Solid waste leachate combined treatment process

Abstract

The application discloses a kind of solid waste leachate combined treatment process, it is related to solid waste leachate processing technical field, including the following steps: solid waste leachate is sent into adjusting pool, water quality optimization, water quantity regulation are carried out, and pretreatment leachate is obtained;It is sent into two-stage A / O system, and high-concentration ammonia nitrogen and most of organic matter are removed, then it is sent into first sedimentation tank;It is sent into micro electrolysis-Fenton-coagulation sedimentation system, and COD is reduced, and biodegradability is improved, then it is sent into second sedimentation tank;It is sent into MBR membrane reactor, and organic matter in wastewater is completely decomposed into CO2 and H2O;The application realizes the cascade treatment of solid waste leachate and the gradual degradation of pollutants by the innovative coupling of biochemical treatment and advanced oxidation process, the advantages of each processing unit are fully utilized in the whole process, not only the treatment effect is remarkable, and operation is stable and reliable, with the characteristics of less secondary pollution, low operating cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste leachate treatment, in particular to a combined solid waste leachate treatment process. BACKGROUND

[0002] Solid waste leachate is a flowing product formed under the action of gravity due to the infiltration of natural precipitation, external surface water, groundwater, water contained in the waste itself, and water produced by biochemical reactions after landfill during the stacking and landfill of solid waste. This leachate mainly has the characteristics of extremely high pollutant concentration (COD concentration is generally 3000-60000 mg / L, BOD5 concentration is 1000-30000 mg / L, ammonia nitrogen concentration is 500-3000 mg / L), rapid change of water quality and quantity, complex composition, many types of toxic and harmful substances, containing multiple heavy metal ions, unbalanced proportion of microbial nutrients, high salt content, poor biodegradability, etc. If not properly treated, solid waste leachate will cause secondary pollution to the soil, groundwater, atmosphere, etc. around the site, and cause great harm to the human body.

[0003] At present, the solid waste leachate treatment technologies adopted at home and abroad mainly include three categories: physical and chemical methods, land treatment methods, and biological methods. The physical and chemical methods include coagulation, stripping, activated carbon adsorption, evaporation, chemical precipitation, ion exchange, membrane separation, etc., which are less affected by changes in water quality and quantity, have stable effluent quality, but have high treatment cost. The land treatment method includes slow infiltration, rapid infiltration, surface flow, constructed wetland, and recharging, etc., which has low investment and operation cost, strong impact load resistance, but is limited by land resources, and is easy to cause accumulation of heavy metals and salts in the soil, polluting the soil and groundwater. Biological methods include aerobic biological treatment (activated sludge method, aerated lagoon, biological rotating disc, etc.) and anaerobic biological treatment (anaerobic biological filter, anaerobic contact method, anaerobic mixed bed, etc.), which have low operation cost, high treatment efficiency, and will not produce chemical sludge, but are difficult to adapt to changes in water quality and quantity, especially high concentration of ammonia nitrogen and heavy metals will inhibit microbial activity.

[0004] CN110117136A discloses a landfill leachate treatment system and method. The system includes a leachate equalization tank, an anoxic tank, an aerobic tank, a flocculation sedimentation tank, a first intermediate water tank, a sand filter, a second intermediate water tank, a cartridge filter, a primary DTRO membrane system, a secondary DTRO membrane system, a concentrate tank, a PAM (Polymer Acetate Amide) dissolution and dosing device, and a PAC (Polymer Acetate Acetate Dosing) dissolution and dosing device. The method involves: first, adjusting the water quality and quantity of the landfill leachate; then, subjecting the equalized leachate to anaerobic biological treatment; next, subjecting the anaerobic leachate to aerobic biological treatment; then, subjecting the aerobic leachate to flocculation and sedimentation; next, subjecting the supernatant of the flocculated leachate to quartz sand filtration; then, subjecting the filtered leachate to two-stage DTRO treatment; finally, discharging the treated water that meets the standards after two-stage DTRO treatment; and reinjecting the concentrate from the multiple DTRO treatments back into the landfill.

[0005] It is particularly noteworthy that leachate from mid-to-late stage landfills is characterized by high ammonia nitrogen and poor biodegradability of organic matter. Currently, the widely used biological + membrane deep treatment process in engineering has problems such as poor biodegradability of effluent after biological treatment, the generation of concentrated solutions with high salinity and large amounts of metal ions during membrane treatment, and the potential for secondary pollution if the concentrated solutions are not properly treated.

[0006] Therefore, existing technologies lack a combined treatment process that can further couple and utilize different processes to achieve staged treatment of leachate and reduce the generation of concentrate. Developing an efficient, economical, and stable combined treatment process for landfill leachate is of significant practical importance. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a combined treatment process for solid waste leachate, which employs a biochemical-advanced oxidation-biochemical combined process to treat solid waste leachate. The advanced oxidation process improves the biodegradability of the wastewater, and no concentrate is generated during the entire treatment process.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A combined treatment process for solid waste leachate includes the following steps:

[0010] (1) The solid waste leachate is sent into the equalization tank for water quality optimization and water quantity adjustment to obtain pretreated leachate;

[0011] (2) The pretreated leachate is sent to a two-stage A / O system to remove high concentrations of ammonia nitrogen and most of the organic matter, and then sent to the first sedimentation tank.

[0012] (3) The effluent from the first sedimentation tank is sent into the micro-electrolysis-Fenton-coagulation sedimentation system to reduce COD and improve biodegradability, and then sent into the second sedimentation tank.

[0013] (4) The effluent from the second sedimentation tank is sent into the MBR membrane reactor to completely decompose the organic matter in the wastewater into CO2 and H2O.

[0014] Preferably, before step (2), the process also includes sludge aeration and cultivation, including the following steps: using pretreated leachate as a substrate, aerating and cultivating it with sludge from the wastewater treatment plant, filling the two-stage A / O system with tap water, controlling the dissolved oxygen in the two-stage A / O system at 2-6 mg / L, and adjusting the pH in the two-stage A / O system to 7-9.

[0015] Preferably, the initial ratio of pretreated leachate to tap water is 5:95, and then the proportion of pretreated leachate is gradually increased according to the ratios of 10:90, 20:80, 40:60, 60:40, 80:20, and 100:0, while increasing the reflux to achieve a sludge settling ratio of 60-80%; the aeration and cultivation time is 0.5-1.5 months to enable the two-stage A / O system to achieve a stable nitrification reaction.

[0016] Preferably, in step (2), the two-stage A / O system includes a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank, and a second-stage aerobic tank connected in sequence; in the first-stage anoxic tank, nitrate nitrogen in the reflux mixed liquor interacts with organic matter in the original wastewater and is reduced by denitrifying bacteria; the effluent from the first-stage anoxic tank enters the first-stage aerobic tank, where organic matter is oxidized and degraded, and organic nitrogen is converted into nitrate nitrogen; part of the effluent from the first-stage aerobic tank is returned to the first-stage anoxic tank, and part enters the second-stage anoxic tank; in the second-stage anoxic tank, undegraded nitrate nitrogen is degraded by denitrifying bacteria through external carbon source and endogenous respiration; the effluent from the second-stage anoxic tank enters the second-stage aerobic tank, where organic matter is oxidized and degraded, and organic nitrogen is converted into nitrate nitrogen; part of the effluent from the second-stage aerobic tank is returned to the second-stage anoxic tank, and part is sent to the first sedimentation tank.

[0017] Preferably, part of the sludge from the first sedimentation tank is returned to the primary anoxic tank, and part enters the sludge tank.

[0018] Preferably, in step (3), the micro-electrolysis-Fenton-coagulation sedimentation system includes a micro-electrolysis reaction tank, a Fenton oxidation reaction tank, and a coagulation tank connected in sequence; the effluent from the first sedimentation tank is sent to the micro-electrolysis reaction tank, acid is added to adjust the pH to 2-4, and aeration reaction is carried out to decompose and degrade the organic matter in the leachate; the effluent from the micro-electrolysis reaction tank is sent to the Fenton oxidation reaction tank, hydrogen peroxide solution is added, after the reaction is completed, alkali is added to adjust the pH to 8-9, and it is sent to the coagulation tank, where a coagulant aid is added for coagulation and sedimentation to separate the insoluble substances produced after advanced oxidation.

[0019] Preferably, the effluent from the coagulation tank is sent to the second sedimentation tank, and the sludge from the second sedimentation tank enters the sludge tank.

[0020] Preferably, the acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid; and the base is one or more of lime milk, sodium hydroxide, and sodium carbonate.

[0021] Preferably, the packing material in the micro-electrolysis reactor is iron-carbon micro-electrolysis packing material TPFC with a porosity of 60-80% and an iron-carbon ratio of 2-6:1; the ratio of iron-carbon micro-electrolysis packing material to wastewater is 200-400g:1L.

[0022] Specifically, the packing material in the micro-electrolysis reactor is iron-carbon micro-electrolysis packing material TPFC, with a porosity of 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, or 80%, and an iron-carbon ratio of 2:1, 3:1, 4:1, 5:1, or 6:1; the ratio of iron-carbon micro-electrolysis packing material to wastewater can be 200g:1L, 250g:1L, 300g:1L, 350g:1L, or 400g:1L.

[0023] Preferably, the concentration of hydrogen peroxide solution is 3-6 wt%, the ratio of hydrogen peroxide solution to wastewater is 1-6 mL:1 L, the reaction time is 60-300 min, and the coagulant is PAM, with a ratio of PAM to wastewater of 0.5-5 mL:1 L.

[0024] Specifically, the concentration of hydrogen peroxide solution can be 3, 4, 5, or 6 wt%, and the ratio of hydrogen peroxide solution to wastewater can be 1 mL:1 L, 2 mL:1 L, 3 mL:1 L, 4 mL:1 L, 5 mL:1 L, or 6 mL:1 L; the reaction time can be 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, or 300 min; the coagulant is PAM, and the ratio of PAM to wastewater can be 0.5 mL:1 L, 1 mL:1 L, 2 mL:1 L, 3 mL:1 L, 4 mL:1 L, or 5 mL:1 L.

[0025] Preferably, in step (4), the volume ratio of the anoxic tank to the membrane reactor in the MBR membrane reactor is 1:2, the membrane filaments are made of polyvinylidene fluoride hollow fiber membrane, the membrane filament pore size is 0.1μm, the porosity is 40-50%, and the working pressure is -0.1-0.03Mpa.

[0026] Preferably, the reflux ratio of the MBR membrane reactor is 100-300%; the sludge concentration in the MBR membrane reactor is 2000-3000 mg / L.

[0027] Specifically, the reflux ratio of the MBR membrane reactor can be 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, or 300%; and the sludge concentration in the MBR membrane reactor can be 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, or 3000 mg / L.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. This invention employs a two-stage A / O-microelectrolysis-Fenton-coagulation sedimentation-MBR combined process to treat solid waste leachate, offering significant technical advantages. The two-stage A / O system features strong resistance to influent shocks, thorough pollutant conversion, and low operating costs, effectively treating pollutants through biological nitrification and denitrification. In the microelectrolysis-Fenton-coagulation sedimentation system, ferrous ions generated by the electrodes can be directly used in the Fenton reaction, saving reagent usage and facilitating process control. Through the galvanic cell reaction of iron and carbon and the hydroxyl radicals generated by H2O2 catalysis, organic pollutants can be further oxidized and degraded, while simultaneously improving the biodegradability of the wastewater. Finally, an MBR membrane reactor is used as the advanced treatment unit, utilizing the metabolic activity of activated sludge and the filtration effect of the membrane module to ensure that the effluent quality meets the discharge requirements of the "Standard for Pollutant Control of Municipal Solid Waste Landfills" (GB16889-2008).

[0030] 2. This invention achieves tiered treatment and gradual degradation of pollutants in solid waste leachate through an innovative coupling of biochemical treatment and advanced oxidation processes. The entire process fully leverages the advantages of each treatment unit, resulting in significant treatment effects, stable and reliable operation, and low secondary pollution and operating costs. Process conditions are easy to control, the treatment units are rationally integrated, and operation and management are simple and feasible. It ensures both treatment effectiveness and good economic efficiency and practicality, providing a technologically advanced and economically feasible solution for solid waste leachate treatment, and possesses significant engineering application value. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some schematic diagrams of certain embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1The process flow diagram for combined treatment of solid waste leachate provided by the present invention is shown. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0034] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.

[0035] The leachate from a municipal solid waste landfill was analyzed, and its water quality characteristics are shown in Table 1. The leachate from this landfill is consistent with the characteristics of mid-to-late stage solid waste leachate.

[0036] Table 1. Water quality parameters of leachate from a landfill.

[0037]

[0038] Sludge from the secondary sedimentation tank of a municipal wastewater treatment plant was selected as inoculum sludge. The sludge concentration was 4500 mg / L, and the sludge showed good settling performance.

[0039] The leachate water had an imbalanced C / N ratio, with high TN content and relatively low COD content. A certain amount of carbon source needed to be added during the initial startup of the two-stage A / O system. In this example, glucose was added as a carbon source to achieve a B / C ratio of 0.3–0.5. Phosphorus was relatively deficient in the leachate, with TP content at 2–3 mg / L. Therefore, a certain amount of phosphate needed to be added during operation. In this example, KH₂PO₄ was added as a phosphorus source to achieve a C:N:P ratio of approximately 100–200:5:1.

[0040] A combined treatment process for solid waste leachate includes the following steps:

[0041] (1) The solid waste leachate is sent into the equalization tank for water quality optimization and water quantity adjustment to obtain pretreated leachate;

[0042] (2) The pretreated leachate was used as a substrate and aerated with sludge from the wastewater treatment plant. The two-stage A / O system was filled with tap water, and the dissolved oxygen in the two-stage A / O system was controlled at 2-6 mg / L. The pH in the two-stage A / O system was adjusted to 7-9. The initial ratio of pretreated leachate to tap water was 5:95. Subsequently, the proportion of pretreated leachate was gradually increased according to the ratios of 10:90, 20:80, 40:60, 60:40, 80:20, and 100:0. The reflux was increased to make the sludge settling ratio reach 60-80%. The aeration and cultivation time was 0.5-1.5 months to enable the two-stage A / O system to achieve a stable nitrification reaction.

[0043] (3) The pretreated leachate is sent to a two-stage A / O system, which includes a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank, and a second-stage aerobic tank connected in sequence. In the first-stage anoxic tank, the nitrate nitrogen in the returned mixed liquor interacts with the organic matter in the original sewage and is reduced by denitrifying bacteria. The effluent from the first-stage anoxic tank enters the first-stage aerobic tank, where the organic matter is oxidized and degraded, and the organic nitrogen is converted into nitrate nitrogen. Part of the effluent from the first-stage aerobic tank is returned to the first-stage anoxic tank, and part enters the second-stage anoxic tank. In the second-stage anoxic tank, the undegraded nitrate nitrogen is degraded by denitrifying bacteria through the addition of an external carbon source and endogenous respiration. The effluent from the second-stage anoxic tank enters the second-stage aerobic tank, where the organic matter is oxidized and degraded, and the organic nitrogen is converted into nitrate nitrogen. Part of the effluent from the second-stage aerobic tank is returned to the second-stage anoxic tank, and part is sent to the first sedimentation tank. Part of the sludge from the first sedimentation tank is returned to the first-stage anoxic tank, and part enters the sludge tank.

[0044] (4) The effluent from the first sedimentation tank is sent to the micro-electrolysis-Fenton-coagulation sedimentation system, which includes a micro-electrolysis reaction tank, a Fenton oxidation reaction tank, and a coagulation tank connected in sequence; the effluent from the first sedimentation tank is sent to the micro-electrolysis reaction tank, and acid (one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid) is added to adjust the pH to 2-4, and aeration reaction is carried out to decompose and degrade the organic matter in the leachate; the effluent from the micro-electrolysis reaction tank is sent to the Fenton oxidation reaction tank, and the packing material in the micro-electrolysis reaction tank is iron-carbon micro-electrolysis packing material TPFC (porosity 60-80%, iron-carbon ratio 2-6:1). The ratio of iron-carbon micro-electrolysis packing to wastewater is 200-400g:1L. Add 3-6wt% hydrogen peroxide solution, with a hydrogen peroxide solution to wastewater ratio of 1-6mL:1L. The reaction time is 60-300min. After the reaction, add alkali (one or more of lime milk, sodium hydroxide, and sodium carbonate) to adjust the pH to 8-9, and send it to a coagulation tank. Add 0.5-5mL / L of coagulant aid PAM for coagulation and sedimentation to separate the insoluble substances produced after advanced oxidation. The effluent from the coagulation tank is sent to a second sedimentation tank, and the sludge from the second sedimentation tank enters a sludge tank.

[0045] (5) Inject tap water into the MBR membrane reactor, then inoculate with the same sludge as the two-stage A / O system, controlling the sludge concentration at 2000-3000 mg / L. After the sludge is added, start aeration. When the sludge in the water changes from black to yellowish-brown, start continuous water intake, using a cultivation method that gradually increases the volumetric loading. On the 2nd and 4th days, pour the effluent from the second sedimentation tank, diluted by one-third and two-thirds respectively. From the 6th day of operation of the MBR membrane reactor, the influent volume is one-third of the design value, and continuous water intake is maintained. Gradually increase to the design value over 10-20 days. Monitor the sludge concentration daily to maintain the amount of activated sludge in the MBR membrane reactor at the optimal level. The volume ratio of the anoxic tank to the membrane reactor in the MBR membrane reactor is 1:2. The membrane fibers are made of polyvinylidene fluoride hollow fiber membrane with a pore size of 0.1 μm, a porosity of 40-50%, and an operating pressure of -0.1-0.03 MPa. The reflux ratio of the MBR membrane reactor is 100-300%.

[0046] The present invention will be further described below through specific embodiments.

[0047] Example 1

[0048] A combined treatment process for solid waste leachate includes the following steps:

[0049] (1) The solid waste leachate is sent into the equalization tank for water quality optimization and water quantity adjustment to obtain pretreated leachate;

[0050] (2) The pretreated leachate was used as a substrate and aerated with sludge from the wastewater treatment plant. The two-stage A / O system was filled with tap water, and the dissolved oxygen in the two-stage A / O system was controlled at 4 mg / L. The pH in the two-stage A / O system was adjusted to 8. The initial ratio of pretreated leachate to tap water was 5:95. Subsequently, the proportion of pretreated leachate was gradually increased according to the ratios of 10:90, 20:80, 40:60, 60:40, 80:20, and 100:0. The reflux was increased to make the sludge settling ratio reach 70%. The aeration and cultivation time was 1 month to enable the two-stage A / O system to achieve a stable nitrification reaction.

[0051] (3) The pretreated leachate is sent to a two-stage A / O system, which includes a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank, and a second-stage aerobic tank connected in sequence. In the first-stage anoxic tank, the nitrate nitrogen in the returned mixed liquor interacts with the organic matter in the original sewage and is reduced by denitrifying bacteria. The effluent from the first-stage anoxic tank enters the first-stage aerobic tank, where the organic matter is oxidized and degraded, and the organic nitrogen is converted into nitrate nitrogen. Part of the effluent from the first-stage aerobic tank is returned to the first-stage anoxic tank, and part enters the second-stage anoxic tank. In the second-stage anoxic tank, the undegraded nitrate nitrogen is degraded by denitrifying bacteria through the addition of an external carbon source and endogenous respiration. The effluent from the second-stage anoxic tank enters the second-stage aerobic tank, where the organic matter is oxidized and degraded, and the organic nitrogen is converted into nitrate nitrogen. Part of the effluent from the second-stage aerobic tank is returned to the second-stage anoxic tank, and part is sent to the first sedimentation tank. Part of the sludge from the first sedimentation tank is returned to the first-stage anoxic tank, and part enters the sludge tank.

[0052] (4) The effluent from the first sedimentation tank is sent to the micro-electrolysis-Fenton-coagulation sedimentation system, which includes a micro-electrolysis reaction tank, a Fenton oxidation reaction tank, and a coagulation tank connected in sequence; the effluent from the first sedimentation tank is sent to the micro-electrolysis reaction tank, hydrochloric acid is added to adjust the pH to 3, and aeration reaction is carried out to decompose and degrade the organic matter in the leachate; the effluent from the micro-electrolysis reaction tank is sent to the Fenton oxidation reaction tank, and the packing material in the micro-electrolysis reaction tank is iron-carbon micro-electrolysis packing material TPFC (porosity 70%, iron-carbon). The ratio of iron-carbon micro-electrolysis packing to wastewater is 4:1, the ratio of iron-carbon micro-electrolysis packing to wastewater is 360g:1L, 5wt% hydrogen peroxide solution is added, the ratio of hydrogen peroxide solution to wastewater is 4mL:1L, and the reaction time is 90min; after the reaction, lime milk is added to adjust the pH to 8, and the mixture is sent to the coagulation tank, where 2mL / L coagulant aid PAM is added for coagulation and sedimentation to separate the insoluble substances produced after advanced oxidation; the effluent from the coagulation tank is sent to the second sedimentation tank, and the sludge from the second sedimentation tank enters the sludge tank;

[0053] (5) Tap water is injected into the MBR membrane reactor, and then the same sludge as the two-stage A / O system is inoculated, controlling the sludge concentration at 2500 mg / L. After the sludge is added, aeration begins. When the sludge in the water changes from black to yellowish-brown, continuous water intake begins, using a gradual increase in volumetric loading. On the 2nd and 4th days, the effluent from the second sedimentation tank is diluted by one-third and two-thirds, respectively. From the 6th day of operation of the MBR membrane reactor, the influent volume is one-third of the design value, maintaining continuous influent. The influent volume is gradually increased to the design value over 15 days. The sludge concentration is monitored daily to maintain the amount of activated sludge in the MBR membrane reactor at its optimal level. The volume ratio of the anoxic tank to the membrane reactor in the MBR membrane reactor is 1:2. The membrane fibers are made of polyvinylidene fluoride hollow fiber membrane with a pore size of 0.1 μm, a porosity of 45%, and an operating pressure of -0.1 MPa. The reflux ratio of the MBR membrane reactor is 200%.

[0054] The operating results are shown in Table 2. After two-stage A / O-micro-electrolysis-Fenton-coagulation sedimentation-MBR process treatment, the effluent COD removal rate is 99.3%, BOD5 removal rate is 99.9%, and ammonia nitrogen removal rate is 99.9%. The effluent COD and ammonia nitrogen meet the emission standards of the "Standard for Pollutant Control of Municipal Solid Waste Landfill" (GB 16889-2008).

[0055] Table 2 Processing Results of Example 1

[0056]

[0057] Example 2

[0058] A combined treatment process for solid waste leachate includes the following steps:

[0059] (1) The solid waste leachate is sent into the equalization tank for water quality optimization and water quantity adjustment to obtain pretreated leachate;

[0060] (2) The pretreated leachate was used as a substrate and aerated with sludge from the wastewater treatment plant. The two-stage A / O system was filled with tap water, and the dissolved oxygen in the two-stage A / O system was controlled at 4 mg / L. The pH in the two-stage A / O system was adjusted to 8. The initial ratio of pretreated leachate to tap water was 5:95. Subsequently, the proportion of pretreated leachate was gradually increased according to the ratios of 10:90, 20:80, 40:60, 60:40, 80:20, and 100:0. The reflux was increased to make the sludge settling ratio reach 70%. The aeration and cultivation time was 1 month to enable the two-stage A / O system to achieve a stable nitrification reaction.

[0061] (3) The pretreated leachate is sent to a two-stage A / O system, which includes a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank, and a second-stage aerobic tank connected in sequence. In the first-stage anoxic tank, the nitrate nitrogen in the returned mixed liquor interacts with the organic matter in the original sewage and is reduced by denitrifying bacteria. The effluent from the first-stage anoxic tank enters the first-stage aerobic tank, where the organic matter is oxidized and degraded, and the organic nitrogen is converted into nitrate nitrogen. Part of the effluent from the first-stage aerobic tank is returned to the first-stage anoxic tank, and part enters the second-stage anoxic tank. In the second-stage anoxic tank, the undegraded nitrate nitrogen is degraded by denitrifying bacteria through the addition of an external carbon source and endogenous respiration. The effluent from the second-stage anoxic tank enters the second-stage aerobic tank, where the organic matter is oxidized and degraded, and the organic nitrogen is converted into nitrate nitrogen. Part of the effluent from the second-stage aerobic tank is returned to the second-stage anoxic tank, and part is sent to the first sedimentation tank. Part of the sludge from the first sedimentation tank is returned to the first-stage anoxic tank, and part enters the sludge tank.

[0062] (4) The effluent from the first sedimentation tank is sent to the micro-electrolysis-Fenton-coagulation sedimentation system, which includes a micro-electrolysis reaction tank, a Fenton oxidation reaction tank, and a coagulation tank connected in sequence; the effluent from the first sedimentation tank is sent to the micro-electrolysis reaction tank, hydrochloric acid is added to adjust the pH to 4, and aeration reaction is carried out to decompose and degrade the organic matter in the leachate; the effluent from the micro-electrolysis reaction tank is sent to the Fenton oxidation reaction tank, and the packing material in the micro-electrolysis reaction tank is iron-carbon micro-electrolysis packing material TPFC (porosity 70%, iron-carbon ratio 1.5%). The ratio of iron-carbon micro-electrolysis packing to wastewater is 300g:1L (5:1). 4wt% hydrogen peroxide solution is added, with a hydrogen peroxide solution to wastewater ratio of 3mL:1L. The reaction time is 150min. After the reaction, lime slurry is added to adjust the pH to 9, and the mixture is sent to a coagulation tank. 4mL / L of coagulant PAM is added for coagulation and sedimentation to separate insoluble substances produced after advanced oxidation. The effluent from the coagulation tank is sent to a second sedimentation tank, and the sludge from the second sedimentation tank enters a sludge tank.

[0063] (5) Tap water is injected into the MBR membrane reactor, and then the same sludge as the two-stage A / O system is inoculated, controlling the sludge concentration at 3000 mg / L. After the sludge is added, aeration begins. When the sludge in the water changes from black to yellowish-brown, continuous water intake begins, using a gradual increase in volumetric loading. On the 2nd and 4th days, the effluent from the second sedimentation tank is diluted by one-third and two-thirds, respectively. From the 6th day of operation of the MBR membrane reactor, the influent volume is one-third of the design value, maintaining continuous influent. The influent volume is gradually increased to the design value over 15 days. The sludge concentration is monitored daily to maintain the amount of activated sludge in the MBR membrane reactor at its optimal level. The volume ratio of the anoxic tank to the membrane reactor in the MBR membrane reactor is 1:2. The membrane fibers are made of polyvinylidene fluoride hollow fiber membrane with a pore size of 0.1 μm, a porosity of 50%, and an operating pressure of -0.1 MPa. The reflux ratio of the MBR membrane reactor is 300%.

[0064] The operating results are shown in Table 3. After two-stage A / O-micro-electrolysis-Fenton-coagulation sedimentation-MBR process treatment, the effluent COD removal rate is 99.0%, the BOD5 removal rate is 99.4%, and the ammonia nitrogen removal rate is 99.8%. The effluent COD and ammonia nitrogen meet the emission standards of the "Standard for Pollutant Control of Municipal Solid Waste Landfill" (GB 16889-2008).

[0065] Table 3. Processing Results of Example 2

[0066]

[0067] Comparative Example 1

[0068] A combined treatment process for solid waste leachate includes the following steps:

[0069] (1) The solid waste leachate is sent into the equalization tank for water quality optimization and water quantity adjustment to obtain pretreated leachate;

[0070] (2) The pretreated leachate was used as a substrate and aerated with sludge from the wastewater treatment plant. The two-stage A / O system was filled with tap water, and the dissolved oxygen in the two-stage A / O system was controlled at 4 mg / L. The pH in the two-stage A / O system was adjusted to 8. The initial ratio of pretreated leachate to tap water was 5:95. Subsequently, the proportion of pretreated leachate was gradually increased according to the ratios of 10:90, 20:80, 40:60, 60:40, 80:20, and 100:0. The reflux was increased to make the sludge settling ratio reach 70%. The aeration and cultivation time was 1 month to enable the two-stage A / O system to achieve a stable nitrification reaction.

[0071] (3) The pretreated leachate is sent to a two-stage A / O system, which includes a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank, and a second-stage aerobic tank connected in sequence. In the first-stage anoxic tank, the nitrate nitrogen in the returned mixed liquor interacts with the organic matter in the original sewage and is reduced by denitrifying bacteria. The effluent from the first-stage anoxic tank enters the first-stage aerobic tank, where the organic matter is oxidized and degraded, and the organic nitrogen is converted into nitrate nitrogen. Part of the effluent from the first-stage aerobic tank is returned to the first-stage anoxic tank, and part enters the second-stage anoxic tank. In the second-stage anoxic tank, the undegraded nitrate nitrogen is degraded by denitrifying bacteria through the addition of an external carbon source and endogenous respiration. The effluent from the second-stage anoxic tank enters the second-stage aerobic tank, where the organic matter is oxidized and degraded, and the organic nitrogen is converted into nitrate nitrogen. Part of the effluent from the second-stage aerobic tank is returned to the second-stage anoxic tank, and part is sent to the first sedimentation tank. Part of the sludge from the first sedimentation tank is returned to the first-stage anoxic tank, and part enters the sludge tank.

[0072] (4) The effluent from the first sedimentation tank is sent to the micro-electrolysis-Fenton-coagulation sedimentation system, which includes a micro-electrolysis reaction tank, a Fenton oxidation reaction tank, and a coagulation tank connected in sequence; the effluent from the first sedimentation tank is sent to the micro-electrolysis reaction tank, hydrochloric acid is added to adjust the pH to 3, and aeration reaction is carried out to decompose and degrade the organic matter in the leachate; the effluent from the micro-electrolysis reaction tank is sent to the Fenton oxidation reaction tank, and the packing material in the micro-electrolysis reaction tank is iron-carbon micro-electrolysis packing material TPFC (porosity 70%, iron-carbon). The ratio of iron-carbon micro-electrolysis packing to wastewater is 4:1, the ratio of iron-carbon micro-electrolysis packing to wastewater is 360g:1L, 5wt% hydrogen peroxide solution is added, the ratio of hydrogen peroxide solution to wastewater is 4mL:1L, and the reaction time is 90min; after the reaction, lime milk is added to adjust the pH to 8, and the mixture is sent to the coagulation tank, where 2mL / L coagulant aid PAM is added for coagulation and sedimentation to separate the insoluble substances produced after advanced oxidation; the effluent from the coagulation tank is sent to the second sedimentation tank, and the sludge from the second sedimentation tank enters the sludge tank;

[0073] The operating results are shown in Table 4. After two-stage A / O-micro-electrolysis-Fenton-coagulation sedimentation process, the effluent COD removal rate was 95.7%, the BOD5 removal rate was 93.9%, and the ammonia nitrogen removal rate was 97.3%. The effluent COD, BOD5, and ammonia nitrogen did not meet the emission standards of the "Standard for Pollutant Control of Municipal Solid Waste Landfill" (GB 16889-2008).

[0074] Table 4. Results of the treatment in Comparative Example 1

[0075]

[0076] Comparative Example 2

[0077] A combined treatment process for solid waste leachate includes the following steps:

[0078] (1) The solid waste leachate is sent into the equalization tank for water quality optimization and water quantity adjustment to obtain pretreated leachate;

[0079] (2) The pretreated leachate was used as a substrate and aerated with sludge from the wastewater treatment plant. The two-stage A / O system was filled with tap water, and the dissolved oxygen in the two-stage A / O system was controlled at 4 mg / L. The pH in the two-stage A / O system was adjusted to 8. The initial ratio of pretreated leachate to tap water was 5:95. Subsequently, the proportion of pretreated leachate was gradually increased according to the ratios of 10:90, 20:80, 40:60, 60:40, 80:20, and 100:0. The reflux was increased to make the sludge settling ratio reach 70%. The aeration and cultivation time was 1 month to enable the two-stage A / O system to achieve a stable nitrification reaction.

[0080] (3) The pretreated leachate is sent to a two-stage A / O system, which includes a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank, and a second-stage aerobic tank connected in sequence. In the first-stage anoxic tank, the nitrate nitrogen in the returned mixed liquor interacts with the organic matter in the original sewage and is reduced by denitrifying bacteria. The effluent from the first-stage anoxic tank enters the first-stage aerobic tank, where the organic matter is oxidized and degraded, and the organic nitrogen is converted into nitrate nitrogen. Part of the effluent from the first-stage aerobic tank is returned to the first-stage anoxic tank, and part enters the second-stage anoxic tank. In the second-stage anoxic tank, the undegraded nitrate nitrogen is degraded by denitrifying bacteria through the addition of an external carbon source and endogenous respiration. The effluent from the second-stage anoxic tank enters the second-stage aerobic tank, where the organic matter is oxidized and degraded, and the organic nitrogen is converted into nitrate nitrogen. Part of the effluent from the second-stage aerobic tank is returned to the second-stage anoxic tank, and part is sent to the first sedimentation tank. Part of the sludge from the first sedimentation tank is returned to the first-stage anoxic tank, and part enters the sludge tank.

[0081] The operating results are shown in Table 5. After two-stage A / O process treatment, the effluent COD removal rate was 80.0%, the BOD5 removal rate was 87.0%, and the ammonia nitrogen removal rate was 96.8%. The effluent COD, BOD5, and ammonia nitrogen did not meet the emission standards of the "Standard for Pollutant Control of Municipal Solid Waste Landfill" (GB 16889-2008).

[0082] Table 5. Results of the treatment in Comparative Example 2

[0083]

[0084] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A combined treatment process for solid waste leachate, characterized in that, Includes the following steps: (1) The solid waste leachate is sent into the equalization tank for water quality optimization and water quantity adjustment to obtain pretreated leachate; (2) The pretreated leachate is sent to a two-stage A / O system to remove high concentrations of ammonia nitrogen and most of the organic matter, and then sent to the first sedimentation tank. (3) The effluent from the first sedimentation tank is sent into the micro-electrolysis-Fenton-coagulation sedimentation system to reduce COD and improve biodegradability, and then sent into the second sedimentation tank. (4) The effluent from the second sedimentation tank is sent into the MBR membrane reactor to completely decompose the organic matter in the wastewater into CO2 and H2O.

2. The combined treatment process for solid waste leachate according to claim 1, characterized in that, In step (2), the two-stage A / O system includes a first-stage anoxic tank, a first-stage aerobic tank, a second-stage anoxic tank, and a second-stage aerobic tank connected in sequence; in the first-stage anoxic tank, the nitrate nitrogen in the reflux mixed liquor interacts with the organic matter in the original sewage and is reduced by denitrifying bacteria; The effluent from the first-stage anoxic tank enters the first-stage aerobic tank, where organic matter is oxidized and degraded, and organic nitrogen is converted into nitrate nitrogen. A portion of the effluent from the primary aerobic tank is returned to the primary anoxic tank, while another portion enters the secondary anoxic tank. In the secondary anoxic tank, undegraded nitrate nitrogen is degraded by denitrifying bacteria through the addition of an external carbon source and endogenous respiration. The effluent from the secondary anoxic tank enters the secondary aerobic tank, where organic matter is oxidized and degraded, converting organic nitrogen into nitrate nitrogen. Part of the effluent from the secondary aerobic tank is returned to the secondary anoxic tank, and part is sent to the primary sedimentation tank.

3. The combined treatment process for solid waste leachate according to claim 2, characterized in that, Part of the sludge from the first sedimentation tank is returned to the primary anoxic tank, and part enters the sludge tank.

4. The combined treatment process for solid waste leachate according to claim 1, characterized in that, In step (3), the micro-electrolysis-Fenton-coagulation sedimentation system includes a micro-electrolysis reaction tank, a Fenton oxidation reaction tank, and a coagulation tank connected in sequence. The effluent from the first sedimentation tank is sent to the micro-electrolysis reaction tank, acid is added to adjust the pH to 2-4, and aeration reaction is carried out to decompose and degrade the organic matter in the leachate. The effluent from the micro-electrolysis reaction tank is sent to the Fenton oxidation reaction tank, hydrogen peroxide solution is added, and after the reaction is completed, alkali is added to adjust the pH to 8-9, and the effluent is sent to the coagulation tank. A coagulant aid is added to carry out coagulation and sedimentation to separate the insoluble substances produced after advanced oxidation.

5. The combined treatment process for solid waste leachate according to claim 4, characterized in that, The effluent from the coagulation tank is sent to the second sedimentation tank, and the sludge from the second sedimentation tank enters the sludge tank.

6. The combined treatment process for solid waste leachate according to claim 4, characterized in that, The acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid; the base is one or more of lime milk, sodium hydroxide, and sodium carbonate.

7. The combined treatment process for solid waste leachate according to claim 4, characterized in that, The packing material in the micro-electrolysis reactor is TPFC (iron-carbon micro-electrolysis packing), with a porosity of 60-80% and an iron-carbon ratio of 2-6:1; the ratio of TPFC packing to wastewater is 200-400 g: 1 L.

8. The combined treatment process for solid waste leachate according to claim 4, characterized in that, The concentration of hydrogen peroxide solution is 3-6 wt%, and the ratio of hydrogen peroxide solution to wastewater is 1-6 mL:1 L; the reaction time is 60-300 min; the coagulant is PAM, and the ratio of PAM to wastewater is 0.5-5 mL:1 L.

9. The combined treatment process for solid waste leachate according to claim 1, characterized in that, In step (4), the volume ratio of the anoxic tank to the membrane reactor in the MBR membrane reactor is 1:

2. The membrane filaments are made of polyvinylidene fluoride hollow fiber membrane with a pore size of 0.1 μm, a porosity of 40-50%, and a working pressure of -0.1 to 0.03 MPa.

10. The combined treatment process for solid waste leachate according to claim 9, characterized in that, The reflux ratio of the MBR membrane reactor is 100-300%; the sludge concentration in the MBR membrane reactor is 2000-3000 mg / L.

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