JP2005103510A - Method for cleaning liquid chemical - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method by which the amount of the waste cleaning liquid chemical to be discharged can remarkably be reduced to bring about an economical effect and the amount of the waste cleaning liquid chemical to be stored can also remarkably be reduced. <P>SOLUTION: The usage of a liquid chemical is remarkably reduced by purifying the spent liquid chemical by using a membrane module and using the purified liquid chemical repeatedly for the purpose of cleaning another membrane module. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for cleaning a membrane. More particularly, the present invention relates to an economical and effective method for cleaning a film.

  Membranes that separate components in liquids and remove SS have been used in various applications because they save energy. For example, industrial wastewater treatment, river water and groundwater turbidity, seawater desalination, bioreactors, etc. are examples. Various types of membranes have been used depending on the application. For example, river water is filtered through a microfiltration membrane, an ultrafiltration membrane, or a reverse osmosis membrane and used as drinking water. In the drainage, the activated sludge water is separated into activated sludge solids and filtered water by a microfiltration membrane or dynamic filtration.

  However, such filtration may cause SS and adsorbate to adhere to the filtration surface and reduce the filtration capacity, and a necessary amount of filtered water may not be obtained. For this reason, by regularly or non-periodically cleaning the filtration surface, the SS component attached to the filtration surface is removed to maintain the filtration capability. For example, in Japanese Patent Laid-Open No. 8-141375, filtration performance is maintained by reversely permeating filtered water from the filtration side periodically. Japanese Patent Application Laid-Open No. 2001-38177 proposes performing filtration while cleaning the filtration surface by supplying air from below the filter body. Furthermore, Japanese Patent Application Laid-Open No. 2002-126470 also proposes a method of chemically cleaning the filter body because the filter surface cannot be cleaned by such a method.

Japanese Patent Application Laid-Open No. 61-0708403 discloses a method of washing an ultrafiltration membrane or a microfiltration membrane in n stages using a chemical in multiple stages, and the membrane permeate in the first stage washing is a chemical washing. A cleaning method is disclosed in which the membrane permeation liquid in the second and subsequent stages of cleaning is returned to the chemical tank without passing through the chemical cleaning apparatus, and the chemical returned to the chemical layer is used for the next cleaning. Yes. Japanese Laid-Open Patent Publication No. 5-96291 discloses that membrane separation is performed with a membrane module without throwing away backwash drainage when the sand filtration layer is backwashed, and this membrane separation water is reused in the system. . Japanese Patent Application Laid-Open No. 11-207344 discloses a method of treating backwash drainage of a sand filtration device with a spiral type module having a specific configuration. Furthermore, Japanese Patent Laid-Open No. 2001-87764 discloses that washing wastewater from a sand filtration pond in a water purification treatment facility is filtered with a membrane filtration device, and the membrane filtration water is recycled as washing water.
Japanese Patent Laid-Open No. 61-0708403 JP-A-5-096291 Japanese Patent Laid-Open No. 11-207344 JP 2001-087764 A

  In such chemical cleaning, the chemical used for cleaning must be treated as chemical chemical waste water. This chemical chemical wastewater is usually discarded after neutralization or detoxification treatment by activated sludge treatment. For this reason, it was expensive and expensive to process. In addition, when a large amount of membrane is washed, a large amount of chemical chemical wastewater is discharged, so that it is necessary to secure a facility for temporary storage for processing, which is expensive. Moreover, in the said patent document 1, although the backwash water used for the washing | cleaning of a film | membrane is processed and reused by another membrane module, a several chemical | medical solution tank is required, and separation of a film | membrane is carried out. The hole diameter is not considered.

  The present invention proposes a method for effectively using the chemical chemical waste water from which the membrane has been washed. The present inventor has found that the chemical agent that has washed the membrane can be applied to membrane washing a plurality of times by treating the membrane with the membrane, and has completed the present invention.

  The invention of claim 1 is characterized in that after the membrane module is washed with a chemical solution, the chemical solution is filtered with a membrane module for chemical solution purification and used again as a chemical solution for membrane module cleaning. This is a chemical cleaning method.

  The invention of claim 2 is a chemical cleaning method characterized in that the chemical purification membrane module has a separation hole diameter substantially equal to or smaller than the separation hole diameter of the membrane module to be cleaned. The invention according to claim 3 is the chemical cleaning method characterized in that at least 30% by weight of the chemical used initially cleans the membrane module three times or more. According to a fourth aspect of the present invention, the chemical liquid cleaning method is characterized in that the chemical liquid is an aqueous solution of an organic acid, an inorganic acid, or a surfactant, or a mixture thereof. The invention according to claim 5 is the chemical solution cleaning method characterized in that the membrane module for chemical solution purification is an external pressure filtration membrane module and can remove turbid components adhering to it by reverse cleaning.

  There are no particular restrictions on the materials used for the chemical purification membrane and the membrane to be used in the present invention. For example, plastics such as polysulfone resin, nylon resin, polyethylene terephthalate resin, fluorine resin, PVA, and cellulose derivative resin may be used, or ceramic may be used. Metals or composite resins may be used.

  Also, the pore diameter of the membrane is not limited, but it is preferably substantially the same as or finer than the pore diameter of the membrane to be cleaned. The chemical solution after membrane cleaning usually contains a large amount of SS. When this chemical solution is washed with a membrane having a pore diameter substantially equal to or smaller than the pore size of the membrane module to be washed next, SS adheres to the membrane to be washed next, and the same effect as when washing with a new chemical solution can be maintained.

  Further, the form of the membrane module to be used is not particularly limited with respect to the membrane module for chemical solution purification and the membrane module to be cleaned. Examples thereof include a hollow fiber membrane module, a spiral membrane module, a flat membrane membrane module, and a tube membrane module.

  Any method of using the membrane module for chemical solution purification can be used, but after chemical solution purification, a large amount of SS in the chemical solution adheres to the membrane, so the attached SS can be easily removed by applying backwashing. Is preferred. In particular, cellulose derivatives are preferable for this application because the material is highly hydrophilic and the SS content in the chemical solution is easily peeled off from the film. Furthermore, the membrane module of the type which filters with external pressure is preferable. This is because the external pressure is less likely to cause clogging even if a large amount of SS is supplemented.

  The chemical liquid used in the present invention is not particularly limited. For example, inorganic acid aqueous solutions such as hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, organic acid aqueous solutions such as citric acid and oxalic acid, oxidizing agents such as hypochlorite aqueous solution, hydrogen peroxide solution and bisulfite And reducing agents, detergents and surfactant aqueous solutions. In particular, in the present invention, an aqueous solution of an inorganic acid, an organic acid, or a surfactant or a mixture thereof is preferable. This is because these liquids have relatively good chemical stability and can be used for multiple membrane cleanings.

  The concentration of the chemical solution to be used may be any concentration as long as the membrane can be washed, but the concentration of the chemical solution to be adjusted at the initial stage for use multiple times is preferably higher than the minimum effective chemical concentration. Preferably, it is 1.5 times to 10 times, preferably 2 times to 5 times the minimum concentration at which it is recovered to 90% or more of the initial film performance by one chemical cleaning. If the concentration is above the lower limit of this range, the effectiveness of the chemical solution consumed by multiple chemical cleanings and the concentration that can be used multiple times even if there is dilution with water that is brought in when rinsing the membrane with water Can keep. In addition, if the concentration is lower than the upper limit of this range, the deterioration of the film due to the high concentration can be minimized. Moreover, you may adjust to the predetermined | prescribed density | concentration by adding the thing of the density | concentration of the chemical | medical solution for washing | cleaning to be used for a chemical | medical solution. With this method, even if the number of times of cleaning with the chemical solution is increased, the variation in the concentration of the chemical solution can be reduced, which is effective. Various methods, such as general analytical methods such as pH, electrical conductivity, refractive index, UV, TOC, and chromaticity, can be applied to detect the concentration.

  In the present invention, it is preferable that at least 30% by weight of the chemical prepared first is used for cleaning the membrane module, and the membrane module is cleaned three times or more. It is possible to reduce the amount of chemical chemical wastewater.

  The method of the present invention can be applied to any membrane module used for drainage. In particular, it is optimal for applications that filter liquids containing SS. For example, when it is used for filtering river water, groundwater, lake water, or activated sludge or coagulated water, SS is easy to accumulate in the membrane, and chemical cleaning is used to discharge a large amount of SS mixed with the cleaning chemical. This is preferable.

  In addition, any cleaning method can be employed for cleaning the chemical solution. For example, immersion cleaning or flash cleaning may be used. In particular, the present invention is particularly effective when reverse cleaning is used in combination with chemical cleaning. When this method is applied, SS can be removed reliably, so that the membrane permeation side is not contaminated with SS during reverse cleaning.

  The method of the present invention can be carried out as follows. First, a membrane cleaning chemical solution having a predetermined effective concentration is first adjusted in the cleaning chemical solution tank. The module is washed with this chemical solution. In particular, it is effective when performing cleaning using reverse cleaning together. The cleaned chemical solution is stored in the reprocessing stock solution tank, filtered by the chemical solution purification membrane module, and returned to the cleaning chemical solution tank again. The chemical concentration of this solution is measured by various analytical methods, the effectiveness of the concentration is confirmed, and the solution is used again. If the concentration is low, it can be adjusted to a predetermined concentration by adding a high concentration chemical. The membrane module for the chemical solution purification is preferably confirmed by the membrane permeation performance with a device equipped with a pressure gauge or a flow meter. The performance of the membrane module for chemical purification itself can be restored by removing SS.

  In the chemical cleaning method of the present invention, the discharge amount of the cleaning chemical waste water can be greatly reduced, which is economical and effective. In addition, the amount of cleaning chemical wastewater stored can be significantly reduced.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. FIG. 1 is an example of the cleaning method of the present invention.
(Example 1)

  Hollow fiber membrane module FW50RVC-FUC1582 (manufactured by Daisen Membrane Systems Co., Ltd.) equipped with a hollow fiber membrane 50m2 made of cellulose acetate material used for river water filtration for 6 months was used as a chemical cleaning module, and the new same type The module was used as a chemical purification module. As a chemical solution to be used, a solution obtained by dissolving citric acid and a surfactant (Ultrasil 53; manufactured by Ecolab Co., Ltd.) in tap water to 0.5% each was used. First, the chemical solution was reversely permeated at a flow rate of 10 m3 / H for 20 seconds from the permeation side of the chemical solution cleaning module, and then the apparatus was stopped for 2 hours while the chemical solution was filled in the module to perform immersion cleaning. Thereafter, the chemical solution was again permeated under the same conditions to complete the washing. The liquid after washing was stored in a reprocessing stock solution tank. This liquid was filtered with an external pressure of 1 m3 / H into a chemical purification module to purify the chemical, and returned to the cleaning chemical tank. The pH of this drug solution and the suction height of the capillary capillary were measured, the concentration of the drug solution was confirmed, and citric acid and a surfactant were added in order to return to the predetermined concentration. Using this chemical solution, the module used in the same manner as the first chemical solution cleaning module was subjected to chemical solution cleaning in exactly the same manner. The chemicals used were purified in exactly the same way as at the beginning.

With this operation, a total of five chemical cleaning modules were cleaned with chemicals. As a result, the performance of all modules recovered to 90% or more of the membrane permeation flow rate during production. After that, the chemical purification module was backwashed with tap water and recovered to the same performance as before use.
(Comparative Example 1)

The chemical solution cleaning was performed in the same manner as in Example 1 except that the chemical solution purification module was not used. As a result, the performance of the second-cleaning module was 90% or less, and recovery was insufficient.
(Comparative Example 2)

  The chemical solution was washed in the same manner as in Example 1 except that the chemical solution purification module was used as the internal pressure type. As a result, when the chemical solution after the second chemical cleaning was filtered through the chemical purification module, membrane clogging occurred due to SS, making it difficult to purify the chemical solution.

  Table 1 shows the results of evaluation in Example 1 and Comparative Examples 1 and 2.

本発明の薬液洗浄方法では、薬液の繰り返し使用が可能となり、廃棄する薬液を大幅に 削減することが確認された。

In the chemical solution cleaning method of the present invention, it was confirmed that the chemical solution can be used repeatedly, and the chemical solution to be discarded is greatly reduced.

The flowchart of the washing | cleaning method of this invention.

Explanation of symbols

1 Chemical Cleaning Tank 2 Cleaning Membrane Module 3 Reprocessing Stock Solution Tank 4 Chemical Pump 5 Reprocessing Pump 6 Chemical Purification Membrane Module 7 Reverse Cleaning Tap Water

Claims (5)

A method for cleaning a chemical solution, comprising: washing a membrane module with a chemical solution, filtering the chemical solution with a membrane module for chemical solution purification, and performing chemical cleaning again using the chemical solution for cleaning the membrane module. 2. The chemical cleaning method according to claim 1, wherein the chemical purification membrane module has a separation hole diameter substantially equal to or smaller than the separation hole diameter of the membrane module to be cleaned. 3. The chemical solution cleaning method according to claim 1, wherein at least 30% by weight of the chemical solution initially used cleans the membrane module three or more times. The chemical solution cleaning method according to any one of claims 1 to 3, wherein the chemical solution is an aqueous solution of an organic acid, an inorganic acid, or a surfactant, or a mixed solution thereof. The medicinal solution cleaning method according to any one of claims 1 to 4, wherein the medicinal solution refining membrane module is an external pressure filtration membrane module, and can remove turbid components adhering by back washing.

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