Restorative cleaning method and device for MBR (Membrane Bio-Reactor) membrane module by utilizing cyclic suction

Abstract

The invention discloses a method and a device for recoverable cleaning of an MBR (Membrane Bio-Reactor) membrane module by utilizing cyclic suction, and relates to the technical field of sewage treatment. Comprising the following steps: adding alkali liquor into a membrane pool, and adding TMPlt into the membrane pool; continuously sucking for 60-120 minutes through a circulating pump under the condition of aeration under the pressure of 60 KPa, monitoring and calculating the water permeability in real time in the sucking process, and ending circulating sucking when the water permeability value is increased, the TMP is reduced and the water permeability value and the TMP tend to be stable and unchanged; emptying the waste liquid in the membrane pool; adding an acid solution into the membrane tank at TMPlt; continuously sucking for 60 to 120 minutes through a circulating pump under the condition of aeration under the pressure of 60 KPa; by adopting staged chemical cleaning and circulating pump dynamic suction control, the closed-loop process of organic pollution decomposition-suction discharge and inorganic crystal dissolution-replacement is realized, and by adopting the process, the TMP recovery rate of the three-year membrane module is greatly improved, the cleaning maintenance period is prolonged, the cleaning time is short, the efficiency is high, and the labor intensity is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the sewage treatment technical field, and in particular to a recovery cleaning method and device of MBR membrane assembly by using cyclic suction. BACKGROUND

[0002] MBR membrane treatment process has been widely used in the field of sewage treatment, especially in the treatment of scattered sewage, due to the characteristics of improved membrane flux, reduced membrane cost and prolonged service life. However, after a period of operation, MBR membranes are easily contaminated to different degrees, and the membrane flux decreases, so that regular recovery cleaning is needed.

[0003] Currently, there are two main ways for recovery cleaning of MBR membrane assembly: one is offline CIP (Clean-In-Place) soaking pool static or low flow rate soaking, the main steps of which are: lifting the membrane assembly out of or emptying the membrane pool; putting the original membrane pool or into an independent CIP soaking pool, and sequentially injecting lye, sodium hypochlorite and acid solution for soaking, during which only membrane pool aeration is used to maintain laminar flow or slight agitation; the other is online maintenance chemical cleaning (MC), the main steps of which are: without stopping production, low-concentration medicament (NaClO) is injected reversely through the water production pump, and circulated for a certain period of time, and an aeration box or perforated pipe aeration is arranged at the bottom of the CIP membrane pool or cleaning pool, and the medicament penetration is assisted by cavitation or bubble scouring, which still belongs to the category of "static soaking + local disturbance".

[0004] The above-mentioned recovery cleaning methods have certain effects, but still have great defects, mainly reflected in: 1. Under static or low flow rate conditions, the organic mud balls and calcium-magnesium crystals that have been decomposed in the inner diameter of the membrane wire cannot be discharged in time, and only rely on diffusion to be discharged, which is easy to cause re-settling and blockage; 2. The medicament does not fully contact with the pollutants deep in the sponge support layer, the reaction time is long, and the recovery rate is low; 3. After static acid washing, Ca 2+ / Mg 2+ re-precipitates due to the rise of pH, which is easy to cause new pollution, 4. The cleaning process includes lifting the membrane, soaking, secondary lifting, and multiple liquid changes, and the whole process needs 24-48h, and 3-4 people are needed to cooperate, so the cleaning cycle is long, and the labor intensity is high; 5. There is a lack of real-time TMP (transmembrane pressure difference) feedback, and the water permeability recovery effect cannot be judged according to the change of transmembrane pressure difference, so the end time is often determined by experience, resulting in "over-washing" or "under-washing"; 6. The large-volume CIP (automatic online cleaning) membrane pool produces 100-200m 3 of high-COD high-salt waste liquid during one cleaning, the cleaning effect is not good or needs to be reworked, resulting in waste of cleaning cost and large amount of waste liquid discharge, which leads to difficulty in centralized treatment of cleaning waste liquid. SUMMARY

[0005] This invention addresses the technical problems of existing MBR membrane module restorative cleaning methods, including secondary deposition of contaminants, insufficient contact between reagents and contaminants, long reaction times, secondary precipitation of crystals, long cleaning cycles, high labor intensity, lack of real-time TMP feedback, and difficulty in centralized treatment of cleaning wastewater. The aim is to provide a method and apparatus for restorative cleaning of MBR membrane modules using a circulating pump. By employing staged chemical cleaning combined with dynamic pump control, a closed-loop process is achieved, involving the decomposition and removal of organic contaminants and the dissolution and replacement of inorganic crystals. This process significantly improves the three-year TMP recovery rate of membrane modules, extends the cleaning and maintenance cycle, shortens cleaning time, increases efficiency, reduces labor intensity, and eliminates the need to modify existing MBR systems. It is suitable for municipal and industrial MBR projects.

[0006] The present invention is achieved through the following technical solution.

[0007] The first objective of this invention is to provide a method for restorative cleaning of MBR membrane modules using cyclic suction, comprising the following steps: Add alkaline solution to the membrane tank. Under aeration conditions with TMP < 60 kPa, continuously pump for 60-120 minutes to decompose and remove organic pollutants. Monitor and calculate the permeability in real time during the pumping process. When the permeability value increases, TMP decreases, and both tend to remain stable, the pumping process ends. Drain the waste liquid from the membrane tank; Add acid solution to the membrane tank, and continuously pump it for 60~240 minutes under aeration conditions with TMP<60KPa to remove calcium and magnesium ions.

[0008] This invention first utilizes a circulating pump to perform dynamic high-flow-rate suction, forcibly carrying away the decomposed organic sludge and dissolved inorganic ions from the inner diameter of the membrane fibers, thus solving the problem of secondary deposition within the 0.1-0.2 mm inner diameter of the membrane fibers. Suction also ensures sufficient contact between the reagent and contaminants deep within the sponge support layer, effectively shortening the reaction time and improving the recovery rate. Then, the waste liquid from alkaline washing is discharged to prevent secondary crystallization or redeposition. Finally, immediately after acid washing, dynamic high-flow-rate suction is performed, continuously extracting the residual liquid from the system to further prevent recrystallization. Furthermore, this invention uses real-time monitoring and calculation of permeability to determine the completion of restorative cleaning, preventing over-washing or under-washing and improving the efficiency of restorative cleaning.

[0009] Therefore, this invention achieves a closed-loop process of organic pollutant decomposition-suction discharge and inorganic crystal dissolution-replacement through staged chemical cleaning and dynamic suction control of circulating pumps. This process significantly improves the TMP recovery rate of membrane modules in three years, extends the cleaning and maintenance cycle, shortens cleaning time and increases efficiency, reduces labor intensity, and eliminates the need to modify existing MBR systems. It is suitable for municipal and industrial MBR projects.

[0010] Furthermore, physical loosening is also included before adding alkaline solution into the membrane tank: Control TMP < 60 kPa, continuously pump for 30-60 minutes in clean water condition to remove loose sludge, and then drain.

[0011] Furthermore, the alkaline solution formulation includes sodium hydroxide, sodium hypochlorite, and recycled water, wherein the mass concentration of sodium hydroxide added is 0.05-0.1%, and the mass concentration of sodium hypochlorite added is 1000-3000 PPM.

[0012] It should be noted that the greywater comes from the permeate of the MBR membrane and has low water quality requirements, with a pH close to neutral and a turbidity of less than 10 NTU. This invention uses the addition of alkali or acid to the greywater to prepare the cleaning solution, which can effectively reduce costs.

[0013] Preferably, the sodium hypochlorite concentration is 1000-1500 PPM.

[0014] Furthermore, the permeability is calculated by monitoring the TMP curve changes using a vacuum pressure transmitter installed at the inlet of the circulating pump.

[0015] Furthermore, draining the waste liquid from the membrane tank specifically includes: After adding water to the membrane tank to fully dilute the waste liquid, drain the tank. When the pH of the waste liquid is neutral, proceed to the next step.

[0016] Furthermore, the acid solution formulation includes citric acid and water, wherein the mass concentration of the added citric acid is 1-2%.

[0017] Preferably, the citric acid added has a mass concentration of 1%.

[0018] A second objective of this invention is to provide a regenerative cleaning device for MBR membrane modules using cyclic suction, for use in the aforementioned method, comprising: A circulating pump with an inlet and an outlet; The inlet pipe connects to the inlet of the circulating pump and is used to connect to the main permeate pipe of the membrane tank. A vacuum pressure transmitter is installed at the inlet of the circulating pump to monitor TMP; The outlet pipeline connects to the outlet of the circulation pump and extends deep into the membrane tank; The flow meter is installed at the outlet of the circulating pump.

[0019] The device of the present invention calculates the total permeability (TMP) by setting a vacuum pressure transmitter at the inlet of the circulating pump and a flow meter at the pump outlet. It calculates the permeability based on the transmembrane pressure difference, flow rate, and actual effective filter membrane area, and judges the completion of restorative cleaning based on the recovery effect of permeability, thereby preventing "over-cleaning" or "under-cleaning" and improving the efficiency of restorative cleaning.

[0020] Furthermore, the inlet pipeline includes an inlet rigid pipe and an inlet flexible pipe connected in sequence, and the outlet pipeline is an outlet flexible pipe.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] 1. The restorative cleaning method of this invention first utilizes the "dynamic" high-flow-rate suction of a circulating pump to force the decomposed organic mud and dissolved inorganic ions out of the inner diameter of the membrane fibers, solving the problem of secondary deposition in the inner diameter of the membrane fibers (0.1-0.2 mm). The suction also allows the agent to fully contact the pollutants deep in the sponge support layer, effectively shortening the reaction time and improving the recovery rate. Then, the waste liquid from alkaline washing is discharged to prevent secondary crystallization or redeposition. Finally, after acid washing, "dynamic" high-flow-rate suction is performed immediately, and the residual liquid is continuously extracted from the system to further avoid recrystallization.

[0023] 2. The restorative cleaning method of the present invention achieves a closed-loop process of organic pollutant decomposition-suction discharge and inorganic crystal dissolution-replacement through staged chemical cleaning and dynamic suction control of circulating pump. This process significantly improves the TMP recovery rate of membrane modules, extends the cleaning and maintenance cycle, shortens cleaning time and increases efficiency, reduces labor intensity, and does not require modification of existing MBR systems. It is suitable for municipal and industrial MBR projects.

[0024] 3. The device of the present invention calculates TMP by setting a vacuum pressure transmitter at the inlet of the circulating pump and a flow meter at the outlet of the pump. It calculates the permeability based on the transmembrane pressure difference, flow rate and actual effective filter membrane area, and judges the completion of restorative cleaning based on the recovery effect of permeability, thereby preventing "over-cleaning" or "under-cleaning" and improving the efficiency of restorative cleaning. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings: Fig. 1 This is a plan view of the device of the present invention; Fig. 2 This is an elevation view of the device of the present invention.

[0026] The attached diagram shows the markings and corresponding component names: 1-Circulating pump, 2-Inlet rigid pipe, 3-Inlet flexible hose, 4-Vacuum pressure transmitter, 5-Outlet flexible hose, 6-Flow meter. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0028] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0029] The "scope" disclosed in this invention is defined in the form of a lower limit and an upper limit. A given scope is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific scope. The scope defined in this way can include or exclude end values, and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a scope.

[0030] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0031] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0032] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other substances not listed may also be included, or that only the listed substances may be included.

[0033] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0034] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0035] It should be noted that, unless otherwise specified, the experimental methods used in the embodiments are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0036] Example 1

[0037] A regenerative cleaning device for MBR membrane modules using cyclic suction, such as Figs. 1-2 As shown, it includes: Circulating pump 1 has an inlet and an outlet; specifically, circulating pump 1 can be a horizontal self-priming pump (Q=50 m). 3 / h, H=12m, N=3 kW, flow-through components SS304 / fluororubber, resistant to pH 1-14, resistant to NaClO≤5000 mg / L); The inlet pipe is connected to the inlet of the circulating pump 1 and is used to connect to the main permeate pipe of the membrane tank. The inlet pipe includes an inlet rigid pipe 2 and an inlet flexible pipe 3 connected in sequence. The inlet rigid pipe 2 can be a DN100 SS304 rigid pipe, and the inlet flexible pipe 3 can be a DN100 PVC steel wire flexible pipe. The inlet rigid pipe 2 and the inlet flexible pipe 3 are connected by a clamp. The inlet flexible pipe 3 is connected to the interface of the main permeate pipe of the membrane tank. Vacuum pressure transmitter 4 (-1 bar to +1 bar) is installed at the inlet of circulating pump 1 to monitor TMP; The outlet pipeline is an outlet hose 5, which is connected to the outlet of the circulation pump 1 and extends into the membrane tank. The outlet hose 5 can be a DN100 PVC steel wire hose. Flow meter 6 is installed at the outlet of circulating pump 1 and connected via a flange. The specific model can be LZB-100S-RL-10-50.

[0038] The device of the present invention calculates the TMP by setting a vacuum pressure transmitter 4 at the inlet of the circulating pump 1 and a flow meter 6 at the pump outlet. It calculates the permeability based on the transmembrane pressure difference, flow rate, and actual effective filter membrane area, and judges the completion of restorative cleaning based on the recovery effect of permeability, thereby preventing "over-cleaning" or "under-cleaning" and improving the efficiency of restorative cleaning.

[0039] Example 2

[0040] A method for restorative cleaning of MBR membrane modules using cyclic suction includes the following steps:

[0041] S1, Physical loosening

[0042] Tighten the DN100 quick-connect clamp between the inlet hose of the circulating pump and the main permeate pipe of the membrane tank, and place the outlet hose inside the membrane tank. The membrane tank consists of n membrane frames forming one membrane module. In principle, the circulating pump should be operated to pump water at a flow rate of 1.5 to 3 times the original design flux of a single membrane frame. At the beginning, observe the TMP change. If it exceeds 60 kPa, reduce the pump flow rate and control the TMP to be below 60 kPa. Pump continuously for 30 to 60 minutes. The actual duration is determined according to the TMP change curve. Remove loose sludge in the clear water state. Finally, empty the tank.

[0043] The TMP curve change refers to the following: In the initial stage of suction, the membrane flux is restricted due to fouling and blockage of the functional layer and sponge support layer of the membrane module. As the pollutants are suctioned out of the system, the flux will increase, and the TMP will decrease. However, this only applies to loose and easily peeled pollutants. When the TMP curve changes gradually or stops changing, the suction step is considered to be over.

[0044] S2, Alkali Washing

[0045] Add greywater to the membrane tank, and add sodium hydroxide and sodium hypochlorite, wherein the mass concentration of sodium hydroxide added is 0.05-0.1%, and the mass concentration of sodium hypochlorite added is 1000-3000 PPM; After the addition is completed, suction is performed, and the suction is controlled below TMP < 60 kPa. The membrane tank is continuously suctioned for 60-120 minutes under aeration, and the actual time is determined according to the TMP change curve. During the suction process, the permeability is calculated by the change of the TMP curve of the vacuum pressure transmitter in front of the pump. The permeability value increases and the TMP decreases. When both tend to remain stable, the cycle suction ends.

[0046] The TMP curve change refers to the following: In the initial stage of suction, the membrane flux is limited by organic pollutants attached to or clogging the functional layer and sponge support layer of the membrane fibers. As the organic pollutants are decomposed and suctioned out of the system, the flux will increase, that is, the TMP will decrease. The decomposition and removal rate of organic pollutants and clogging pollutants is proportional to time. When the TMP curve changes gradually or no longer changes, the suction is considered to be over.

[0047] The formula for calculating the transmembrane pressure (TMP) difference is: TMP = 9.8 × (H) 液 -H 表 )-P(KPa), Wherein: H 液 The membrane tank liquid level height is read in real time by the membrane tank level gauge, in meters; H 表 The elevation of the permeate pressure gauge relative to the bottom of the membrane tank, in meters (m). P is the vacuum pressure transmitter reading, in kPa;

[0048] Permeability is expressed as the amount of water produced by a membrane system per unit TMP, per unit time, and per unit membrane area. It is generally converted to the amount of water produced per unit time per unit membrane area under 1 bar pressure. Permeability = L / m 2 / h / bar Where: L is the water flow rate through the pump per unit time (L / h). m 2 The actual effective filtration membrane area (m²) 2 ); bar is the transmembrane pressure difference TMP (bar). h represents a unit of time, specifically 1 hour.

[0049] Existing static soaking technologies lack real-time TMP (transmembrane pressure difference) feedback, making it impossible to monitor changes in transmembrane pressure difference online to judge the permeability recovery effect. The end time is often determined by experience, resulting in "overwashing" or "underwashing". This invention avoids the phenomenon of "overwashing" or "underwashing" by monitoring TMP in real time during the suction process. At the same time, the agent is fully introduced into all parts of the membrane fibers by the circulation pump, so that the organic pollutants in the membrane fiber sponge support layer are chemically decomposed and carried out of the inner diameter of the membrane fibers by the pulsating flow.

[0050] S3, Wastewater discharge + pH neutralization with reclaimed water

[0051] After alkaline washing is completed, the membrane tank is drained after being thoroughly diluted with water through multiple replenishment processes. The waste liquid is then drained into a waste liquid neutralization tank. Once the pH of the alkaline washing waste liquid is checked and found to be close to neutral, the process proceeds to the next step.

[0052] S4, Pickling-Dynamic Displacement

[0053] Add greywater to the membrane tank and add citric acid at a concentration of 1-2% by mass. Immediately after addition, the circulating pump should be used for suction. The suction should be controlled below TMP < 60 kPa. The membrane tank should be continuously suctioned for 60 to 240 minutes under aeration. The actual duration should be determined according to the TMP change curve.

[0054] In this step, the chemical reagent initially arrives on the outer side of the membrane fiber's inner diameter. A circulating pump draws the highly concentrated reagent mixture from the outside of the membrane fiber through the functional layer and sponge support layer into the inner diameter. After the chemical reaction, the concentration decreases. The circulating pump continuously and dynamically replaces this high-concentration reagent with the inner diameter, while the low-concentration reagent and decomposed inorganic scale are extracted and returned to the outer diameter side of the membrane fiber. Therefore, this step effectively removes dissolved Ca from the micropores of the functional layer and sponge support layer after scaling. 2+ / Mg 2+ It is carried out from the inner diameter of the membrane filament by the pulsating flow, thus avoiding recrystallization.

[0055] The above-described process steps of this invention first utilize the "dynamic" high-flow-rate suction of a circulating pump to force the decomposed organic sludge and dissolved inorganic ions out of the inner diameter of the membrane fibers, solving the problem of secondary deposition in the inner diameter of the membrane fibers (0.1-0.2 mm). Suction also ensures sufficient contact between the reagent and pollutants deep within the sponge support layer, effectively shortening the reaction time and improving the recovery rate. Then, the waste liquid from alkaline washing is discharged to prevent secondary crystallization or redeposition. Finally, immediately after acid washing, "dynamic" high-flow-rate suction is performed, and the residual liquid is continuously extracted from the system to further prevent recrystallization. Furthermore, this invention uses real-time monitoring and calculation of permeability to determine the completion of restorative cleaning, preventing "over-washing" or "under-washing" and improving the efficiency of restorative cleaning.

[0056] Application Example 1

[0057] Chaonan Xinhuan Waterworks Project: Phase II, offline chemical cleaning of membrane modules 1-14, with a design flux of 17.14 L / m³. 2 The total membrane area of ​​the 8 membrane frames is 13,376 m². 2 ;

[0058] Based on this, a method for restorative cleaning of MBR membrane modules using cyclic suction is provided, comprising the following steps: (1) Draining the membrane tank: Add water to the membrane tank and aerate for 30 minutes, then drain the membrane tank. Repeat this process twice. (2) Physical loosening: The membrane tank is replenished with water, and the connection is cleaned, the pumping is cleaned and circulated, and aeration and pumping are carried out. The pumping is run for 30 minutes. According to the TMP change curve, the pumping is carried out for an average of 5-8 minutes for every 2 membrane frames of the 8 membrane frames. (3) Alkaline washing: The membrane tank is emptied and replenished with water for alkaline chemical cleaning. The dosage of sodium hydroxide (solid) is 150 kg (about 0.1% mixed solution concentration) and 10% sodium hypochlorite is 3000 kg (about 1500 PPM mixed solution concentration). Aeration is performed and the cleaning circulation pump is run for 2 hours. According to the TMP change curve, the 8 membrane frames are circulated an average of 5 times, and each time 2 membrane frames are pumped for 4~6 minutes. (4) Draining alkaline washing waste liquid from membrane tank: a. Add water and turn on aeration for 30 minutes, b. Drain, c. Check the pH of alkaline washing waste liquid, cycle steps a, b, and c twice, and drain the water in membrane tank when the pH is less than 7.8. (5) Acid washing: Fill the membrane tank with water until it submerges the top of each membrane frame, add 1500 kg of solid citric acid (about 1% mixed solution concentration) for aeration and run the cleaning circulation pump for 4 hours. According to the TMP change curve, the 8 membrane frames are circulated an average of 10 times, and each time 2 membrane frames are pumped for 4~6 minutes. (6) Empty the membrane tank and resume operation.

[0059] The detection data before and after cleaning in this application example 1 are shown in Table 1.

[0060] Table 1. Test data before and after cleaning

[0061] Comparative Example 1

[0062] The difference between this comparative example and the application case is that it does not use a circulating pump for suction, but instead uses conventional aeration and stirring.

[0063] Table 2. Comparison of detection data between Application Example 1 and Comparative Example 1

[0064] The detection data from Application Example 1 and Comparative Example 1 show that: Compared to conventional aeration and stirring, this invention uses a circulating pump combined with chemical agents to perform restorative cleaning of the MBR membrane module. After cleaning, the permeability increases significantly, reaching 195 LMH / bar, while Comparative Example 1 only has 66 LMH / bar. After 30 days of operation, the permeability of this invention can still reach 158 LMH / bar, while the permeability of Comparative Example 1 is only 48 LMH / bar. After 60 days of operation, the TMP of this invention is less than 20 kPa, while the TMP of Comparative Example 1 is greater than 35 kPa, and restorative cleaning is already required.

[0065] Application Example 2

[0066] 1. Experimental setup: MBR system of Chengdu No. 4 Reclaimed Wastewater Treatment Plant, PVDF hollow fiber membrane module 21160 m², operating flux 17.14 L / m² / h.

[0067] 2. Operating cycle: Replaced and put into use in April 2021, continuously operating for 4.5 years, and undergoing restorative cleaning when the transmembrane pressure difference (TMP) reaches ≥35 kPa.

[0068] 3. Cleaning parameters: Alkaline washing: NaClO 1000ppm + NaOH 0.05% + dilute water, dynamically pumped at 24.7L / h for 30 min; Pickling: 1% citric acid + diluted water, dynamic replacement 24.7 L / h, 30 min; The circulation pump frequency was maintained at 50 Hz at each step, and the membrane shear force was ≥1200 s. -1 .

[0069] 4. Testing Method: TMP recovery rate = (TMP before cleaning - TMP after cleaning) / TMP before cleaning × 100% Dry weight of membrane fibers: Cut a section of membrane fiber, dry it at 105 °C to constant weight, and weigh it using an electronic balance (0.1 mg). Ca 2+ / Mg 2+ Samples were taken after the outlet pH was stabilized >5.5 using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0070] 5. Results Data: Before cleaning, TMP was 38 kPa; after cleaning, it was 6.75 kPa, with a TMP recovery rate of 82.3%. The dry weight of the membrane fibers after acid washing decreased from 21.4 mg / cm³. -1 Decreased to 8.9 mg cm -1 The weight loss ratio is 2.39 times; Outlet residual liquid Ca 2+ +Mg 2+ 42 mg L -1 Less than 50 mg L -1 Threshold, no secondary crystallization.

[0071] 6. Labor time: 2 people, 8 hours to complete; the subsequent operation cycle is extended from 45 days to >90 days, and the labor intensity is reduced by 70% (based on cleaning time).

[0072] In summary:

[0073] This invention employs a "dynamic suction with a cleaning circulation pump" to forcefully remove organic clumps and inorganic crystals from the micropores of the membrane fiber functional layer and sponge support layer, as well as from the inner diameter of the membrane fibers, using high shear force. This increases the TMP recovery rate of the PVDF membrane module to over 85%, significantly improving the TMP recovery rate. The residual liquid Ca... 2+ / Mg 2+ With a concentration of <50 mg / L, secondary crystallization is eliminated; the entire cleaning process requires only 2 people and can be completed in 8 hours, resulting in short cleaning time and high efficiency; the cleaning cycle is extended from 45 days to more than 90 days, and the labor intensity is reduced by 70%.

[0074] Finally, it should be noted that the above specific embodiments are only used to describe the purpose, technical solution, and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation of the present invention and is not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing specific embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions or improvements can be made to some or all of the technical features. These modifications, equivalent substitutions, and improvements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for restorative cleaning of MBR membrane modules using cyclic suction, characterized in that, Includes the following steps: Add alkaline solution to the membrane tank. Under aeration conditions with TMP < 60 kPa, continuously pump for 60-120 minutes to decompose and remove organic pollutants. Monitor and calculate the permeability in real time during the pumping process. When the permeability value increases, TMP decreases, and both tend to remain stable, the pumping process ends. Drain the waste liquid from the membrane tank; Add acid solution to the membrane tank, and continuously pump it for 60~240 minutes under aeration conditions with TMP<60KPa to remove calcium and magnesium ions.

2. The method for restorative cleaning of MBR membrane modules using cyclic suction according to claim 1, characterized in that, Before adding alkaline solution to the membrane tank, physical loosening is also required: Control TMP < 60 kPa, continuously pump for 30-60 minutes in clean water condition to remove loose sludge, and then drain.

3. The method for restorative cleaning of MBR membrane modules using cyclic suction according to claim 1, characterized in that, The alkaline solution formulation includes sodium hydroxide, sodium hypochlorite, and recycled water, wherein the mass concentration of sodium hydroxide added is 0.05-0.1%, and the mass concentration of sodium hypochlorite added is 1000-3000 PPM.

4. The method for restorative cleaning of MBR membrane modules using cyclic suction according to claim 3, characterized in that, The sodium hypochlorite concentration is 1000-1500 PPM.

5. The method for restorative cleaning of MBR membrane modules using cyclic suction according to claim 1, characterized in that, The permeability is calculated by monitoring the TMP curve changes using a vacuum pressure transmitter installed at the inlet of the circulating pump.

6. The method for restorative cleaning of an MBR membrane module using cyclic suction according to claim 1, characterized in that, Draining the waste liquid from the membrane tank specifically includes: After adding water to the membrane tank to fully dilute the waste liquid, drain the tank. When the pH of the waste liquid is neutral, proceed to the next step.

7. The method for restorative cleaning of an MBR membrane module using cyclic suction according to claim 1, characterized in that, The acid solution formulation includes citric acid and water, and the mass concentration of the added citric acid is 1-2%.

8. The method for restorative cleaning of an MBR membrane module using cyclic suction according to claim 7, characterized in that, The citric acid added has a mass concentration of 1%.

9. A regenerative cleaning device for MBR membrane modules using cyclic suction, used in the method of claim 1, characterized in that, include: A circulating pump with an inlet and an outlet; The inlet pipe connects to the inlet of the circulating pump and is used to connect to the main permeate pipe of the membrane tank. A vacuum pressure transmitter is installed at the inlet of the circulating pump to monitor TMP; The outlet pipeline connects to the outlet of the circulation pump and extends deep into the membrane tank; The flow meter is installed at the outlet of the circulating pump.

10. The MBR membrane module restorative cleaning device using cyclic suction according to claim 9, characterized in that, The inlet pipeline includes an inlet rigid pipe and an inlet flexible pipe connected in sequence, and the outlet pipeline is an outlet flexible pipe.

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