JP4943552B2 - Waste water treatment method and waste water treatment system containing surfactant - Google Patents

Description

  The present invention relates to a wastewater treatment method and a wastewater treatment system containing a surfactant.

  In recent years, a system for reusing wastewater has attracted attention in beverage manufacturing factories and the like. The reuse of waste water is preferable not only from the viewpoint of reducing the operating cost of the factory but also from the viewpoint of the environment because the amount of tap water used can be reduced and the amount of waste water can be reduced. Therefore, the necessity of introducing a wastewater recycling system is rapidly increasing among companies consuming a large amount of water. This wastewater reuse system is used in general filling equipment such as soft drinks and aseptic filling equipment, and as wastewater to be collected, rinser wastewater used for washing containers before beverage filling and containers after filling Examples include pastorizer drainage used for cleaning.

For example, in a general filling facility or aseptic filling facility such as a beverage manufacturing plant, the container to be filled with beverage is oxidatively sterilized containing sodium hypochlorite or peroxide (hydrogen peroxide, peracetic acid, etc.). After sterilization with the agent, the container is rinsed with sterile water. For this reason, waste water containing disinfectants such as sodium hypochlorite, hydrogen peroxide, and peracetic acid is continuously discharged from the rinser, and how to treat the disinfectant in this waste water has been a problem from the past. It was.
As a prior art described in the patent literature, for example, there is a processing device that decomposes peracetic acid in supplied wastewater into acetic acid in a peracetic acid decomposition tank (activated carbon tower) and removes the decomposed acetic acid in acetic acid-containing water with a reverse osmosis membrane. (For example, refer to Patent Document 1 and Patent Document 2).

JP 2001-170657 A (page 3-5, FIG. 1) Japanese Patent Laid-Open No. 2002-307081 (page 3, FIG. 1)

  Here, among the beverage manufacturing factories, mainly in the factories that produce soft drinks of PET bottles, a conveyor lubricant is mixed in the sterilized washing water of the containers. The conveyor lubricant is sprayed on the conveyor surface so that the PET bottles smoothly flow through the production line. For example, a surfactant is used. Because plastic bottles are lightweight, they tend to tip over on the production line, especially before filling beverages, and the conveyor line is lubricated to prevent this in view of the fact that if the tipping over, the production line stops and productivity decreases. An agent is used. This conveyor lubricant is used not only for a conveyor line that conveys containers to a rinser, but also for a conveyor line that conveys containers filled with beverages to a path riser.

  However, when the wastewater containing these conveyor lubricants is treated with a reverse osmosis membrane treatment apparatus, the permeation flux may be lowered due to the polarity of the surfactant and the charge on the membrane surface. This is because many anion (anion) systems have been used as conventional conveyor lubricants. In recent years, in addition to the function as a slip agent, cation (cation) In many cases, nonionic (nonionic) surfactants are used, while reverse osmosis membranes are usually anionic charged. Therefore, the cationic surfactant is adsorbed on the membrane surface, causing a decrease in permeation flux. Even when a nonionic surfactant is used for a long period of time, a permeation flux lowering phenomenon due to adsorption of the surfactant on the film surface becomes a problem. The conventional techniques including the above-mentioned patent documents cannot cope with such problems due to the polarity of the surfactant and the charging of the membrane surface.

  The present invention has been made to solve the technical problems as described above, and its object is to provide a cationic or nonionic surfactant with respect to the membrane surface of the reverse osmosis membrane treatment apparatus. This is to suppress a decrease in permeation flux due to adsorption.

Thus, the invention according to the following claims [1] to [4] is provided.
  [1] In the invention according to claim 1, waste water discharged from a beverage manufacturing plant and containing a cationic and / or nonionic surfactant is passed through a catalyst for disinfecting a disinfectant to decompose the disinfectant. A method for treating wastewater containing a surfactant, characterized in that wastewater that has passed through the disinfectant-decomposing catalyst is passed through a cationically charged reverse osmosis membrane.
  [2] The invention according to claim 2 is characterized in that, in the step of decomposing the sterilizing agent, the waste water is once adjusted to near neutral and then passed through the sterilizing agent decomposing catalyst. This is a wastewater treatment method containing the surfactant described in 1.

[3] The invention according to claim 3 is a wastewater treatment system for treating wastewater discharged from a beverage manufacturing factory and containing a cationic and / or nonionic surfactant, which contains the surfactant. A wastewater treatment system comprising a disinfectant decomposer that decomposes the disinfectant from the wastewater and a reverse osmosis membrane treatment device that filters the wastewater from which the disinfectant has been decomposed by the disinfectant decomposer with a cationically charged reverse osmosis membrane.
  [4] The invention according to claim 4 is the waste water treatment system according to claim 4, wherein the waste water is a rinser waste water and / or a pasteurizer waste water used for sterilization and washing of containers.

  According to the present invention, it is difficult for the permeation flux to decrease in the reverse osmosis membrane treatment apparatus, and long-term stable operation of the reverse osmosis membrane treatment apparatus becomes possible.

It is the figure which showed the whole waste-water-treatment system structure to which Embodiment 1 is applied. It is the figure which showed the whole waste-water-treatment system structure in Embodiment 2. FIG.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention. The drawings used are for explaining the present embodiment and do not represent the actual size.

(Embodiment 1)
FIG. 1 is a diagram showing an overall configuration of a wastewater treatment system 100 to which the present embodiment is applied. A wastewater treatment system 100 shown in FIG. 1 is connected to a beverage filling facility 10 composed of a general filling PET line, an aseptic filling PET line or the like, and a facility (system for collecting and reusing wastewater from the beverage filling facility 10. ). The beverage filling facility 10 includes, for example, a rinser (not shown) for sterilizing and washing containers such as bottles and caps filled with beverages, and a pasterizer for cooling and sterilizing products such as beverages filled in containers ( It includes a water treatment process (not shown). In the wastewater treatment system 100, wastewater such as the rinser wastewater that is the wastewater from the rinser and the pasteurizer wastewater that is the wastewater from the path riser is treated and returned to the beverage filling facility 10 to realize reuse of waste water. ing.

  Here, in the beverage filling facility 10, for example, containers such as plastic bottles are conveyed on a production line (conveyor line). At this time, the conveyor lubricant is sprayed onto the conveyor surface so that containers such as PET bottles flow smoothly through the production line. For that reason, in the rinser drainage and pasteurizer drainage, conveyor lubricant is mixed in addition to disinfectant and product components (coffee, tea, fruit juice, syrup, etc.) adhering to the container when the container is filled with the product. ing. Many anionic surfactants have been used as conventional conveyor lubricants. However, in recent years, in order to ensure bactericidal properties and low foaming properties in addition to lubricity, a situation where a cationic (or nonionic) surfactant is used as the conveyor lubricant is increasing, and the wastewater treatment system 100 is increased. The rinser wastewater and pasteurizer wastewater treated in step 1 contain a cationic or nonionic surfactant.

  As a system for treating such rinser wastewater and pastorizer wastewater, a wastewater treatment system 100 to which the present embodiment is applied includes a disinfectant decomposition device 110, a pH adjustment device 120, and a reverse osmosis membrane treatment device 130. I have. This disinfectant disassembling apparatus 110 decomposes disinfectants (sodium hypochlorite, hydrogen peroxide, peracetic acid, etc.) contained in the rinser waste water and the pasterizer waste water. More specifically, the sterilizing agent decomposing apparatus 110 includes a pH adjusting 111 for adjusting drainage to a pH suitable for the sterilizing agent decomposition reaction, and a sterilizing agent decomposing catalyst 112 filled with a catalyst for decomposing the sterilizing agent. Including. In the disinfectant decomposing apparatus 110, first, the pH is adjusted to about neutral (usually about pH 7) with caustic soda or the like at pH adjustment 111. Since acidic decomposition efficiency is poor, it is adjusted to be neutral or alkaline. Then, the bactericide mixed in the wastewater whose pH is adjusted is decomposed by the bactericide decomposition catalyst 112 mainly made of activated carbon. For example, peracetic acid, which is a sterilizing agent, is decomposed into acetic acid by the sterilizing agent decomposing apparatus 110.

  The pH adjusting device 120 of the wastewater treatment system 100 adsorbs a cationic or nonionic surfactant to the reverse osmosis membrane treatment device 130 that delivers this wastewater to the wastewater whose germicide is decomposed by the germicide decomposer 110. PH is adjusted in order to suppress this. The pH is adjusted by measuring the pH of the waste water whose disinfectant has been decomposed by the disinfectant decomposer 110 with a pH measuring device (not shown) and performing feedback control so that the pH becomes 6 or less, for example, with hydrochloric acid or the like. The

  The reverse osmosis membrane treatment device 130 is a membrane treatment device that mainly removes soluble impurities in waste water, and is composed of a reverse osmosis membrane (RO membrane) and an NF membrane (nanofiltration membrane) also called a loose RO membrane. . In the present embodiment, the “reverse osmosis membrane” including the NF membrane will be described. In the reverse osmosis membrane treatment device 130, for example, acetic acid decomposed by the disinfectant decomposition device 110, product components (coffee, tea, fruit juice, syrup, etc.) attached to the container when the product is filled in the container, conveyor lubrication The ingredients of the agent are filtered. These contaminants to be filtered exist as dissolved substances or suspended substances in the rinser drainage and the pasterizer drainage.

  A functional group such as a carboxyl group (COOH) is introduced into the reverse osmosis membrane constituting the reverse osmosis membrane treatment apparatus 130 in order to impart hydrophilicity. This functional group includes anionic, cationic and nonionic types, and one or several of them are introduced. However, since the kind and the blending amount are different for each brand, this causes a difference in charge for each film. Further, when the neutral atmosphere contains many weak acid groups and weak bases having a dissociation degree, the dissociation degree changes with respect to the change in pH in the neutral atmosphere, thereby changing the surface charge.

An anion charged membrane has, for example, only a carboxyl group as a functional group, and the negative chargeability changes depending on the degree of dissociation of the carboxyl group due to pH change. This anion charged membrane containing a carboxyl group is in a dissociated state in a neutral atmosphere, and thus is anion charged. However, at a pH of 4 or less, the dissociation is lost and the charge is neutral. On the other hand, a pH-dependent amphoteric charged membrane is a membrane that can be anionic charged or cationically charged by pH change, and contains, for example, a cationic amino group together with an anionic carboxyl group, Although it is anion charged in the alkaline to neutral range, it changes from anion charged to cation charged in the acidic range.
The cationic charged membrane has, for example, an amino group as a functional group and has a cationic charge property.

  In the present embodiment, the waste water containing the conveyor lubricant is adjusted to pH 6 or less and passed through the downstream reverse osmosis membrane processing apparatus 130. By setting the pH to 6 or less, the anion charge (minus charge) on the membrane surface of the reverse osmosis membrane treatment apparatus 130 can be weakened or changed from neutral to cation charge (plus charge). This makes it possible to minimize adsorption of the cationically charged conveyor lubricant to the membrane surface. The pH value to be adjusted takes different optimum values depending on the film brand and the conveyor lubricant used. That is, it varies depending on the type and amount of functional groups introduced into the film and the components contained in the surfactant. Therefore, it is preferable to test in advance and determine the optimum value.

Here, the degree of dissociation of the carboxyl group will be described.
The degree of dissociation of the carboxyl group (acetic acid) used in the anionically charged reverse osmosis membrane is as follows.

  In Table 1, the percentage (%) of dissociation of carboxyl groups with respect to the pH value of the wastewater is displayed. As shown in Table 1, the rate of dissociation is 99% or more at pH 7 or higher, and there is almost no undissociated portion in this state. On the other hand, the dissociation starts gradually from pH 6.5. In the examples described later, the effect is confirmed at pH 5.8, and it is considered that the effect comes out if there is an undissociated portion even in a minute amount.

Further, the absolute magnitude (strength) of the charge of the membrane is greatly influenced not only by pH but also by the absolute amount of exchange groups introduced. Even if the rate of dissociation due to pH is small, if the amount of exchange groups is large, strong charge is exhibited. In general, the charge of the membrane varies depending on the brand, but it is said in the manufacturer's data and literature that the RO membrane is strong and the NF membrane is weak.
In addition, it becomes easy to adsorb | suck a cation charge substance, so that anion charge is strong. For this reason, since the original charge of the NF film is weak, there is a tendency for the effect to be achieved even when the pH is high. On the other hand, since the RO membrane is highly charged, it is considered necessary to adjust the pH to a low level.
From the degree of dissociation of the carboxyl group, the applicable range of pH is considered to be appropriate at pH 4 or less, preferably 3.5 or less at which almost no dissociation occurs. However, it is preferable to increase the allowable upper limit value from the use conditions and economy of the membrane described later, and the applicable upper limit value is considered to be 6.5 or less at which dissociation starts due to pH, preferably 6 or less at which the degree of dissociation starts to rise. .

Next, conditions for using the film will be described. Although it differs depending on the brand of the reverse osmosis membrane, it is generally as follows.
First, the allowable range of pH is often pH 3 to 9, and it is necessary to keep this range for both supply water and concentrated water. Since ion concentration occurs in the reverse osmosis membrane, the acidity of the treated water becomes stronger when the feed water is acidic. In the present embodiment, the operation of lowering the pH must maintain pH 3 or higher even with concentrated water, and the upper limit value of the supplied water needs to be taken into consideration. Although the difference in pH between the feed water and the treated water varies depending on the concentration ratio, it is generally necessary to adjust the pH of the feed water to 3.5 to 4 or more.
In addition, the desalting performance is affected by the pH of the feed water, and when the pH is 4 or less, the performance deteriorates rapidly. Therefore, the application lower limit value in the present embodiment is preferably 3.5 or more, and more preferably 4 or more.
Here, lowering the pH to a lower value results in the use of more chemicals, and the economic efficiency deteriorates. Therefore, from the viewpoint of economy, the vicinity of neutrality is a preferable condition as much as possible.
As described above, the pH adjustment range by the pH adjustment device 120 is preferably about pH 3.5 to 6.5, and most preferably about 5 to 6 is most preferable.

  In addition, when the container sterilization washing waste water contains acetic acid, the pH of the waste water stock solution is 6 or less. As described above, the disinfectant decomposition catalyst 112 of the disinfectant decomposer 110 has a high decomposition efficiency on the neutral to alkaline side, as described above. It needs to be adjusted. The adjustment to the acidic side by the pH adjuster 120 should be performed after the disinfectant is decomposed by the disinfectant decomposition catalyst 112. However, when there is no problem in the decomposition efficiency, the optimum pH of the reverse osmosis membrane in the previous stage of the catalyst You may adjust it.

[Example]
Hereinafter, the present embodiment (Embodiment 1) will be specifically described with reference to examples. However, this embodiment does not limit the present embodiment.
Example 1
In each example and comparative example, SU600 (anion charged, NF membrane) manufactured by Toray Industries, Inc. was used as the reverse osmosis membrane processing apparatus 130. In addition, Sanikulens PET (containing cation and nonionic surfactant) manufactured by Ecolab Co., Ltd. was used as a conveyor lubricant. In Example 1, when the stock solution of the conveyor lubricant was diluted 41 times as the film immersion liquid, the pH after dilution was 5.8. The test conditions for the membrane treatment were a water recovery rate of 50%, a filtration pressure of 0.35 MPa, and the test stock solution used sterilized washing waste water from a PET bottle container. As a test procedure, first, the initial permeation flux (L / m 2 · h) was measured and then immersed in an immersion liquid (diluted liquid for conveyor lubricant) for 15 hours. Finally, after thoroughly washing with pure water, the permeation flux was measured.

(Example 2)
As the reverse osmosis membrane treatment device 130, SU600 manufactured by Toray Industries, Inc. was used in the same manner. As a conveyor lubricant, Lubo Drive ZF (containing cation, anion and nonionic surfactant) manufactured by Ecolab Co., Ltd. was used. In Example 2, when the stock solution of the conveyor lubricant was diluted 33 times as the film immersion liquid, the pH after dilution was 3.9. Other conditions are the same as in the first embodiment.

(Comparative Example 1)
As the reverse osmosis membrane treatment device 130, SU600 manufactured by Toray Industries, Inc. was used in the same manner. In addition, as a conveyor lubricant, Sanikulens PET manufactured by Ecolab Co., Ltd. was used as in Example 1. In Comparative Example 1, the pH of the film soaking solution was adjusted to 7 with caustic soda. Other conditions are the same as in the first embodiment.

(Comparative Example 2)
As the reverse osmosis membrane treatment device 130, SU600 manufactured by Toray Industries, Inc. was used in the same manner. As a conveyor lubricant, Lubo Drive ZF manufactured by Ecolab Co., Ltd. was used as in Example 2. In Comparative Example 2, the pH of the film soaking solution was adjusted to 7 with caustic soda. Other conditions are the same as in the first embodiment.

  Table 2 shows changes in the permeation flux with respect to the conveyor lubricant before being diluted with the diluent in each of the above examples.

As shown in Table 2, when the pH of the immersion liquid is 7 in Comparative Example 1 and Comparative Example 2, the permeation flux is reduced to 87% and 85% compared to before immersion. On the other hand, when the pH of the immersion liquid is adjusted to the acidic side in Example 1 and Example 2, the permeation flux after immersion is 99% and 95% before immersion, and the permeation flux is reduced. Can be suppressed.
In this way, by adjusting the pH to 6 or less before passing through the reverse osmosis membrane treatment device 130, the permeation flux of the reverse osmosis membrane treatment device 130 is unlikely to decrease, and the reverse osmosis membrane treatment device 130. Stable operation over a long period of time.

(Embodiment 2)
In the first embodiment, as shown in FIG. 1, by providing a pH adjusting device 120 that adjusts the pH to 6 or less as a pretreatment of the reverse osmosis membrane processing device 130, the cationic or nonionic surfactant is reversed. Adsorption to the membrane surface of the osmotic membrane treatment apparatus 130 was suppressed. In the second embodiment, a cation-charged reverse osmosis membrane is used in advance in a system in which the effluent contains a cationic or nonionic surfactant in order to cope with the same problem as in the first embodiment. This suppresses the occurrence of a decrease in the permeation flux on the membrane surface due to the cationic or nonionic surfactant.
The same functions as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here.

  FIG. 2 is a diagram illustrating an overall configuration of the waste water treatment system 100 according to the second embodiment. The waste water treatment system 100 shown in FIG. 2 is provided with a reverse osmosis membrane treatment device 150 made of a cationically charged membrane on the downstream side of the disinfectant decomposition device 110. In general wastewater treatment, the raw water contains a lot of natural organic substances having anion charge. For this reason, if a cation-charged membrane is used as the reverse osmosis membrane, the membrane is immediately clogged. Therefore, in the waste water treatment, an anion-charged membrane is usually used. However, in the present embodiment, the characteristics of drainage from a beverage manufacturing plant that uses pure water and does not contain much natural organic matter, and in recent years, cationic or nonionic surfactants have been used as conveyor lubricants. In view of the fact that the reverse osmosis membrane treatment apparatus 150 is often used, a cationically charged membrane is used.

  In the waste water treatment system shown in FIG. 2, waste water containing a conveyor lubricant made of a cationic or nonionic surfactant from a rinser or a paste riser is treated. At this time, first, the waste water contained in the conveyor lubricant is adjusted to near neutrality with caustic soda or the like (when the pH of the waste water stock solution is 6 or less) in the pH adjustment 111 of the sterilizing agent decomposing apparatus 110. Thereafter, the solution is passed through a sterilizing agent decomposition catalyst 112 mainly composed of activated carbon in the sterilizing agent decomposing apparatus 110 to decompose the contained sterilizing agent (sodium hypochlorite, hydrogen peroxide, peracetic acid, etc.). In the present embodiment, the waste water in which the disinfectant is decomposed in this way is passed through a reverse osmosis membrane treatment apparatus 150 made of a cationically charged reverse osmosis membrane. By using this cationically charged membrane in the reverse osmosis membrane treatment apparatus 150, it is possible to prevent the cationic surfactant from adsorbing on the membrane surface and blocking the membrane surface.

〔Example〕
Hereinafter, this embodiment (Embodiment 2) will be described in detail with reference to examples. However, this embodiment does not limit the present embodiment.
(Example 3)
Here, SU200 (cation charge, NF membrane) manufactured by Toray Industries, Inc. was used as the reverse osmosis membrane treatment apparatus 150. In addition, Sanikulens PET (containing cation and nonionic surfactant) manufactured by Ecolab Co., Ltd. was used as a conveyor lubricant. When the stock solution of the conveyor lubricant was diluted 41 times as the film immersion liquid, the pH after dilution was 5.8. This was adjusted to 7 with caustic soda. The test conditions for the membrane treatment were a water recovery rate of 50%, a pressure during filtration of 0.75 MPa, and the test stock solution used sterilized washing waste water from a PET bottle container. As a test procedure, first, the initial permeation flux was measured, and then immersed in an immersion liquid (conveyor lubricant diluent) for 15 hours. Then, after thoroughly washing with pure water, the permeation flux was measured.

(Comparative Example 3)
As the reverse osmosis membrane treatment apparatus 150, SU600 (anion charged, NF membrane) manufactured by Toray Industries, Inc. was used. As the conveyor lubricant, Sanikulens PET manufactured by Ecolab Co., Ltd., which is the same as in Example 3, was used, and all other conditions were the same as in Example 3.

  Table 3 shows changes in the permeation flux with respect to the conveyor lubricant before being diluted with the diluent in each of the above examples.

When the anion-charged reverse osmosis membrane treatment apparatus 150 is used as in Comparative Example 3 shown in Table 3, the permeation flux is 87% lower than that before the immersion. On the other hand, when the cationically charged reverse osmosis membrane treatment apparatus 150 was used as in Example 3, the permeation flux after immersion could be maintained as high as 99%, and a decrease in permeation flux could be suppressed.
Thus, by using a cation charged membrane for the reverse osmosis membrane treatment device 150, the permeation flux of the reverse osmosis membrane treatment device 150 is less likely to decrease, and the reverse osmosis membrane treatment device 150 can be operated stably over a long period of time. Can be made possible.

  The present invention can be applied to, for example, a wastewater collection system in a beverage manufacturing factory, such as a general filling facility or an aseptic filling facility.

DESCRIPTION OF SYMBOLS 10 ... Beverage filling equipment, 100 ... Waste water treatment system, 110 ... Disinfectant decomposition device, 111 ... pH adjustment, 112 ... Catalyst for disinfecting disinfectant, 120 ... pH adjustment device, 130 ... Reverse osmosis membrane treatment device, 150 ... Reverse osmosis Membrane treatment equipment

Claims (3)

Is discharged from the beverage manufacturing plant, the wastewater containing cationic surfactants, once was adjusted to neutral, and passed through the sterilizing agent decomposition catalyst to decompose the disinfectant contained in the waste water,
A method for treating wastewater containing a surfactant, wherein the wastewater that has passed through the catalyst for disinfecting disinfectant is passed through a cationically charged reverse osmosis membrane. Is discharged from the beverage manufacturing plant, a wastewater treatment system for treating waste water containing a cationic surfactant,
After adjusting the wastewater containing the surfactant to neutral once, it is passed through a catalyst for disinfecting a disinfectant to disinfect the disinfectant contained in the wastewater ,
A wastewater treatment system comprising: a reverse osmosis membrane treatment device for filtering wastewater from which the bactericide has been decomposed by the disinfectant decomposition device using a cationically charged reverse osmosis membrane. The waste water treatment system according to claim 2 , wherein the waste water is a rinser waste water and / or a pasteurizer waste water used for sterilizing and washing containers.

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