The EU's first management forum aimed at promoting the sustainable development of water resources in Asian cities opened on February 14 in Changde, Hunan. More than 20 officials and experts from European countries such as Germany and the Netherlands exchanged discussions with officials and scholars from Asian countries such as China, Vietnam, Bangladesh, and Indonesia on how to deal with urban water pollution and ensure the sustainable development of urban water resources.
Due to humans' excessive waste and continuous pollution of water resources, the deterioration and shortage of water resources are increasingly threatening the survival and development of human beings, especially the urban water crisis is becoming a worldwide problem.
Song Lanhe, deputy director of the National Water Resources Management Center of the Ministry of Construction of the People's Republic of China, revealed that two-thirds of the more than 600 cities in China are lacking water that can be used normally.
This three-day event was jointly organized by the Changde City Government of China, Hanover City, Germany, and Utrecht City Government, and the like. The EU wants to introduce Changde's urban water management concepts and technical methods to Changde as an example. Wu Lin, a project official of the EU Representative Office in China, said that China, which accounts for 21% of the world's population, only accounts for 6% of water resources. The growing water demand and water shortage are becoming contradictions in social development. The EU recognizes that Such problems exist in developing regions of the world, and solutions must rely on the efforts of the world.
The cities of Hanover and Utrecht introduced to the participants the water treatment in the city-the traditional treatment process encountered difficulties in operation and cost, and needed stable and economically viable technologies
From July 1, the leachate treatment of existing domestic waste landfills has begun to fully implement the Standard for Pollution Control of Domestic Waste Landfills (GB16889-2008). This is another water pollutant discharge standard that has been evaluated as "the most stringent" by the industry, and COD, ammonia nitrogen and other limits have been significantly tightened.
According to the requirements of this standard, all domestic landfill leachate must be discharged in full compliance with relevant indicators. However, judging from the current actual situation, there is almost no domestic landfill leachate treatment case that can meet the requirements for stable operation. Including the "bio + membrane" process that was previously promoted, it also encountered a series of technical and management difficulties and poor processing results. At present, both managers and companies intending to get a share of the landfill leachate treatment market are eager to find more applicable technologies.
Why is there no successful case?
The treatment of landfill leachate is difficult, the situation is complicated, the project design parameters are far from the actual operation, and the process of "bio + membrane" is difficult to run and the cost is high.
"Including the German technology, the original design parameters were very ideal, but long-term operation is completely different. There are great problems to achieve stable operation." Said Wang Shengdong, director of the Environmental Engineering Institute of Shanghai Environmental Sanitation Engineering Design Institute. They did The landfill leachate project has been for many years, but so far, no project has been done or seen that is stable and meets the economic requirements. "The COD index of landfill leachate is reduced to 1000mg / L after treatment, and the problem is not big, but it is very difficult to deal with the requirements of stable standards, including the membrane method."
Measuring a pollution control technology depends not only on its advanced nature, but also on whether it can meet the standards stably and the cost can be controlled in practice. In this regard, landfill leachate treatment poses severe challenges to each technology. Wang Jialian, secretary general of the Water Pollution Prevention Committee of the China Environmental Protection Industry Association, said in an interview with reporters that over a period of time, various processing technologies have been used in various places, but there are problems such as excessively complex processes and inability to achieve stable standards.
"From the perspective of actual operation, the membrane method is basically a dead end." Industry experts generally said that membrane technology has its advanced nature, but in the field of landfill leachate treatment, it currently has insurmountable obstacles in operation, management, and cost. Many domestic projects have adopted the "biochemical + membrane" process, including multiple processing steps such as anaerobic, aerobic, ultrafiltration, reverse osmosis, etc. The system is complex and affected by many factors, so that the coordinated operation of the entire system requires a higher techinque level. Once one of the processes is "paralyzed", the entire process will be severely affected or even shut down.
Another problem that deserves attention is that processes such as "biochemical + membrane" will still produce more than 30% concentrated liquid during operation, and the concentration of pollutants is very high, and its treatment is still a difficult problem. Professor Wang Kaijun from the Department of Environmental Science and Engineering of Tsinghua University said that if the recycling process is adopted, it is easy to cause salt to be accumulated in a timely manner, and the frequency of membrane replacement will rise rapidly, which will significantly increase costs.
Whether it is a complete biochemical method or the introduction of membrane technology, the system stability of the existing process also largely depends on the technical level and experience of management operators. The lack of high-level talents familiar with the operation of the above-mentioned treatment units is an important reason that causes most of the current landfill leachate treatment projects to fail to operate normally. "I have seen 50 to 60 projects in the country. Whether it is a double-film or laminated film process, the operation is not ideal. Either it is not stable, or it will be shut down for maintenance." Said Zhao Lijun, technical consultant of Tianjin Municipal Engineering Design Institute.
Operation is an important standard for inspection technology
New technology research and development must meet the principles of high efficiency and low consumption, reliable operation, relatively simple management, and strong adaptability.
Following the introduction of the "Standard for Pollution Control of Domestic Waste Landfill Sites", the Department of Science and Technology Standards of the Ministry of Environmental Protection issued related engineering technical specifications and began to organize the formulation of related technical policies. Both from the management department and the industry are trying to find new processing technologies and models. Zhu Xingxiang, vice chairman of China Environmental Protection Industry Association, said that landfill leachate treatment is a difficult problem, and we should encourage exploration of solutions from multiple angles.
"Governance technology must consider the cost, and the cost in the case of stable compliance is the key to determining whether a technology can be promoted and applied on a large scale." Xu Haiyun, secretary-general of the Urban Waste Disposal Professional Committee of the China Environmental Protection Industry Association, pointed out, especially with the waste treatment facilities. Expansion to county-level cities must take into account factors such as cost, operation, and management.
A landfill leachate treatment technology called "MVC evaporation + DI" is attracting industry attention. This technology applies the mature mechanical vapor compression technology (MVC) to the landfill leachate treatment field after innovation. At present, it has 8 successful projects and 6 projects under construction. Zhonghuan Water Construction Co., Ltd., Zhongshan Dibaolong Water Treatment Equipment Co., Ltd. and Dongguan Yunshui Yao Environmental Protection Technology Co., Ltd. have formed a strategic consortium in the research and development and promotion of related technologies, and each has its advantages in project promotion, research and development, and construction.
The next day, the China Environmental Protection Industry Association organized an expert council on this technology in Dongguan, Guangdong Province. Liu Hongliang, an academician of the Chinese Academy of Engineering, chaired the review, and a number of industry experts visited the site and listened to corporate reports.
After review, the expert group concluded that the landfill leachate was treated with "MVC evaporation + DI" technology from Huatankou Landfill, and the effluent water quality met the water quality standards in Table 2 of the "Standard for Pollution Control of Domestic Waste Landfill", and the treatment effect was significant. . Compared with traditional technology, this technology has the advantages of fewer process units, simple operation and management, small footprint, high water yield (less concentrated liquid), etc., and is less affected by landfill age and seasonal changes, and has a stronger Adaptability. Among them, the MVC evaporation and DI ion exchange processes are mature, fully recover energy, reduce energy consumption, and have excellent effects of removing ammonia nitrogen.
Participating experts said that this technology has been successfully applied in multiple landfill disposal projects, providing new ideas for the exploration of landfill leachate treatment technology in China. Judging from the current project operation situation, this technical route is indeed superior to the traditional process, but as a new technology, there are still some problems that need to be solved and improved.
Ming Wang Shengdong revealed that they are very interested in this technology. In the next step, they will cooperate with the enterprise to build a leachate treatment facility with a scale of about one to two hundred tons in Shanghai Laogang Waste Treatment Plant. Through actual operation, observe the cost and actual operation effect. "This technology is very viable, especially for the leachate disposal of small landfills, with simple management and immediate shutdown, but the premise is to reduce construction costs through equipment localization and optimization of processes."
Related Links
The "Standard for Pollution Control of Domestic Waste Landfill Sites" (GB16889-2008) was formulated by the Science and Technology Standards Department of the Ministry of Environmental Protection, and has been fully implemented since July 1, 2008.
The new standard improves the design, construction, acceptance and operation standards of the landfill leachate system. At the same time, the number of pollutant control projects in domestic waste landfills has been increased, and the concentration limits of pollutants such as COD and ammonia nitrogen have been significantly tightened. The standard “Table 2“ Concentration Limits for Water Pollutant Discharge in Existing and Newly Built Domestic Solid Waste Landfill Sites ”stipulates that the discharge concentration limit for conventional sewage treatment facilities’ discharge outlets is 100mg / L, ammonia nitrogen is 25mg / L, and total nitrogen is 40mg / L, total phosphorus was 3mg / L.
According to the requirements of environmental protection work, in areas where the intensity of land development has been high, the environmental carrying capacity has begun to weaken or the environmental capacity is small, the ecological environment is fragile, and prone to serious environmental pollution problems, and special protection measures are needed, domestic garbage should be strictly controlled For the pollutant discharge behavior of landfills, the existing and newly built domestic waste landfills in the above-mentioned areas shall implement the standard in Table 3 of the “Special Discharge Limits of Water Pollutants for Existing and Newly Built Domestic Waste Landfills”. Strict, the COD limit of the discharge outlet of conventional sewage treatment facilities is 60mg / L, ammonia nitrogen is 8mg / L, total nitrogen is 20mg / L, and total phosphorus is 1.5mg / L. Experience, Shanghai, China, and Dhaka, Bangladesh, introduced urban river management.
