Treatment method of landfill leachate

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a landfill leachate treatment method. The embodiment of the invention discloses a treatment method of landfill leachate. The treatment method comprises the following steps: (1) pretreating the landfill leachate, and then carrying out electron beam irradiation concerted catalysis treatment; (2) the effluent subjected to electron beam irradiation concerted catalysis treatment enters a biochemical treatment system; (3) enabling effluent passing through the biochemical treatment system to enter a membrane treatment system; and (4) the strong brine passing through the membrane treatment system enters evaporative crystallization equipment. The method can be used for treating the landfill leachate which is high in organic matter content, high in salt content and difficult to biodegrade, and compared with a traditional treatment method, the method is simpler and more efficient and has a better application prospect.

Description

Technical Field

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

[0002] With the rapid development of my country's economy, the discharge of wastewater, waste gas and waste residue has brought serious environmental pollution. Leachate refers to a high-concentration organic wastewater formed by the water contained in the garbage itself in the landfill, the rain and snow water entering the landfill and other water, minus the saturated water holding capacity of the garbage and the covering soil layer, and passing through the garbage layer and the covering soil layer. The characteristics of leachate include: (1) a large number of organic matter types, complex composition, and high toxicity; high organic concentration and a wide range of variation; (2) high ammonia nitrogen content; (3) low pH value and relatively high suspended matter content; (4) high salt content, with chloride ion concentration as high as thousands of milligrams per liter; (5) contains a variety of heavy metals.

[0003] The concentrations of pollutants such as COD, ammonia nitrogen, total phosphorus, and chromaticity in landfill leachate are extremely high. If they are not effectively treated, they will cause great damage to the surrounding environment. In particular, high-concentration organic matter in landfill leachate is difficult to remove effectively, which will cause serious membrane pollution and clogging of evaporation and crystallization equipment in subsequent treatment processes. Therefore, it is of great significance and market value to develop a new method to effectively degrade the difficult-to-degrade organic matter in landfill leachate, improve traditional biochemical treatment, membrane treatment and evaporation and crystallization treatment technologies, and achieve zero discharge of landfill leachate. Summary of the invention

[0004] The present invention is based on the inventor's discovery and understanding of the following facts and problems:

[0005] Landfill leachate is a typical high-salinity, high-organic-matter-difficult-to-degrade wastewater, in which there are many types of organic matter and complex components. It is difficult to degrade the organic matter using conventional sewage treatment methods. At the same time, since landfill leachate contains heavy metals, toxic and harmful substances and high levels of salt, the growth of microorganisms is restricted, making it difficult for sewage biochemical treatment technology to play an effective role. High concentrations of difficult-to-degrade organic matter will lead to serious membrane pollution and blockage of evaporation and crystallization equipment. At present, organic matter in landfill leachate is often treated by advanced oxidation, ozone oxidation, electrochemistry and other methods. The existing methods have complex process flows, require the introduction of a large number of chemical substances, and have high treatment costs. Therefore, it is necessary to conduct in-depth research on the removal of organic matter in landfill leachate to reduce the problems of membrane pollution and evaporation and crystallization equipment blockage in subsequent processes.

[0006] The present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, an embodiment of the present invention provides a method for treating landfill leachate, which can treat landfill leachate with high organic matter content, high salt content, and poor biodegradability. Compared with traditional treatment methods, the method is simpler and more efficient, and has better application prospects.

[0007] The method for treating landfill leachate according to the embodiment of the present invention comprises the following steps:

[0008] (1) Pre-treating the landfill leachate and then subjecting it to electron beam irradiation synergistic catalytic treatment;

[0009] (2) the effluent from the electron beam irradiation synergistic catalytic treatment described in step (1) enters the biochemical treatment system;

[0010] (3) the effluent from the biochemical treatment system of step (2) enters the membrane treatment system;

[0011] (4) The concentrated brine passing through the membrane treatment system described in step (3) enters the evaporation crystallization equipment.

[0012] The advantages and technical effects brought by the method for treating the landfill leachate of the embodiment of the present invention are as follows: 1. The method of the embodiment of the present invention adopts the electron beam irradiation synergistic catalytic treatment method to reduce the organic matter, toxic and harmful substances, heavy metals, etc. in the landfill leachate, change the molecular structure of the difficult-to-degrade organic matter in the landfill leachate, improve the ability of subsequent biochemical treatment, slow down membrane pollution, and ensure that the concentrated brine after membrane treatment enters the evaporation crystallization equipment without causing equipment blockage; 2. The method of the embodiment of the present invention adds a catalyst during the electron beam irradiation process to improve the COD degradation efficiency of the landfill leachate, while improving the biodegradability of the landfill leachate after treatment and reducing the content of toxic and harmful substances, which is beneficial to subsequent biochemical treatment; 3. The method of the embodiment of the present invention adopts a biochemical treatment system that can utilize microorganisms to degrade organic matter, nitrogen, phosphorus, etc., the water produced by the membrane treatment system can be recycled and reused, the condensed water after the concentrated brine enters the evaporation crystallization equipment can be used as recycled water, and the separated salt can be recycled, thereby achieving zero discharge of landfill leachate; 4. Compared with the existing landfill leachate treatment method, the method of the embodiment of the present invention is simpler and more efficient, and is easy to promote and apply.

[0013] In some embodiments, in step (1), the pretreatment includes grid filtration and flocculation sedimentation.

[0014] In some embodiments, the pore size of the grid is 1 to 5 mm; and / or the flocculant used in the flocculation precipitation includes at least one of polyaluminum chloride, polyferric sulfate, polyaluminum ferric chloride and polyacrylamide.

[0015] In some embodiments, in the step (1), the energy of the electron beam irradiation is 3 to 10 MeV, the beam current intensity is 50 to 300 mA, and the irradiation dose is 1 to 30 KGy; and / or, the catalyst used in the electron beam irradiation synergistic catalytic treatment includes at least one of a multi-metal oxygen-containing material and a multi-metal material, wherein the metal includes at least one of iron, aluminum, copper, manganese, cobalt, vanadium, chromium, nickel, calcium, magnesium, titanium, and zinc.

[0016] In some embodiments, in the step (1), a chemical additive is added to the landfill leachate before the electron beam irradiation synergistic catalytic treatment, wherein the chemical additive includes at least one of hydrogen peroxide, sodium hypochlorite, potassium permanganate, ferric sulfate, and manganese chloride.

[0017] In some embodiments, the amount of the chemical additive added is 0.01-5 g / L.

[0018] In some embodiments, in step (2), the biochemical treatment system includes anaerobic treatment, anoxic treatment and aerobic treatment.

[0019] In some embodiments, in step (3), the membrane treatment system includes an ultrafiltration membrane treatment system and a reverse osmosis membrane treatment system.

[0020] In some embodiments, in step (3), the pore size of the ultrafiltration membrane is 10 to 100 nm, and the pore size of the reverse osmosis membrane is 0.1 to 1 nm.

[0021] In some embodiments, in step (4), the evaporation crystallization equipment includes a single-effect evaporation equipment or a multi-effect evaporation equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flow chart of the method for treating landfill leachate in Example 1. DETAILED DESCRIPTION

[0023] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0024] The method for treating landfill leachate according to the embodiment of the present invention comprises the following steps:

[0025] (1) Pre-treating the landfill leachate and then subjecting it to electron beam irradiation synergistic catalytic treatment;

[0026] (2) the effluent from the electron beam irradiation synergistic catalytic treatment described in step (1) enters the biochemical treatment system;

[0027] (3) the effluent from the biochemical treatment system of step (2) enters the membrane treatment system;

[0028] (4) The concentrated brine passing through the membrane treatment system described in step (3) enters the evaporation crystallization equipment.

[0029] The method for treating the landfill leachate of the embodiment of the present invention adopts an electron beam irradiation synergistic catalytic treatment method to reduce organic matter, toxic and harmful substances, heavy metals, etc. in the landfill leachate, change the molecular structure of the difficult-to-degrade organic matter in the landfill leachate, improve the ability of subsequent biochemical treatment, slow down membrane pollution, and ensure that the concentrated brine after membrane treatment enters the evaporation crystallization equipment without causing equipment blockage; adding a catalyst during the electron beam irradiation process can improve the COD degradation efficiency of the landfill leachate, while improving the biodegradability of the landfill leachate after treatment and reducing the content of toxic and harmful substances, which is beneficial to subsequent biochemical treatment; the adopted biochemical treatment system can utilize microorganisms to degrade organic matter, nitrogen, phosphorus, etc., the water produced by the membrane treatment system can be recycled and reused, the condensed water after the concentrated brine enters the evaporation crystallization equipment can be used as recycled water, and the separated salt can be recycled, thereby achieving zero discharge of the landfill leachate; compared with the existing landfill leachate treatment method, it is simpler and more efficient, and is easy to promote and apply.

[0030] In some embodiments, preferably, in the step (1), the pretreatment includes grid filtration and flocculation precipitation. Further preferably, the pore size of the grid is 1 to 5 mm; and / or, the flocculant used in the flocculation precipitation includes at least one of polyaluminum chloride, polyferric sulfate, polyaluminum ferric chloride and polyacrylamide. More preferably, when the flocculant is polyaluminum chloride (PAC), polyferric sulfate (PFS) or polyaluminum ferric chloride, the dosage of the flocculant is 100 to 2000 mg / L; when the flocculant is polyacrylamide, the dosage of the flocculant is 1 to 10 mg / L.

[0031] In the embodiment of the present invention, grid filtration and flocculation sedimentation are performed, which can filter out solid impurities with larger particles in the landfill leachate on the one hand, and can flocculate and precipitate colloids, particulate matter, organic matter and other substances in the landfill leachate on the other hand, thereby reducing the difficulty of subsequent treatment.

[0032] In some embodiments, preferably, in step (1), the energy of the electron beam irradiation is 3-10 MeV, the beam current intensity is 50-300 mA, and the irradiation dose is 1-30 KGy; and / or, the catalyst used in the electron beam irradiation synergistic catalytic treatment includes at least one of a multi-metal oxygen-containing material and a multi-metal material, wherein the metal includes at least one of iron, aluminum, copper, manganese, cobalt, vanadium, chromium, nickel, calcium, magnesium, titanium, and zinc. Further preferably, the amount of the catalyst is 0.1-5 g / L.

[0033] In the embodiment of the present invention, the irradiation dose of the electron beam is optimized to achieve better treatment effect; if the irradiation dose is too low, the treatment effect is not ideal; if the irradiation dose is too high, not only will there be no obvious improvement in the treatment effect, but it will also increase the treatment cost of the landfill leachate.

[0034] In some embodiments, preferably, in the step (1), a chemical additive is added to the landfill leachate before the electron beam synergistic catalytic irradiation treatment, wherein the chemical additive comprises at least one of hydrogen peroxide, sodium hypochlorite, potassium permanganate, ferric sulfate, and manganese chloride. Further preferably, the amount of the chemical additive added is 0.01 to 5 g / L.

[0035] In the embodiment of the present invention, the added chemical additives can fully utilize the free radicals and redox substances generated during the electron beam irradiation and catalysis process, and further improve the treatment effect of the landfill leachate.

[0036] In some embodiments, preferably, in step (2), the biochemical treatment system includes anaerobic treatment, anoxic treatment and aerobic treatment. Further preferably, the hydraulic retention time of the anaerobic treatment is 24 to 72 hours, the hydraulic retention time of the anoxic treatment is 12 to 36 hours, and the hydraulic retention time of the aerobic treatment is 24 to 72 hours. More preferably, the aerobic treatment includes at least one of SBR, biofilter, biorotor, biological contact oxidation tank, and aerobic MBR. More preferably, the microorganisms treated by the biochemical system are anaerobic, anoxic and aerobic microorganisms that have been cultured and domesticated with landfill leachate and are suitable for high-salt and high-COD environments.

[0037] In some embodiments, preferably, in step (3), the membrane treatment system includes an ultrafiltration membrane treatment system and a reverse osmosis membrane treatment system. Further preferably, in step (3), the pore size of the ultrafiltration membrane is 10 to 100 nm, and the pore size of the reverse osmosis membrane is 0.1 to 1 nm. More preferably, the recovery rate of the reverse osmosis membrane system is 50 to 90%, preferably 70 to 85%.

[0038] In the embodiment of the present invention, a double membrane treatment system is used to ensure the effect of membrane treatment; in addition, the effluent of the ultrafiltration membrane is used as the inlet water of the reverse osmosis membrane to ensure the stability of the reverse osmosis inlet water and extend the service life of the reverse osmosis membrane. After being treated by the membrane treatment system, the COD content in the concentrated brine can be guaranteed to be less than 150 mg / L, avoiding the problem of easy blockage of the evaporation crystallization equipment, and ensuring the long-term stable operation of the treatment process.

[0039] In some embodiments, preferably, in the step (4), the evaporation crystallization equipment comprises a single-effect evaporation equipment or a multi-effect evaporation equipment.

[0040] The technical solution of the present invention is described in detail below in conjunction with specific embodiments and drawings.

[0041] The multi-metal oxygen-containing materials used in the following embodiments are prepared by referring to the preparation method in the patent application (application number is 202110383631.6); the multi-metal materials are prepared by referring to the preparation method in the patent application (application number is 202110383641.X).

[0042] The landfill leachate used in the following Examples 1 to 5 and Comparative Example 1 was selected from the landfill leachate concentrate treated by membrane from a domestic waste landfill in Chongqing. The water contained obvious solid matter, was brown in color, and had a complex water quality (see Table 1). The BOD / COD value of the landfill leachate was 0.27, which was difficult to treat using conventional biological methods.

[0043] Table 1 Summary of water quality analysis of garbage concentrate (mg / L)

[0044]

[0045] Note: pH is dimensionless; the unit of color is times.

[0046] The water quality of the landfill leachate used in Example 6 and Comparative Example 2 is shown in Table 2:

[0047] Table 2

[0048]

[0049] Example 1

[0050] The method for treating the landfill leachate in this embodiment is as follows: Figure 1 As shown:

[0051] (1) filtering the landfill leachate through a screen to remove floating matter, solid matter, etc.;

[0052] (2) Adding polyferric chloride and polyacrylamide to the filtered landfill leachate to flocculate and settle suspended solids, organic matter, etc., wherein the addition amounts of polyferric chloride and polyacrylamide are 1000 mg / L and 1.5 mg / L, respectively; the color of the supernatant after flocculation and sedimentation becomes relatively lighter and the transparency increases;

[0053] (3) subjecting the solution after flocculation and precipitation to electron beam irradiation synergistic catalytic treatment, wherein the energy of the electron beam irradiation is 10 MeV, the beam current intensity is 60 mA, the irradiation dose is 10 KGy, the catalyst used is an iron-cobalt-zinc ternary oxygen-containing material, and the amount of the catalyst used is 2.5 g / L;

[0054] (4) The landfill leachate after electron beam irradiation and catalytic treatment enters the biochemical treatment system, and is treated by anaerobic treatment, anoxic treatment and aerobic treatment respectively. The anaerobic, anoxic and aerobic microorganisms are cultivated by gradually increasing the inflow of landfill leachate. The hydraulic retention time of anaerobic treatment is 36 h, the hydraulic retention time of anoxic treatment is 24 h, and the hydraulic retention time of aerobic treatment is 40 h.

[0055] (5) The effluent after biochemical treatment enters the membrane treatment system and is first filtered through an ultrafiltration membrane. The filtered water enters the reverse osmosis treatment system. The clean water after reverse osmosis treatment can be directly discharged or reused in compliance with the standards. The concentrated brine enters the evaporation crystallization equipment for desalination treatment. The pore size of the ultrafiltration membrane is 100 nm, the pore size of the reverse osmosis membrane is 0.5 nm, the recovery rate of the reverse osmosis treatment is 75%, and the concentration multiple is 4 times. The COD of the concentrated brine entering the evaporation crystallization equipment is 50 mg / L.

[0056] (6) The concentrated brine after being concentrated by the reverse osmosis membrane enters the evaporation crystallization equipment. The evaporated condensed water can be used as recycled water. The separated salt is mainly composed of sodium chloride, sodium sulfate, potassium chloride, etc.; it can be separated and recycled, or it can be landfilled.

[0057] Example 2

[0058] The treatment method of Example 2 is the same as that of Example 1, except that in step (3), the irradiation dose of the electron beam is 5 KGy.

[0059] Example 3

[0060] The treatment method of Example 3 is the same as that of Example 1, except that in step (3), the irradiation dose of the electron beam is 15 KGy.

[0061] Example 4

[0062] The treatment method of Example 4 is the same as that of Example 1, except that in step (3), the irradiation dose of the electron beam is 20 KGy.

[0063] Example 5

[0064] The treatment method of Example 5 is the same as that of Example 1, except that in step (3), the irradiation dose of the electron beam is 30 KGy.

[0065] The water quality of the garbage concentrate treated by electron beam irradiation and catalytic treatment in step (3) of Example 1 was analyzed, and the results are shown in Table 3:

[0066] Table 3 Water quality of garbage concentrate after electron beam irradiation and catalytic treatment (mg / L)

[0067]

[0068] The water quality of the clean water after reverse osmosis treatment in Example 1 was analyzed, and the results are shown in Table 4:

[0069] Table 4 Water quality after reverse osmosis treatment

[0070]

[0071] It can be seen from the data in Table 4 that after the landfill leachate is treated by the treatment process of Example 1, the water quality of the clean water can directly meet the discharge standards, thereby achieving effective treatment of the landfill leachate.

[0072] The water quality of the garbage concentrate treated by electron beam irradiation and catalytic treatment in Examples 1 to 5 was analyzed, and the COD content and degradation rate are shown in Table 5:

[0073] Table 5 COD content and COD degradation rate of landfill leachate under different irradiation doses

[0074] Radiation dose 5KGy 10KGy 15KGy 20KGy 30KGy COD(mg / L) 1218 1043.8 1180.5 1131.25 1218 COD degradation rate (%) 41.4 49.7 43.2 45.5 41.4

[0075] Example 6

[0076] The treatment method of this embodiment is the same as that of embodiment 1, except that: in step (3), the irradiation dose of the electron beam is adjusted and a chemical additive is added to study the degradation effect of COD under different irradiation conditions. The catalyst is an iron-nickel binary metal material, and the amount of the catalyst is 1 g / L; the chemical additive is hydrogen peroxide, and the amount of hydrogen peroxide added is 2 g / L. The results are shown in Table 6:

[0077] Table 6

[0078]

[0079] Comparative Example 1

[0080] The method is the same as that in Example 1, except that in step (3), instead of using the radiation synergistic catalytic treatment method to remove organic matter, a traditional organic matter removal method is used, specifically including: using the Fenton oxidation treatment method instead of electron beam irradiation, the pH of the Fenton reaction is 3, the dosage of ferrous sulfate and hydrogen peroxide is 1.7 g / L and 2.5 g / L respectively, and after the reaction, the pH of the solution is adjusted back to about 7.5; the water quality of the garbage concentrate treated in step (3) is analyzed, and the results are shown in Table 7:

[0081] Table 7

[0082]

[0083] Comparing the data in Table 3 and Table 7, it can be seen that the treatment method using electron beam irradiation and synergistic catalysis has a better treatment effect on organic pollutants than the Fenton oxidation treatment method in the prior art.

[0084] Comparative Example 2

[0085] The treatment method of this comparative example is the same as that of Example 6, except that: in step (3), instead of using the radiation synergistic catalytic treatment method to remove organic matter, a traditional method for removing organic matter is used, specifically including: using a Fenton oxidation treatment method instead of electron beam irradiation, the pH of the Fenton reaction is 3, the dosage of ferrous sulfate and hydrogen peroxide is 1.7 g / L and 2.5 g / L respectively, and after the reaction, the pH of the solution is adjusted back to about 7.5; the water quality of the garbage concentrate treated in step (3) is analyzed, and the results show that its COD content is 620 mg / L.

[0086] By comparing Example 6 and Comparative Example 2, it can be seen that the treatment method using electron beam irradiation synergistic catalysis has a better treatment effect on organic pollutants than the Fenton oxidation treatment method in the prior art; adding additives can further improve the effect of electron beam irradiation synergistic catalytic treatment and reduce the COD concentration in the leachate.

[0087] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0088] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A method for treating landfill leachate, characterized in that: The following steps are involved: (1) Pre-treating the landfill leachate and then subjecting it to electron beam irradiation synergistic catalytic treatment; (2) the effluent from the electron beam irradiation synergistic catalytic treatment described in step (1) enters the biochemical treatment system; (3) the effluent from the biochemical treatment system of step (2) enters the membrane treatment system; (4) The concentrated brine passing through the membrane treatment system described in step (3) enters the evaporation crystallization equipment.

2. The method for treating landfill leachate according to claim 1, characterized in that: In the step (1), the pretreatment includes grid filtration and flocculation sedimentation.

3. The method for treating landfill leachate according to claim 1, characterized in that: The aperture of the grid is 1-5 mm; and / or the flocculant used in the flocculation precipitation includes at least one of polyaluminium chloride, polyferric sulfate, polyaluminium ferric chloride and polyacrylamide.

4. The method for treating landfill leachate according to claim 1, characterized in that: In the step (1), the energy of the electron beam irradiation is 3 to 10 MeV, the beam current intensity is 50 to 300 mA, and the irradiation dose is 1 to 30 KGy; and / or the catalyst used in the electron beam irradiation synergistic catalytic treatment includes at least one of a multi-metal oxygen-containing material and a multi-metal material, wherein the metal includes at least one of iron, aluminum, copper, manganese, cobalt, vanadium, chromium, nickel, calcium, magnesium, titanium, and zinc.

5. The method for treating landfill leachate according to claim 1 or 4, characterized in that: In the step (1), a chemical additive is added to the landfill leachate before the electron beam irradiation synergistic catalytic treatment, wherein the chemical additive includes at least one of hydrogen peroxide, sodium hypochlorite, potassium permanganate, ferric sulfate, and manganese chloride.

6. The method for treating landfill leachate according to claim 5, characterized in that: The added amount of the chemical auxiliary agent is 0.01-5 g / L.

7. The method for treating landfill leachate according to claim 1, characterized in that: In the step (2), the biochemical treatment system includes anaerobic treatment, anoxic treatment and aerobic treatment.

8. The method for treating landfill leachate according to claim 1, characterized in that: In the step (3), the membrane treatment system includes an ultrafiltration membrane treatment system and a reverse osmosis membrane treatment system.

9. The method for treating landfill leachate according to claim 8, characterized in that: In the step (3), the pore size of the ultrafiltration membrane is 10 to 100 nm, and the pore size of the reverse osmosis membrane is 0.1 to 1 nm.

10. The method for treating landfill leachate according to claim 1, characterized in that: In the step (4), the evaporation crystallization equipment includes a single-effect evaporation equipment or a multiple-effect evaporation equipment.

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