Solid waste

The treatment and disposal of solid waste should follow the principles of reduction, harmlessness, and resource utilization. Reduction: composting of organic solid waste, fermentation of biodegradable organic waste to produce biogas, microbial decomposition techniques for waste cellulose (hydrolysis, saccharification, and proteinization techniques), pyrolysis of solid waste ； Harm reduction: stabilization treatment, land disposal, sanitary landfilling of household waste, safe disposal of hazardous waste, safe disposal of radioactive solid waste ； Resource utilization: Recycling recyclable materials. With technological advancements and increasing shortages of resources, the recycling of solid waste will be the ultimate direction for development.

Treatment of solid waste generally refers to the process of converting solid waste into a form suitable for transportation, storage, utilization, or disposal through physical, chemical, biological, physicochemical, and biochemical methods. The goals of solid waste treatment are to render it harmless, reduce its volume, and recover resources from it. Some people consider solid waste to be the most difficult type of waste to handle among the \"three types of waste,\" as it contains quite complex components, and its physical properties (such as volume, fluidity, uniformity, degree of fragmentation, moisture content, calorific value, etc.) vary greatly. Achieving the goals of \"harmlessness, reduction, and resource utilization\" for such waste presents considerable challenges. Common methods for preventing solid waste pollution start with controlling its generation; for example, gradually reforming the urban fuel structure (including that used in industry), controlling the consumption of raw materials in factories, extending the useful life of products, and increasing the rate of waste recycling ； Next is the implementation of comprehensive utilization, treating solid waste as resources and energy; for waste that cannot be utilized, it is compressed and rendered non-toxic before becoming final solid waste, which is then landfilled or dumped at sea. The main methods currently used include compaction, crushing, sorting, solidification, incineration, and biological treatment. ⑴Compaction technology. Compaction is a pretreatment technique that reduces the volume of waste, lowers transportation costs, and extends the lifespan of landfills. It is a widely used method for preprocessing solid waste; items such as cars, aluminum cans, and plastic bottles are usually subjected to compaction first. Solid waste that can be reduced in volume through compaction is suitable for this treatment, while certain types of waste that may cause operational problems, such as tar, sludge, or liquid materials, are generally not suitable for compaction. ⑵Crushing technology. To reduce the size of waste entering incinerators, landfills, composting systems, etc., solid waste must first be crushed. The waste that has been crushed has uniform dimensions as well as a uniform texture, since large gaps have been eliminated; it is then compacted during the landfilling process. There are many methods for crushing solid waste, including impact crushing, shear crushing, compression crushing, and friction crushing. In addition, there are also specialized methods such as low-temperature crushing and hybrid crushing. ⑶Sorting technology. Solid waste sorting is an important method for achieving the resource utilization and reduction of solid waste; through sorting, useful materials are properly selected for use, while harmful materials are properly separated ； Another approach is to separate waste materials of different particle sizes; the basic principle of sorting is to utilize differences in certain properties of the materials in order to separate them. For example, separation is achieved by utilizing the differences in magnetism and non-magnetism among waste materials ； Separation using differences in particle size ； Separation using differences in specific gravity, etc. Depending on their properties, various machines can be designed and manufactured to sort solid waste; such sorting methods include manual picking, screening, gravity separation, magnetic separation, eddy current separation, optical sorting, etc. ⑷Curing treatment technology. Solidification technology is a harmless treatment process that involves adding a solidifying matrix to waste in order to fix or enclose hazardous solid waste within an inert solidifying matrix. The resulting solidified product should possess good impermeability, mechanical strength, as well as resistance to leaching, as well as resistance to changes in humidity and freeze-thaw conditions. Depending on the type of solidifying matrix used, solidification treatments can be classified into sedimentation solidification, asphalt solidification, glass solidification, and gelatinous solidification, among others. ⑸Incineration and pyrolysis technologies. The incineration method is a comprehensive treatment process that involves the high-temperature decomposition and deep oxidation of solid waste; its advantage is that a large amount of hazardous waste is decomposed into harmless substances. As the proportion of combustible materials in solid waste is increasing, it has become an essential trend to use incineration as a method for dealing with solid waste, taking advantage of its thermal energy. With this treatment method, less space is required, and a large volume of waste can be processed; it also helps in environmental protection. Incineration plants are typically located in large cities with populations of over 100,000, and they are equipped with energy recovery systems. Due to land scarcity in Japan, the use of incineration is increasing gradually. The heat generated during the incineration process can be used for power generation, while the heat produced by incinerators can be utilized to heat homes and maintain temperatures in greenhouses. Currently, Japan and Switzerland incinerate over 65% of their municipal waste each year to recover energy. However, the incineration method also has disadvantages, such as high investment costs, secondary pollution caused by smoke emissions during the incineration process, and severe equipment corrosion. Pyrolysis involves heating organic materials at high temperatures (500°C–1000°C) in an anaerobic or oxygen-deficient environment, causing them to decompose into gas, liquid, and solid products. Compared to incineration, pyrolysis is a more promising treatment method, and its most significant advantage is the lower cost of infrastructure investment. ⑹Biological treatment technology. Biological treatment technologies make use of microorganisms to decompose organic solid waste, rendering it harmless. These technologies can convert organic solid waste into energy, food, feed, and fertilizer; they can also be used to extract metals from waste materials and residues. They represent effective methods for the resource utilization of solid waste. Some of the commonly used techniques include composting, biogas production, saccharification of waste cellulose, conversion of waste fibers into feed, and biological leaching. The recycling value of solid waste: By sorting and recycling waste, we can achieve efficient comprehensive utilization of resources, achieving twice the result with half the effort. Recycling efforts depend on the degree of sorting and the amount of waste accumulated; the recycling of solid waste holds great historical significance.

Solid waste is divided into: hazardous solid waste and non-hazardous solid waste. Hazardous solid waste is generally handled by specialized companies. Non-hazardous solid waste can be handled by recycling centers or sanitation departments. :victory: :victory: :victory:

The treatment of solid waste in small and medium-sized enterprises has not yet received the same level of attention as wastewater and exhaust gas emissions, and the requirements set by environmental protection authorities are not particularly strict. Currently, the industry dedicated to the proper handling of solid waste will see its market expand as there is increasing emphasis on environmental protection, thereby enabling the effective recycling of waste.