The compilation team of Technical Specification for Environmental Protection Acceptance of Construction Projects: Domestic Waste Landfill Project of the Ministry of Environmental Protection recently confirmed that at present, about two-thirds of large and medium-sized cities in China are surrounded by garbage, and about 1.4 cities have no suitable places to dump garbage. Statistics show that in recent years, with the acceleration of urbanization and the improvement of people's living standards, the average annual growth rate of urban domestic waste in China is nearly 9%, and the per capita annual output reaches 440kg. The growth rate of Beijing and other cities is as high as 15%-20%. At present, the output of urban domestic waste in China is about 65.438+0.46 billion tons, and the cumulative amount of urban domestic waste is more than 7 billion tons, covering an area of more than 500 million square meters.
20 13 China statistical yearbook data: by the end of 20 12, there were 540 landfill sites in China, with a landfill capacity of 3 1. 1.025 million tons/day, and the total annual landfill amount was1.051. About 72.6% of municipal solid waste is treated by landfill.
The main environmental impacts of municipal solid waste landfill treatment include the pollution of peculiar malodorous gas emitted by garbage, landfill gas pollution caused by garbage degradation and fermentation during landfill, leachate pollution with high concentration of pollutants caused by physical, chemical and biological effects, leaching and washing of rainwater and soaking of groundwater during garbage stacking and landfill, and the concentration of flies and insects caused by landfill odor. As the traditional and final treatment method of domestic waste, landfill technology is still the main way to treat domestic waste in China and most countries in the world. The overall level of domestic waste landfill in China is still in the primary stage.
Second, the principle of comprehensive garbage management:
According to local conditions, scientific guidance. Considering the actual situation in different regions, we should strengthen classification guidance and adhere to the combination of centralized treatment and decentralized treatment. In accordance with the principle of "reduction, recycling and harmlessness", advanced and applicable technologies are selected according to local conditions, and resource treatment technologies such as incineration are given priority in areas where conditions permit.
Domestic waste in China can be generally divided into four categories: recyclable waste, kitchen waste, harmful waste and other wastes. At present, the commonly used garbage disposal methods mainly include comprehensive utilization, sanitary landfill, incineration and composting.
1. Recyclable garbage mainly includes five categories: waste paper, plastic, glass, metal and cloth.
1) Waste paper: it mainly includes newspapers, periodicals, books, all kinds of wrapping paper, office paper, advertising paper, cartons, etc. However, it should be noted that paper towels and toilet paper are too water soluble to be recycled.
2) Plastics: mainly including various plastic bags, plastic packaging, disposable plastic lunch boxes and tableware, toothbrushes, cups, mineral water bottles, toothpaste tubes, etc.
3) Glass: mainly includes various glass bottles, broken glass pieces, mirrors, light bulbs, thermos bottles, etc.
4) Metal objects: mainly include cans and cans.
5) Cloth: mainly includes discarded clothes, tablecloths, towels, schoolbags, shoes, etc.
Comprehensive treatment and recycling can reduce pollution and save resources. If every 1 ton of waste paper is recycled, 850 kilograms of paper can be made, 300 kilograms of wood can be saved, and pollution is reduced by 74% compared with the same output; Every 1 ton plastic beverage bottle can recover 0.7 tons of secondary raw materials; Every recovered 1 ton of scrap steel can produce 0.9 tons of steel, which saves 47% cost compared with ore smelting, reduces air pollution by 75%, and reduces water pollution and solid waste by 97%.
2. Kitchen waste includes food waste such as leftovers, bones, roots, leaves and peels. After biotechnology treatment, 0.3 tons of organic fertilizer can be produced per ton.
3. Hazardous wastes include: waste batteries, waste fluorescent tubes, waste water silver thermometers, expired drugs, etc. These wastes need special safety treatment.
4. Other wastes include bricks and tiles, muck, toilet waste paper, paper towels and other wastes that are difficult to recycle.
Three, the comprehensive treatment process of municipal solid waste:
1. Brief introduction of municipal solid waste resource treatment technology
According to the analysis of domestic waste treatment methods, the domestic waste treatment process in Zheng 'an County will adopt a "fast, harmless, all-resource, industrialized and intelligent" garbage treatment process. The advantages of this treatment process are as follows:
1) solves the problems of large area, short use time, long occupation time, groundwater pollution, soil pollution, air pollution and so on in the process of sanitary landfill of municipal solid waste;
2) The problems of high operating cost and difficult treatment of toxic gases generated by pure incineration and pure incineration power generation processes are solved;
3) It solves the problems of poor fertilizer quality, difficulty in recycling, mosquito and fly breeding in composting plant and harm to the health of surrounding people.
2. Process description of urban waste sorting workshop:
Municipal solid waste is transported to the garbage sorting workshop through garbage transfer stations and garbage trucks. After weighing, the garbage truck enters the closed garbage sorting workshop to unload the garbage into the garbage temporary pit with the volume of 1800m3, and the deodorant is sprayed when unloading. The garbage in the garbage temporary storage pit is sent to the plate feeder through the grab of the bridge double-beam crane, and conveyed to the 120mm crusher by the belt conveyor and the electromagnetic iron remover (recovering some metals). This machine can crush all large pieces of garbage and bagged garbage (particle size is greater than 400mm, crushing rate is 99%). After crushing, the garbage with the particle size of 0 ~ 0~ 120mm enters the roller garbage separator, and the kitchen organic garbage and part of sandy garbage (undersize) separated by the roller garbage separator directly enter the crusher for crushing (the crushing particle size is controlled below 30mm), and the broken kitchen organic garbage and part of sandy garbage enter the organic fertilizer workshop through the belt conveyor to produce organic fertilizer (the organic matter in the garbage can be separated by 75-90%). The light garbage (on the screen) sorted by the roller garbage sorter enters the positive pressure sorter for sorting. In the positive pressure sorter, the incoming garbage meets the flat airflow vertically, and is sorted according to different specific gravity and different landing points. Wood, rubber, textiles, etc. The heavy products separated by the positive pressure separator enter the electromagnetic iron remover for iron removal, and the heavy products after iron removal enter the gas-making workshop as combustible materials after being crushed by the crusher. The (light products) separated by positive pressure separator enter photoelectric separator for further separation, and impurities (leaves, paper, etc. ) mixed with heavy products and sent to the gasification workshop for gasification.
The waste plastics sorted by photoelectric sorter are sent to wood-plastic workshop by belt conveyor, cleaned, granulated and mixed with wood powder to make wood-plastic plates or wood-plastic profiles.
Part of the separated sand mixed with combustible substances enters the gas-making workshop to make gas. The cinder enters the building materials workshop to produce aerated concrete. ?
The broken kitchen organic waste and some sandy waste enter the organic fertilizer workshop through the belt conveyor to produce organic fertilizer. In the organic fertilizer workshop, the organic matter is completely matured in the process of thermal oxidation treatment of hydrolyzed water, and completely expanded into powder when sprayed, while inorganic sand and glass slag have the same volume. There is no change, so the sprayed materials are dried by the dryer and screened by the screening machine, and become organic fertilizer, that is, all organic wastes become undersized, all inorganic substances become undersized (sand, glass slag), and inorganic and mixed organic substances are separated by the screen. This technology is a complete separation technology of organic matter and inorganic matter in garbage separation technology at home and abroad, that is, "thermal separation" technology.
3. Treatment method:
1) biodegradable organic matter, sludge, leachate-organic fertilizer (organic fertilizer workshop).
2) Making sand and gravel aerated concrete (building materials workshop). ?
3) Plastics-cleaning, crushing and granulating straw sawdust to produce wood-plastic products (wood-plastic workshop).
4) Non-recyclable combustible substance-anaerobic combustible gas production (pyrolysis gas production workshop).
5) Waste batteries and metals-recycling.
4. The main characteristics of integrated management of domestic waste:
The modern production line is designed according to the garden-style factory planning, three-dimensional layout, centralized control, computer management and visual monitoring. The materials are transported in a closed way, the gas is completely purified and then discharged, and no waste water is discharged, thus realizing clean production. All indicators have reached the relevant national standards.
1) fast: the products will be delivered in four hours, and the garbage will be disposed of on the same day, so that Nissan will be able to clear the day.
2) Harmless: fully enclosed operation, so there will be no odor overflow; Plastic is not burned, so there is no harmful waste gas or less harmful waste gas; Organic matter is hydrolyzed and thermally oxidized by water at high temperature and high pressure, so it is completely sterilized; Quick treatment with little or no leachate.
3) No surplus: All garbage is recycled and thoroughly treated. ?
4) Strong adaptability? Urban and rural domestic waste, vegetable market waste, construction waste, medical waste, livestock manure, livestock carcasses, food industry waste, agricultural waste, traditional Chinese medicine industry waste, sewage treatment plant sludge, landfill leachate.
5) Small floor space: it is one quarter of that of composting method and one sixth of that of landfill method, and the land used can be used permanently.
6) High level of resource utilization and industrialization: due to thorough pre-sorting, all recyclable materials can be recycled, and at the same time, the amount of garbage incineration is reduced, and the amount of harmful gases is also reduced (especially, the amount of dioxin generated in the incinerator is reduced 100% compared with the pure incineration process).
7) Advanced equipment: the main equipment is mostly patented equipment developed through years of field experience, with low failure rate and good use effect, which is especially suitable for the treatment of municipal solid waste in China.
8) Energy is recycled, and garbage is treated by garbage, so the treatment cost is low. The economic benefit is good, and the output is far greater than the input. ?
Fourth, the effect:
Using comprehensive garbage treatment technology to build a garbage treatment plant has the advantages of mature technology, reliable technology, remarkable economic benefits, small project investment, short construction period and fast recovery time. The main equipment is mainly domestic patented equipment, which has reliable performance and is economical and applicable. No secondary pollution, high utilization of resources. Because of its price, quality and other factors, the products produced by its comprehensive treatment technology have broad market prospects, completely realizing that "mixing is garbage and separation is resources"; The concept of "coming in is garbage, going out is product" and resource recycling. It will certainly make due contributions to improving human living environment, building a new socialist countryside, building a resource-saving society and developing a circular economy.
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