The treatment of leachate from urban landfills has always been a very difficult issue in landfill design, operation and management. Leachate is the product of gravity flow of liquid in a landfill, mainly from precipitation and the water contained in the waste itself. Since there are many factors that may affect the properties of leachate during the flow of liquid, including physical factors, chemical factors, and biological factors, the properties of leachate vary within a considerable range. Generally speaking, its pH value is between 4 and 9, COD is in the range of 2000 to 62000mg/L, BOD5 is from 60 to 45000mg/L, and the concentration of heavy metals is basically the same as that in municipal sewage. Urban landfill leachate is a high-concentration organic wastewater with complex composition. If it is directly discharged into the environment without treatment, it will cause serious environmental pollution. For the purpose of protecting the environment, leachate treatment is essential. ?
1 Current status of leachate treatment technology The treatment methods of landfill leachate include physical and chemical methods and biological methods. Physical and chemical methods mainly include activated carbon adsorption, chemical precipitation, density separation, chemical oxidation, chemical reduction, ion exchange, membrane dialysis, gas lift and wet oxidation methods, etc. When the COD is 2000~4000?mg/L, the physical and chemical methods The COD removal rate of this method can reach 50% to 87%. Compared with biological treatment, physical and chemical treatment is not affected by changes in water quality and quantity, and the effluent quality is relatively stable. It has better treatment effects, especially for landfill leachate with a low BOD5/COD ratio (0.07-0.20) that is difficult to biologically treat. However, the cost of physical and chemical treatment is high and it is not suitable for the treatment of large-volume landfill leachate. Therefore, currently, biological methods are mainly used for landfill leachate. Biological methods are divided into aerobic biological treatment, anaerobic biological treatment and a combination of the two. Aerobic treatment includes activated sludge method, aerated oxidation tank, aerobic stabilization pond, biological turntable and trickling filter, etc. Anaerobic treatment includes upflow sludge beds, anaerobic immobilized bioreactors, mixing reactors and anaerobic stabilization ponds. ?
2 Introduction to leachate treatment Landfill leachate has characteristics different from those of general urban sewage: high concentrations of BOD5 and COD, high metal content, large changes in water quality and quantity, high ammonia nitrogen content, and microbial nutrients. Disproportionality, etc. Among the leachate treatment methods, combining leachate with urban sewage is the simplest method. However, landfills are usually far away from cities and towns, so there are specific difficulties in the combined treatment of leachate and urban sewage, and they often have to be treated separately. Commonly used processing methods are as follows. ?
2.1 Aerobic treatment uses activated sludge method, oxidation ditch, aerobic stabilization pond, biological turntable and other aerobic methods to treat leachate. There is successful experience. Aerobic treatment can effectively reduce BOD5, COD and ammonia nitrogen can also remove other pollutants such as iron, manganese and other metals. Among the aerobic methods, delayed aeration is the most commonly used method, as well as aeration stabilization ponds and biological turntables (mainly used to remove nitrogen). They will be introduced separately below. ?
2.1.1 Activated sludge method?
2.1.1.1 Traditional activated sludge method
?Leachate can be treated by biological methods, chemical flocculation, and carbon adsorption , membrane filtration, lipid adsorption, gas stripping and other methods for separate or combined treatment. Among them, the activated sludge method is the most widely used because of its low cost and high efficiency. The operating results of several activated sludge process sewage treatment plants in the United States and Germany show that by increasing the sludge concentration to reduce the organic load of the sludge, the activated sludge process can achieve satisfactory landfill leachate treatment effects. For example, the Fall Township sewage treatment plant in Pennsylvania, USA, has a CODCr of ?6000-21000?mg/L in the wastewater leachate, a BOD5 of ?3000-13000?mg/L, and ammonia nitrogen of 200-2000?mg/L. The sludge concentration (MLVSS) of the aeration tank is ?6000~12000mg/L, which is 3~6 times the general sludge concentration. When the volumetric organic load is 1.87kgBOD5/(m3·d), F/M is 0.15~0.31kgBOD5/(kgMLSS·d), and the BOD5 removal rate is 97%; when the volumetric organic load is 0.3kgBOD5/(m3·d) ), F/M is 0.03~0.05kg BOD5/(kgMLSS·d), and the BOD5 removal rate is 92%.
Data from the plant shows that as long as the concentration of the activated sludge method is appropriately increased so that F/M is between 0.03 and 0.31kgBOD5/(kgMLSS·d) (it should not be any higher), the activated sludge method can effectively treat landfill seepage. filtrate.
?Many scholars have also found that activated sludge can remove 99% of BOD5 in leachate, and more than 80% of organic carbon can be removed by activated sludge. Even if the organic carbon in the incoming water is as high as 1000mg/L, the pollution The mud biophase can also quickly adapt and degrade. The activated sludge system operating under low load can remove 80% to 90% of COD in the leachate, and the effluent BOD5 is <20mg/L. For leachates with COD 4000-13000mg/L, BOD 51600-11000mg/L, and NH3-N 87-590mg/L, the COD removal rate of the mixed aerobic activated sludge method can be stabilized at more than 90%. Numerous landfill leachate treatment systems in actual operation have shown that the activated sludge method has better treatment effects than other methods such as chemical oxidation. ?
2.1.1.2 Hypoxic?Aerobic activated sludge process
?Hypoxic?Aerobic activated sludge process and SBR process and other improved activated sludge processes, because of their It has the characteristics of being able to maintain a high operating load, taking a short time, and is more effective than the conventional activated sludge method. Xu Dimin of Tongji University and others used the hypoxic-aerobic activated sludge method to treat landfill leachate. The test proved that: under controlled operating conditions, the landfill leachate was treated by the hypoxic-aerobic activated sludge method, and the effect was excellence. The average CODCr, BOD5, and SS of the final effluent were reduced from the original 6466 mg/L, 3502 mg/L, and 239.6 mg/L to CODCr＜300 mg/L and BOD5＜50 mg/L (the average was 13.3 mg/L). L) and SS<100mg/L (average 27.8mg/L). The total removal rates were CODCr 96.4%, BOD5 99.6%, and SS 83.4%.
?If the treated effluent is further chemically coagulated with basic aluminum chloride, the CODCr of the effluent can be reduced to less than 100mg/L.
?The two-stage method is also better than the general biological method for treating nitrogen and phosphorus in leachate. The average removal rate of phosphorus is 90.5%; the average removal rate of nitrogen is 67.5%. In addition, the operation of this method makes up for the shortcomings of the anaerobic and aerobic two-stage biological treatment method. The first stage forms more NH3-N, making the second stage difficult to carry out and the two aerobic treatments last too long. ?
2.1.1.3 Physicochemical activated sludge composite treatment system
?Due to the high proportion of polymer compounds that are difficult to degrade in the leachate water, the inhibitory effect of heavy metals present, Therefore, a composite system that combines biological methods with physical and chemical methods is commonly used to treat landfill leachate. For leachate with BOD5?1500m g/L, Cl-800mg/L, hardness (calculated as CaCO3) 800mg/L, total iron 600mg/L, organic nitrogen 100mg/L, TSS 300mg/L, SO2-4300mg/L, Some scholars have used this method for treatment and found that the effect is very good, with the removal rates of BOD5, COD, NH3-N, and Fe reaching 99%, 95%, 90%, and 99.2% respectively. After the incoming water in this system passes through the regulating tank, it can avoid the instantaneous high concentration of toxic substances that inhibits activated sludge organisms; adding lime to the clarifier can remove heavy metals and some organic matter; the gas stripping tank (aeration) gas, adding NaOH when the temperature is low) can remove 50% of the NH3-N in the incoming water, thereby keeping the concentration of NH3 below the inhibitory level; because the phosphorus in the wastewater is precipitated by the added lime, and the pH value is too high, it is necessary to add Phosphorus and acidic substances; the activated sludge system can be used in series or parallel. During operation, the conventional method or the delayed aeration method can be selected by adjusting the return sludge ratio, which has greater operational flexibility. ?
2.1.2 Aeration stabilization pond
?Compared with the activated sludge method, the aeration stabilization pond has a large volume and low organic load. Although the degradation progress is slower, due to its The project is simple and is the most cost-effective aerobic biological treatment method for landfill leachate in areas where land is not expensive.
Small-scale, pilot-scale and production-scale studies in the United States, Canada, the United Kingdom, Australia and Germany have shown that the use of aeration stabilization ponds can achieve better landfill leachate treatment effects.
?For example, the UK invested 60,000 pounds in Bryn Posteg Landfill to build a 1000m3 aeration oxidation pond, equipped with 2 surface aeration devices, with a minimum hydraulic retention time of 10d, and the oxidation pond effluent flows through 3km after sedimentation Long pipe into city sewer. This system started operation in 1983. The maximum CODCr of leachate is 24000mg/L, the maximum BOD5 is ?10000mg/L, F/M=0.05~0.3kgCOD/(kgMLSS·d), and the water volume changes range is 0~150m3/d. The average BOD5 of the effluent is 24mg/L, but occasionally it exceeds 50mg/L. The COD removal rate reaches 97%, but P needs to be added during the operation. Taking into account the daily operating costs, investment repayment and interest, and leachate Compared with discharging directly to the municipal pipe network, it can save 750 pounds per year.
?The British Water Research Center also conducted a pilot test of an aeration stabilization pond with CODCr > 15000mg/L leachate in the New Park Landfill in the southeast. When the load was 0.28~0.32kgCOD /(kgMLSS·d) or 0.04~0.64kgCOD/(kgMLSS·d). When the mud age is 10 days, the COD and BOD5 removal rates are over 98% and 91% respectively. Phosphoric acid also needs to be added during operation. ?
2.1.3 Biofilm method
?Compared with the activated sludge method, the biofilm method has the advantages of resisting water volume and water quality impact loads, and the biofilm can grow for generations Longer microorganisms, such as nitrifying bacteria. C. Peddie and J. Atwater from the University of British Columbia in Canada used a biological turntable with a diameter of 0.9m to treat weak leachate with CODCr
2.2 Anaerobic biological treatment
?The purposeful application of anaerobic biological treatment has a history of nearly a hundred years. However, it was not until the past 20 years that, with the development of microbiology, biochemistry and other disciplines and the accumulation of engineering practice, new anaerobic treatment processes have been continuously developed, which have overcome the characteristics of the traditional process such as long hydraulic retention time and low organic load, making it Great progress has been made in theory and practice, and good results have been achieved in treating high-concentration (BOD5 ≥2000?mg/L) organic wastewater.
Anaerobic biological treatment has many advantages. The most important ones are low energy consumption and simple operation, so the investment and operating costs are low. Moreover, because the amount of residual sludge produced is small, the required nutrients are also low. For example, its BOD5/P only needs to be 4000:1. Although the P content in the leachate is usually less than 1 mg/L, it can still meet the P requirements of microorganisms. Using ordinary anaerobic nitrification, at 35°C, a load of 1kgCOD/(m3·d), and a residence time of 10d, the COD removal rate in the leachate can reach 90%.
?In recent years, the anaerobic biological treatment methods developed include: anaerobic biological filters, anaerobic contact tanks, upflow anaerobic sludge bed reactors and staged anaerobic nitrification. ?
2.2.1 Anaerobic biological filter
?Anaerobic filter is suitable for treating dissolved organic matter. The average COD of leachate from Halifax Highway 101 landfill in Canada is 12850mg/L. BOD5/COD is 0.7 and pH is 5.6. The leachate is first adjusted to pH=7.8 with lime water, and then settled for 1 hour before entering the anaerobic filter (this process also plays a role in removing heavy metals such as Zn). When the load is 4kgCOD/(m3·d), the COD removal rate It can reach more than 92%; when the load increases, the removal rate drops sharply.
J.G. Henry et al. from the University of Toronto in Canada also successfully used anaerobic filters to treat 1.5-year-old and 8-year-old landfill leachates respectively at room temperature. Their CODs were 14000mg/ L and 4000?mg/L, BOD5/COD are 0.7 and 0.5 respectively. When the load is 1.26~1.45kgCOD/(m3·d) and the hydraulic retention time is 24~96h, the COD removal rate can reach more than 90%. When the load increases, the removal rate also drops sharply. It can be seen that although the load of anaerobic filter when treating high-concentration organic sewage can reach 5-20kgCOD/(m3·d), the load of leachate must be kept at a low level to obtain ideal treatment results. ?
2.2.2 Upflow anaerobic sludge bed
?The British Water Research Center reported the use of an upflow anaerobic sludge bed (UASB) to treat COD＞ For 10000mg/L leachate, when the load is 3.6~19.7kgCOD/(m3·d), the average mud age is 1.0~4.3d, and the temperature is 30℃, the COD and BOD5 removal rates are 82% and 85% respectively. They The load is much larger than that of the anaerobic filter.
?During anaerobic decomposition, organic nitrogen is converted into ammonia nitrogen, and there is NH4＋?NH3＋H?＋ reaction. If the pH is >7, NH3 in the equilibrium is dominant and can be removed by stripping. However, during anaerobic decomposition, the pH is approximately equal to 7, so the effluent may contain more NH4+, which will consume dissolved oxygen in the receiving water body. ?
2.3 Combination of anaerobic and aerobic methods
?Although practice has proven the effectiveness of anaerobic biological methods in the treatment of high-concentration organic wastewater, anaerobic methods alone are used for treatment Leachate is also rare. The use of anaerobic or aerobic treatment processes for high-concentration landfill leachate is both economical and reasonable, and has high treatment efficiency. The removal rates of COD and BOD reached 86.8% and 97.2% respectively. ?
2.3.1 Anaerobic?Aerobic biological oxidation process (anaerobic nitrification and biological oxidation pond)
?The Department of Biology of Southwest Normal University has a pH of 8.0 to 8.6 and a COD of The leachate is 16124 mg/L, BOD5 is 214-406 mg/L, and NH3-N is 475 mg/L. It is treated by anaerobic or aerobic biochemical methods. The effluent pH is 7.1-7.9 and the COD is 170.33-314.8 mg/L. BOD5 is 91.4mg/L and NH3-N is 29.1mg/L. ?
2.3.2 Anaerobic, oxidation ditch, and facultative pond technology
?The following description and analysis will be made based on the Guangzhou Likeng landfill. The Likeng landfill sewage treatment plant is designed with a flow rate of 300m3/d. The incoming water BOD5 is 2500mg/L, CODCr is 4000mg/L, NH3-N is 1000mg/L, SS is 600mg/L, and the color is ?1000 times; the effluent BOD5 is 30mg/L, CODCr is 80mg/L, NH3-N is 10mg/L, SS is 70mg/L, and the chroma is 40 times. The selected process flow is: anaerobic? oxidation ditch? facultative pond? flocculation sedimentation. When the incoming water quality is good and the facultative pond effluent meets the standards, the facultative pond water can be discharged directly; when the incoming water quality is poor and the facultative pond effluent does not meet the discharge standards, the coagulation sedimentation system is activated. , and then discharge the sedimentation tank supernatant.
?Judging from the current operation of this process, when the COD of the incoming water is high, the quality of the effluent water is good; once the COD decreases, especially when the temperature is low and there is little rain in winter, the COD decreases to a level that is not conducive to biochemical treatment. , the water quality components of the effluent were too high to meet the standards, and the effluent was brown. Although the flocculation and sedimentation system was activated, the effect was still not ideal. It can be seen that the color of the leachate and the effective removal of NH3-N will have a beneficial impact on the biochemical treatment. ?
2.3.3 Anaerobic? Air flotation? Aerobic process
?This process is used to treat the leachate of Daejeonshan garbage sanitary landfill. Based on the leachate detection data and simulation tests of similar landfill sites by the Guangzhou Environmental Hygiene Institute, and combined with the actual conditions of the site, the leachate sewage treatment design parameters were determined.
The inlet water quality CODCr is 8000mg/L, BOD5 is 5000mg/L, SS is 700mg/L, and the pH value is 7.5; the outlet water quality is CODCr 100mg/L, BOD5 is 60mg/L, SS is 500mg/L, and the pH value is 6.5. ~7.5. ?Based on the characteristics of the site being far away from the urban area, in order to facilitate management and save energy consumption, anaerobic and aerobic combined treatment processes were selected after comparison. The anaerobic section is an upflow anaerobic sludge bed reactor, and the aerobic section is a biological contact oxidation method, adding chemical coagulation sedimentation and biological oxidation ponds, and is discharged after purification treatment reaches the standard. The remaining sludge is concentrated and sent back to the landfill for disposal.
?Considering that the leachate water quality varies greatly, an air flotation process is added after the anaerobic section to increase the treatment capacity to cope with the high quality of the incoming water. Currently, Shenzhen Xiaping Landfill is designed to use anaerobic, flotation, and aerobic processes to treat leachate. ?
2.3.4 UASB? Oxidation ditch? Stabilization pond
?Fuzhou City built the country's largest modern comprehensive municipal waste treatment site in 1995 - Fuzhou Hongmiaoling Garbage Sanitary landfill. The water volume of landfill leachate treated is 1000m3/d; the landfill leachate water quality (inlet) is CODCr 8000mg/L and BOD5 5500mg/L; the treatment water quality requirements (outlet) are CODCr removal rate of 95% and BOD5 removal rate of 97%.
?The design adopts an upflow anaerobic sludge bed, an Ober oxidation ditch, and a stabilizing pond process. The leachate from the landfill is concentrated in the storage tank. Depending on the higher terrain of the site, it flows to the collection tank and grid. After being measured by the Bar-type metering tank, it flows to the distribution tank by potential energy, and then relies on hydrostatic head pressure to reach the top. Inward flow anaerobic sludge bed. The sewage after anaerobic treatment flows to a sedimentation tank for solid-liquid separation. The supernatant flows to the Ober oxidation ditch. The settled sludge is discharged to the sludge tank by gravity. The sludge is regularly sent to the landfill or landfill by tanker truck. Compost utilization.
?The sewage undergoes aerobic and biochemical treatment in the Ober oxidation ditch. The Ober oxidation ditch adopts the three-groove A/O process, which has advanced sewage denitrification treatment effect. The outstanding advantage of this process is that it can both nitrify ammonia nitrogen and denitrify nitrate using BOD as a carbon source in the first ditch. The total nitrogen removal rate can reach 80%. Since BOD in sewage is used as a carbon source , resulting in the removal of BOD5 in the sewage, reducing the oxygen demand in the sewage. In order to improve the denitrification effect of the oxidation ditch, the effluent from the third ditch is pumped to the first ditch with a submersible pump for internal reflux, and denitrification is carried out in the first ditch.
?The sewage treated by the oxidation ditch flows into the secondary sedimentation tank for solid-liquid separation, and the clarified water flows to the stabilizing pond for biological treatment. The remaining sludge in the secondary sedimentation tank is discharged to the concentration tank by gravity. The supernatant in the concentration tank returns to the oxidation ditch for treatment, and the concentrated sludge is pumped to a tanker with a submersible pump and transported to a landfill for burial or composting. ?
2.4 Land treatment
?Land treatment method, also known as soil irrigation method, is the earliest sewage treatment method adopted by mankind, but the application of land treatment system is mostly seen in urban sewage treatment. For leachate treatment, the leachate is collected and returned to the landfill through sprinkler irrigation. Recirculating landfill leachate increases biological activity by increasing the moisture content of the waste, accelerating methane production and waste decomposition. Secondly, due to the evaporation in sprinkler irrigation, the volume of leachate is reduced, which is beneficial to the operation of the wastewater treatment system and can save energy costs. Part of the Seamer Carr landfill in Northern England uses leachate recirculation. After 20 months, the COD value of the leachate in the recirculation area dropped significantly, and the metal concentration dropped significantly, while the NH3-N and Cl- concentrations Changes are minor. This shows that the decrease in metal concentration is not only caused by dilution, but also may be caused by the adsorption of inorganic components in the garbage.
?Due to the many advantages of recycling leachate, the top of the landfill should not be completely closed when designing the landfill, but regularly arranged channels should be set up to avoid contamination of the surrounding water sources. Low-concentration leachate cannot be discharged directly because the NH3-N and Cl- concentrations are still high, the temperature is low in seasons, there is less evaporation, and the biological activity is weak. The effect of recycling leachate needs further research.
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2.5 Nitrification and Denitrification
?"Old" landfills are often in the methane fermentation stage, and the ammonia nitrogen content in their leachates is relatively high, usually 100-1000mg/L . There are two main methods for removing ammonia nitrogen: one is nitrification and denitrification; the other is to increase the pH value to above 9 and then blow it off with air. Robinson and Maris aerated the 20-year-old landfill leachate at a temperature of 10°C and a mud age of 60 days (actually this is similar to the operating conditions of the oxidation pond), and it can be completely nitrified. Other aerobic methods using biological turntables have also been successful, so it is generally believed that nitrification of leachate is not a problem. ?
2.6 Rochem's reverse osmosis treatment plant in the UK
?Rochem's patented disc tube reverse osmosis system is used to treat primary leachate at the UK landfill leachate treatment plant. The treatment technology is Rochem's separation membrane system designed and manufactured at Winterton Landfill in South Humberside.
?The heart of this system is Rochem's patented disc tube. The cylinder, which consists of plates, octagonal steel and a wear-resistant membrane cushion inside a circular tube, can handle leachate that quickly clogs ordinary reverse osmosis membrane systems. The leachate enters Rochem's treatment system under membrane pressure for aeration and pH correction. When the leachate containing pollutants flows through the inner membrane surface of the cylinder, the pollutants in the leachate are separated due to reverse osmosis and discharged through the membrane. The entire system cleaning operation is automated. When the system needs to be chemically cleaned, the control indicator will display information. At the same time, the automatic cleaning system will use programmed chemical agents to clean the system internally, so that It returns to its original functionality. Because the leachate forms turbulence on the surface of the membrane when it is closed, reducing oxidation and producing odor, internal cleaning must be carried out at a certain time, but the interval between such cleanings is long. Rochem's separation membrane system can remove heavy metals and suspended solids. substances, ammonia nitrogen and harmful refractory organic matter, and the treated water meets strict discharge standards.
?The Ihlenbery landfill in Germany is now equipped with a Rochem's treatment system that has a treatment capacity of 50m3/h and a water recovery rate of 90%. ?
Introduction to urban garbage leachate treatment process From: Free Paper Network
3 Analysis and comparison of treatment processes Compared with aerobic methods, anaerobic biological treatment has the following advantages. (1) The aerobic method consumes energy (air compressor, rotating brush, etc.), but the anaerobic treatment can generate energy (generate methane gas). The higher the COD concentration, the more energy the aerobic method consumes; the greater the production capacity of the anaerobic method, the more obvious the difference between the two. (2) The proportion of organic matter converted into sludge during anaerobic treatment (0.1kgMLSS/kgCODCr) is much smaller than the proportion of aerobic treatment (0.5kgMLSS/kgCODCr), so the cost of sludge treatment and disposal is greatly reduced. (3) The growth of sludge during anaerobic treatment is small, and the requirements for inorganic nutrients are much lower than those in aerobic treatment, so it is suitable for treating landfill leachate with relatively low phosphorus content. (4) According to reports, many halogen organic compounds that are difficult to handle under aerobic conditions can be biodegraded under anaerobic conditions. (5) The organic load of anaerobic treatment is high and the area occupied is relatively small. However, the COD concentration and ammonia nitrogen concentration in the anaerobic treatment effluent are still relatively high, and the dissolved oxygen is very low, so it is not suitable to be discharged directly into rivers or lakes. Subsequent aerobic treatment is generally required. In addition, most landfill leachates in the world are acidic (the pH value is generally between 5.5 and 7.0). When the pH is below 7, methanogenic bacteria will be inhibited or even die, which is not conducive to anaerobic treatment, while aerobic treatment does not have such strict pH requirements. Furthermore, the optimal temperature for anaerobic treatment is 35°C. Below this temperature, the treatment efficiency decreases rapidly. In comparison, aerobic treatment does not have high temperature requirements. Even if the water temperature is not controlled in winter, better effluent quality can still be achieved. In view of the above reasons, it is currently recommended to use anaerobic methods (followed by aerobic treatment) to treat high-concentration landfill leachate with a COD concentration above 50 000 mg/L, and to treat high-concentration landfill leachate with a COD concentration below 5 000 mg/L. It is recommended to use aerobic biological treatment method for landfill leachate.
For landfill leachate with COD between ?5 000? and ?50 000?mg/L, either aerobic or anaerobic methods can be used. Other factors are mainly considered when selecting the process. ?
4 Conclusions and Suggestions Through the analysis and comparison of the above several treatment methods and treatment processes, the following conclusions can be drawn, and suggestions and opinions on water quality, water quantity, etc. are put forward: (1) Landfill leachate has composition It is complex, with huge changes in water quality and quantity, high concentrations of organic matter and ammonia nitrogen, and imbalanced proportions of microbial nutrients. Therefore, when selecting a biological treatment process for landfill leachate, it is necessary to measure the various components of the landfill leachate in detail and analyze their characteristics in order to take appropriate measures. countermeasures. Reliable and optimized process parameters should also be obtained through small and pilot tests to obtain ideal treatment effects. (2) Multiple methods are feasible for leachate treatment. Building biological ponds where conditions permit and using aquatic plant systems to treat leachate not only save investment, but also have low operating costs. Land treatment has also received people's attention, but it is still rarely used in leachate treatment. Biofilm method and activated sludge method have mature operation and management experience. In recent years, a combination of anaerobic and aerobic processes has been used to biologically treat leachate. However, the investment in building a dedicated leachate treatment plant is high, and the operation and management costs are high. With the closure of the landfill, the water treatment facilities will eventually be scrapped, so they should be selected with caution. (3) There are not many landfills in my country that can truly meet sanitary landfill standards. Many landfills are unable to build leachate collection systems that meet environmental protection requirements as designed due to investment constraints. Therefore, it is advisable to develop leachate treatment technology that saves investment and achieves good results. The landfill leachate is recirculated into the landfill, and the leachate is degraded by land adsorption, soil biodegradation and the anaerobic filter bed of the landfill layer. It has the characteristics of low investment, good effect, and no investment in special treatment facilities. . Moreover, the recirculation of leachate can keep the garbage moist and accelerate the stability of the landfill. The recharge method is currently rarely used, and in-depth research can be conducted to clarify the usage conditions, treatment efficiency and engineering design parameters of the recharge treatment. (4) Treating leachate from landfills is one aspect of the problem. On the other hand, reducing the amount of leachate produced should be considered. It is appropriate to develop landfill technologies that can reduce leachate production, such as aerobic landfill or quasi-aerobic landfill. (5) The treatment of landfill leachate is still in the research and exploration stage in my country. In order to build a standardized urban garbage sanitary landfill, more in-depth research should be conducted on the treatment of landfill leachate.