Methods for solid waste treatment
In Vietnam in the coming years, the trend of solid waste treatment is different between large cities and provinces.
The purpose of waste disposal is to:
- Convert waste to a less toxic, more manageable form.
- Turning waste into other usable usable substances,
- Reduce the volume or volume to store more,
- Temporarily kept to wait for suitable technology.
Depending on the technology applied, the handling cost will vary. There is a treatment technology with low cost but in the process of processing generates secondary pollution. There are modern treatment technologies, high operating costs but safe handling, no smell, no secondary pollution. However, the management of solid waste is effective, limiting waste generation, reusing and recycling waste. In solid waste management, the priority order is arranged as follows:
- Reduce emissions,
Currently, in developing countries including our country, the methods of solid waste treatment are often applied as follows:
For domestic solid waste, with a large proportion of organic constituents is utilized to produce compost. However, because the waste classification process is not synchronized, only a part of domestic waste is bio-composted, the rest is still buried in concentrated landfills.
The components that are difficult to biodegrade but are flammable such as scrap paper, rags, plastics, rubber … are no longer recyclable, the combustion method can be applied to reduce the volume. Construction waste and incombustible components such as snail shells, stone bricks, crockery, etc., to be leveled or buried directly in burial sites.
- Method of incineration:
Incineration is the current popular method in the world to treat solid waste in general, especially for industrial hazardous solid waste and medical hazardous waste in particular. Handling exhaust fumes generated by incineration is a matter of particular concern. Depending on the composition of the exhaust gas, appropriate treatment methods can be applied such as chemical methods (precipitation, neutralization, oxidation, etc.), physical and chemical methods (absorption, adsorption, electrolytes). ), mechanical methods (filtration, sedimentation) …
Incineration of solid waste is the final stage of treatment applied to certain types of waste that cannot be treated by other means. This is a period of high temperature oxidation in the presence of oxygen in the air, in which toxic waste is converted into gas and non-flammable components. The exhaust gas generated during the incineration process is exhausted and released into the atmosphere. Ash and ash were buried.
The method of incineration is widely used in some countries such as Japan, Germany, Switzerland, the Netherlands, Denmark, etc. which have limited land for waste disposal sites.
Waste disposal by incineration method is important to minimize waste to the final stage of disposal of ash and slag. On the other hand, the energy generated during incineration can be utilized for boilers, furnaces or other industries that need heat and electricity. Each incinerator needs to be equipped with an exhaust treatment system to control air pollution caused by combustion.
Although incineration requires a high cost of disposal, it is often used to treat hazardous waste such as medical and industrial waste because these methods treat the pollutants fairly thoroughly. infected.
Waste incineration is usually carried out in specialized incinerators at high temperatures, usually from 850 to 1,100oC. The essence of the process is to conduct a fire reaction, which oxidizes waste by heat and oxygen from the air. Reaction temperature is maintained by adding energy such as electrical energy or heat generated when burning fuels such as gas, diesel …
Currently, in Vietnam, hazardous medical solid waste is mainly handled by small-capacity incinerators equipped for each hospital. However, large central hospitals under the Ministry of Health have well performed the collection, classification, transportation and treatment of medical waste. Hospitals at provincial and district levels, the treatment of medical waste depends heavily on the economic conditions of each province. The number of district hospitals equipped with incinerators that meet standards is very small. Therefore, medical waste is often burned by manual incinerators or buried in hospital grounds.
For industrial hazardous waste which is treated by incineration method, it is almost followed the burning principle of medical waste but the furnace capacity is larger. Currently, the industrial parks with concentrated investment in hazardous solid waste treatment areas are not concentrated. Hazardous solid wastes are often contracted by companies with functional companies and licensed to transport and handle hazardous solid waste. In Vietnam, urban environmental companies (abbreviated as URENCO) are still the leading units in hazardous solid waste treatment. The company researches, designs and manufactures large-capacity solid waste incinerators in several locations, serving the needs of surrounding waste treatment.
- Hygienic burial methods:
Among solid waste treatment and disposal methods in the world in general and in Vietnam in particular, landfill is the most common and simple method. This method has been widely applied in most countries of the world. In essence, landfill is a method of storing waste in an area and covering it with soil.
The landfill method is usually applied to municipal solid waste that is not used for recycling, ashes of incinerators and industrial wastes. The burial method is also commonly used to bury hazardous waste and radioactive wastes in burial sites with special designs for hazardous waste.
Sanitary landfill is a method of controlling the decomposition of solids as they are buried and covered with the surface. Solid waste in landfills will be decomposed by internal biodegradation to produce end products of nutrient-rich substances such as organic acids, nitrogen, ammonium compounds and some gases such as CO2 , CH4.
In the North, the Nam Son landfill site (Soc Son, Hanoi) is the largest landfill site, responsible for waste treatment for the whole Hanoi city. Each day the Nam Son landfill receives around 3,000 tons of garbage and may increase to 4,000 tons / day in the next 2 years. Currently, Nam Son beach has filled 6/9 burial compartments.
In Ho Chi Minh City, approximately 6,000 tons of garbage are brought to landfills every day. However, due to land fund and topography, there are many landfills in Ho Chi Minh City serving the city’s solid waste treatment.
The Go Cat landfill in Ho Chi Minh City was once the main landfill site of Ho Chi Minh City. However, the burial sites are now closed because the yards are full.
Although the Go Cat landfill has been closed, the garbage water treatment system, the gas recovery system and the generator equipment continue to operate.
In addition, Ho Chi Minh City has Phuoc Hiep landfill, belonging to the Northwest solid waste disposal complex. This landfill covers an area of over 22.8 hectares, with an average waste treatment capacity of about 3,000 tons / day, built with a total budget of over VND 197 billion. The treatment technology of this landfill is the hygienic landfill technology, the leachate at the site will be collected by HDPE pipe system and taken to the centralized wastewater treatment station, then discharged into Thay channel. Cai.
- Biological incubation method:
The process of biological composting applies to non-toxic organic matter, at first dewatering, then treatment until it becomes porous and moist. Humidity and temperature are controlled to keep the material in an aerobic state throughout the incubation period. The process of generating its own heat by biochemical oxidation of organic substances. The end product of the decomposition process is CO2, water and sustainable organic compounds such as lignin, cellulose, fiber …
For small scale (eg livestock farms), organic waste can be applied in composting bio-technology. For large scale industrial composting technology can be applied. The temperature, humidity and ventilation are tightly controlled so that the annealing process is optimal.
In Vietnam, Cau Dien Waste Processing Plant belonging to Hanoi Urban Environment One Member Company Limited (URENCO) is one of the leading factories in Vietnam in the field of composting biological waste. Organic waste for compost processing.
In addition, there is a Viet Tri waste processing factory in the North, now renamed and developed into a state-owned limited liability company of Phu Tho waste treatment and processing company with long-term experience. in the field of biological composting.
- Methods of recycling solid wastes:
Recycling activities have existed for a long time in Vietnam. Recyclable wastes such as metal, plastic and paper are sold by households to scrap collectors, and then transferred to craft villages. The technology of recycling waste in craft villages is mostly old and outdated, weak infrastructure, small-scale production leads to serious environmental pollution in some places. Some recycling villages are currently facing many pressing environmental issues such as Chi Dao commune (Hung Yen), Minh Khai commune (Hung Yen), paper manufacturing village of Duong O commune (Bac Ninh) … In general, Recycling activities in Vietnam are not systematically managed, but mainly by private establishments spontaneously.
Electronic waste is one of the most recyclable types of waste in Vietnam. Broken computers, televisions, locomotives are often sold to the waste collection team (junk, trash). These waste products are usually separated to gather components, or to retrieve metal and cases for resale to recycling facilities.
However, it is worth mentioning that the recycling technology at these facilities is too outdated. After the usable metals and electronic components were dismantled and sold or repaired, the rest was mostly burned or crushed and then added chemicals to create new products, which were single products. As simple as bottles, nylon bags in limited quantities.
Plastic recycling is also a potential industry in our country. Currently, Vietnam has more than 2,200 enterprises producing plastic products, about 80-90% of raw materials must be imported while the growth rate of this industry is from 15 to 20% per year. However, at present, the recycling of plastic on an industrial scale has not really been concerned about development. Plastic recycling facilities are mainly household-scale, concentrated in craft villages with outdated and manual technologies, thus causing serious environmental pollution such as Dong Mau trade village, Yen Dong commune, district. Yen Lac, Vinh Phuc province. The whole village has more than 40 plastic recycling facilities and dozens of households purchase plastic waste for recycling. Each month, the village recycles about 150-200 tons of plastic.
In addition, paper is also a recyclable material, but in Vietnam, the ratio of used paper to the total consumption of paper is only about 25%, very low compared to other countries in the region because There are many reasons: technology, costs, and legalization of production costs for complicated domestic paper collection, making domestic paper collection in progress.
Used paper after being recovered and transferred to the factory can be recycled into tissue paper for packaging, tissue paper, newsprint. Small-scale production facilities mainly use domestic collected paper to produce low-end products. In contrast, medium and large scale facilities mainly use used paper imported from abroad to recycle paper to serve higher quality products.
From 2000 to the present, many modern and synchronous production lines of pulp from recovered paper have been installed in Vietnam. In 2009, Vietnam put into production a number of new production lines with a total capacity of 190,000 tons / year. In addition, the old lines were upgraded with stages of grinding, sieving and separating fibers to bring higher powder efficiency and better powder quality. Technology used used paper in Vietnam is making positive changes, contributing to stimulate the development of waste paper collection and development of the domestic paper industry.
- Development trend of solid waste treatment technology:
The amount of solid waste and hazardous waste in Vietnam is increasing rapidly according to the development of the economy in general and industry in particular, especially in the two key economic regions of the North and the South. However, the problem of collection, transportation and treatment of hazardous waste in Vietnam is still inadequate. The number of capable and licensed units operating in the field of collection, transportation and disposal of hazardous waste is small and the capacity and qualifications of these units are weak, so the rate of low hazardous emissions. Therefore, many hazardous wastes, when gathering indiscriminately, burying unsatisfactory.
Currently, our country is in the process of developing integration with the world. On the other hand, the information age develops so that scientific and technological achievements are quickly applied. In the field of environmental protection, too, in Vietnam has been using the technology applied in the world.
5.1. Trend of solid waste treatment technology in the world
In developed countries, solid waste collection and management processes are completed due to the adequate facilities and techniques, in addition to the people’s high sense of environmental protection. Therefore, the classification of upstream waste is very good. On the other hand, waste recycling technologies have been developed and popularized in a number of countries such as the United States, Japan, and South Korea … The environmental industry has been established to address environmental pollution. recycling waste and bringing high economic efficiency.
Economic growth and increased waste always go hand in hand. As the demand for life is improved, it requires society to provide more products for people. Therefore, the development of production, raw materials and natural resources used by mankind constitute useful products but will eventually create waste.
According to statistics, in the US from 1970 to 1998, the amount of solid waste buried and destroyed increased by 37%, the amount of waste per capita increased by 14%. Americans generate 156 million tons of municipal solid waste each year. In Korea, total solid waste is about 298 million tons / year, of which urban waste is about 58 million tons / year, industrial waste is about 100 million tons / year.
If we say the trend of the world’s solid waste treatment technology in the future is far more asserted that landfill technology will be “without a foothold”, recycling technologies will be applied according to type of waste. Especially, pyrolysis technology will be widely used, because it allows for very thorough treatment and reduces the most volume compared to other methods.
However, in the coming time in developed countries where industrial environment industry has developed, recycling technologies have been applied effectively, the method of hygienic landfill accounts for a very low rate, about 10-15%. In these countries, the food processing technology is developed, the main food is processed, so the amount of food waste will decrease. On the other hand, in these countries the proportion of agricultural development is very low. Therefore, the technology of producing compost accounts for a very low proportion, only accounting for about 1-5% of the waste.
Municipal solid wastes, agricultural solid wastes, and industrial wastes tend to be recycled or treated by pyrolysis methods which reuse thermal energy in different forms.
Trends in management and treatment of solid and hazardous waste in countries around the world are as follows:
Focus on thoroughly solving industrial solid waste, for the following reasons:
– Industrial waste causes serious environmental pollution;
– Industry with scientific and technological capabilities;
–Industry capable of manpower;
–The industry has a department in charge of the environment.
The world goes to no landfills.
Application of advanced technologies, waste recycling.
5.2. Trends in solid waste treatment technology in Vietnam
In Vietnam in the coming years, the trend of solid waste treatment is different between large cities and provinces.
– In big cities, the trend of treatment by pyrolysis is to recover energy to reduce treatment costs.
– In the provinces, there are two trends of solid waste disposal: hygienic burial and microbiological production.
Within a decade from 2010 to 2020, the trend of urban solid waste treatment in big cities such as Hanoi, Ho Chi Minh City, Hai Phong, Da Nang, Nha Trang … mainly uses thermal methods. stool and recycling methods.
For example, a series of solid waste treatment projects from 2010 to present in Hanoi city have been proposed:
The project is handled by Plasma PGM combustion method 300 tons / day of Thanh Quang Construction and Trading Joint Stock Company (under construction).
Hanoi urban solid waste project at Nam Son waste treatment complex by recycling method of AIC World Progressive Joint Stock Company (under construction).
Proposal of Xuan Mai urban waste treatment project by recycling technology into diesel …
The main reasons big cities need to eliminate waste burial methods are the lack of space and environmental pollution due to leachate and landfill emissions.
Treatment by pyrolysis method: conventional incineration, incineration takes advantage of heat, plasma combustion, carbonization method … although the investment and operating costs are high, it will be an alternative measure. alternative to burial methods. Anaerobic composting and decomposition methods can only handle organic components.
Factors affecting the demand for pyrolysis treatment:
– The need to recover valuable products and energy from urban solid waste.
– Traditional incineration method has a negative impact.
– There are restrictions on burying untreated waste.
Currently, the world has been applying modern technologies in the treatment of solid waste such as incineration of electricity generation, plasma combustion at high temperatures, recycling of waste plastic, waste rubber into fuel oil … In Vietnam some advanced technology has also been imported and started to apply. However, in order to decode the technology and move forward to mastering the technology, the relevant authorities and environmental scientists and scientists should focus on the following issues:
For urban solid waste:
– Research incineration technology combined with making use of thermal power generation to use and operate waste treatment systems to reduce treatment costs.
– Research on carbonization technology to create fuel products and materials to treat environmental pollution.
– Studying Plasma incineration technology to form a synthetic gas used to operate waste treatment systems.
– Research pyrolysis technology to create fuel to use and operate the waste system.
– Research on the production of catalysts effectively used for the process of pyrolysis to form fuels.
– Research on recycling technology of rubber, plastic, metal and paper components …