Manganese removal device for backflow water of drinking water purification plant

Abstract

The manganese removal device comprises a water outlet short pipe, a reaction tank, an iron electrode, a carbon electrode and a water inlet short pipe, the reaction tank is a turbulent flow reaction tank, the longitudinal section of the reaction tank is in a wave shape and has wave crests and wave troughs, and the two sides of the reaction tank are connected with the water inlet short pipe and the water outlet short pipe respectively. A carbon electrode and an iron electrode are mounted at the trough of the reaction tank, the carbon electrode is positioned in the upper direction, the iron electrode is positioned in the lower direction, and the iron electrode and the carbon electrode are mounted in a crossed manner at an angle of 30 degrees. When the device runs, the electrodes are connected to a power supply, a NaOH solution is added into the sodium hydroxide dosing pipe, iron loses electrons to generate ferrate ions, and soluble Mn < 2 + > in backflow water of a drinking water plant can be efficiently oxidized into insoluble Mn < 4 + >. The reaction tank can be used as a turbulent flow tank, and the section of the tank body is wave-shaped and has wave crests and wave troughs, so that the overflowing speed is changed to generate vortexes, the turbulent flow effect of water flow in the reaction tank is intensified, and the electrode reaction efficiency and the substrate mixing efficiency are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, and particularly relates to a manganese removal device for backflow water of a drinking water purification plant. BACKGROUND

[0002] Manganese causes multiple hazards to water treatment systems, the environment and the health of residents, and long-term drinking of water with excessive manganese may affect the health of the nervous system, especially having potential harm to the intelligence development of children. In recent years, relevant engineering research cases show that due to the metabolic action of algae and the high substrate concentration of raw water, the sludge water of the sedimentation tank of some drinking water treatment plants contains a large amount of manganese. The high-concentration manganese enriched in the sludge water is concentrated and dewatered and then backflows to the water treatment process, which greatly increases the treatment load of manganese and has a great impact on the original treatment process. In addition, the high-concentration manganese in the backflow water also causes changes in the odor and color of the effluent (such as black and red tap water). Therefore, the backflow water of the drinking water plant needs to be properly treated to prevent the manganese and other pollutants enriched therein from backflowing into the drinking water system.

[0003] At present, in China, divalent manganese (Mn 2+ ) is oxidized to insoluble MnO2 by an oxidizing agent (such as potassium permanganate and ozone) and removed by precipitation, or manganese sand, activated carbon or other adsorption materials are used to adsorb manganese in the sludge water. However, these methods have the problems of poor oxidation effect, complex equipment and facilities, and large investment. Especially for built water plants, they cannot be implemented due to the limitation of land space.

[0004] Based on the above needs, the present application designs an electrolytic manganese removal device with small occupation, excellent oxidation effect, green low toxicity and convenient maintenance for manganese control of backflow water of a drinking water treatment plant. SUMMARY

[0005] The purpose of the present application is to provide a manganese removal device for backflow water of a drinking water purification plant to solve the problem of excessive manganese concentration in backflow water of a water plant. The present application provides the following scheme: The manganese removal device for backflow water of a drinking water purification plant provided by the present application comprises a water outlet short pipe, a reaction tank, an iron electrode, a carbon electrode and a water inlet short pipe, wherein the reaction tank is a turbulent flow reaction tank, the longitudinal section of the reaction tank is wave-shaped with wave crests and wave troughs, one side of the reaction tank is connected with the water inlet short pipe, the other side of the reaction tank is connected with the water outlet short pipe, the carbon electrode and the iron electrode are installed at the wave trough of the reaction tank, the carbon electrode is located in the upper direction and the iron electrode is located in the lower direction along the water flow direction, the carbon electrode is close to the water inlet short pipe, and the iron electrode and the carbon electrode are cross-installed at an angle of 30°.

[0006] In the present application, a sodium hydroxide dosing pipe is arranged at the water inlet short pipe.

[0007] In the application, the six iron electrodes are evenly distributed at the troughs of the reaction tank and are located on the same plane; the six carbon electrodes are evenly distributed at the troughs of the reaction tank and are located on the same plane.

[0008] In the application, the pipe diameter of the water inlet short pipe and the water outlet short pipe is the same and is smaller than the inner diameter of the reaction tank.

[0009] In the application, the water inlet short pipe is connected to the reflux water pipe through the water inlet, and the water outlet short pipe is connected to the reflux water pipe through the water outlet.

[0010] In the application, the iron electrode and the carbon electrode are respectively connected to the power supply.

[0011] In the application, when running, the newly generated ferrate is dissolved in the reflux water and releases a large amount of oxygen atoms, oxidizes Mn 2+ in the raw water into Mn 4+ which is difficult to dissolve in water, degrades the organic matter therein, and kills the bacteria and viruses in the water; in addition, during the oxidation process, the ferrate is reduced to nascent ferric hydroxide, which is mixed with the Mn 4+ solution at the front end of the reflux, and the remaining ferrate and ferric hydroxide respectively play the oxidation and coagulation functions, further strengthening the treatment efficiency of the existing process of the water plant.

[0012] The beneficial effects of the application are that: when the device is running, the electrodes are connected to the power supply, NaOH solution is added through the sodium hydroxide dosing pipe, iron loses electrons to generate ferrate ions (FeO4 2- ), which can efficiently oxidize the easily soluble Mn 2+ in the reflux water of the drinking water plant into Mn 4+ which is difficult to dissolve. In addition, the wave-shaped pipe electrolytic cell can act as a turbulent tank, as the cross section of the tank body is wave-shaped, with wave crests and troughs, which changes the flow velocity to generate vortexes, intensifying the turbulent effect of the water flow in the reaction tank, significantly improving the electrode reaction efficiency and substrate mixing efficiency, and after FeO4 2- is reduced to nascent Fe(OH)3, it can be refluxed to the front end of the coagulation section to become part of the coagulant, improving the coagulation effect. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a schematic diagram of the process of a water plant.

[0014] Figure 2 is a top view of the device.

[0015] Figure 3 is a front view of the device.

[0016] Figure 4 is an axonometric view of the device.

[0017] The following are the labels in the diagram: 1. Outlet pipe, 2. Reaction tank, 3. Iron electrode, 4. Carbon electrode, 5. Inlet pipe, 6. Sodium hydroxide dosing pipe, 7. Inlet, 8. Outlet. Detailed Implementation

[0018] The technical solution of the present invention will now be described in detail with reference to the embodiments and accompanying drawings: Example 1

[0019] The main body of this device is reaction vessel 2, such as Figures 2-4 As shown. The reaction vessel is a turbulent flow reaction vessel, with an inlet pipe 5 and an outlet pipe 1 connected to the front and rear of the reaction vessel 2, respectively. Six iron electrodes 3 and six carbon electrodes 4 are installed on the cylinder of the reaction vessel 2. Along the water flow direction, the iron electrodes 3 are positioned downwards and the carbon electrodes 4 are positioned upwards, with them intersecting at a 30° angle. Both electrodes are installed in the recessed areas, i.e., the troughs, of the turbulent flow reaction vessel 2. A sodium hydroxide dosing pipe 6 is provided on the inlet pipe 5. The diameters of the inlet pipe 5 and the outlet pipe 1 are the same, both smaller than the inner diameter of the turbulent flow reaction vessel 2.

[0020] During operation, iron electrode 3 and carbon electrode 4 are connected to a power source. NaOH solution is added to the sodium hydroxide dosing tube 6. Iron electrode 3 acts as the anode. Under alkaline conditions, iron loses electrons to generate ferrate ions (FeO4). 2- At the cathode, hydrogen ions gain electrons to generate hydrogen gas. The electrolyte is a sodium hydroxide (NaOH) solution with a concentration of approximately 7 mol / L.

[0021] Because the cross-section of the reaction vessel 2 is wavy with peaks and troughs, the turbulence of the water flow inside the reaction vessel 2 is amplified, which greatly improves the efficiency of electrode reaction and mixing.

[0022] The device's inlet 7 is connected to the return water pipe, and the outlet 8 is connected to the return water pipe. They are installed in parallel, and the water volume is regulated and distributed through valves.

[0023] like Figure 1 As shown, the raw water is treated in a coagulation sedimentation tank, where the filtrate enters the filter tank, the sludge enters the sludge thickening tank, the supernatant in the sludge thickening tank enters the inlet of this device, and the dewatered sludge enters the equalization tank by adding dewatering liquid. Part of the water in the filter tank enters the clear water tank, and the other part enters the equalization tank. The water treated in the equalization tank enters the sludge thickening tank, enters the inlet of this device, and the remainder flows back into the raw water.

[0024] In this embodiment, 100 L of reflux water from a drinking water plant containing Mn was taken and analyzed in the laboratory. The Mn content in the reflux water was... 2+ The concentration is 0.62-0.86 g / m³. 3For comparison with the synchronous electrolysis and mixing performance of the turbulent reaction tank-2 of the application.

[0025] Step 1: 100 L of water sample is evenly divided into two groups, one of which is treated by traditional parallel arrangement of electrochemical electrode plates; the other is treated in the turbulent reaction tank 2 with the added wave tube.

[0026] Step 2: The pre-configured sodium hydroxide is added online through the sodium hydroxide dosing pipe 6 to the front end of the reactor at a dosage of 10 mL / L of 1 mol / L sodium hydroxide solution, and the current density is set to 2750 A / m2. Test analysis shows that the electrolytic cell without the added wave tube can produce 0.76-0.81 mg / L of ferrate; the turbulent reaction tank 2 with the added wave tube of the application can generate 0.85-0.97 mg / L of ferrate, and the electrolytic ferrate and Mn 2+ In the electrolytic cell or turbulent reaction tank 2, the mixture is fully mixed for 55-60 seconds.

[0027] Step 3: According to the dimensionless variance and the Beckley number calculated by the tracer test results, the dimensionless variance of the electrolytic cell without the added wave tube reaches 0.5731-0.6012, the Beckley number reaches 1.2903-1.4130, and the mixing efficiency is 75.3-77.6%; the turbulent reaction tank with the added wave tube of the device reaches 0.6815-0.6932, the Beckley number reaches 1.103-1.2130, and the contact mixing efficiency reaches 91.2-93.7%.

[0028] Step 4: The Mn 2+ in the backflow water reacts with the ferrate oxidant produced by electrolysis to be oxidized to Mn 4+ .

[0029] The treated backflow water is transported to the raw water pool of the water plant, and through the coagulation and sedimentation process, the Mn 4+ is transferred to the sludge phase, and the removal rate of Mn can reach 93.8%. Compared with not using the device to treat the backflow water of the drinking water plant, the gain effect of the device is to increase the ferrate production rate by 11.8-19.8% and the mixing efficiency by 15.9-16.1%. Example 2

[0030] The device shown in Example 1 is used.

[0031] In this example, a certain drinking water plant is used to test the performance of the application. The backflow water quantity of the drinking water treatment plant is 5000 m 3 / d, and the Mn 2+ concentration in the backflow water is 0.53-0.67 g / m 3 .

[0032] Step 1: The pre-configured sodium hydroxide was added online by 10 L / m through the sodium hydroxide feeding pipe 6 3 1mol / L sodium hydroxide solution to the front end of the reactor, and the current density was set to 2750 A / m2. Analysis found that electrolysis under this condition could produce 0.67-0.71 g / m 3 of ferrate oxidant, and the electrolysis produced ferrate was fully mixed with Mn 2+ in the turbulent reaction tank 2 for 60 s.

[0033] Step 2: According to the test results of the tracer method, the dimensionless variance reached 0.6815-0.6932, the Berkeley number reached 1.103-1.2130, and the contact mixing efficiency reached 89.2-90.5%. After sufficient mixing, the solution continued to react in the subsequent conveying pipeline for 3-5 min, and Mn 2+ was completely oxidized to Mn 4+ , and the oxidation efficiency reached 83.7-89.2%.

[0034] Step 3: The treated backflow water was transported to the raw water pool of the water plant, and through the coagulation and sedimentation process, Mn 4+ was transferred to the sludge phase, and the removal rate of Mn could reach 93.8%. Compared with not using the device to treat the backflow water of the drinking water plant, the gain effect of the device is that it reduces the load of 50-60% of the backflow water Mn, and reduces the concentration of Mn in the effluent of the drinking water treatment plant by about 12.2-18.7%.

Claims

1. A manganese removal device for return water in a drinking water purification plant, comprising an outlet short pipe, a reaction tank, an iron electrode, a carbon electrode, and an inlet short pipe, characterized in that: The reaction vessel is a turbulent reaction vessel with a wavy longitudinal section, featuring crests and troughs. One side of the reaction vessel is connected to an inlet pipe, and the other side is connected to an outlet pipe. Carbon and iron electrodes are installed at the troughs of the reaction vessel. Along the water flow direction, the carbon electrode is positioned upwards, and the iron electrode is positioned downwards. The carbon electrode is close to the inlet pipe, and the iron and carbon electrodes are installed at a 30° angle.

2. The manganese removal device for return water in a drinking water purification plant according to claim 1, characterized in that: A sodium hydroxide dosing pipe is installed at the water inlet short pipe.

3. The manganese removal device for return water in a drinking water purification plant according to claim 1, characterized in that: There are 6 iron electrodes, evenly distributed in the troughs of the reaction vessel and located on the same plane; there are 6 carbon electrodes, evenly distributed in the troughs of the reaction vessel and located on the same plane.

4. The manganese removal device for return water in a drinking water purification plant according to claim 1, characterized in that: The inlet and outlet pipes have the same diameter, and are smaller than the inner diameter of the reaction vessel.

5. A manganese removal device for return water in a drinking water purification plant according to claim 1, characterized in that: The inlet short pipe is connected to the return water pipe through the inlet, and the outlet short pipe is connected to the return water pipe through the outlet.

6. A manganese removal device for return water in a drinking water purification plant according to claim 1, characterized in that: The iron electrode and the carbon electrode are connected to the power supply respectively.

7. A manganese removal device for return water in a drinking water purification plant according to claim 1, characterized in that: During operation, the newly generated ferrates dissolve in the return water, releasing a large number of oxygen atoms, which in turn removes Mn from the raw water. 2+ Oxidized to water-insoluble Mn 4+ This process degrades organic matter and kills bacteria and viruses in the water; furthermore, during oxidation, ferrates are reduced to nascent ferric hydroxide, which reacts with Mn... 4+ The mixed liquor is refluxed back to the front end and mixed with the raw water of the water plant. The remaining ferrate and ferric hydroxide perform oxidation and coagulation functions, respectively.

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