Landfill leachate treatment method and system

Abstract

The invention belongs to the field of wastewater treatment, and particularly relates to a landfill leachate treatment method and system. According to the method, the water quality and the water quantity of the landfill leachate are homogenized through an adjusting tank, then the landfill leachate is sequentially subjected to AO biochemical treatment and MBR treatment, iron-carbon micro-electrolysis treatment, ultraviolet catalytic oxidation treatment, coagulating sedimentation treatment and biological aerated filter treatment to obtain clear water, and generated sludge is subjected to filter pressing to form a sludge cake for landfill. According to the method, an optimized advanced oxidation treatment process consisting of iron-carbon micro-electrolysis treatment, ultraviolet catalytic oxidation treatment and coagulating sedimentation treatment is effectively combined with biological aerated filter treatment, so that advanced treatment of the landfill leachate is realized, and the problems that in an existing landfill leachate treatment process, the dosage of an oxidizing agent is large, the utilization rate is low, and the treatment cost is high are effectively solved. And the occupied area of tail water biochemical treatment is large. The system is used for realizing landfill leachate treatment, is high in treatment efficiency and high in denitrification load, does not need to design a secondary sedimentation tank, and reduces the construction cost of the system.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment, and in particular relates to a method and system for treating garbage leachate. Background Art

[0002] Leachate is a complex organic wastewater produced in the process of urban sanitary landfill. It contains high concentrations of difficult-to-degrade organic matter, total nitrogen, inorganic salts and various suspended solids, which can pose serious hazards to human health and the ecological environment. Therefore, proper treatment of leachate is crucial.

[0003] Strict emission standards for leachate, coupled with the long treatment time and high investment and operating costs of leachate treatment technology, have made effective decontamination, efficient denitrification and treatment cost control of leachate an important topic in the industry and academia, and also a huge challenge facing the environmental protection field.

[0004] At present, there are two main types of treatment technologies for landfill leachate: one is the treatment process with membrane method as the core, such as the scheme disclosed in the existing patent with publication number CN 110357350 A, that is, after conventional biological treatment (AO biochemical + MBR treatment), the membrane method is continued to be used to deeply treat the landfill leachate. The representative processes are "pretreatment (uniform water quality and water volume) + biological treatment (AO biochemical + MBR treatment) + NF + RO", where AO refers to anaerobic-aerobic treatment process, MBR refers to membrane bioreactor, NF refers to nanofiltration, and RO refers to reverse osmosis. This treatment process not only makes the leachate meet the standards, but also produces membrane filtration concentrate that is more difficult to treat. The second is the treatment process currently adopted by our company with advanced oxidation as the core, which is to continue to use advanced oxidation technology to deeply treat the landfill leachate after conventional biological treatment. The process treatment steps are "pretreatment (uniform water quality and water volume) + biological treatment (AO biochemical + MBR treatment) + Fenton treatment + traditional biochemical treatment (cyclic activated sludge treatment or oxidation ditch treatment)", and the specific treatment process flow is as follows Figure 1 As shown, although this treatment process can achieve full-scale treatment of landfill leachate, it uses traditional Fenton treatment, with a large amount of oxidant added and low utilization rate. It also uses traditional biochemical treatment of tail water, with low treatment efficiency and the need to design a secondary sedimentation tank, which results in a large tail water biochemical footprint.

[0005] Therefore, there is a need in the art to design a new method and system for treating landfill leachate. Summary of the invention

[0006] One object of the present invention is to provide a method for treating landfill leachate, which, after AO biochemical + MBR treatment, uses an optimized advanced oxidation treatment and aerated biological filter treatment to effectively combine for deep treatment, effectively solving the problems of large oxidant dosage and low utilization rate in the existing landfill leachate treatment process, as well as large tailwater biochemical footprint. The method comprises the following steps:

[0007] S1, the landfill leachate is passed through a regulating tank to make the water quality and quantity uniform, and then subjected to AO biochemical treatment + MBR treatment to obtain a first treated liquid and a first sludge;

[0008] S2, the first treatment liquid is subjected to iron-carbon micro-electrolysis treatment, and the filler used in the iron-carbon micro-electrolysis treatment reacts with the first treatment liquid to obtain a filler containing Fe 2+ a second treatment solution containing ions;

[0009] S3, containing Fe 2+ The second treatment liquid of the ions is subjected to ultraviolet catalytic oxidation treatment, and an oxidant is added in batches during the treatment to obtain a third treatment liquid;

[0010] S4, adding a coagulant aid to the third treated liquid for coagulation and sedimentation treatment to obtain a supernatant and a second sludge;

[0011] S5, discharging the supernatant after the coagulation and sedimentation treatment into an aerated biological filter for treatment to obtain clean water;

[0012] S6. The first sludge and the second sludge are subjected to filter pressing treatment to form mud cakes and then landfilled.

[0013] In a specific embodiment, in step S1, two-stage AO biochemical treatment is performed first, and then MBR treatment is performed, and the carbon source required by denitrifying bacteria is added during the AO biochemical treatment.

[0014] In a specific embodiment, the COD (chemical oxygen demand) equivalent of the carbon source is 250,000-1,000,000 mg / L, the total nitrogen concentration is less than 700 mg / L, the pH is 4-9, and the ratio of BOD (biochemical oxygen demand) to COD is greater than 0.5.

[0015] In a specific embodiment, the aeration rate during the iron-carbon micro-electrolysis treatment is controlled at 5-50 L / min, the reaction time is 1-2 h, and the pH value is adjusted to 3-4.

[0016] In a specific embodiment, the iron-carbon micro-electrolysis treatment uses a multi-metal fusion catalyst as a filler, the filler has a particle size of 3-4 cm, an iron content of 50-75%, a carbon content of 10-15%, a catalyst content of 5-10%, a porosity of 60-75%, an activator content of 1-5%, and a density of 1.3 g / cm3.

[0017] In a specific embodiment, the HRT (hydraulic retention time) of the ultraviolet catalytic oxidation treatment is 0.5-1h, the ultraviolet wavelength is 200-280nm, and the irradiation time is 10-30min.

[0018] In a specific embodiment, the oxidant is H 2 O 2 , the H 2 O 2 The mass concentration of H 2 O 2 The added volume is 0.5-10‰ of the volume of the landfill leachate, and the oxidation time is 15-60min.

[0019] In a specific embodiment, during the coagulation and sedimentation treatment, the pH value of the third treatment liquid is adjusted to 6-9, and a coagulant is added to achieve mud-water separation, wherein the dosage of the coagulant is 0.5-1 ppm.

[0020] In a specific embodiment, the coagulant aid is a combination of one or more of polyaluminium ferric chloride, polyferric sulfate and polyaluminium chloride.

[0021] In a specific embodiment, the HRT of the supernatant in the aerated biological filter is 1-3h, and porous ceramsite is added into the aerated biological filter.

[0022] The method of the present invention has at least the following beneficial effects:

[0023] 1. This method uses the filler to react with the first treatment liquid during the iron-carbon micro-electrolysis process to produce a small amount of Fe 2+ ions and a large number of free radicals to degrade some organic matter in the first treatment solution, Fe 2+ The ion consumption is small and there is no need to add ferrous sulfate. On the other hand, by adding the oxidant in batches during the ultraviolet catalytic oxidation treatment, not only the dosage and iron sludge production are greatly reduced, but also the utilization rate of the reagents is improved, the wastewater treatment efficiency is improved, and the cost of reagent addition is reduced.

[0024] 2. This method can effectively utilize the residual Fe in the second treatment solution during UV catalytic oxidation treatment. 2+ Ions, while further improving the removal rate of organic matter in wastewater, also reduce the inhibition of chemical agents on the activity of microorganisms in subsequent aerated biological filter treatment and improve the biodegradability of wastewater.

[0025] 3. This method uses an aerated biological filter to treat the oxidized tail water, which can achieve simultaneous carbon removal and nitrogen removal, with a higher denitrification load. It does not require the design of a secondary sedimentation tank, which reduces the floor space and further reduces the treatment cost.

[0026] In summary, this method combines the optimized advanced oxidation treatment process consisting of iron-carbon micro-electrolysis treatment, ultraviolet catalytic oxidation treatment and coagulation and sedimentation treatment with aerated biological filter treatment for the first time to deeply treat landfill leachate, which not only meets the emission standards but also significantly reduces the treatment cost.

[0027] Another object of the present invention is to provide a landfill leachate treatment system for implementing the landfill leachate treatment method. The system comprises a regulating tank, an AO biochemical + MBR treatment device, an iron-carbon micro-electrolysis treatment device, an ultraviolet catalytic oxidation treatment device, a coagulation sedimentation tank, an aerated biological filter and a clear water tank connected in sequence, the outlet ends of the AO biochemical + MBR treatment device and the coagulation sedimentation tank are also connected to a sludge thickening tank, and the outlet end of the sludge thickening tank is connected to a sludge dewatering device.

[0028] The system requires a small amount of reagents, has a high reagent utilization rate, and has a high treatment efficiency. By using an aerated biological filter to treat the oxidized tail water, carbon removal and nitrogen removal can be performed simultaneously. The reactor has a higher denitrification load and does not require the design of a secondary sedimentation tank, which reduces the floor space and reduces the system construction cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the process flow chart of the existing landfill leachate treatment process.

[0030] Figure 2 FIG. 1 is a process flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0032] Combine the following Figure 2 The embodiment of the landfill leachate treatment process is specifically described. Figure 2 FIG. 1 is a process flow chart of an embodiment of the present invention.

[0033] like Figure 2As shown, first, the leachate is discharged into the AO biochemical + MBR treatment device after the water quality and water volume are uniformed through the regulating tank, and two-stage AO biochemical treatment + MBR treatment is carried out. The carbon source required by denitrifying bacteria is added during the AO biochemical treatment, and the air required for aeration is provided by the Roots blower. Most of the organic matter is degraded by the action of microorganisms, and then filtered through the MBR membrane to achieve mud and water separation to obtain the first treated liquid and the first sludge. Compared with the first-stage AO biochemical treatment, the two-stage AO biochemical treatment has a better denitrification effect and can better cope with water quality fluctuations. The COD equivalent in the carbon source is 250,000-1 million mg / L, the total nitrogen concentration is less than 700 mg / L, the pH is 4-9, and the BOD / COD is greater than 0.5. The carbon source uses a composite carbon source compounded with chemical waste or syrup. Chemical waste can be organic solvent waste liquid such as methanol, ethanol, acetone, etc., or fermentation waste liquid generated from processes such as alcohol production and antibiotic manufacturing, or antibiotic production waste liquid or vitamin production waste liquid; syrup can be corn syrup, sucrose syrup, glucose syrup or fructose syrup.

[0034] Then, the first treatment liquid is subjected to optimized advanced oxidation treatment. The specific steps are: the first treatment liquid is discharged into the iron-carbon micro-electrolysis treatment device, the first treatment liquid is subjected to iron-carbon micro-electrolysis treatment, and the filler used in the iron-carbon micro-electrolysis treatment reacts with the first treatment liquid to obtain a Fe-containing 2+ During this step of treatment, the aeration volume of the iron-carbon micro-electrolysis treatment device is controlled at 5-50L / min, the reaction time is 1-2h, and the pH value of the treatment liquid in the iron-carbon micro-electrolysis treatment device is adjusted to 3-4 by adding sulfuric acid and the pH automatic control system. No precipitation is required to obtain a second treatment liquid containing Fe 2+ The second treatment liquid of the ions is directly discharged into the subsequent ultraviolet catalytic oxidation treatment device.

[0035] Iron-carbon micro-electrolysis treatment uses a multi-metal fusion catalyst as a filler. This filler is produced by high-temperature reduction technology. The filler includes iron, carbon and a catalyst, and the catalyst is composed of rare earth elements. The particle size of the filler is controlled to be 3-4 cm, the iron content is 50-75%, the carbon content is 10-15%, the catalyst content is 5-10%, the porosity is 60-75%, the activator content is 1-5%, and the density is 1.3 g / cm 3 Specifically, the filler can be the "high temperature fired non-caking iron-carbon filler" of Shandong Yichuang Environmental Protection Company.

[0036] In the UV catalytic oxidation treatment device, Fe 2+ The second treatment liquid containing ions is subjected to ultraviolet catalytic oxidation treatment, wherein the oxidant is H 2 O 2 , and H was added in batches during the treatment period. 2 O2 After the reaction is completed, the third treatment liquid is obtained. In this treatment process, the HRT of the ultraviolet catalytic oxidation treatment is controlled to be 0.5-1h, the ultraviolet wavelength is 200-280nm, and the irradiation time is 10-30min. 2 O 2 The mass concentration of H 2 O 2 The total volume added is 0.5-

[0037] 10‰, oxidation time is 15-60min.

[0038] The third treated liquid is discharged into the coagulation sedimentation tank, and a coagulant is added to the third treated liquid in the coagulation sedimentation tank for coagulation sedimentation treatment to obtain a supernatant and a second sludge. In this treatment process, by adding liquid alkali to the coagulation sedimentation tank, the pH automatic control system adjusts the pH value of the treated liquid in the sedimentation tank to 6-9, and adds a coagulant to achieve mud-water separation to obtain a supernatant and a second sludge. Among them, the dosage of the coagulant is 0.5-1ppm, and the coagulant includes a combination of one or more of polyaluminum ferric chloride, polyferric sulfate and polyaluminum chloride, and the liquid alkali can be a NaOH solution.

[0039] Then, the supernatant is treated in an aerated biological filter. The specific operation is: the supernatant is discharged into the aerated biological filter for treatment, and finally clean water is obtained. In this step, a Roots blower is used to provide the air required for aeration, and the HRT of the supernatant in the aerated biological filter is controlled to be 1-3h, and porous ceramsite is added to the aerated biological filter.

[0040] Finally, the first sludge and the second sludge are filtered through an existing sludge thickening tank and a sludge dewatering device to form mud cakes and then landfilled.

[0041] In order to better implement the technical solution of the present invention, the following is a case where the leachate from a landfill is 400m 3 / d as an example, the implementation manner of the present invention is further described in conjunction with specific embodiments.

[0042] Example 1

[0043] The COD concentration in the landfill leachate was measured to be 7121.43 mg / L before treatment. During treatment, the landfill leachate was first passed through a regulating tank to even out the water quality and quantity, and then subjected to two-stage AO biochemical treatment + MBR treatment. After mud and water separation, the first treated liquid and the first sludge were obtained. The first treated liquid after MBR treatment was pumped into the iron-carbon micro-electrolysis treatment device through a lifting pump. The liquid inlet end of the iron-carbon micro-electrolysis treatment device was connected to a pipeline mixer. The first treated liquid was mixed with concentrated sulfuric acid in the pipeline mixer, so that the pH value of the first treated liquid entering the carbon micro-electrolysis treatment device was adjusted to 3.0, and the HRT of the carbon micro-electrolysis treatment device for iron-carbon micro-electrolysis was controlled to be 1.5h. The second treated liquid obtained after the reaction did not need to be precipitated and could be directly discharged into the ultraviolet catalytic oxidation treatment device. During iron-carbon micro-electrolysis, the micro-electric field generated around the filler causes free radicals to be generated at the cathode and the anode, including hydrogen ions at the cathode and ferrous ions and free radicals such as superoxide at the anode. These free radicals degrade part of the organic matter in the first treatment liquid, and ferrous ions are not the main reactant at this stage, so the consumption of ferrous ions is relatively small. The COD removal rate in the discharged second treatment liquid is 21.53%, and Fe 2+ Ion residual 100mg / L.

[0044] After the second treatment liquid is discharged into the ultraviolet catalytic oxidation treatment device through the pump, the ultraviolet lamp is turned on for 30 minutes, and 80 mg / L of H 2 O 2 , the residual Fe in the second treatment solution 2+ The ions were fully utilized. At this time, the COD concentration in the second treated liquid was measured to be degraded by 53.69% on the basis of iron-carbon micro-electrolysis treatment. Then, 1 mM 30% H 2 O 2 , added 3 times in total, that is, the total reaction time is 30 minutes, and the third treated liquid is obtained after the reaction is completed.

[0045] The third treated liquid is discharged into a coagulation sedimentation tank, and the pH value of the third treated liquid in the coagulation sedimentation tank is adjusted to 7.0 by adding NaOH solution, and 0.6 ppm of coagulant aid is added to precipitate it to obtain a supernatant and a second sludge.

[0046] The supernatant is discharged into the aerated biological filter through a pipe. No additional carbon source is required from the outside. The hydraulic retention time is 2 hours. Organic matter and nitrogen are removed simultaneously to finally obtain clean water.

[0047] The first sludge and the second sludge are filtered through the existing sludge thickening tank and sludge dewatering device to form mud cakes and then landfilled.

[0048] In this embodiment, the COD concentration and ammonia nitrogen (NH3 The specific calculation results of the concentration of 2-nitrogen (N), total nitrogen (TN), the treatment efficiency of each step and the total treatment efficiency of the deep treatment stage (iron-carbon micro-electrolysis treatment + ultraviolet catalytic oxidation treatment + coagulation sedimentation tank treatment + aerated biological filter treatment) are shown in Table 1. In Table 1, the data in the three columns on the right refer to the data after the corresponding steps are completed; and the deep treatment stage in the last row refers to the deep treatment starting from the iron-carbon micro-electrolysis treatment, so the last row refers to the treatment efficiency of various indicators in the clean water compared with the various indicators after "two-stage AO biochemical treatment + MBR treatment".

[0049] Table 1

[0050]

[0051] In this embodiment, the first treated liquid after two-stage AO biochemical treatment + MBR treatment has COD, NH 3 -N and TN in the deep treatment stage, the total treatment efficiency was 97.82%, 99.68% and 64.72% respectively, and the deep treatment stage of the present invention, the reagent (H 2 O 2 The cost of adding the coagulant + filler) is 14.72 yuan / ton, of which the coagulant and filler account for a very small proportion of the cost of the agent. Generally, the filler in the present invention only needs to be replaced part of it according to actual conditions every year of use.

[0052] In this embodiment, the first treated liquid after two-stage AO biochemical treatment + MBR treatment has a higher total treatment efficiency and dosage of reagents (FeSO 4 +H 2 O 2 The specific calculation results of the cost are shown in Table 2.

[0053] Table 2

[0054]

[0055] As can be seen from Table 1, after the landfill leachate has been treated with two-stage AO biochemical treatment + MBR treatment, and then the deep treatment process of the present application (iron-carbon micro-electrolysis treatment, ultraviolet catalytic oxidation treatment, coagulation sedimentation treatment and aerated biological filter treatment) is used to obtain clean water with a COD concentration of <100 mg / L, and the COD concentration has even dropped to below 50 mg / L, and the ammonia nitrogen (NH 3 -N) concentration ≤ 10mg / L, total nitrogen (TN) concentration ≤ 40mg / L, and all indicators of clean water meet the standards of Table 2 in the "Pollution Control Standards for Municipal Waste Landfills" (GB16889-2008).

[0056] From the comparison between Table 1 and Table 2, it can be seen that the COD concentration, NH 3 -N concentration and TN concentration indicators are better than the existing traditional treatment process. In addition, since the existing traditional treatment process requires the addition of FeSO 4 + and H 2 O 2 The amount of both agents is large, and the H in this application 2 O 2 The batch addition method is adopted to make H 2 O 2 The utilization rate of the oxidant can be fully utilized, and the utilization rate of the oxidant is greatly improved. In addition, the present application adopts iron-carbon micro-electrolysis treatment, which mainly produces a large number of free radicals to degrade organic matter, Fe 2+ The consumption of ions is small, thus reducing the cost of adding reagents.

[0057] In addition, the present application adopts an aerated biological filter to treat the oxidized tail water. Compared with the existing traditional biochemical treatment (cyclic activated sludge treatment or oxidation ditch treatment) of the tail water, it can simultaneously remove carbon and nitrogen, with a higher denitrification load, and there is no need to design a secondary sedimentation tank, which reduces the footprint and reduces the treatment cost.

[0058] The present invention effectively combines the optimized advanced oxidation process and aerated biological filter treatment to perform deep treatment of landfill leachate, so that the landfill leachate meets the discharge standards and reduces the treatment cost. This deep treatment method has the advantages of small dosage of reagents, high utilization rate, low operating cost, small footprint, high treatment efficiency, etc., and can achieve true environmental friendliness.

[0059] Example 2

[0060] Compared with Example 1, the COD concentration in the landfill leachate is greatly increased to 17000 mg / L. During the treatment, the landfill leachate is first passed through a regulating tank to even out the water quality and quantity, and then subjected to a two-stage AO biochemical treatment + MBR treatment. After mud and water separation, a first treated liquid and a first sludge are obtained. The first treated liquid after the MBR treatment is pumped into the iron-carbon micro-electrolysis treatment device through a lifting pump. The liquid inlet end of the iron-carbon micro-electrolysis treatment device is connected to a pipeline mixer. The first treated liquid is mixed with concentrated sulfuric acid in the pipeline mixer, so that the pH value of the first treated liquid entering the iron-carbon micro-electrolysis treatment device is adjusted to 3.0. The HRT of the iron-carbon micro-electrolysis treatment device for iron-carbon micro-electrolysis is controlled to be 1.5h. After the reaction is completed, the second treated liquid obtained does not need to be precipitated and can be directly drained. The COD concentration removal rate in the discharged second treated liquid is measured to be 32.60%, and the Fe 2+ Ion residual 96.8mg / L.

[0061] The second treatment liquid is discharged into the ultraviolet catalytic oxidation treatment device through a pump. The ultraviolet lamp is turned on for 30 minutes. The residual Fe 2+ The ions were fully utilized. At this time, the COD concentration in the second treated liquid was measured to be degraded by 50% on the basis of iron-carbon micro-electrolysis treatment. Then, 1 mM 30% H 2 O 2 , added 3 times in total, that is, the total reaction time is 30 minutes, and the third treated liquid is obtained after the reaction is completed.

[0062] The third treated liquid is discharged into the coagulation sedimentation tank through a pipeline, and the pH value of the wastewater is adjusted to 7.0 by adding NaOH solution, and 0.6 ppm of coagulant is added to make it precipitate, thereby obtaining a supernatant and a second sludge.

[0063] The supernatant is discharged into the aerated biological filter through a pipeline. No external carbon source is required. The hydraulic retention time is 2 hours. Organic matter and nitrogen are removed simultaneously to finally obtain clean water.

[0064] The first sludge and the second sludge are filtered through the existing sludge thickening tank and sludge dewatering device to form mud cakes and then landfilled.

[0065] In this embodiment, the COD concentration and ammonia nitrogen (NH 3 The specific calculation results of nitrogen (N) concentration, total nitrogen (TN) concentration, treatment efficiency of each step and the total efficiency of the deep treatment stage (iron-carbon micro-electrolysis treatment + ultraviolet catalytic oxidation treatment + coagulation sedimentation tank treatment + aerated biological filter treatment) are shown in Table 3.

[0066] Table 3

[0067]

[0068]

[0069] It can be seen from Table 3 that even when the COD concentration in the landfill leachate reaches 17000 mg / L, the COD concentration in the clean water obtained after treatment by the method of the present invention can be reduced to below 50 mg / L. 3 -N concentration is below 2mg / L, and TN concentration is below 10mg / L. It further illustrates that the method of the present invention can effectively treat landfill leachate containing high concentration of COD to meet the standards before discharge, and the effluent water quality is even better than the current water quality standards (standards in Table 2 of GB16889-2008). At the same time, the treatment method requires less dosage of reagents, which reduces the treatment cost while maintaining a high pollutant removal efficiency.

[0070] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for treating landfill leachate, characterized in that: The steps include: S1, the landfill leachate is passed through a regulating tank to make the water quality and quantity uniform, and then subjected to AO biochemical treatment + MBR treatment to obtain a first treated liquid and a first sludge; S2, the first treatment liquid is subjected to iron-carbon micro-electrolysis treatment, and the filler used in the iron-carbon micro-electrolysis treatment reacts with the first treatment liquid to obtain a filler containing Fe 2+ a second treatment solution containing ions; S3, containing Fe 2+ The second treatment liquid of the ions is subjected to ultraviolet catalytic oxidation treatment, and an oxidant is added in batches during the treatment to obtain a third treatment liquid; S4, adding a coagulant aid to the third treated liquid for coagulation and sedimentation treatment to obtain a supernatant and a second sludge; S5, discharging the supernatant after the coagulation and sedimentation treatment into an aerated biological filter for treatment to obtain clean water; S6. The first sludge and the second sludge are subjected to filter pressing treatment to form mud cakes and then landfilled.

2. The method for treating landfill leachate according to claim 1, characterized in that: In step S1, two-stage AO biochemical treatment is first performed, and then MBR treatment is performed, and the carbon source required by denitrifying bacteria is added during the AO biochemical treatment.

3. The method for treating landfill leachate according to claim 2, characterized in that: The COD equivalent of the carbon source is 250,000-1,000,000 mg / L, the total nitrogen concentration is less than 700 mg / L, the pH is 4-9, and the ratio of BOD to COD is greater than 0.

5.

4. The method for treating landfill leachate according to claim 1, characterized in that: During the iron-carbon micro-electrolysis treatment, the aeration volume was controlled at 5-50 L / min, the reaction time was 1-2 h, and the pH value was adjusted to 3-4.

5. The method for treating landfill leachate according to claim 4, characterized in that: The iron-carbon micro-electrolysis process uses a multi-metal fusion catalyst as a filler, the filler has a particle size of 3-4 cm, an iron content of 50-75%, a carbon content of 10-15%, a catalyst content of 5-10%, a porosity of 60-75%, an activator content of 1-5%, and a density of 1.3 g / cm 3 .

6. The method for treating landfill leachate according to claim 1, characterized in that: The HRT of the ultraviolet catalytic oxidation treatment is 0.5-1h, the ultraviolet wavelength is 200-280nm, and the irradiation time is 10-30min.

7. The method for treating landfill leachate according to claim 6, characterized in that: The oxidant is H2O2, the mass concentration of the H2O2 is 30%, the total volume of the H2O2 added is 0.5-10‰ of the volume of the landfill leachate, and the oxidation time is 15-60 minutes.

8. The method for treating landfill leachate according to claim 1, characterized in that: During the coagulation and sedimentation treatment, the pH value of the third treatment liquid is adjusted to 6-9, and a coagulant is added to achieve mud-water separation, wherein the dosage of the coagulant is 0.5-1ppm, and the coagulant is a combination of one or more of polyaluminum ferric chloride, polyferric sulfate and polyaluminum chloride.

9. The method for treating landfill leachate according to claim 8, characterized in that: The HRT of the supernatant treated in the aerated biological filter is 1-3h, and porous ceramsite is added into the aerated biological filter.

10. A landfill leachate treatment system, characterized in that: The method for treating landfill leachate according to any one of claims 1 to 9 comprises a regulating tank, an AO biochemical + MBR treatment device, an iron-carbon micro-electrolysis treatment device, an ultraviolet catalytic oxidation treatment device, a coagulation sedimentation tank, an aerated biological filter and a clear water tank connected in sequence, wherein the outlet ends of the AO biochemical + MBR treatment device and the coagulation sedimentation tank are also connected to a sludge thickening tank, and the outlet end of the sludge thickening tank is connected to a sludge dewatering device.

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