In-situ filtering membrane cleaning method

Abstract

A filter membrane cleaning method relates to the technical field of water treatment.Soaking acid water and soaking alkaline water are reversely injected into a filter device through a backwashing pipeline for acid soaking and alkaline soaking, and the volume of a cavity in the reverse position of a filter membrane of the filter device is just filled with the injected acid water or alkaline water; the soaking time of injecting the soaking acid water and the soaking time of injecting the soaking alkaline water are both 1-2 hours, after soaking is completed, the acid water and the alkaline water are drained away, and then clean water is used for back flushing. Compared with the prior art, the device has the advantages that the filtering membrane can be effectively cleaned without additionally arranging a soaking pool, the cleaning time is short, continuous treatment of sewage cannot be obviously influenced, and the cost is low.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a method for cleaning filter membranes. Background Technology

[0002] Currently, medical wastewater treatment in hospitals generally requires secondary biological treatment before disinfection before discharge. Some projects add membrane filtration at the end of the secondary biological treatment process to improve the effectiveness and efficiency of biological treatment, making full use of space (both microbial treatment and filtration equipment require a large space; combining the two can make full use of the limited space in the hospital) and enhancing the system's treatment effect. To fully utilize the filtration capacity of the filtration equipment, the filter membrane needs to be backwashed after a period of use. Clean water is used for backwashing to avoid damaging the microorganisms in the microbial tank. However, since the filtration device is in a microbial environment, microorganisms inevitably grow on the filter membrane. Even with backwashing, the microorganisms attached to the filter membrane are not easily washed out, leading to a significant decrease in the membrane's filtration performance. An effective method to remove microorganisms from the filter membrane is to soak it in acid and alkali to kill the microorganisms. After this, the filtration function can be easily restored through backwashing. One existing method involves transferring the filter membrane to another soaking tank for acid and alkali soaking to avoid killing the microorganisms in the microbial tank. However, this method requires setting up a separate soaking tank, which is limited by environmental constraints and makes it difficult to set up such a tank. Furthermore, the disassembly and reassembly of the filter membrane is labor-intensive and time-consuming, significantly impacting the continuous treatment of wastewater. Another method is to drain the existing membrane tank and then soak it in acid or alkali. However, this method has two drawbacks: first, it requires stopping the entire system during cleaning, posing a risk of wastewater overflow due to insufficient treatment; second, draining the membrane tank is generally impractical. While draining the membrane tank might waste some microbial sludge if it's a separate facility, it's practically impossible if the membrane tank and biological treatment tank are combined. Summary of the Invention

[0003] The purpose of this invention is to provide an in-situ filter membrane cleaning method that eliminates the need for additional soaking or membrane drying tanks, effectively cleans the filter membrane through precise calculations, has a short cleaning time, requires minimal reagents, does not significantly affect the continuous biological treatment of wastewater, and is low-cost and convenient.

[0004] The filter membrane cleaning method of this invention is implemented as follows: A medical wastewater microbial treatment device includes a microbial treatment tank with a filter; a drainage pipe that pumps filtered water to a collection tank via a pumping device; and a backwashing pump that backwashes clean water into the backwashing pipe of the filter. The filter includes an upper pipe, a lower pipe mounted on a support, and hundreds of filamentous filter tubes connected between the upper and lower pipes. An acid dosing device with an acid dosing pump and an alkaline dosing device with an alkaline dosing pump are connected to the backwashing pipe. The filter membrane cleaning method of this invention is implemented by precisely calculating the effective space of the filamentous filter tubes, combined with the flow rate of the dosing pump, the flow rate of the backwashing pump, the dosing concentration, and the soaking concentration. The dosing pump periodically injects soaking acid or soaking alkaline water back into the filter device. Acid or alkali soaking is performed, with periodic backwashing pump assistance. The injection volume, time, backwashing flow rate, backwashing time, and frequency are calculated based on the effective membrane area to ensure the injected acid or alkali solution precisely fills the cavity at the reverse side of the filter membrane, with a concentration sufficient for soaking. The soaking time for either acid or alkali is 0.5-2 hours, determined through process calculations. After injection, allow the solution to settle for 30-60 minutes to ensure thorough contact between the solution and the membrane fiber blockage. After settling, aeration is then activated for 10-20 minutes to dislodge the softened blockage through vibration, achieving the cleaning purpose. Finally, the suction pump is started to drain the soaking acid or alkali solution, followed by backwashing with clean water. Throughout the cleaning process, aeration should not be activated during the injection phase to prevent chemical leakage into the tank; sludge return should be shut off to prevent any leaked chemicals from entering the upstream biological treatment tank and affecting microbial growth. It is recommended to activate sludge return every other day.

[0005] The filamentous filter tubes of the filtration device are filled with acidic or alkaline soaking solution in reverse. This acid or alkaline soaking effectively kills microorganisms on the tube walls and softens inorganic contaminants, allowing for effective removal of inactivated microorganisms and flushing away inorganic particles during backwashing. This prevents active microorganisms or inorganic particles from adhering to the filamentous filter tubes and affecting filtration efficiency. Even if trace amounts of acid or alkaline solution enter the microbial tank during the acid or alkaline soaking process, they will only spread to and be diluted around the filamentous filter tubes within a short time, killing only the microorganisms around the filamentous filter tubes. This will not damage the vast majority of microorganisms in the upstream biological tank. Furthermore, the solution is immediately pumped away by the suction pump. Therefore, this method achieves both the inactivation of microorganisms on the filamentous filter tubes and the preservation of the microbial treatment efficiency of the microbial tank.

[0006] Since there is no need to remove the filtration device from the microbial tank for acid or alkali soaking of the filamentous filter tubes, the process is simple, low-cost, and highly efficient. Acid or alkali soaking is performed only by filling the filamentous filter tubes with acid or alkali solution, avoiding a large amount of acid or alkali water from entering the microbial tank and ensuring the activity of microorganisms in the microbial tank. Therefore, it will not significantly affect the wastewater treatment effect.

[0007] Compared with existing technologies, this invention has the advantages of not requiring frequent removal of the filter device for cleaning, having a long cycle for cleaning the filter device, not significantly affecting the wastewater treatment effect, saving manpower, having high equipment utilization efficiency, and low cost. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the filter membrane cleaning method of the present invention; Figure 2 This is a schematic diagram of the structure of a filamentous filter tube.

[0009] Explanation of reference numerals in the attached drawings: 1-Microbial treatment tank; 2-Filtration device; 3-Filament filter tube; 4-Upper pipe; 5-Lower pipe; 6-Pumping device; 7-Fan; 8-Backwash inlet electric valve; 9-Backwash water pump; 10-Acid dosing device; 1001-Acid dosing pump; 11-Backwash pipe; 12-Alkaline dosing device; 1201-Alkaline dosing pump; 15-Collection tank; 16-Disinfectant dosing device. Detailed Implementation

[0010] The filter membrane cleaning method of the present invention will now be described in further detail with reference to the accompanying drawings and embodiments: As shown in the figure, the wastewater in the microbial treatment tank 1 of the medical wastewater microbial treatment device is treated by microorganisms and then filtered through the curtain-like filamentous filter tubes 3 of the filtration device 2 (hundreds of filamentous filter tubes 3 are connected between the upper pipe 4 and the lower pipe 5, which are mounted on a support to form a component-type filtration device 2; the upper pipe 4 and the lower pipe 5 are connected to the pumping device 6; in use, the filtration device 2 is placed in the microbial treatment tank 1). The filtered water is pumped out by the pumping device 6 into the collection tank 15. In this embodiment, the effective volume of all the filamentous filter tubes 3 of the filtration device 2 is: 780m2 * 0.5L / m2 = 390L = 0.39m3. The disinfectant dosing device 1 is then started. 6. Disinfectant solution is mixed into the filtered water for disinfection. After a period of time (actually after 2 hours of normal operation), the pumping device 6 is turned off, the sewage inlet valve is closed, and the aeration blower 7 is turned off. The backwash inlet electric valve 8 is opened, and the backwash water pump 9 is started to backwash the filamentous filter tubes 3 arranged in a curtain shape. The filamentous filter tubes 3 are backwashed for 5-10 minutes. The backwash flux is calculated based on the area, and the flux is selected as 30-35 L / m2.h. When the backwash is insufficient to restore the filtration efficiency of the filamentous filter tubes 3 (actually after 9 days), the filtration capacity of the filter device 2 drops from 10 tons / hour to below 6 tons / hour. An enhanced backwash process is then carried out, namely: the citric acid soaking acid water dosing device 10 is started and the filamentous filter tubes are fed through the backwash pipe 11. Filter tube 3 is soaked in citric acid solution by reverse injection, or sodium hypochlorite alkaline solution dosing device 12 is started, and sodium hypochlorite alkaline solution is injected into the filamentous filter tube 3 through backwash pipe 11 for sodium hypochlorite alkaline solution soaking. Acid solution dosing device 10 is an acid solution mixing tank. Citric acid and water are added into the acid solution mixing tank according to the set ratio and stirred evenly. Alkaline solution dosing device 12 is an alkaline solution mixing tank. Sodium hypochlorite and water are added into the alkaline solution mixing tank according to the set ratio and stirred evenly. Specifically, by accurately calculating the effective space of filamentous filter tube 3 (membrane filament), combined with the flow rate of citric acid dosing pump 1001 or sodium hypochlorite dosing pump 1201, the delivery flow rate of backwash water pump 9, the dosing concentration, and the soaking concentration, through... The backwash pipe 11 injects citric acid solution or sodium hypochlorite alkaline solution into the filter device 1 in the reverse direction for acid or alkali soaking. The injection volume, injection time, backwash boost flow rate, backwash boost time, and frequency are calculated based on the effective filamentous filter tube 3 (membrane fiber) area. During the continuous injection of citric acid solution and sodium hypochlorite alkaline solution, the backwash water pump 9 is started in stages to ensure that the amount of citric acid solution and sodium hypochlorite alkaline solution injected is just enough to fill the cavity volume of the filamentous filter tube 3 in the reverse direction of the filter device 1, and the concentration meets the soaking requirements. In fact, the total amount of citric acid added is 1800-2200g (specifically 1950g, which requires adding 80 liters of water to the water tank of the acid water dosing device 10 first, and then adding solid citric acid 2).4 kg of sodium hypochlorite is added to filter device 2, stirred thoroughly (total solution approximately 80 liters). The concentration of citric acid is 0.5-3 wt%, added in 4 portions, each lasting 10 minutes. The total amount of sodium hypochlorite added is 0.9-1.1 kg. Sodium hypochlorite alkaline solution is then injected back into the filamentous filter tube 3 through backwash pipe 11 for sodium hypochlorite alkaline soaking. The concentration of sodium hypochlorite added to filter device 2 is 1-3 wt%, added in 5 portions, each lasting 10 minutes. (Specifically, 1 kg of sodium hypochlorite needs to be added to 100 liters of 10 wt% sodium hypochlorite solution in the water tank of the alkaline solution dosing device.) Approximately four 25-liter buckets of citric acid solution or sodium hypochlorite solution were injected. The soaking time for either solution is 0.5-2 hours, determined by process calculations. After injection, the solution should be allowed to settle for 30-60 minutes to ensure thorough contact between the citric acid solution and the blockage on the filamentous filter tube 3. After settling, aeration should be initiated for 10-20 minutes to dislodge the softened blockage through vibration, achieving the cleaning purpose. Finally, the citric acid solution or sodium hypochlorite solution should be drained, followed by a backwash with clean water. During the entire cleaning process, aeration should not be activated during the injection phase to prevent leakage of the citric acid solution or sodium hypochlorite solution into the tank. Sludge return should be shut off to prevent any leakage of citric acid solution or sodium hypochlorite solution into the upstream biological treatment tank, which could affect microbial growth. It is recommended to restart the return flow every other day. After strengthening the backwash process, the filtration capacity of filter device 2 can be restored to over 10 tons / hour. .

[0011] Preferably, during the backwashing process before the enhanced backwashing process, sodium hypochlorite is added sequentially or intermittently once (10 g / L sodium hypochlorite solution is added to the backwash water at a flow rate of 2 L / min for 1.5 min), once with citric acid (30 g / L citric acid solution is added to the backwash water at a flow rate of 2 L / min for 1.5 min), once with sodium hypochlorite (10 g / L sodium hypochlorite solution is added to the backwash water at a flow rate of 2 L / min for 1.5 min), followed immediately by once with citric acid (30 g / L citric acid solution is added to the backwash water at a flow rate of 2 L / min for 1.5 min). Specifically, the cycle is 9 days. For the first three days, backwashing is performed every two hours, followed by the addition of sodium hypochlorite. For the next three days, backwashing is performed every two hours, followed by the addition of citric acid. For the last three days, backwashing is performed every two hours, followed by the addition of sodium hypochlorite, and then the addition of citric acid.

[0012] Because the amount of sodium hypochlorite and citric acid added is small, they act mainly on the filamentous filter tube 3, which significantly affects the attached microorganisms. This causes the microorganisms attached to the filamentous filter tube 3 to easily fall off due to reduced activity or even inactivation. Even if these small amounts of acidic and alkaline substances affect the microorganisms in the biological treatment tank, the impact is slight and will not significantly inactivate the microorganisms in the biological treatment tank. Moreover, the microorganisms will recover quickly in subsequent biological treatment.

Claims

1. A method for cleaning a filtration membrane, characterized by, The medical wastewater microbial treatment device includes a microbial treatment tank with a filtration device, a drainage pipe that pumps filtered water to a collection tank, and a backwashing pipe that backwashes clean water into the filtration device via a backwashing pump. The filtration device includes an upper pipe, a lower pipe mounted on a support, and hundreds of filamentous filter tubes connected between the upper and lower pipes. The backwashing pipe is connected to an acid dosing device with an acid dosing pump and an alkaline dosing device with an alkaline dosing pump. The filter membrane cleaning method of this invention is implemented as follows: by accurately calculating the effective space of the filamentous filter tubes, combined with the flow rate of the dosing pump, the flow rate of the backwashing pump, the dosing concentration, and the soaking concentration, the dosing pump periodically injects soaking acidic or alkaline water into the filtration device for acid or alkaline soaking. The backwash pump is used periodically to assist the process. The amount of acid or alkali injected, the injection time, the backwash boost flow rate, the backwash boost time, and the frequency are calculated based on the effective membrane area. This ensures that the amount of acid or alkali injected is just enough to fill the cavity volume at the reverse side of the filter membrane in the filter device, and the concentration meets the soaking requirements. The soaking time for the acid or alkali is 0.5-2 hours, which is determined through process calculation. After the injection is completed, the filter is allowed to settle for 30-60 minutes to allow the solution to fully contact the membrane fiber blockage. After settling, aeration is turned on for 10-20 minutes to allow the softened blockage to fall off through aeration and vibration, achieving the purpose of cleaning. Finally, the suction pump is started to drain the soaking acid or alkali, and then the filter is backwashed with clean water.

2. The method of claim 1, wherein Citric acid is added to the backwash water in the backwash pipe through a citric acid injection device to form citric acid soaking acid water. This acid water is then injected back into the filter device in the microbial tank through the backwash pipe for acid soaking. After soaking, the citric acid soaking acid water is drained through the drain pipe, with the amount of water drained exceeding the amount injected. Any citric acid soaking acid water that overflowed into the microbial tank near the filter device is drained away. Then, a backwash is performed with clean water. Finally, the solution is injected through a sodium hypochlorite injection device. Sodium hypochlorite is added to the backwash water in the backwash pipe to form a sodium hypochlorite soaking alkaline solution. This alkaline solution is then injected back into the filter device in the microbial tank through the backwash pipe for alkaline soaking. After soaking, the sodium hypochlorite soaking alkaline solution is drained away through the drain pipe. The amount of sodium hypochlorite soaking alkaline solution drained is greater than the amount injected, and any sodium hypochlorite soaking alkaline solution that overflowed into the microbial tank near the filter device is drained away. Then, the filter membrane is backwashed with clean water to complete the cleaning process.

3. The filter membrane cleaning method according to claim 1 or 2, characterized by, During the backwashing process before the enhanced backwashing procedure, sodium hypochlorite is added to the backwash water once sequentially or intermittently, i.e., at a flow rate of 2L / min, adding 10g / L of sodium hypochlorite to the backwash water. Sodium hypochlorite solution for 1.5 min, then citric acid solution for 1.5 min (30 g / L citric acid solution added to backwash water at a flow rate of 2 L / min), then sodium hypochlorite solution for 1.5 min (10 g / L sodium hypochlorite solution added to backwash water at a flow rate of 2 L / min), followed immediately by citric acid solution for 1.5 min (30 g / L citric acid solution added to backwash water at a flow rate of 2 L / min).

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