A method and system for resource processing of landfill leachate

Abstract

The present invention provides a method and system for resource-based treatment of landfill leachate. S1: Treating the landfill leachate to obtain sludge and liquid. S2: The liquid obtained in step S1 is placed in an organic matter storage tank, the sludge obtained in step S1 is processed, and the liquid in the organic matter storage tank can be used as a sodium acetate carbon source in sewage treatment. The present invention has the beneficial effect of: the supernatant obtained after leachate resource treatment contains rich organic matter and can replace the commercial sodium acetate carbon source added in some sewage treatment plants, achieving energy conservation, consumption reduction, cost reduction, and efficiency improvement in sewage treatment.

Description

Technical Field

[0001] The present invention belongs to the field of sewage treatment, and in particular relates to a method and system for resource treatment of landfill leachate. Background Art

[0002] During the operation of garbage incineration plants and garbage transfer stations, a certain amount of garbage leachate is generated. The leachate contains not only a large amount of dissolved organic matter (total organic carbon, volatile fatty acids and humus, etc.), but also high concentrations of ammonia nitrogen, inorganic components (such as Ca 2+ Mg 2+ NH4 + 、Fe 2+ 、Mn 2+ 、Cl - ), heavy metal ions (such as As, Hg, Cd, Cr, Cu, Pb) and other toxic and harmful substances, making the traditional activated sludge treatment process difficult to apply to leachate.

[0003] Taking the treatment of 100 tons of leachate per day as an example, to meet the emission standards, the design investment per ton is between 100,000 and 200,000 yuan, and the total investment is between 10 million and 20 million yuan. The operating fee per ton is between 50 and 100 (different processes and water quality). The basic construction fee of a 1,000-ton leachate treatment station needs to cost over 100 million yuan, and the annual operating fee can reach 30 million yuan. Therefore, the cost of leachate treatment is unaffordable for general enterprises.

[0004] On the other hand, the low COD concentration of the influent of urban sewage treatment plants has become a "stumbling block" for improving the quality and efficiency of sewage treatment. Since the main process of sewage treatment plants is the activated sludge method, it is necessary to rely on the biochemical reactions of microorganisms in the activated sludge to treat sewage. If the influent COD concentration is too low, it will lead to insufficient nutrition for the microorganisms and they will not be able to maintain relatively good activity. In order to ensure that the nitrogen and phosphorus problems meet the standards, sewage treatment plants often excessively add large amounts of chemical agents, such as adding large amounts of purchased carbon to reduce total nitrogen, and adding large amounts of inorganic coagulants to reduce total phosphorus. Some sewage treatment plants also directly add flocculants to the secondary sedimentation tank to control sludge loss. The chemical costs of many sewage treatment plants have actually exceeded electricity bills to become the largest expense, making operations unsustainable.

[0005] Therefore, from the perspective of resource recovery, combined leachate and municipal sewage treatment can significantly reduce treatment costs by eliminating the high expense of constructing a separate leachate treatment system. It also utilizes the high concentration of organic matter in leachate, reducing the amount of carbon source added during municipal sewage treatment. However, due to the complex and unstable quality of leachate and the presence of various inhibitors to activated sludge in municipal sewage treatment plants, which can easily lead to adverse symptoms such as activated sludge poisoning, direct combined leachate treatment significantly increases the pollutant load of the sewage, deteriorating water quality and exceeding the treatment capacity of the sewage treatment plant. It may also interfere with the normal biological treatment processes of municipal sewage treatment plants. For example, high concentrations of ammonia nitrogen can inhibit microorganisms, affecting biological denitrification, while heavy metals can be toxic to microorganisms, reducing biological activity. Certain components in leachate, such as acidic substances, may accelerate corrosion of sewage pipes, shortening their service life, increasing maintenance costs, and posing a potential risk of leaks. Summary of the Invention

[0006] In view of this, the present invention aims to provide a method and system for resource recovery treatment of landfill leachate to solve at least one technical problem in the background technology.

[0007] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0008] A method for recycling landfill leachate comprises the following steps:

[0009] S1: Treat the landfill leachate to obtain sludge and liquid;

[0010] S2: The liquid obtained in step S1 enters the organic matter storage tank, and the sludge obtained in step S1 is processed. The liquid in the organic matter storage tank can be used as a sodium acetate carbon source for sewage treatment;

[0011] The treatment of the landfill leachate in step S1 includes the landfill leachate sequentially entering a dephosphorization unit, a conventional heavy metal removal unit, a special heavy metal removal unit, a coprecipitation unit, and a solid-liquid separation unit;

[0012] The sludge in step S2 is processed through a sludge dewatering unit:

[0013] The liquid obtained from the solid-liquid separation unit is treated in the nitrogen removal unit and then enters the organic matter storage tank. Part of the sludge obtained after the solid-liquid separation treatment is recycled back to the dephosphorization unit, and the other part of the sludge obtained after the solid-liquid separation treatment enters the sludge dewatering unit. The filtrate of the sludge dewatering unit is treated in the phosphorus removal unit and then enters the organic matter storage tank.

[0014] or the treatment of the landfill leachate in step S1 includes the landfill leachate sequentially entering a filtration unit, an electro-flocculation-chemical flocculation combination unit, and a separation unit;

[0015] The sludge in step S2 is processed through a sludge thickening unit;

[0016] The supernatant obtained from the separation unit is then processed in the electric adsorption unit and the membrane concentration unit before entering the organic matter storage tank;

[0017] The settled sludge obtained from the separation unit enters the membrane concentration unit of the sludge concentration unit, and the filtrate obtained from the sludge concentration unit enters the organic matter storage tank.

[0018] Furthermore, a first agent is added to the dephosphorization unit in step S1, and the first agent is one or both of calcium oxide and calcium hydroxide;

[0019] Alternatively, the first agent is added in an amount of 5-10 g / L, the pH value in the dephosphorization unit of step S1 is adjusted to 9-10, and the hydraulic retention time in the dephosphorization unit is 10-20 minutes. Calcium ions react with phosphate to form insoluble calcium phosphate precipitates (such as hydroxyapatite). Calcium ions can also be adsorbed on the surface of the returned sludge particles, enhancing the sludge particles' ability to adsorb phosphorus, thereby removing phosphorus from the water.

[0020] Furthermore, a second agent is added to the conventional heavy metal removal unit of step S1, and the second agent is one or both of sodium hydroxide and potassium hydroxide; the addition of alkali will increase the pH value of the solution. At a higher pH value, the existence form of many conventional heavy metals changes (such as copper ions, zinc ions, and cadmium ions), and the solubility of the hydroxides of these heavy metals is very low, thereby forming hydroxide precipitates in the solution.

[0021] and / or, the amount of the second agent added is 1-4 g / L, the pH value in the conventional heavy metal removal unit is adjusted to 11-12, and the hydraulic retention time in the conventional heavy metal removal unit is 10-20 min;

[0022] And / or, a third agent is added to the special heavy metal removal unit in step S1, and the third agent is one or both of green vitriol and siderite;

[0023] The third agent, green vitriol (FeSO₄·7H₂O) and siderite, contains ferrous ions, added at a rate of 1–2 g / L. The addition of ferrous ions can remove some heavy metals that are difficult to precipitate as hydroxides. For example, ferrous ions can reduce hexavalent chromium to trivalent chromium, making it easier to precipitate chromium hydroxide. Ferrous ions can also react with mercury ions to form insoluble mercury compound precipitates. Ferrous ions can react with arsenic in the solution to form ferrous minerals (such as ferrous arsenate), which have extremely low solubility and belong to the extremely stable violaceous iron family, making them difficult to redissolve.

[0024] And / or, a fourth agent is added to the coprecipitation unit in step S1, and the fourth agent is one or more of hematite, ferric chloride, ferric nitrate, ferric sulfate, and magnetite;

[0025] And / or, the fourth agent is added in an amount of 4-8 g / L. Trivalent iron ions undergo hydrolysis in the solution to form a series of hydroxyl complexes. These complexes are positively charged and can neutralize negatively charged colloidal particles in the water, causing them to lose stability. Furthermore, these complexes have a large specific surface area and adsorption activity, allowing them to adsorb multiple colloidal particles, forming bridges between the colloidal particles and promoting particle aggregation. This can precipitate small suspended particles in the solution, precipitate heavy metal hydroxides, and aggregate insoluble components into larger flocs, resulting in a co-precipitation effect.

[0026] Furthermore, the solid-liquid separation unit of step S1 is an inclined plate sedimentation tank; since the specific gravity of iron salts is relatively large and the solution contains calcium ions that are prone to scaling, the use of an inclined plate sedimentation tank is more efficient.

[0027] And / or, the inclined plate spacing of the inclined plate sedimentation tank is 70-100 mm, and the inclined plate inclination angle is 55°-65°;

[0028] And / or, the inclined plate sedimentation tank is provided with a clear water area, a buffer area, and a sedimentation area from top to bottom; the length ratio of the clear water area, the buffer area, and the sedimentation area is 15:15:70,

[0029] And / or, the hydraulic retention time of the solid-liquid separation unit is 60-120 min, the surface load intensity of the solid-liquid separation unit is 0.8-1.2 m³ / (h·㎡), and the flow rate of the solid-liquid separation unit is 0.2-0.3 mm / s.

[0030] Furthermore, an aeration device is provided at the bottom of the nitrogen removal unit in step S1, the gas-water ratio of the nitrogen removal unit is 15-20:1, the aeration intensity of the nitrogen removal unit is 2-4 cubic meters / square meter·hour, and the hydraulic retention time of the nitrogen removal unit is 2-3 hours; since the alkalinity of the solution is relatively high at this time, most of the ammonia in the solution can be removed by aeration.

[0031] Alternatively, the sludge dewatering unit is a screw press dewatering machine having a power of 1-5 kWh, a screw shaft speed of 2-5 rpm, and a filter slot width of 0.5-2 mm. The filtrate after filtration enters the nitrogen removal unit, and the filter residue from the sludge dewatering unit is treated in a sludge treatment device. The filter residue has a moisture content of 75%-85% and is centrally treated.

[0032] Furthermore, the filtration unit in step S1 is a basket filter with a filtration accuracy of 2 mm and made of stainless steel. The purpose of the filtration unit is to prevent large particles of coarse fiber from interfering with the subsequent electro-flocculation process.

[0033] And / or, the electric flocculation-chemical flocculation combination unit includes a flocculation tank, an electrode plate assembly, and an agitator, and the electrode plate assembly and the agitator are sequentially arranged in the flocculation tank from top to bottom.

[0034] And / or, the plate assembly includes an anode plate and a cathode plate, the anode plate and the cathode plate are arranged alternately, and a flocculation filling particle assembly is provided between the anode plate and the cathode plate; the anode plate and the cathode plate are both iron plates, and the current density of the anode plate and the cathode plate is 50~150 A / m 2 The distance between the anode plate and the cathode plate is 3 cm to 5 cm, and the hydraulic retention time of the electrocoagulation-chemical flocculation combined unit is 60 to 90 min.

[0035] The anode and cathode plates are made of the same material. To improve electrode utilization efficiency, the electrocoagulation voltage is periodically reversed. This electrode reversal exploits the polarization phenomenon of the electrodes. During the electrocoagulation process, the anode gradually dissolves, producing metal ions, while the cathode undergoes a reduction reaction, producing hydrogen or other reduction products. Over time, the anode's dissolution rate gradually accelerates, while the reduction products at the cathode gradually accumulate, leading to a decline in electrode performance. By periodically reversing the electrodes, the anode and cathode roles are reversed, slowing the anode's dissolution rate and promptly removing the reduction products at the cathode. This effectively extends the electrode's lifespan and improves its utilization efficiency. Furthermore, electrode reversal enhances the electrocoagulation process. During electrode reversal, deposits on the electrode surface are removed, restoring the electrode's surface area and increasing its reactivity. Furthermore, electrode reversal changes the electric field distribution on the electrode surface, promoting pollutant flocculation and precipitation, thereby enhancing the electrocoagulation process.

[0036] And / or, the flocculating filling particle assembly includes flocculating filling particles and a fiber woven mesh bag; a plurality of flocculating filling particles are arranged in the fiber woven mesh bag;

[0037] And / or, the flocculating filler particles are one or two or more of sodium carbonate, calcium oxide, sodium hydroxide, and calcium hydroxide;

[0038] And / or, the fiber woven mesh bag is provided with holes, and the diameter of the holes is 0.5-0.8 cm;

[0039] And / or, the stirring speed of the stirrer is 100-150 rpm, and the stirrer is made of stainless steel.

[0040] The purpose of the combined electro-flocculation and chemical flocculation unit is to convert the iron in the iron plate into ferrous and ferric ions when powered. The filler particles undergo dissolution and hydrolysis reactions, producing large amounts of hydroxide. These ions form ferric hydroxide and ferrous hydroxide precipitates. The resulting iron hydroxide has a flocculating effect, adsorbing, encapsulating, and reacting with large amounts of suspended matter, heavy metals, and other substances to form co-precipitates, thereby separating them from the solution and forming precipitation, reducing the content of harmful substances in the water and achieving the goal of purifying water quality. The larger size of the flocculating particles allows for their slow release into the solution, compensating for the slow reaction rate caused by the low hydroxide concentration in electro-flocculation. Furthermore, the mass force and adsorption of the flocculating particles promote hydroxide flocculation, and the high-density inorganic mineral skeleton effectively promotes the settling of the flocs. The role of stirring is to promote the faster transfer of pollutants in the water to the electrodes, and also to promote the removal of reaction products from the electrode surface, thereby improving the efficiency of electroflocculation; preventing flocculants and filling particles from precipitating and accumulating at the bottom of the container or on the surface of the electrode, thereby improving the utilization rate of reactants; the electroflocculation and filling particle reaction process generates a certain amount of heat, and stirring can promote the transfer and diffusion of heat, making the system temperature more stable.

[0041] Furthermore, the separation unit of step S1 is a vertical flow sedimentation tank;

[0042] The effective water depth of the vertical flow sedimentation tank is 3~4 m, the flow rate of the water inlet pipe of the vertical flow sedimentation tank is 0.15 m~0.3 m / s, the flow rate of the water outlet pipe of the vertical flow sedimentation tank is 0.2 m~0.4 m / s, the gap height between the central pipe bell mouth and the reflector of the vertical flow sedimentation tank is 0.25 m~0.5 m, the rising flow rate of the vertical flow sedimentation tank is 0.5~1 mm / s, the sedimentation time of the vertical flow sedimentation tank is 1.5~2.0 h, the sludge hopper inclination angle of the vertical flow sedimentation tank is 55°~60°, and the surface load of the vertical flow sedimentation tank is 1.5~3.0 m 3 / (m 2 h). Vertical flow sedimentation tanks occupy a smaller footprint, facilitate sludge discharge, and offer superior hydraulic conditions. Solution flows into the tank through the center pipe and upwards, while settled sludge collects at the center of the tank bottom and is discharged through the sludge discharge pipe. The direction of water flow aligns with the direction of particle settling, minimizing disturbance of the precipitating particles.

[0043] Furthermore, the electrosorption unit of step S1 uses one of membrane electrosorption or flow electrosorption modes, and the electrode material of the electrosorption unit of step S1 is an activated carbon-based electrode material; the membrane material uses AEM or PEM ion exchange membrane.

[0044] Alternatively, the electrosorption unit has a plate voltage of 1.5-3 V, a plate spacing of 0.5-1 cm, and a hydraulic retention time of 10-30 minutes. A dual-module continuous flow operation mode is employed, with one module performing adsorption while the other performs desorption. The electrosorption unit can effectively remove various salts from water, including sodium, chloride, calcium, magnesium, and ammonium ions. By applying an electric field across the electrodes, ions in the water migrate toward the oppositely charged electrodes and are adsorbed, significantly reducing the salt and ammonia nitrogen concentrations in the solution.

[0045] And / or, the membrane concentration unit uses a nanofiltration membrane for concentration, the material of the nanofiltration membrane is one or more of cellulose acetate, sulfonated polysulfone or polyamide, the pore size of the nanofiltration membrane concentration is 5-10 nm, and the membrane flux of the nanofiltration membrane concentration is 10-30 L / (m 2 ·h), the operating pressure of nanofiltration membrane concentration is 1~5 MPa, the feed flow rate of nanofiltration membrane concentration is 1~5 m / s, the retention rate of nanofiltration membrane concentration is 80%~90%, and the concentration multiple is 4~6 times.

[0046] And / or, the sludge concentration unit is an elliptical sludge dewatering machine with a processing capacity of 1~5 m 3 / h, the solid load of the elliptical stack sludge dewatering machine is 25~60 kgDS / h, the moisture content of the sludge after dehydration is 75%~85%, the speed of the elliptical stack sludge dewatering machine is 50~150 rpm, the mud inlet pressure of the elliptical stack sludge dewatering machine is 0.1~0.5 MPa, and the back pressure of the elliptical stack sludge dewatering machine is 0.05~0.2 MPa; the filter residue of the sludge dewatering unit is treated in the sludge treatment device. The elliptical stack sludge dewatering machine has good solid-liquid separation effect and can maintain stable processing capacity. It will not cause the processing capacity to decrease due to blockage like other filtration type dewatering machines; and the energy consumption is very low, no high-power drive components are required, and there is no metal contact design, which reduces the possibility of equipment failure due to wear and tear, and can operate continuously for 24 hours.

[0047] A system for treating landfill leachate as a resource, comprising a phosphorus removal unit, a conventional heavy metal removal unit, a special heavy metal removal unit, a co-precipitation unit, a solid-liquid separation unit, a nitrogen removal unit, and an organic matter storage tank;

[0048] The phosphorus removal unit, the conventional heavy metal removal unit, the special heavy metal removal unit, the co-precipitation unit, and the solid-liquid separation unit are sequentially connected through pipelines;

[0049] The solid-liquid separation unit is connected to the nitrogen removal unit through a pipeline, the solid-liquid separation unit is connected to the sludge dewatering unit through a pipeline, the sludge dewatering unit is connected to the sludge treatment device through a pipeline, the sludge dewatering unit is connected to the nitrogen removal unit through a pipeline, and the nitrogen removal unit is connected to the organic matter storage tank through a pipeline;

[0050] And / or, the phosphorus removal unit is provided with a first reagent inlet pipeline;

[0051] And / or, the conventional heavy metal removal unit is provided with a second reagent inlet pipeline;

[0052] And / or, the special heavy metal removal unit is provided with a third reagent inlet pipeline;

[0053] And / or, the co-precipitation unit is provided with a fourth reagent inlet pipeline;

[0054] and / or, the coprecipitation unit is connected to the special heavy metal removal unit via a solution reflux pipe;

[0055] And / or, the solid-liquid separation unit is connected to the phosphorus removal unit through a sludge return pipe.

[0056] The sludge return ratio of the sludge return pipe of the present application is 10%~20%, and the return sludge concentration is 30,000~40,000 mg / L; sludge return can improve the sedimentation performance of flocs, and the granular matter in the return sludge can act as a skeleton, effectively promoting the sedimentation of flocs such as heavy metal hydroxides and suspended matter. At the same time, due to the low solubility of calcium oxide, the sludge contains some unreacted calcium oxide, and sludge return can increase the utilization efficiency of calcium oxide.

[0057] The solution reflux ratio of the solution reflux pipeline of the present application is 50%~80%, and the sludge concentration of the reflux solution is 10000~20000 mg / L; the solution reflux can enhance the flocculation efficiency and utilization rate of the iron salt, increase the flocculation co-precipitation reaction time, promote the growth of co-precipitation particles to form larger particles, and the co-precipitation material contains a larger surface area, which can adsorb small particle precipitation materials.

[0058] A system for treating landfill leachate as a resource, comprising a filtration unit, an electro-flocculation-chemical flocculation combination unit, a separation unit, an electro-adsorption unit, a membrane concentration unit, an organic matter storage tank, a sludge concentration unit, and a sludge treatment device;

[0059] The filtration unit, the electric flocculation-chemical flocculation combination unit, the separation unit, the electric adsorption unit, and the membrane concentration unit are sequentially connected through pipelines;

[0060] The separation unit is connected to the sludge concentration unit through a pipeline, and the membrane concentration unit is connected to the organic matter storage tank through a pipeline; the sludge concentration unit is connected to the sludge treatment device through a pipeline; the sludge concentration unit is connected to the sludge treatment device through a pipeline, and the sludge concentration unit is connected to the organic matter storage tank through a pipeline.

[0061] Compared with the existing technology, the method and system for resource recovery of landfill leachate described in the present invention have the following advantages:

[0062] 1. The organic matter content in the leachate of this application is almost completely retained, and the COD removal rate is less than 8%.

[0063] 2. The removal rate of toxic and harmful substances in this application is relatively high, and the removal rates of SS, TP, major heavy metals, chroma, etc. are all over 80%.

[0064] 3. The construction and operation costs of this application are extremely low. The investment and construction cost is only one-fifth of the harmless treatment of leachate, and the operation cost is only one-half of it, thus getting rid of the dilemma of extremely high cost of leachate treatment.

[0065] 4. The supernatant obtained after the resource utilization treatment of the leachate in this application contains rich organic matter, which can replace the commercial sodium acetate carbon source added in some sewage treatment plants, thereby achieving energy saving, consumption reduction, cost reduction and efficiency improvement in sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0067] Figure 1 This is a schematic flow chart of a method for recycling landfill leachate according to Example 1 of the present invention;

[0068] Figure 2 This is a schematic flow chart of a method for recycling landfill leachate according to Example 2 of the present invention;

[0069] Figure 3 This is a schematic diagram of a flocculation filling particle assembly of a method for resource recovery of landfill leachate described in Example 2 of the present invention.

[0070] Description of reference numerals:

[0071] 1. Anode plate; 2. Cathode plate; 3. Flocculation filling particle assembly; 4. Agitator. DETAILED DESCRIPTION

[0072] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0073] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0074] Example 1

[0075] like Figure 1 As shown, a method for resource recovery of landfill leachate comprises the following steps: S1: treating the landfill leachate to obtain sludge and liquid; S2: the liquid obtained in step S1 enters an organic matter storage tank, the sludge obtained in step S1 is processed, and the liquid in the organic matter storage tank can be used as a sodium acetate carbon source for sewage treatment;

[0076] The treatment of the landfill leachate in step S1 includes the landfill leachate sequentially entering a dephosphorization unit, a conventional heavy metal removal unit, a special heavy metal removal unit, a co-precipitation unit, and a solid-liquid separation unit; the sludge in step S2 is processed by a sludge dewatering unit: the liquid obtained in the solid-liquid separation unit is treated in a nitrogen removal unit and then enters an organic matter storage tank, a part of the sludge obtained after the solid-liquid separation treatment is recycled back to the dephosphorization unit, and another part of the sludge obtained after the solid-liquid separation treatment enters a sludge dewatering unit, and the filtrate of the sludge dewatering unit is treated in a phosphorus removal unit and then enters an organic matter storage tank.

[0077] In step S1, a first agent is added to the dephosphorization unit. The first agent is one or both of calcium oxide and calcium hydroxide. The first agent is added in an amount of 5-10 g / L. The pH value in the dephosphorization unit is adjusted to 9-10. The hydraulic retention time in the dephosphorization unit is 10-20 minutes. A second agent is added to the conventional heavy metal removal unit in step S1. The second agent is one or both of sodium hydroxide and potassium hydroxide.

[0078] The amount of the second agent added is 1-4 g / L, the pH value in the conventional heavy metal removal unit is adjusted to 11-12, and the hydraulic retention time in the conventional heavy metal removal unit is 10-20 minutes; the third agent is added to the special heavy metal removal unit in step S1, and the third agent is one or both of green vitriol and siderite; the amount of the third agent added is 1-2 g / L;

[0079] A fourth agent is added to the coprecipitation unit in step S1. The fourth agent is one or more of hematite, ferric chloride, ferric nitrate, ferric sulfate, and magnetite. The amount of the fourth agent added is 4-8 g / L.

[0080] The solid-liquid separation unit of step S1 is an inclined plate sedimentation tank; the inclined plate spacing of the inclined plate sedimentation tank is 70-100 mm, and the inclined plate inclination angle is 55°-65°; the inclined plate sedimentation tank is provided with a clear water area, a buffer area, and a sedimentation area from top to bottom; the length ratio of the clear water area, the buffer area, and the sedimentation area is 15:15:70,

[0081] The hydraulic retention time of the solid-liquid separation unit is 60~120 min, the surface load intensity of the solid-liquid separation unit is 0.8~1.2 m³ / (h·㎡), and the flow rate of the solid-liquid separation unit is 0.2~0.3 mm / s.

[0082] The bottom of the nitrogen removal unit in step S1 is provided with an aeration device, the air-water ratio of the nitrogen removal unit is 15:1-20:1, the aeration intensity of the nitrogen removal unit is 2-4 cubic meters / square meter·hour, and the hydraulic retention time of the nitrogen removal unit is 2-3 hours;

[0083] The sludge dewatering unit is a screw press dewatering machine, the power of the screw press dewatering machine is 1~5 kWh, the screw shaft speed of the screw press dewatering machine is 2~5 revolutions per minute, and the filter seam width of the screw press dewatering machine is 0.5~2 mm.

[0084] A system for a landfill leachate resource treatment method includes a phosphorus removal unit, a conventional heavy metal removal unit, a special heavy metal removal unit, a coprecipitation unit, a solid-liquid separation unit, a nitrogen removal unit, and an organic matter storage tank; the phosphorus removal unit, the conventional heavy metal removal unit, the special heavy metal removal unit, the coprecipitation unit, and the solid-liquid separation unit are sequentially connected via pipelines; the solid-liquid separation unit and the nitrogen removal unit are connected via pipelines, the solid-liquid separation unit is connected via pipelines to a sludge dewatering unit, the sludge dewatering unit is connected via pipelines to a sludge treatment device, the sludge dewatering unit is connected via pipelines to the nitrogen removal unit, and the nitrogen removal unit is connected via pipelines to the organic matter storage tank;

[0085] The phosphorus removal unit is provided with a first reagent inlet pipeline; the conventional heavy metal removal unit is provided with a second reagent inlet pipeline; the special heavy metal removal unit is provided with a third reagent inlet pipeline; the co-precipitation unit is provided with a fourth reagent inlet pipeline; the co-precipitation unit is connected to the special heavy metal removal unit through a solution reflux pipeline; the solid-liquid separation unit is connected to the phosphorus removal unit through a sludge reflux pipeline.

[0086] Example 2

[0087] like Figure 2 As shown, a method for resource recovery of landfill leachate comprises the following steps: S1: treating the landfill leachate to obtain sludge and liquid; S2: the liquid obtained in step S1 enters an organic matter storage tank, the sludge obtained in step S1 is processed, and the liquid in the organic matter storage tank can be used as a sodium acetate carbon source for sewage treatment;

[0088] The treatment of the landfill leachate in step S1 includes the landfill leachate entering the filtration unit, the electric flocculation-chemical flocculation combination unit, and the separation unit in sequence; the sludge in step S2 is processed by the sludge concentration unit; the supernatant obtained by the separation unit is then processed by the electric adsorption unit and the membrane concentration unit in sequence before entering the organic matter storage tank; the sunken sludge obtained by the separation unit enters the membrane concentration unit of the sludge concentration unit, and the filtrate obtained by the sludge concentration unit enters the organic matter storage tank.

[0089] The filtration unit of step S1 is a basket filter with a filtration accuracy of 2 mm. The electro-flocculation-chemical flocculation combined unit includes a flocculation tank, in which a plate assembly and an agitator 4 are arranged from top to bottom. The plate assembly includes an anode plate 1 and a cathode plate 2, which are arranged alternately. A flocculation filling particle assembly 3 is provided between the anode plate 1 and the cathode plate 2. Both the anode plate 1 and the cathode plate 2 are iron plates, and the current density of the anode plate 1 and the cathode plate 2 is 50-150 A / m 2 The distance between the anode plate 1 and the cathode plate 2 is 3 cm to 5 cm, and the hydraulic retention time of the electro-flocculation-chemical flocculation combined unit is 60 to 90 min.

[0090] like Figure 3 As shown, the flocculating filling particle assembly 3 includes flocculating filling particles and a fiber woven mesh bag; a plurality of flocculating filling particles are placed in the fiber woven mesh bag; the flocculating filling particles are one or two or more of sodium carbonate, calcium oxide, sodium hydroxide, and calcium hydroxide; the fiber woven mesh bag is provided with holes, the diameter of the holes is 0.5~0.8 cm; the stirring speed of the stirrer 4 is 100~150 rpm, and the stirrer 4 is made of stainless steel. The separation unit of step S1 is a vertical flow sedimentation tank; the effective water depth of the vertical flow sedimentation tank is set to 3~4 m, the water inlet pipe flow rate of the vertical flow sedimentation tank is 0.15 m~0.3 m / s, the water outlet pipe flow rate of the vertical flow sedimentation tank is 0.2 m~0.4 m / s, the gap height between the central pipe bell mouth and the reflector of the vertical flow sedimentation tank is 0.25 m~0.5 m, the rising flow rate of the vertical flow sedimentation tank is 0.5~1 mm / s, the sedimentation time of the vertical flow sedimentation tank is 1.5~2.0 h, the sludge hopper inclination angle of the vertical flow sedimentation tank is 55°~60°, and the surface load of the vertical flow sedimentation tank is 1.5~3.0 m 3 / (m 2 ·h).

[0091] The electrosorption unit of step S1 uses a membrane electrosorption or flow electrosorption mode, and the electrode material of the electrosorption unit of step S1 is an activated carbon-based electrode material; the electrode plate voltage of the electrosorption unit is 1.5-3 V, the electrode plate spacing of the electrosorption unit is 0.5-1 cm, and the hydraulic retention time of the electrosorption unit is 10-30 min;

[0092] The membrane concentration unit is a nanofiltration membrane concentration unit. The material of the nanofiltration membrane is one or more of cellulose acetate, sulfonated polysulfone or polyamide. The pore size of the nanofiltration membrane concentration unit is 5~10 nm, and the membrane flux of the nanofiltration membrane concentration unit is 10~30 L / (m 2 ·h), the operating pressure of nanofiltration membrane concentration is 1~5 MPa, the feed flow rate of nanofiltration membrane concentration is 1~5 m / s, and the retention rate of nanofiltration membrane concentration is 80%~90%;

[0093] The sludge concentration unit is an elliptical sludge dewatering machine with a processing capacity of 1~5 m 3 / h, the solid load of the sludge thickening unit is 25~60 kgDS / h, the moisture content of the sludge after dehydration is 75%~85%, the equipment speed of the sludge thickening unit is 50~150 rpm, the sludge inlet pressure of the sludge thickening unit is 0.1~0.5 MPa, and the back pressure of the sludge thickening unit is 0.05~0.2 MPa.

[0094] Example 3

[0095] The flow chart is the same as that in Example 1;

[0096] The initial pH value of the leachate from a waste incineration plant is 7.0, the COD concentration is 69900 mg / L, the total phosphorus is 80 mg / L, the heavy metal Cr concentration is 0.5 mg / L, the heavy metal arsenic concentration is 0.5 mg / L, the ammonia nitrogen concentration is 2000 mg / L, and the suspended solids concentration is 5000 mg / L. The leachate production is 100 m 3 / d, set the working time to 10 h / d, and the processing volume per hour is 10 m 3 / h.

[0097] The leachate is pumped into the 2.5 m 3 The phosphorus removal unit was equipped with a 1.5-ton (1.5-meter) dephosphorization tank. CaO powder was added to the dephosphorization unit at a rate of 50 kg / h. An automatic pH controller was installed at the rear end of the dephosphorization unit, coupled with a dosing pump. The COD concentration at the outlet of the dephosphorization unit was 69,500 mg / L, total phosphorus was 20 mg / L, heavy metal chromium concentration was 0.45 mg / L, heavy metal arsenic concentration was 0.25 mg / L, ammonia nitrogen concentration was 1900 mg / L, and the pH was 10.

[0098] Then the leachate enters the 2.5 m 3A conventional heavy metal removal unit with a capacity of 1000 liters was fed with a 40% mass fraction NaOH solution at a rate of 10 liters per hour. An automatic pH controller was installed at the back end, coupled with a dosing pump. The outlet concentration of the conventional heavy metal removal unit was 69,000 mg / L COD, 20 mg / L total phosphorus, 0.25 mg / L heavy metal chromium, 0.25 mg / L heavy metal arsenic, 1800 mg / L ammonia nitrogen, and a pH of 11.

[0099] After the conventional heavy metals are removed, the leachate enters the 7.5 m 3 The special heavy metal removal unit pool was of 1.53 million cubic meters, and 20 L / h of FeSO4 solution (40% mass fraction) was added to the unit. The COD concentration at the outlet of the special heavy metal removal unit was 67500 mg / L, the total phosphorus was 20 mg / L, the heavy metal Cr concentration was 0.15 mg / L, the heavy metal arsenic concentration was 0.01 mg / L, the ammonia nitrogen concentration was 1700 mg / L, and the pH value was 10.

[0100] After the leachate has been cleaned of heavy metals, it enters the 7.5 m 3 The coprecipitation unit tank is of a volume of 1000 m2, and FeCl3 solution (40% mass fraction) is added to the unit at a rate of 80 L / h. The COD concentration at the outlet of the coprecipitation unit is 65,000 mg / L, the total phosphorus is 0.5 mg / L, the heavy metal Cr concentration is 0.1 mg / L, the heavy metal arsenic concentration is 0.05 mg / L, the ammonia nitrogen concentration is 1600 mg / L, and the pH value is 9. A reflux is set at the end of the coprecipitation unit, and the reflux ratio is 50%, i.e., 5.0 m 3 / h.

[0101] After the leachate leaves the co-precipitation unit, it enters the 10 m 3 In the solid-liquid separation unit, the supernatant flows into the storage tank. The COD concentration at the outlet is 65,000 mg / L, the total phosphorus concentration is 0.5 mg / L, the heavy metal Cr concentration is 0.1 mg / L, the heavy metal arsenic concentration is 0.05 mg / L, the ammonia nitrogen concentration is 1600 mg / L, the pH value is 9, and the flow rate is 6.7 m 3 / h. The sinking sludge enters the sludge dewatering unit with a sludge concentration of 30,000 mg / L, a water content of 98%, a VSS ratio of 20%, and a flow rate of 3.3 m 3 / h.

[0102] The supernatant liquid leaves the solid-liquid separation unit and enters the nitrogen removal unit. The introduction of air or hot steam can make the ammonium ions in the supernatant liquid enter the gas phase from the liquid phase, and the ammonia nitrogen concentration can be reduced from 1600 mg / L to 600 mg / L. The COD concentration at the outlet of the nitrogen removal unit is 65000 mg / L, total phosphorus is 0.5 mg / L, heavy metal Cr is 0.1 mg / L, heavy metal arsenic is 0.05 mg / L, ammonia nitrogen concentration is 600 mg / L, pH value is 9, and flow rate is 6.7 m 3 / h.

[0103] After the sludge-water mixture of the sinking sludge leaves the solid-liquid separation unit, part of the sludge is returned to the sludge, and the return ratio is 10%, that is, 0.33 m 3 / h; the remaining 90% of the sludge enters the sludge dehydration unit, and the sludge moisture content can be reduced from 98% to 80%. The filtrate passing through the dehydrator has a COD concentration of 60,000 mg / L, total phosphorus of 0.4 mg / L, heavy metal Cr 0.1 mg / L, heavy metal arsenic 0.05 mg / L, ammonia nitrogen concentration of 1500 mg / L, a pH value of 9, and a flow rate of 2.7 m 3 / h; the moisture content of the filter residue is 80%, and the production volume is 0.3 m 3 / h, dry solid content is 40kg / L, and the filter residue is sent to the waste incineration plant for incineration. Finally, the two liquids are mixed, with a COD concentration of 63500 mg / L, total phosphorus 0.46 mg / L, heavy metal Cr 0.1 mg / L, heavy metal arsenic 0.05 mg / L, ammonia nitrogen concentration of 600 mg / L, pH value of 9, and flow rate of 9.7m 3 / h, has low toxicity and can be used as a sodium acetate carbon source in sewage treatment.

[0104] Example 4

[0105] The flow chart is the same as that in Example 2;

[0106] The initial pH value of the leachate from a waste incineration plant is 6.9, the COD concentration is 40,000 mg / L, the total phosphorus is 80 mg / L, the heavy metal Cr concentration is 0.5 mg / L, the heavy metal arsenic concentration is 0.5 mg / L, the suspended solids concentration is 10,000 mg / L, and the conductivity is 30 ms / cm. The leachate production is 120 m 3 / d, set 24-hour working time, and the processing volume per hour is 5 m 3 / h. The leachate passes through a 10-mesh basket filter and enters the electro-flocculation-chemical flocculation combination unit. The distance between the electro-flocculation plates is 3 cm and the residence time is 90 min. The plates are filled with calcium oxide-sodium hydroxide flocculation particles with a particle size of 1.5 cm. They are loaded with a polyethylene mesh with a pore diameter of 0.5 cm and a stirring speed of 150 rpm. The effluent COD concentration of the electro-flocculation-chemical flocculation combination unit is 35,000 mg / L, the suspended solids concentration is 15,000 mg / L, the conductivity is 32 ms / cm, and the flow rate is 5 m 3 / h.

[0107] The mud-water mixture enters the separation unit and is separated by the vertical flow sedimentation tank. The supernatant has a COD concentration of 35,000 mg / L, a total phosphorus concentration of 0.5 mg / L, a heavy metal Cr concentration of 0.1 mg / L, a heavy metal arsenic concentration of 0.05 mg / L, suspended solids of 1,000 mg / L, a conductivity of 32 ms / cm, and a flow rate of 4 m 3 / h; the water content of the sinking sludge is 99%, the sludge concentration is 40000 mg / L, and the flow rate is 1m 3 / h.

[0108] The supernatant of the separation unit enters the electrosorption unit, which greatly reduces the conductivity of the solution. The effluent COD concentration is 35,000 mg / L, the total phosphorus is 0.5 mg / L, the heavy metal Cr concentration is 0.05 mg / L, the heavy metal arsenic concentration is 0.03 mg / L, the suspended solids concentration is 800 mg / L, and the conductivity is 10 ms / cm. After that, the solution enters the membrane concentration unit, which concentrates it 4 times. The effluent COD concentration is 140,000 mg / L, the total phosphorus is 2 mg / L, the heavy metal Cr concentration is 0.2 mg / L, the heavy metal arsenic concentration is 0.12 mg / L, the suspended solids concentration is 3200 mg / L, and the conductivity is 40 ms / cm. Finally, it enters the storage tank with a flow rate of 1 m 3 / h.

[0109] The sludge from the separation unit sinks into the sludge concentration unit. The dehydrator reduces the sludge moisture content from 99% to 80%, and the volume is reduced by 95%. The filter residue is sent for sludge treatment, and the filtrate enters the storage tank with a COD concentration of 35,000 mg / L, a total phosphorus concentration of 0.5 mg / L, a heavy metal Cr concentration of 0.1 mg / L, a heavy metal arsenic concentration of 0.05 mg / L, a suspended solids concentration of 1,000 mg / L, a conductivity of 32 ms / cm, and a flow rate of 0.95 m 3 / h, and finally the storage tank obtained two mixed liquids. The COD concentration of the liquid in the storage tank was 88846 mg / L, the total phosphorus was 1.3 mg / L, the heavy metal Cr concentration was 0.15 mg / L, the heavy metal arsenic concentration was 0.08 mg / L, the suspended solids concentration was 2128 mg / L, the conductivity was 36 ms / cm, and the flow concentration was 1.95 m 3 / h.

[0110] Calculated based on a processing scale of 100 tons / day, the investment cost of the leachate resource treatment facility of the present invention is approximately 1 to 2 million yuan, while the cost of the harmless treatment facility for landfill leachate on the market is approximately 10 million yuan, thus saving 80% of the investment cost.

[0111] Secondly, the treatment cost of conventional landfill leachate harmless treatment facilities is 80 to 100 yuan per ton, while the operating cost of the leachate resource treatment facility of the present invention is about 50 yuan, thus reducing the operating cost by 30% to 50%.

[0112] The organic matter in the leachate generated by the project can be sent to the sewage treatment plant for co-treatment, reducing the amount of sodium acetate carbon source added to the sewage treatment plant. Calculated at a sodium acetate carbon source equivalent of 300,000 mg / L, the average leachate organic matter content can reach 50,000 mg / L. With an annual production of 30,000 tons, this can save 5,000 tons of sodium acetate. At 1,000 yuan per ton of sodium acetate, this can save the sewage treatment plant approximately 5 million yuan in carbon source addition costs annually.

[0113] As shown in Table 1, Example 3 of the present invention has the advantages of low operating cost and relatively stable reaction, and Example 4 of the present invention has the advantages of fast reaction speed and small footprint.

[0114] Table 1 Comparison of reaction time, floor space, operating cost and reaction stability between Example 3 and Example 4

[0115] ;

[0116] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for recycling landfill leachate, characterized by: The steps include: S1: Treat the landfill leachate to obtain sludge and liquid; S2: The liquid obtained in step S1 enters the organic matter storage tank, and the sludge obtained in step S1 is processed. The liquid in the organic matter storage tank can replace the sodium acetate carbon source and be used in sewage treatment; The treatment of the landfill leachate in step S1 includes the landfill leachate sequentially entering a filtration unit, an electro-flocculation-chemical flocculation combination unit, and a separation unit; The sludge in step S2 is processed through a sludge thickening unit; The supernatant obtained from the separation unit is then processed in the electric adsorption unit and the membrane concentration unit before entering the organic matter storage tank; The sinking sludge obtained from the separation unit enters the membrane concentration unit of the sludge concentration unit, and the filtrate obtained from the sludge concentration unit enters the organic matter storage tank; The filtration unit in step S1 is a basket filter, and the filtration accuracy of the basket filter is 2 mm; The electric flocculation-chemical flocculation combination unit includes a flocculation tank, a plate assembly, and a stirrer. The plate assembly and the stirrer are sequentially arranged in the flocculation tank from top to bottom. The plate assembly includes an anode plate and a cathode plate, which are arranged alternately. A flocculation filling particle assembly is provided between the anode plate and the cathode plate. Both the anode plate and the cathode plate are iron plates, and the current density of the anode plate and the cathode plate is 50~150 A / m 2 The spacing between the anode and cathode plates is 3 cm to 5 cm, and the hydraulic retention time of the electro-flocculation-chemical flocculation combined unit is 60 to 90 minutes. The flocculation filling particle assembly includes flocculation filling particles and a fiber woven mesh bag; a plurality of flocculation filling particles are arranged in the fiber woven mesh bag; The flocculating filling particles are one or two or more of sodium carbonate, calcium oxide, sodium hydroxide and calcium hydroxide; The fiber woven mesh bag is provided with holes with a diameter of 0.5-0.8 cm; The stirring speed of the stirrer is 100-150 rpm, and the stirrer is made of stainless steel; The separation unit of step S1 is a vertical flow sedimentation tank; The effective water depth of the vertical flow sedimentation tank is 3~4 m, the flow rate of the water inlet pipe of the vertical flow sedimentation tank is 0.15 m~0.3 m / s, the flow rate of the water outlet pipe of the vertical flow sedimentation tank is 0.2 m~0.4 m / s, the gap height between the central pipe bell mouth and the reflector of the vertical flow sedimentation tank is 0.25 m~0.5 m, the rising flow rate of the vertical flow sedimentation tank is 0.5~1 mm / s, the sedimentation time of the vertical flow sedimentation tank is 1.5~2.0 h, the sludge hopper inclination angle of the vertical flow sedimentation tank is 55°~60°, and the surface load of the vertical flow sedimentation tank is 1.5~3.0 m 3 / (m 2 ·h).

2. The method for recycling landfill leachate according to claim 1, wherein: The electrosorption unit of step S1 uses one of membrane electrosorption or flow electrosorption modes, and the electrode material of the electrosorption unit of step S1 is an activated carbon-based electrode material; The plate voltage of the electrosorption unit is 1.5-3 V, the plate spacing of the electrosorption unit is 0.5-1 cm, and the hydraulic retention time of the electrosorption unit is 10-30 min; The membrane concentration unit uses nanofiltration membrane for concentration. The material of the nanofiltration membrane is one or more of cellulose acetate, sulfonated polysulfone or polyamide. The pore size of the nanofiltration membrane concentration is 5~10 nm, and the membrane flux of the nanofiltration membrane concentration is 10~30 L / (m 2 ·h), the operating pressure of nanofiltration membrane concentration is 1~5 MPa, the feed flow rate of nanofiltration membrane concentration is 1~5 m / s, and the retention rate of nanofiltration membrane concentration is 80%~90%; The sludge concentration unit is an elliptical sludge dewatering machine with a processing capacity of 1~5 m 3 / h, the solid load of the elliptical stack sludge dewatering machine is 25~60 kgDS / h, the moisture content of the sludge after dehydration is 75%~85%, the speed of the elliptical stack sludge dewatering machine is 50~150 rpm, the mud inlet pressure of the elliptical stack sludge dewatering machine is 0.1~0.5 MPa, and the back pressure of the elliptical stack sludge dewatering machine is 0.05~0.2 MPa; The filter residue from the sludge dewatering unit is treated in the sludge treatment device.

3. The system used in the method for recycling landfill leachate according to any one of claims 1 to 2, characterized in that: It includes filtration unit, electric flocculation-chemical flocculation combination unit, separation unit, electric adsorption unit, membrane concentration unit, organic matter storage tank, sludge concentration unit, and sludge treatment device; The filtration unit, the electric flocculation-chemical flocculation combination unit, the separation unit, the electric adsorption unit, and the membrane concentration unit are sequentially connected through pipelines; The separation unit is connected to the sludge concentration unit through a pipeline, and the membrane concentration unit is connected to the organic matter storage tank through a pipeline; the sludge concentration unit is connected to the sludge treatment device through a pipeline; the sludge concentration unit is connected to the sludge treatment device through a pipeline, and the sludge concentration unit is connected to the organic matter storage tank through a pipeline.

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