What are the hazards of landfill?
What are the hazards of landfill?
Explosion accidents and fires. The gas released by landfill contains a lot of CH4 and CO2. When the concentration of CH4 in the air reaches 5%~ 15%, it is easy to cause explosion. The methane explosion at Yangfang Town Landfill in Changping County, Beijing is a typical example.
Groundwater pollution. Volatile organic compounds and CO2 in landfill gas will dissolve into groundwater, which will break the equilibrium pressure of CO2 in the original groundwater, promote the dissolution of CaCO3 and increase the hardness of groundwater. The escape of landfill gas from a fully enclosed landfill will cause liner leakage, aggravate the leaching of leachate and lead to groundwater pollution.
Aggravated global warming. CH4 and CO2 are the main greenhouse gases, which will produce greenhouse effect and make the global climate warm. CH4 destroys ozone 40 times as much as CO2, and the greenhouse effect is more than 20 times higher than CO2, while CH4 content in landfill gas is 40%~60%.
Causing plants to suffocate. Although CH4 has no direct physiological effect on vascular plants, it can reduce the oxygen level in the rhizosphere of plants through direct gas replacement or oxygen consumption by methanogens, so that the root zone of plants will die due to hypoxia. In addition, CH4 can promote the formation of C2H4 under anaerobic conditions.
Landfill gas contains carcinogenic and teratogenic volatile organic gases, and its foul smell is easy to cause discomfort.
Advantages and disadvantages of landfill:
Advantages of landfill: sanitary landfill technology is mature and the treatment cost is low, which is the main way of centralized treatment of urban garbage in China at present.
Disadvantages of landfill: less investment, simple process, large treatment capacity, and better realization of surface harmlessness. However, the buried garbage has not been treated harmlessly, leaving a lot of bacteria and viruses; Biogas also has hidden dangers such as heavy metal pollution; Garbage leakage will pollute groundwater resources for a long time, so this method is potentially harmful and will bring endless troubles to future generations. This method not only fails to realize the resource treatment of garbage, but also occupies a lot of land, which is a dangerous way to reserve pollution sources for future generations. At present, many developed countries explicitly prohibit landfill. The competent departments at all levels in China have gradually realized the problems existing in this treatment technology, and this kind of behavior will be banned and eliminated.
If it is a real landfill, what harm will it bring to the surrounding environment and what measures will be taken?
The leakage and release of landfill leachate and landfill gas will lead to various environmental problems, including potential health hazards, groundwater pollution, air pollution and greenhouse effect, vegetation destruction, fire and explosion, and the settlement of landfill itself.
Landfill gas: Landfill gas refers to the gas produced by anaerobic digestion and degradation of a large number of organic substances contained in municipal solid waste accumulated or landfilled during landfill. Landfill gas is a kind of mixed gas, and its generation and release are determined by the composition of garbage, the moisture status of garbage dump, the temperature, pH value, meteorological conditions, the age of garbage, the structure of garbage dump and environmental geology.
There are many ways to release landfill gas: on the one hand, it can diffuse into the atmosphere through the surface of landfill; On the other hand, landfill gas can spread laterally to the surrounding area of the landfill through geological structures in underground rock and soil, such as cracks, so that the landfill gas can be released into the atmosphere after moving away from the landfill.
What are the dangerous and harmful factors of sanitary landfill of domestic waste?
1 Impact of Secondary Pollutants in Landfill on Surrounding Environment The secondary pollutants produced by microorganism and chemical reaction in Landfill mainly include landfill gas and leachate.
1. 1 landfill gas refers to the gas produced by anaerobic digestion and degradation of a large number of organic substances contained in municipal solid waste accumulated or buried during landfill. Landfill gas is a kind of mixed gas, and its generation and release are determined by the composition of garbage, the moisture status of garbage dump, the temperature, pH value, meteorological conditions, the age of garbage, the structure of garbage dump and environmental geology.
There are many ways to release landfill gas: on the one hand, it can diffuse into the atmosphere through the surface of landfill; On the other hand, landfill gas can spread laterally to the surrounding area of the landfill through geological structures in underground rock and soil, such as cracks, so that the landfill gas can be released into the atmosphere after moving away from the landfill. The composition of landfill gas is mainly divided into three categories: (1) methane and carbon dioxide, and the total volume accounts for 95%~99% of the total landfill gas, of which methane accounts for 50%~70% and carbon dioxide accounts for 30%~50%.
According to statistics, during the life of landfill, about 100~200m3 landfill gas can be generated per ton of garbage. British landfills emit 2.2 million tons of methane every year, while American landfills emit 1 1.6 million tons of methane every year.
Methane and carbon dioxide are the main greenhouse gases, and their greenhouse effect will have a great impact on the global environment. The potential greenhouse effect of methane equivalent volume is 2 1 times that of carbon dioxide. With the increase of garbage output, methane emission from China landfill will increase from 3.38% in 2000 to 7. 19% in 2020. The control and utilization of landfill gas has become an important issue in municipal waste management.
The density of carbon dioxide is 0.5 times that of 65438+ air and 2.8 times that of methane, which tends to move to the bottom of landfill and may eventually accumulate at the bottom of landfill. (2) Sulfide and ammonia nitrogen account for about 5% of the total volume of landfill gas; This gas is the main cause of odor around the landfill. As long as the air contains hydrogen sulfide, sulfur dioxide or mercaptan with the volume concentration of 1* 10-5, people can smell the odor.
The odor pollution range produced by landfill is generally less than 2km, and the odor range can reach more than 6km under unfavorable inversion conditions. The investigation results of 329 municipal solid waste disposal sites in China show that the over-standard rate of hydrogen sulfide in unorganized waste gas of each landfill is 7.6%, and the over-standard multiple is 0.5~24.
(3) Trace gases, with various types and complex components, mainly include some trace volatile organic compounds (VOCs), such as aromatic hydrocarbons, aliphatic hydrocarbons and other trace gases, totaling 100. Young et al. determined the trace VOCs in the air of three landfills in Britain, and * * * detected 154 compounds, among which 1 16 compounds could be detected in all landfills.
The California Air Resources Board investigated 66 landfills, and all of them detected toxic and harmful organic pollutants such as benzene, toluene, trichloroethylene, chloroform and vinyl chloride. Zou Shichun and others conducted qualitative and quantitative analysis of VOCs in the air of a landfill in Guangzhou. The results showed that 17 was the first pollutant controlled by the US Environmental Protection Agency (USEPA), and the concentration of benzene and alkylbenzene compounds was the highest, which was 2.54 ~ 1.508.48 g/m3.
Although the volume percentage of trace gases in landfill gas is less than 1%, these gases are highly volatile and toxic, causing serious environmental pollution, and their potential toxicity has attracted widespread attention. The distribution law of harmful gas concentration in the air of #p# paging title #e# landfill site is roughly as follows: the newly-built landfill site is higher than the buried site, the in-site site is higher than the off-site, the low-lying site is higher than the high-lying site, and the downwind site is higher than the windward site.
The release of landfill gas has a negative impact on the surrounding environment of landfill, and its potential explosion danger has great harm and threat to the health and safety of landfill workers. In recent years, there have been many casualties caused by landfill gas explosion and combustion.
1.2 Landfill Leachate Landfill Leachate refers to a kind of sewage with high concentration of suspended solids and organic or inorganic components, which is filtered out through biological and chemical degradation, shower and scouring of rainwater and soaking of surface water and groundwater during storage and landfill. The particularity of its formation leads to the complexity of its water quality. Organic matter in landfill leachate can be divided into low molecular weight fatty acids, medium molecular weight fulvic acid and humus high molecular weight carbohydrates.
At present, many scholars at home and abroad have analyzed the organic components in leachate, and the results show that the percentage of organic pollutants in leachate is complicated, including alkanes and aromatics, and there may also be some acids, alcohols, phenols, ketones, aldehydes, amides and so on. Many components are synthetic organic compounds that have never appeared in nature in the past, and a considerable number of compounds are toxic organic pollutants that cause cancer, promote cancer and help cancer. Especially when domestic waste is mixed with some industrial waste, the composition is more complicated.
Zheng et al. sampled and analyzed the Datianshan landfill in Guangzhou, and found 77 main organic pollutants in the leachate, including 29 aromatic hydrocarbons, 18 alkane olefins, 8 acids, 5 esters, 6 alcohols and phenols, 4 ketones and aldehydes, 2 amides and 5 others. These 77 kinds of organic pollutants contain 1 confirmed carcinogen, and its relative content ranks first among 77 kinds of organic pollutants, and there are 5 kinds of carcinogens or auxiliary carcinogens.
Pirbazari et al. studied the leachate of West Covina landfill, and also detected 18 special organic substances. Most of the heavy metals in leachate exist in the form of compounds or complexes, and the specific forms are closely related to the pH value of sewage and the concentration of organic matter in water.
Generally speaking, the concentration of metal ions in leachate of domestic waste landfill is usually low, but the dissolution of heavy metal ions in landfill mixed with industrial waste and domestic waste is obviously increased. Jensen et al. studied the contents of heavy metals in leachate from four landfills in Denmark.