epidemic. This requires significant financial costs and more time to neutralize the area and increases the risk of spreading the infection. Similar problems arise when it is necessary to neutralize medical waste.
The closest technical solution The claimed object is an installation according to patent RU No. 2198024, containing a settling tank and a system of containers and filters (prototype).
The disadvantage of the known device is the impossibility of use in the field, the complexity of the process and the need to bring waste to the processing site. The experience of using stationary furnaces for recycling organic waste by burning them has also revealed those disadvantages that limit the period of their operational reliability. The use of stationary stoves in rural areas is inappropriate due to their unprofitability. Since the reliability requirement is one of the main ones, we will consider the disadvantage that must be eliminated first.
The technical result is an increase in the productivity of neutralization and disposal of organic waste at the places of their direct location or collection.
This is achieved due to the fact that the landfill for solid waste disposal, containing a base and an embankment of waste built on it, additionally contains a forest protection belt located around the landfill at a distance of no more than 50 m and having a width of at least 10 m, and also has a natural or an artificial waterproof base connected to a system of drainage pipes connected by a collector, from which drainage flows into an apparatus for processing them as harmful and hazardous waste, and on the waterproof base of the landfill a pyramid-shaped artificial mound of waste is erected with edges covering it with an outer plant layer of bulk soil, and the embankment is reinforced with horizontal intermediate insulating layers and inclined ones made, for example, from recycled scrap metal waste in the form of nets or gratings, and on the upper layers of the embankment the insulating layers are made cross-sloping in order to hold waste transporting and landfill servicing equipment at the top of the embankment.
The drawing shows a diagram of a landfill for solid waste disposal.
The landfill for solid waste disposal contains a forest protection strip 1 (green zone), located around the landfill at a distance of no more than 50 m and having a width of at least 10 m. The landfill has a natural or artificial waterproof base 5 connected to a system of drainage pipes 10 connected by a collector 11, from which drainage flows into apparatus 12 for processing as harmful and hazardous waste. On the waterproof base 5 of the landfill, a pyramid-shaped artificial embankment of waste 3 is erected with edges 4 and 6 covering it with an outer plant layer of bulk soil. The embankment is reinforced with horizontal 2 intermediate insulating layers and inclined 7 made, for example, from recycled scrap metal waste in the form of nets or gratings. Moreover, on the upper layers of the embankment, the insulating layers 8 must be made cross-sloping in order to hold the waste-carrying and landfill-servicing equipment 9 at the top of the embankment.
The landfill for solid waste works as follows.
It is advisable to choose a site for a landfill in clay soil, which, in terms of capacity, can provide waste storage for 20–25 years or more. Considering that in central Russia approximately 600 mm of precipitation falls per year, the base of the site is made in the form of a huge trough 1.5 m deep. At the same time, the filtrate accumulating in the trough will remain within the landfill for a long time and will not be able to pollute reservoirs and groundwater . Destruction and pollution of the lithosphere occurs as a result of the functioning of enterprises in various sectors of the economy: agriculture, mining, transport, ferrous and non-ferrous metallurgy, etc. In the process of transforming the lithosphere, man (according to the beginning of the 90s) extracted 125 billion tons of coal, 32 billion tons of oil, 100 billion tons of other minerals; plowed more than 1,500 million hectares of land.
As a result: more than 20 million hectares of land are swamped and salinized; erosion has destroyed 2 million hectares over the past 100 years; the area of ravines exceeded 25 million hectares; the height of waste heaps reaches 300 m, mountain dumps - 150 m; the depth of mines drilled for gold extraction exceeds 4 km (South Africa), oil wells - 6 km. The vital function of the lithosphere is expressed in the fact that it is the basic subsystem of the biosphere, since all biota rests on the earth's crust. One of the effective solutions to the problem of transition to low-waste technologies may be the introduction of a cleaner production strategy at every industrial enterprise. However, in Russia this strategy is not yet an integral part public policy in the field of environmental protection. Therefore, the introduction of cleaner production can only occur as a result of the proactive activities of an industrial enterprise. To demonstrate such initiative, the management and team of the enterprise must understand the goals pursued by the cleaner production strategy. One of characteristic features The cleaner production strategy is its integrated approach, in which the prevention of environmental pollution is carried out by developing technical measures (projects) interconnected with their environmental and economic assessments, establishing a procedure for their implementation in order to both reduce waste generation and save resources.
For manufacturing processes, cleaner production means using raw materials, water and energy more efficiently, eliminating toxic and hazardous materials from being used, and preventing waste and emissions from occurring where they occur. For finished products and services, a cleaner production strategy aims to reduce their environmental impact throughout the entire life cycle of the product and/or service - from the extraction of raw materials needed to manufacture the product and service, to wear and tear and the eventual disposal of the product and service.
It should be noted that waste disposal outside the enterprise to obtain secondary raw materials, for example, in the form of waste paper, scrap metal, broken glass and other materials that can be used in the technological processes of other enterprises, is of even less importance for of this enterprise compared to other cleaner production activities. This is due to the fact that in this case there is no saving in materials included in the production process for a given enterprise.
When using "end" technologies, a significant role in the pollution and destruction of the lithosphere belongs to production and consumption waste.
Removal solid waste, the number of which is constantly growing, is one of the important and difficult tasks of environmental engineering. On average in Europe there is 350 kg of urban waste per capita per year. In Moscow, for example, more than 2.5 million tons of household waste are generated annually, of which more than 90% are subject to disposal at landfills.
The use of high-load hygienic landfills for solid waste disposal, which provide for the daily covering of new portions of waste brought in with soil, prevents air and water pollution.
In Russia, this is solved by installing waste sorting stations, in which paper, cardboard, ferrous and non-ferrous metals, glass, polymer materials, textiles and food waste. The degree of recycling in this case is about 30% of the solid waste mass. It is more promising, although more expensive, to process waste into compost or burn it, using the resulting heat to supply heat or generate electricity.
A landfill for solid waste disposal, containing a base and a waste embankment built on it, characterized in that it additionally contains a forest protection strip located around the landfill at a distance of no more than 50 m and having a width of at least 10 m, and also has a natural or artificial waterproof a base connected to a system of drainage pipes connected by a collector, from which the drainage flows into the apparatus for processing it as harmful and hazardous waste, and on the waterproof base of the landfill, a pyramid-shaped artificial mound of waste is erected with edges covering it with an outer plant layer of bulk soil, Moreover, the embankment is reinforced with horizontal intermediate insulating layers and inclined ones, made, for example, from recycled scrap metal waste in the form of nets or gratings, and on the upper layers of the embankment the insulating layers are made cross-sloping in order to hold waste transporting and landfill servicing equipment at the top of the embankment.
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Waste disposal must take place in specially organized landfills. Landfills for waste disposal are environmental structures designed for regular centralized collection, removal, neutralization and storage of non-recyclable waste. The number and capacity of landfills for each region are justified by technical and economic calculations.
In the EEC countries, landfills for waste disposal are divided into landfills for hazardous, household and inert waste. This classification is largely conditional, since it is not always possible to draw a clear line between hazardous, non-hazardous and inert waste, since this line can change over time under the influence of various factors.
Disposals of solid household waste in our country must comply with the sanitary rules stipulated by the Hygienic Requirements for the Design and Maintenance of Landfills for Solid Waste (SP 2.1.7.722 - 98), developed by the Research Institute of Human Ecology and Environmental Hygiene named after. A. N. Sysina.
When designing landfills, it is necessary to be guided by SNiP 2.01.28. - 85 “Landfills for neutralization and disposal of toxic waste. General design provisions”, according to which non-recyclable toxic waste of classes I, II and III, i.e. extremely dangerous, highly dangerous and moderately dangerous, are subject to disposal at landfills.
In accordance with current building codes, landfills must have three facilities, which can be located at different sites: 1) a workshop for disinfection and initial processing of waste in order to completely neutralize it or reduce the hazard class, as well as reduce the volume of waste to be buried; 2) waste disposal area; 3) a garage of specialized vehicles intended for transportation and disposal of waste.
When organizing waste disposal sites, the following are important:
* right choice sites;
* creation of necessary engineering structures;
* procedure for filling the landfill with waste;
* depth of waste pre-treatment;
* conducting environmental monitoring;
* control over the formation, collection and transportation of biogas;
* control over the formation, collection and removal of filtrate.
In accordance with modern requirements, waste disposal must be equipped with the following separate engineering structures:
* compacted base made of mineral layers in combination with artificial materials;
* passages;
* facilities for collecting seepage water and purifying it;
* facilities for the collection and utilization of released gas;
* structures to protect the landscape through land reclamation.
Landfills are located in clear, open, well-ventilated, non-flooded areas where the necessary engineering work can be performed. A sanitary protection zone must be created around the landfill at a distance of at least 3000 m.
The landfill can be located at a distance of at least 200 m from agricultural land and transit highways and at least 50 m from forested areas.
The burial site should be located at a slight distance from the main transport routes and be connected to them by a good quality road.
The shortage of space for waste disposal near large cities can be reduced by organizing a network of transfer stations where waste will be sorted, crushed and accumulated by type. This will reduce their volume and use more distant landfills for disposal.
Landfills are located in areas with low-filtration soils (clay, loam, shale, etc.) with a filtration coefficient of no more than 0.00001 cm/s. The groundwater level at its greatest rise should be at least 2 m from the lower level of the buried waste (usually buried 7-15 m).
The main structural elements of a waste disposal site are the containment liner, the protective lining layer, the leachate drainage layer and the top cover. To ensure tightness, mineral (clay) coatings, polymer film materials (for example, high-density polyethylene), asphalt concrete coatings, and soil reinforcement with bentonite are used.
The disposal site must be equipped with a reliable system for collecting and removing leachate. To ensure good drainage, a highly porous layer of some material, such as crushed stone, is laid over the entire base of the storage facility on top of the sealing coating.
To ensure reliable control, regulation and limitation of leachate release from the storage facility, the top coating, which is also made from mineral raw materials (clay) or from a polymer film, is important. Drainage pipes are placed at a distance of no more than 20 m from each other.
Before establishing a landfill, the composition of the waste should be determined, as it affects the scope of engineering activities that must be performed to create an orderly disposal site that meets environmental requirements.
There are two main types of burial: above ground and underground.
Underground burials- mines, voids, wells, old oil fields and other workings - are used mainly for the disposal of hazardous and radioactive waste.
Above ground burials various types(Fig. 8.1) are used to dispose of household and construction waste, as well as industrial waste with an accurately measured small content of toxic components.
Dump type burials have the following advantages:
* the base of the burial is located on the earth's surface;
* there is a good ability to control the compaction of the placed material;
* water drainage occurs without the use of pumps;
* the ability to monitor the condition of drainage systems.
Disadvantages of dump type burials:
* difficulty assessing the stability of slopes, especially at high burial heights;
* high shear stresses at the base of the slopes;
* the need to use special building structures to increase the stability of burial;
A- dump type of burial; b- burial on the slopes; in ■ Burial in pits; G - burial in an underground bunker; 1 ■ moves; 2 - waterproofing; 3 - concrete
Burials on the slopes Unlike the dump-type burials considered above, they require additional protection of the burial body from sliding and from being washed away by water flowing down the slope. Protection is carried out using building structures.
Burial in pits has less impact on the landscape and does not pose sustainability hazards. However, it requires drainage of water using pumps, since the base is located below the surface of the earth. Such burial creates additional difficulties for waterproofing the side slopes and the base of the waste disposal, and also requires constant monitoring of drainage systems.
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Burials in underground bunkers in all respects they are more convenient and environmentally friendly, however, due to the large capital costs of their construction, they can only be used to remove small amounts of waste. Underground burial is widely used for isolating radioactive waste, as it allows, under certain conditions, to ensure radioecological safety for the entire required period and is the most economical effective way handling them. Without going into details of the organization of underground storage facilities for radioactive waste, it should be noted that the most difficult problem is choosing a disposal site with optimal geological conditions.
Waste placement at the landfill should be carried out in layers no more than 2 m thick with mandatory compaction, ensuring the greatest compactness and absence of voids, which is especially important when burying large-sized waste.
Compaction of waste during disposal is necessary not only to maximize the use of free space, but also to reduce subsequent subsidence of the burial body. In addition, a loose burial body, having a density below 0.6 t/m, complicates the control of filtrate, since many channels inevitably appear in the body, making its collection and removal difficult.
The degree of waste compaction depends on the equipment used, the nature of the waste and the method of its disposal. For waste compaction, conventional road machines are used, such as crawler bulldozers with power from 50 to 120 kW, KM-305 rollers, as well as special heavy compactors with steel gears. The use of compactors allows the burial body to be compacted to 0.7 - 0.8 t/m.
Layer-by-layer covering of the entire base with small layers of waste of uniform thickness is more appropriate than laying waste over the entire height of the burial, but in separate areas.
However, sometimes, primarily for economic reasons, the storage facility is filled section by section. The main reasons for sectional filling are the need to separate different types of waste within one landfill, as well as the desire to reduce the areas where leachate is formed.
When assessing the stability of a burial body, one should distinguish between external and internal stability. Internal stability is understood as the state of the burial body itself (stability of the sides, resistance to swelling); External stability refers to the stability of the burial ground (subsidence, crushing). Insufficient stability can damage the drainage system and waterproofing. Subsidence is possible due to the following reasons:
Displaces water from wet waste;
An increase in the volume of voids due to the outflow of biogases formed as a result of microbiological processes;
Crushing waste due to mechanical loads.
Some experts believe that the laid layer of waste after compaction should be sprinkled with soil daily, which reduces the risk of transmission of infections by rodents and birds, as well as eliminates contamination of the area in windy weather. With large landfill areas this is not always possible due to technical and economic difficulties. It is more advantageous to use polymer films, synthetic degradable foams and other materials for temporary covering of the burial body.
After the burial is completed, it must be waterproofed from above and the land must be reclaimed. Such burials must be protected from further penetration of sediments and seepage water. This is not done immediately after the burial is completed, but after the end of biological processes in his body and the complete cessation of gas emission. Otherwise, a closed burial may turn into a time bomb.
Since modern requirements for waterproofing are not met when burying waste in unorganized landfills, these landfills are a source of groundwater and soil pollution. To waterproof existing landfills, technology has been developed to create lateral and horizontal barriers around the old landfill. Lateral isolation is created by drilling vertical wells into which special materials are injected that block the lateral migration of harmful substances from the body of the waste storage facility.
If contaminated waters are connected to deep-lying aquifers, then additional isolation of the landfill base is required using horizontal wells, which is carried out by drilling from the open side (if any) of the pit or by drilling inclined wells. Ozokerite (a product of brown coal extraction) or liquid glass and other silicate materials are used as waterproofing materials.
An important element of landfill management is environmental monitoring, the purpose of which is to identify any undesirable impacts on it in order to take the necessary corrective actions. The objects of monitoring are air and biogas, groundwater and leachate, soil and burial body. The scope of monitoring depends on the type of waste and the design of the landfill.
Due to the catastrophic shortage in our country of industrial waste landfills equipped in accordance with the rules, the practice of burying industrial waste together with municipal solid waste is practiced. The maximum amount of industrial waste allowed for storage at household waste landfills is standardized by a document approved by the Chief Sanitary Doctor.
In the Moscow region, industrial waste is accepted for disposal together with municipal solid waste at such large landfills as "Timokhovo" with an area of 64 hectares, "Salaryevo" (50 hectares), "Shcherbinka" (50 hectares), "Iksha" (40 hectares), " Khmetyevo" (25 hectares).
The main condition for accepting industrial waste to these landfills is compliance with sanitary and hygienic requirements for the protection of atmospheric air, soil, ground and surface water.
The main criterion for the acceptance of industrial waste is the composition of the filtrate at a pH of 5 - 10 and a temperature of 10 - 40 ° C, the inability of the waste to explode, spontaneous combustion, release of toxic gases, or generate intense dust. Their humidity should be no more than 85%. The maximum quantities of industrial waste that can be stored in solid waste landfills depend on their hazard class. Thus, waste belonging to hazard class IV is accepted without restrictions and can be used as insulating materials. The list of such waste is given in table. 8.1.
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Table 8.1
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The aqueous extract of toxic substances from these wastes corresponds to the solid waste filtrate, and the biochemical and chemical oxygen demand does not exceed 300 mg/l.
Industrial waste of hazard classes III and IV, the water extract of which also corresponds to solid waste in terms of the content of toxic substances, but has a biochemical and chemical oxygen demand of 3400 - 5000 mg/l, is accepted for disposal together with solid waste with restrictions. Their weight should not exceed 30% of the mass of solid waste. The list of such waste and the maximum volumes of their disposal per 1000 m of solid waste are given in table. 8.2.
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Table 8.2 Maximum norms for joint disposal at solid waste landfills of industrial waste of hazard classes IV and III, accepted with restrictions (per 1000 m3 of solid waste)
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Some types of industrial waste belonging to hazard classes III - IV, which are also limitedly accepted for disposal at solid waste landfills, require special conditions burial or preliminary preparation at the place of formation (Table 8.3)
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Table 8.3 Limit norms for the disposal of industrial waste of IV and III hazard classes (per 1000 m of solid waste), requiring compliance with special conditions
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At the same time, the total amount of all industrial waste of hazard classes IV and III accepted for disposal at a solid waste landfill should not exceed 100 tons per 1000 m of solid waste. Industrial waste that is capable of spontaneous combustion due to chemical reactions in the bulk of the stored mass or that emit vapors and gases that form explosive or toxic mixtures with the air or gases of the landfill are not allowed to be buried in household waste landfills.
Until recently, one of the most modern in our country was the Krasny Bor landfill for disposal and processing of industrial waste near St. Petersburg. The landfill is surrounded by a ring canal that drains groundwater and surface water from the surrounding area into the Bolshaya Izhora River. The landfill accepts sludge from sewage treatment plants and all industrial waste, with the exception of radioactive waste and those subject to regeneration.
All waste accepted for disposal at the landfill must have a passport with technical characteristics waste, a brief description of measures for its safe handling during incineration and disposal.
Combustible waste is burned at the landfill in special furnaces at a temperature of about 1000 °C. The layout of the polygon is shown in Fig. 8.2.
I- area for neutralization of inorganic waste; II - non-combustible organic waste disposal site; III- burial site for particularly hazardous waste; IV- thermal waste treatment area; V- administrative area; VI- garage; 1 - gearbox and weight; 2 - chemical laboratory; 3 - administrative building; 4 - boiler room
The landfill with an area of 58 hectares was created in 1969 and was designed for operation for 10 - 15 years, but is still in operation. Currently, 1.5 million tons of toxic waste have already been buried at the Krasny Bor landfill, which has led to its overflow and a difficult environmental situation around it.
More advanced landfills for the treatment and disposal of industrial waste were planned to be built in all major industrial regions of the country in the early 90s.
Waste disposal in Moscow is associated with very large disadvantages and difficulties. The main ones are: the lack of free land plots near the city, the constant increase in the distance of waste removal, the lack of transport, equipment and fuel for the removal and processing of waste, as well as for the preparation of the landfill and its control. Average range waste removal from Moscow to burial sites is 80 km, and from the cities of the Moscow region 40 km.
Such remoteness of waste disposal sites from the sources of their formation leads to numerous unorganized dumps of garbage and industrial waste, which do not have any preparation and subsequent control. In 1997 alone, 140.5 thousand tons of toxic waste were buried in unauthorized landfills in the country, and of the registered waste disposal sites with a total area of 14 thousand hectares, 15% did not meet the current requirements for landfills.
1. Landfill composition
A solid waste disposal site is a complex of environmental structures designed for storing, isolating and neutralizing solid household waste, providing protection from pollution of the atmosphere, soil, surface and groundwater, and preventing the spread of rodents, insects and pathogens.
Landfill for solid waste in general case consists of the following parts:
Access road along which solid waste is transported and empty garbage trucks return;
Economic zone intended for organizing the operation of the landfill;
Solid waste storage area where waste is placed and buried; the storage area is connected to the economic zone by a temporary on-site road;
Power supply line from external electrical networks.
The waste mass of the landfill is limited by the systems of engineering structures: the upper final coating and the anti-filtration screen to control the landfill's emissions - reducing the adverse impact on the environment.
2. Requirements for the location of the landfill
The selection of a site for a solid waste landfill is carried out on the basis of the functional zoning of the territory and urban planning decisions; the latter are carried out in accordance with SNiP. Landfills are located outside the residential area and in separate territories, ensuring the size of the sanitary protection zone.
Placement of polygons is not allowed:
On the territory of the I, II and III zones of sanitary protection zones of water sources and mineral springs;
In all zones of sanitary protection zones of resorts;
In areas of mass suburban recreation of the population and on the territory of medical and health institutions;
In recreational areas;
In places where aquifers are pinched out;
Within the boundaries of established water protection zones of open water bodies.
Placement of landfills in swampy and flooded areas is not allowed. Promising areas for locating landfills are areas where clays or heavy loams are found at the base, and groundwater lies at a depth of at least 2 m. In this case, the foundation soils should have a filtration coefficient of no more than 10 cm/s (0.0086 m/day). .
The selected site for the construction of a landfill must have a sanitary and epidemiological certificate confirming its compliance with sanitary rules.
3. Protection of the base of the solid waste storage area
For foundation soils with a filtration coefficient of more than 10 cm/s, it is necessary to provide the following anti-filtration screens:
1) single-layer clay screen with a thickness of at least 0.5 m. The original clay of an undisturbed structure must have a filtration coefficient of no higher than 0.001 m/day. A protective layer of local soil with a thickness of 0.2... 0.3 m is laid on top of the screen;
2) soil-bitumen screen treated with organic binders or waste from the oil refining industry with a thickness of 0.2 to 0.4 m on one side or double impregnation with bitumen emulsion, depending on the composition of the waste and climatic conditions;
3) double-layer latex screen. The screen consists of a 0.3 m thick grading sublayer, a latex layer, an intermediate layer of sandy soil 0.4 m high, a second latex layer and a protective layer of fine-grained soil 0.5 m thick;
4) a two-layer screen made of polyethylene film stabilized with carbon black. A two-layer screen consists of an underlying layer - clay soil with a thickness of at least 0.2 m, two layers of polyethylene film stabilized with soot, 0.2 mm thick. A drainage layer of coarse sand 0.4 m thick is placed between the layers of film. A protective layer (0.5 m thick) of sandy soil with particles of maximum particle size up to 5 mm is laid on the top layer of the film. It is allowed to use single-layer artificial screens without leachate drainage under favorable hydrogeological conditions of the storage area: the groundwater level is at least 6 m from the base surface of the working maps; the presence of loams at the base of the maps with a filtration coefficient of no more than 10 cm/s and a thickness of at least 6 m.
A drainage layer is provided for emergency situations and control of filtrate output.
5) screen from bentomat brand SS100. The soil on which the material is laid must be compacted with a compaction coefficient of at least 0.9. The base should not contain plant roots, stones or other objects that could mechanically damage the material. All irregularities in the base larger than 12 mm must be leveled. The amount of material laid on site daily must be such that it can be covered on the day of laying with a protective layer of soil. As an exception, it is allowed for a wheeled vehicle to move on laid mats, avoiding mechanical impacts on the material during sudden stops. The bentomat is protected by a layer of fine-grained soil with a layer thickness of 300 mm. Bentomat panels 5 m wide and 40 m long are overlapped by at least 150 mm. To ensure additional reliability, bentonite granules are poured between the overlapping edges in an amount of 0.4 kg/linear meter.
4. Drainage system
The drainage system is designed to collect and drain filtrate. One of the drainage system designs is as follows. A material with a small lime content with a particle size of 16...32 mm and a filtration coefficient of more than 10 m/s is applied to a layer of non-woven textile above the polymer fabric, acting as a return filter. The layer thickness is at least 50 cm.
In the area where the filtrate removal pipes are located, the layer thickness increases to 105 cm (three diameters of the filtrate removal pipe). This ensures sufficient protection of the pipe.
The return filter is poured at the beginning and, using lightweight equipment, is distributed over the protective fabric. Pipes are laid straight with a thrust angle of 120°.
To ensure removal of filtrate from the entire area, the return filter has a slope of more than 3% in the direction of the pipes for collecting filtrate. Maximum length the drainage of filtrate from the surface filter is 15 m. It follows that the maximum distance between filtrate collectors is 30 m.
Leachate collection occurs at the lowest point of the landfill using PEHD pipes (according to Russian classification- from polyethylene pipes PE 80 SDR technical according to GOST 18599-2001).
Drainage pipes are made with perforations (slots) across the pipe axis for 2/3 of the pipe perimeter. The area of the slots must be at least 5% of the outer surface of the drainage pipes. The slot width is 12 mm, the slot length is 60 mm, which protects them from clogging when using a return filter with a particle size of 16... 32 mm. The ends of the pipes are not perforated when passing through the enclosing embankment.
In the direction of leachate flow, drainage pipes pass through the landfill embankment and the protective layer on the slope and enter sewer wells located outside the landfill field.
On the opposite slope, drainage pipes are led upward along the polymer layer from the storage area for inspection and washing. At the edge of the slope the drainage pipes end. They are closed with an airtight cap, which is dismantled for technical inspection. With this design, it is possible to access the filtrate collectors from two sides, and there is also the possibility of washing and using a mobile camera.
In the area where drainage pipes are laid through the embankment, controlled pipes (pipe-in-pipe system) must be used. The support of the pipe at the point where it passes through the embankment must be made in such a way that water does not leak in this place.
After drainage pipes are removed from the storage area in sewer wells, they are combined into a common (sewer) pipe with discharge into a filtrate collection tank.
If necessary (according to the altitude conditions of the area), a pumping station can be installed to collect the filtrate. From the pumping station, the filtrate is pumped into the collection tank.
The filtrate collected by the sewer system can be removed using a pumping station to district wastewater treatment plants. Part of the filtrate can be supplied to the storage area using a pumping station to moisten solid waste during a fire hazard period.
5. Economic zone
5.1. Composition of structures
On the territory of the hozzone there are:
Administrative and amenity building (ABK);
Checkpoint (checkpoint) together with a stationary radiometric control point;
Weight;
Garage and areas with sheds and workshops for parking and repairing machines and mechanisms;
Warehouse of fuels and lubricants;
Warehouses for storing energy resources, building materials, workwear, household equipment, etc.;
Electrical supply facilities;
Garbage truck washing;
Fireproof containers;
Disinfectant baths;
Treatment facilities for washing garbage trucks;
Sewage pumping station.
The administrative building contains social premises for workers (locker rooms, toilets, showers), a rest room, a canteen, and a security room.
The territory of the economic zone must have a hard surface, lighting and entry from the landfill.
At large landfills receiving over 360 thousand cubic meters. m/year of solid waste and designed for a service life of more than 15 years, technical water supply is provided from artesian wells located on the territory of the economic zone. Drinking water must be imported.
At smaller landfills designed for a service life of less than 15 years, in agreement with Rospotrebnadzor authorities and local municipal authorities, technical water supply is provided with imported water.
Removal of wastewater is carried out using:
City sewerage system (if there is a sewer collector at an economically feasible distance);
Control and regulation pond;
Evaporation pond.
The area of the evaporation pond is determined from the estimated storm water runoff from the landfill area.
Near the economic zone, a parking area for passenger cars of landfill workers is being constructed.
The number of parking spaces per 100 workers in 2 adjacent shifts is 7... 10. This number should be adjusted in accordance with the level of motorization.
The territory of the economic zone is supplied with storm sewerage with discharge of wastewater into the general sewer network.
The administrative sewage system is designed to collect wastewater in septic tanks, from which transportation to city (district) treatment plants is organized.
5.2. Basic parameters of structures.
At the exit from the landfill there should be a control and disinfection zone with a reinforced concrete bath 8 m long, 0.3 m deep and 3 m wide for disinfecting the wheels of garbage trucks. The bathtub is filled with a three percent Lysol solution and sawdust.
Water consumption for external fire extinguishing is 10 l/s. A prefabricated reinforced concrete tank or pond for fire extinguishing is designed with a capacity of at least 50 cubic meters. m and is determined by local conditions.
A fence is being designed along the perimeter of the entire territory of the solid waste landfill. The fence can be replaced by: a drainage trench more than 2 m deep, a shaft more than 3 m high. A gate or barrier is designed in the fence of the landfill near the administrative building.
Drainage (upland) ditches are designed to drain runoff from areas located above the landfill.
External lighting according to a permanent scheme is provided only for the economic zone; daily maps are illuminated according to a temporary scheme.
The minimum illumination of working (daily) cards is 5 lux.
6. Operation of the landfill
6.1. Basic technological operations.
The following main types of work are performed at the landfill: reception, storage and isolation of solid waste.
Accounting for accepted solid waste is carried out by volume in an uncompacted state. A note on the accepted amount of solid waste is made in the solid waste registration log.
It is strictly prohibited to transport waste suitable for use to landfills. national economy as secondary resources, as well as toxic, radioactive and biologically hazardous waste.
The organization of work at the landfill is determined by the technological scheme for operating the landfill, developed as part of the project. The main work planning document is the operation schedule drawn up for the year. It is planned monthly: the number of solid waste received, indicating N cards on which waste is stored, development of soil for isolating solid waste.
The organization of work at the site must ensure environmental protection, maximum productivity of mechanization equipment and safety precautions.
6.2. Control of delivered solid waste.
The operation of the landfill, waste disposal, and refusal to accept waste must be regulated by regulations on the acceptance of permitted types of waste. In order to ensure that only permitted waste is stored, control measures are required on the part of landfill personnel.
Control of delivered waste includes the following:
Checking the carrier's accompanying documents;
Determination of volume and weight of waste;
Conducting visual inspection;
Performing radiometric monitoring.
Checking of accompanying documents and measuring weight are carried out upon entry. Visual control, in which the delivered waste is monitored by appearance, consistency, color and smell, is carried out during weighing and when unloading machines. If in doubt, sampling of the imported material is necessary. Waste brought to the landfill that is not permitted for storage will not be accepted.
6.3. Unloading transport.
Uninterrupted unloading of garbage trucks is organized at the landfill. Garbage trucks arriving at the landfill are unloaded at the working map.
The area for unloading garbage trucks in front of the working map is divided into two sections: garbage trucks are unloading in one section, bulldozers or compactors are working in the other.
The placement of garbage trucks at the unloading site should ensure the unimpeded exit of each unloaded vehicle.
The duration of reception of garbage trucks for unloading in one section of the site is assumed to be 1...2 hours. The minimum area in front of the working map, taking into account its division into two parts, must simultaneously ensure at least 12% of the unloading of garbage trucks arriving during the working day.
The path from the scales to the unloading point is equipped with signs. All vehicles follow the signs and take the shortest route from the scales to the storage area. Drivers are shown the unloading location. Machines must maintain a safe distance to the unprotected edge of the slope - at least 10 m. After unloading and re-inspecting the batch, the machine immediately leaves the unloading site.
6.4. Waste disposal.
Solid waste unloaded from vehicles is stored on a working map.
Indiscriminate storage of solid waste throughout the entire area of the landfill, outside the area allocated for a given day (work maps), is not allowed. The following dimensions of the working map are established: width 5 m, length 30 - 150 m.
Bulldozers move solid waste onto the working map, creating layers up to 0.5 m high. Due to 5... 10 compacted layers, a shaft is created with a gentle slope 2 m high above the level of the garbage truck unloading area. The shaft of the next working card is “pushed” towards the previous one (by storing using the “pushing” method). With this method, waste is placed from bottom to top.
A compacted layer of solid waste 2 m high is isolated with a layer of soil 0.25 m (if compaction is ensured by 3.5 times or more, an insulating layer 0.15 m thick is allowed). Unloading of garbage trucks in front of the working map should be carried out on a layer of solid waste, more than 3 months have passed since the time of laying and insulating it. (as the maps are filled out, the work front moves away from the solid waste placed in the previous day).
Storage of solid waste using the “pushing” method is carried out from top to bottom. The height of the slope should be no more than 2.5 m. With the “push” method, in contrast to the “pushing” method, the garbage truck is unloaded on the upper isolated surface of the working map formed the previous day. As the maps are filled, the work front moves forward along the solid waste laid in the previous day.
The movement of solid waste unloaded by garbage trucks onto the working map is carried out by bulldozers of all types. To increase the productivity of bulldozers (by 30 - 40%), it is necessary to use blades with greater width and height.
Compaction of solid waste laid on the working map in layers of 0.5 m is carried out by heavy bulldozers weighing 14 tons and based on tractors with a power of 75... 100 kW (100... 130 hp). Compaction in layers of more than 0.5 m is not allowed. Compaction is carried out by passing the bulldozer 2...4 times over one place. Bulldozers compacting solid waste must move along long side cards. With a 2-fold pass of the bulldozer, the solid waste compaction is 570... 670 kg/cubic. m, with a 4-fold pass - 670... 800 kg/cubic. m.
To ensure uniform subsidence of the landfill body, it is necessary (twice a year) to make a control determination of the degree of compaction of solid waste.
Humidification of solid waste in summer must be carried out during fire hazardous periods. Water consumption for irrigation is assumed to be 10 liters per 1 cubic meter. m solid waste.
Intermediate and final insulation of the compacted layer of solid waste is carried out with soil. When storing solid waste in open, non-buried storage areas, intermediate insulation is carried out daily in the warm season, and at intervals of no more than three days in the cold season. The layer of intermediate insulation is 0.25 m, when compacting solid waste with KM-305 rollers - 0.75 m.
The development of soil and its delivery to the working map is carried out by scrapers.
IN winter period It is allowed to use construction waste and industrial waste (waste lime, chalk, soda, gypsum, graphite, etc.) as an insulating material. As an exception, in winter it is allowed to use snow supplied by bulldozers from nearby areas for insulation. In the spring, when the temperature rises above 5 °C, the areas where snow insulation was applied are covered with a layer of soil. Laying the next tier of solid waste on an insulating layer of snow is unacceptable.
6.5. Sanitary protection zone.
The sanitary protection zone (SPZ) separates the territory of the landfill site from residential buildings, landscape and recreational zones, recreation areas, and resorts with mandatory marking of boundaries with special information signs.
A sanitary protection zone is a mandatory element of a solid waste landfill. The use of sanitary protection zone areas is carried out taking into account the restrictions established by current legislation, norms and rules. The sanitary protection zone is approved in the prescribed manner in accordance with the legislation of the Russian Federation in the presence of a sanitary and epidemiological conclusion on compliance with sanitary norms and rules.
The width of the sanitary protection zone is established in accordance with SanPiN 2.2.1/2.1.1.1200-03. The width of the CVD of the solid waste landfill is taken as equal to 500 m for a 2nd class enterprise.
The territory of the sanitary protection zone is intended for:
Ensuring that the level of exposure is reduced to the required hygienic standards for all factors of influence beyond its boundaries;
Creation of a sanitary protective barrier between the landfill territory and the residential area;
Organization of additional green areas that provide screening, assimilation and filtration of atmospheric air pollutants and increase the comfort of the microclimate.
The sanitary protection zone must have a consistent study of its territorial organization, landscaping and landscaping at all stages of the development of construction projects, reconstruction and operation of the landfill.
For an existing landfill, the project for organizing a sanitary protection zone must be a mandatory document.
As part of the project for the organization, landscaping and improvement of sanitary protection zones, documentation is provided in the amount that allows an assessment of design decisions regarding their compliance with sanitary standards and rules.
In pre-design, project documentation for the construction of new, reconstruction or technical re-equipment of existing landfills, measures and funds must be provided for the organization and improvement of sanitary protection zones, including the relocation of residents if necessary. The project for organization, improvement and landscaping is presented simultaneously with the project for construction (reconstruction, technical re-equipment).
6.6. Monitoring system.
The monitoring system must contain:
Organizational structure;
General model of the system;
Complex of technical means;
Models of the situation;
Methods of observations, data processing, situation analysis and forecasting;
Information system.
A special monitoring project is being developed for the solid waste landfill, which includes sections: monitoring the condition of underground and surface water bodies, atmospheric air, soils and plants, noise pollution in the area of possible adverse influence of the landfill; a system for controlling technological processes at a landfill, ensuring the prevention of pollution of underground and surface water bodies, atmospheric air, soils and plants, and noise pollution above permissible limits in cases where the polluting influence of landfills is detected.
The solid waste landfill monitoring project is being developed according to technical specifications owner of the landfill and is coordinated with the authorized bodies.
The monitoring system must include devices and structures to monitor the condition of ground and surface water, atmospheric air, soil and plants, as well as noise pollution in the area of possible influence of the landfill.
In agreement with the hydrogeological service, local authorities of Rospotrebnadzor and environmental protection, control pits, wells or boreholes are designed in the green zone of the landfill to monitor the state of groundwater, depending on their depth.
One control structure is installed upstream of the landfill in order to sample water that is not affected by leachate from the landfill. Water samples from control pits, wells and boreholes located upstream of the landfill along the groundwater flow characterize their initial state.
Below the landfill along the groundwater flow (at a distance of 50... 100 m, if there is no danger of groundwater contamination from other sources), 1 - 2 wells (pits, boreholes) are laid to take water samples in order to identify the influence of the landfill runoff on it.
Wells with a depth of 2... 6 m are made of reinforced concrete pipes with a diameter of 700... 900 mm to a mark of 0.2 m below the groundwater level (GWL). The filter bottom consists of a layer of crushed stone 200 mm thick. They go down into the well using a stationary ladder.
When groundwater occurs deeper, its control is carried out using wells. The design of structures must ensure protection of groundwater from accidental contamination, the possibility of drainage and pumping, as well as the convenience of taking water samples. The volume of indicators to be determined and the frequency of sampling are justified in the landfill monitoring project.
In the selected samples, the content of ammonia, nitrites, nitrates, bicarbonates, calcium, chlorides, iron, sulfates, lithium, COD, BOD, organic carbon, pH, magnesium, cadmium, chromium, cyanides, lead, mercury, arsenic, copper, barium is usually determined , dry residue, etc.
If in samples taken downstream a significant increase in the concentrations of the determined substances is established compared to the control, it is necessary, in agreement with the regulatory authorities, to expand the scope of the determined indicators, and in cases where the content of the determined substances exceeds the MPC, it is necessary to take measures to limit the entry of pollutants into groundwater up to the MPC level.
Above the landfill on surface water sources and below the landfill on drainage ditches, surface water sampling sites are also designed. Selected samples are examined for helminthological, bacteriological and sanitary-chemical indicators.
If in water samples taken downstream of surface water a significant increase in the concentrations of the determined indicators is established compared to the control, it is necessary, in agreement with the regulatory authorities, to expand the scope of the determined indicators, and in cases where the content of the determined substances exceeds the maximum permissible concentration, it is necessary to take measures to prevent entry of pollutants into surface water bodies to the MPC level. Vehicle access to ground and surface water control facilities is designed and provision is made for drainage or pumping of water before sampling.
The estimate for the construction of the landfill includes the costs of installing samplers for taking water samples used in the water supply and sewerage system.
The monitoring system must include constant monitoring of the state of the air environment. For these purposes, it is necessary to conduct quarterly analyzes of atmospheric air samples over the waste sites of the landfill and at the border of the sanitary protection zone for the content of compounds that characterize the process of biochemical decomposition of solid waste and pose a great danger.
The volume of indicators to be determined and the frequency of sampling are justified in the landfill monitoring project and agreed upon with the authorized bodies. Typically, when analyzing atmospheric air samples, the content of methane, hydrogen sulfide, ammonia, carbon monoxide, benzene, trichloromethane, carbon tetrachloride, and chlorobenzene is determined.
If air pollution is established above the maximum permissible concentration on the border of the sanitary protection zone and above the maximum permissible concentration. At the landfill workplace, appropriate measures must be taken taking into account the nature and level of pollution.
The monitoring system should include constant monitoring of the condition of the soil in the area of possible influence of the landfill. For this purpose, the quality of soil and plants is monitored for the content of exogenous chemical substances (ECS), which should not exceed the maximum permissible concentration in the soil and, accordingly, the residual amounts of harmful ECS in the commercial plant mass should not exceed permissible limits. The volume of determined chemical substances and the frequency of monitoring are determined in the landfill monitoring project and are agreed upon with specially authorized environmental protection authorities.
7. Collection of landfill gas and its processing
7.1. General information on landfill gas, gas condensate, quantity and quality.
Landfill gas is formed due to the fermentation of organic components in waste in the body of the landfill during biochemical decomposition processes. In addition to gaseous decomposition products, gaseous components of sediments (eg greenhouse gases) and water vapor (in a saturated state) are also formed.
The resulting gases and vapors form a wet gas mixture variable composition. The main components of this mixture are methane CH, carbon dioxide CO.
Due to its main components, as well as the presence of other hazardous components, landfill gas emissions can have a harmful effect on the environment in the form of:
Hazards of explosion, burning, smoke;
Interference with landfill reclamation;
Distribution of the corresponding odor;
Release of toxic or hazardous components;
Harmful impact on the climate.
Based on this, gases must be collected and utilized (processed).
The emergence of landfill gas occurs in five phases, and the reduction in formation occurs in four (Table 1).
Table 1
Phases of landfill gas formation
| Phase | Name | Process |
| I | Oxidation (aerobic phase) |
Education landfill gas |
| II | Acid fermentation | |
| III | Unstable fermentation methane |
|
| IV | Stable methane phase |
|
| V | Methanogenic long-term phase |
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| VI | Arrival phase air |
Decrease education |
| VII | Oxidation phase methane |
|
| VIII | Carbon dioxide phase | |
| IX | Air phase |
Due to the duration of the waste disposal process, local overlap of various phases occurs. The presence and condition of the surface coating system also influences gas formation, since biochemical decomposition of organic substances and gas formation occurs with the consumption of water; The solid waste body dries out slowly with reduced water supply.
Before construction of a landfill gas collection and treatment system, careful and comprehensive studies must be conducted, including a complete analysis of the composition of the landfill gas.
7.2. Research to determine the composition of landfill gas.
To assess the probable environmental pollution and danger during the emission of landfill gas, as well as its possible energy potential, comprehensive gas engineering studies are usually carried out. The results obtained provide the basis for the development or selection of landfill gas collection and treatment systems.
Gas measurements consisting of FID (flame ionization) and measurements at the soil surface can be used as primary studies. Taking into account the indicators obtained from the measurements, a multi-month gas extraction experiment is planned, during which gas is actively pumped out in the demonstration section of the landfill.
Since gas engineering studies show the instantaneous state of gas origin, they are complemented by a developed quantitative forecast of gas production (to determine the time dependence of the gas formation schedule). If the gas pumping tests carried out suggest the origin of the gas in the landfill pile and significant emission potential, planning and construction is necessary active system collection of landfill gas and its processing.
7.3. Expected gas output.
Given a sufficient number (i.e., over the entire surface) of gas wells, the actual volumes of gas pumped out per unit time depend in large part on the structure and degree of coverage of the landfill, associated with these moisture conditions in the body, and on the well system used.
7.4. Component composition of landfill gas.
The composition of the gas is determined based on the results of testing samples (extracts) of landfill gas. The number of main components for landfills with typical landfill gas formation is within the following limits (Table 2).
table 2
Components of landfill gas
Landfill gas may contain other components.
7.5. The amount of water condensate and its composition.
The resulting landfill gas enters the system in a state saturated with water vapor, and with a heavy load of pumping gas from a well (well), it may contain drops of water (aerosol). Due to the cooling of the gas in the pipeline system, water condensate is released from it.
The released condensate flows freely along the foot of the gas pipe to the next low point, where the condensate is removed from the gas system.
Since the pumping side of the gas system is always under vacuum, the separator must be sealed (vacuum-tight).
On the pressure side of the gas system, where the pressure is higher than atmospheric pressure, condensation is unlikely to occur. A small amount of water condensate may form when the pipeline cools down during shutdowns. Maintenance connected gas consumers (high temperature flare).
Water condensate released from landfill gas consists (according to the formation mechanisms) of water (the main component), steam-distilled components (ammonium), condensed other substances and leachate from the landfill (if ruptures occur during pumping). The expected amount of condensate is calculated based on the results of experimental sampling of landfill gas from boreholes.
7.6. Technological scheme for collection and utilization of landfill gas.
An active landfill gas removal facility primarily aims to reduce emissions and, after construction, to protect the top cover of the solid waste pile against damage from rising landfill gas. The installation consists of the specified side collectors (drill wells, gas wells, gas pipelines, control system), as well as a flare block and a condensate pipeline system. If the quantity and quality of landfill gas allows its economical use for electricity production, it is necessary to build a block thermal power plant with the possible use of thermal renewable energy sources. Landfill gas collection points in connection with the ongoing waste disposal process must be designed in such a way that the process can continue further, and the surface of the waste disposal only subsequently undergoes final sealing in parts. This means that the construction of devices for collecting landfill gas should be carried out in stages, corresponding to waste disposal and partial sealing of the solid waste pile. It is possible to select a device for collecting landfill gas at low or high points, as well as in a mixed manner. The advantage of collection at low points is the return flow of condensate into the gas well. This creates a barrier to ongoing drying and thereby influences the formation of landfill gas.
Gas removal from the landfill should primarily be carried out by pumping from vertical wells (wells), which makes it possible to remove gas from large areas of various sections of the landfill. Due to the subsidence and settlement of the landfill body due to compaction and massive volume reduction during biological decomposition processes, the functional performance of horizontal drainage is at great risk, and such drainage should be used in exceptional cases. Each vertical well is regulated separately using a valve and is connected by a pumping pipe to the collecting traverse of the regulating gas station. Gas from the wells enters the collecting gas pipeline, and from it in the form of mixed gas is supplied to the flare unit or to the block thermal power plant.
Prefabricated manifolds are located in accordance with industrial safety requirements in closed gas control stations (primarily protection from frost in winter). The pumping and utilization of landfill gas occurs through a pumping station using an integrated high-temperature flare.
Access to the landfill gas collection facility must be provided through the main entrance to the landfill or through internal production routes. The control station, gas pumping unit and flare unit must be located in a non-settlement area to ensure reliable operation. They are entered through a locked door. The pumping station consists of machine and switching rooms. It is preferable to provide access to the switching room through a single-leaf door, and to the machine room through a double-leaf door. The flare can be integrated into the pumping building or installed freely. The arrangement of individual parts of the installation must take into account the necessary fire safety rules and distances.
7.7. General safety provisions in the landfill gas collection and utilization system.
In a simplified form, landfill gas (biogas) can be considered as a binary gas mixture with the components methane and carbon dioxide. At a certain concentration of a mixture of methane and oxygen, an explosive mixture occurs. The explosive range of a gas-air mixture of pure methane with atmospheric air is in the range from 5 to 15% by volume.
Due to inert gases such as carbon dioxide and nitrogen, this range is significantly limited. With an increase in the amount of CO2 or N 2, the explosive range narrows from the lower limit until the moment when the amount of air reaches 58% and the upper and lower explosive limits coincide.
During gas pumping activities in gas pipelines, there is a danger of atmospheric air being drawn in from the pumping side. Drawing air into areas low pressure may occur during, for example, depressurization of a gas pipeline (leakage in the gas pipeline).
On the pressure side of the fan, landfill gas may leak into the atmosphere due to depressurization of pipelines. In the event of ignition of an explosive mixture of methane and air in a closed system, depending on the composition of the mixture, significant explosive pressure may arise, therefore technical systems for measuring, draining and harmless disposal of landfill gas must be equipped, operated and supervised to comply with technical conditions security. In addition to the emergency shutdown function, activated by the established critical indicators of the amount of CO2 and CH4, as well as the excess temperature in the flame damper in front of the unit, not only an emergency shutdown of parts of the system is performed, but also a corresponding notification. This function is also activated when the gas concentration in the room increases.
8 . Landfill closure
The closure of the landfill for receiving solid waste is carried out after dumping it at the design level. The last layer of waste before closing the landfill is covered with a layer of soil, taking into account further reclamation. When planning the insulating layer, it is necessary to ensure a slope towards the edges of the landfill.
The design of the landfill's insulating layer is determined by the task for its reclamation. Strengthening the external slopes of the landfill should be carried out from the beginning of the operation of the landfill as the storage height increases. The material for covering the outer slopes of the landfill is the vegetable soil previously removed during its construction.
To protect against weathering or washout of soil from the slopes of the landfill, it is necessary to plant them immediately after laying the insulating layer. Protective plantings are planted along the slopes and terraces are built. The choice of tree and shrub species is determined by local conditions.
In areas subsequently used for open warehouses of non-food containers, the thickness of the top insulating layer must be at least 1.5 m. When using the reclaimed territory of the landfill for growing agricultural products, gardening and berry plants and forest plantings, the thickness of the top insulating layer can be changed to depending on the type of plant crops grown. Upper layer Before covering it with insulation, waste must be carefully compacted to a density of at least 750 kg/m3. m.
According to EU rules, after filling individual areas or the entire landfill and stabilizing the solid waste sludge, it is necessary to apply a surface sealing system.
According to current EU regulations, the surface sealing system must contain the following components (from top to bottom):
Artificial impermeable layer (polymer fabric);
Impermeable mineral layer;
Drainage layer more than 0.5 m thick;
Top surface covering more than 1 m thick.
To avoid loss of functions of the drainage layer, it is necessary to lay inert material (sand) or filter-stable geotextile between the drainage layer and the top surface covering.
