Three principal methods of waste disposal
Categories: Solid Waste Disposal
Three principal methods of waste disposal
There are three principal methods of solid waste disposal in addition to recycling, they are Landfill,
1. Landfill
Landfill is an effective method to consume a large number of municipal solid waste, but also a disposing method of all the residue from the final waste treatment processes At present, direct landfill is widely used in China.
The so-called direct landfill is putting the waste into a good pit has been prepared then covered and compact, to let it bring about biological, physical, chemical changes, decomposition of organic matter, to achieve reduction and harmless purposes.
There is a mountain filled with garbage in the south of Water Park in Tianjin city of China, which is creating an artificial environment, change harm into advantage, the project covers an area of nearly 80 million square meters, the source of mountain solid are mixed garbage and construction waste soil at the rate of 1:1, for the infiltration filtrate and fermentation biogas and slope stability, have taken the necessary measures.
Kansas City in United States is a small city, and the population is small, this city is surrounded by vast rural areas, an election to build the landfill in a low-lying hills and far away from the city’s, in order to prevent the secondary pollution, measures were taken as follow:
(1) Covered with impermeable layer under and around the bottom;
(2) Hierarchical placement, that is, a layer of garbage piling up, and then covered with earth compaction, according to the introduction, some garbage piling up layer also installed air conductivity and aqueduct channel, and use of it to produce biogas.
There is a dense forest in Koto-ku, Tokyo, Japan, which is a lush land with flowers and grass, known as the “Dream Island”, this dream island is created by waste reclamation.
However, many of our cities are still take outdoor garbage piling up mostly, without any protective measures. Each garbage dumps have become a source of pollution, mosquitoes breeds , rats disaster, the smell filled everywhere, a large number of waste water penetrate from the surface into the underground, cause serious pollution to the urban environment and the groundwater sources. Shenyang city has 10 in 35 landfill as the drilling samples inorder to analysis the waste samples and quality of ground water fault, and the analysis found that:
(1) The quality of ground water was deteriorated, polluted seriously, water turbid smelly, anaerobic E. coli were detected in the water;
（2）Hazardous substances were detected in samples of waste. There are tons of garbage transported to the seaside suburb to pile up in Shanghai city every day, a pile of garbage mountain up to two-three meters is growing up, causing serious pollution to the surrounding environment.
Landfill is one of the most common waste disposal method, its greatest feature is the low processing costs, the method is simple, but likely to cause secondary pollution of groundwater resources. With the the amount of waste increased in the city, there are less and less applicable landfill sites close to the city, it will increase the landfill waste discharge fees if open the landfill far away, so can not even afford this high cost.
2. Incineration
Waste incineration is placing the waste in high-temperature furnace, so that the combustible components can be made full of oxidation, the heat produced can be use for electricity generation and heating. Two U.S. companies named Westinghouse and Ao Kangnuo developed a waste-to-energy system jointly has been successful. The incinerator of this system can make the garbage may be up to 7% moisture into dry solid waste and then incineration, the efficiency rate of burning is more than 95%, while burning stove can heat the surface of the heat into steam for heating, air conditioning equipment and steam turbine power generation.
China’s Shijiazhuang City bulit a construction of incineration station, Institute of Environmental Science waste incineration plant in Shenyang city imported and a special equiment for hospital and othere units’ waste treatment and disposal from Japan, incineration ash residues generated in the process of burning account about 5% of the biological waste before burning by weight, which is high-quality fertilizer generally. In recent years, China pay more and more attention to the technologies of waste incineration renewable energy power generation.
Incineration has the advantage of reduction effect (the residue has more than 90% size reduction after burning, weight reduction of 80% or more) and the waste disposing is complete. However, according to U.S. reports the incineration plant construction and production cost is extremely expensive. In most cases, the electricity generated by the equipment value is far lower than expected sales to local government, leaving huge economic losses. As the waste contains some of the metal, its highly toxic during burning, resulting in secondary environmental hazards. The heat required of incineration of waste is greater than 3.35MJ/kg, otherwise, you must add accelerant, which will increase operating costs to the general point that the city unbearable.
3. compost
To pile the garbage into accumulation, keep the heat of 70 ℃, then storage, fermentation, with the ability of microbial decomposition of garbage has, decompose the organic matter into inorganic nutrients. After composting, the waste change into a sanitary, odorless humus. Not only a good way to solve the garbage, but also to achieve the purpose of recycling. However, the solid waste composting is too much amount, and the nutrient content is low, which could easily lead to soil compaction and deterioration of groundwater quality if long-term use, so the comosting scale can not be extended too much either.
Regardless of municipal solid waste landfill, incineration or composting, all of them must have a pre-processing. The most common pre-processing of waste is crushing. After crushed, the capacity can be reduced for landfill, for incineration crushing can make burning more fully , for compost crushing can make the garbage maturity faster.
