A method for treating landfill leachate

Abstract

The present application relates to the field of sewage treatment, and specifically discloses a method for treating landfill leachate, comprising the following steps: S1 primary sedimentation, adjustment, anaerobic treatment, water quality equalization, and adsorption treatment, wherein the obtained homogeneous landfill leachate is added with 0.3-1.5 kg / L landfill leachate treatment agent for treatment, and then subjected to membrane treatment and deep oxidation to obtain discharge water meeting water quality standards; the landfill leachate treated by the landfill leachate treatment method of the present application has a maximum COD removal rate, a mercury ion removal rate, a cadmium ion removal rate, ammonia nitrogen removal rate, and suspended solids removal rate of 96.83%, 99.11%, 99.20%, 99.05%, and 95.65%, respectively, showing a high treatment effect.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and more specifically, to a method for treating landfill leachate. Background Art

[0002] Under my country's current economic and technological conditions, the main methods for treating domestic waste are sanitary landfill, incineration, and composting. During the domestic waste treatment process, due to its high water content and high organic content, microbial decomposition and natural precipitation produce a dark brown wastewater called leachate, which is characterized by foul-smelling waste gases and contains volatile organic compounds. This leachate typically contains high concentrations of difficult-to-degrade organic wastewater, posing a serious threat to the ecological environment and human health.

[0003] Landfill leachate mainly consists of four parts: (1) water in the garbage itself; (2) water produced by the decomposition of organic matter in the garbage by microorganisms; (3) natural precipitation; and (4) water that seeps into the landfill area through surface runoff. Studies have found that the quality of landfill leachate is affected by factors such as the time of landfilling, the nature of the garbage itself, and the garbage treatment technology. The water quality is characterized by complex composition, high levels of heavy metals, organic pollutants, and ammonia nitrogen, a foul odor, high color, an imbalance in the ratio of microbial nutrients, and difficulty in treatment.

[0004] In related technologies, oxidation processes are used to oxidize and decompose non-biodegradable organic matter in sewage, such as Fenton oxidation and ozone oxidation, which have the characteristics of strong oxidizing ability and fast reaction speed. However, in actual applications, due to the complex composition of pollutants in leachate, the treated leachate has problems such as high ammonia nitrogen content, high suspended solids content, high heavy metal ion content, and high chemical oxygen demand, which makes it difficult to meet actual needs. Summary of the Invention

[0005] In order to improve the treatment effect of landfill leachate, the present application provides a landfill leachate treatment method.

[0006] In a first aspect, the present application provides a method for treating landfill leachate, which adopts the following technical solution:

[0007] A method for treating landfill leachate comprises the following steps:

[0008] S1: Primary sedimentation: The landfill leachate is subjected to primary sedimentation, mixing and removal of filter residue to obtain primary sedimentation landfill leachate;

[0009] S2 regulation: adjusting the water volume of the primary landfill leachate obtained in S1 and removing the generated odor to obtain regulated landfill leachate;

[0010] S3 anaerobic treatment: the regulated landfill leachate obtained in S2 is anaerobically mixed to form suspended sludge to obtain anaerobic landfill leachate;

[0011] S4 water quality balance: the anaerobic landfill leachate obtained in S3 is subjected to water quality balance and stirring to obtain homogeneous landfill leachate;

[0012] S5 adsorption treatment: adding 0.3-1.5 kg / L of landfill leachate treatment agent to the homogenized landfill leachate obtained in S4 to obtain adsorbed landfill leachate;

[0013] S6 membrane treatment: the adsorbed landfill leachate obtained in S5 is treated with a concentrated membrane and degraded to obtain membrane-treated landfill leachate;

[0014] S7 deep oxidation: The membrane-treated landfill leachate obtained in S6 is subjected to ozone oxidation treatment to obtain discharge water with water quality that meets the standards. By adopting the above technical solution, S1 subjects the landfill leachate to primary sedimentation, mixing and defiltration to obtain primary sedimentation landfill leachate, and at the same time removes the generated odor to obtain regulated landfill leachate; the regulated landfill leachate is subjected to anaerobically mixed to fully mix the upper activated sludge with the lower sludge to form a suspended sludge layer to obtain anaerobic landfill leachate; the anaerobic landfill leachate is subjected to water quality equalization and stirring to obtain homogeneous landfill leachate with COD balance; the homogeneous landfill leachate is treated with 0.3-1.5kg / L landfill leachate treatment agent to remove organic matter and heavy metal ions in the homogeneous landfill leachate to obtain adsorption landfill leachate; the adsorption landfill leachate is subjected to concentration membrane treatment to degrade inorganic matter to obtain membrane-treated landfill leachate; the membrane-treated landfill leachate is subjected to ozone oxidation treatment to further remove organic pollutants in the membrane-treated landfill leachate to obtain discharge water with water quality that meets the standards.

[0015] Preferably, the landfill leachate treatment agent comprises the following raw materials in parts by weight: 150-300 parts of biochar, 50-100 parts of defoaming agent, 100-300 parts of sodium alginate modified with L-cysteine and amino-terminated hyperbranched polymer, 50-150 parts of polysilicate titanium iron salt, and 2-10 parts of water.

[0016] The landfill leachate treatment agent of the present application comprises the following raw materials in parts by weight: 150-300 parts of biochar, 50-100 parts of defoaming agent, 100-300 parts of sodium alginate modified with L-cysteine and amino-terminated hyperbranched polymer, and 50-150 parts of polysilicate titanium iron salt. The raw materials can be selected at any value within their respective ranges, and the treatment effect of landfill leachate can be improved.

[0017] Biochar is a kind of high aromatic hydrocarbon material with advantages such as large specific surface area, developed pores and rich carbon. Biochar is porous and loose and contains a large number of functional groups on the surface. It has excellent adsorption performance and high cost performance. It can effectively remove chemical oxygen demand (COD) and heavy metal ions in wastewater. First, biochar adsorbs ionic organic compounds and ionizable organic compounds in wastewater, and forms charged groups after functional groups gain and lose electrons to achieve the removal effect; second, it uses the acidic surface functional groups such as carboxyl and phenolic hydroxyl groups on the surface of biochar and reacts with related reactions to increase the surface electronegativity of biochar, thereby NH4 + The cations obtain more binding sites, achieving the ammonia nitrogen adsorption effect; thirdly, the molecular force of biochar adsorbs the ammonia nitrogen pollutants; and the different pore sizes (micropores, mesopores, macropores) of the pore structure adsorb organic pollutants into the biochar, quickly achieving the ammonia nitrogen adsorption effect.

[0018] Defoamers can rapidly reduce the surface tension of the gas and liquid phases, causing foam to expand rapidly and suppressing it over a long period of time. They can effectively destroy and remove foam, suppressing its formation over a long period of time, and effectively controlling the liquid level in the biochemical pool to prevent leachate from overflowing.

[0019] Cysteine (L-cys) is a common non-essential amino acid in the human body, containing a carboxyl group (-COOH), an amino group (-NH2), and a sulfhydryl group (-SH). L-cys can not only undergo electrostatic adsorption with protonated amine groups in wastewater, but also is a harmless and highly effective amino acid reducing agent. The reducing (-SH) group of L-Cys can reduce and adsorb metal ions, thereby improving the treatment effect of landfill leachate.

[0020] Hyperbranched polymers can be dissolved in a variety of solvents, have low viscosity, have micellar properties, are easily soluble in water, and have a large number of active groups on the surface. They can coat and complex heavy metal ions. Their end groups are amino groups, which improve the ability of the polymer to bind to heavy metals and can improve the treatment effect of landfill leachate.

[0021] Sodium alginate not only has a large number of adsorption sites in its molecular structure, but also has excellent biocompatibility, renewability, high mechanical strength and other advantages. It can also form a gel that is easy to separate from wastewater. However, the adsorption capacity of sodium alginate is limited. After covalent cross-linking with amino-terminated hyperbranched polymers, a large number of active groups can be added to promote the binding with heavy metals. At the same time, L-Cys and the carboxyl (-COOH), amino (-NH2) and thiol (-SH) groups in the molecule can produce strong hydrogen bonds within the sodium alginate molecule, making L-Cys evenly distributed in the sodium alginate structure. The two work together to improve the treatment effect of landfill leachate.

[0022] Polysilicate titanium iron salt, polysilicate mainly bonds with insoluble particles in landfill leachate by adsorption bridging and net-capturing sweeping effects. As the degree of polymerization increases, its structure develops towards a network trend. Iron and titanium metal cations can also increase the storage time of polysilicate titanium iron salt, making it play a better role. Moreover, polysilicate titanium iron salt not only has adsorption bridging ability, but also enhances the flocculation function with the help of the electrical neutralization ability of iron and titanium metal cations. Among them, titanium ions have a good removal effect on organic matter, iron ions have good turbidity removal ability and good floc density and sedimentation effect, and can also reduce the cost problem caused by titanium salts, so that polysilicate titanium iron salt improves the treatment effect of landfill leachate.

[0023] Preferably, the sodium alginate modified by L-cysteine and the amino-terminated hyperbranched polymer comprises the following raw materials, based on the weight of the sodium alginate modified by L-cysteine and the amino-terminated hyperbranched polymer: 5-10 parts of L-cysteine, 15-25 parts of sodium alginate, 5-10 parts of amino-terminated hyperbranched polymer, 16-20 parts of calcium carbonate, 5-15 parts of water, and 6-10 parts of gluconolactone; 5-15 parts of gluconolactone.

[0024] Preferably, the sodium alginate modified with L-cysteine and the amino-terminated hyperbranched polymer is obtained by the following steps:

[0025] S1. Add L-cysteine to water and stir evenly, then add sodium alginate and stir evenly to obtain L-cysteine modified hydrosol;

[0026] S2. Add the hyperbranched polymer to the sodium alginate hydrosol obtained in step S1, stir for 1-5 hours, add gluconolactone and calcium carbonate, and stir at 20-30° C. for 5-10 hours to obtain an L-cysteine-modified sodium alginate and hyperbranched polymer gel.

[0027] By adopting the above technical solution, L-cysteine is added into water and stirred evenly, and then sodium alginate is added and stirred evenly to obtain L-cysteine modified hydrosol, L-Cys generates a strong hydrogen bond effect inside the sodium alginate molecule, so that L-Cys is evenly distributed in the sodium alginate structure; hyperbranched polymer is added and stirred for 1-5 hours, gluconolactone and calcium carbonate are added, and stirred at 20-30°C for 5-10 hours, and Ca carbonate is added. 2+ As a cross-linking agent for sodium alginate, it + By reacting with gluconolactone to form a dense cross-linked network structure, the Ca-EDTA chelate can be distributed throughout the sodium alginate solution before the calcium ions are released. It can also adjust the calcium ion release rate to make the gel uniform, thereby obtaining sodium alginate modified with L-cysteine and terminal amino hyperbranched polymer.

[0028] Preferably, the weight ratio of the L-cysteine, sodium alginate, and amino-terminated hyperbranched polymer is 1:(2-2.5):(0.8-1).

[0029] By adopting the above technical solution, L-cysteine, sodium alginate, and terminal amino groups are controlled.

[0030] The weight ratio of the branched polymer can further improve the treatment effect of landfill leachate.

[0031] Preferably, the weight ratio of the gluconolactone and calcium carbonate is 1:(2.25-2.5).

[0032] By adopting the above technical solution and adjusting the weight ratio of gluconolactone and calcium carbonate, the treatment effect of landfill leachate can be further improved.

[0033] Preferably, the biochar comprises 20-40 wt% of sludge-based biochar and 50-80 wt% of plant-based biochar.

[0034] By adopting the above technical solution, sludge-based biochar has a good adsorption effect on heavy metal ions in landfill leachate, which can improve the removal rate of heavy metal ions; plant-based biochar has a good adsorption effect on COD, NH4 + The removal effect of -N, NO2-N, TN, aromatic and difficult-to-degrade organic matter with double bonds is obvious. The combined effect of the two can improve the treatment effect of landfill leachate.

[0035] Preferably, the raw materials of the landfill leachate treating agent further include 50-100 parts by weight of polyacrylamide and 10-30 parts by weight of carboxymethyl starch.

[0036] By adopting the above technical solution, polyacrylamide exhibits the advantages of long molecular chains, low dosage, and excellent flocculation effect, resulting in excellent performance in turbidity removal, decolorization, and adsorption. While polysilicate titanium iron salt has strong adsorption and charge neutralization capabilities, its low molecular weight limits its ability to bond between colloidal particles during the flocculation process. Relying solely on sweeping flocculation requires a large dosage. Due to its large molecular weight and long molecular chains, polyacrylamide primarily flocculates through adsorption and bridging. The active groups on the chains adsorb colloidal particles through hydrogen bonds, electrostatic bonding, and van der Waals forces, and the entire polymer chain then acts as a bridge. Therefore, by combining polysilicate titanium iron salt with polyacrylamide, the adsorption and charge neutralization properties of the polysilicate titanium iron salt are combined with the bonding and bridging properties of the polyacrylamide. The addition of a carboxymethyl starch coagulant aid accelerates the growth of the titanium iron salt flocs, enhancing their shear resistance and regeneration recovery. Together, polyacrylamide and carboxymethyl starch promote the flocculation of the titanium iron salt, improving the treatment of landfill leachate.

[0037] Preferably, the weight ratio of the polyacrylamide and carboxymethyl starch is (3-4):1.

[0038] By adopting the above technical solution and controlling the weight ratio of polyacrylamide and carboxymethyl starch to (3-4):1, the flocculation effect of polysilicate titanium iron salt can be further promoted, thereby improving the treatment effect of landfill leachate.

[0039] Preferably, the landfill leachate treating agent is prepared by the following steps: mixing and dissolving water and polysilicate titanium iron salt; then adding biochar, L-cysteine and amino-terminated hyperbranched polymer to jointly modify sodium alginate and defoaming agent and other admixtures, and mixing and stirring evenly to obtain the landfill leachate treating agent.

[0040] In summary, this application includes at least one of the following beneficial technical effects:

[0041] (1) The COD removal rate, mercury ion removal rate, cadmium ion removal rate, ammonia nitrogen removal rate and suspended solids removal rate of the water treated by the landfill leachate treatment method of the present application are as high as 96.83%, 99.11%, 99.20%, 99.05% and 95.65%, respectively, which has a high treatment effect.

[0042] (2) By incorporating L-cysteine-modified sodium alginate and a hyperbranched polymer and controlling the weight ratio of L-cysteine, sodium alginate, and amino-terminated hyperbranched polymer, the present application achieves a COD removal rate, a mercury ion removal rate, a cadmium ion removal rate, and an ammonia nitrogen removal rate of water treated by the landfill leachate treatment method of 91.51-93.79%, 95.97-97.32%, 96.41-97.60%, and 95.71-97.41%, respectively, significantly improving the treatment effect of landfill leachate.

[0043] (3) The present application improves the treatment effect of landfill leachate by adding polyacrylamide and carboxymethyl starch into the raw materials and controlling the weight ratio of polyacrylamide and carboxymethyl starch, so that the COD removal rate, mercury ion removal rate, cadmium ion removal rate, ammonia nitrogen removal rate and suspended solids removal rate of water after the landfill leachate treatment method are 88.93-90.45%, 94.45-95.35%, 95.05-95.85%, 94.09-95.04% and 93.68-95.04%, respectively.

[0044] (4) In this application, by adding sludge-based biochar and plant-based biochar to the biochar in the raw material, the COD removal rate, mercury ion removal rate, cadmium ion removal rate, ammonia nitrogen removal rate and suspended solids removal rate of the water treated by the landfill leachate treatment method are 86.19%, 92.84%, 93.61%, 92.37% and 87.75% respectively, thereby improving the treatment effect of landfill leachate. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Flowchart of the processing method provided in this application. DETAILED DESCRIPTION

[0046] The present application is further described in detail below with reference to specific embodiments.

[0047] The following raw materials in this application are all commercially available products. They are provided to fully disclose the raw materials in this application and should not be construed as limiting the sources of the raw materials. Specifically:

[0048] L-cysteine, active substance content 99%; sodium alginate, active substance content 99%

[0049] The terminal hydroxy hyperbranched polymer is selected from terminal hydroxy hyperbranched polyurethane with a content of ≥95%; gluconolactone has a density of 0.6, a melting point of 160°C, and a water solubility of 500g / L (20°C); biochar, plant biochar, is selected from coconut shell biochar with a particle size of 6-12 mesh and a moisture content of 5-10%; sludge biochar has a particle size of 200-325 mesh and a moisture content of ≤5%; the defoamer is selected from water-based polyether modified silicon with an effective substance content of 60-99% and industrial grade; polysilicate titanium iron salt; and the polyacrylamide is selected from cationic polyacrylamide with a molecular weight of 8 million and an effective substance content of 99%; carboxymethyl starch has a content of ≥99% and a density of 2.3g / cm 3 .

[0050] The following is an example of the preparation of sodium alginate modified with L-cysteine and amino-terminated hyperbranched polymer.

[0051] Preparation Example 1

[0052] Sodium alginate was modified with L-cysteine and an amino-terminated hyperbranched polymer as described in Preparation Example 1 by the following steps: S1. 10 kg of L-cysteine was added to 6 kg of water and stirred for 30 minutes to obtain a uniform mixture. 15 kg of sodium alginate was then added and stirred to obtain an L-cysteine-modified hydrosol.

[0053] S2. Add 7 kg of hyperbranched polymer to the sodium alginate hydrosol obtained in step S1, stir for 1-5 h, add 8 kg of gluconolactone and 19 kg of calcium carbonate, and stir at 25 ° C for 8 h to obtain L-cysteine-modified sodium alginate and hyperbranched polymer gel.

[0054] Preparation Example 2-5

[0055] The preparation methods of L-cysteine-modified sodium alginate and hyperbranched polymer in Preparation Examples 2-5 are the same as those in Preparation Example 1, except that the amounts of sodium alginate and hyperbranched polymer in the raw materials are different, as shown in Table 1.

[0056] Table 1. Dosage of L-cysteine-modified sodium alginate and hyperbranched polymer in Preparation Examples 2-5 (kg)

[0057]

[0058] Preparation Examples 6-9

[0059] The preparation methods of L-cysteine-modified sodium alginate and hyperbranched polymers in Preparation Examples 6-9 are the same as those in Preparation Example 3, except that the amount of calcium carbonate added in the raw materials is different, as shown in Table 2 for details.

[0060] Table 2: Dosage of L-cysteine-modified sodium alginate and hyperbranched polymer in Preparation Examples 6-9 (kg)

[0061]

[0062] Example 1

[0063] A method for treating landfill leachate in Example 1 comprises the following steps:

[0064] S1 Primary Settling: The landfill leachate is subjected to primary settling for 7 days and the filter residue is removed to obtain primary settling landfill leachate;

[0065] S2: Adjusting the primary landfill leachate obtained in S1 to adjust the water volume to 0.5 wt % of the primary landfill leachate, while removing the generated odor to obtain adjusted landfill leachate;

[0066] S3 anaerobic treatment: the regulated landfill leachate obtained in S2 is subjected to anaerobically mixed with the exclusion of air to form suspended sludge to obtain anaerobic landfill leachate;

[0067] S4 water quality equalization: the anaerobic landfill leachate obtained in S3 is subjected to water quality equalization to a pH of 6.5-7.5, and stirred to obtain homogeneous landfill leachate;

[0068] S5 adsorption treatment: the homogenized landfill leachate obtained in S4 is treated with 0.9 kg / L landfill leachate treatment agent for a residence time of 8 days to obtain adsorbed landfill leachate;

[0069] S6 membrane treatment: The adsorbed landfill leachate obtained in S5 was concentrated and then treated with NF membrane, with a membrane filtration flux of 15.4 L / (h·m 2 ), total water production 13.6m 3 / h, the NF membrane water production rate is controlled at 85% to obtain membrane-treated landfill leachate;

[0070] S7 deep oxidation: The membrane-treated landfill leachate obtained in S6 is subjected to ozone oxidation at a temperature of 150°C and a pressure of 10 MPa for 3 days to obtain discharge water that meets water quality standards.

[0071] The landfill leachate treating agent is prepared by the following preparation method:

[0072] According to the dosage in Table 3, water and polysilicate titanium iron salt were mixed and dissolved; then biochar, sodium alginate modified with L-cysteine and terminal amino hyperbranched polymer, and defoamer were added and mixed and stirred evenly to obtain a landfill leachate treatment agent, wherein the sodium alginate modified with L-cysteine and terminal amino hyperbranched polymer was prepared in Preparation Example 1, and the biochar was sludge-based biochar.

[0073] Example 2-3

[0074] The difference between the landfill leachate treatment method of Example 2-3 and Example 1 is that the dosage of L-cysteine and amino-terminated hyperbranched polymer co-modified sodium alginate in the landfill leachate treatment agent raw materials in the biochemical pool is different, as shown in Table 3 for details.

[0075] Table 3 Dosage of the leachate treatment agent of Examples 1-3 (kg)

[0076]

[0077] Examples 4-5

[0078] The difference between the landfill leachate treatment method of Example 4-5 and Example 2 lies in the different types and dosages of biochar in the raw materials of the landfill leachate treatment agent in the biochemical pool, as shown in Table 4 for details.

[0079] Table 4 Dosage of the leachate treatment agent of Example 4-5 (kg)

[0080]

[0081] Example 6

[0082] The difference between the landfill leachate treatment method of Example 6 and Example 5 is that the raw materials of the landfill leachate treatment agent in the biochemical pool also include polyacrylamide and carboxymethyl starch. The specific dosages are shown in Table 5.

[0083] Examples 7-10

[0084] The difference between the landfill leachate treatment methods of Examples 7-10 and Example 6 is that the dosage of polyacrylamide in the raw material of the landfill leachate treatment agent in the biochemical pool is different, as shown in Table 5 for details.

[0085] Table 5 Dosage of the leachate treatment agent of Examples 6-10 (kg)

[0086]

[0087] Examples 11-18

[0088] The difference between the landfill leachate treatment method of Examples 11-18 and Example 8 is that the sodium alginate modified with L-cysteine and the terminal amino hyperbranched polymer in the raw materials of the landfill leachate treatment agent in the biochemical pool is prepared in Preparation Examples 2-9, and the sodium alginate is modified with L-cysteine and the terminal amino hyperbranched polymer. The types and dosages of other raw materials are the same as those in Example 8.

[0089] Comparative Example 1

[0090] The landfill leachate treatment method of Comparative Example 1 differs from that of Example 1 in that the sodium alginate modified with L-cysteine and amino-terminated hyperbranched polymer in the raw materials of the landfill leachate treatment agent in the biochemical pool is replaced with an equal amount of unmodified sodium alginate, and the types and dosages of the other raw materials are the same as those in Example 1.

[0091] Comparative Example 2

[0092] The landfill leachate treatment method of Comparative Example 2 differs from that of Example 1 in that the sodium alginate modified with L-cysteine and the amino-terminated hyperbranched polymer in the raw materials of the landfill leachate treatment agent in the biochemical pool is replaced with an equal amount of L-cysteine, and the types and dosages of the other raw materials are the same as those in Example 1.

[0093] Comparative Example 3

[0094] The landfill leachate treatment method of Comparative Example 3 is the same as that of Example 1, except that the sodium alginate modified with L-cysteine and amino-terminated hyperbranched polymer in the raw materials of the landfill leachate treatment agent in the biochemical pool is replaced with an equal amount of hyperbranched polymer, and the types and dosages of the other raw materials are the same as those in Example 1.

[0095] Performance testing

[0096] The landfill leachate treated by the landfill leachate treatment methods of Examples 1-18 and Comparative Examples 1-3 was tested, and the water quality test results are shown in Table 6:

[0097] Before treatment, the COD of the leachate was 953.5 mg / L, the mercury ion concentration was 24 mg / L, the cadmium ion concentration was 14 mg / L, the ammonia nitrogen concentration was 650 mg / L, and the suspended matter content was 2559 mg / L.

[0098] The detection method is: Chemical oxygen demand (COD) is determined in accordance with the national environmental protection standard HJ8282017 "Determination of Chemical Oxygen Demand of Water Quality - Dichromate Method".

[0099] Heavy metal ions were determined in accordance with the national environmental protection standard HJ 7762015 “Determination of 32 elements in water quality by inductively coupled plasma optical emission spectrometry”.

[0100] Ammonia nitrogen concentration was determined in accordance with the national environmental protection standard HJ 5362009 “Water quality - Determination of ammonia nitrogen - Salicylic acid spectrophotometry”.

[0101] The suspended matter content is determined in accordance with the national standard GB 1190189 “Water quality - Determination of suspended matter by gravimetric method”.

[0102] Table 6 Landfill leachate water quality test results

[0103]

[0104]

[0105] The test results in Table 6 show that the COD removal rate, mercury ion removal rate, cadmium ion removal rate, ammonia nitrogen removal rate and suspended solids removal rate of the landfill leachate after adopting the landfill leachate treatment method of the present application are as high as 96.83%, 99.11%, 99.20%, 99.05% and 95.65%, respectively, which has a high treatment effect.

[0106] Combined with the water quality test results after the landfill leachate treatment methods of Examples 1-3 and Comparative Examples 1-3, the COD removal rate, mercury ion removal rate, cadmium ion removal rate, ammonia nitrogen removal rate and suspended solids removal rate of the landfill leachate after being treated by the landfill leachate treatment method of Examples 1-3 were 81.33-83.15%, 89.98-91.05%, 91.06-92.02%, 89.32-90.46% and 82.85-84.69%, respectively, which were significantly higher than those of Comparative Examples 1-3. This indicates that the addition of L-cysteine and amino-terminated hyperbranched polymer to the raw materials of the landfill leachate treatment agent to jointly modify sodium alginate can significantly improve the treatment effect of the landfill leachate.

[0107] In Examples 2 and 4-5, the COD removal rate, mercury ion removal rate, cadmium ion removal rate, ammonia nitrogen removal rate and suspended solids removal rate of the landfill leachate after the landfill leachate treatment method of Example 5 was adopted were 86.19%, 92.84%, 93.61%, 92.37% and 87.75%, respectively, which were higher than those of Examples 2 and 4, indicating that when the biochar in the raw material includes 20-40wt% of sludge-based biochar and 50-80wt% of plant-based biochar, it is more appropriate to improve the treatment effect of landfill leachate. It may be that the biochar in the raw material includes 50-60wt% of sludge-based biochar and 20-40wt% of plant-based biochar, which can improve the removal of heavy metal ions and COD, NH4+ The removal rate of -N, NO2-N, TN, aromatic and difficult-to-degrade organic matter with double bonds is related to the removal rate of -N, NO2-N, TN, aromatic and difficult-to-degrade organic matter with double bonds.

[0108] In Examples 5 and 6, the COD removal rate, mercury ion removal rate, cadmium ion removal rate, ammonia nitrogen removal rate, and suspended solids removal rate of the landfill leachate after the landfill leachate treatment method of Example 6 were 87.41%, 93.56%, 94.25%, 93.13%, and 91.98%, respectively, which were higher than those of Example 5. This indicates that the addition of polyacrylamide and carboxymethyl starch to the raw materials is more suitable and improves the landfill leachate treatment efficiency. This may be related to the fact that the addition of polyacrylamide and carboxymethyl starch to the raw materials can enhance the flocculation effect of the polysilicate titanium iron salt.

[0109] In Examples 6-10, the COD removal rate, mercury ion removal rate, cadmium ion removal rate, ammonia nitrogen removal rate, and suspended solids removal rate of the landfill leachate after the landfill leachate treatment methods of Examples 7-9 were 88.93-90.45%, 94.45-95.35%, 95.05-95.85%, 94.09-95.04%, and 93.68-95.04%, respectively, all higher than those of Examples 6 and 10. This indicates that a weight ratio of polyacrylamide to carboxymethyl starch of (3-4):1 is more suitable and improves the landfill leachate treatment effect. This may be related to the fact that controlling the weight ratio of polyacrylamide to carboxymethyl starch can further enhance the flocculation effect of the polysilicate titanium iron salt.

[0110] In Examples 8 and 11-14, the COD removal rate, mercury ion removal rate, cadmium ion removal rate, and ammonia nitrogen removal rate of the landfill leachate after the landfill leachate treatment method of Examples 11-13 were 91.51-93.79%, 95.97-97.32%, 96.41-97.60%, and 95.71-97.41%, respectively, all higher than those of Examples 8 and 14. The suspended matter removal rate remained essentially unchanged, indicating that a weight ratio of L-cysteine-modified sodium alginate to L-cysteine, sodium alginate, and amino-terminated hyperbranched polymer in the hyperbranched polymer raw material of 1:(2-2.5):(0.8-1) is more suitable and improves the landfill leachate treatment effect. This may be related to the fact that the weight ratio of L-cysteine, sodium alginate, and amino-terminated hyperbranched polymer can improve the removal rate of heavy metal ions.

[0111] In Examples 3 and 15-18, the COD removal rate, mercury ion removal rate, cadmium ion removal rate, and ammonia nitrogen removal rate of the landfill leachate treated by the landfill leachate treatment method of Examples 15-17 were 95.01-96.83%, 98.03-99.11%, 98.24-99.20%, and 97.90-99.05%, respectively, all higher than those of Examples 3 and 18. The suspended matter removal rate remained essentially unchanged, indicating that a weight ratio of L-cysteine-modified sodium alginate to gluconolactone and calcium carbonate in the hyperbranched polymer raw material of 1:(2.25-2.5) is more suitable and improves the landfill leachate treatment effect. This may be related to the fact that the weight ratio of gluconolactone and calcium carbonate can improve the removal rate of heavy metal ions.

[0112] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for treating landfill leachate, characterized in that: The steps include: S1: Primary sedimentation: The landfill leachate is subjected to primary sedimentation, mixing and removal of filter residue to obtain primary sedimentation landfill leachate; S2 regulation: adjusting the water volume of the primary landfill leachate obtained in S1 and removing the generated odor to obtain regulated landfill leachate; S3 anaerobic treatment: the regulated landfill leachate obtained in S2 is anaerobically mixed to form suspended sludge to obtain anaerobic landfill leachate; S4 water quality equalization: the anaerobic landfill leachate obtained in S3 is subjected to water quality equalization and stirring to obtain homogeneous landfill leachate; S5 adsorption treatment: adding 0.3-1.5 kg / L of landfill leachate treatment agent to the homogenized landfill leachate obtained in S4 to obtain adsorbed landfill leachate; S6 membrane treatment: the adsorbed landfill leachate obtained in S5 is concentrated and membrane treated to obtain membrane treated landfill leachate; S7 deep oxidation: the membrane-treated landfill leachate obtained in S6 is subjected to ozone oxidation treatment to obtain discharge water that meets water quality standards; The S5 adsorption treatment agent for landfill leachate comprises the following raw materials in parts by weight: 150-300 parts of biochar, 50-100 parts of defoaming agent, 100-300 parts of sodium alginate modified with L-cysteine and amino-terminated hyperbranched polymer, 50-150 parts of polysilicate titanium iron salt, and 2-10 parts of water.

2. The method for treating landfill leachate according to claim 1, wherein: The sodium alginate modified by L-cysteine and amino-terminated hyperbranched polymer comprises the following raw materials in parts by weight: 5-15 parts of L-cysteine, 10-40 parts of sodium alginate, 3-15 parts of amino-terminated hyperbranched polymer, 16-25 parts of calcium carbonate, 5-10 parts of water, and 6-10 parts of gluconolactone.

3. The method for treating landfill leachate according to claim 2, wherein: The sodium alginate modified by L-cysteine and the amino-terminated hyperbranched polymer is obtained by the following steps: S1. Add L-cysteine to water and stir evenly, then add sodium alginate and stir evenly to obtain L-cysteine-modified sodium alginate hydrosol; S2. Add amino-terminated hyperbranched polymer to the L-cysteine-modified sodium alginate hydrosol obtained in step S1, stir for 1-5 hours, add gluconolactone and calcium carbonate, and stir at 20-30° C. for 5-10 hours to obtain sodium alginate modified with L-cysteine and amino-terminated hyperbranched polymer.

4. The method for treating landfill leachate according to claim 2, wherein: The weight ratio of the L-cysteine, sodium alginate and amino-terminated hyperbranched polymer is 1:(2-2.5):(0.8-1).

5. The method for treating landfill leachate according to claim 2, wherein: The weight ratio of the gluconolactone and calcium carbonate is 1:(2.25-2.5).

6. The method for treating landfill leachate according to claim 1, wherein: The biochar comprises 20-40 wt% of sludge-based biochar and 50-80 wt% of plant-based biochar.

7. The method for treating landfill leachate according to claim 1, wherein: The raw materials of the landfill leachate treating agent further include 50-100 parts by weight of polyacrylamide and 10-30 parts by weight of carboxymethyl starch.

8. The method for treating landfill leachate according to claim 7, wherein: The weight ratio of the polyacrylamide and carboxymethyl starch is (3-4):

1.

9. The method for treating landfill leachate according to claim 2, wherein: The landfill leachate treating agent is prepared by the following steps: mixing and dissolving water and polysilicate titanium iron salt; then adding biochar, L-cysteine and amino-terminated hyperbranched polymer to modify sodium alginate and defoaming agent and other admixtures, and mixing and stirring evenly to obtain the landfill leachate treating agent.

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