Solid waste landfill leachate treatment system and process

Abstract

The invention discloses a solid waste landfill leachate treatment system and process, and relates to the technical field of solid waste leachate treatment.The treatment process comprises the following steps that solid waste landfill leachate is pretreated through a filter, large-particle matter is removed, then the solid waste landfill leachate is fed into a raw water collecting tank, standing and sedimentation are conducted, and a solid waste leachate stock solution is obtained; introducing the sludge into a digestion tank, performing intermittent aeration, performing wood particle and microbiological treatment, introducing the treated sludge into a precipitation tank, separating the sludge, wood particles and water, introducing supernate into a reaction tank, performing wood particle and microbiological treatment, and discharging the supernate; the process provided by the invention solves the problems that microorganisms in a treatment system are easy to inhibit, the treatment effect is poor, the treated liquid is difficult to reach the standard and the like when the high-concentration leachate is treated by an existing biological method, the high-concentration leachate can still keep good microbial activity, organic matters in the sewage are repeatedly subjected to aerobic and anaerobic decomposition in the digestion tank, and the treatment effect is good. And high-efficiency removal can be realized.

Description

Technical Field

[0001] This invention relates to the field of solid waste leachate treatment technology, specifically to a treatment system and process for solid waste landfill leachate. Background Technology

[0002] With economic development, population growth, and the continuous improvement of living standards, the amount of urban waste has increased rapidly, making proper waste disposal an urgent task. Common solid waste treatment methods include landfill, incineration, composting, and comprehensive utilization. Among these, landfill has become the main method of waste treatment both domestically and internationally due to its convenient management, low treatment costs, and mature technology. Leachate is wastewater formed during the landfilling and disposal process, consisting of water produced from the decomposition of organic matter in the waste, free water in the waste, atmospheric precipitation, and infiltrated groundwater. Leachate is characterized by large fluctuations in water quality (unstable water quality), complex water quality (containing various heavy metal ions and ammonia nitrogen), high organic concentration, and poor biodegradability, easily causing serious pollution to surrounding soil and groundwater. Therefore, the effective collection and treatment of landfill leachate has attracted widespread attention and urgently needs to be addressed.

[0003] Currently, landfill leachate treatment technologies used both domestically and internationally can be mainly divided into three categories: physicochemical methods, land treatment methods, and biological methods. Physicochemical methods include coagulation, air stripping, activated carbon adsorption, evaporation, chemical precipitation, ion exchange, and membrane separation. These methods are less affected by changes in leachate quality and quantity, resulting in stable effluent quality, but they are relatively expensive. Land treatment methods include slow infiltration, rapid infiltration, surface runoff, constructed wetlands, and recharge. These methods have lower investment and operating costs and strong resistance to shock loads. However, land treatment methods are limited by land resources and can easily lead to the accumulation of heavy metals and salts in the soil, causing pollution to soil and groundwater. Biological treatment methods can be divided into two main categories: aerobic biological treatment and anaerobic biological treatment. Aerobic treatment processes include activated sludge processes, aerated oxidation ponds, and biological rotating discs, while anaerobic treatment processes include anaerobic biological filters, anaerobic contact processes, and anaerobic mixed beds. Biological treatment methods have low operating costs, high treatment efficiency, and do not produce chemical sludge. However, existing biological methods are difficult to adapt to changes in leachate quality and quantity, especially when ammonia nitrogen and heavy metal concentrations are high. These high concentrations strongly inhibit the microorganisms in the treatment system, affecting the treatment effect and making it difficult for the effluent to meet standards. There is a lack of biological treatment methods that can maintain good microbial activity even with high concentrations of leachate.

[0004] Chinese patent document CN201611214409.9 discloses a method for treating landfill leachate based on a combination of active microorganisms and biological agents, including the following steps: a) measuring the concentration of pollutants in the landfill leachate before treatment; b) preparing the combination of active microorganisms and biological agents according to the pollutant concentration, and then preparing an aqueous solution of the combination of active microorganisms and biological agents; c) injecting the aqueous solution of the combination of active microorganisms and biological agents into the landfill leachate; d) observing and measuring the concentration of pollutants in the landfill leachate after treatment. However, this treatment method is not effective when treating high-concentration leachate. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a solid waste landfill leachate treatment system and process. Addressing the problems of microbial inhibition, poor treatment efficiency, and difficulty in achieving standards in existing biological treatment methods for high-concentration leachate, the present invention proposes an intermittent aeration biological treatment method that maintains good microbial activity even in high-concentration leachate. The treatment system consists of a collection tank, multiple digestion tanks, a sedimentation tank, and a reaction tank. Treated wood chips, combined in a specific particle size ratio, are placed in the digestion and reaction tanks. Organic matter in the wastewater undergoes repeated aerobic and anaerobic decomposition in the digestion tanks, achieving highly efficient removal.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A solid waste landfill leachate treatment system includes a raw water collection tank, a digestion tank, a sedimentation tank, and a reaction tank; the digestion tank and the reaction tank are filled with wood chips, and the raw material for the wood chips is fir wood.

[0008] Preferably, the digester is connected to an aeration device, and the aeration mode is intermittent aeration, with an air supply and stop time ratio of 8:16 to 16:8.

[0009] Preferably, the number of digestion tanks is ≥1.

[0010] Preferably, the wood chips have a particle size of 2-5 mm.

[0011] Preferably, the filling height of the wood chips is 6-7 cm.

[0012] Preferably, the wood chips are loaded with microorganisms, which are one or more of aerobic microorganisms, anaerobic microorganisms, and facultative aerobic microorganisms.

[0013] Preferably, the raw water collection tank is connected to an odor treatment device.

[0014] This invention also claims a solid waste landfill leachate treatment process utilizing the said leachate treatment system, comprising the following steps:

[0015] The leachate from the solid waste landfill is pretreated using a filter to remove large particles. It is then sent to a raw water collection tank for settling to obtain raw leachate. This raw leachate is then fed into a digestion tank with intermittent aeration. After treatment with wood chips and microorganisms, it is fed into a sedimentation tank to separate sludge, wood chips, and water. The supernatant is fed into a reaction tank and treated with wood chips and microorganisms before being discharged.

[0016] Preferably, the pretreatment process also includes collecting and treating the odor generated during the pretreatment process.

[0017] Preferably, the sludge settled in the sedimentation tank is sent back to the digestion tank for secondary treatment via an air return pump.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1) This invention provides a solid waste landfill leachate treatment process suitable for high-concentration solid waste leachate. First, pretreatment removes large particulate matter. Then, the leachate is introduced into a raw water collection tank to allow solid matter to settle, buffering the leachate and ensuring a quantitative and stable supply of wastewater to the digester. Next, the leachate is fed into the digester, where wood chips and loaded microorganisms decompose organic matter into carbon dioxide and water under the action of enzymes within the bacteria. A sedimentation tank separates sludge, wood chips, and water. The sludge settles at the bottom of the tank and is returned to the digester via an air return pump, ultimately decomposing into H2O and CO2. Finally, in the reaction tank, wood chips and loaded microorganisms further decompose the unsettled sludge in the supernatant. This process employs a combination of intermittent aeration, wood chips, and microorganisms for solid waste leachate treatment, resulting in low energy consumption, minimal sludge discharge, and the ability to internally recycle and digest the generated sludge with good removal efficiency.

[0020] 2) This invention provides a solid waste landfill leachate treatment system. The wood chips are processed from cedar wood. Cedar wood has abundant natural wood pores and microvascular gaps, which have good adsorption and filtration performance. At the same time, its wood fibers have good toughness and are not easy to rot or deform when soaked in water for a long time. Cedar wood is rich in cellulose, which can not only serve as a carbon source for denitrification, but also as an attachment carrier for microorganisms. When added to the digester, it has a good denitrification effect. In addition, cedar wood is a natural resource with good cost advantages.

[0021] 3) This invention provides a solid waste landfill leachate treatment system. The microbial system has a strong BOD tolerance, and the BOD load that the digestion tank can withstand can generally reach 4 kg / m³ within 4-8 hours. 3 ·d, when the BOD load is less than 4 kg / m 3 When the load is around 6 kg / m³, the processing system is basically normal.3 At ·d, microorganisms are affected and their activity decreases. When treating high-concentration leachate, diluting the leachate to a certain level using effluent recirculation before treatment can prevent microbial death and ensure the normal operation of the treatment system. Attached Figure Description

[0022] 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.

[0023] Figure 1 The present invention provides a process flow diagram for the treatment of leachate from solid waste landfills. Detailed Implementation

[0024] 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 merely illustrative and not intended to limit the invention.

[0025] 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.

[0026] This invention provides a solid waste landfill leachate treatment system, including a raw water collection tank, a digestion tank, a sedimentation tank, and a reaction tank; the raw water collection tank is connected to an odor treatment device.

[0027] The digestion tank and the reaction tank are filled with wood chips, the raw material of which is fir wood, the particle size of which is 2-5 mm, and the filling height of which is 6-7 cm. The digestion tank is connected to an aeration device, and the aeration mode is intermittent aeration, with an air supply to stop time ratio of 8:16 to 16:8.

[0028] Specifically, the number of digestion tanks is ≥1, preferably 3.

[0029] Specifically, the wood chips are loaded with microorganisms, which are one or more of aerobic, anaerobic, and facultative aerobic microorganisms.

[0030] This invention also claims a solid waste landfill leachate treatment process utilizing the said leachate treatment system, comprising the following steps:

[0031] The leachate from the solid waste landfill is pretreated using a filter to remove large particulate matter and collect and treat the odor generated during the pretreatment process. The leachate is then sent to a raw water collection tank for settling to obtain raw leachate solution. This raw leachate solution is then fed into a digestion tank with intermittent aeration. After treatment with wood chips and microorganisms, it is fed into a sedimentation tank to separate sludge, wood chips, and water. The settled sludge is returned to the digestion tank for secondary treatment via an air return pump, while the supernatant is fed into a reaction tank for further treatment with wood chips and microorganisms before being discharged.

[0032] The present invention will be further described below through specific embodiments.

[0033] Example 1

[0034] A process for treating leachate from a solid waste landfill includes the following steps:

[0035] The leachate from the solid waste landfill is pretreated using a filter to remove large particles larger than 2 mm. The treated leachate is then fed into a raw water collection tank for settling to obtain raw leachate solution. This raw leachate solution is then fed into three digestion tanks (filled with 2-3 mm wood chips to a height of 6 cm, loaded with aerobic, anaerobic, and facultative anaerobic bacteria including *Nitrifying Bacillus*, acetic acid-producing methanogens, and *Bacillus*). Intermittent aeration is applied. After treatment with the wood chips and microorganisms, the solution is fed into a sedimentation tank to separate sludge, wood chips, and water. The sludge settled in the sedimentation tank is returned to the digestion tank via an air return pump for secondary treatment. The supernatant is fed into a reaction tank, where it is treated with wood chips and microorganisms before being discharged.

[0036] The experimental device was connected to the existing domestic sewage treatment system of a solid waste landfill. The average COD concentration of the leachate treated in this field test was 2944.96 mg / L, the average SS concentration was 265.32 mg / L, the average ammonia nitrogen concentration was 241.14 mg / L, and the average BOD5 concentration was 1251.08 mg / L. The leachate was continuously added at rates of 360, 600, and 1080 L / h, with aeration for 12 hours followed by a 12-hour shutdown. The treatment capacity was 3 m³. 3 / d.

[0037] The results of the on-site test are shown in the table below. The removal rates were 93% for SS, 99.8% for ammonia nitrogen, 98.2% for COD, and 97.9% for BOD5. These results indicate that the average removal rate of organic matter was above 90% under all operating conditions. This demonstrates that the system has a special function in treating ammonia nitrogen, with extremely significant treatment effects. It also shows good results in reducing color, SS, and BOD, and the effluent quality meets or exceeds the Class II standard of GB 16889-2008.

[0038] Table 1. Processing Results of Example 1

[0039]

[0040] Comparative Example 1

[0041] A process for treating leachate from a solid waste landfill includes the following steps:

[0042] The leachate from the solid waste landfill is pretreated using a filter to remove large particles larger than 2 mm. The treated leachate is then fed into a raw water collection tank for settling to obtain raw leachate solution. This raw leachate solution is then fed into a digestion tank (three tanks loaded with aerobic, anaerobic, and facultative anaerobic bacteria: Nitrifying Bacteria, Acetic Acid-Producing Methanogens, and Bacillus) with intermittent aeration. After microbial treatment, the solution is fed into a sedimentation tank to separate sludge from water. The sludge settled in the sedimentation tank is returned to the digestion tank via an air return pump for secondary treatment. The supernatant is fed into a reaction tank, treated by microorganisms, and then discharged.

[0043] Similarly, the experimental device was connected to the existing domestic sewage treatment system of a solid waste landfill. The average COD concentration of the leachate treated in the experiment was 2944.96 mg / L, the average SS concentration was 265.32 mg / L, the average ammonia nitrogen concentration was 241.14 mg / L, and the average BOD5 concentration was 1251.08 mg / L. The leachate was continuously added at rates of 360, 600, and 1080 L / h, with aeration for 12 hours followed by a 12-hour shutdown. The treatment capacity was 3 m³. 3 / d.

[0044] The results of the on-site test are shown in the table below. The removal rates were 66.31% for SS, 58.18% for ammonia nitrogen, 70.28% for COD, and 61.54% for BOD5. These results indicate that the organic matter removal rates under all operating conditions were significantly lower than in Example 1. This demonstrates that fir wood chips, acting as a carbon source for denitrification and a carrier for microorganisms, significantly promote the efficient treatment of leachate.

[0045] Table 2 shows the results of the treatment in Comparative Example 1.

[0046]

[0047]

[0048] 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 solid waste landfill leachate treatment system, characterized in that, It includes a raw water collection tank, a digestion tank, a sedimentation tank, and a reaction tank; the digestion tank and the reaction tank are filled with wood chips, and the raw material for the wood chips is fir wood.

2. The leachate treatment system according to claim 1, characterized in that, The digester is connected to an aeration device, and the aeration mode is intermittent aeration, with an air supply and stop time ratio of 8:16 to 16:

8.

3. The leachate treatment system according to claim 1, characterized in that, The number of digestion tanks is ≥1.

4. The leachate treatment system according to claim 1, characterized in that, The wood chips have a particle size of 2-5 mm.

5. The leachate treatment system according to claim 1, characterized in that, The filling height of the wood chips is 6-7 cm.

6. The leachate treatment system according to claim 1, characterized in that, Wood chips are loaded with microorganisms, which are one or more of aerobic, anaerobic, and facultative aerobic microorganisms.

7. The leachate treatment system according to claim 1, characterized in that, The raw water collection tank is connected to an odor treatment device.

8. A solid waste landfill leachate treatment process utilizing the leachate treatment system according to any one of claims 1 to 7, characterized in that, Includes the following steps: The leachate from the solid waste landfill is pretreated using a filter to remove large particles. It is then sent to a raw water collection tank for settling to obtain raw leachate. This raw leachate is then fed into a digestion tank with intermittent aeration. After treatment with wood chips and microorganisms, it is fed into a sedimentation tank to separate sludge, wood chips, and water. The supernatant is fed into a reaction tank and treated with wood chips and microorganisms before being discharged.

9. The process according to claim 8, characterized in that, The pretreatment process also includes collecting and treating the odor generated during the pretreatment process.

10. The process according to claim 8, characterized in that, The sludge settled in the sedimentation tank is sent back to the digestion tank for secondary treatment via an air return pump.

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