A method and system for treating raw landfill leachate

Abstract

This invention discloses a method and system for treating landfill leachate stock, belonging to the field of wastewater treatment technology. The method includes the following steps: first, adding an appropriate amount of acid to the landfill leachate and stirring until homogeneous to obtain an acidic solution with a pH value below 1.5; then, adding silicate cement to the acidic solution in one go or in small amounts multiple times, mixing thoroughly, and allowing it to settle until solids precipitate before discharging the liquid to the external environment or transporting it to the next process. The total amount of silicate cement added is 6%-10% of the mass of the acidic solution. This method can simultaneously treat TP, TN, and NH3 in landfill leachate. 3 Removal of -N and COD, TP, TN, NH 3 The removal rate of nitrogen (-N) can reach over 75%, and the COD removal rate can reach over 30%. The levels of recalcitrant organic macromolecules and benzene ring compounds are significantly reduced. The organic matter in the water sample is reduced, and the molecular structures are simpler and smaller, which is beneficial for biological decomposition and utilization. The system has a simple structure, is easy to use, and significantly reduces water treatment costs.

Description

A method and system for treating landfill leachate raw liquid Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method and system for treating raw landfill leachate. Background Technology

[0002] Landfill leachate is a liquid formed when water, organic matter, inorganic salts, and other substances contained in landfills are squeezed out and mixed together after the landfill is compacted. If collected, managed, or treated improperly, or if disposed of unsafely, leachate from landfills can cause serious pollution to groundwater, surface water, and soil.

[0003] As a complex and highly stable wastewater, landfill leachate contains over 60% humic substances as organic carbon. Humic substances are a class of high-molecular-weight organic compounds with complex structures, mainly composed of elements such as carbon, hydrogen, and oxygen, and containing various chemical functional groups, such as carboxylic acids, phenolic hydroxyl groups, and amino groups. As a recalcitrant organic compound, humic substances influence the anaerobic ammonia oxidation process and microbial activity through enzyme systems and the anaerobic ammonia oxidation pathway. The presence of humic substances is the main reason why landfill leachate is not easily reactive, making this type of wastewater difficult to treat and a major challenge in the environmental field.

[0004] Especially for high-concentration landfill leachate, current technologies struggle to directly treat the raw solution, necessitating pretreatment. Currently, the most common treatment method is biological treatment, often combined with multiple physicochemical treatment units at the front end and downstream membrane treatment and advanced oxidation units. However, this combined process suffers from challenges because the physicochemical treatments at the front end do not completely disrupt the stable organic environment of the leachate, which is primarily composed of humic substances. Furthermore, the downstream membrane treatment and advanced oxidation units result in high system costs and energy consumption. Summary of the Invention

[0005] The purpose of this invention is to provide a method for treating high-concentration landfill leachate stock solution. The process is simple, capable of treating high-concentration stock solution, and has high treatment efficiency and low treatment cost.

[0006] The present invention also provides a treatment system for high-concentration landfill leachate stock solution, which has a simple structure, is easy to use, and has a low cost.

[0007] The embodiments of the present invention are implemented as follows:

[0008] The present invention provides a method for treating landfill leachate stock, comprising the following steps:

[0009] S1: Add an appropriate amount of acid to the landfill leachate, stir and mix evenly to obtain an acidic solution with a pH value below 1.5;

[0010] S2: Add silicate cement to the acidic solution in one go or in small amounts multiple times. After each addition of silicate cement, mix thoroughly and let stand until the solid settles. Then discharge the liquid to the external environment or transport it to the next process. The total amount of silicate cement added is 6%-10% of the mass of the acidic solution.

[0011] Preferably, the acid solution in step S1 is concentrated sulfuric acid or hydrochloric acid.

[0012] Preferably, in step S1, the pH value of the acidic solution prepared is 0.2, 0.5, 1.0, 1.09 or 1.5.

[0013] Preferably, in step S2, the total amount of silicate cement added is 6%, 8%, or 10% of the mass of the acidic solution.

[0014] Preferably, in step S2, if silicate cement is added in small amounts multiple times, the amount of silicate cement added each time is 1%-3% of the mass of the acidic solution.

[0015] Preferably, if silicate cement is added in small amounts multiple times, the amount of silicate cement added each time is 2% of the mass of the acidic solution.

[0016] The present invention also provides a treatment system for landfill leachate raw liquid, including an acid treatment container and an alkali treatment container connected by a pipeline; the upper end of the acid treatment container is provided with a waste liquid inlet and an acid addition port, and a pH sensor is provided inside the acid treatment container; the upper end of the alkali treatment container is provided with an alkali addition port, and a drain port is also provided on the alkali treatment container; a first stirrer and a second stirrer are respectively provided inside the acid treatment container and the alkali treatment container.

[0017] Preferably, an acid buffer container is provided between the acid treatment container and the alkali treatment container, and a first metering pump is provided on the pipeline between the acid buffer container and the alkali treatment container.

[0018] Preferably, the alkali treatment container is equipped with a filter screen, the inlet pipe of the alkali treatment container extends into the interior of the filter screen, and the outlet of the alkali treatment container is located outside the filter screen.

[0019] Preferably, there are multiple alkali treatment containers, which are connected in sequence by a pipeline and a second metering pump is provided on the pipeline.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) It can simultaneously remove multiple pollutants from wastewater with significant effects. The method for treating raw landfill leachate provided in this embodiment of the invention first uses acid to adjust the pH of the landfill leachate to below 1.5. Under low pH conditions, a large number of protons (H+) are present, and a large number of carboxylic acids and phenolic groups on the humic substances in the landfill leachate are protonated, reducing the Zeta potential value. The Zeta potential decay can significantly reduce the stability of particle aggregation in the colloidal system of the landfill leachate, thus destabilizing the originally stable organic system. Then, an appropriate amount of silicate cement is added to the acidified landfill leachate, which can simultaneously remove TP, TN, NH3-N and COD from the landfill leachate. The removal rates of TP, TN and NH3-N can all reach more than 75%, and the COD removal rate can reach more than 30%.

[0022] (2) Effective degradation of organic systems in high-concentration landfill leachate raw liquid, solving the problem of extremely low biodegradability of wastewater. The E4 / E6 ratio in the landfill leachate treated by this method increased significantly, reaching up to 43 times that of the raw water; indicating that the aromaticity of the water sample decreased, the degree of aromatic carbon chain condensation decreased, and the number of recalcitrant organic macromolecules and benzene ring substances decreased significantly. The organic matter in the water sample decreased and the molecular structure became simpler and the molecular weight smaller, which is conducive to biological decomposition and utilization.

[0023] (3) The method and process are simple, and the treatment cost and energy consumption are greatly reduced. In addition, the use of concentrated sulfuric acid or hydrochloric acid to adjust the pH of landfill leachate can greatly reduce the cost of acid.

[0024] The landfill leachate raw liquid treatment system provided by the embodiments of the present invention has a simple structure and is easy to use. It can set reasonable acid and alkali addition amounts, treatment retention time and stirring speed according to the water quality of different regions or environments to ensure the best treatment effect. The treatment system can effectively degrade macromolecular organic matter in landfill leachate and significantly reduce indicators such as COD, TN, NH3-N, and TP. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 is a schematic diagram of the structure of the landfill leachate raw liquid treatment system provided in an embodiment of the present invention;

[0027] In the diagram: 10-Acid treatment container; 11-Waste liquid inlet; 12-Acid addition port; 13-First stirrer; 14-pH sensor; 15-Valve; 20-Alkali treatment container; 21-Alkali addition port; 22-Second stirrer; 23-Filter screen; 24-First metering pump; 25-Second metering pump; 30-Acid buffer container. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0031] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0032] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0033] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; or they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] Example 1

[0035] Referring to Figure 1, Embodiment 1 of the present invention provides a treatment system for landfill leachate raw liquid, including an acid treatment container 10 and an alkali treatment container 20.

[0036] The acid treatment container 10 has a waste liquid inlet 11 on the upper side wall and an acid addition port 12 on the top. The acid treatment container 10 is equipped with a first stirrer 13 and a pH sensor 14. The acid treatment container 10 has an acid liquid outlet at the lower end and a valve 15 at the acid liquid outlet. The valve 15 can be a solenoid valve. The valve 15 and the pH sensor 14 can be connected through a controller.

[0037] Landfill leachate flows into acid treatment container 10 from waste liquid inlet 11. Then, strong acids such as sulfuric acid or hydrochloric acid are added through acid addition port 12, and the first stirrer 13 is started to stir and mix it thoroughly. The pH value is generally adjusted to 0.2-1.5. Strong acids are added as needed. When the pH value reaches the required acidity, the pH sensor 14 sends a signal to the controller. Then, the controller controls the valve 15 to open, and the acid-treated waste liquid is discharged from the acid outlet.

[0038] An acid buffer container 30 is located below the acid treatment container 10, and the acid discharged from the acid outlet flows into the acid buffer container 30. Alternatively, the acid buffer container 30 can be placed not below the acid treatment container 10, but side-by-side or at a higher position. The acid treatment container 10 and the acid buffer container 30 are connected by a pipe, and a pump then transfers the solution from the acid treatment container 10 to the acid buffer container 30. The acid buffer container 30 ensures uniform and stable subsequent drainage.

[0039] The alkali treatment container 20 has an alkali inlet 21 at its upper end and a drain outlet on its upper side wall. A second stirrer 22 is installed inside the container. A filter screen 23, made of non-woven fabric or fiberglass cloth, is also installed inside the alkali treatment container 20. The filter screen 23 can be made into a mesh bag structure and then placed inside the alkali treatment container 20. The alkali treatment container 20 is connected to the acid buffer container 30 via a pipe. A first metering pump 24 is installed on the pipe. One end of the pipe connects to the inside of the acid buffer container 30 from the bottom or near the bottom side wall, and the other end connects to the inside of the alkali treatment container 20. The pipe opening extends into the filter screen 23, and the lower end of the alkali inlet 21 also extends into the filter screen 23. The stirring blades of the second stirrer 22 are also located inside the filter screen 23. In this way, the first metering pump 24 transports the acid in the acid buffer container 30 to the alkali treatment container 20, and then adds alkaline raw materials through the alkali inlet 21. In this embodiment, silicate cement is selected as the alkaline raw material. The mixture is stirred and mixed evenly by the second stirrer 22 to fully react. The blocky precipitate formed by the reaction of silicate cement in the alkali treatment container 20 can adhere to the filter screen 23. This not only facilitates the periodic cleaning of the precipitate, but also the accumulation and adhesion of alkaline material blocky substances, combined with the filtering effect of the filter screen 23, can further purify the effluent quality of this stage of treatment container. In addition, the accumulation and adhesion of alkaline blocky substances can continuously supply alkali, which is beneficial to reduce the amount of alkaline material used during operation, improve utilization efficiency, and reduce treatment costs.

[0040] Of course, the alkali treatment container 20 can be directly connected to the acid treatment container 10, so that the solution after acid treatment in the acid treatment container 10 can be directly transported into the alkali treatment container 20 for treatment.

[0041] There can be multiple alkali treatment containers 20, which are connected in sequence by pipelines and equipped with a second metering pump 25.

[0042] The landfill leachate treatment system provided by this invention can effectively degrade macromolecular organic matter in landfill leachate, significantly reducing indicators such as COD, TN, NH3-N, and TP, and achieving a nitrogen and phosphorus removal rate of over 75%.

[0043] Example 2

[0044] Embodiment 2 of the present invention provides a method for treating landfill leachate stock, comprising the following steps:

[0045] S1: Add an appropriate amount of acid to the landfill leachate, stir and mix evenly to obtain an acidic solution with a pH value below 1.5.

[0046] In this step, the acid solution can be concentrated sulfuric acid or hydrochloric acid, with concentrated sulfuric acid being preferred.

[0047] In this step, the pH value of the prepared acidic solution can be 0.2, 0.5, 0.8, 1.0, 1.09, 1.2 or 1.5, etc., and should be adjusted according to the actual situation to ensure that the pH value after acidification is below 1.5. It is preferred that the pH value of the acidic solution be adjusted to around 1.0.

[0048] S2: Add silicate cement to the acidic solution in one go or in small amounts multiple times. After each addition of silicate cement, mix thoroughly and let stand until the solid settles. Then discharge the liquid to the external environment or transport it to the next process. The total amount of silicate cement added is 6%-10% of the mass of the acidic solution.

[0049] In this step, if silicate cement is added all at once, the amount of silicate cement added can be 6%, 7%, 8%, 9% or 10% of the mass of the acidic solution, preferably around 8%.

[0050] In this step, if silicate cement is added in small amounts multiple times, the amount of silicate cement added each time should be about 1.5%-3% of the mass of the acidic solution, preferably about 2% of the mass of the acidic solution each time, and the total amount added should be 6%, 7%, 8%, 9% or 10% of the mass of the acidic solution, etc.

[0051] The specific experiment is as follows:

[0052] (I) Take an appropriate amount of fresh landfill leachate raw water (pH 8.51) and divide it into several equal portions, numbered A1-A12. Then, A1 is left untreated, and an appropriate amount of concentrated sulfuric acid is added to each of the remaining portions to adjust the pH value of the landfill leachate in A2-A12 to 8.00, 7.00, 6.00, 5.00, 4.00, 3.00, 2.00, 1.80, 1.60, 1.50, and 1.00, respectively. After standing for 24 hours, the water quality indicators are tested. The test items include total phosphorus content (TP), total nitrogen content (TN), ammonia nitrogen content (NH3-N), and chemical oxygen demand (COD). The test results are shown in Table 1. Then, ordinary silicate cement was added to each water sample. The amount of ordinary silicate cement added was 10% of the solution mass, and it was added all at once. Then, the sample was stirred with a magnetic stirrer at 800 r / min for 30 min. After standing for 24 hours, the water quality indicators were measured. The results are shown in Table 2.

[0053] Table 1 Water quality indicators after acidification treatment

[0054]

[0055] Table 2 Water quality indicators after treatment with added ordinary silicate cement

[0056]

[0057] Analysis of the test results in Tables 1 and 2 shows that after adjusting the raw leachate to different pH values, adding ordinary silicate cement when the pH value is greater than 3.00 has no significant effect on the removal of pollutants in the leachate. When the pH value is between 1.60 and 2.00, adding ordinary silicate cement increases the removal efficiency of TN and NH3-N, with TN removal rates of 66.40%-70.02% and NH3-N removal rates of 64.70%-70.60%. When the pH value is below 1.50, the removal efficiency of TN and NH3-N increases significantly, with both TN and NH3-N removal rates exceeding 80%.

[0058] (II) Take an appropriate amount of fresh landfill leachate (pH 8.45) and divide it into several equal portions, numbered B1-B5. B1 is left untreated. Add an appropriate amount of concentrated sulfuric acid to each of the remaining portions to adjust the pH of the leachate in B2-B5 to 1.50, 1.00, 0.50, and 0.20, respectively. Test the water quality indicators for each portion, including total phosphorus (TP), total nitrogen (TN), ammonia nitrogen (NH3-N), and chemical oxygen demand (COD). The test results are shown in Table 3. Then, add... Ordinary silicate cement was added to water samples 1-B5 in small amounts multiple times. Each addition of ordinary silicate cement was 2% of the solution mass, with a cumulative addition of 10%. After each addition, the sample was stirred at 800 r / min for 10 minutes and allowed to stand for 15 minutes. The pH of the water sample was then measured before the next addition. The pH measurement results are shown in Table 4. Finally, the water sample after the last addition of silicate cement (i.e., the cumulative addition of silicate cement was 10.0%) was taken for water quality analysis. The test results are shown in Table 5.

[0059] Table 3

[0060]

[0061] Table 4

[0062] Water sample pH B1 B2 B3 B4 B5 No cement added 8.45 1.51 1.03 0.55 0.20 First addition 2.0%, cumulative 2.0% 8.57 8.31 8.03 1.74 0.97 Second addition 2.0%, cumulative 4.0% 8.87 8.77 8.11 3.52 1.56 Third addition 2.0%, cumulative 6.0% 8.85 9.86 9.63 8.68 2.84 Fourth addition 2.0%, cumulative 8.0% 8.89 11.22 11.02 11.50 6.88 Fifth addition 2.0%, cumulative 10.0% 8.92 12.21 11.76 11.99 9.39 surface

[0063] Table 5

[0064]

[0065] The test results in Table 3 show that adjusting the pH of the water sample alone increased the levels of TP, TN, and ammonia nitrogen, indicating that acidification alone cannot improve water quality and may even increase these levels.

[0066] The test results in Table 4 show that the pH value of the untreated water sample remained essentially unchanged after adding ordinary silicate cement; however, the pH value of the treated water sample gradually increased after adding ordinary silicate cement. This indicates that the pollutant system in the raw landfill leachate is stable, and adding only alkaline material like ordinary silicate cement cannot change the acidity or alkalinity of the water sample. In contrast, the water sample treated with acidity exhibits an imbalance of pollutants, and the addition of alkaline material like silicate cement can trigger an acid-base reaction, altering the pH of the water sample.

[0067] Table 5 shows that the removal efficiency of various water quality indicators was poor in the untreated water sample after adding ordinary silicate cement. However, significant changes in water quality indicators occurred after adding ordinary silicate cement to the acidified water sample. Specifically, the pollutant removal rate was best when the pH was adjusted to 1.00, with TP removal reaching 87.06%, TN removal reaching 79.19%, NH3-N removal reaching 82.20%, and COD removal reaching 38.77%.

[0068] (III) Randomly take a sample of fresh landfill leachate (pH 8.45), add an appropriate amount of concentrated sulfuric acid, and measure the pH value of the landfill leachate to be 1.09; then divide it into 6 equal portions, numbered C1-C6. No ordinary silicate cement is added to C1, and 2.0%, 4.0%, 6.0%, 8.0%, and 10.0% ordinary silicate cement are added to C2-C5 respectively. Stir the mixture on a magnetic stirrer at 600 r / min for 30 minutes, let it stand for 2 days, and measure the water quality indicators. The test results are shown in Table 6.

[0069] Table 6

[0070]

[0071]

[0072] As shown in Table 6, adjusting the pH of the landfill leachate raw water to below 1.5 and then adding different proportions of alkaline ordinary silicate cement resulted in a corresponding increase in pollutant removal efficiency as the cement content increased. In particular, when the cement content reached 6.0% or higher, the TP removal rate reached over 87%, the TN removal rate over 78%, the ammonia nitrogen removal rate over 81%, and the COD removal rate over 32%.

[0073] (iv) Only concentrated sulfuric acid was added to fresh landfill leachate and landfill leachate stored for different times, and the pH of the landfill leachate was adjusted to below 1.5. After standing for 24 hours, the water quality was tested and analyzed. The results are shown in Table 7.

[0074] Table 7

[0075]

[0076] As shown in Table 7, for landfill leachate aged in different years, acidification treatment alone did not significantly remove TP, TN, ammonia nitrogen and COD from the water samples.

[0077] (V) Take an appropriate amount of fresh landfill leachate raw water (pH 8.45) and divide it into several equal portions, numbered D1-D6. Then, D1 is left untreated, and 2.0%, 4.0%, 6.0%, 8.0% and 10.0% of ordinary silicate cement by mass of solution are added to D2-D6 respectively. Stir the mixture on a magnetic stirrer at 600 r / min for 30 minutes, let it stand for 2 days, and measure the water quality indicators. The test results are shown in Table 8.

[0078] Table 8

[0079]

[0080] As can be seen from the data in Table 8, adding ordinary silicate cement to landfill leachate alone does not significantly remove TP, TN, ammonia nitrogen, and COD from the water sample.

[0081] (vi) Add concentrated sulfuric acid to the landfill leachate to lower the pH of the water sample to below 1.5. After the acid adjustment is completed, the pH is measured at different standing times. The results are shown in Table 9.

[0082] Table 9

[0083]

[0084] As can be seen from Table 9, after acidification treatment of landfill leachate, the pH value of the leachate will change when exposed to air. This is because the leachate will react when exposed to air for a long time, so the change in pH value is a normal phenomenon.

[0085] (vii) UV 254 The test involved UV-curing the solution from the original water sample after treatment with only ordinary silicate cement. 254 Detection, and UV testing of solutions from acid-treated water samples after treatment with ordinary silicate cement. 254 The test results are shown in Table 10.

[0086] Table 10

[0087]

[0088] As shown in Table 10, the E4 / E6 ratio did not change significantly in the untreated water sample after treatment with ordinary silicate cement. However, the E4 / E6 ratio in the landfill leachate treated with ordinary silicate cement after acidification increased significantly, reaching a maximum of 43 times that of the original water. This indicates a decrease in the aromaticity and degree of aromatic carbon chain condensation in the water sample, a significant reduction in recalcitrant organic macromolecules and benzene ring substances, and a decrease in organic matter with simpler molecular structures and smaller molecular weights, which is beneficial for biological decomposition and utilization.

[0089] (viii) Commonly used strong acids were selected for experimental analysis to determine their cost and impact on water quality. Concentrated sulfuric acid, hydrochloric acid and phosphoric acid were selected for experimental analysis in this experiment.

[0090] (a) Cost analysis using acid

[0091] Phosphoric acid was used to adjust the pH of landfill leachate. The dosages used to adjust the pH of the original solution (8.00) to 1.50, 1.00, 0.50, and 0.20 were 2.63%, 7.33%, 21.17%, and 37.17%, respectively. Based on a phosphoric acid price of 4,500 yuan / ton, the acid cost for treating 1 ton of landfill leachate to a pH of 1.50, 1.00, 0.50, and 0.02 were 118.35 yuan, 329.85 yuan, 925.65 yuan, and 1,672.65 yuan, respectively.

[0092] The amounts of sulfuric acid used to adjust the pH of landfill leachate from 8.00 to 1.5, 1.0, 0.5, and 0.2 were 0.36%, 0.92%, 2.95%, and 5.28%, respectively. Based on a sulfuric acid price of 1000 yuan / ton, the acid costs for treating 1 ton of landfill leachate to pH 1.50, 1.00, 0.50, and 0.20 were 3.60, 9.20, 29.50, and 52.80 yuan, respectively.

[0093] The leachate was adjusted with hydrochloric acid (laboratory concentration 36.46%). The amounts of hydrochloric acid used to adjust the pH of the original solution (pH 8.00) to 1.50, 1.82%, 5.32%, and 11.02% were 1.05%, 1.82%, 5.32%, and 11.02%, respectively. Based on a price of 400 yuan / ton for 31% dilute hydrochloric acid and a conversion factor of 1.2 times for each concentration difference, the acid cost for treating 1 ton of original leachate to pH 1.50, 1.00, 0.50, and 0.02 were 5.04, 8.74, 25.54, and 52.90 yuan, respectively.

[0094] Therefore, it is more cost-effective to use sulfuric acid and hydrochloric acid to adjust the acidity of landfill leachate.

[0095] (b) Take an appropriate amount of landfill leachate, determine the TP content of the original water sample, then divide it into three portions, add concentrated sulfuric acid, hydrochloric acid, and phosphoric acid respectively, adjust the pH to 0.2, and determine the TP content in the water sample after acidification treatment. The results are shown in Table 11. Then, add ordinary silicate cement to the three acidified water samples in small amounts multiple times. The amount of ordinary silicate cement added each time is 2% of the solution mass, and the cumulative amount added is 10%. The pH is measured, and the results are shown in Table 12.

[0096] Table 11

[0097] TP (mg / L): Raw water 9.29, adjusted to 0.20 with phosphoric acid; 129608.00, adjusted to 0.20 with sulfuric acid; 1.10, adjusted to 0.20 with hydrochloric acid; 0.86. surface

[0098] As can be seen from Table 11, the TP content in the water sample increased significantly after acidification treatment with phosphoric acid, which made TP removal more difficult and increased the cost of subsequent TP treatment.

[0099] Table 12

[0100]

[0101] Table 12 shows that after adjusting the water sample to 0.2 with phosphoric acid and then adding cement, the pH only increased to 0.60 when the cement content reached 10.0%. After adjusting the water sample to 0.2 with sulfuric acid and hydrochloric acid respectively, the pH increased to 8.37 and 10.78 when the cement content was 10.0%, respectively. Therefore, if phosphoric acid is used for acidification, more ordinary silicate cement is needed to adjust the pH back to alkaline conditions for subsequent alkali treatment; this results in high alkali costs and a significant increase in precipitation.

[0102] Therefore, concentrated sulfuric acid and hydrochloric acid are preferred for acidification treatment of landfill leachate.

[0103] This invention is not limited to the above-described optional embodiments. Anyone can derive other various forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that falls within the scope of the claims of this invention shall be protected by this invention.

Claims

1. A method for treating landfill leachate stock, characterized in that: The process includes the following steps: S1: Add an appropriate amount of acid to the landfill leachate, stir and mix evenly to obtain an acidic solution with a pH value below 1.

5. The acid in step S1 is concentrated sulfuric acid or hydrochloric acid. S2: Add silicate cement to the acidic solution in one go or in small amounts multiple times. After each addition of silicate cement, mix thoroughly, let stand until the solid precipitates, and then discharge the liquid into the external environment or transport it to the next process. The total amount of silicate cement added is 6%-10% of the mass of the acidic solution.

2. The method for treating landfill leachate stock solution according to claim 1, characterized in that: In step S1, the pH value of the acidic solution prepared is 0.2, 0.5, 1.0, 1.09, or 1.

5.

3. The method for treating landfill leachate stock solution according to claim 1, characterized in that: In step S2, the total amount of silicate cement added is 6%, 8%, or 10% of the mass of the acidic solution.

4. The method for treating landfill leachate stock solution according to claim 1, characterized in that: In step S2, if silicate cement is added in small amounts multiple times, the amount of silicate cement added each time should be 1%-3% of the mass of the acidic solution.

5. The method for treating landfill leachate stock solution according to claim 4, characterized in that: If silicate cement is added in small amounts multiple times, the amount of silicate cement added each time should be 2% of the mass of the acidic solution.

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