A method and device for treating concentrated liquid of reverse osmosis of domestic waste leachate

Abstract

The application discloses a kind of domestic waste leachate reverse osmosis concentrated liquid processing method and processing device, the domestic waste leachate reverse osmosis concentrated liquid processing method includes the following steps: step 1: remove or reduce the heavy metal ion content in domestic waste leachate reverse osmosis concentrated liquid;Step 2: the domestic waste leachate reverse osmosis concentrated liquid after step 1 processing is desalted to reduce its salt concentration;Step 3: the domestic waste leachate reverse osmosis concentrated liquid after step 2 processing is decomposed COD by the action of electricity production microorganism and reduces ammonia nitrogen, the application can effectively remove the refractory organic matter in reverse osmosis concentrated liquid, high salt content and high ammonia nitrogen and heavy metal and other harmful substances, in addition, the main energy of the processing system of the application can be provided by the electricity generated by microbial metabolism, with the advantages of energy saving and carbon reduction, simple operation, stable operation and low cost, in addition, by reducing the salt concentration in wastewater, so that microorganism is more active in wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and in particular relates to a method and device for treating reverse osmosis concentrate from municipal solid waste leachate. Background Technology

[0002] Before treatment, municipal solid waste leachates with complex components, which poses a potential threat to the environment. Membrane treatment processes, with reverse osmosis as the main representative, are one of the common methods for the deep treatment of municipal solid waste leachate. However, after reverse osmosis treatment, pollutants are concentrated to form leachate concentrate from the membrane treatment process. This concentrate contains a large amount of recalcitrant organic matter, high salt content, high ammonia nitrogen, as well as harmful substances such as heavy metals, making it a difficult wastewater to treat.

[0003] Currently, the main treatment processes for municipal solid waste leachate reverse osmosis concentrate include atomized spray incineration, evaporation, reinjection, and advanced oxidation technologies. Among these, atomized spray incineration involves atomizing the membrane concentrate under high temperature and pressure and then spraying it into the incinerator. In the furnace, the concentrate evaporates water to reduce its volume and burns away organic pollutants. However, this process can easily generate dioxins, causing secondary pollution, and corresponding measures are still needed. Evaporation technology involves heating the reverse osmosis concentrate to evaporate the water in the wastewater, forming condensate. Simultaneously, it removes volatile and recalcitrant organic compounds and ammonia nitrogen from the concentrate. Studies have shown that evaporation is effective in treating concentrates. However, the volatile organic gases produced during evaporation, such as alkanes, benzene compounds, and alcohols, require further treatment, increasing operating costs. Furthermore, the harmless disposal of the concentrated solids containing high levels of heavy metals and salinity left after evaporation is a significant challenge. Reinjection technology involves reinjecting wastewater into a landfill for natural infiltration. Within the landfill, some water evaporates, reducing the water volume. Oxidation-reduction reactions and the biodegradation capabilities of microorganisms remove recalcitrant organic compounds from the wastewater. This technology is simple to operate and has low operating costs, leading to its adoption by numerous landfills. However, the removed ions are merely adsorbed within the landfill and cannot be completely removed. With the operation of the reinjection process, conventional ions and heavy metals continue to accumulate internally, affecting not only the microorganisms responsible for degradation but also resulting in higher salt content in the subsequent leachate and higher heavy metal content in the sludge produced by microorganisms in the landfill. This is not a long-term solution. In recent years, advanced oxidation technologies, including Fenton oxidation and ozone oxidation, have been researched and applied to landfill leachate treatment. These technologies primarily generate hydroxyl radicals with strong oxidizing capabilities to oxidize organic pollutants in wastewater into CO2 or easily treatable organic matter. They are characterized by rapid effectiveness, minimal secondary pollution, and effective reduction of water toxicity. However, advanced oxidation technologies cannot completely remove heavy metals. Summary of the Invention

[0004] In order to solve the above-mentioned technical problems, one of the objectives of the present invention is to provide a method for purifying reverse osmosis concentrate of municipal solid waste leachate.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A method for treating reverse osmosis concentrate from municipal solid waste leachate, comprising the following steps:

[0006] Step 1: Remove or reduce the content of heavy metal ions in the reverse osmosis concentrate of municipal solid waste leachate;

[0007] Step 2: Desalinate the reverse osmosis concentrate of the leachate from municipal solid waste treated in Step 1 to reduce its salt concentration;

[0008] Step 3: The reverse osmosis concentrate of the leachate from municipal solid waste treated in Step 2 is decomposed by electrogenic microorganisms and ammonia nitrogen is reduced.

[0009] In step 1 of the above technical solution, an alkaline solution is added to the reverse osmosis concentrate of municipal solid waste leachate to form hydroxide precipitates of heavy metal ions.

[0010] In step 2 of the above technical solution, electrodialysis is used to reduce the salt concentration in the reverse osmosis concentrate of the municipal solid waste leachate.

[0011] The alkaline solution mentioned in the above technical solution is a sodium hydroxide solution and / or a potassium hydroxide solution.

[0012] The second objective of this invention is to provide a simple treatment device that can purify the reverse osmosis concentrate of municipal solid waste leachate according to the above-described treatment method.

[0013] To achieve the above objectives, another technical solution of the present invention is as follows: a municipal solid waste leachate reverse osmosis concentrate treatment device, which uses the municipal solid waste leachate reverse osmosis concentrate treatment method described above to purify wastewater, wherein the wastewater is municipal solid waste leachate reverse osmosis concentrate, and includes a sedimentation unit, a desalination unit and a microbial fuel cell unit. Alkali solution and wastewater are added to the sedimentation unit to form and remove heavy metal ions in the wastewater. The wastewater treated by the sedimentation unit is then discharged into the desalination unit to reduce the salt concentration in the wastewater. The wastewater treated by the desalination unit is then discharged into the microbial fuel cell unit to reduce the COD and ammonia nitrogen concentrations in the wastewater.

[0014] The sedimentation unit described in the above technical solution includes a sedimentation tank and a solid-liquid separation mechanism. The sedimentation tank has a discharge port at its lower end, and the solid-liquid separation mechanism has an inlet, an outlet, and a solid outlet. The outlet of the sedimentation tank is connected to the inlet of the solid-liquid separation mechanism, and the outlet of the solid-liquid separation mechanism is connected to the desalination unit. The wastewater is mixed with alkaline solution in the sedimentation tank, and heavy metals are precipitated in the sedimentation tank.

[0015] The desalination unit described in the above technical solution includes a first tank body, which is equipped with a cation exchange membrane, an anion exchange membrane, and a bipolar membrane. The cation exchange membrane, anion exchange membrane, and bipolar membrane together divide the first tank body into four sub-tanks. The four sub-tanks are, in order, an anode tank, an acid-producing tank, a desalination tank, and a cathode tank. A bipolar membrane connects the anode tank and the acid-producing tank, an anion exchange membrane connects the acid-producing tank and the desalination tank, and a cation exchange membrane connects the desalination tank and the cathode tank. Wastewater treated by the precipitation unit is discharged into the desalination tank. A first cathode electrode is provided in the cathode tank, and a first anode electrode is provided in the anode tank. The first anode electrode and the first cathode electrode are electrically connected to the positive and negative terminals of a power source, respectively. The anode tank contains a conductive liquid, and the wastewater in the acid-producing tank is discharged into the microbial fuel cell unit.

[0016] The microbial fuel cell unit described in the above technical solution includes a second pool body, which has a second anode and a second cathode electrode. The second anode and the second cathode electrode are electrically connected, and the wastewater treated by the desalination unit is discharged into the second pool body.

[0017] In the above technical solution, the first anode and the second anode are made of carbon fiber brushes, and the first cathode and the second cathode are made of activated carbon air cathodes.

[0018] In the above technical solution, both the first anode and the second anode are enriched with electrogenic microorganisms.

[0019] The beneficial effects of this invention are as follows: through the combined action of alkali precipitation, bio-electrodialysis, and microbial fuel cell, this invention can effectively remove recalcitrant organic matter, high salt content, high ammonia nitrogen, and heavy metals from reverse osmosis concentrate. In addition, the main energy source of the treatment system of this invention can be provided by the electricity generated by microbial metabolism, which has the advantages of energy saving and carbon reduction, simple operation, stable operation, and low cost. Furthermore, by reducing the salt concentration in the wastewater, the activity of microorganisms in the wastewater is improved. Attached Figure Description

[0020] Figure 1 This is a simplified structural diagram of the municipal solid waste leachate reverse osmosis concentrate treatment device according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the specific structure of the municipal solid waste leachate reverse osmosis concentrate treatment device according to an embodiment of the present invention.

[0022] In the diagram: 1. Sedimentation unit; 11. Sedimentation tank; 12. Solid-liquid separation mechanism; 2. Desalination unit; 21. First tank; 21a. Anode tank; 21b. Acid production tank; 21c. Desalination tank; 21d. Cathode tank; 22. Cation exchange membrane; 23. Anion exchange membrane; 24. Bipolar membrane; 25. First cathode electrode; 26. First anode electrode; 3. Microbial fuel cell unit; 31. Second tank; 32. Second anode electrode; 33. Second cathode electrode. Detailed Implementation

[0023] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description and claims. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0024] This embodiment provides a method for treating reverse osmosis concentrate from municipal solid waste leachate, including the following steps:

[0025] Step 1: Remove or reduce the content of heavy metal ions in the reverse osmosis concentrate of municipal solid waste leachate;

[0026] Step 2: Desalinate the reverse osmosis concentrate of the leachate from municipal solid waste treated in Step 1 to reduce its salt concentration;

[0027] Step 3: The COD of the municipal solid waste leachate reverse osmosis concentrate treated in Step 2 is decomposed and the ammonia nitrogen is reduced by electrogenic microorganisms. In Step 1, an alkaline solution is added to the municipal solid waste leachate reverse osmosis concentrate to form hydroxide precipitates of heavy metal ions (heavy metal ions can be heavy metal ions that can precipitate with hydroxide ions, such as copper ions, zinc ions, and cadmium ions). In Step 2, an electrodialysis method is used to reduce the salt concentration in the municipal solid waste leachate reverse osmosis concentrate. The alkaline solution is sodium hydroxide solution and / or potassium hydroxide solution.

[0028] In addition, such as Figure 1 and Figure 2As shown, this embodiment also provides a municipal solid waste leachate reverse osmosis concentrate treatment device, which uses the municipal solid waste leachate reverse osmosis concentrate treatment method described above to purify wastewater. The wastewater is municipal solid waste leachate reverse osmosis concentrate, including a sedimentation unit 1, a desalination unit 2, and a microbial fuel cell unit 3. Alkali solution and wastewater are added to the sedimentation unit 1 to form and remove heavy metal ions in the wastewater. The wastewater treated by the sedimentation unit 1 is then discharged into the desalination unit 2 to reduce the salt concentration in the wastewater. The wastewater treated by the desalination unit 2 is then discharged into the microbial fuel cell unit 3 to reduce the COD and ammonia nitrogen concentrations in the wastewater.

[0029] The sedimentation unit 1 described in the above technical solution includes a sedimentation tank 11 and a solid-liquid separation mechanism 12. The lower end of the sedimentation tank 11 has a drain outlet, and the solid-liquid separation mechanism 12 has an inlet, an outlet, and a solid outlet. The outlet of the sedimentation tank 11 is connected to the inlet of the solid-liquid separation mechanism 12, and the outlet of the solid-liquid separation mechanism 12 is connected to the desalination unit 2. The wastewater is mixed with alkaline solution in the sedimentation tank 11, and heavy metals are precipitated in the sedimentation tank 11.

[0030] The desalination unit 2 described in the above technical solution includes a first tank 21. The first tank 21 is equipped with a cation exchange membrane 22, an anion exchange membrane 23, and a bipolar membrane 24. These membranes divide the first tank 21 into four sub-tanks. The four sub-tanks are, in order, an anode tank 21a, an acid-producing tank 21b, a desalination tank 21c, and a cathode tank 21d. A bipolar membrane 24 connects the anode tank 21a and the acid-producing tank 21b; an anion exchange membrane 23 connects the acid-producing tank 21b and the desalination tank 21c; and a cation exchange membrane connects the desalination tank 21c and the cathode tank 21d. Membrane replacement 22: Wastewater treated by the sedimentation unit 1 is discharged into the desalination tank 21c. A first cathode electrode 25 is installed in the cathode tank 21d, and a first anode electrode 26 is installed in the anode tank 21a. The first anode electrode 26 and the first cathode electrode 25 are electrically connected to the positive and negative terminals of the power supply, respectively (through the action of the electric field, cations in the wastewater migrate to the cathode tank, and anions migrate to the acid-producing tank. By controlling the potential and current density of the electrodes, ions in the wastewater can be effectively removed, thereby reducing the salt content). The anode tank 21a contains a conductive liquid, and the wastewater in the acid-producing tank 21b is discharged into the microbial fuel cell unit 3.

[0031] The microbial fuel cell unit 3 described in the above technical solution includes a second pool body 31, which contains a second anode 32 and a second cathode 33. The second anode 32 and the second cathode 33 are electrically connected. The wastewater treated by the desalination unit 2 is discharged into the second pool body 31 (the organic matter is converted into electrical energy by the metabolic action of microorganisms. The desalinated wastewater is used as the influent, and the organic pollutants in it are oxidized and decomposed into electron donors by microorganisms. The electron donors are transferred to the electrodes through the microbial membrane and combine with the electron acceptors on the electrodes to generate electrical energy, while simultaneously further denitrifying).

[0032] In the above technical solution, the first anode 26 and the second anode 32 are made of carbon fiber brushes, the first cathode 25 and the second cathode 33 are made of activated carbon air cathodes, and the first anode 26 and the second anode 32 are enriched with electrogenic microorganisms.

[0033] In this embodiment, a 10 mol / L sodium hydroxide solution is added to the sedimentation tank to finely adjust the pH of the nanofiltration concentrate (wastewater) to ensure it remains stable within the range of 12.0 ± 0.1. After a 2-hour reaction (stirring can be performed during the reaction, and the mixture should be allowed to stand afterward to ensure the precipitate settles completely), the heavy metal ions and OH groups are ensured to react completely. - The reaction produces a hydroxide precipitate. In this embodiment, the solid-liquid separation mechanism 12 can be separated by a centrifuge (of course, it is not limited to this, and can be a commonly used solid-liquid separation device on the market).

[0034] The reverse osmosis concentrate of the leachate from domestic waste was treated using the above-mentioned treatment device, and the parameters of the wastewater after treatment were monitored. As shown in Table 1, the wastewater was rendered harmless after treatment.

[0035] Table 1. Removal effect of the present invention on major pollutants in municipal solid waste leachate

[0036]

[0037] Note: Raw water refers to the reverse osmosis concentrate of leachate from domestic waste; COD, TN, NH3-N, and TP are all routine indicators in wastewater testing.

[0038] 5. The processing method and processing apparatus provided in this embodiment have the following advantages:

[0039] Wastewater resource utilization and energy conversion: Both the bio-electrodialysis (desalination unit) and the microbial fuel cell unit can convert organic pollutants in wastewater into electrical energy through the action of electrogenic microorganisms, with some of the energy used in situ for system treatment. The bio-electrodialysis unit can convert salts in wastewater into recyclable acid and alkali resources through bipolar membrane dissociation of water molecules and membrane migration. The acid can be reused for membrane cleaning in the bio-electrodialysis unit to reduce membrane fouling, and the alkali can be reused for the alkali addition reaction in the precipitation unit. Therefore, this embodiment achieves efficient resource utilization and also provides some of the energy required for system operation.

[0040] Environmentally friendly: The entire treatment process does not produce secondary pollution, and all generated materials are effectively treated or reused, which is in line with the concept of green environmental protection.

[0041] 5. The processing flow of the processing device provided in this embodiment is as follows:

[0042] 1. Precipitation Unit:

[0043] (1) Add the wastewater to the sedimentation tank;

[0044] (2) The pH of the wastewater was adjusted to 12.0±0.1 by precisely adding a sodium hydroxide solution with a concentration of 10 mol / L;

[0045] (3) Allow the reaction to proceed for 2 hours to ensure that the heavy metal ions and OH groups react completely. - The reaction produces a hydroxide precipitate;

[0046] (4) To enable the suspended matter to settle effectively and complete the solid-liquid separation.

[0047] 2. Desalination unit:

[0048] (1) Add the wastewater treated by the sedimentation unit to the desalination tank, add the culture medium (which can be wastewater containing nutrients and suitable for the growth of electrogenic microorganisms, and the wastewater must also be conductive) to the anode tank, and pre-fill the acid production tank and the cathode tank with a sodium chloride solution of 1g / L (so that it is conductive).

[0049] (2) The power supply used in the desalination unit is a DC power supply. The external voltage of the power supply is adjusted to 1.0V (the electrogenic microorganisms in the desalination unit will also generate electrical energy, which is equivalent to an external power supply connected in series). It runs under constant voltage for 12 hours. Through the action of electric field, the cations in the wastewater migrate to the cathode pool and the anions migrate to the acid production pool, thereby achieving effective removal of ions in the concentrate and reducing the salt content.

[0050] 3. Microbial fuel cell unit:

[0051] (1) The concentrated liquid after desalination is introduced into the microbial fuel cell unit;

[0052] (2) Connect the second anode and the second cathode electrically with a wire and connect them in series with a 1000Ω external resistor (the second anode and the second cathode form a power source by themselves);

[0053] (3) Run for 24 hours to further remove organic pollutants and ammonia nitrogen.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A reverse osmosis concentrate treatment device for municipal solid waste leachate, characterized in that, The system includes a precipitation unit (1), a desalination unit (2), and a microbial fuel cell unit (3). Alkali solution and wastewater are added to the precipitation unit (1) to form a precipitate of heavy metal ions in the wastewater and remove the precipitate. The wastewater treated by the precipitation unit (1) is then discharged into the desalination unit (2) to reduce the salt concentration in the wastewater. The wastewater treated by the desalination unit (2) is then discharged into the microbial fuel cell unit (3) to reduce the COD and ammonia nitrogen concentrations in the wastewater. The desalination unit (2) includes a first tank (21), in which a cation exchange membrane (22), an anion exchange membrane (23), and a bipolar membrane (24) are disposed. The first tank (21) is divided into four sub-tanks by the cation exchange membrane (22), anion exchange membrane (23), and bipolar membrane (24). The four sub-tanks are, in order, an anode tank (21a), an acid-producing tank (21b), a desalination tank (21c), and a cathode tank (21d). The bipolar membrane (24) is located between the anode tank (21a) and the acid-producing tank (21b). The acid-producing tank (21b) and the desalination tank (21c) are connected by a bipolar membrane (24). c) is an anion exchange membrane (23), and the desalination tank (21c) and the cathode tank (21d) are connected by a cation exchange membrane (22). The wastewater treated by the precipitation unit (1) is discharged into the desalination tank (21c). The cathode tank (21d) is equipped with a first cathode electrode (25), and the anode tank (21a) is equipped with a first anode electrode (26). The first anode electrode (26) and the first cathode electrode (25) are electrically connected to the positive and negative poles of the power supply, respectively. The anode tank (21a) is filled with conductive liquid. The wastewater in the acid production tank (21b) is discharged into the microbial fuel cell unit (3).

2. The municipal solid waste leachate reverse osmosis concentrate treatment device according to claim 1, characterized in that, The sedimentation unit (1) includes a sedimentation tank (11) and a solid-liquid separation mechanism (12). The sedimentation tank (11) has a drain outlet at its lower end. The solid-liquid separation mechanism (12) has an inlet, an outlet and a solid outlet. The outlet of the sedimentation tank (11) is connected to the inlet of the solid-liquid separation mechanism (12). The outlet of the solid-liquid separation mechanism (12) is connected to the desalination unit (2). The wastewater is mixed with alkaline solution in the sedimentation tank (11) and heavy metals are precipitated in the sedimentation tank (11).

3. The municipal solid waste leachate reverse osmosis concentrate treatment device according to claim 1, characterized in that, The microbial fuel cell unit (3) includes a second pool body (31), which has a second anode (32) and a second cathode (33) connected to each other. Wastewater treated by the desalination unit (2) is discharged into the second pool body (31).

4. The municipal solid waste leachate reverse osmosis concentrate treatment device according to claim 3, characterized in that, The first anode (26) and the second anode (32) are made of carbon fiber brushes, and the first cathode (25) and the second cathode (33) are made of activated carbon air cathodes.

5. The municipal solid waste leachate reverse osmosis concentrate treatment device according to claim 4, characterized in that, Electrogenic microorganisms are enriched on both the first anode (26) and the second anode (32).

6. A method for treating municipal solid waste leachate concentrate using the reverse osmosis concentrate treatment device according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Remove or reduce the content of heavy metal ions in the reverse osmosis concentrate of municipal solid waste leachate; Step 2: Desalinate the reverse osmosis concentrate of the leachate from municipal solid waste treated in Step 1 to reduce its salt concentration; Step 3: The reverse osmosis concentrate of the leachate from municipal solid waste treated in Step 2 is decomposed by electrogenic microorganisms and ammonia nitrogen is reduced.

7. The method for treating municipal solid waste leachate reverse osmosis concentrate according to claim 6, characterized in that, In step 1, an alkaline solution is added to the reverse osmosis concentrate of municipal solid waste leachate to form hydroxide precipitates of heavy metal ions.

8. The method for treating municipal solid waste leachate reverse osmosis concentrate according to claim 6, characterized in that, In step 2, electrodialysis is used to reduce the salt concentration in the reverse osmosis concentrate of the municipal solid waste leachate.

9. The method for treating municipal solid waste leachate reverse osmosis concentrate according to claim 7, characterized in that, The alkaline solution is a sodium hydroxide solution and / or a potassium hydroxide solution.

Images