Treatment method of landfill leachate

Abstract

The invention relates to the technical field of landfill leachate treatment, in particular to a landfill leachate treatment method. Performing solid-liquid separation on the landfill leachate to obtain filtrate; mixing the filtrate with nano zero-valent iron loaded by activated carbon, carrying out stirring reaction to obtain a reactant, and carrying out pressure filtration on the reactant to obtain a pressure filtrate; after being treated by the method disclosed by the invention, the landfill leachate also keeps relatively high organic matter content and can be used as a carbon source in other biochemical treatment, so that waste is turned into wealth. The method not only can reduce the treatment cost of the landfill leachate and shorten the treatment process, but also can realize effective recycling of organic matters in the wastewater, and has important environmental and economic values.

Description

Technical Field

[0001] The invention relates to the technical field of landfill leachate treatment, in particular to a landfill leachate treatment method. Background Art

[0002] With the acceleration of urbanization, the amount of garbage generated has increased dramatically, and garbage treatment and resource recycling have become important issues in the field of environmental protection. Leachate is a common high-concentration organic wastewater in landfills, containing a large amount of organic matter, heavy metal ions, ammonia nitrogen and other pollutants. These pollutants pose a serious threat to the environment and human health. Therefore, the effective treatment and resource recycling of leachate is of great significance.

[0003] At present, the treatment technology of landfill leachate is "Fenton oxidation + biochemical treatment + membrane treatment", and finally the discharge reaches the standard. The specific steps are as follows: Fenton oxidation: through Fenton reagent (Fe 2+ and H2O2) to produce strong oxidizing hydroxyl radicals, which oxidize refractory organic matter. Biochemical treatment: Use microorganisms to degrade organic pollutants and reduce the biochemical oxygen demand (BOD) and chemical oxygen demand (COD) in wastewater. Membrane treatment: Use membrane technologies such as reverse osmosis and nanofiltration to remove dissolved solids and some heavy metal ions in wastewater.

[0004] Although existing technologies can treat pollutants in landfill leachate to a certain extent, the following problems still exist: High treatment cost: The biochemical treatment site occupies a large area, the membrane treatment equipment is expensive, the Fenton treatment agent cost is high, and the operation and maintenance cost of the entire treatment process is high. Large amount of tailings: A large amount of sludge is generated during the biochemical treatment and Fenton oxidation process, which requires further treatment and disposal. Low resource recovery rate: Existing technologies mainly focus on the removal of pollutants, and the recycling of useful substances in wastewater, such as organic matter, is insufficient. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method for treating landfill leachate. The treatment method provided by the present invention greatly reduces the treatment cost of landfill leachate, shortens the treatment cycle, and realizes the effective utilization of organic matter in the landfill leachate.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for treating landfill leachate, comprising the following steps:

[0008] 1) separating the solid and liquid of the landfill leachate to obtain a filtrate;

[0009] 2) mixing the filtrate obtained in step 1) with the nano zero-valent iron supported on activated carbon, and stirring to react to obtain a reactant;

[0010] The amount of nano zero-valent iron loaded on the activated carbon is 2 g / L;

[0011] The stirring reaction conditions include: a rotation speed of 150-300 rpm and a time of 30 min;

[0012] The components of the activated carbon-supported nano zero-valent iron include nano zero-valent iron, ferrous sulfate and activated carbon, and the mass ratio of the nano zero-valent iron, ferrous sulfate and activated carbon is 1:0.5 to 1:1 to 2;

[0013] 3) The reactant obtained in step 2) is filtered to obtain a filtrate.

[0014] Preferably, in step 1), a screw stacking machine is used to separate the solid and liquid of the landfill leachate.

[0015] Preferably, the water content of the nano zero-valent iron supported on activated carbon in step 2) is 15-20%.

[0016] Preferably, the method for preparing the activated carbon-supported nano zero-valent iron comprises the following steps:

[0017] Mixing the nano zero-valent iron with water to form a slurry;

[0018] The slurry is mixed with ferrous sulfate and activated carbon, and the precipitate obtained by centrifugation is nanometer zero-valent iron supported by activated carbon.

[0019] Preferably, the concentration of nano zero-valent iron in the slurry is 8-10 wt.%.

[0020] Preferably, the conditions for using plate and frame filtration in step 3) include: pressure of 0.6-1 MPa and time of 0.5-1.5 h.

[0021] The present invention also provides application of the treatment method described in the above technical solution in reducing the heavy metal content of landfill leachate.

[0022] Preferably, the heavy metals include chromium and / or mercury.

[0023] Beneficial effects of the present invention:

[0024] The treatment method provided by the present invention includes "solid-liquid separation + heterogeneous Fenton-like oxidation + filtration". First, the solids in the landfill leachate are separated by a screw stacker or flotation method to effectively reduce the solid matter content in the leachate. Then, the activated carbon-loaded nano zero-valent iron material is used to effectively remove heavy metal elements in the waste liquid, wherein the activated carbon and nano zero-valent iron constitute a micro-electrolysis system, which can achieve catalytic degradation of difficult-to-degrade organic matter in the leachate, degrading large molecular organic matter into small molecular organic matter, and reducing and adsorbing and removing heavy metals. After the treated solution is filtered, the COD in the leachate can be used to supplement the carbon source in biochemical treatment.

[0025] The advantage of this method is that it greatly reduces the treatment cost of landfill leachate, shortens the treatment cycle, and realizes the effective utilization of organic matter in the leachate.

[0026] Cost reduction and effective resource recovery are achieved through innovations in the following aspects:

[0027] 1. First, through solid-liquid separation, the solid content in the leachate is reduced to avoid increasing the consumption of materials during the Fenton oxidation process.

[0028] 2. Then, a composite material was prepared using activated carbon and nano-zero-valent iron to construct a heterogeneous Fenton-like system. Through the micro-electrolysis system between iron and carbon, the macromolecules in the leachate were degraded into small molecules, and the heavy metals in the leachate were converted into free states. At the same time, the strong reduction and adsorption properties of the nano-zero-valent iron material in the composite material were used to remove the heavy metals in the solution.

[0029] 3. Finally, the composite material is removed from the leachate by filtration, thereby achieving effective removal of heavy metals in the leachate.

[0030] After the above treatment, the leachate still maintains a relatively high content of organic matter and can be used as a carbon source in other biochemical treatments, turning waste into treasure.

[0031] The present invention can not only reduce the cost of landfill leachate treatment and shorten the treatment process, but also realize the effective recycling of organic matter in wastewater, and has important environmental and economic value. DETAILED DESCRIPTION

[0032] The present invention provides a method for treating landfill leachate, comprising the following steps:

[0033] 1) separating the solid and liquid of the landfill leachate to obtain a filtrate;

[0034] 2) mixing the filtrate obtained in step 1) with the nano zero-valent iron supported on activated carbon, and stirring to react to obtain a reactant;

[0035] The amount of nano zero-valent iron loaded on the activated carbon is 2 g / L;

[0036] The stirring reaction conditions include: a rotation speed of 150-300 rpm and a time of 30 min;

[0037] The components of the activated carbon-supported nano zero-valent iron include nano zero-valent iron, ferrous sulfate and activated carbon, and the mass ratio of the nano zero-valent iron, ferrous sulfate and activated carbon is 1:0.5 to 1:1 to 2;

[0038] 3) The reactant obtained in step 2) is filtered to obtain a filtrate.

[0039] The present invention separates the solid and liquid of the landfill leachate to obtain a filtrate. The present invention preferably uses a screw press to separate the solid and liquid of the landfill leachate. The present invention has no special restrictions on the source of the landfill leachate. The present invention has no specific requirements on the parameter conditions of the screw press, but only realizes a simple solid-liquid separation. Of course, in addition to the screw press separator, centrifugal separation, plate and frame filter press and other means can also be used here.

[0040] The present invention mixes the obtained filtrate with nano zero-valent iron supported by activated carbon, performs stirring reaction, and obtains a reactant; the addition amount of the nano zero-valent iron supported by activated carbon is 2g / L; the conditions of the stirring reaction include: a rotation speed of 150-300rpm and a time of 30min; the components of the nano zero-valent iron supported by activated carbon include nano zero-valent iron, ferrous sulfate and activated carbon, and the mass ratio of the nano zero-valent iron, ferrous sulfate and activated carbon is 1:0.5-1:1-2. In the present invention, the water content of the nano zero-valent iron supported by activated carbon is preferably 15-20%. In the present invention, the preparation method of the nano zero-valent iron supported by activated carbon preferably includes the following steps: mixing the nano zero-valent iron with water to prepare a slurry; mixing the slurry with ferrous sulfate and activated carbon, and centrifuging to obtain a precipitate of nano zero-valent iron supported by activated carbon. In the present invention, the concentration of nano zero-valent iron in the slurry is preferably 8-10wt.%.

[0041] The present invention filters the obtained reactants to obtain a filtrate. The present invention preferably uses plate and frame filtration under the following conditions: a pressure of 0.6 to 1 MPa and a time of 0.5 to 1.5 hours. In the present invention, the filtrate has a low heavy metal content, meets national standards, and can be sold directly.

[0042] The present invention also provides the use of the treatment method described in the above technical solution in reducing the heavy metal content of landfill leachate. In the present invention, the heavy metal preferably includes chromium and / or mercury.

[0043] In order to further illustrate the present invention, the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0044] Example 1

[0045] The raw leachate composition: COD 17600mg / L, SS 1800mg / L, total chromium content 0.602mg / L, total Hg content 0.002mg / L.

[0046] Processing steps:

[0047] (1) The landfill leachate is filtered and treated by a spiral press to reduce the solid matter content in the leachate, and the SS is reduced to below 200 mg / L after treatment;

[0048] (2) Adding the composite material, the amount of the material added is 2 g / L, stirring continuously after the material is added, the stirring rate is 150-300 rpm, and the reaction time is 30 min;

[0049] The composite material is composed of nano zero-valent iron, ferrous sulfate and activated carbon, wherein the mass ratio of nano zero-valent iron: ferrous sulfate: activated carbon is 1:1:2; the role of ferrous sulfate is to provide divalent iron ions to prevent the rapid failure of nano zero-valent iron, and the activated carbon can reduce the agglomeration of nano zero-valent iron materials and improve the adsorption performance of the materials.

[0050] The specific preparation method is as follows: firstly, nanometer zero-valent iron is prepared into a slurry with a concentration of 10wt.%, and then ferrous sulfate is added and stirred evenly. Finally, activated carbon is slowly added, stirring continuously during the addition process, and then water is removed by centrifugal filtration to obtain a composite material. The material is in a wet solid state, and the water content is 18%;

[0051] (3) The material is filtered through a plate and frame filter under the following conditions: pressure of 0.6-1 MPa and time of 0.5-1.5 h;

[0052] (4) After treatment, the COD content in the solution was 11400 mg / L, the total chromium content was 0.014 mg / L (the standard is 0.1 mg / L), and the total mercury content was 0.0007 mg / L (the standard is 0.001 mg / L).

[0053] The treated leachate is packed in ton barrels and sold. The material cost of this treatment is 16 yuan / ton, the comprehensive cost is 18.5 yuan / ton (including manpower, electricity consumption, and equipment loss), and the sales price of the treated waste liquid is 65 yuan / ton. After comprehensive conversion, there is still a certain profit.

[0054] Comparative Example 1

[0055] (Original processing technology):

[0056] (1) filtering the landfill leachate (same as in Example 1) through a screw stack to separate the solid and liquid, thereby reducing the solid content of the waste liquid;

[0057] (2) The pH value of the leachate was adjusted to 3.5 by adding dilute sulfuric acid, and then 18 g / L of ferrous sulfate and 1.8 g / L of hydrogen peroxide were added and stirred for 30 min. After treatment, the COD in the leachate was reduced to 3650 mg / L;

[0058] (3) Biochemical treatment, using two-stage A / O biochemical treatment (Tong Xingming. Research on the treatment of landfill leachate by hydrolysis acidification-Fenton-two-stage A / O MBR-nanofiltration process [D]. Jiangnan University, 2022. [2] Yu Xiangkui, Li Li. A case study of landfill leachate treatment project in Changzhou [J]. Railway Energy Conservation, Environmental Protection, Safety and Health, 2013, 3(006): 275-278.), with a treatment cycle of 5 days;

[0059] (4) MBR+NF deep treatment+concentrate treatment process, the leachate is filtered and treated by ultrafiltration membrane and nanofiltration membrane, on the one hand, the COD index in the waste liquid is guaranteed to meet the standard (≤100mg / L), and at the same time, the heavy metal content is reduced to ensure that it meets the standard. After membrane treatment, the concentrate is treated again by Fenton oxidation method alone.

[0060] The concentrated solution after membrane treatment is treated by Fenton oxidation method alone:

[0061] (1) The reason for separate treatment is that the concentration of the concentrate is very high, but the amount of solution is relatively small, so it is treated separately;

[0062] (2) This concentration is relatively high. The processing parameters are: pH 3.5, ferrous sulfate 40g / L, hydrogen peroxide 5g / L; first add acid to adjust the pH value of the concentrate to 3.5, then add ferrous sulfate, and after it is fully dissolved and mixed, add hydrogen peroxide.

[0063] (3) After Fenton oxidation treatment, wastewater is directly discharged if it meets the standards. If it does not meet the standards, it is returned to the front-end biochemical treatment.

[0064] The treated leachate can meet the discharge standards. The material cost of the treatment is 35 yuan / t, and the comprehensive cost is 62 yuan / t (including equipment loss, manpower, electricity consumption and membrane material loss).

[0065] Based on the above comparative analysis, the method of the present invention can greatly reduce the total cost of landfill leachate treatment, and at the same time can achieve effective utilization of organic matter in the leachate. The method is very practical in some water-scarce or remote areas, and is currently being used in a landfill in the county town of Chifeng City, Inner Mongolia, and the treated leachate is sold to some nearby water treatment plants.

[0066] The difficulty of this method is how to reduce the heavy metal content in the leachate. If the heavy metals cannot be effectively removed, the treated leachate cannot be transferred and sold. However, in the presence of organic matter, many heavy metals are complexed with organic macromolecules. How to effectively remove heavy metals without significantly reducing the COD of the solution is the biggest breakthrough of this project.

[0067] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for treating landfill leachate, characterized in that: The following steps are involved: 1) separating the solid and liquid of the landfill leachate to obtain a filtrate; 2) mixing the filtrate obtained in step 1) with the nano zero-valent iron supported on activated carbon, and stirring to react to obtain a reactant; The amount of nano zero-valent iron loaded on the activated carbon is 2 g / L; The stirring reaction conditions include: a rotation speed of 150-300 rpm and a time of 30 min; The components of the activated carbon-supported nano zero-valent iron include nano zero-valent iron, ferrous sulfate and activated carbon, and the mass ratio of the nano zero-valent iron, ferrous sulfate and activated carbon is 1:0.5 to 1:1 to 2; 3) The reactant obtained in step 2) is filtered to obtain a filtrate.

2. The processing method according to claim 1, characterized in that: The step 1) uses a screw stacking machine to separate the solid and liquid of the landfill leachate.

3. The processing method according to claim 1, characterized in that: In the step 2), the water content of the nano zero-valent iron supported by the activated carbon is 15-20%.

4. The processing method according to claim 1 or 3, characterized in that: The preparation method of the activated carbon-supported nano zero-valent iron comprises the following steps: Mixing the nano zero-valent iron with water to form a slurry; The slurry is mixed with ferrous sulfate and activated carbon, and the precipitate obtained by centrifugation is nanometer zero-valent iron supported by activated carbon.

5. The processing method according to claim 4, characterized in that: The concentration of nano zero-valent iron in the slurry is 8-10 wt.%.

6. The processing method according to claim 1, characterized in that: The conditions for using plate and frame filtration in step 3) include: pressure of 0.6-1 MPa and time of 0.5-1.5 h.

7. Use of the treatment method according to any one of claims 1 to 6 in reducing the heavy metal content in landfill leachate.

8. The use according to claim 7, characterized in that: The heavy metals include chromium and / or mercury.