sanitary landfill has always played an important role as the final disposal method of garbage, and it is still the main way of garbage disposal in most countries, including China. However, although environmental protection engineering measures such as anti-seepage, compaction, covering and collection have been adopted in sanitary landfill, some characteristics such as large landfill height difference and large gas production still pose a potential threat to the safe operation of landfill. In foreign countries, such as Turkey and the Philippines, there have been tragedies in which the landslide of garbage dump caused a methane explosion and buried the whole village. In China, in 22, a landslide occurred in Liangfengya landfill site in Chongqing, causing heavy casualties and property losses. Therefore, how to do a good job in the safe operation of landfill to ensure the normal operation of landfill and prevent environmental pollution and personal and property damage is an important topic before us.
As the first large-scale landfill site built according to the sanitary landfill standards of the Ministry of Construction in China and the national sanitary landfill demonstration project, Tianziling Waste Treatment Plant in Hangzhou has accumulated some experience in safe operation. Tianziling Waste Treatment Plant has a total investment of 11 million yuan (including 3 million yuan from Zhongjia Power Plant), covering an area of 48 hectares, with a total landfill capacity of 6 million cubic meters. Landfill is carried out in layers strictly according to units, and its process is leveling → compaction → covering soil, with a daily garbage disposal capacity of 1,5 ~ 4, tons and a service life of 13 years. The whole site is composed of landfill reservoir area, sewage collection and treatment system, groundwater pollution prevention system, environmental monitoring station, biogas power plant, weighbridge metering system and management living area.
In May, 1994, Tianziling Waste Treatment Plant cooperated with American Huimin Group to establish Zhongjia Environmental Technology Co., Ltd. to build a landfill gas power plant. The scale of the first phase project is 2 sets of 97KW units, and the final phase can reach 6 sets. On October 27th, 1998, the power plant was officially put into operation to generate electricity. This project has good economic, environmental and social benefits. It can not only prevent the secondary pollution of landfill gas, but also effectively eliminate the potential safety hazards caused by landfill and fill the domestic gap.
In recent years, Tianziling Waste Treatment Plant has also made active attempts in vegetation restoration of landfill sites. If bamboo is planted in the closed area of landfill, the survival rate can reach above 95%, which can not only prevent soil erosion and protect the ecological environment, but also improve the stability of landfill and produce certain economic benefits.
according to the design library capacity, the first landfill is close to saturation. The second landfill in Hangzhou with a total investment of 35 million yuan and a design service life of 24 years will start construction in the near future.
in the past 1 years, Tianziling Waste Treatment Plant has made some achievements in various aspects, and has been awarded the honorary titles of "the first type of national waste treatment promotion project", "the national excellent environmental management project", the title of "the best example of improving the living environment in Dubai in 2" by the United Nations, the first batch of key technical demonstration projects implemented by the Ministry of Construction, and the top ten pacesetter of "the national advanced group of city appearance and environmental sanitation" by the State Science and Technology Commission.
Take this as an example, and talk about several key points of safe operation of landfill.
first, the introduction of international management system is the guarantee of safe operation
since 22, Hangzhou Tianziling Waste Treatment Plant has introduced three management systems, namely ISO91, ISO141 and OHSAS181, and standardized the safe operation by establishing and maintaining a systematic, programmed and highly self-disciplined scientific management system. Therefore, the guidelines, objectives and safety and environmental management scheme of landfill are formulated. Among them, those related to ISO91 mainly include the design of landfill and the technical specifications of landfill operation; What involves ISO141 is mainly the management measures of important environmental factors in landfill; What is involved in OHSAS181 is the identification and evaluation of hazardous sources in landfills, and the control measures and management means for major hazardous sources. After the integration of the three management systems, more than 3 program documents such as Management Procedure of Landfill, Control Procedure of Methane Gas (Biogas), Management Procedure of Oils, Chemicals and Dangerous Goods, and more than 4 operation instructions such as Operation Specification for Bulldozers, Operation Instruction for Connecting Biogas Pipes in Reservoir Area, Emergency Plan for Handling Serious Accidents, and a series of records and tables have been formulated, which provide a safe operation for the landfill.
2. Standardized operation technology is the key to safe operation
The operation technology of landfill is the life of landfill, therefore, the key to safe operation of landfill is to standardize landfill operation.
according to the composition of landfill waste, the configuration of site compactor and the compaction times, the thickness of landfill unit layer should be controlled at 2-5 meters, and the maximum thickness should not exceed 6 meters; The thickness of each large layer can be set to 1 ~ 2 meters according to the total height; Compaction of landfill waste should be more than 6 kg/m3, preferably more than 8 kg/m3, so as to reduce the void ratio of waste, reduce water and air in the void and reduce settlement.
slope operation should be completed at one time as far as possible to avoid local landslide caused by repair; The garbage layer can have waves caused by settlement, so that there is interaction between layers; It is necessary to cover the landfill in time, reduce the rainfall entering the garbage layer and avoid the instability of the garbage layer due to too much rain.
3. Setting the air guide and drainage system is the basis of safe operation
The water and air in the garbage have a significant influence on the stability of the pile. The landfill site must be equipped with an effective air-guiding and seepage-discharging system to discharge the water and air in the pile. Generally, blind ditches, gabions, flood discharge wells and exhaust wells can be used to guide and discharge the interior of the pile. The rainwater and sewage are separated by flood intercepting ditch to prevent rainwater from entering the pile. Build drainage ditches on each platform to prevent the slope from being washed by rain.
Because the commercial utilization value of landfill gas is not great in general landfills, the landfill gas can be channeled, collected and discharged into the sky by gas guide system, or ignited and removed by automatic igniter, and can also be used for heating green greenhouses. Larger landfills can consider using biogas to generate electricity. For example, Hangzhou Tianziling Zhongjia Power Plant, the first domestic power generation plant using landfill gas, has two 97 kW units, which reduces landfill gas by nearly 1 million cubic meters annually, with an annual output value of more than 8 million yuan, which not only greatly reduces the safety hazards of landfill sites, reduces the odor in the reservoir area, but also creates good social, environmental and economic benefits.
4. Vegetation restoration is a beneficial supplement for safe operation
Covering the final site area with .8 ~ 1m thick cohesive soil in time and vegetation restoration can not only prevent rain from washing, but also play a role as a reed net on the slope, prevent the formation of sliding camber, enhance the integrity of discrete garbage bodies and improve the stability of garbage bodies.
5. Strengthening monitoring and inspection is a powerful guarantee for safe operation
Strengthen the monitoring of the stability of the garbage dump, and regularly observe the left and right displacement of the pile with an goniometer and the elevation change of the pile with a level. Select 1 representative points in the reservoir area for inspection and measurement every week. All these can play an early warning role in order to take effective measures to prevent accidents.
according to the latest technical standards for urban garbage treatment and prevention formulated by the Ministry of construction, the methane concentration should not exceed 5%. This value refers to the index of the Environmental Protection Agency of the United States, that is, the methane concentration in the air is 5% as the lower limit of explosion, and when the concentration reaches 5% ~ 1%, an explosion will occur. Although the methane concentration in landfill is generally between 1% and 2% when gas guide and exhaust facilities are installed, it does not rule out that the methane concentration will exceed 5% in specific locations and specific climatic conditions. Therefore, it is particularly important to strengthen the monitoring of methane concentration in the reservoir area and check the fire ban in the reservoir area.
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