Method for treating membrane concentrated solution by using two-stage hydrothermal reaction

Abstract

The invention discloses a method for treating a membrane concentrated solution by using a two-stage hydrothermal reaction, which comprises the following steps: providing the membrane concentrated solution, and adjusting the pH value of the membrane concentrated solution to be acidic to obtain an initial reaction solution; performing a first hydrothermal reaction on the initial reaction solution, separating after the first hydrothermal reaction is finished to obtain a first liquid phase solution and a solid phase material, and drying the solid phase material to obtain artificial humus; adjusting the pH value of the first liquid phase solution to be acidic to obtain an acidizing treatment solution, adding hydrogen peroxide based on the volume of an acidizing reaction solution and the concentration of organic matters, and carrying out a second hydrothermal reaction to obtain a second liquid phase solution after the reaction is finished; carrying out microbial biochemical treatment on the second liquid-phase solution to remove residual organic matters in the hydrothermal solution so as to obtain a third liquid-phase solution; and carrying out evaporation and concentration treatment on the third liquid phase solution to recover the inorganic salt. According to the method, a membrane concentrated solution is treated by using a two-stage hydrothermal process, and resource recovery is realized while the sewage is treated to reach the standard.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane concentrate, and particularly to a method for treating membrane concentrate by using a two-stage hydrothermal reaction. Background Art

[0002] In all aspects of the harmless and resourceful treatment of municipal solid waste, a large amount of landfill leachate is continuously generated. Generally, biochemical treatment units (such as anaerobic fermentation and membrane bioreactor) are used for the preliminary treatment of leachate containing high-concentration organic matter. In order to meet the discharge requirements of GB16889-2024, nanofiltration membranes, reverse osmosis membranes or even multi-stage membrane systems (CJJ / T150-2023) are usually used to further treat the biochemical effluent to ensure that the effluent quality meets the standards. However, the use of membrane processes will produce landfill leachate membrane concentrate with a volume ratio of 13%-30%, which is characterized by extremely high organic matter content, high aromaticity and extremely low biodegradability, and it is difficult to be effectively treated by conventional physical and chemical or biochemical processes.

[0003] Currently, the conventional treatment methods for membrane concentrate in China include returning to the landfill and advanced oxidation processes (AOPs), etc. However, these methods have inevitable limitations in terms of resource recovery, carbon emission reduction, sustainable development, etc. Returning to the landfill can treat a large amount of membrane concentrate in the short term, but the non-biodegradable organic matter and high-concentration inorganic salts (NH 4+ , Cl - ) will continuously accumulate in the landfill, increasing the treatment pressure of the landfill while reducing the treatment effect, posing challenges to the effective operation of the landfill and possibly affecting environmental safety. Although AOPs can effectively degrade organic matter, it is extremely dependent on the addition of extra reagents (such as Fe 2+ , H + and H2O2), and has a high operating cost. At the same time, the extra reagents added will introduce extra ions and organic intermediates into the system, which may further pollute the treated water body. In addition, most of the organic matter is finally degraded into CO2, which runs counter to the current background of "dual carbon".

[0004] Based on the above problems, there is an urgent need for a green and environmental protection technology that can not only effectively treat membrane concentrate but also realize the reuse of organic matter, which not only meets the low operating cost but also promotes resource recovery and promotes the development of leachate treatment towards resource utilization. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for treating membrane concentrate by using a two-stage hydrothermal reaction in view of the technical defects existing in the prior art. This method treats membrane concentrate by using a two-stage hydrothermal process, achieving resource recovery while treating the sewage up to the standard.

[0006] The technical solution adopted to achieve the purpose of the present invention is as follows:

[0007] In a first aspect, a method for treating membrane concentrate by a two-stage hydrothermal reaction includes the following steps: providing a membrane concentrate, adjusting the pH of the membrane concentrate to acidic to obtain an initial reaction solution; performing a first hydrothermal reaction on the initial reaction solution, separating after the first hydrothermal reaction to obtain a first liquid-phase solution and a solid-phase material, and obtaining artificial humus after drying the solid-phase material; adjusting the pH of the first liquid-phase solution to acidic to obtain an acidified treatment solution, adding hydrogen peroxide based on the volume and organic matter concentration of the acidified reaction solution and then performing a second hydrothermal reaction, and obtaining a second liquid-phase solution after the reaction; performing microbial biochemical treatment on the second liquid-phase solution to remove the residual organic matter in the hydrothermal solution to obtain a third liquid-phase solution; and performing evaporation concentration treatment on the third liquid-phase solution to recover inorganic salts.

[0008] The method of the present application first converts the organic matter with difficult biodegradability and complex structure in the membrane concentrate into artificial humus through the first hydrothermal reaction, effectively improving the solidification of organic carbon and thus reducing carbon emissions. At the same time, the artificial humus can be used for environmental remediation and soil improvement, further improving the carbon utilization rate. Secondly, through the second hydrothermal reaction, under the action of hydrogen peroxide, the macromolecular organic matter remaining in the first liquid-phase solution is converted into low-molecular-weight and easily biodegradable organic matter and used for subsequent biochemical treatment. Compared with advanced oxidation, the combination of hydrothermal and hydrogen peroxide can effectively avoid the residual or dissolution of catalysts in the advanced oxidation process, and at the same time can also avoid converting all organic matter into CO2, effectively reducing carbon emissions. For the inorganic salts (KCl, NaCl) in the second liquid-phase solution, resource recovery is finally achieved through the biochemical treatment of salt-tolerant strains combined with evaporation concentration.

[0009] In some specific embodiments, the pH of the initial reaction solution is 3.7 to 4.3, and the pH of the acidified treatment solution is 3.7 to 4.3.

[0010] In some specific embodiments, the steps of performing a first hydrothermal reaction on the initial reaction solution, separating after the first hydrothermal reaction to obtain a first liquid-phase solution and a solid-phase material, and obtaining artificial humus after drying the solid-phase material include: loading the initial reaction solution into a reaction vessel, sealing and heating it to 180°C to 220°C at a rate of 3°C / min to 5°C / min and then reacting for 3 h to 6 h, and the volume of the initial reaction solution is not greater than 50% of the volume of the reaction vessel.

[0011] In some specific embodiments, for the first hydrothermal reaction of the initial reaction solution, after the first hydrothermal reaction is completed and separation is carried out, to obtain the first liquid-phase solution and the solid-phase material, and the step of obtaining artificial humus after drying the solid-phase material further includes: after the first hydrothermal reaction is completed, the reaction vessel is cooled and the solid-liquid mixture is taken out, and after standing for 12 h to 24 h, solid-liquid separation is carried out to obtain the first liquid-phase solution and the solid-phase material.

[0012] In some specific embodiments, for the first hydrothermal reaction of the initial reaction solution, after the first hydrothermal reaction is completed and separation is carried out, to obtain the first liquid-phase solution and the solid-phase material, and the step of obtaining artificial humus after drying the solid-phase material further includes: the solid-phase material is dried at 60 °C to 80 °C for 12 h to 24 h to remove the moisture in the solid-phase material to obtain solid hydrothermal carbon, and the solid hydrothermal carbon is artificial humus.

[0013] In some specific embodiments, hydrogen peroxide is an aqueous hydrogen peroxide solution with a mass content of 30%, and the addition amount of the aqueous hydrogen peroxide solution with a mass content of 30% satisfies formula (I):

[0014] V = 1.67×10 -5 ×DOC×V1 Formula (I)

[0015] In the formula, V is the added volume of the aqueous hydrogen peroxide solution with a mass content of 30%, and the unit is L; DOC is the concentration of organic matter in the acidified reaction solution, and the unit is mg / L; V1 is the volume of the acidified reaction solution. For example, when DOC = 1000 mg / L in the acidified reaction solution, the addition amount of the aqueous hydrogen peroxide solution with a mass content of 30% is 16.7 ml / L.

[0016] In some specific embodiments, after adjusting the pH of the first liquid-phase solution to acidic to obtain the acidified treatment solution, based on the volume and organic matter concentration of the acidified reaction solution, hydrogen peroxide is added and then the second hydrothermal reaction is carried out. The step of obtaining the second liquid-phase solution after the reaction is completed includes: loading the first reaction liquid-phase solution into a reaction vessel, sealing it, and heating it to 180 °C to 220 °C at a rate of 3 °C / min to 5 °C / min and then reacting for 1 h to 4 h.

[0017] In some specific embodiments, the membrane concentrate is a landfill leachate membrane concentrate.

[0018] Second, an artificial humus is prepared by the method of the first aspect.

[0019] In some specific embodiments, the artificial humus satisfies at least one of the following: (1) the mass ratio of oxygen element to carbon element in the artificial humus O / C < 0.6; (2) the mass ratio of the sum of oxygen element and nitrogen element to carbon element in the artificial humus (O + N) / C < 0.6; (3) the mass ratio of carbon element to N element in the artificial humus C / N > 22.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. In the method for treating membrane concentrate by two-stage hydrothermal reaction of the present application, through the first hydrothermal reaction, more than 40% of the organic carbon can be preferentially solidified, and high-quality artificial humus can be produced. The elemental composition of the artificial humus of the present application meets the local standard DB23 / T 3592-2023 and exceeds some other existing humus, and can be used for environmental remediation and soil improvement. On this basis, in the method of the present application, through the second hydrothermal reaction in the form of combining hydrothermal reaction with hydrogen peroxide, the complex organic matter remaining in the first hydrothermal solution can be effectively treated, so as to achieve a DOC removal rate of more than 50% and a UV 254 removal rate of more than 80%. At the same time, the second hydrothermal reaction can effectively promote the formation of small molecules, thereby improving the biodegradability of the liquid phase, and the luminescent bacteria inhibition rate is reduced by more than 30%.

[0022] 2. Compared with AOPs in the second hydrothermal reaction of the method for treating membrane concentrate by two-stage hydrothermal reaction of the present application, the only additional reagent is hydrogen peroxide, which can effectively solve the problems of catalyst dissolution or residue existing in the advanced oxidation process. And in the second hydrothermal reaction, high-concentration Cl - in the liquid will participate in the formation of reactive chlorine species to jointly promote the degradation of organic matter.

[0023] 3. In the method for treating membrane concentrate by two-stage hydrothermal reaction of the present application, salt-tolerant strains are used to further biochemically treat the effluent of the second hydrothermal reaction, and the removal of organic matter of 85%-95% is achieved again. Combining with the subsequent evaporation and concentration process, the inorganic salts in the biochemically treated effluent are recovered.

[0024] 4. In the method for treating membrane concentrate by two-stage hydrothermal reaction of the present application, the pH is adjusted to about 4.0. Compared with 3.0 selected by conventional AOPs, the consumption of acids and alkalis for pH adjustment is reduced. At the same time, the only additional reagent required is H2O2, and the dosage is relatively low, which can effectively reduce the reagent cost. The required hydrothermal environment for the reaction can be achieved by reasonably setting pipelines and recovering the waste heat of the incineration plant. At the same time, compared with advanced oxidation, it can effectively avoid the direct oxidation of organic matter to CO2, effectively achieving carbon emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The figure shows a process flow diagram of the method for treating membrane concentrate by two-stage hydrothermal reaction in Example 1.

[0026] Figure 2 The figure shows SEM images of different solid fertilizers, where Figure 2a1 and Figure 2 a2 are humic substances extracted from black soil, Figure 2 b1 and Figure 2 b2 are humic substances obtained from biomass reactions, Figure 2 c1 and Figure 2 c2 are artificial humic substances obtained in Example 1. Detailed implementation manners

[0027] The features and exemplary embodiments of various aspects of the present application will be described in detail below. To make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present application by showing examples of the present application.

[0028] For simplicity, the present application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, although not explicitly recited, each point or single value between the range endpoints is included in this range. Thus, each point or single value can be used as its own lower or upper limit and combined with any other point or single value or combined with other lower or upper limits to form a range not explicitly recited.

[0029] The above-mentioned inventive content of the present application does not intend to describe every disclosed embodiment or every implementation manner in the present application. The following description more specifically exemplifies exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments, which can be used in various combinations. In each instance, the enumeration is only a representative group and should not be construed as exhaustive. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0030] In view of the problems mentioned in the background art, the embodiments of the present application provide a method for treating membrane concentrate by a two-stage hydrothermal reaction, including the following steps: providing a membrane concentrate, adjusting the pH of the membrane concentrate to acidic to obtain an initial reaction solution; performing a first hydrothermal reaction on the initial reaction solution, separating after the first hydrothermal reaction to obtain a first liquid-phase solution and a solid-phase material, and obtaining artificial humus after drying the solid-phase material; adjusting the pH of the first liquid-phase solution to acidic to obtain an acidified treatment solution, adding hydrogen peroxide based on the volume and organic matter concentration of the acidified reaction solution, and then performing a second hydrothermal reaction, and obtaining a second liquid-phase solution after the reaction; performing microbial biochemical treatment on the second liquid-phase solution to remove the residual organic matter in the hydrothermal solution to obtain a third liquid-phase solution; performing evaporation concentration treatment on the third liquid-phase solution to recover inorganic salts.

[0031] The method of the present application first converts the organic matter with difficult biodegradability and complex structure in the membrane concentrate into artificial humus through the first hydrothermal reaction, effectively improving the solidification of organic carbon, thereby reducing carbon emissions. At the same time, the artificial humus can be used for environmental remediation and soil improvement, further improving the carbon utilization rate. Secondly, through the second hydrothermal reaction, under the action of hydrogen peroxide, the macromolecular organic matter remaining in the first liquid-phase solution is transformed into low-molecular-weight and easily biodegradable organic matter, which is used for subsequent biochemical treatment. Compared with advanced oxidation, the combination of hydrothermal and hydrogen peroxide can effectively avoid the residue or dissolution of the catalyst in the advanced oxidation process, and at the same time can also avoid converting all the organic matter into CO2, effectively reducing carbon emissions. For the inorganic salts (KCl, NaCl) in the second liquid-phase solution, resource recovery is finally achieved through the biochemical treatment of salt-tolerant strains combined with evaporation concentration.

[0032] In some embodiments, the pH of the initial reaction solution is 3.7 to 4.3. For example, the pH of the initial reaction solution can be 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, or any combination range of the above values; the pH of the acidified treatment solution is 3.7 to 4.3. For example, the pH of the acidified treatment solution can be 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, or any combination range of the above values.

[0033] In some embodiments, the steps for subjecting the initial reaction solution to a first hydrothermal reaction, separating after the first hydrothermal reaction to obtain a first liquid-phase solution and a solid-phase material, and drying the solid-phase material to obtain artificial humus include: loading the initial reaction solution into a reaction vessel, sealing it, heating it to 180°C to 220°C at a rate of 3°C / min to 5°C / min, and reacting for 3 h to 6 h. The volume of the initial reaction solution is not greater than 50% of the volume of the reaction vessel. For example, the volume of the initial reaction solution can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any combination range of the above values.

[0034] In some embodiments, the steps for subjecting the initial reaction solution to a first hydrothermal reaction, separating after the first hydrothermal reaction to obtain a first liquid-phase solution and a solid-phase material, and drying the solid-phase material to obtain artificial humus further include: after the first hydrothermal reaction ends, cooling the reaction vessel and taking out the solid-liquid mixture, standing for 12 h to 24 h, and then performing solid-liquid separation to obtain a first liquid-phase solution and a solid-phase material.

[0035] In some embodiments, the steps for subjecting the initial reaction solution to a first hydrothermal reaction, separating after the first hydrothermal reaction to obtain a first liquid-phase solution and a solid-phase material, and drying the solid-phase material to obtain artificial humus further include: drying the solid-phase material at 60°C to 80°C for 12 h to 24 h to remove the moisture in the solid-phase material to obtain solid hydrothermal carbon, and the solid hydrothermal carbon is artificial humus.

[0036] In some embodiments, hydrogen peroxide is an aqueous hydrogen peroxide solution with a mass content of 30%. The addition amount of the aqueous hydrogen peroxide solution with a mass content of 30% satisfies formula (I):

[0037] V = 1.67×10 -5 ×DOC×V1 Formula (I)

[0038] In the formula, V is the added volume of the aqueous hydrogen peroxide solution with a mass content of 30%, and the unit is L; DOC is the concentration of organic matter in the acidified reaction solution, and the unit is mg / L; V1 is the volume of the acidified reaction solution.

[0039] In some embodiments, the steps for adjusting the pH of the first liquid-phase solution to acidic to obtain an acidified treatment solution, adding hydrogen peroxide based on the volume and organic matter concentration of the acidified reaction solution, and then performing a second hydrothermal reaction to obtain a second liquid-phase solution after the reaction ends include: loading the first reaction liquid-phase solution into a reaction vessel, sealing it, heating it to 180°C to 220°C at a rate of 3°C / min to 5°C / min, and reacting for 1 h to 4 h.

[0040] In some embodiments, the membrane concentrate is a landfill leachate membrane concentrate.

[0041] Second aspect: An artificial humus is prepared by the method of the first aspect.

[0042] In some specific embodiments, the artificial humus satisfies at least one of the following: (1) the mass ratio of oxygen to carbon in the artificial humus, O / C < 0.6; (2) the mass ratio of the sum of oxygen and nitrogen to carbon in the artificial humus, (O + N) / C < 0.6; (3) the mass ratio of carbon to N in the artificial humus, C / N > 22.

[0043] In addition, the term "and / or" in this text is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this text generally represents an "or" relationship between the preceding and following associated objects.

[0044] The following examples more specifically describe the content disclosed in this application, and these examples are only for illustrative purposes.

[0045] In the examples of this application, the landfill leachate membrane concentrate sample is from a certain leachate treatment plant in Shenzhen, Guangdong Province, and it is a nanofiltration membrane concentrate.

[0046] Example 1

[0047] A method for treating membrane concentrate by two-stage hydrothermal reaction, as Figure 1 shown, includes the following steps:

[0048] Step 1: Provide the landfill leachate membrane concentrate, and use H2SO4 (1 mol / L) and NaOH (1 mol / L) to adjust the pH of the membrane concentrate to 4.0 to obtain the initial reaction solution.

[0049] Step 2: Transfer the above initial reaction solution to a stainless steel high-pressure reaction kettle with a maximum allowable load capacity of 50% of the reaction kettle volume, seal it and transfer it to an oven. Set the heating rate to 5 °C / min, and carry out the first hydrothermal reaction for 6 h under hydrothermal conditions at a temperature of 220 °C without additional pressurization or gas filling. After the first hydrothermal reaction ends, naturally cool it for 4 h to room temperature, open the kettle body, transfer the solid-liquid mixture to a separation container, and let it stand for 24 h. After solid-liquid separation, obtain the first liquid-phase solution and solid-phase material. The solid-phase material is dried at 60 °C for 24 h to remove the moisture in the solid-phase material. The dried solid material is artificial humus, which can be applied to environmental remediation and soil improvement.

[0050] Step 3: Use H2SO4 (1 mol / L) and NaOH (1 mol / L) to adjust the first liquid-phase solution to pH = 4 to obtain an acidified treatment solution. According to the organic matter concentration (DOC value) and treatment volume of the acidified treatment solution, calculate the required addition amount of hydrogen peroxide (mass concentration of 30%) according to formula (Ⅰ), and directly transfer it into the system. After mixing evenly, transfer it into a high-temperature reaction kettle for the second hydrothermal reaction. The hydrothermal time is 1 h, the heating rate is 5 °C / min, and the temperature is 220 °C. After the second hydrothermal reaction is completed, take out the reaction kettle and let it cool naturally to room temperature to obtain the second liquid-phase solution.

[0051] Step 4: Introduce the second liquid-phase solution into the biochemical treatment tank, and select salt-tolerant strains for biochemical treatment to remove the residual organic matter in the hydrothermal solution, which is beneficial to the subsequent recovery of inorganic salts, and obtain the third liquid-phase solution.

[0052] Step 5: Adopt the evaporation concentration method to recover NaCl and KCl in the third liquid-phase solution.

[0053] In this example, the parameters of the artificial humus are shown in Table 1.

[0054] Table 1 Comparison table of artificial humus and local standards (analyzed by an elemental analyzer)

[0055]

[0056] In Table 1: - indicates that the data cannot be obtained.

[0057] As can be seen from Table 1, the artificial humus prepared in this example meets the DB23 / T 3592-2023 standard and has practical value. The structure of the artificial humus is as Figure 2 shown.

[0058] The electron micrograph of the artificial humus synthesized in this example is as Figure 2 shown in c. It can be seen from the figure that it presents a humus skeleton structure similar to that of natural humus ( Figure 2 a) and the humus synthesized from fallen leaves ( Figure 2 b), and shows the aggregation phenomenon of carbon chains, and its elemental composition is mainly C and O. In addition, Figure 2 spheres composed of fragment structures also appear in c.

[0059] Table 2 Comparison of the average molecular weight and biological toxicity of the hydrothermal solution before and after the second hydrothermal reaction treatment

[0060] Average molecular weight (GPC) Average molecular weight (FT-ICR MS) Luminescent bacteria inhibition rate Membrane concentrate of landfill leachate 4210 Da 379.1 Da 90％ First liquid-phase solution 4109 Da 354.3 Da - Second liquid-phase solution 1281 Da 299.2 Da 54％

[0061] In Table 2: - indicates that the data cannot be obtained.

[0062] The organic matter in the membrane concentrate of landfill leachate, the first liquid-phase solution and the second liquid-phase solution of this example was detected, and the results are shown in Table 2. The method for treating the membrane concentrate by two-stage hydrothermal reaction of this application can effectively reduce the molecular weight of organic matter in the membrane concentrate of landfill leachate and the inhibition rate of luminescent bacteria.

[0063] Comparative Example 1-2

[0064] The difference between Comparative Example 1-2 and Example 1 is only the time of the first hydrothermal reaction. For details, see Tables 3 and 4.

[0065] Table 3 Parameter Results Table of Examples 1-3

[0066]

[0067]

[0068] Table 4 Comparison of the Distribution of Artificial Humic Substances / Humic Substance Elements in Example 1 and Comparative Example 1 (XPS Results)

[0069] C％ N％ O％ S％ O / C (O + N) / C C / N Natural humus 40.82 5.81 52.34 0.83 1.28 1.42 7.04 Artificial fulvic acid 55.05 - 43.61 - 0.79 - - Existing artificial humus 55.6 1.63 42.41 0.26 0.76 1.42 34.48 Artificial humus of Example 1 76.64 3.11 18.58 1.66 0.24 0.28 24.64 Artificial humus of Comparative Example 1 61.31 2.73 30.99 4.97 0.51 0.55 22.46

[0070] As can be seen from Tables 3 and 4, with the increase of the time of the first hydrothermal reaction, the yield of artificial humic substances prepared by the method of this application increases, and the DOC removal rate also further increases. At the same time, the artificial humic substances of this application have relatively low O / C, (O+N) / C and relatively high C / N, indicating that the artificial humic substances of this application have better carbon sequestration effect.

[0071] Comparative Example 3-8

[0072] The difference between Comparative Example 3-8 and Example 1 lies in the pH of the initial reaction solution and the time of the first hydrothermal reaction. For details, see Table 5.

[0073] Table 5 Comparative Table of Parameter Results of Example 1, Comparative Examples 1-6

[0074] Initial reaction solution pH First hydrothermal reaction time (h) DOC removal rate after the first hydrothermal reaction (%) Example 1 4 6 43 Comparative Example 3 8 1 6 Comparative Example 4 8 3 26 Comparative Example 5 8 6 28 Comparative Example 6 10 1 11 Comparative Example 7 10 3 26 Comparative Example 8 10 6 23

[0075] As can be seen from Table 5, with the acidification pH of this application, the first hydrothermal reaction has a higher DOC removal rate.

[0076] Example 2

[0077] The difference between Example 2 and Example 1 is the reaction time of the second hydrothermal reaction. For details, see Table 4.

[0078] Comparative Example 9-12

[0079] The difference between Comparative Example 9-12 and Example 1 lies in the time of the second hydrothermal reaction and the addition amount of hydrogen peroxide. For details, see Table 6.

[0080] Table 6 Results of organic matter removal in Example 1, Example 4 and Comparative Examples 7 - 10

[0081]

[0082]

[0083] In Table 6, a: is the dosage of hydrogen peroxide in Example 1, specifically calculated according to formula (Ⅰ).

[0084] As shown in Table 6, with the H2O2 addition amount of the present application, the second hydrothermal reaction has the optimal DOC removal rate, UV 254 removal rate and SUVA 254 removal rate.

[0085] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for treating membrane concentrate using a two-stage hydrothermal reaction, characterized in that: The following steps are involved: Providing a membrane concentrate, and adjusting the pH of the membrane concentrate to acidic to obtain an initial reaction solution; The initial reaction liquid is subjected to a first hydrothermal reaction, and after the first hydrothermal reaction is completed, a first liquid phase solution and a solid phase material are obtained by separation, and the solid phase material is dried to obtain artificial humus; The pH of the first liquid phase solution is adjusted to acidic to obtain an acidified treatment solution, hydrogen peroxide is added based on the volume and organic matter concentration of the acidified reaction solution, and a second hydrothermal reaction is performed to obtain a second liquid phase solution after the reaction is completed; The second liquid phase solution is subjected to microbial biochemical treatment to remove residual organic matter in the hydrothermal solution to obtain a third liquid phase solution; The third liquid phase solution is subjected to evaporation concentration treatment to recover the inorganic salt.

2. The method according to claim 1, characterized in that The pH of the initial reaction solution is 3.7-4.3, and the pH of the acidified treatment solution is 3.7-4.

3.

3. The method according to claim 1, characterized in that The step of performing a first hydrothermal reaction on the initial reaction solution, separating to obtain a first liquid phase solution and a solid phase material after the first hydrothermal reaction is completed, and drying the solid phase material to obtain artificial humus comprises: The initial reaction liquid is placed in a reaction container, which is sealed and heated to 180°C to 220°C at a rate of 3°C / min to 5°C / min, and then reacted for 3h to 6h. The volume of the initial reaction liquid is not greater than 50% of the volume of the reaction container.

4. The method according to claim 1, characterized in that The step of performing a first hydrothermal reaction on the initial reaction solution, separating to obtain a first liquid phase solution and a solid phase material after the first hydrothermal reaction is completed, and drying the solid phase material to obtain artificial humus also includes: After the first hydrothermal reaction is completed, the reaction container is cooled and the solid-liquid mixture is taken out. After standing for 12 to 24 hours, the solid-liquid is separated to obtain a first liquid phase solution and a solid phase material.

5. The method according to claim 1, characterized in that The step of performing a first hydrothermal reaction on the initial reaction solution, separating to obtain a first liquid phase solution and a solid phase material after the first hydrothermal reaction is completed, and drying the solid phase material to obtain artificial humus also includes: The solid phase material is dried at 60° C. to 80° C. for 12 h to 24 h to remove moisture in the solid phase material to obtain solid hydrothermal charcoal, which is artificial humus.

6. The method according to claim 1, characterized in that The hydrogen peroxide is a hydrogen peroxide aqueous solution with a mass content of 30%, and the addition amount of the hydrogen peroxide aqueous solution with a mass content of 30% satisfies formula (I): V=1.67×10 -5 ×DOC×V1 Formula (Ⅰ) Wherein, V is the added volume of the 30% by mass hydrogen peroxide aqueous solution, in L; DOC is the organic matter concentration in the acidified reaction solution, in mg / L; and V1 is the volume of the acidified reaction solution.

7. The method according to claim 1, characterized in that The step of adjusting the pH of the first liquid phase solution to acidity to obtain an acidified treatment solution, adding hydrogen peroxide based on the volume and organic matter concentration of the acidified reaction solution and performing a second hydrothermal reaction, and obtaining a second liquid phase solution after the reaction is completed comprises: The first reaction liquid phase solution is placed into a reaction container, which is sealed and heated to 180° C. to 220° C. at a rate of 3° C. / min to 5° C. / min, and then reacted for 1 h to 4 h.

8. The method according to claim 1, characterized in that The membrane concentrate is landfill leachate membrane concentrate.

9. An artificial humus, characterized in that: It is prepared by the method according to any one of claims 1 to 8.

10. The artificial humus according to claim 9, characterized in that: The artificial humus meets at least one of the following requirements: (1) The mass ratio of oxygen to carbon in the artificial humus is O / C < 0.6; (2) The mass ratio of the sum of the mass of oxygen and nitrogen elements to the mass of carbon element in the artificial humus (O+N) / C is less than 0.6; (3) The mass ratio of carbon element to nitrogen element in the artificial humus is C / N>22.

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