China's urban garbage treatment started very late, and it didn't start until 1980s. In the past, garbage was piled up in the open air.
According to the data of the Municipal Solid Waste Treatment Committee of China Environmental Protection Industry Association, before 1990, the municipal solid waste treatment rate in China was less than 2%. Since the 1990s, the level of urban garbage disposal in China has been continuously improved. From 65438 to 0999, there were 668 cities and 696 garbage treatment plants (sites) in China, including less than 200 harmless treatment plants. The garbage disposal rate is 63.4%, and the harmless disposal rate is only 20.3%.
At present, there are more than 700 harmless treatment plants of municipal solid waste in China, and the harmless treatment rate of municipal solid waste in China is 52%.
Garbage disposal in China should be collected first. At present, the collection method of municipal solid waste in China is basically mixed collection. Although our government advocated classified collection in 2002, it only accounts for 16% at present.
There are three main ways of mixed collection. One is to put the collection containers in fixed places, such as residential areas, streets and other public places. Every day, special sanitation personnel are responsible for collecting the garbage in these containers. Second, there are fixed garbage collection stations in residential areas, and residents can throw their domestic garbage into the garbage stations every day. The third is the garbage chute. In China's high-rise residential buildings, the garbage chute was designed when the building was built, from the first floor to the top floor. Residents can throw the garbage into the garbage chute, and the sanitation personnel take it away from the ground floor. Collecting domestic garbage through garbage tunnels used to be the most common garbage collection method in residential areas. However, after the outbreak of SARS in 2003, garbage tunnels were banned in many cities because they were conducive to the spread of bacteria. Beijing, Guangzhou, Shanghai and other cities have successively stipulated that garbage lanes should not be set up in new houses, and some cities have also closed garbage lanes in existing houses.
The collected garbage is transported to the garbage transfer station by a special garbage truck. The garbage truck is completely sealed. After the garbage is transported to the transfer station, it needs to be treated in the first step. First of all, it is classified by classifier, which is divided into organic and inorganic, usable and unusable. It is necessary to compress the large-capacity garbage. After that, the garbage is sorted and transported away.
Part of the garbage transported from the transfer station is transported to the sanitary landfill, and the garbage is filled into the prepared pit, covered and compacted, so that it will undergo biological, physical and chemical changes and decompose organic matter to achieve the purpose of reduction and harmlessness. These pits are paved with special pipes and impervious layers to collect the gas and leachate produced by garbage fermentation. After gas combustion, some leachate is purified into reclaimed water, which is used to clean garbage vehicles and ground dust. Some leachate will be discharged after reaching the national first-class standard after filtration, which will not cause pollution to the environment.
Others are transported to composting plants. After composting, domestic garbage becomes sanitary and odorless humus, which is used as fertilizer for plants.
Part of it is sent to the incinerator for incineration, so that the combustible components in the garbage are fully oxidized, and the generated heat is used for power generation and heating. At present, there are 140 garbage power plants built, under construction and being submitted for approval in China. A ton of garbage can generate 300 degrees of electricity, and the waste heat can also be used for heating. Tianjin Shuang Gang Garbage Power Plant has a daily garbage disposal capacity of 1.200 tons and an annual power generation capacity of1.200 million kWh, which can supply power to 50,000 households for one year, equivalent to saving 48,000 tons of standard coal.
For recyclable garbage, it will be recycled.
In the process of garbage disposal, China has formulated many relevant standards, such as the agricultural control standard of urban garbage, the sanitary standard of harmless feces, and the emission standard of incineration waste gas.
Among the current garbage disposal methods, incineration develops slowly in China, mainly due to the shortage of funds. The initial investment of incineration treatment is large, and it will cost about 700-800 million yuan to build an incinerator with a daily garbage treatment capacity of 1 000 tons and attached heat energy recovery equipment. Moreover, due to the dioxin gas generated when incinerating garbage, many cities do not use incineration to treat garbage except for the need of treating medical garbage. Many cities use sanitary landfills more, which environmental officials think is more suitable for China's national conditions.
According to the data of the Municipal Solid Waste Treatment Committee of China Environmental Protection Industry Association, at present, 70% of municipal solid waste in China is treated by landfill, 20% by composting, 5% by incineration and 5% by other treatments (including open-air stacking and recycling).