Solid waste treatment usually refers to the process of converting solid waste into something suitable for transportation, storage, utilization or disposal through physical, chemical, biological, physicochemical and biochemical methods. The goals of solid waste treatment are harmlessness, reduction and resource utilization. It is generally collected and disposed by professional solid waste disposal units. You can check it out on Weihui.com. There is a lot of information about solid waste disposal companies, which can help you compare prices and select a cost-effective disposal unit. Currently, the main methods used include compaction, crushing, sorting, solidification, incineration, biological treatment, etc.
1. Compaction technology
Compaction is a pretreatment technology that reduces the volume of waste, reduces transportation costs, and extends the life of the landfill. Compaction is a commonly used solid waste pretreatment method. For example, cars, cans, plastic bottles, etc. are usually compacted first. Solid waste suitable for compaction and volume reduction processing also includes garbage, loose waste, paper tapes, cartons and certain fiber products. Wastes that may cause damage to compaction equipment should not be compacted. Some wastes that may cause operational problems, such as tar, sludge or liquid materials, are generally not suitable for compaction.
2. Crushing technology
In order to reduce the size of waste entering incinerators, landfills, composting systems, etc., solid waste must be crushed in advance. The crushed waste not only has a uniform size but also has a uniform texture due to the elimination of large gaps, making it easier to compact during the landfill process. There are many crushing methods for solid waste, including impact crushing, shear crushing, extrusion crushing, friction crushing, etc. In addition, there are also special low-temperature crushing and wet crushing.
3. Sorting technology
Solid waste sorting is an important means to realize the resource utilization and reduction of solid waste. Through sorting, the useful ones will be fully selected and utilized, and the waste will be fully utilized. The harmful ones are fully separated; the other is to separate wastes of different granularity levels. The basic principle of sorting is to use the differences in certain properties of materials to sort them. For example, the difference between magnetic and non-magnetic properties in waste is used for separation; the difference in particle size is used for separation; the difference in specific gravity is used for separation, etc. According to different properties, various machines can be designed and manufactured to sort solid waste. Sorting includes manual picking, screening, gravity sorting, magnetic sorting, eddy current sorting, optical sorting, etc.
4. Solidification Technology
Solidification technology is a harmless method that fixes or contains hazardous solid waste in an inert solidification substrate by adding a solidification substrate to the waste. chemical processing process. It is understood that the cured product should have good penetration resistance, good mechanical properties, as well as leaching resistance, dry-wet resistance, and freeze-thaw resistance. Such solidified products can be disposed of directly in safe landfills, and can also be used as basic materials for buildings or subgrade materials for roads. Curing treatment can be divided into cement curing, asphalt curing, glass curing, self-gel curing, etc. according to the different curing substrates.
5. Incineration and pyrolysis technology
The incineration method is a comprehensive treatment process of high temperature decomposition and deep oxidation of solid waste. The advantage is that a large amount of harmful waste materials are decomposed into harmless substances. As the proportion of combustibles in solid waste gradually increases, it has become an inevitable development trend to use incineration methods to treat solid waste and utilize its heat energy.
This method of treating solid waste occupies less space and has a large processing capacity. It can achieve good results in protecting the environment and providing energy. European countries were the first to adopt incineration methods to deal with solid waste. Most incineration plants are located in large cities with a population of more than 100,000 and are equipped with energy recovery systems. Due to land shortage in Japan, the use of incineration method is gradually increasing. The heat energy obtained from the incineration process can be used to generate electricity. The heat generated by the incinerator can be used to heat residents and maintain room temperature in greenhouses. Currently, Japan and Switzerland incinerate more than 65% of municipal waste every year to regenerate energy. However, the incineration method also has disadvantages, such as large investment, secondary pollution caused by smoke exhaust during the incineration process, and serious equipment corrosion.
Pyrolysis is to heat organic matter at high temperature (500-1000C) under anaerobic or anoxic conditions to decompose it into gas, liquid and solid products. Compared with incineration, pyrolysis is a more promising treatment method. Its significant advantage is low infrastructure investment.
6. Biological treatment technology
Biological treatment technology uses microorganisms to decompose organic solid waste to render it harmless. Various technologies can convert organic solid waste into energy, food, feed and fertilizer, and can also be used to extract metals from waste products and waste residues. It is an effective technical method for solid waste resource utilization. At present, the widely used ones include: composting, biogasification, waste cellulose saccharification, waste fiber feed conversion, bioleaching, etc.
Solid waste that cannot be utilized or processed due to technical reasons or other reasons is final solid waste. The disposal of final solid waste is the final step in controlling solid waste pollution and solving the problem of the fate of solid waste. The purpose and technical requirements of disposal are to isolate solid waste from the biosphere in the environment to the greatest extent possible, and to avoid or reduce the pollution and harm to the environment caused by the pollution components in it.
Final solid waste can be divided into two categories: marine disposal and land disposal.
1. Ocean disposal
Ocean disposal is mainly divided into two methods: ocean dumping and ocean incineration. Ocean dumping is a disposal method that puts solid waste directly into the ocean. It is based on the fact that the ocean is a huge waste receptor and has the ability to greatly dilute pollutants.
When conducting ocean dumping, the disposal site must first be selected in accordance with relevant legal provisions, and then the technical feasibility shall be determined based on the oceanographic characteristics of the disposal area, marine protection water quality standards, types of waste to be disposed, and dumping methods. Research and economic analysis, and finally dump according to the designed dumping plan. Ocean incineration is a disposal method that uses incineration ships to incinerate solid waste on board. The waste gas generated after waste incineration passes through the purification device and condenser, the condensate is discharged into the sea, the gas is discharged into the atmosphere, and the residue is dumped into the ocean. This technology is suitable for the disposal of flammable wastes, such as chlorine-containing organic wastes.
2. Land disposal
There are many methods of land disposal, including landfill, land cultivation, deep well irrigation, etc. Landfill is a disposal technology developed from traditional stacking and landfill disposal. It is currently the main method of solid waste disposal.
According to law, it can be divided into sanitary landfill and safe landfill. Sanitary landfill is a disposal method that disposes general solid waste so that it will not cause harm to public health and safety. It is mainly used to dispose of municipal waste. The waste transported to the landfill is usually spread into a thin layer of a certain thickness in a limited area and then compacted to reduce the volume of the waste. After each layer is covered with soil and compacted. Compacted waste and soil cover form a single unit. A series of interconnected units of the same height form an elevated level. A complete sanitary landfill consists of one or more risers. During the selection, design, construction, operation and closure of sanitary landfill sites, issues such as preventing leachate leakage, controlling the release of degradation gases, eliminating odors and pathogenic bacteria, and developing and utilizing the site should be considered.
The safe landfill method is a further improvement of the sanitary landfill method and has stricter technical requirements for site construction. Landfills must be equipped with man-made or natural linings; the lowest layer of landfills must be located above the groundwater level; appropriate measures must be taken to control and divert surface water; leachate collection, treatment and monitoring systems must be equipped, and cover Materials or linings should be used to control possible gases to prevent the release of gases; the source, nature and quantity of wastes disposed of should be recorded and incompatible wastes should be disposed of separately.