Manganese removal device and in-situ electrochemical preparation and cleaning method of manganese removal functional layer

Abstract

The invention belongs to the technical field of water treatment, particularly relates to purification of manganese-containing sewage, and discloses a manganese removal device and an in-situ electrochemical preparation and cleaning method of a manganese removal functional layer. By arranging the water purification functional layer and combining with the ceramic membrane to treat the manganese-containing underground water, the underground water can be efficiently treated, and the ruthenium-iridium-titanium anode and the cathode are used for preventing the pollution of the water purification functional layer, prolonging the service life of the device and increasing the flux of the ceramic membrane; the functional layer can intercept most pollutants and prevent the pollutants from polluting the membrane material.

Description

Technical Field

[0001] The invention relates to a water treatment device, a water treatment method and a cleaning method, and in particular to a manganese removal device and an in-situ electrochemical preparation and cleaning method of a manganese removal functional layer. Background Art

[0002] Manganese is one of the most abundant elements in the earth's crust. It dissolves in surface water and groundwater through contact with water bodies, generally in the form of Mn 2+ Although trace manganese plays an important role in the growth of plants and animals, if Mn 2+ Exceeding the standard concentration may cause discomfort in appearance and taste, and may have adverse effects on human health, so Mn 2+ The birnessite type manganese oxide can adsorb dissolved Mn(II) in water and catalytically oxidize it into insoluble Mn(IV) for retention. Therefore, the birnessite type manganese oxide has a good treatment effect on water bodies with excessive manganese content.

[0003] At the same time, membrane separation technology has been widely used in the field of water treatment, but membrane pollution is still the most difficult factor in membrane water treatment process. How to solve the problem of membrane pollution is still an urgent problem to be solved.

[0004] In the prior art, "Pre-depositing PAC-birnessite cake layer on gravity drivennceramic membrane (GDCM) reactor for manganese removal: The signiffcance of stable ffux and biofflm, Xing Du etc Separation and Purification Technology, 367 (2021) 118623" discloses a method for removing Mn through a functional layer. Although its treatment efficiency is high, this method faces the problem of easy clogging.

[0005] And “Enhancing manganese removal through pre-deposition of powdered activated carbon-manganese oxide (PAC-MnOx) fflm on gravity-driven ceramic membrane: The impact of biofilm integrity and ffuid dynamics, Qiao Wang etc, Separation and Purification Technology, 342 (2024) 127051” also discloses a method for treating manganese-containing water based on the synergistic effect between a gravity-based Mn removal functional layer and a ceramic membrane. However, this technology also faces the problem of easy clogging.

[0006] Based on the above problems, the inventors have developed a manganese removal device and an in-situ electrochemical preparation and cleaning method for a manganese removal functional layer. The present invention can purify manganese-containing water while increasing the filtration flux of the device through electrochemical cleaning, extending the use time of the device and reducing the number of cleaning times of the device. Summary of the invention

[0007] In order to solve the problems existing in the above-mentioned prior art, the main purpose of the present application is to provide a manganese removal device and an in-situ electrochemical preparation and cleaning method of a manganese removal functional layer.

[0008] In the first aspect of the present invention, the present invention discloses the following technical scheme: a manganese removal device, comprising a raw water tank, a raw water inlet pipe, a raw water inlet valve, a membrane bioreactor, a water purification functional layer, a ceramic membrane, a water outlet pipe, a water outlet valve, and a purified water collecting tank.

[0009] Furthermore, the membrane bioreactor is an electrochemical membrane bioreactor, and the electrochemical membrane bioreactor includes a raw water inlet, a ceramic membrane, a titanium wire, a ruthenium-iridium-titanium anode, a cathode, a water outlet, and an exhaust port; Furthermore, the ruthenium-iridium-titanium anode and the cathode are used to prevent contamination of the water purification functional layer.

[0010] Furthermore, the water purification functional layer is prepared by the following method: S1: Disconnect the raw water inlet pipe from the water inlet and close the water outlet valve; S2: Connect the titanium wire to the controllable DC regulated power supply through the wire and open the exhaust port; S3: adding a mixed suspension of manganese sulfate solution, sodium chloride solution and activated carbon powder into the electrochemical membrane bioreactor; S4: adjusting the power supply voltage, electrolyzing the sodium chloride solution, oxidizing Mn(II) to insoluble manganese oxides, attaching them to the surface of the suspended activated carbon powder particles, and reacting for 1-4 hours; preferably, the reaction time is 2 hours; S5: Connect the raw water inlet pipe and the water inlet, open the outlet valve, and under the action of gravity, an in-situ electrochemically coupled ceramic membrane surface manganese oxide water purification functional layer is formed on the ceramic membrane and the cathode.

[0011] Furthermore, the ruthenium iridium titanium electrode sheet is matched with the electrochemical membrane bioreactor, the edge of the ruthenium iridium titanium electrode sheet is 1-3 mm smaller than the reactor, and the ruthenium iridium titanium electrode sheet is welded with titanium wire with a diameter of 1-2 mm, and the titanium wire passes through the small hole on the top of the reactor and is fixed.

[0012] Furthermore, the ruthenium-iridium-titanium electrode sheet is matched to the circle of a circular electrochemical membrane bioreactor, and the diameter of the circle is 1-3 mm smaller than that of the reactor, preferably 1-2 mm.

[0013] Furthermore, a ceramic membrane is placed parallel to the bottom of the membrane bioreactor, the upper part of the ceramic membrane is the water inlet area of ​​the membrane pool, and the part below the ceramic membrane is the water outlet area. Ruthenium, iridium and titanium anodes are fixed on the surface of the ceramic membrane, and the spacing between the ruthenium, iridium and titanium anodes is 1-4 cm, preferably 2 cm.

[0014] Furthermore, one end of the titanium wire is welded to the electrode sheet, and the other end passes through the top of the electrochemical membrane bioreactor and is connected to the electric wire.

[0015] Furthermore, the diameter of the titanium wire is 1-1.5 mm.

[0016] A second aspect of the present invention is a water purification method using the manganese removal device as described in the first aspect; Manganese-containing groundwater is placed in a raw water tank. Under the action of gravity, the manganese-containing water enters the electrochemical membrane bioreactor. In the reactor, the manganese-containing water comes into contact with the water purification functional layer and is purified by the ceramic membrane before entering the clean water collection tank.

[0017] Furthermore, the Mn in the manganese-containing groundwater is 2+ The concentration is 0.49-0.52 mg / L. After treatment, the manganese ion concentration of the water entering the clean water collection tank is less than 0.1 mg / L.

[0018] In a third aspect, the present invention provides a method for cleaning the manganese removal device as described in the first aspect, comprising the following steps: S1: Close the raw water inlet, separate the raw water inlet pipe from the reactor inlet, close the outlet valve, open the exhaust port, pump out the water in the water inlet area to a suitable height, and then connect the positive and negative electrodes of the constant current power supply to the titanium wire of the corresponding electrode sheet; S2: Turn on the steady-current power switch, adjust the voltage knob, maintain a certain current density, and control the reaction time; use the bubbles precipitated on the surface of the cathode electrode to disturb the water purification functional layer, and the free chlorine produced by the anode is dispersed in the water inlet area. After the reaction is completed, the cleaned suspension in the water inlet area is extracted.

[0019] Furthermore, the cleaning cycle is 1-2 months, the voltage of the current-stabilizing power supply is 5V, and the current density is 2.9-3.1 mA / cm 2 The electrochemical cleaning time is 2-4h. After cleaning, the flux of the in-situ electrochemically coupled ceramic membrane surface manganese oxide reactor increases by an average of 30-90%.

[0020] Furthermore, the reactor throughput increased by an average of 50-90% after cleaning.

[0021] In certain embodiments, the manganese removal device includes a raw water tank, a raw water inlet pipe, a raw water inlet valve, an electrochemical membrane bioreactor, a water purification functional layer, a ceramic membrane, an outlet pipe, an outlet valve, a purified water collecting tank, a controllable DC regulated power supply, and electric wires.

[0022] In certain embodiments, the collected manganese-containing groundwater is placed in a raw water tank. Under the action of gravity, the manganese-containing water enters the electrochemical membrane bioreactor. In the membrane bioreactor, the manganese-containing water contacts the water purification functional layer, and the manganese ions are self-catalytically oxidized by manganese oxides in the functional layer and biologically oxidized by manganese oxidizing bacteria to form new manganese oxides, participating in the removal of manganese ions.

[0023] In some embodiments, the in-situ electrochemically coupled ceramic membrane surface manganese oxide reactor structure and functional layer preparation process is: A ceramic membrane is placed in parallel at the bottom of the membrane bioreactor, the upper part of the ceramic membrane is the membrane pool water inlet area, and the lower part of the ceramic membrane is the water outlet area. Ruthenium, iridium and titanium cathodes are fixed on the ceramic membrane, and the electrode spacing is 1-4cm, preferably 2-3cm; sodium chloride solution, manganese sulfate solution and activated carbon powder are added to the membrane pool water inlet area, and under certain voltage conditions, the Cl of the sodium chloride solution is electrolyzed. - to free chlorine; and the suspended activated carbon powder particle environment can promote the free chlorine to oxidize dissolved Mn(II) into insoluble manganese oxide, and at the same time provide a carrier for the attachment of manganese oxide; under gravity pressure, manganese oxide-activated carbon is deposited on the ceramic membrane to form a water purification functional layer.

[0024] In some embodiments, the process of electrochemically cleaning the functional layer by the manganese removal device of the in-situ electrochemically coupled ceramic membrane surface manganese oxide reactor is as follows: When performing electrochemical cleaning, turn off the water inlet pump and water inlet valve, separate the water inlet pipe from the reactor water inlet, open the exhaust port, pump out the water in the water inlet area to a suitable height, close the water outlet valve, and then connect the positive and negative electrodes of the constant current power supply to the titanium wire of the corresponding electrode sheet.

[0025] Turn on the steady-current power switch, adjust the voltage knob to increase the voltage reading to an appropriate value, and then control the reaction time to 2-4 hours. The voltage can be selected to be no less than 5V.

[0026] Since the applied voltage exceeds the oxygen evolution potential and chlorine evolution potential of the electrode sheet, the bubbles precipitated on the surface of the cathode electrode are used to disturb the functional layer, promoting the dispersion of the functional layer, and the free chlorine generated by the anode is dispersed in the membrane pool and fully contacts the functional layer. The present invention utilizes the free chlorine to fall off and attach to the EPS on the particle surface and oxidize it into smaller molecules. The suspension after cleaning in the membrane pool is extracted and normal operation is resumed. The present invention can increase the water production flux, and the pores of the functional layer are enlarged and restored after electrochemical cleaning, thereby improving the permeability of the functional layer, extending the life of the ceramic membrane, and increasing the total water filtration volume.

[0027] Compared with the prior art, the beneficial effects of the present invention are: The present invention utilizes an in-situ electrochemically coupled ceramic membrane surface manganese oxide reactor to treat manganese-containing groundwater, Mn 2+ It is oxidized and removed by manganese oxides in the water purification functional layer with good removal effect.

[0028] The device and method of the present invention electrolyzes sodium chloride solution to obtain free chlorine, which can convert Mn 2+ It is oxidized to manganese oxides, and the abundant active sites on the surface of activated carbon promote the oxidation of manganese ions by adsorbed free chlorine and the attachment of newly generated manganese oxides in situ, thereby dispersing the distribution of manganese oxides, increasing the contact area with manganese-containing water, and expanding the porosity of the water purification functional layer.

[0029] The device and method of the present invention utilize bubbles generated at the cathode to disturb the functional layer, and the electrical properties of activated carbon can promote interspecies electron transfer, accelerate the oxidation of extracellular polymers EPS between pores by free chlorine and free radicals generated at the anode, significantly alleviate the pollution of the functional layer, and increase the water production efficiency of the system.

[0030] The device and method of the present invention can improve the water filtration flux of the device, prolong the life of the ceramic membrane, and increase the total amount of water filtered by the ceramic membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of a manganese removal device system of an in-situ electrochemically coupled ceramic membrane surface manganese oxide reactor of the present invention; Figure 2 It is a schematic diagram of the structure of an electrochemical membrane bioreactor; Figure 3 It is a schematic diagram of the in-situ electrochemical cleaning process.

[0032] In the figure: raw water tank 1, electrochemical membrane bioreactor 2, water purification functional layer 3, ceramic membrane 4, water purification collecting tank 5, raw water inlet valve 6, raw water inlet pipe 7, outlet pipe 8, outlet valve 9, electric wire 10, controllable DC regulated power supply 11, water inlet 201, titanium wire 202, ruthenium iridium titanium anode 203, cathode 204, water outlet 205, exhaust port 206. DETAILED DESCRIPTION

[0033] For a better understanding of the present invention, the following examples are provided to further illustrate the present invention, but the content of the present invention is not limited to the following examples. Example 1

[0034] Combination Figure 1 The present embodiment is described as a manganese removal device for an in-situ electrochemically coupled ceramic membrane surface manganese oxide reactor, comprising a raw water tank (1), a raw water inlet pipe (7), an electrochemical membrane bioreactor (2), a water purification functional layer (3), a ceramic membrane (4), a water outlet pipe (8), a purified water collection tank (5), a controllable DC regulated power supply (11), and an electric wire (10).

[0035] The water outlet of the raw water tank (1) is provided with a raw water inlet valve (6) for controlling the opening and closing of raw water entering the electrochemical membrane bioreactor (2); and the inlet of the clean water collecting tank (5) is provided with a water outlet valve (9) for controlling the opening and closing of filtered water entering.

[0036] The collected manganese-containing groundwater is placed in a raw water tank (1), and under the action of gravity, the manganese-containing water enters the electrochemical membrane bioreactor (2).

[0037] In the reactor (2), the manganese-containing water contacts the functional layer (3), Mn 2+ The manganese oxides in the functional layer (3) are self-catalytically oxidized and bio-oxidized by manganese oxidizing bacteria to form new manganese oxides, which participate in the removal of manganese ions.

[0038] The electrochemical membrane bioreactor (2) comprises a water inlet (201), a titanium wire (202), a ruthenium-iridium-titanium anode (203), a cathode (204), a water outlet (205), and an exhaust port (206).

[0039] A ceramic membrane (4) is placed parallel to the bottom of the electrochemical membrane bioreactor (2), the upper part of the ceramic membrane is the membrane pool water inlet area, and the lower part of the ceramic membrane is the water outlet area. Ruthenium, iridium and titanium cathodes (anode (203) and cathode (204) are fixed on the ceramic membrane, and the electrode spacing is 2 cm.

[0040] One end of the titanium wire (202) is welded to the electrode sheet, and the other end passes through the top of the electrochemical membrane bioreactor (3) and is connected to the wire (10). Disconnect the raw water inlet pipe (7) from the water inlet (201), close the outlet valve (9), connect the titanium wire (202) to the controllable DC voltage-stabilized power supply (11) through the wire (10), open the exhaust port (206), add manganese sulfate solution, sodium chloride solution and activated carbon powder. Turn on the power supply, adjust the voltage of the power supply (11) to 5V, and electrolyze the Cl of the sodium chloride solution. - It is a free chlorine active substance, oxidizing Mn(II) to insoluble manganese oxide, which adheres to the surface of suspended activated carbon powder particles. The reaction time is 2h.

[0041] After the reaction is completed, the raw water inlet pipe (7) is connected to the water inlet (201), and the water outlet valve (9) is opened. Under the action of gravity, the collected groundwater enters the electrochemical membrane bioreactor (2), and the pressure causes the activated carbon-manganese oxide to be deposited on the ceramic membrane (4) and the cathode (204) to form a water purification functional layer (3). Example 2

[0042] Using the water purification method of the device in Example 1, the prepared Mn 2+ =0.5 mg / L of groundwater is placed in a raw water tank (1), and under the action of gravity, the manganese-containing groundwater enters the electrochemical membrane bioreactor (2).

[0043] In the reactor (2), the manganese-containing water contacts the functional layer (3), Mn 2+ The manganese oxides in the functional layer (3) are self-catalytically oxidized and bio-oxidized by manganese oxidizing bacteria to form new manganese oxides, which participate in the removal of manganese ions.

[0044] After one week of operation, the manganese ion in the effluent was still below 0.1 mg / L after treatment by in-situ electrochemical coupling ceramic membrane surface manganese oxide reactor, and the effluent Mn 2+ The concentration meets the water quality standards of the "Hygiene Standard for Tap Drinking Water" (GB / T 5750-2006), and the treated water can be used in decentralized drinking water facilities. Example 3

[0045] According to the water purification method of Example 2, the water is continuously purified, and the ceramic membrane flux is about 60L / (m 2 ·h) dropped to about 15 L / (m 2 h), the following parameters are used for electrochemical cleaning: The voltage value of the controllable DC regulated power supply is 5V, and the current density is 2.9~3.1 mA / cm 2 The electrochemical cleaning time was 4 h. After cleaning, the flux of the device increased by 66.7% to 25 L / (m 2 h).

[0046] When the cleaned device is used to purify the same sewage again and operated under the same conditions, it will take one month for the ceramic membrane flux to drop to the level before cleaning, about 15 L / (m 2 h), repeat the first cleaning operation. Example 4

[0047] According to the water purification method of Example 2, the water is continuously purified, and the ceramic membrane flux is about 60L / (m 2 ·h) dropped to about 14 L / (m 2 h) Electrochemical cleaning was performed using the following parameters: The voltage value of the controllable DC regulated power supply is 5V, and the current density is 2.9~3.1 mA / cm 2 The electrochemical cleaning time was 4 h, and the device flux increased to 28 L / (m 2 h).

[0048] When the cleaned device is used again to purify the same sewage and operated again under the same working conditions, it will take one month for the ceramic membrane flux to drop to the level before cleaning, at which time the first cleaning operation is repeated. Example 5

[0049] Comparing the flux of the reactor with and without electrochemical cleaning of the functional layer, the flux of the reactor without any operation increased from 60L / (m 2 h) down to 15 L / (m 2 ·h) and showed a stable trend, but the overall trend continued to decline. After three months, the flux decreased to 12L / (m 2 ·h). For the reactor that has undergone periodic electrochemical cleaning (cleaning every three months and once a month), the average flux can be stabilized at 25 L / (m 2 ·h), which is almost twice as much as the flux without any operation. This shows that electrochemical cleaning can significantly improve the flux of the device and maintain the flux at a high level. Comparative Example 1

[0050] In order to compare the effects of the present invention, the inventors used conventional cleaning methods to clean the functional layer, including forward aeration and backwashing, while electrochemical backwashing showed better cleaning effects.

[0051] The device adopts the same operating conditions, flow rate and water quality as Example 3-5. After 3 months of long-term operation, the system flux is reduced to 15 L / (m 2 h) or so.

[0052] Positive aeration: Use an air pump with an air volume of 20L / min to evenly disperse the functional layer and reconstruct the functional layer. The flux temporarily increases from 15 L / (m 2 h) rebound to 20L / (m 2 ·h), but after one day of normal operation, the flux returned to the level of 15 L / (m 2 h) Flux: forward aeration cannot reconstruct the functional layer well.

[0053] Electrochemical cleaning can restore the flux to 28 L / (m 2 ·h), and it can maintain a stable downward trend. After 25 days of continuous filtration after electrochemical cleaning, the flux returned to the level before cleaning, 15L / (m 2 h), and the manganese ion in the effluent can still be kept below 0.1 mg / L. Although positive aeration can redistribute the functional layer evenly and disperse the connection between particles and particles and between particles and EPS, a large amount of EPS accumulated in the functional layer cannot be removed after long-term operation. After restarting, a new round of accumulation will occur. Therefore, the water flux will drop rapidly after a short recovery. Electrochemical cleaning can directly remove EPS by separating the adhesion between particles and EPS through electrochemical chlorine production.

[0054] The backwashing method for cleaning and regeneration has a weaker effect on the recovery of flux, and the flux is almost not improved. The backwashing method for cleaning and regeneration cannot increase the membrane flux. After cleaning, the membrane flux is still 15L / (m 2 ·h), this is because the system of the present invention is different from the traditional sand filtration. The water penetration during the backwashing process is greatly affected by the pressure resistance of the ceramic membrane. In addition, water has no effect on removing EPS, so the effect of increasing the flux by backwashing cannot be achieved.

[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is limited by the appended claims and their equivalents.

Claims

1. A manganese removal device, comprising a raw water tank, a raw water inlet pipe, a raw water inlet valve, a membrane bioreactor, a water purification functional layer, a ceramic membrane, a water outlet pipe, a water outlet valve, and a purified water collection tank, characterized in that: The membrane bioreactor is an electrochemical membrane bioreactor, which includes a raw water inlet, a ceramic membrane, a titanium wire, a ruthenium-iridium-titanium anode, a cathode, a water outlet, and an exhaust port; The ruthenium-iridium-titanium anode and the cathode are used to prevent contamination of the water purification functional layer.

2. A manganese removal device according to claim 1, characterized in that: The water purification functional layer is prepared by the following method: S1: Disconnect the raw water inlet pipe from the water inlet and close the water outlet valve; S2: Connect the titanium wire to the controllable DC regulated power supply through the wire and open the exhaust port; S3: adding a mixed suspension of manganese sulfate solution, sodium chloride solution and activated carbon powder into the electrochemical membrane bioreactor; S4: adjusting the power supply voltage, electrolyzing the sodium chloride solution, oxidizing Mn(II) to insoluble manganese oxide, attaching it to the surface of the suspended activated carbon powder particles, and reacting for 1-4 hours; S5: Connect the raw water inlet pipe and the water inlet, open the outlet valve, and under the action of gravity, the water purification functional layer is formed on the ceramic membrane and the cathode.

3. A manganese removal device according to claim 1, characterized in that: The ruthenium-iridium-titanium electrode sheet is matched with the electrochemical membrane bioreactor, and the edge of the ruthenium-iridium-titanium electrode sheet is 1-3 mm smaller than the reactor. The ruthenium-iridium-titanium electrode sheet is respectively welded with titanium wires with a diameter of 1-2 mm, and the titanium wires pass through the small holes on the top of the reactor and are fixed.

4. A manganese removal device according to claim 3, characterized in that: The ruthenium-iridium-titanium electrode sheet is matched to the circle of a circular electrochemical membrane bioreactor, and the diameter of the circle is 1-3 mm smaller than that of the reactor.

5. A manganese removal device according to claim 1, characterized in that: A ceramic membrane is placed parallel to the bottom of the membrane bioreactor, the upper part of the ceramic membrane is the membrane pool water inlet area, and the lower part of the ceramic membrane is the water outlet area. Ruthenium, iridium and titanium cathodes are fixed on the surface of the ceramic membrane, and the distance between the ruthenium, iridium and titanium cathodes is 1-4 cm.

6. A manganese removal device according to claim 1, characterized in that: One end of the titanium wire is welded to the electrode sheet, and the other end passes through the top of the electrochemical membrane bioreactor and is connected to the electric wire.

7. A water purification method using the manganese removal device according to any one of claims 1 to 6, characterized in that: Manganese-containing groundwater is placed in a raw water tank. Under the action of gravity, the manganese-containing water enters the electrochemical membrane bioreactor. In the reactor, the manganese-containing water comes into contact with the water purification functional layer and is purified by the ceramic membrane before entering the clean water collection tank.

8. A water purification method according to claim 7, characterized in that: The Mn content of the manganese-containing groundwater 2+ The concentration is 0.49-0.52 mg / L. After treatment, the manganese ion concentration of the water entering the clean water collection tank is less than 0.1 mg / L.

9. A method for cleaning a manganese removal device according to any one of claims 1 to 6, characterized in that: S1: Close the raw water inlet, separate the raw water inlet pipe from the reactor inlet, close the outlet valve, open the exhaust port, pump out the water in the water inlet area to a suitable height, and then connect the positive and negative electrodes of the constant current power supply to the titanium wire of the corresponding electrode sheet; S2: Turn on the steady-current power switch, adjust the voltage knob, maintain a certain current density, and control the reaction time; use the bubbles precipitated on the surface of the cathode electrode to disturb the water purification functional layer, and the free chlorine produced by the anode is dispersed in the water inlet area. After the reaction is completed, the cleaned suspension in the water inlet area is extracted.

10. A cleaning method according to claim 9, characterized in that: The cleaning cycle is 1-2 months, the voltage of the current-stabilizing power supply is 5V, and the current density is 2.9-3.1 mA / cm 2 The electrochemical cleaning time is 2-4h. After cleaning, the flux of the in-situ electrochemically coupled ceramic membrane surface manganese oxide reactor increases by an average of 30-40%.

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