A leachate membrane concentration liquid treatment process

Abstract

The application relates to the technical field of wastewater treatment, and particularly discloses a garbage leachate membrane concentrated liquid treatment process. The garbage leachate membrane concentrated liquid is treated by using sodium carbonate solution and sodium hydroxide solution first, so that part of calcium and magnesium ions form a precipitate, then the supernatant generated after layering is collected, the supernatant is filtered, and the obtained filtrate is further subjected to electrolysis. After the electrolysis treatment, the hardness of the filtrate is obviously reduced, and when the filtrate is applied in a heat evaporation process and a back spraying incinerator process, fouling is not prone to being generated, the cost and time for cleaning the fouling are not needed to be additionally paid, and the garbage leachate membrane concentrated liquid is fully utilized.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, and more specifically, to a landfill leachate membrane concentrate treatment process. Background Technology

[0002] Waste incineration for power generation is a common method of waste disposal. Waste entering a waste-to-energy plant is generally not burned directly, but first stored in a waste pit. After fermentation, leachate is extracted from the waste pile, and the remaining waste is then incinerated. This process increases the calorific value of the waste and ensures that waste can still be received when equipment malfunctions or needs maintenance, thus playing a regulatory role. The leachate generated during waste storage and the flushing water from the unloading platform are considered wastewater, which must be treated before discharge.

[0003] To meet stringent environmental impact assessment requirements, current waste incineration plants generally employ a combined treatment process of "pretreatment + biological treatment + dual membrane method (NF+RO)" to treat landfill leachate. This approach offers advantages such as good effluent quality, compliance with discharge standards, and a small footprint. However, this process generates a large amount of membrane concentrate (approximately 30% of the total influent). Biological utilization of this membrane concentrate is challenging; it cannot be directly discharged, nor can it be further purified through biological treatment. Currently, the main methods for disposing of membrane concentrate are thermal evaporation and recirculation incineration.

[0004] Regarding the aforementioned technologies, the inventors believe that although both thermal evaporation and recirculation incineration technologies can treat landfill leachate membrane concentrate, the high hardness of the membrane concentrate easily leads to a large amount of scaling inside the treatment equipment, which not only increases maintenance costs but also makes it impossible to dispose of the membrane concentrate smoothly. Summary of the Invention

[0005] In related technologies, excessively high hardness of the membrane concentrate can easily lead to significant scaling inside the treatment equipment, not only increasing maintenance costs but also hindering the successful disposal of the membrane concentrate. To address this deficiency, this application provides a landfill leachate membrane concentrate treatment process.

[0006] This application provides a landfill leachate membrane concentrate treatment process, which adopts the following technical solution:

[0007] A landfill leachate membrane concentrate treatment process includes the following steps:

[0008] (1) Prepare sodium carbonate solution and sodium hydroxide solution, transport the leachate membrane concentrate to the first reaction tank, add the prepared sodium hydroxide solution and sodium carbonate solution to the first reaction tank, adjust the pH to 10-11, and after stirring, discharge the effluent into the second reaction tank.

[0009] (2) Stir the wastewater in the second reaction tank, let it stand and separate into layers, discharge the upper clear liquid into the middle tank, discharge the middle turbid liquid into the sedimentation tank; pump the lower sludge into the sludge tank.

[0010] (3) Use a microfiltration membrane to microfilter the clear liquid in the intermediate tank to obtain filtrate, discharge the filtrate into the filtrate tank, and pump the wastewater generated during the periodic cleaning of the microfiltration membrane back to the second reaction tank; coagulate and settle the turbid liquid in the sedimentation tank, and then pump the clear liquid to the intermediate tank; press the sludge in the sludge tank, remove the filter cake, and send the remaining liquid back to the first reaction tank.

[0011] (4) Pump the clear liquid in the filtrate tank into the electrolysis device, add nucleation inducing agent to the clear liquid, and electrolyze and soften the clear liquid after energizing. After electrolysis, the treatment of landfill leachate membrane concentrate can be completed.

[0012] By adopting the above technical solution, in the first reaction tank, this application uses sodium hydroxide to convert most of the magnesium ions into magnesium hydroxide precipitate and convert some bicarbonate ions into carbonate ions; simultaneously, this application also uses sodium carbonate to supplement carbonate ions, and carbonate ions combine with calcium ions to form calcium carbonate precipitate. After the above reaction, most of the calcium and magnesium ions are converted into precipitates. The effluent from the first reaction tank carries the precipitates into the second reaction tank, where further stratification occurs. After stratification, most of the calcium and magnesium precipitates accumulate in the lower sludge layer and are removed, while a small portion remains in the middle turbid liquid. At the same time, a certain amount of calcium and magnesium ions remain in the upper clear liquid and the middle turbid liquid. After coagulation and sedimentation, the calcium and magnesium precipitates in the middle turbid liquid are removed. The upper clear liquid in the sedimentation tank and the upper clear liquid from the second reaction tank flow together into the intermediate tank, where a microfiltration membrane is used to intercept the insoluble matter to obtain the filtrate. In the electrolysis device, a DC electric field is generated between the positive and negative electrodes. The cathode has an excess of negative charge and adsorbs the calcium and magnesium ions in the filtrate to the area near the cathode. Under the influence of electric current, the water near the cathode undergoes an electrode reaction, generating hydroxide ions that increase the hydroxide ion concentration near the cathode. Hydroxide ions combine with magnesium ions near the cathode to form magnesium hydroxide, while calcium ions combine with residual carbonate ions to form calcium carbonate. Nucleation inducing agents promote the crystallization of calcium and magnesium ions and the growth of precipitates during this process. After electrolysis, the hardness of the filtrate decreases significantly, making it less prone to scaling in thermal evaporation and recirculation incinerator processes. This eliminates the need for additional costs and time spent on scaling removal, achieving full utilization of the landfill leachate membrane concentrate.

[0013] Preferably, in step (4), the current density during the electrolytic softening process is 28-33 A / m. 2 .

[0014] By adopting the above technical solution, this application has optimized the current density during the electrolytic softening process. Within this range, the migration rate of calcium and magnesium ions to the cathode and the generation rate of hydroxide ions are both relatively fast, which can generate more precipitates in the same amount of time, thus helping to quickly reduce the hardness of the filtrate.

[0015] Preferably, in step (4), the electrode spacing of the electrolysis device is 3-6 cm.

[0016] By adopting the above technical solution, and based on the preferred current density, this application optimizes the spacing between the electrodes. Within the above spacing range, a strong electric field can be maintained between the electrodes, and because the distance is relatively close, the time spent on ion migration is also relatively short, which helps to quickly reduce the hardness of the filtrate.

[0017] Preferably, in step (4), the residence time of the filtrate in the electrolysis device is 30-60 min.

[0018] By adopting the above technical solution, this application further optimizes the time spent on electrolyzing the filtrate while optimizing the current density and electrode distance. Within the above time range, the residual calcium and magnesium ions in the filtrate can be fully removed, thereby effectively reducing the hardness of the filtrate.

[0019] Preferably, the nucleation inducing agent comprises sand particles, wherein the sand particles are quartz sand or garnet sand.

[0020] By adopting the above technical solution, this application preferentially uses quartz sand or garnet sand as nucleation inducing agents. These nucleation inducing agents have relatively large particle sizes but relatively low costs. After calcium and magnesium ions precipitate on the surface of these sand particles, they can produce a porous and rough structure, which has a certain adsorption effect on organic impurities in water. Furthermore, the sand particle deposits themselves also have the function of adsorbing and purifying water, which helps to improve the water quality of the filtrate.

[0021] Preferably, the nucleation inducing agent further includes calcium carbonate seed crystals, which are prepared by the following method: quicklime is added to hot water for digestion, then allowed to stand for aging, and after sieving, refined lime milk is obtained. A calcium hydroxide suspension is prepared using the refined lime milk, and a mixture of nitrogen and carbon dioxide is introduced into the calcium hydroxide suspension. After the reaction is completed, calcium carbonate seed crystals are obtained.

[0022] By adopting the above technical solution, this application uses lime milk to prepare a calcium hydroxide suspension, and then introduces nitrogen-diluted carbon dioxide gas to allow titanium dioxide and calcium hydroxide suspension to react slowly, thereby obtaining nano-sized calcium carbonate seed crystals, which can act as nucleation inducing the formation of calcium carbonate. Through the synergistic effect of calcium carbonate seed crystals and sand particles, calcium and magnesium ions can more fully form precipitates, thus effectively reducing the hardness of the filtrate.

[0023] Preferably, the calcium hydroxide suspension is reacted with the mixed gas at 18-20°C.

[0024] By adopting the above technical solution, this application has optimized the temperature conditions for the reaction of calcium hydroxide suspension with carbon dioxide in the mixed gas. Within the above temperature range, the obtained calcium carbonate seed crystals have a more regular morphology and better dispersion effect, which can better promote the formation of calcium carbonate and help to fully reduce the hardness of the filtrate.

[0025] Preferably, the concentration of calcium hydroxide in the calcium hydroxide suspension is 1.0-1.2 mol / L.

[0026] By adopting the above technical solution, this application optimizes the calcium hydroxide concentration in the calcium hydroxide suspension. Within the above concentration range, the obtained calcium carbonate seed crystals have more regular morphology and better dispersion effect, which can better promote the formation of calcium carbonate and help to fully reduce the hardness of the filtrate.

[0027] Preferably, the nucleation inducing agent further includes modified slag powder, which is prepared by the following method: slag powder, anhydrous ethanol, water, vinylalkoxysilane and hydrochloric acid are mixed and heated to obtain a slag dispersion. A monomer and an initiator are added to the modified slag dispersion under water bath heating conditions to carry out the reaction. After the reaction is completed, the mixture is naturally cooled, the product is filtered and dried, and then ground to obtain modified slag powder. The monomer includes acrylic acid.

[0028] By adopting the above technical solution, this application first uses vinylalkoxysilane to couple and modify slag powder under acidic conditions, introducing vinyl groups onto the surface of the slag powder. Then, under the action of an initiator, the vinyl groups react with monomers. After the acrylic acid in the monomers copolymerizes with the vinyl groups, polycarboxylic acid segments can be formed on the surface of the slag powder. The polycarboxylic acid segments have a strong adsorption effect on calcium and magnesium ions, which can promote the solidification and precipitation of calcium and magnesium ions and help to fully reduce the hardness of the filtrate.

[0029] Preferably, the monomer also includes unsaturated fatty acids.

[0030] By adopting the above technical solution, this application uses unsaturated fatty acids as monomers. The long branches introduced by the unsaturated fatty acids can increase the capture range of calcium and magnesium ions by the polycarboxylic acid segments, promote the solidification and precipitation of calcium and magnesium ions, and help to fully reduce the hardness of the filtrate.

[0031] In summary, this application has the following beneficial effects:

[0032] 1. This application first treats the landfill leachate membrane concentrate with sodium carbonate and sodium hydroxide solutions, causing most of the calcium and magnesium ions to precipitate. Then, the clear liquid produced after stratification is collected. After filtration, the resulting filtrate undergoes further electrolysis. After electrolysis, the hardness of the filtrate is significantly reduced, making it less prone to scaling in thermal evaporation and reflow incinerator processes. This eliminates the need for additional cost and time for scaling removal, thus achieving full utilization of the landfill leachate membrane concentrate.

[0033] 2. The preferred type of nucleation inducing agent in this application promotes the crystallization of calcium and magnesium ions and the growth of precipitates, effectively removes residual calcium and magnesium ions in the filtrate, reduces the hardness of calcium and magnesium ions, and helps alleviate scaling in the treatment equipment.

[0034] 3. This application grafts polycarboxylic acid segments onto the surface of slag powder and further introduces long branches with carboxyl groups through unsaturated fatty acids. The polycarboxylic acid segments have a strong adsorption effect on calcium and magnesium ions, which can promote the precipitation of calcium and magnesium ions and help to significantly reduce the hardness of the filtrate. Detailed Implementation

[0035] The present application will be further described in detail below with reference to the embodiments, preparation examples and comparative examples. The raw materials involved in the present application can all be obtained commercially.

[0036] Example of calcium carbonate seed crystal preparation

[0037] The following explanation uses Preparation Example 1 as an example.

[0038] Preparation Example 1

[0039] In this preparation example, calcium carbonate seed crystals were prepared according to the following method:

[0040] Industrial-grade quicklime was added to hot water at 80℃ at a solid-liquid ratio of 1:8 for digestion, and then allowed to stand for 24 hours for aging. After sieving through a 75μm square-hole sieve, refined lime milk was obtained. A 1.5mol / L calcium hydroxide suspension was prepared using the refined lime milk. A mixture of nitrogen and carbon dioxide (nitrogen gas fraction of 70%) was introduced into the calcium hydroxide suspension at 25℃ at a rate of 480mL / min. After the reaction was complete, calcium carbonate seed crystals were obtained.

[0041] Preparation Example 2

[0042] The difference between this preparation example and Preparation Example 1 is that the calcium hydroxide suspension reacts with the mixed gas at 20°C.

[0043] Preparation Example 3

[0044] The difference between this preparation example and Preparation Example 1 is that the calcium hydroxide suspension reacts with the mixed gas at 19°C.

[0045] Preparation Example 4

[0046] The difference between this preparation example and Preparation Example 1 is that the calcium hydroxide suspension reacts with the mixed gas at 18°C.

[0047] Preparation Example 5

[0048] The difference between this preparation example and preparation example 4 is that the concentration of calcium hydroxide in the calcium hydroxide suspension is 1.2 mol / L.

[0049] Preparation Example 6

[0050] The difference between this preparation example and preparation example 4 is that the concentration of calcium hydroxide in the calcium hydroxide suspension is 1.1 mol / L.

[0051] Preparation Example 7

[0052] The difference between this preparation example and preparation example 4 is that the concentration of calcium hydroxide in the calcium hydroxide suspension is 1.0 mol / L.

[0053] Preparation example of modified slag powder

[0054] The following explanation uses Preparation Example 8 as an example.

[0055] Preparation Example 8

[0056] In this preparation example, the modified slag powder was prepared according to the following method:

[0057] Mix 50g of slag powder, 900g of anhydrous ethanol, 350g of water, and 10g of vinyltriethoxysilane. Adjust the pH to 3.5 with 0.1mol / L hydrochloric acid and react for 1h in a water bath at 60℃. Add 150g of acrylic acid and 1g of ammonium persulfate to the resulting mixture and react at 70℃ for 4h. After the reaction is complete, allow it to cool naturally. Filter and dry the product, and then grind it to obtain modified slag powder.

[0058] Preparation Example 9

[0059] The difference between this preparation example and preparation example 8 is that, in the method for preparing modified slag powder, unsaturated fatty acids and acrylic acid are added together to the mixture. The unsaturated fatty acid used is linoleic acid, and the molar ratio of linoleic acid to acrylic acid is 1:20.

[0060] Example

[0061] Examples 1-5

[0062] The following description uses Example 1 as an example.

[0063] Example 1

[0064] In this embodiment, the pH of the landfill leachate membrane concentrate is 7.43, the calcium hardness (calculated as calcium carbonate) is 815.62 mg / L, the magnesium hardness (calculated as magnesium hydroxide) is 459.36 mg / L, the bicarbonate ion concentration is 785.92 mg / L, the chloride ion concentration is 5326 mg / L, and the ammonia nitrogen concentration is 97.62 mg / L. The microfiltration membrane system includes one SMF membrane stack (SMF-8-2; 2500L x 1500W x 2800H, assembly) and two SMF membranes (ZM-6-8, PTFE membrane elements). The membrane fibers are made of PTFE, the membrane shell is made of PP, and the area of ​​a single membrane is 6 m². 2 The nucleation inducing agent is quartz sand with a fineness modulus of 2.7.

[0065] This embodiment provides a landfill leachate membrane concentrate treatment process, including the following steps:

[0066] (1) Prepare a 10 wt% sodium carbonate solution and a 10 wt% sodium hydroxide solution, using 3m 3 The landfill leachate membrane concentrate is transported to the first reaction tank at a rate of / h. First, a prepared sodium carbonate solution and sodium hydroxide solution are added to the first reaction tank at a weight ratio of 1:3 until the pH is adjusted to 10. After stirring, it is then transported at a rate of 3m³ / h. 3 The effluent is discharged into the second reaction tank at a rate of / h;

[0067] (2) Stir the wastewater in the second reaction tank at a rate of 20 r / min for 8 hours, then stop stirring and wait for the sedimentation to separate into layers. Then discharge the clear liquid in the upper layer into the middle tank and the turbid liquid in the middle layer into the sedimentation tank. Pump the sludge in the lower layer into the sludge tank.

[0068] (3) Use a microfiltration membrane to microfilter the clear liquid in the intermediate tank to obtain filtrate, discharge the filtrate into the filtrate tank, and pump the wastewater generated during the periodic cleaning of the microfiltration membrane back to the second reaction tank; coagulate and settle the turbid liquid in the sedimentation tank, and then pump the clear liquid to the intermediate tank; press the sludge in the sludge tank, remove the filter cake, and send the remaining liquid back to the first reaction tank.

[0069] (4) Pump the clarified liquid from the filtrate tank into an electrolysis device with an electrode spacing of 8 cm, and add quartz sand, with a weight equivalent to 5% of the total weight of the filtrate, as a nucleation inducing agent. After energizing, apply 25 A / m 2 The current density is used to electrolyze and soften the clear liquid. After the filtrate stays in the electrolysis device for 20 minutes, the electrolysis ends, thus completing the treatment of the landfill leachate membrane concentrate.

[0070] As shown in Table 1, the main difference between Examples 1-3 is that the wastewater in the first reaction tank is adjusted to different pH values ​​in step (1).

[0071] Table 1 pH of the first reaction tank

[0072] sample Example 1 Example 2 Example 3 pH of the first reaction tank 10 10.5 11

[0073] Example 4

[0074] The difference between this embodiment and Embodiment 3 is that the current density during the electrolytic softening process is 28 A / m. 2 .

[0075] Example 5

[0076] The difference between this embodiment and Embodiment 3 is that the current density during the electrolytic softening process is 31 A / m. 2 .

[0077] Example 6

[0078] The difference between this embodiment and Embodiment 3 is that the current density during the electrolytic softening process is 33 A / m. 2 .

[0079] Example 7

[0080] The difference between this embodiment and Embodiment 6 is that the electrode spacing of the electrolysis device is 6cm.

[0081] Example 8

[0082] The difference between this embodiment and Embodiment 6 is that the electrode spacing of the electrolysis device is 4.5 cm.

[0083] Example 9

[0084] The difference between this embodiment and Embodiment 6 is that the electrode spacing of the electrolysis device is 3cm.

[0085] Example 10

[0086] The difference between this embodiment and Embodiment 9 is that the residence time of the filtrate in the electrolysis device is 30 minutes.

[0087] Example 11

[0088] The difference between this embodiment and Embodiment 9 is that the residence time of the filtrate in the electrolysis device is 45 minutes.

[0089] Example 12

[0090] The difference between this embodiment and Embodiment 9 is that the residence time of the filtrate in the electrolysis device is 60 minutes.

[0091] Example 13

[0092] The difference between this embodiment and Embodiment 12 is that the nucleation inducing agent is garnet sand with a fineness modulus of 2.7.

[0093] Example 14

[0094] The difference between this embodiment and Example 13 is that the nucleation inducing agent also includes calcium carbonate seed crystals, which are prepared according to the method of Preparation Example 1, and the weight ratio of calcium carbonate seed crystals to garnet sand is 1:50.

[0095] As shown in Table 2, the difference between Examples 14-20 is that the preparation methods for calcium carbonate seed crystals are different.

[0096] Table 2 Examples of calcium carbonate seed crystal preparation

[0097] sample Preparation Example Example 14 Preparation Example 1 Example 15 Preparation Example 2 Example 16 Preparation Example 3 Example 17 Preparation Example 4 Example 18 Preparation Example 5 Example 19 Preparation Example 6 Example 20 Preparation Example 7

[0098] Example 21

[0099] The difference between this embodiment and Example 20 is that the nucleation inducing agent also includes modified slag powder, which is prepared according to the method of Preparation Example 8, and the weight ratio of modified slag powder to garnet sand is 1:20.

[0100] Example 22

[0101] The difference between this embodiment and Example 21 is that the modified slag powder is prepared according to the method of Preparation Example 9.

[0102] Comparative Example

[0103] Comparative Example 1

[0104] The difference between this comparative example and Example 1 is that the filtrate is not electrolyzed.

[0105] Comparative Example 2

[0106] The difference between this comparative example and Example 1 is that no nucleation inducing agent is added when electrolyzing the filtrate.

[0107] Performance testing methods

[0108] The total hardness of the filtrate was determined by EDTA titration according to the fourth edition of "Methods for Monitoring and Analysis of Water and Wastewater". The results are shown in Table 3.

[0109] Table 3 Total Hardness

[0110] sample Hardness (mg / L) sample Hardness (mg / L) Example 1 139.12 Example 13 87.44 Example 2 119.38 Example 14 76.32 Example 3 105.45 Example 15 73.25 Example 4 103.85 Example 16 73.08 Example 5 101.62 Example 17 72.71 Example 6 98.38 Example 18 70.34 Example 7 97.41 Example 19 69.88 Example 8 96.89 Example 20 69.42 Example 9 96.06 Example 21 50.39 Example 10 94.34 Example 22 47.68 Example 11 92.17 Comparative Example 1 416.57 Example 12 90.78 Comparative Example 2 178.28

[0111] Combining Example 1 and Comparative Example 1 with Table 3, it can be seen that the hardness of the filtrate in Comparative Example 1 is much higher than that in Example 1. This is because in Example 1, electrolysis causes calcium and magnesium ions to accumulate at the cathode, and under the action of the nucleation inducing agent, precipitates are formed, thus achieving sufficient removal of calcium and magnesium ions. In contrast, Comparative Example 1 did not undergo electrolysis treatment, and simple chemical precipitation alone cannot fully remove calcium and magnesium ions.

[0112] As can be seen from Example 1 and Comparative Example 2, and Table 3, although Comparative Example 2 also underwent electrolysis, the hardness of the filtrate after electrolysis was still higher than that of Example 1. This is because no nucleation inducing agent was added to the filtrate of Comparative Example 2, which could not promote the formation and growth of the precipitate, and therefore could not fully remove the hardness of the filtrate within a limited time.

[0113] As can be seen from Examples 1-22 and Comparative Examples 1-2, and Table 3, after processing according to this application, the landfill leachate membrane concentrate, which originally had a total hardness of over 1,000 mg / L, was transformed into a filtrate with a hardness of less than 150 mg / L, and the treatment efficiency was high. The precipitates formed during the treatment process were collected as sludge, and the final filtrate was less prone to scaling when used in thermal evaporation and reflow incinerator processes, eliminating the need for additional cost and time for scaling removal. This achieved the rational disposal and full utilization of the landfill leachate membrane concentrate.

[0114] As can be seen from Examples 3-6 and Table 3, the total hardness of the filtrate measured in Examples 4-6 is relatively low. This is because, within the current density range corresponding to Examples 4-6, the migration rate of calcium and magnesium ions to the cathode and the generation rate of hydroxide ions are both relatively fast, resulting in the generation of more precipitates in the same amount of time, which helps to quickly reduce the hardness of the filtrate.

[0115] As can be seen from Examples 6-9 and Table 3, the total hardness of the filtrate measured in Examples 7-9 is relatively low. This is because within the electrode spacing range corresponding to Examples 7-9, a strong electric field can be maintained between the electrodes, and due to the close distance, the time spent on ion migration is relatively short, which helps to quickly reduce the hardness of the filtrate.

[0116] As can be seen from Examples 9-12 and Table 3, the total hardness of the filtrate measured in Examples 10-12 is relatively low. This is because, within the time range corresponding to Examples 10-12, the residual calcium and magnesium ions in the filtrate can be fully removed, thereby effectively reducing the hardness of the filtrate.

[0117] As can be seen from Examples 12 and 13 and Table 3, the use of garnet sand can also effectively promote the reduction of hardness during electrolysis.

[0118] As can be seen from Examples 13, 14-20, and Table 3, the total hardness of the filtrate measured in Examples 14-20 was lower. This is because the nano-calcium carbonate seeds can act as nucleation inducing agents to induce the formation of calcium carbonate. Through the synergistic effect of the calcium carbonate seeds and sand particles, calcium and magnesium ions can more fully form precipitates, thereby effectively reducing the hardness of the filtrate. When the calcium hydroxide suspension reacts with the mixed gas at 18-20℃, or when the concentration of calcium hydroxide in the calcium hydroxide suspension is 1.0-1.2 mol / L, the obtained calcium carbonate seeds have a more regular morphology and better dispersion, which can better promote the formation of calcium carbonate and help to significantly reduce the hardness of the filtrate.

[0119] As can be seen from Examples 20 and 21 and Table 3, the total hardness of the filtrate measured in Example 21 is lower. This is because the polycarboxylic acid segments on the surface of the modified slag powder have a strong adsorption effect on calcium and magnesium ions, which can promote the solidification and precipitation of calcium and magnesium ions and help to fully reduce the hardness of the filtrate.

[0120] As can be seen from Examples 21 and 22 and Table 3, the total hardness of the filtrate measured in Example 22 was lower. This is because the long branches introduced by the unsaturated fatty acids can increase the capture range of calcium and magnesium ions by the polycarboxylic acid segments, promote the solidification and precipitation of calcium and magnesium ions, and help to fully reduce the hardness of the filtrate.

[0121] The above embodiments are merely explanations of this application and are not intended to limit it. After reading this specification, those skilled in the art can make modifications to the embodiments of this application without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of this application.

Claims

1. A process for treating a landfill leachate membrane concentrate, characterized in that, The method comprises the following steps: (1) preparing sodium carbonate solution and sodium hydroxide solution, and conveying landfill leachate membrane concentrate to a first reaction tank, and adding the prepared sodium hydroxide solution and sodium carbonate solution into the first reaction tank, adjusting pH to 10-11, and discharging the effluent into a second reaction tank after stirring; (2) stirring the wastewater in the second reaction tank, discharging the supernatant into an intermediate tank after static stratification, discharging the middle turbidity into a sedimentation tank, and pumping the lower sludge into a sludge tank; (3) microfiltering the supernatant in the intermediate tank by using a microfiltration membrane to obtain filtrate, pumping the filtrate into a filtrate tank, pumping the wastewater generated during periodic cleaning of the microfiltration membrane back to the second reaction tank, coagulating and precipitating the turbidity in the sedimentation tank, and then pumping the supernatant into the intermediate tank, and pressure filtering the sludge in the sludge tank, and then pumping the residual liquid back to the first reaction tank after removing the filter cake; (4) pumping the supernatant in the filtrate tank into an electrolytic device, adding a nucleation inducer into the supernatant, electrolyzing the supernatant after power-on to achieve electrolytic softening, and completing the treatment of the landfill leachate membrane concentrate after electrolysis; The nucleation inducer comprises sand, and the sand is quartz sand or garnet sand; The nucleation inducer further comprises calcium carbonate crystal seeds or modified slag powder; The calcium carbonate crystal seeds are prepared by the following method: adding quicklime into hot water for digestion, then standing and aging, and then screening to obtain refined milk of lime, preparing calcium hydroxide suspension by using the refined milk of lime, and introducing a mixed gas of nitrogen and carbon dioxide into the calcium hydroxide suspension, and obtaining calcium carbonate crystal seeds after reaction; The modified slag powder is prepared by the following method: mixing slag powder, anhydrous ethanol, water, vinyl alkoxysilane and hydrochloric acid, and then obtaining slag dispersion liquid after heating reaction, and then adding monomers and initiators into the slag dispersion liquid under water bath heating conditions for reaction, and then naturally cooling after reaction, and then pumping and filtering and drying the product, and then grinding to obtain modified slag powder; the monomers comprise acrylic acid and unsaturated fatty acid.

2. The treatment process of landfill leachate membrane concentrate according to claim 1, characterized in that, In step (4), the current density during the electrolytic softening process is 28-33 A / m 2 .

3. The treatment process of landfill leachate membrane concentrate according to claim 2, characterized in that, In step (4), the distance between the electrode plates of the electrolytic device is 3-6 cm.

4. The treatment process of landfill leachate membrane concentrate according to claim 3, characterized in that, In step (4), the residence time of the filtrate in the electrolytic device is 30-60 min.

5. The treatment process of landfill leachate membrane concentrate according to claim 1, characterized in that, The calcium hydroxide suspension is reacted with the mixed gas at 18-20℃.

6. The treatment process of a landfill leachate membrane concentrate according to claim 5, characterized in that, The concentration of calcium hydroxide in the calcium hydroxide suspension is 1.0-1.2 mol / L.