1. Landfill treatment

Landfill is an effective method to absorb a large amount of municipal solid waste, and it is also the final disposal method of all the residues in the garbage treatment process. At present, the direct landfill method is widely used in China.

The so-called direct landfill method is to fill the garbage into the prepared pit, cover and compact it, make it undergo biological, physical and chemical changes, decompose organic matter, and achieve the purpose of reduction and harmlessness.

However, most of the garbage in many cities in China is still piled up in the open air without any protective measures. Every garbage dump has become a source of pollution. Mosquitoes and flies are rampant, rats are infested, and the smell stinks. A large amount of garbage and sewage seeped into the ground from the surface, which caused serious pollution to the urban environment and underground water sources. In Shenyang, 10 of 35 landfill sites was drilled and sampled, and the fault samples of waste and groundwater quality were analyzed. The analysis results show that:

1, the groundwater quality deteriorated, the pollution was serious, the water quality was turbid and smelly, and anaerobic Escherichia coli was detected in the water;

2. Toxic and harmful substances were detected in the faulty samples of garbage. Every day in Shanghai, 10,000 tons of garbage are transported to the suburbs and piled up at the seaside. The garbage mountain as high as twenty or thirty meters has caused serious pollution to the surrounding environment.

Landfill is one of the most common garbage disposal methods, which is characterized by low cost and simple method, but it is easy to cause secondary pollution of groundwater resources. With the increase of urban garbage, there are fewer and fewer suitable landfills near the city, and the opening of long-distance landfills has greatly increased the cost of garbage discharge, even unbearable.

2. Incineration treatment

Incineration is a method of putting garbage into a high-temperature furnace to fully oxidize the combustible components in it, and the generated heat is used for power generation and heating. The garbage conversion energy system jointly developed by Westinghouse and O 'Connor Company has been successful. The incinerator of this system can convert garbage with humidity of 7% into dry solid for incineration, and the incineration efficiency is over 95%. At the same time, the high temperature on the surface of the incinerator can convert heat energy into steam, which can be used for heating, air conditioning equipment and steam turbine power generation.

The advantages of incineration treatment are good reduction effect (after incineration, the residue volume is reduced by more than 90%, and the weight is reduced by more than 80%), and the treatment is thorough. However, according to American reports, the construction and production costs of incineration plants are extremely expensive. In most cases, the value of electricity generated by these devices is far below the expected sales, leaving huge economic losses to the local government. Because garbage contains some metals, incineration is highly toxic and will cause secondary environmental harm. Incineration requires the calorific value of garbage to be greater than 3.35MJ/kg, otherwise combustion improver must be added, which will increase the operating cost to an unbearable level for ordinary cities.

3. Composting treatment

Domestic garbage is stacked, stored and fermented at 70℃, and organic matter is decomposed into inorganic nutrients by the decomposition ability of microorganisms in garbage. After composting, domestic garbage becomes sanitary and odorless humus. It can not only solve the way out of garbage, but also achieve the purpose of recycling. However, domestic waste compost has a large amount and low nutrient content, so long-term use is easy to cause soil hardening and groundwater deterioration. Therefore, the scale of compost is not easy to be too large.

Whether it is landfill, incineration or composting, pretreatment is essential.