With the rapid development of the country's society and economy, the consumption of household appliances, automobiles and new building decoration materials has increased rapidly, and the application of plastic materials has been rapidly developed. At present, the annual consumption of plastics in the world has reached 260 million tons, and China's annual consumption of plastics is 45.78 million tons. In 2007, China imported 6.84 million tons of waste. It is estimated that the import volume will remain at the 2007 level in 2008; the domestic recycling volume will be about 8 million tons in 2007 and more than 9 million tons in 2008. The recycling of waste plastic materials is equivalent to the consumption of polymer in that year. 1/3 strong. Waste plastics have become one of the world's most important sources of waste, and the waste plastic materials themselves and their recycling and treatment processes have been unscientific and have had a huge adverse impact on the surrounding environment. In recent years, many countries have begun to pay attention to reducing the environmental pollution of waste plastics recycling and recycling processes.
Recycling Process Pollution Classification The main indicators for measuring the environmental impact of various processes in the waste plastics recycling process are: solid waste, wastewater, noise and waste gas.
Solid waste: mainly from waste generated by the cleaning process, sludge generated by wastewater treatment, activated carbon produced by waste gas treatment, and partially non-recyclable waste plastic.
Wastewater: It is the main source of pollution. The separation and cleaning of waste plastics produces a large amount of industrial wastewater, which is large in quantity, heavy in pollution and complex in composition.
The main indicators for evaluating waste liquid pollution are: oxygen balance (COD, BOD), heavy metal content (Pb, Hg, ag, au, Cr, Ni, etc.), indicators of organic and inorganic pollutants (phenols, lipids, oils, fluorine). Compounds, cyanides, chlorides, phosphates, etc.).
Noise: mainly refers to various mechanical vibrations, frictions, impacts such as crushers, noise generated by the sorting machine during the process of dismantling and recycling, and is measured by the noise value db.
Exhaust gas: The recycling process is not serious to the air pollution. The main reason is that PVC has some volatile substances and dust, which causes air pollution. In addition, the refrigerant, foaming agent (CFC, HCFC), etc. generated when the refrigeration equipment is recovered may destroy the ozone layer.
The environmental impact of the plastic recycling process refers to the sum of various emissions in all phases of the process. Table 1 lists the contaminants that may be present during the disposal of waste plastics. Table 1 Environmental impact factors in the recycling process of waste plastics.

Control measures <br> Solid waste impact prevention and control In order to prevent the spread of waste plastics and their adhering substances to the surrounding area, the waste plastic storage place should be effectively isolated from the ground and surrounding environment, and the accumulated mixed waste should be cleaned regularly. Harmful treatment.
Since most solid wastes are flammable, if they are not halogen-containing plastics, they can be directly incorporated into coal combustion as fuel for boilers and power plants; if they are halogen-containing plastics, they must be transported to waste incineration power plants to avoid air pollution. As a raw material for incineration.
Wastewater pollution prevention Wastewater pollutants are often adhering substances on waste plastics. The water pollution caused by the variety of waste plastics and the environment is different: 1. Suspended matter pollution: contact or packaging of cotton yarn, chemical fiber, quartz sand, cement, calcium carbonate, etc.; 2. Organic pollution: contact or packaging of food, feed 3. Beverage pollution: contact or packaging of oily substances; 4. solute contamination: contact or packaging of sodium chloride, soda ash, etc.; 5. color pollution: contact or packaging of dyes, etc.; 6.PH Value pollution: contact or packaging of strong acid and strong substances; 7. microbial pollution: mainly from disposable medical equipment or waste plastics after consumption; 8. toxic substances: contact or packaging toxic and hazardous substances.
At present, wastewater treatment methods are mainly divided into three categories: physical treatment, chemical treatment and biological treatment. The physical treatment method usually uses sedimentation, filtration, centrifugal separation, air flotation, evaporative crystallization, reverse osmosis and the like to separate pollutants such as suspended solids, colloids and oils from the wastewater to preliminarily purify the wastewater.
Chemical treatment usually uses neutralization, coagulation, redox, extraction, stripping, stripping, adsorption, ion exchange and electro-osmosis to separate and remove pollutants from wastewater.
The biological treatment method is divided into aerobic treatment and anaerobic treatment. Among them, the aerobic treatment method currently uses activated sludge method, biological filter and oxidation pond, etc.; anaerobic treatment method, also known as biological reduction treatment, is mainly used to treat high concentration organic wastewater and sludge, using digester Processing equipment.
For Class 1-3 wastewater, due to the absence of toxic and hazardous substances, physical treatment methods such as grid, screen filtration, fractional sedimentation, air flotation, etc. are usually used for discharge; for 4-8 wastewater, At present, most small and medium-sized processing enterprises in China do not have the processing capacity. From the perspective of development, it is a feasible solution to establish centralized and harmless disposal and sewage treatment facilities for such waste plastics.
In addition, the concentration of pollutants in wastewater is closely related to the nature of waste plastics, such as coarse materials, which contain many papers, soil particles and other debris, and are of various types of plastics. The amount of wastewater generated is large, and one ton of waste plastic is produced. The wastewater can reach 10 tons, and the waste water produced by the cleaning and crushing process has high content of organic matter and suspended matter, wherein the COD can reach 2000 mg/m3, and the SS can reach 500 mg/m3. For waste plastics using imported first-grade granular materials and secondary granular materials, the cleaning can be carried out. Even if it is cleaned, the amount of waste water produced per ton of waste plastics is only about 2 tons, the general COD is 500 mg/m3, and the SS is 200 mg. /m3. The biochemical experiments of wastewater show that the biochemical difference of wastewater produced by different waste plastics is large, but its biodegradability is generally not very good.
In actual production, the coagulation treatment process can be used to remove most of the suspended solids in the wastewater, and then the wastewater is reused in the production process to reduce the discharge of wastewater. The discharged wastewater can be mixed with domestic sewage to improve its biodegradability and discharged after biological treatment.
Noise pollution prevention and control of waste plastic recycling enterprises should be located in different residential areas, at the same time can consider the following measures: adjust production processes, improve mechanical precision; take high-altitude emissions or processing in a closed, semi-enclosed environment, increase the space of the control space, increase Operate the doors and windows of the site; use porous sound absorbing materials (glass fiber, slag wool, felt, etc.) to reduce noise by 5-10 decibels; work staff use personal protective equipment such as earplugs, earmuffs, anti-noise helmets, and perform noise operations Non-noise job rotation system.
Waste gas impact prevention and treatment enterprises should also be separated from residential areas. In addition to the large amount of volatile gases emitted during the processing of PVC, generally the waste gas produced by other waste plastics processing is very small, and is exhausted by using a fan.
Waste plastics contaminated with pollutants and pungent odors should be treated in a special processing manner to eliminate the pollution of heavy pollutants and irritating odors before entering the recycling process. The exhaust port of the fan is passed into a water tank containing alkaline substances, which can effectively remove irritating substances.
The source of organic waste gas is mainly from the process of granulation and open mixing. The high temperature mixing process will release a small amount of organic gas, mainly from the decomposition of some of the waste plastic into small molecules and some additives in the original plastic. A pungent odor should be disposed of properly.
The activated carbon adsorption method is used to treat the exhaust gas generated by low concentration, large air volume or intermittent operation, and the removal effect is better, and the activated carbon can be recycled and reused, and the adsorbed material is precipitated by steam, and the precipitated organic solvent is separated and treated to be harmless. emission. The collection of the gas collecting hood and the adsorption of organic gases by activated carbon can make the organic waste gas removal rate reach more than 90%.
When some of the waste plastics used for miscellaneous mixing are used for granulation, black smoke is generated due to high-temperature carbonization of the waste plastics, and the soot treatment process can be checked for the water hood treatment.
In addition, the industry should actively guide and support a number of scale and level of waste plastics processing bases, gradually cancel the workshop-type factories, improve the classification technology, and effectively reduce the environmental pollution of waste plastics recycling process.

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