Keywords: municipal solid waste recycling technology pollution treatment
1. The present situation of municipal solid waste treatment and recycling technology in China
According to the idea of integrated management of municipal solid waste, the collection and transportation of municipal solid waste is also an important part of integrated management of municipal solid waste. At present, the collection and transportation methods of urban garbage in China are still in a relatively backward stage, and most of the domestic garbage is collected by mixing, but not by classification. On the one hand, mixed collection increases the quantity of urban garbage collection and transportation, and consumes more manpower, material resources and financial resources; On the other hand, it increases the technical difficulty, engineering investment and operation cost of municipal solid waste treatment, which is not conducive to the reduction, recycling and harmless treatment of municipal solid waste. At present, there are three kinds of recycling technologies: landfill treatment, composting treatment and incineration treatment. The following is an analysis of the status quo of the three technologies.
(1) Present situation of municipal solid waste landfill treatment
For a long time, most cities in China have used open-air stacking, natural ditch filling and pit filling to absorb municipal solid waste, which not only encroached on valuable land resources, but also caused potential impact and harm to the environment. In particular, the leachate of municipal solid waste from landfills is not collected and treated, which leads to serious pollution of water resources and its environment. Since the end of 198s, China's municipal solid waste landfill technology has developed to a certain extent, and a number of relatively complete municipal solid waste sanitary landfills (or quasi-sanitary landfills) have been built one after another throughout the country. In these sanitary landfills (or quasi-sanitary landfills), there are generally relatively perfect anti-seepage systems, leachate collection and treatment systems, landfill gas drainage systems, rainwater and sewage diversion systems, etc. Imported high-density polyethylene liners are also used in municipal solid waste sanitary landfills built in Shenzhen, Beihai, Beijing and Tianjin. However, at present, there are still many shortcomings in most municipal solid waste landfills in China, such as anti-seepage at the bottom of landfill, collection and utilization of landfill gas, collection and treatment of leachate, layered compaction of landfill operation, daily coverage and final recovery of landfill.
(2) Current situation of municipal solid waste composting
At present, the technology of municipal solid waste composting in China is in a relatively shrinking state. Practice has proved that compost produced by mixed collection of municipal solid waste has low fertilizer efficiency, many impurities and high cost, which is inconvenient for farmland production and affects its market development. Mechanized municipal waste composting plants in Wuxi, Hangzhou, Beijing, Shanghai and other places built during the Seventh Five-Year Plan period were closed down one after another for technical and market reasons. At present, some municipal waste composting plants with low mechanization and mainly adopting static aerobic fermentation technology are widely used in China. It is characterized by simple process, less mechanical equipment and low investment and operation cost, but at the same time, there are also some problems, such as low compost quality, the odor and sewage generated during composting are not effectively treated, and the urban garbage composting plant has a great impact on the surrounding environment. Reducing the cost of composting, improving the quality of composting products and opening up market channels are the key factors for the development of municipal solid waste composting technology, and the important condition affecting these factors is to realize the classified collection of organic waste.
(3) Present situation of municipal solid waste incineration treatment
Incineration treatment is a new hotspot of municipal solid waste treatment technology in China. Compared with developed countries, China's municipal solid waste incineration technology has just started, and it can't meet the growing needs at present. The huge market potential has attracted many enterprises to invest in the development of municipal solid waste incineration technology and equipment. On the basis of introducing foreign advanced technology and equipment to build China's first modern municipal waste incineration plant, Shenzhen has completed the localization project of No.3 incinerator in combination with the national "Eighth Five-Year Plan". The localization level of equipment has reached more than 8%, and the technical performance has reached or exceeded the level of the original imported equipment, laying a foundation for the localization of municipal waste incineration equipment in China. In the past three years, some economically developed cities in China, especially coastal cities such as Shanghai, Guangzhou, Beijing, Shenzhen, Zhuhai, Beihai, Ningbo, Xiamen, etc., are actively preparing for the establishment of municipal waste incineration plants. At present, the total scale of municipal waste incineration plants under construction and planned is about 1, tons/day, most of which are built by introducing technology and equipment. Most of the municipal waste incineration plants that have been built with domestic technology and equipment are at a low level, which makes it difficult to operate normally and meet the pollution control standards.
2. Analysis of the present situation of urban garbage disposal
At present, it is easy to discuss and analyze the problem of urban garbage disposal only in the way of disposal, and talk about urban garbage disposal. Generally speaking, the characteristics of municipal waste composition are high moisture (because of the high proportion of kitchen waste), high ash (high ash content in areas with low gas penetration rate) and low calorific value; The collection method is basically mixed collection. At present, the present situation of municipal solid waste treatment can be summarized as follows:
(1) Most municipal solid waste in most cities still adopts open-air stacking and simple landfill treatment, and the phenomenon of littering is quite common;
(2) In some areas, especially in the economically developed eastern coastal areas, there are fewer and fewer suitable sites for municipal solid waste landfill.
(3) Under the condition of mixed collection, municipal solid waste composting is difficult to develop, and it is still shrinking in some areas;
(4) Municipal solid waste incineration is still in its infancy. Domestic self-developed municipal waste incineration equipment is still immature, and the price of imported incineration equipment system is too high, which is unbearable for the economic strength of most cities. Without classified collection, according to the requirements of the Pollution Control Standard for Domestic Waste Incineration (GWKB3), it is suitable for municipal waste incineration facilities with high moisture content, high ash content and low calorific value. No matter whether it is domestically produced or independently developed, its engineering investment and operating cost are relatively high, and it is difficult to popularize it generally.
3. Problems in the recycling of municipal solid waste in China
The municipal solid waste in China is growing rapidly. By the end of 2, the annual removal volume of municipal solid waste exceeded 118 million tons. With the economic growth and the improvement of people's living standards, especially the optimization of civil fuel structure, the output and composition of municipal solid waste in China have also undergone fundamental changes. There are various indications that the utilization potential of municipal solid waste in China is huge
After analysis, there are the following problems in the utilization of municipal solid waste in China: ① The mixed recycling of municipal solid waste increases the difficulty of garbage utilization. China's municipal solid waste basically belongs to mixed recycling, and it needs a lot of manpower, material resources and financial resources to separate useful substances from the recycled garbage, which is not conducive to the recycling of municipal solid waste. ② The technology of recycling municipal solid waste is backward. There are more inorganic components than organic components, more combustible components than combustible components, more compostable components than compostable components in urban garbage in China, and there are differences among large, medium and small cities, so it is difficult to recycle and the economic benefits are poor. (3) Lack of funds for recycling municipal solid waste. The cost of municipal solid waste treatment in China mainly comes from the government, and the amount is limited, while the construction of large sanitary landfill plants or incineration power plants requires a lot of money, resulting in poor infrastructure for municipal solid waste resource utilization. (4) imperfect laws and regulations and poor management. At present, our country puts the emphasis on waste reduction, not paying enough attention to the recycling of waste, and there is no corresponding recycling method, so the management is poor, and the current management system is not conducive to the recycling of waste. ⑤ The awareness of resource utilization is weak. With the improvement of living standards, people's consumption concept changes, and the concept of resource recycling is weak and difficult.
4. Countermeasures for recycling urban garbage in China
To sum up, simply relying on a certain technology to treat urban domestic garbage is not the fundamental method to solve the garbage problem suitable for China's national conditions.
As far as the current situation is concerned, because China's policy on power generation by garbage incineration is not perfect, it is not yet mature to rely on garbage incineration to generate electricity, and the surplus power other than the factory's own electricity is sold online. Moreover, the calorific value of garbage is low, the installed capacity of incineration power generation is small, the power generation cost is high, and the electricity price is not competitive compared with conventional power generation. From the economic point of view, garbage incineration power generation is not the best way to recycle garbage.
garbage is a resource, which has become people's knowledge. Therefore, it is unscientific to simply "treat" garbage. We must adjust measures to local conditions, aim at the diversity of components in garbage, and make comprehensive utilization based on resource and energy recovery. Comprehensive utilization should include the following aspects
1) recycling of available materials (waste paper, metal, glass, etc.);
2) composting in Corruptible organics;
3) energy utilization of non-perishable organic matter with high calorific value;
4) Solidification treatment of ash and slag to realize the materialization of ash and slag.
At present, some domestic units have begun to try this aspect, but due to technical problems, the utilization efficiency of resources and energy is low, and the energy of garbage itself can not be used to solve the problem of high energy consumption in the process. The system has high operating cost and low technical content, which is not conducive to industrial promotion. The development of integrated garbage disposal system should aim at self-sufficiency of system energy. On the one hand, the production cost can be greatly reduced; on the other hand, the construction cost of the system can be greatly reduced by selecting a smaller installed power generation capacity, which is more suitable for the national conditions and has a broad market prospect, and the resulting social and economic benefits will be considerable.
References:
[1] Zang Wenchao. Present situation and management problems of municipal solid waste in China. Environmental protection, 1998, (8): 41 ~ 43
[2] Zhou Yuewei. Present situation and countermeasures of solid waste resource utilization in Beijing. Environmental protection, 1998, (9): 44 ~ 46. 12 (2): 9 ~ 11
[4] Fang Chuanglin. The direction of sustainable development and utilization of garbage resources in China. Environment, 1996, (9): 3 ~ 31
[5] Deng Xiaolong. Discussion on comprehensive treatment and recycling technology of urban garbage. Environment, 1998, (5): 38 ~ 38.