CN114956312A - Method for cleaning membrane of MBR system for aldehyde-containing wastewater and preventing scaling - Google Patents
Method for cleaning membrane of MBR system for aldehyde-containing wastewater and preventing scaling Download PDFInfo
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- 239000012528 membrane Substances 0.000 title claims abstract description 169
- 238000004140 cleaning Methods 0.000 title claims abstract description 50
- 238000000034 method Methods 0.000 title claims abstract description 17
- 125000002485 formyl group Chemical class [H]C(*)=O 0.000 title claims abstract description 13
- 239000002351 wastewater Substances 0.000 title claims abstract description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 80
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 33
- 239000005708 Sodium hypochlorite Substances 0.000 claims abstract description 28
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 claims abstract description 28
- 238000011001 backwashing Methods 0.000 claims abstract description 22
- 239000008399 tap water Substances 0.000 claims abstract description 22
- 235000020679 tap water Nutrition 0.000 claims abstract description 22
- 230000004907 flux Effects 0.000 claims abstract description 20
- 239000002253 acid Substances 0.000 claims abstract description 18
- 230000020477 pH reduction Effects 0.000 claims abstract description 14
- 239000003814 drug Substances 0.000 claims abstract description 11
- 239000007788 liquid Substances 0.000 claims abstract description 10
- 238000004519 manufacturing process Methods 0.000 claims abstract description 9
- 239000000203 mixture Substances 0.000 claims abstract description 8
- 238000005273 aeration Methods 0.000 claims abstract description 7
- 230000008859 change Effects 0.000 claims abstract description 7
- 239000010802 sludge Substances 0.000 claims abstract description 7
- 230000002265 prevention Effects 0.000 claims abstract description 6
- 239000011550 stock solution Substances 0.000 claims abstract description 5
- 238000005406 washing Methods 0.000 claims description 10
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 8
- 239000000460 chlorine Substances 0.000 claims description 8
- 229910052801 chlorine Inorganic materials 0.000 claims description 8
- 238000002791 soaking Methods 0.000 claims description 7
- 230000001502 supplementing effect Effects 0.000 claims description 4
- 238000011010 flushing procedure Methods 0.000 abstract description 5
- 238000009991 scouring Methods 0.000 abstract 1
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 9
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 9
- 239000005416 organic matter Substances 0.000 description 8
- 150000007524 organic acids Chemical class 0.000 description 7
- 239000000126 substance Substances 0.000 description 6
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 5
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 5
- 239000011575 calcium Substances 0.000 description 5
- 229910052791 calcium Inorganic materials 0.000 description 5
- 239000011777 magnesium Substances 0.000 description 5
- 229910052749 magnesium Inorganic materials 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 239000003513 alkali Substances 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000010842 industrial wastewater Substances 0.000 description 4
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 3
- 229910001424 calcium ion Inorganic materials 0.000 description 3
- 239000003344 environmental pollutant Substances 0.000 description 3
- 238000011065 in-situ storage Methods 0.000 description 3
- 239000002957 persistent organic pollutant Substances 0.000 description 3
- 231100000719 pollutant Toxicity 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
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- 239000011734 sodium Substances 0.000 description 2
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- 238000004611 spectroscopical analysis Methods 0.000 description 2
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- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 238000004971 IR microspectroscopy Methods 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 159000000007 calcium salts Chemical class 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
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- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 238000004065 wastewater treatment Methods 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/02—Aerobic processes
- C02F3/12—Activated sludge processes
- C02F3/1236—Particular type of activated sludge installations
- C02F3/1268—Membrane bioreactor systems
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
- B01D65/02—Membrane cleaning or sterilisation ; Membrane regeneration
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
- B01D65/08—Prevention of membrane fouling or of concentration polarisation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
- B01D2321/04—Backflushing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
- B01D2321/40—Automatic control of cleaning processes
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/06—Controlling or monitoring parameters in water treatment pH
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2303/00—Specific treatment goals
- C02F2303/14—Maintenance of water treatment installations
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/10—Biological treatment of water, waste water, or sewage
Abstract
The invention discloses a method for cleaning and preventing scaling of an MBR system membrane of aldehyde-containing wastewater, which comprises the following steps: cleaning the scaled MBR membrane: aerating and scouring membrane components of the MBR system, and emptying sludge in the membrane tank; adding tap water to immerse the membrane module of the MBR system, and evacuating the muddy water mixture in the membrane tank after aeration; injecting tap water, adding sodium hypochlorite, and keeping the pH constant; emptying sodium hypochlorite liquid medicine, injecting tap water into the membrane tank, aerating and flushing membrane components of the MBR system, and cleaning the sodium hypochlorite liquid medicine; adding hydrochloric acid, and recording pH change and MBR membrane flux data every hour; adding hydrochloric acid to keep the pH constant, and cleaning with tap water; and (3) MBR scaling prevention: adding the hydrochloric acid stock solution and backwashing water into an MBR system membrane module at certain intervals, and keeping the pH value to be 7.5-7.8; the membrane pool pH meter is linked with the backwashing acidification system, the pH value is more than 7.8, the water production of the membrane component of the MBR system is stopped, and the backwashing acidification program is started; when the pH value is less than 7.5, the acid addition is stopped, and the membrane module of the MBR system produces water. The invention slows down membrane pollution, reduces operation pressure and maintains stable PH.
Description
Technical Field
The invention relates to the technical field of industrial wastewater treatment, in particular to an MBR (membrane bioreactor) maintenance technology for aldehyde-containing and organic acid-containing comprehensive wastewater, and more particularly relates to a method for cleaning a membrane of an MBR system for aldehyde-containing wastewater and preventing scaling.
Background
Most of wastewater generated in industries such as petrifaction and pharmaceutical factories contains aldehydes, organic acids and other substances, COD is as high as tens of thousands, other wastewater in the factories needs to be homogenized, and acid and alkali are added into an adjusting tank to be neutral; then the organic matter enters an anaerobic generator to degrade macromolecular organic matter into micromolecular organic matter, then the organic matter enters an AO process, and finally the organic matter is treated by MBR and discharged or recycled after reaching the standard.
The quality of the industrial wastewater fluctuates greatly, but the water quality components are more complex after being homogenized by other water sources. MBR is used as a terminal processing unit, the complicated water quality causes the complicated membrane pollution type, and the conventional chemical cleaning mode has little effect on relieving MBR membrane pollution. For MBR scaling, the existing data introduces that citric acid is adopted to slow down membrane scaling, and citric acid mainly performs a complex reaction with metal ions to increase the solubility of the metal ions, but the citric acid can increase the organic load of a biochemical pool in an MBR system.
Therefore, aiming at the problems that the pH fluctuation is large, the MBR is greatly influenced and the effect of the conventional chemical cleaning method is not ideal in the treatment of inorganic substance mixed type industrial wastewater containing aldehyde, organic acid, calcium, magnesium and the like, an effective method for delaying the scaling of the MBR and the membrane cleaning is developed.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a method for cleaning a membrane of an MBR system for aldehyde-containing wastewater and preventing scaling, which can slow down membrane pollution, reduce operation pressure and maintain stable PH.
The purpose of the invention is realized by the following technical scheme.
The invention relates to a method for cleaning and preventing scaling of an MBR system membrane of aldehyde-containing wastewater, which comprises the following steps:
a first part: fouled MBR membrane cleaning
Firstly, each film is 5-6m 3 Continuously aerating and washing membrane components of the MBR system for 10-30min at a flow rate of/h, and emptying sludge in a membrane tank;
② adding tap water to immerse the membrane component of the MBR system for sufficient aeration, each membrane is 5-6m 3 H/air flow, aerating for 1-4h, and emptying the mud-water mixture in the membrane pool;
sixthly, injecting tap water again, adding 3000ppm sodium hypochlorite and 2000-active chlorine, circulating for 10min, and soaking for 1-6 h; recording the pH value, the residual chlorine and the MBR membrane flux value once per hour, and supplementing 1000ppm of sodium hypochlorite when the pH value is reduced to be more than 0.5 until the pH value is stably controlled to be 11-11.5;
seventhly, sodium hypochlorite liquid medicine is emptied, tap water is injected into the film pool, and each film is 5-6m 3 Continuously aerating and washing membrane components of the MBR system for 10-30min at a gas/h rate, and cleaning sodium hypochlorite liquid medicine;
adding 5000-10000ppm hydrochloric acid into an MBR system membrane component, and recording pH change and MBR membrane flux data every hour; when the pH value is increased to be more than 0.5, adding 1000ppm hydrochloric acid until the pH value is stably controlled to be 0.66-0.97, and cleaning with tap water;
a second part: prevention of MBR scaling
Adding hydrochloric acid stock solution and backwashing water into a membrane module of an MBR system at intervals of 20-30 cycles, wherein the concentration of hydrochloric acid is 200-600mg/L, and the pH around an MBR membrane and a membrane tank is kept between 7.5-7.8;
secondly, adding an online pH meter into the membrane pool, linking the pH meter with the backwashing acidification system, stopping water production of a membrane component of the MBR system when the pH is more than 7.8, starting the backwashing acidification system, and performing a backwashing acidification program; and when the pH value is less than 7.5, stopping adding acid, and starting a membrane module water production mode of the MBR system.
The membrane module of the MBR system is a curtain-type membrane module in the MBR system.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
(1) the invention regularly adopts the backwashing of low-concentration hydrochloric acid (200-. On the other hand, the low-dosage hydrochloric acid concentration can not cause the chloride ion content in water to be greatly increased, and the corrosion of stainless steel equipment such as a membrane frame, a pipeline and the like is slowed down.
(2) In the process of biochemical degradation of the acid after sodium hypochlorite, the aldehyde-containing organic acid industrial wastewater forms organic acid, and the organic acid is biodegraded to generate carbon dioxide and water, so that the pH value in the water is increased, the biochemical efficiency is reduced, and the scale formation of calcium, magnesium and the like in the water is intensified. The invention adopts proper hydrochloric acid to adjust pH value, which can improve the organic matter degradation efficiency of the biochemical system.
(3) The optimized cleaning method saves time, medicament and labor.
(4) The traditional method for preventing the MBR system from scaling is to add hydrochloric acid or sulfuric acid to the tail end of an aerobic tank to adjust the pH value, wherein an acid adding device and a corrosion-resistant pipeline need to be installed again for acid at the tail end of the aerobic tank, so that the equipment investment cost is increased, and the phenomenon of uneven mixing of a membrane tank is easily caused by adding hydrochloric acid at the tail end of the aerobic tank. The invention directly utilizes the existing chemical cleaning system to clean in situ, only needs to modify the automatic control program, and adds hydrochloric acid regularly and quantitatively. The backwashing acid adding system can accurately control the pH value of the periphery of the MBR membrane module by adding hydrochloric acid, and is more favorable for slowing down membrane pollution.
Drawings
FIG. 1 is a scanning electron micrograph of a fouled membrane filament;
FIG. 2 is a scanning electron micrograph of the membrane filaments after acid washing;
FIG. 3 is a graph of a contaminated membrane thread analysis,
wherein, FIG. 3-1 is the analysis of the contaminated membrane by electron microscopy, and FIG. 3-2 is the analysis of the contaminated membrane by energy spectrometry;
figure 4 is a graph of membrane filament before and after alkaline cleaning,
wherein, FIG. 4-1 shows the film filament infrared before and after alkaline cleaning, and FIG. 4-2 shows the film filament appearance before and after alkaline cleaning;
FIG. 5 is a graph of membrane flux change for an acid-first and a base-second wash;
FIG. 6 is a membrane flux change for the sodium first and acid second wash mode.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
The invention relates to a membrane cleaning and scaling prevention method for an MBR system for aldehyde-containing wastewater, which mainly comprises two aspects, wherein one part is cleaning of an MBR membrane which is already scaled, and the other part is preventing scaling of the MBR.
In the first part, cleaning the scaled MBR membrane, and in-situ cleaning mainly comprises the following steps:
firstly, each film is 5-6m 3 And/h/air flow continuously aerating and flushing the membrane module of the MBR system for 10-30min, and emptying the sludge in the membrane tank. Wherein, the MBR system membrane module is a curtain type membrane module in the MBR system.
② adding tap water to immerse the membrane component of the MBR system for sufficient aeration, each membrane is 5-6m 3 H/air flow, aerating for 1-4h, and emptying the mud-water mixture in the membrane pool.
Thirdly, running water is injected again, and 3000ppm sodium hypochlorite with available chlorine of 2000-. And recording the pH value, the residual chlorine and the MBR membrane flux value once per hour, and adding 1000ppm of sodium hypochlorite when the pH value is reduced to be more than 0.5 until the pH value is stable and unchanged, and controlling the pH value to be 11-11.5.
Fourthly, the sodium hypochlorite liquid medicine is emptied, tap water is injected into the membrane pool, and 5 to 6m of each membrane is adopted 3 And/h/air flow, continuously performing aeration flushing on the membrane module of the MBR system for 10-30min, and cleaning the sodium hypochlorite liquid medicine.
Fifthly, adding 5000-10000ppm hydrochloric acid into the membrane module of the MBR system, and recording the pH change and MBR membrane flux data every hour. When the pH value is increased to be more than 0.5, 1000ppm hydrochloric acid is added until the pH value is stable and unchanged, the pH value is controlled to be 0.66-0.97, and the mixture is washed by tap water.
The above cleaning process can restore the MBR membrane flux to 300% from the initial 15L/m2 to 54L/m2 h. The sodium hypochlorite is mainly used for cleaning organic matters on the surface of an MBR membrane, fully scaling calcium, magnesium and other elements on the surface of the membrane, and then cleaning with hydrochloric acid to thoroughly clean inorganic pollution on the surface of the membrane.
A second part: prevention of MBR scaling
Adding hydrochloric acid stock solution and backwashing water into a membrane module of an MBR system at intervals of 20-30 cycles, wherein the concentration of hydrochloric acid is 200-600mg/L, and the pH around an MBR membrane and a membrane tank is kept between 7.5 and 7.8.
Secondly, an on-line pH meter can be added into the membrane pool and linked with the existing backwashing acidification system. When the pH value is more than 7.8, stopping water production of a membrane module of the MBR system, starting a backwashing acidification system, and performing a backwashing acidification program; and when the pH value is less than 7.5, stopping adding acid, and starting a membrane module water production mode of the MBR system.
Example 1: comparison of cleaning modes of fouled MBR membrane
The contaminated membrane filaments are hard in appearance and rough in surface, solid residues fall off, and the contaminated membrane filaments and the membrane filaments cleaned by hydrochloric acid are subjected to scanning electron microscope and energy spectrum analysis on the pollutant elements on the membrane surface, as shown in fig. 1 and 2. As can be seen from FIGS. 1 and 2, agglomerated substances are attached to the surface of the scaled membrane filaments, so that the membrane pores on the membrane surface are blocked, and the pollutants on the membrane surface after cleaning are remarkably reduced. The contaminated membrane filaments were subjected to energy spectrometry as shown in FIG. 3. From the energy spectrum analysis of fig. 3, it can be seen that the contaminating elements on the membrane surface are mainly calcium, and small amounts of magnesium, iron and phosphorus, in addition to the elements of the membrane material itself. The scanning electron microscope also reflects the remarkable cleaning effect of hydrochloric acid on the side surface because the hydrochloric acid cleans calcium and magnesium on the surface of the film.
The membrane filaments before and after sodium hypochlorite washing were subjected to infrared analysis, and as can be seen from fig. 4, the organic matter was reduced in the clean membrane filaments as compared with the contaminated membrane filaments. The contaminated membrane wire has an absorption peak at 1600-1650 nm, and represents an organic matter containing a C-C single bond, and 3100-3300 nm contains an organic pollutant containing a carboxyl group. As can be seen from the combination of FIG. 4-1 and FIG. 4-2, the organic pollutants on the membrane surface are cleaned by sodium hypochlorite, and the membrane flux is further recovered.
As can be seen by infrared and scanning electron microscopy, the pollutants of the MBR system are mainly scale formation caused by calcium salt and organic pollutants caused by organic acid and the like. And respectively adopting two cleaning modes to clean the membrane module of the MBR system under the same pollution state.
The first mode is as follows: each film is 5-6m 3 And/h/air flow continuously aerating and washing a curtain type membrane assembly in the MBR system for 10-30min, and emptying sludge in the membrane tank. Adding tap water, immersing in MBR membrane module, and aerating to 5-6m per membrane 3 And h/air flow, aerating for 1-4h, and emptying the mud-water mixture in the membrane pool. Adding 5000ppm hydrochloric acid, circularly soaking for 2h, supplementing 2000ppm hydrochloric acid, circularly soaking for 1h, washing with clear water to neutrality, adding 2000ppm sodium hydroxide and 2000ppm hydrochloric acid, soaking for 3h, supplementing 1000ppm sodium hydroxide and 1000ppm sodium hypochlorite, and washing with tap water to neutrality.
Adopting a cleaning mode of acid first and alkali secondInitial membrane flux of 18L/m at suction pressure of-0.08 MPa 2 H, after hydrochloric acid cleaning, the membrane flux is increased to 49L/m under the suction pressure of-0.05 MPa 2 H, after the membrane is circularly soaked and cleaned by sodium hydroxide and sodium hypochlorite, the membrane flux is slightly reduced to 47L/m under the suction pressure of-0.05 MPa 2 H, as shown in figure 5. It is seen that acid first and then alkali can only remove inorganic pollution, but not organic pollution effectively.
The second mode is as follows: each film is 5-6m 3 And/h/air flow continuously aerating and washing a curtain type membrane assembly in the MBR system for 10-30min, and emptying sludge in the membrane tank. Adding tap water, immersing in MBR membrane module, and aerating to 5-6m per membrane 3 And h/air flow, aerating for 1-4h, and emptying the mud-water mixture in the membrane pool. 3000ppm sodium hypochlorite is soaked for 4 hours, 5000ppm hydrochloric acid is added after tap water is washed, 1000ppm hydrochloric acid is supplemented after 2 hours, and tap water is washed to be neutral after soaking 2 hours.
Adopting a sodium hypochlorite-acid cleaning mode, and the initial membrane flux is 13L/m when the suction pressure is minus 0.08MPa 2 H, after sodium hypochlorite cleaning, the membrane flux is increased to 54L/m under the suction pressure of-0.05 MPa 2 H, after cyclic soaking and cleaning by hydrochloric acid, the membrane flux of suction pressure-0.03 MPa is increased to 59L/m 2 H as shown in fig. 6. Therefore, the MBR system can be thoroughly cleaned by adopting sodium hypochlorite and then hydrochloric acid.
After the cleaning method in the first mode and the second mode is compared, the operation pressure is lower, and when the suction pressure is-0.03 MPa, the membrane flux is higher and can reach 59L/m 2 H. The membrane cleaning effect is more stable by the cleaning mode of firstly alkali and then acid.
Example 2: fouled MBR membrane cleaning
When the MBR membrane surface is scaled and the membrane filaments are hard, the in-situ cleaning mainly comprises the following steps:
firstly, each film is 5-6m 3 And/h/air flow continuously aerating and flushing the membrane module of the MBR system for 10-30min, and emptying the sludge in the membrane tank. Wherein, the MBR system membrane module is a curtain type membrane module in the MBR system.
② adding tap water to immerse the membrane component of the MBR system for sufficient aeration, each membrane is 5-6m 3 /hAerating for 1-4h, and emptying the mud-water mixture in the membrane pool.
Thirdly, running water is injected again, and 3000ppm sodium hypochlorite with available chlorine of 2000-. And recording the pH value, the residual chlorine and the MBR membrane flux value once per hour, and adding 1000ppm of sodium hypochlorite when the pH value is reduced to be more than 0.5 until the pH value is stable and unchanged, and controlling the pH value to be 11-11.5.
Fourthly, the sodium hypochlorite liquid medicine is emptied, tap water is injected into the membrane pool, and 5 to 6m of each membrane is adopted 3 And/h/air flow, continuously performing aeration flushing on the membrane module of the MBR system for 10-30min, and cleaning the sodium hypochlorite liquid medicine.
Fifthly, hydrochloric acid cleaning is needed, 10000ppm hydrochloric acid is adopted to fully soak membrane components of the MBR system, and a large amount of carbon dioxide bubbles are generated due to the reaction of the hydrochloric acid and calcium carbonate on the surface of the membrane. After the bubbles are eliminated, a circulating system is started, the membrane flux is tested, and 1000ppm hydrochloric acid is supplemented after the membrane is soaked for 1 hour to test the change of the pH value and the increase range of the pH value exceeds 0.5. And (4) until the pH value is stable and is controlled to be 0.66-0.97, and cleaning the membrane module by using tap water.
Example 3: prevention of MBR scaling
After the backwashing acid adding system is started on site, the acid adding device is started every four hours, the hydrochloric acid stock solution and backwashing water are added into the membrane module of the MBR system together, the concentration of the hydrochloric acid is about 400mg/L, the pH around the MBR membrane and the pH of the membrane pool are kept between 7.5 and 7.8, the solubility of calcium ions in the membrane system is increased, the calcium ions permeate the membrane system, the calcium ions are not accumulated on the surface of the membrane, and the operation of the MBR system is stable.
Wherein, an online pH meter is added into the membrane pool and linked with the backwashing acidification system, when the pH value is more than 7.8, the water production of the membrane component of the MBR system is stopped, the backwashing acidification system is started, and a backwashing acidification program is carried out; and when the pH value is less than 7.5, stopping adding acid, and starting a membrane module water production mode of the MBR system.
While the present invention has been described in terms of its functions and operations with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise functions and operations described above, and that the above-described embodiments are illustrative rather than restrictive, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined by the appended claims.
Claims (2)
1. A method for cleaning and preventing scaling of an MBR system membrane of aldehyde-containing wastewater is characterized by comprising the following steps:
a first part: fouled MBR membrane cleaning
Firstly, each film is 5-6m 3 Continuously aerating and washing membrane components of the MBR system for 10-30min at a flow rate of/h, and emptying sludge in a membrane tank;
② adding tap water to immerse the membrane component of the MBR system for sufficient aeration, each membrane is 5-6m 3 H/air flow, aerating for 1-4h, and emptying the mud-water mixture in the membrane pool;
thirdly, running water is injected again, and 3000ppm sodium hypochlorite with available chlorine of 2000 and 3000ppm is added, the circulation is carried out for 10min, and the soaking is carried out for 1 to 6 hours; recording the pH value, the residual chlorine and the MBR membrane flux value once per hour, and supplementing 1000ppm of sodium hypochlorite when the pH value is reduced to be more than 0.5 until the pH value is stably controlled to be 11-11.5;
fourthly, the sodium hypochlorite liquid medicine is emptied, tap water is injected into the membrane pool, and 5 to 6m of each membrane is adopted 3 Continuously aerating and washing membrane components of the MBR system for 10-30min at a gas/h rate, and cleaning sodium hypochlorite liquid medicine;
adding 5000-10000ppm hydrochloric acid into an MBR system membrane module, and recording pH change and MBR membrane flux data every hour; when the pH value is increased to be more than 0.5, adding 1000ppm hydrochloric acid until the pH value is stably controlled to be 0.66-0.97, and cleaning with tap water;
a second part: prevention of MBR scaling
Adding hydrochloric acid stock solution and backwashing water into a membrane module of an MBR system at intervals of 20-30 cycles, wherein the concentration of hydrochloric acid is 200-600mg/L, and the pH around an MBR membrane and a membrane tank is kept between 7.5-7.8;
secondly, adding an online pH meter into the membrane pool, linking the pH meter with the backwashing acidification system, stopping water production of a membrane component of the MBR system when the pH is more than 7.8, starting the backwashing acidification system, and performing a backwashing acidification program; and when the pH value is less than 7.5, stopping adding acid, and starting a membrane module water production mode of the MBR system.
2. The method for cleaning and preventing scaling of membrane of MBR system for aldehyde-containing wastewater according to claim 1, wherein the membrane module of MBR system is a curtain membrane module in MBR system.
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