JP2001314875A - Method for treating chemical washing waste liquid of separation membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating a chemical washing waste liquid by separating the chemical washing waste liquid of a separation membrane using an organic acid into clear treated water easily dischargeable to sewerage or the like and a small amount of residue. SOLUTION: A compound containing a metal component forming a substantially insoluble or hardly soluble organic acid salt and soluble in an organic acid aqueous solution is added to the chemical washing waste liquid using the organic acid to precipitate the organic acid component before the waste liquid is separated into clear treated water and residue.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for treating a chemical cleaning waste liquid from a separation membrane. The method for treating a chemical cleaning waste liquid of a separation membrane according to the present invention can significantly reduce the volume of a chemical cleaning waste liquid generated when the separation membrane is chemically cleaned with an organic acid.

[0002]

2. Description of the Related Art In recent years, the development of a separation technique using a filtration membrane has been advanced, and it is widely used for various uses such as filtration of water. However, in the process of membrane filtration, solids such as suspended substances in a stock solution called SS attach to the membrane surface and / or penetrate into microporous, and the permeation flux decreases with time.
Therefore, in order to stably continue the filtration operation for a long period of time, it is indispensable to set a filtering condition and to develop an effective method for cleaning the separation membrane.

Conventionally, various methods have been studied as a method for cleaning a separation membrane. These methods can be roughly classified into a physical cleaning method and a chemical cleaning method. Physical cleaning methods include a method of forcibly removing adhered substances with a sponge ball or a high-pressure water stream, a liquid backwashing method in which liquid such as water or a permeate is passed from the filtrate side to the undiluted liquid side, and a pressurized gas being filtrated. Backwashing method of passing gas from the side to the stock solution side, pressurizing operation to introduce gas from the filtrate side with a pressure lower than the pressure at which gas is released from the stock solution side of the hollow fiber membrane, bubbling method of blowing bubbles to the stock solution side A variety of methods have been proposed, including an ultrasonic method, an electrophoresis method, and the like. Further, as a chemical cleaning (hereinafter referred to as chemical cleaning) method, a method of dissolving and removing adhered substances by a chemical solution such as an oxidizing agent such as an aqueous acid solution, an aqueous alkali solution, or an aqueous sodium hypochlorite solution, or a cleaning agent is known. Are known.

In general, when a substance that adheres to a filtration membrane and causes a decrease in permeation flux (hereinafter referred to as a fouling substance) is mainly composed of an inorganic substance such as an oxide such as iron or manganese or a hydroxide, Acids such as hydrochloric acid, oxalic acid, and citric acid are known to be effective as chemical cleaning chemicals, and it is known that organic acids such as oxalic acid and citric acid have a particularly high cleaning effect. Therefore, from the viewpoint of the cleaning effect, an organic acid is often preferable as a chemical cleaning chemical solution rather than hydrochloric acid, but there is a problem of treatment of a chemical cleaning waste liquid as described below.

[0005] When the separation membrane is chemically washed with acids, the used chemical solution (hereinafter referred to as "chemical washing waste liquid") generally has an acidic pH, and the fouling substance is dissolved or suspended in a solid state. For this reason, it may not be possible to release the water directly into the sewer or river. For example, according to the Tokyo Metropolitan Government's sewage elimination standards as of July 1, 1998, if a manufacturer or gas supplier that does not have a specific facility emits more than 50 m3 / day, discharge to sewage is permitted. The waste water has a pH of more than 5.7 and less than 8.7, dissolved iron of less than 10 mg / L (liter), suspended solids (hereinafter referred to as SS) of less than 300 mg / L, and biochemical oxygen demand ( (Hereinafter referred to as BOD) is specified as less than 300 mg / L. Therefore, when disposing of the chemical cleaning waste liquid, it is necessary to take necessary measures such as neutralization and then discharge it, or to dispose it as industrial waste, while taking into account the above regulatory values.

[0006]

SUMMARY OF THE INVENTION The present inventors have conducted tests from the viewpoint of the processability of chemical cleaning waste liquid with acids for fouling containing iron as a main component. As a result, the chemical cleaning waste liquid with hydrochloric acid precipitates a large amount of iron dissolved by the neutralization treatment, and is purified to a level capable of discharging sewage by removing it by a method such as filtration. Chemical washing waste liquid with organic acids such as citric acid
It has been found that since the OD is extremely high and the dissolved iron is not easily precipitated even when the neutralization treatment is performed, it is not possible to easily purify the iron to a level at which the sewage can be discharged.

[0007] Therefore, the washing waste liquid with an organic acid requires a final treatment such as biological treatment, incineration treatment, dilution discharge or industrial waste treatment. However, biological treatment requires a relatively large installation space, and also requires dilution. In effluent, the total load of wastewater is not reduced at all and dilution water is required,
On the other hand, industrial waste treatment requires disposal costs. Furthermore, the diluting discharge and the industrial waste treatment are all against the recent trend of environmental protection and waste reduction, and are in a state of containing very serious problems.

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel method for treating chemical washing waste liquid from a separation membrane, which can separate the chemical washing waste liquid by an organic acid into clear water that can be easily discharged and a small amount of residue. .

[0009]

According to the present invention, there is provided a method for treating a chemical washing waste liquid of a separation membrane, comprising the steps of: providing an organic acid substantially insoluble or hardly soluble in a chemical washing waste liquid using an organic acid aqueous solution; A compound containing a metal component that forms a salt and soluble in an organic acid aqueous solution is added to precipitate an organic acid component, and then separated into clear treated water and a small amount of residue.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The separation membrane to be used in the present invention includes a microfiltration membrane, an ultrafiltration membrane, a reverse osmosis membrane and the like. The material of the separation membrane is not particularly limited, and is a polysulfone-based resin hydrophilized with a polyvinyl alcohol-based resin, a polysulfone-based resin to which a hydrophilic polymer is added, a polyvinyl alcohol-based resin, and a polyacrylonitrile-based resin. , Cellulose acetate resin, hydrophilized polyethylene resin, polyolefin, polysulfone, polyethersulfone, ethylene-vinyl alcohol copolymer, polyvinylidene fluoride,
Use conditions include separation membranes composed of organic polymer materials such as polyperfluoroethylene, polymethacrylate, polyester, and polyamide, and separation membranes composed of inorganic materials such as ceramics. Can be selected according to the desired filtration performance and the like.

Here, a separation membrane made of a polysulfone resin hydrophilized with a polyvinyl alcohol resin, a polysulfone resin added with a hydrophilic polymer or a polyvinyl alcohol resin not only has excellent hydrophilicity, It is particularly preferable because it has excellent heat resistance and chemical resistance. When using organic polymer materials, 30 mol%
Copolymerized with other components in the following amount, or 30% by weight
It may be a blend of other materials in an amount within the range. Further, examples of the structure of the separation membrane include a flat membrane, a hollow fiber membrane, a tubular membrane, and a spiral membrane, but are not particularly limited. The above-mentioned separation membrane is a “membrane module” that is bundled and adhered to a housing, or fixed in a cylindrical container while being wound together with a support for the purpose of supplementing mechanical strength and improving usability. May be used as When the separation membrane and the separation membrane module have excellent heat resistance and chemical resistance, it is possible to use a high-concentration organic acid aqueous solution by heating it during chemical cleaning, and the cleaning effect is increased. In some cases, the washing time can be shortened, which is preferable.

In the present invention, the above-mentioned separation membrane module is chemically washed with an organic acid aqueous solution. The concentration of the organic acid aqueous solution is set depending on the chemical resistance of the separation membrane, the amount of the fouling substance, and the like, and is generally used in a concentration within the range of 0.1 to 5% by weight. Chemical cleaning with organic acid aqueous solution
In general, a sufficient cleaning effect can be obtained at room temperature. However, if the separation membrane module is excellent in heat resistance and chemical resistance as described above, if the separation membrane module is heated to about 60 ° C. for chemical cleaning, for example, In some cases, the effect is increased or the cleaning time can be shortened.

As a method for chemical cleaning, an organic acid aqueous solution is introduced into the undiluted solution side of the separation membrane module, left standing (immersed) for a predetermined time, and then washed with water. The organic acid aqueous solution is circulated to the undiluted solution and, if necessary, simultaneously filtered. After that, there is a method of washing with water, and a method of combining these with a physical washing operation, and the like.
Although it can be selected according to the characteristics of the chemical cleaning device, it is preferable to perform the cleaning in combination with the circulation in terms of the cleaning effect.

In the present invention, the organic acid component is added by adding a compound soluble in an organic acid aqueous solution and containing a metal component which generates an organic acid salt substantially insoluble or hardly soluble in the waste liquid after the above-mentioned chemical washing. And then separated into clear treated water and residue. At this time, water used for water washing may be added to the chemical washing waste liquid to carry out batch treatment. The term “substantially insoluble or hardly soluble” as used herein means that the BOD derived from the dissolved organic acid component is sufficiently low after the precipitation treatment described in detail below, and that the neutralized This refers to a state in which the amount of the organic acid component is sufficiently reduced to such a degree that almost all of the ring component is precipitated. Therefore, the solubility of the generated organic acid salt is preferably 1 g or less, more preferably 0.1 g or less, per 100 g of water at normal temperature.

From this viewpoint, it is necessary that the compound used in the present invention is a water-soluble compound containing a metal component which reacts with an organic acid ion to form a substantially insoluble and hardly soluble organic acid salt. Yes, for example, when treating oxalic acid washing waste liquid, magnesium, calcium, compounds containing alkaline earth metal components such as strontium and barium, scandium, yttrium, cerium, cobalt, copper, zinc, cadmium, mercury, thallium, Examples include compounds containing lead and bismuth.
As the compound to be added, an inorganic salt is preferable from the viewpoint of the BOD of the waste liquid, and it is preferable that the compound is easily available, inexpensive, and has no toxicity or danger. From this viewpoint, for example, when treating oxalic acid washing waste liquid, preferred compounds include magnesium chloride, magnesium carbonate, magnesium hydroxide, calcium chloride, calcium carbonate, calcium hydroxide and the like. Further, when a calcium compound is used, a small amount of the residue obtained in the step described below can be oxidized to solidify the cement, which is particularly preferable.

The amount of the water-soluble compound containing a metal component is
The valency of the metal component, which is appropriately set depending on the reactivity with the organic acid component, for example, when treating oxalic acid washing waste liquid, when using a metal component acting as a divalent component such as magnesium or calcium, It is preferable that the amount is within a range of 1.0 to 1.5 mol times of oxalic acid used for chemical cleaning. On the other hand, when a metal component acting as a trivalent component such as scandium is used, it is preferably in the range of 0.67 to 1.0 mol times the oxalic acid used for chemical cleaning. If the added amount is small, the final treated water B
The OD value may not be sufficiently reduced.

After adding the water-soluble compound containing the metal component described above, in order to sufficiently promote the precipitation reaction of the organic acid component,
It is preferred to stir. The required stirring time varies depending on the concentration of the organic acid, the metal compound to be added, the treatment scale, the stirring method and the stirring efficiency.For example, when treating oxalic acid washing waste liquid using calcium chloride as the metal compound, the reaction time is reduced. Is almost complete within about 15 minutes.

The pH of the waste liquid at the end of the above reaction is:
It depends on the concentration of organic acid aqueous solution used for chemical cleaning, the type and amount of fouling, and the type and amount of metal compound to be added, but if the pH deviates from the discharge standard for sewerage, etc. Performs sum processing. The chemical used is not particularly limited, but is preferably an inorganic component.Examples of the alkali component include sodium hydroxide and potassium hydroxide.On the other hand, examples of the acid component include hydrochloric acid and sulfuric acid. No.

By the operations described so far, the BOD
The organic acid component to be loaded is almost completely precipitated, and subsequently, a clear water component that can be discharged to a sewer and the like is separated into a small amount of residue.

Examples of the separation method include various filtration using a hollow fiber membrane cartridge filter, a paper filter, and diatomaceous earth, coagulation sedimentation, a filter press, pressure flotation, and the like. It can be appropriately selected according to various conditions.

According to the method for treating chemical cleaning waste liquid of the present invention, it is possible to separate the chemical cleaning waste liquid using an organic acid into clear treated water that can be easily discharged into sewage and the like and a small amount of residue. It is used as a heat refrigerant for purification of river water, well water, lake water, etc., recovery of steam drain, district heating and cooling, building air conditioning, etc. It can be applied to an extremely wide range of applications where separation membranes are used, including purification of cold and hot water used.

[0022]

The present invention will be described in more detail with reference to the following examples. From the results of the following examples, it is understood that according to the present invention, it is possible to easily separate clear water that can be discharged to a sewer or the like and a small amount of residue.

Example 1 A hollow fiber membrane element 1 incorporated in a hollow fiber membrane module 2 shown in FIG. 1 was used as a separation membrane to be washed.
In this hollow fiber membrane module 2, a hollow fiber membrane element 1 is housed in a container 3, and is divided into a stock solution side A and a filtrate side B by a hollow fiber membrane convergence unit 4. The hollow fiber membrane element 1
It is made of a polysulfone resin hydrophilized with polyvinyl alcohol, has a nominal pore size of 0.1 μm, and a membrane area of 7 m ² . The hollow fiber membrane module 2
Is provided with a stock solution supply port 5, a filtrate solution outlet 6, a gas discharge port 7, and a stock solution discharge port 8. When the external pressure total filtration method is used, the gas discharge port 7 and the stock solution discharge port 8 are closed. A stock solution to be filtered is supplied from a stock solution supply port 5, and the filtrate filtered by the hollow fiber membrane element 1 is extracted from a filtrate outlet 6.

It contains about 1 mg / L of iron and has a temperature of about 50 mg / L.
The hollow fiber membrane element 1 which has been used for about 6 months for filtration of hot water for air conditioning at a temperature of about 20 ° C. and whose water permeability has been reduced to about 20% of the initial value is added to 12 L of a 2% by weight oxalic acid aqueous solution at room temperature.
After soaking for an hour and then washing with water, the water permeability was 9
He had recovered to 2%. The pH of the aqueous oxalic acid solution (hereinafter referred to as “chemical cleaning waste liquid”) after the chemical cleaning was 1.9. To the chemical washing waste liquid, calcium chloride was added in an amount of 1.2 mol times the amount of oxalic acid used, and the mixture was stirred for 15 minutes, and then neutralized by adding sodium hydroxide to pH 7. Next, 100 mg / L of an acrylamide polymer flocculant was used.
After adding and stirring for 5 minutes to form a floc, the solution was passed through a paper filter having a nominal pore size of 30 µ to perform solid-liquid separation. Table 1 shows the results of the water quality analysis of the treated water.

[0025]

[Table 1]

Example 2 Treated water was obtained in the same manner as in Example 1 except that the waste liquid after neutralization with sodium hydroxide was filtered with a pleated cartridge filter having a nominal pore size of 3 μm. Table 1 shows the results of the water quality analysis of the treated water.

Example 3 To the same chemical washing waste liquid as in Example 1, 1.5 mol times calcium hydroxide was added instead of 1.2 mol times calcium chloride used oxalic acid, and the mixture was stirred for 15 minutes. Then, hydrochloric acid was added to neutralize the solution to pH 7. Next, solid-liquid separation was performed through a filter precoated with diatomaceous earth. Table 1 shows the results of the water quality analysis of the treated water.

COMPARATIVE EXAMPLE In Example 1, the pH was adjusted to 7 by neutralizing the chemical washing waste liquid with sodium hydroxide. Table 1 shows the results of water quality analysis of the obtained waste liquid.

[0029]

According to the method for treating chemical cleaning waste liquid of the separation membrane of the present invention, it is possible to easily treat chemical cleaning waste liquid using an organic acid, thereby greatly reducing the labor and cost of chemical cleaning wastewater treatment. be able to.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view showing a state in which a hollow fiber membrane element to which a method for treating chemical cleaning waste liquid of a separation membrane according to one embodiment of the present invention is applied is incorporated in a hollow fiber membrane module.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Separation membrane (hollow fiber membrane element), 2 ... Hollow fiber membrane module, 3 ... Container, 4 ... Hollow fiber membrane condensing part, 5 ... Undiluted solution supply port, 6 ... Filtrate outlet, 7 ... Gas outlet, 8 ... Undiluted solution Vent,
A: undiluted solution, B: filtrate side.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shinichi Ito 1-11-1 Hitsuji, Adachi-ku, Tokyo Stock inside Tokyo Electric Works (72) Inventor Hironobu Murakami 1-1-1 Hitsutaya, Adachi-ku, Tokyo Stock (72) Inventor Tsutomu Miura 1621 Sazu, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd. (72) Inventor Yuko Hayashi 1621 Sakurazu, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd. (72) Inventor Naoyuki Kato 3-8-2, Nihombashi, Chuo-ku, Tokyo Kuraray Co., Ltd. (72) Inventor Shinji Komori 3-82-2, Nihonbashi, Chuo-ku, Tokyo F-term in Kuraray Co., Ltd. 4D006 GA03 GA06 GA07 HA03 HA19 KC02 KC16 KD14 KD15 KD16 KE11Q KE16Q MA01 MA02 MA03 MA22 MB09 MB11 MB15 MC03 MC18 MC22 MC28 MC29 MC33 MC34 MC37 MC39 MC48 MC54 MC62 MC63 PA01 PB04 P B22 PB27 4D038 AA08 AB10 AB66 AB90 BA04 BA06 BB13 BB17 BB18

Claims (3)

[Claims] 1. A method for treating a chemical washing waste liquid generated when a separation membrane is chemically washed with an organic acid aqueous solution, wherein the metal component produces a substantially insoluble or hardly soluble organic acid salt in the chemical washing waste liquid. A method for treating a chemical cleaning waste liquid of a separation membrane, wherein a compound soluble in an organic acid aqueous solution is added to precipitate an organic acid component, and then separated into clear treated water and residue. 2. The method according to claim 1, wherein the organic acid aqueous solution is an oxalic acid aqueous solution. 3. The separation according to claim 2, wherein the compound containing a metal component that forms a substantially insoluble or hardly soluble oxalate and soluble in the oxalic acid aqueous solution mainly comprises at least one of a magnesium compound and a calcium compound. Treatment method for chemical cleaning waste liquid of membrane.