An inventory of mainstream landfill leachate treatment processes

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This post was last edited by Qingfeng Xuchi on 2022-1-11 11:10. In recent years, with the increase in the number of cities and population in our country, people's living standards have continued to improve, and urban waste has also increased dramatically. In this situation, many towns have built new landfills. At the same time, the problem of landfill leachate treatment has also gradually surfaced. along with * * More attention is paid to people's livelihood, environmental protection standards are increasingly improved, and local environmental protection emission requirements are becoming more stringent. The difficulty of treating landfill leachate has also become * * One of the technical difficulties that relevant departments focus on. Figure 1 "GB 16889-2008" because the characteristics of landfill leachate are different from those of general urban sewage. Secondary pollutants produced by compaction and fermentation of garbage and other wastes during the process of stacking, landfilling and incineration are organic or inorganic harmful components. Liquid form usually has complex composition, high concentration of ammonia nitrogen (NH4-N) and organic pollutants (CODCR), poor biodegradability, high total dissolved solids content (TDS), high content of heavy metal substances, and is accompanied by severe toxicity, stench and other main characteristics. Among the leachate treatment methods, combining leachate with urban sewage is the simplest method. Figure 2 "GB 16889-2008》Emission limit landfills can be divided into different grades according to the length of landfilling years. Landfills with less than or equal to 5 years of landfill can be defined as early stage landfills, landfills with 5-10 years of landfill can be defined as mature landfills, and landfills with more than 10 years of landfill can be defined as aged landfills. In landfills, the water quality of landfill leachate also changes greatly as the age of the landfill increases. The main influencing factors are the age and design structure of the landfill. The material composition and concentration of landfill leachate fluctuate greatly. As the age of the landfill increases, the difficulty of its treatment also increases. Most domestic landfills are usually far away from cities and towns, so there are specific difficulties in the combined treatment of leachate and urban sewage. Therefore, most landfills have independent leachate treatment stations to self-process the leachate. The treatment processes are also different. The following will introduce you to the common treatment processes of landfill leachate and comments on their advantages and disadvantages. 1. Biological treatment + membrane treatment process 1. Treatment process: Pretreatment—microbial treatment—membrane adsorption filtration. 2. Adopt craftsmanship: Medium temperature anaerobic system+MBR+RO. 3. Process explanation: The landfill leachate flows into the medium-temperature anaerobic tank through the regulating tank. After being degraded by macromolecular organic pollutants, it enters the MBR reactor in the anoxic section. It is mixed with the return water and enters the MBR in the aerobic section for aeration to remove TN in the leachate. The effluent from the aerobic tank enters the MBR separator, and the separated sludge concentrate is returned to the MBR anoxic section. The MBR effluent enters the reverse osmosis system, and the leachate is discharged up to standard after reverse osmosis treatment. Advantages of medium temperature anaerobic+MBR+RO treatment process: The process principle is biochemical reaction and physical treatment process. Since there are many influencing factors during the operation of the biochemical system, close coordination and cooperation between various units are required. The process has a high degree of self-control and low technical risks, but it is difficult to treat "aging" leachate. shortcoming: The disadvantages of this process are that the water yield is low, which increases the difficulty of recirculation; the biological treatment effect is unstable, and biological strains need to be cultivated and domesticated, which increases the operating cost; the biochemical effect on "aging" leachate is extremely poor; the operation cannot be shut down for a long time and requires continuous operation. Recommendation index: 3 stars 2. Full membrane adsorption filtration treatment process 1. Treatment process: Pretreatment—two-stage reverse osmosis membrane filtration. 2. Adopt craftsmanship: Two-stage DTRO reverse osmosis treatment process. 3. Process explanation: The raw leachate solution from the landfill enters the high-pressure pump through the regulating tank, and then enters the first-level DTRO reverse osmosis membrane for filtration through the circulating high-pressure pump. After the water is discharged, it enters the second-level DTRO reverse osmosis system. After the two-stage reverse osmosis filtration, the effluent reaches the standard and is discharged. It is circulated into the system for treatment. The first-level concentrated liquid is returned to the landfill area for centralized treatment, and the second-level concentrated liquid is returned to the main water inlet. The total water production rate of the system is about 60%. Advantages of two-stage DTRO treatment process diagram: This process is easy to operate, can operate intermittently, has a high degree of automation, and is easy to maintain and manage; it has many disadvantages in terms of membrane product types.: This process is sensitive to the quality of leachate raw water, and the water yield is easily affected by factors such as SS, conductivity, and temperature; in the two-stage reverse osmosis treatment process, the lack of pretreatment in the front stage can easily lead to blockage of the reverse osmosis membrane, high replacement frequency, and increased treatment costs; the water yield is low (55%-70% under normal conditions), making reinjection difficult and increasing operating costs. Recommendation index: 3 stars 3, low consumption evaporation + Kohisi ion exchange treatment process 1. Treatment process: Pre-filtration - vapor compression separation of water - absorption of gaseous ammonia. 2. Adopt craftsmanship: MVC evaporation + Kehaisi ion exchange. 3. Process explanation: The landfill leachate is backflushed and filtered online through the regulating tank filter to remove SS and fibers in the leachate to improve the removal efficiency. It then uses the MVC compression evaporation principle to separate the pollutants in the leachate from water to achieve water purification. Ammonia in distilled water is removed through Kohis special resin to achieve comprehensive discharge of water quality standards. During the MVC evaporation process, volatile gas ammonia is discharged, and the DI system is used to absorb the remaining hydrochloric acid gas in the leachate. shortcoming: The evaporation process has high energy consumption such as electricity consumption and high maintenance costs; the equipment material requirements are high. advantage: The advantages of this process are that it is less affected by the original water quality of the leachate, has a high water yield, usually reaching 90%, can achieve intermittent operation, has a high degree of self-control, is simple to maintain, and has a small amount of concentrated liquid. Recommendation index: 4 stars follow * * With the introduction of more stringent environmental protection standards and the improvement of local environmental protection standards, there are not many landfills that can truly meet sanitary landfill standards. Many landfills are unable to build leachate collection systems that meet environmental protection requirements due to investment constraints as designed. Therefore, environmental protection technicians continue to try and improve the landfill leachate treatment process, whether it is pre-aeration and pre-coagulation sedimentation treatment of the original leachate solution in the regulating tank, catalytic wet oxidation treatment, membrane bioreactor treatment, membrane Fenton reactor treatment and degassing membrane deamination treatment, all in the pursuit of better leachate treatment technology. The treatment of landfill leachate is still in the research and exploration stage in our country. In order to build a standardized urban garbage sanitary landfill, it is necessary to * * Environmental protection departments and environmental protection technicians should conduct more in-depth research on the treatment of landfill leachate.