CN112933993A - Method for cleaning nanofiltration membrane - Google Patents

Method for cleaning nanofiltration membrane Download PDF

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Publication number
CN112933993A
CN112933993A CN202110376380.9A CN202110376380A CN112933993A CN 112933993 A CN112933993 A CN 112933993A CN 202110376380 A CN202110376380 A CN 202110376380A CN 112933993 A CN112933993 A CN 112933993A
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Prior art keywords
cleaning
nanofiltration membrane
washing
membrane
pure water
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CN202110376380.9A
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CN112933993B (en
Inventor
李天玉
唐娜
陈亦力
王志栋
郭莎莎
张佩瑶
王龙龙
吕学敏
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Beijing Huateyuan Technology Co ltd
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Biyuan Water Source Membrane Technology Research Center Beijing Co ltd
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    • 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
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/027—Nanofiltration
    • 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
    • B01D2321/16—Use of chemical agents
    • B01D2321/162—Use of acids
    • 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
    • B01D2321/16—Use of chemical agents
    • B01D2321/164—Use of bases
    • 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
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Abstract

The invention provides a method for cleaning a nanofiltration membrane, which comprises the following steps: in the operation process of the nanofiltration membrane, water is fed for 8-16m every 6h3Flushing a nanofiltration membrane for 150 s/h, wherein the flux attenuation of the nanofiltration membrane is less than or equal to 30%, preparing EDTA-4Na with the mass fraction of 0.3%, adding NaOH to adjust the pH value to 11-12, and performing cleaning for 15min and soaking for 0.5h for alternative treatment, wherein the total time is 2 h; adding hydrochloric acid to adjust pH to 2-3, washing for 15min and soaking for 0.5h alternately, wherein the washing time is 2 h; washing with pure water to neutrality; when flux of nanofiltration membrane is attenuated>30 percent, preparing EDTA-4Na with the mass fraction of 0.5 percent, adding NaOH to adjust the pH value to 11-12, washing for 15min and soaking for 0.5h for alternative treatment for 4 h; adding hydrochloric acid to adjust pH to 2-3, washing for 15min, and soaking for 0.5 hr for 2 hr; washing with pure water to neutrality.

Description

Method for cleaning nanofiltration membrane
Technical Field
The invention relates to the technical field of nanofiltration membranes, in particular to a method for cleaning a nanofiltration membrane.
Background
With the improvement of the water quality index of the drinking water and the deep understanding of people on the concept of healthy drinking water, the nanofiltration membrane is widely applied to the advanced treatment of the drinking water. The nanofiltration membrane has the advantages that other membranes are difficult to compare with the ultrafiltration membrane, and has high retention rate on small molecular organic matters and micro-pollutants in water compared with the ultrafiltration membrane; compared with a reverse osmosis membrane, the nanofiltration membrane has low water inlet pressure, large flux and low desalination rate, can retain mineral substances, and the produced water meets the requirements of people on healthy drinking water. However, a certain low-desalination nanofiltration membrane is used for nearly 3 months for water produced by the conventional process, the water permeability coefficient of the membrane is reduced to 5.5LMH/bar from 13.1LMH/bar, and the reduction rate of the water permeability coefficient reaches 58.02%. The pollution of the nanofiltration membrane in the process operation and the reduction of the membrane flux, the shortening of the service life of the membrane element, the increase of energy consumption and the increase of cost caused by the pollution are the main problems in the prior nanofiltration operation and use process. Membrane cleaning is the most effective way to deal with membrane fouling at present as a means for rapid flux recovery.
Chemical agent cleaning is the main means for slowing the pollution of the nanofiltration membrane and reducing the operating pressure. At present, chemical cleaning of the nanofiltration membrane mainly comprises acid cleaning and alkali cleaning. The acid washing can dissolve and clean inorganic salt scale formed by inorganic ions on the surface of the membrane, and the alkali washing is mainly used for eluting organic pollutants accumulated on the surface of the membrane. However, the acid washing can enhance the shrinkage cavity effect of the nanofiltration membrane, and the alkali washing can cause the increase of the membrane pores and influence the interception performance of the nanofiltration membrane. The conventional nanofiltration membrane cleaning method comprises the steps of citric acid cleaning and EDTA-4Na cleaning, but the problems of high flux caused by swelling and enlargement of membrane pores and easy pollution caused by sudden increase of TMP in a short time exist after the EDTA-4Na cleaning, and frequent chemical cleaning uses a large amount of chemical agents, so that the agent is wasted, residual medicines can cause membrane damage, the utilization rate of the nanofiltration membrane is reduced, economic waste is caused, and deeper environmental pollution is caused.
Therefore, a nanofiltration membrane cleaning method which can delay membrane pollution, save cleaning steps and cleaning cost and improve the sudden increase of TMP after cleaning is needed.
Disclosure of Invention
The invention provides a method for cleaning a nanofiltration membrane, which aims to overcome the defects in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme.
A method for cleaning a nanofiltration membrane comprises the following steps:
s1 when flux attenuation of the nanofiltration membrane is less than or equal to 30%, the following steps are adopted:
s11 alkaline washing:
preparing EDTA-4Na with the mass fraction of 0.1-1% in an alkaline washing tank, adding NaOH to adjust the pH value to 11-12, introducing the adjusted cleaning liquid into a nanofiltration membrane through a cleaning pump, and alternately cleaning for 15min and soaking for 0.5h, wherein the total cleaning time is 1-4 h;
s12 acid washing:
after alkaline washing, adding acid into a pickling tank to adjust the pH value to 2-3, feeding the adjusted cleaning solution into a nanofiltration membrane through a cleaning pump, and controlling the flow velocity of the cleaning solution to be 6-8m3Cleaning for 15min and soaking for 0.5h alternately, wherein the total cleaning time is 1-4h, and the temperature of the cleaning liquid is 20-40 ℃;
s13 rinsing with pure water:
after alkaline washing, pure water enters a nanofiltration membrane through a washing pump until the pH value of the effluent is recovered to be neutral;
s2 when flux attenuation of the nanofiltration membrane is more than 30%, the following steps are adopted:
s21 alkaline washing:
EDTA-4Na with the mass fraction of 0.3% -1% is prepared in an alkaline washing tank, NaOH is added to adjust the pH value to 11-12, the adjusted cleaning liquid enters a nanofiltration membrane through a cleaning pump, cleaning is carried out for 15min and soaking is carried out for 0.5h alternately, and the total cleaning time is 2-6 h;
s22 acid washing:
after alkali washing, adding acid into a pickling tank to adjust the pH value to 2-3, feeding the adjusted cleaning solution into a nanofiltration membrane through a cleaning pump, and alternately cleaning for 15min and soaking for 0.5h, wherein the total cleaning time is 1-4 h;
s23 rinsing with pure water:
after acid washing, pure water enters the nanofiltration membrane through a cleaning pump until the pH value of the effluent is recovered to be neutral.
Preferably, in the method, the flow rate of the cleaning liquid and the water is controlled to be 6-8m3The temperature of the cleaning liquid and the pure water is 20-40 ℃.
Preferably, the method further comprises: in the operation process of the nanofiltration membrane, pure water is used for 8-16m every 4-12 h3Flushing the nanofiltration membrane for 100 s-5 min at a flow rate of/h, and refluxing the flushed liquid to the front end for water inlet or directly discharging.
Preferably, pure water is used for 8-16m every 6h during the operation of the nanofiltration membrane3The nanofiltration membrane is washed for 150s at the flow rate of/h.
Preferably, in the method, the mass fraction of EDTA-4Na in S11 alkaline washing is 0.3%, and the mass fraction of EDTA-4Na in S21 alkaline washing is 0.5%.
According to the technical scheme provided by the method for cleaning the nanofiltration membrane, the method has the following beneficial effects:
1) under the condition of not influencing the recovery rate, the pure water flushing can reduce the pollution rate of the nanofiltration membrane, thereby prolonging the cleaning period of the chemical agent and saving the operation and maintenance cost.
2) According to the severity of the nanofiltration membrane pollution, different chemical agent cleaning schemes are selected, and agents and cleaning time can be saved.
3) The method of cleaning EDTA-4Na and then pickling is adopted in the cleaning sequence of the agent, so that the characteristic of the shrinkage effect of the nanofiltration membrane is enhanced, and the problems of increased membrane pores and reduced interception performance caused by alkaline washing of EDTA-4Na are solved.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic view of an automatic control flushing process of this embodiment 1;
figure 2 is a graph comparing the membrane specific flux results of the nanofiltration membranes flushed at different time intervals using the method of example 1;
FIG. 3 is a graph comparing the results of membrane specific flux after caustic and acid cleaning using the method of example 2;
FIG. 4 is a graph comparing the membrane specific flux results after acid washing using the method of example 3;
FIG. 5 is a graph comparing the specific flux results for membranes with flux decay > 30% using the alkaline plus acid wash protocol of example 2 with flux decay < 30%;
description of reference numerals:
the water outlet valve is connected with a water inlet valve, a first section concentrated water valve, a second section concentrated water valve, a first section concentrated water reflux valve, a second section concentrated water reflux valve, a water outlet valve, a second section water inlet branch valve and a concentrated water outlet valve.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or coupled. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
For the convenience of understanding the embodiments of the present invention, the following description will be further explained by taking several specific embodiments as examples in conjunction with the drawings, and the embodiments are not to be construed as limiting the embodiments of the present invention.
Example 1
In this embodiment, a first stage and a second stage of nanofiltration are taken as an example, in the operation process of the nanofiltration membrane, the nanofiltration membrane is automatically washed by an electric control program, the nanofiltration unit is shut down and does not produce water during washing, the first stage and the second stage are respectively washed, fig. 1 is a schematic diagram of an automatic control washing flow of this embodiment, and referring to fig. 1, the specific embodiment is as follows:
and (3) washing for a first stage: closing the unit to stop water production, closing a section of concentrated water valve, a section of concentrated water reflux valve, a section of concentrated water branch valve, opening a concentrated water discharge valve, opening a water inlet valve and a water pump, and enabling the water inlet to be 8-16m3Flushing the nanofiltration membrane for 150s at the flow rate of/h, and closing a valve (b) of a concentrated water outlet valve.
And (4) a second flushing stage: closing the water inlet valve and the second-stage concentrated water reflux valve, opening the second-stage concentrated water bypass valve, the first-stage concentrated water valve, the second-stage concentrated water valve and the water pump, and allowing the water inlet to reach 8-16m3Flushing the nanofiltration membrane for 150s at a flow rate of/h, and switching all valves to positiveAnd (4) a normal running state. The electric control program sets that the washing is carried out once every 6h, and the washing liquid after washing flows back to the front end to be fed or is directly discharged.
The method can reduce the accumulation of pollutants and reduce the pollution rate of the nanofiltration membrane. FIG. 2 is a comparison graph of the membrane specific flux results of the nanofiltration membrane washed every day with the same amount of water for washing every day and at different time intervals under the premise of not affecting the recovery rate, and it can be seen from FIG. 2 that the membrane specific flux decay rate of the nanofiltration membrane is 1.55LMH/MPa d when the nanofiltration membrane is washed once every 12h and every 300 s. The membrane specific flux decay rate of the nanofiltration membrane is 1.95 LMH/MPa.d when the nanofiltration membrane is washed once every 10h and every 252 s. The membrane specific flux decay rate of the nanofiltration membrane is 0.63 LMH/MPa.d when the nanofiltration membrane is washed once every 6h and 150s every time. I.e., the shorter the time interval, the slower the membrane specific flux drops, thus reducing the number of chemical washes. The operation conditions are as follows: flux 20LMH, recovery 75%.
Example 2
The embodiment provides a method for cleaning a nanofiltration membrane, wherein the severity of membrane pollution is judged according to the amount of membrane specific flux attenuation, the membrane specific flux attenuation is 27.7% in the embodiment, and the judgment shows that the membrane specific flux attenuation is less than or equal to 30%, so that a cleaning scheme is selected, namely the membrane specific flux can be recovered to the initial value only by using alkaline cleaning. The specific operating conditions were as follows:
1) alkali washing:
preparing EDTA-4Na with the mass fraction of 0.3% in an alkaline washing tank, adding NaOH to adjust the pH value to 11.5, feeding the adjusted cleaning solution into a nanofiltration membrane through a cleaning pump, and controlling the flow velocity of the cleaning solution to be 6m3And/h, the temperature of the cleaning solution is 27-29 ℃, and the cleaning solution is cleaned for 15min and soaked for 0.5h alternately, wherein the total cleaning time is 4 h.
2) Acid washing: hydrochloric acid is added into a pickling tank to adjust the pH value to be 2, the adjusted cleaning solution enters a nanofiltration membrane through a cleaning pump, and the flow velocity of the cleaning solution is controlled to be 6m3And/h, alternately cleaning for 15min and soaking for 0.5h, wherein the total cleaning time is 2h, and the cleaning solution temperature is 27-29 ℃.
3) Washing with pure water:
alkali washingThen pure water is adopted to enter the nanofiltration membrane through a cleaning pump until the pH value of the outlet water is recovered to be neutral, and the flow velocity of the pure water is controlled to be 6m3The temperature of the pure water is 27-29 ℃.
4) And after the cleaning is finished, closing the cleaning pump and the cleaning system, and opening the nanofiltration unit to normally produce water.
Fig. 3 is a comparison graph of the membrane specific flux results after the alkali washing and the acid washing by the method of this example, and it can be seen from fig. 3 that the membrane specific flux is restored to 102.1% after the alkali washing (the membrane specific flux is greater than 100% due to the flux increase caused by the swelling of the membrane pores), and then the acid washing membrane specific flux is restored to 98.7%.
By adopting the acid washing step of the embodiment, the swelling and shrinking of the membrane pores can be obviously improved, and the problem of TMP sudden increase after cleaning in the prior art is solved.
Example 3
The embodiment provides a method for cleaning a nanofiltration membrane, which judges the severity of membrane pollution according to the amount of membrane specific flux attenuation, wherein the membrane specific flux attenuation is 43.5% in the embodiment, and the judgment shows that the flux attenuation of the nanofiltration membrane is greater than 30%, so the following steps are adopted:
1) alkali washing:
EDTA-4Na with the mass fraction of 0.5% is prepared in the alkaline washing tank, NaOH is added to adjust the pH value to be 11.5, the adjusted cleaning liquid enters the nanofiltration membrane through the cleaning pump, and the flow velocity of the cleaning liquid is controlled to be 8m3The temperature of the cleaning liquid and the pure water is 27-29 ℃, cleaning is carried out for 15min and soaking is carried out for 0.5h alternately, and the total cleaning time is 4 h;
2) acid washing:
after alkaline washing, hydrochloric acid is added into a pickling tank to adjust the pH value to 2.5, the adjusted cleaning solution enters a nanofiltration membrane through a cleaning pump, and the flow rate of the cleaning solution is controlled to be 8m3And h, the temperature of the cleaning liquid and the pure water is 27-29 ℃, cleaning is carried out for 15min and soaking is carried out for 0.5h alternately, and the total cleaning time is 2 h.
3) Washing with pure water:
after acid washing, pure water enters the nanofiltration membrane through a cleaning pump until the pH value of the effluent is recovered to be neutral.
4) And after the cleaning is finished, closing the cleaning pump and the cleaning system, and opening the nanofiltration unit to normally produce water.
Fig. 4 is a comparison graph of the specific flux results of the membrane after acid washing by using the method of the present embodiment, and it can be seen from fig. 4 that when the flux attenuation is greater than 30%, the specific flux of the membrane after alkali washing by using the method of example 2 is recovered to 104.9%, and the specific flux of the membrane after acid washing is recovered to 96.6%.
Example 4
Fig. 5 is a comparison graph of the membrane specific flux results obtained by two cleaning processes using the method of flux attenuation < 30% of example 1 when the membrane specific flux is attenuated by 45.4%, and it can be seen from fig. 5 that when the flux is attenuated by > 30%, the membrane specific flux is restored to 88.7% after the first alkali cleaning is performed using the method of flux attenuation < 30%, and then the acid-cleaned membrane specific flux is restored to 89.1%, and the flux cannot be completely restored. The specific flux of the second alkali washing membrane is recovered to 106.9% by continuously using a method with the flux attenuation of less than 30%, and then the specific flux of the acid washing membrane can be recovered to 95.3%. Although multiple cycles of alkaline and acid washing eventually lead to complete recovery of the membrane specific flux, enormous labor and reagent costs are undoubtedly incurred.
However, the flux can be recovered by the method of the present embodiment with the flux attenuation of more than 30%, so that it is necessary and effective to select different cleaning methods according to the flux attenuation degree of the nanofiltration membrane.
The method of the present embodiment is also applicable to the case of one, three or more stages.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for apparatus or system embodiments, since they are substantially similar to method embodiments, they are described in relative terms, as long as they are described in partial descriptions of method embodiments. The above-described embodiments of the apparatus and system are merely illustrative, and the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (5)

1. The method for cleaning the nanofiltration membrane is characterized by comprising the following steps of:
cleaning in steps according to the flux attenuation value of the nanofiltration membrane:
s1 when flux attenuation of the nanofiltration membrane is less than or equal to 30%, the following steps are adopted:
s11 alkaline washing:
preparing EDTA-4Na with the mass fraction of 0.1-1% in an alkaline washing tank, adding NaOH to adjust the pH value to 11-12, introducing the adjusted cleaning liquid into a nanofiltration membrane through a cleaning pump, and alternately cleaning for 15min and soaking for 0.5h, wherein the total cleaning time is 1-4 h;
s12 acid washing:
after alkaline washing, adding acid into a pickling tank to adjust the pH value to 2-3, feeding the adjusted cleaning solution into a nanofiltration membrane through a cleaning pump, and controlling the flow velocity of the cleaning solution to be 6-8m3Cleaning for 15min and soaking for 0.5h alternately, wherein the total cleaning time is 1-4h, and the temperature of the cleaning liquid is 20-40 ℃;
s13 rinsing with pure water:
after alkaline washing, pure water enters a nanofiltration membrane through a washing pump until the pH value of the effluent is recovered to be neutral;
s2 when flux attenuation of the nanofiltration membrane is more than 30%, the following steps are adopted:
s21 alkaline washing:
EDTA-4Na with the mass fraction of 0.3% -1% is prepared in an alkaline washing tank, NaOH is added to adjust the pH value to 11-12, the adjusted cleaning liquid enters a nanofiltration membrane through a cleaning pump, cleaning is carried out for 15min and soaking is carried out for 0.5h alternately, and the total cleaning time is 2-6 h;
s22 acid washing:
after alkali washing, adding acid into a pickling tank to adjust the pH value to 2-3, feeding the adjusted cleaning solution into a nanofiltration membrane through a cleaning pump, and alternately cleaning for 15min and soaking for 0.5h, wherein the total cleaning time is 1-4 h;
s23 rinsing with pure water:
after acid washing, pure water enters the nanofiltration membrane through a cleaning pump until the pH value of the effluent is recovered to be neutral.
2. The method as claimed in claim 1, wherein the flow rate of the cleaning liquid and the water is controlled to 6 to 8m3The temperature of the cleaning liquid and the pure water is 20-40 ℃.
3. The method of claim 1, further comprising: in the operation process of the nanofiltration membrane, pure water is used for 8-16m every 4-12 h3Flushing the nanofiltration membrane for 100 s-5 min at a flow rate of/h, and refluxing the flushed liquid to the front end for water inlet or directly discharging.
4. The method as claimed in claim 1, wherein the pure water is used for 8-16m every 6h during the operation of the nanofiltration membrane3The nanofiltration membrane is washed for 150s at the flow rate of/h.
5. The method according to claim 1, wherein the mass fraction of EDTA-4Na in S11 alkaline washing is 0.3%, and the mass fraction of EDTA-4Na in S21 alkaline washing is 0.5%.
CN202110376380.9A 2021-04-06 2021-04-06 Method for cleaning nanofiltration membrane Active CN112933993B (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU2009202672A1 (en) * 2009-07-01 2011-01-20 Desaln8 Pty Ltd Apparatus and method for improving the quality of water from an aquifer
CN103657425A (en) * 2013-11-29 2014-03-26 北京碧水源膜科技有限公司 Method for recycling waste polyamide roll type reverse-osmosis membrane elements
CN109126472A (en) * 2018-08-21 2019-01-04 清华大学 A kind of cleaning agent and cleaning method of Treating Municipal Sewage secondary effluent nanofiltration membrane
CN109224869A (en) * 2018-11-19 2019-01-18 湖南军信环保股份有限公司 A kind of cleaning method of NF film, RO film
CN109224870A (en) * 2018-11-19 2019-01-18 湖南军信环保股份有限公司 A kind of nanofiltration, reverse osmosis membrane chemical cleaning method

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU2009202672A1 (en) * 2009-07-01 2011-01-20 Desaln8 Pty Ltd Apparatus and method for improving the quality of water from an aquifer
CN103657425A (en) * 2013-11-29 2014-03-26 北京碧水源膜科技有限公司 Method for recycling waste polyamide roll type reverse-osmosis membrane elements
CN109126472A (en) * 2018-08-21 2019-01-04 清华大学 A kind of cleaning agent and cleaning method of Treating Municipal Sewage secondary effluent nanofiltration membrane
CN109224869A (en) * 2018-11-19 2019-01-18 湖南军信环保股份有限公司 A kind of cleaning method of NF film, RO film
CN109224870A (en) * 2018-11-19 2019-01-18 湖南军信环保股份有限公司 A kind of nanofiltration, reverse osmosis membrane chemical cleaning method

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