Nori seaweed water treatment equipment that uses seawater electrolysis hydrogen gas as a reducing agent.

Abstract

The present invention provides a seaweed-making water treatment device that uses seawater electrolysis hydrogen gas as a reducing agent. [Solution] Seawater electrolysis water is added to the wastewater (wastewater from paper making) left after papering seaweed in the paper making section 21 of the seaweed production equipment 20 to sterilize and decolorize the wastewater from paper making, and furthermore, by bringing the hydrogen-containing gas generated by the seawater electrolysis reaction into contact with the sterilization and decolorization reaction treated water, the chlorine-based oxidizing components (residual chlorine) remaining in the sterilization and decolorization reaction treated water are decomposed and removed, and the treated water is reused as paper making water, etc. The system is inexpensive enough to be introduced into small-scale seaweed production facilities, and is capable of sufficiently purifying wastewater from paper making, which can contribute to reducing water bills and therefore seaweed production costs.

Description

[Technical Field]

[0001] This invention relates to a seaweed-making water treatment device equipped with a brine electrolysis reactor and a sterilization and decolorization reactor used for water reclamation. More specifically, this invention relates to a seaweed-making water treatment device equipped with a brine electrolysis reactor and a sterilization and decolorization reactor used for water reclamation, which purifies wastewater discharged from seaweed-making equipment and reuses it as seaweed-making water. [Background technology]

[0002] Dried seaweed for consumption is generally made by shredding raw seaweed harvested at seaweed farms and feeding it to seaweed manufacturing equipment using tap water, where it goes through the papering, dehydration, drying, and peeling processes. In the papering process, about 1 liter of water is used per sheet of seaweed, but because water charges account for a high proportion of seaweed production costs, there have been attempts to use groundwater instead of tap water. However, if the quality of the water used in the paper-making process is poor, the quality of the nori product will decline and it will also become unsanitary, so tap water is often used, which does not result in a reduction in nori production costs.

[0003] Therefore, in order to reduce water costs, it has recently been proposed to treat the wastewater after laver making (hereinafter simply referred to as "laver making wastewater") with ozone to sterilize and decolorize it, and then reuse the treated wastewater as laver making water (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] YBM Corporation, "GAS SOLUTION Ultra Fine Bubble Generator," pp. 3-5, [online], [Retrieved June 6, 2022], Internet (URL: https: / / www.fuki-ss.co.jp / wp-content / uploads / faby-formjet.pdf) Summary of the Invention [Problem to be solved by the invention]

[0005] However, the ozone treatment equipment proposed in Non-Patent Document 1 and elsewhere is expensive, and so at present, its introduction is limited to large-scale seaweed production facilities.In addition, the purification treatment (sterilization and decolorization) of wastewater from seaweed production using ozone treatment is not necessarily sufficient. For this reason, there was a need to develop a technology that was inexpensive enough to be introduced into small-scale seaweed production facilities (seaweed production and processing lines run by small, individual businesses), that could sufficiently purify the wastewater from the seaweed-making process, and that could contribute to reducing water bills and ultimately seaweed production costs.

[0006] The present invention was made in consideration of the above circumstances, and aims to provide a seaweed-making water treatment device that is inexpensive enough to be introduced in small-scale seaweed production facilities, can sufficiently purify wastewater from seaweed-making, and is equipped with a brine electrolysis reactor and a sterilization and decolorization reactor used for regenerating seaweed-making water, which can contribute to reducing water bills and ultimately seaweed production costs. [Means for solving the problem]

[0007] In order to achieve the above object, the construction of the water recycling device according to the present invention is as follows: (1) A water recycling system comprising: a brine electrolysis reactor that generates brine electrolysis water by brine electrolysis reaction to sterilize and decolorize wastewater after laver production in a laver production facility; and a sterilization and decolorization reactor that decomposes and removes chlorine-based oxidizing components (residual chlorine) remaining in the sterilization and decolorization reaction treated water by bringing the hydrogen-containing gas generated by the brine electrolysis reaction into contact with the sterilization and decolorization reaction treated water, which is wastewater that has been sterilized and decolorized with the brine electrolysis water. The system enables the sterilization and decolorization reaction treated water, from which chlorine-based oxidizing components have been decomposed and removed, to be reused as water for laver production.

[0008] In the present invention, electrolyzed salt water can be, for example, electrolyzed seawater.

[0009] The above-mentioned configuration (1) of the planting water recycling device of the present invention has the following effects. In other words, electrolyzed brine water can be produced and supplied at low cost and has excellent sterilization and decolorization properties. Furthermore, the hydrogen-containing gas used here is generated as a by-product of the brine electrolysis reaction, has high purity, and is also excellent in the ability to decompose and remove chlorine-based oxidizing components (residual chlorine) remaining in the sterilization and decolorization reaction treated water. Therefore, according to the configuration (1) above, it is possible to provide a water recycling device that is inexpensive enough to be introduced into small-scale seaweed production facilities (seaweed production and processing lines run by small-scale individual business owners), can sufficiently purify and treat wastewater from seaweed making, and can contribute to reducing water bills and ultimately seaweed production costs.

[0010] The brine electrolysis reactor according to the present invention is configured as follows: (2) A brine electrolysis reactor used in the construction of the papermaking water reclamation device of the present invention as described above in (1), a brine electrolysis reaction tank; and an anode material and a cathode material that are disposed in the brine electrolysis reaction tank and that electrolyze brine in the brine electrolysis reaction tank when a voltage is applied thereto; The brine electrolysis reaction vessel is characterized in that a space is provided at the bottom thereof in which exfoliated metal hydroxide crystals deposited on the surface of the cathode material during the brine electrolysis reaction can be deposited.

[0011] The above-mentioned configuration (2) of the brine electrolysis reactor of the present invention has the following effects. That is, during operation of the brine electrolysis reactor, crystals of metal hydroxides such as magnesium hydroxide, which are mainly composed of magnesium ions in brine, are precipitated on the surface of the cathode material, and during long-term operation, the crystals peel off from the surface of the cathode material and deposit at the bottom. However, the above-mentioned configuration (2) can effectively deal with this phenomenon.

[0012] In the above-mentioned configuration (2) of the brine electrolysis reactor of the present invention, it is preferable to adopt the following configuration (3).

[0013] (3) In the configuration of (2) above, the anode material is made of a platinum-based electrode material, and the cathode material is made of titanium or SUS.

[0014] In addition, the configuration of the sterilization and decolorization reaction apparatus according to the present invention is as follows: (4) A sterilization and decolorization reaction device used in the above-mentioned (1) configuration of the planting water recycling device of the present invention, a sterilization and decolorization reaction tank for sterilizing and decolorizing the wastewater using an oxidizing agent containing sodium hypochlorite (NaClO) as a main component contained in the electrolyzed brine; a gas-liquid contact reaction tank provided downstream of the sterilization and decolorization reaction tank for decomposing and removing chlorine-based oxidizing components (residual chlorine (sodium hypochlorite (NaClO))) remaining in the sterilization and decolorization reaction treated water, The sterilization and decolorization reaction tank and the gas-liquid contact reaction tank are characterized in that they are push-flow type reaction tanks with a four-tank structure having a first reaction tank, a second reaction tank, a third reaction tank, and a fourth reaction tank in that order, separated by a partition plate.

[0015] In the above-mentioned configuration (4) of the sterilization and decolorization reaction apparatus of the present invention, it is preferable to configure it as in the following (5) to (7).

[0016] (5) In the configuration of (4), the first reaction tank is a reaction tank in which a sterilization reaction proceeds, The second reaction tank is a reaction tank in which a decolorization reaction of an easily decolorizable component proceeds, The third reaction tank is a reaction tank using a granular catalyst that promotes the decomposition reaction of difficult-to-decolorize components by residual chlorine, The fourth reaction tank is a reaction tank in which the hydrogen-containing gas generated by the brine electrolysis reaction is brought into contact with the treated water from the third reaction tank, and the chlorine-based oxidizing components (residual chlorine) remaining in the treated water from the third reaction tank are reduced and decomposed for removal.

[0017] The preferable configuration of (5) above has the following effects. In other words, there are 10% of bacteria in the wastewater from the planting water. 4 ~10 6The inventors have demonstrated through a series of studies that adding electrolyzed brine water to this papermaking wastewater achieves almost complete sterilization by adding an amount of water with an effective chlorine concentration of several ppm and setting the reaction time to 0.5 to 2 minutes. Furthermore, because the bacteria in the papermaking wastewater can be sterilized even when the residence time of the water to be treated (papermaking wastewater) is kept as short as around 2 minutes, it is possible to reduce the capacity of the first reaction tank. Furthermore, because the easily decolorizable components are decolorizable in a short time of about 1 to 2 minutes, it is possible to reduce the capacity of the second reaction tank. By providing a decolorizing reaction tank (third reaction tank) using a granular catalyst that promotes the decomposition reaction of the difficult-to-decolorize components downstream of the second reaction tank, it is possible to shorten the reaction time and reduce the total capacity of the second and third reaction tanks. Therefore, according to the preferred configuration of (5) above, it is possible to provide a sterilization and decolorization reaction apparatus that is inexpensive enough to be introduced into small-scale seaweed production facilities, can sufficiently purify wastewater from seaweed making, and can contribute to reducing water bills and ultimately seaweed production costs.

[0018] (6) In the above configuration (5), the granular catalyst is an eggshell-type catalyst in which a catalytically active metal component, mainly composed of nickel peroxide or cobalt peroxide, is supported on the outer surface of porous particles. According to the preferable configuration of (6) above, it is possible to realize a granular catalyst that is effective in promoting the decomposition reaction (bleaching reaction) of components that are difficult to bleach.

[0019] (7) In the configuration of (4) above, when the volume of the first reaction tank is Vr1, the volume of the second reaction tank is Vr2, and the volume of the third reaction tank is Vr3, Vr1 <Vr2<Vr3 Fulfilling the relationship. [Effects of the Invention]

[0020] According to this invention, it is possible to provide a seaweed-making water treatment device that is inexpensive enough to be introduced into small-scale seaweed production facilities (seaweed production and processing lines run by small, individual business owners), is capable of sufficiently purifying and treating wastewater from seaweed-making, and is equipped with a brine electrolysis reactor and a sterilization and decolorization reactor used to regenerate seaweed-making water, which can contribute to reducing water bills and ultimately seaweed production costs. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a block diagram showing the configuration of a water reclamation system for realizing a water reclamation device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a longitudinal sectional view showing the schematic configuration of a sterilization and decolorization reaction apparatus according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be described in more detail below with reference to preferred embodiments, but the following embodiments are merely examples of the present invention and are not intended to limit the scope of the present invention.

[0023] (Configuration of the planting water reclamation device) First, the configuration of a planting water recycling apparatus according to one embodiment of the present invention will be described with reference to FIG.

[0024] FIG. 1 is a block diagram showing the configuration of a water reclamation system for realizing a water reclamation device according to one embodiment of the present invention.

[0025] The papermaking water recycling apparatus of this embodiment adds electrolyzed seawater to wastewater (papermaking wastewater) after papermaking in a nori production apparatus to sterilize and decolorize the papermaking wastewater. Furthermore, hydrogen-containing gas generated by the seawater electrolysis reaction is brought into contact with the sterilized and decolorized treated water to decompose and remove chlorine-based oxidizing components (residual chlorine) remaining in the sterilized and decolorized treated water, allowing the treated water to be reused as papermaking water, etc. Thus, in the papermaking water recycling apparatus of this embodiment, electrolyzed seawater containing sodium hypochlorite is used as an oxidizing agent for sterilizing and decolorizing the papermaking wastewater. Furthermore, hydrogen-containing gas generated by the seawater electrolysis reaction is used to decompose and remove chlorine-based oxidizing components (residual chlorine) remaining in the sterilized and decolorized treated water.

[0026] The construction of the planting water recycling apparatus of this embodiment has the following advantages. In other words, electrolyzed seawater can be produced and supplied at low cost and has excellent sterilization and decolorization properties. The hydrogen-containing gas used here is a by-product of the seawater electrolysis reaction, has high purity, and is also excellent in decomposing and removing chlorine-based oxidizing components (residual chlorine) remaining in the sterilization and decolorization reaction treated water. Therefore, with this configuration, it is possible to provide a seaweed water recycling device that is inexpensive enough to be introduced into small-scale seaweed production facilities (seaweed production and processing lines run by small-scale individual business owners), is capable of sufficiently purifying and treating wastewater from seaweed making, and can contribute to reducing water bills and ultimately seaweed production costs.

[0027] This will be explained in more detail below. The brewing water recycling apparatus of this embodiment can be realized, for example, by the brewing water recycling system shown in FIG. The seaweed-making water reclamation system shown in FIG. 1 includes a seaweed-making apparatus 20 having a paper-making section 21, a seawater electrolysis reactor 22 for generating electrolyzed seawater for sterilizing and decolorizing wastewater (seaweed-making wastewater) after seaweed is made in the paper-making section 21, and a sterilization / decolorization reactor 1 for adding the electrolyzed seawater to the seaweed-making wastewater to sterilize and decolorize the seaweed-making wastewater. The seaweed-making wastewater that has been sterilized and decolorized in the sterilization / decolorization reactor 1 is further contacted with hydrogen-containing gas generated by the seawater electrolysis reaction, thereby decomposing and removing residual chlorine-based oxidizing components (residual chlorine), resulting in reclaimed water. The reclaimed water is then temporarily stored in a water storage tank 23, similar to tap water, and reused for various purposes as a substitute for tap water. For example, the reclaimed water is sent from the water storage tank 23 to the paper-making section 21 of the seaweed-making apparatus 20 and reused as seaweed-making water. Furthermore, the reclaimed water in the water tank 23 can be reused for cleaning or other purposes, for example. The seawater electrolysis reactor 22 and the sterilization and decolorization reactor 1 will be described in detail later.

[0028] (Configuration of seawater electrolysis reactor) Next, the configuration of a seawater electrolysis reactor according to one embodiment of the present invention will be described.

[0029] The seawater electrolysis reactor 22 shown in Fig. 1 is used in the papermaking water reclamation system of this embodiment. More specifically, this seawater electrolysis reactor is used to produce electrolyzed seawater as an oxidizing agent for sterilizing and decolorizing the papermaking wastewater. Furthermore, the hydrogen-containing gas generated as a by-product of the seawater electrolysis reaction is used to decompose and remove chlorine-based oxidizing components (residual chlorine) remaining in the sterilization and decolorization reaction treated water.

[0030] The seawater electrolysis reactor of this embodiment includes a seawater electrolysis reactor tank, and an anode material and a cathode material that are disposed in the seawater electrolysis reactor tank and electrolyze seawater in the seawater electrolysis reactor tank when a voltage is applied thereto, The seawater electrolysis reactor is characterized in that a space is provided in the lower part of the seawater electrolysis reactor, where exfoliated crystals of metal hydroxides such as magnesium hydroxide, which are mainly composed of magnesium ions and precipitated on the surface of the cathode material during the seawater electrolysis reaction, can be deposited.

[0031] <About seawater> Seawater from seaweed cultivation areas can be used. The salt concentration in seawater is usually about 3 wt.%, and it can be used as is or diluted with tap water. However, since a lower salt concentration reduces the current efficiency in the electrolysis reaction, in practice, the salt concentration is preferably in the range of about 1 to 3 wt.%, and more preferably in the range of about 2 to 3 wt.%.

[0032] <Structure of the seawater electrolysis reactor> Seawater electrolysis reactors can be either monopolar (single-pole) or bipolar (two-pole, multi-pole) types. Seawater can be passed through the seawater electrolysis reactor either upflow or crossflow, depending on the installation space and ease of maintenance at the site where the seawater electrolysis reaction is performed. Regardless of the type of system used, however, during operation, crystals of metal hydroxides such as magnesium hydroxide, primarily composed of magnesium ions in seawater, precipitate on the surface of the cathode material. Over long periods of operation, these crystals peel off from the surface of the cathode material and settle at the bottom. Therefore, it is important to design the electrolysis reactor so that a certain amount of space (empty space) is provided at the bottom of the seawater electrolysis reactor.

[0033] <Electrode materials> The anode material for the electrode used in the seawater electrolysis reaction can be a platinum-based electrode material such as a platinum-plated titanium substrate or a platinum-baked DSE electrode, while the cathode material can be titanium or SUS (stainless steel).

[0034] (Configuration of sterilization and decolorization reaction device) Next, the configuration of a sterilization and decolorization reaction apparatus according to one embodiment of the present invention will be described with reference to FIG.

[0035] FIG. 2 is a longitudinal sectional view showing the schematic configuration of a sterilization and decolorization reaction apparatus according to one embodiment of the present invention.

[0036] The sterilization and decolorization reaction apparatus 1 shown in Fig. 2 is used in the papermaking water recycling apparatus of the present embodiment. More specifically, the sterilization and decolorization reaction apparatus 1 is used to sterilize and decolorize the papermaking wastewater by adding electrolyzed seawater to the papermaking wastewater. The sterilization and decolorization reaction apparatus 1 also brings hydrogen-containing gas generated by the seawater electrolysis reaction in the seawater electrolysis reactor 22 into contact with the sterilization and decolorization reaction-treated water, thereby reducing and decomposing and removing chlorine-based oxidizing components (residual chlorine) remaining in the sterilization and decolorization reaction-treated water.

[0037] As shown in Figure 2, the sterilization and decolorization reaction apparatus 1 includes a rectangular parallelepiped sterilization and decolorization reaction tank 2 with a partially open top, which sterilizes and decolorizes the papermaking wastewater using an oxidizing agent whose main component is sodium hypochlorite (NaClO) contained in electrolyzed seawater. The sterilization and decolorization reaction tank 2 is a four-tank push-flow type reaction tank having a first reaction tank 7, a second reaction tank 8, a third reaction tank 9, and a fourth reaction tank 10, separated in order by partition plates 3, 4, and 5. The fourth reaction tank 10 is further separated into two tanks by a partition plate 6. The sterilization and decolorization reaction tank 2 is also provided with a treated water storage tank 12 integrally disposed adjacent to a wall plate 13 at the downstream end.

[0038] Partition plates 3 and 5 are open at their lower ends, and partition plate 4 is open at its upper end. Partition plate 6 is also open at its upper end, with the lower edge of the opening of partition plate 6 being lower than the lower edge of the opening of partition plate 4. Wall plate 13 at the downstream end of sterilization / decolorization reaction tank 2 is also open at its lower end. This allows the papermaking wastewater to flow vertically in a zigzag pattern from first reaction tank 7 to fourth reaction tank 10 (see arrows A, B, C, and D in Figure 2). The wastewater from the planting water (sterilization and decolorization reaction treated water) that has been passed through the first reaction tank 7 to the third reaction tank 9 and has been subjected to sterilization and decolorization is passed through the fourth reaction tank 10 where any chlorine-based oxidizing components (residual chlorine) remaining in the sterilization and decolorization reaction treated water are decomposed and removed. The water then passes through the lower opening of the wall panel 13 at the downstream end of the sterilization and decolorization reaction tank 2 (see arrow E in Figure 2) and is temporarily stored in the treated water storage tank 12, where it can be reused as planting water, etc. In this invention, the treated water storage tank is not included in the sterilization and decolorization reaction tank. Therefore, in this embodiment, the treated water storage tank 12 may be provided separately from the sterilization and decolorization reaction tank 2.

[0039] As described above, in this embodiment, a sterilization and decolorization reaction apparatus 1 of the push flow type is used, in which the sterilization and decolorization reaction tank 2, which performs sterilization, decolorization, and decomposition and removal of residual chlorine, is divided by partition plates 3, 4, 5, and 6 to form a multi-tank structure.

[0040] This will be explained in more detail below. The first reaction tank 7 is a reaction tank (sterilization reaction tank) in which a sterilization reaction proceeds. More specifically, the first reaction tank 7 is a reaction tank in which electrolyzed seawater is added to and mixed with the wastewater papermaking water to carry out a sterilization treatment. The wastewater from the planting water contains 10% of bacteria. 4 ~10 6 The present inventors have demonstrated through a series of studies that when electrolyzed seawater is added to this wastewater papermaking water, sterilization is nearly complete by adding an amount of seawater with an effective chlorine concentration of several ppm and setting the reaction time to 0.5 to 2 minutes. Furthermore, because the bacteria in the wastewater papermaking water can be sterilized even when the residence time of the water to be treated (wastewater papermaking) is kept as short as about 2 minutes, it is possible to reduce the capacity of the first reaction tank 7.

[0041] The second reaction tank 8 is a reaction tank (bleaching reaction tank) in which the decolorization reaction of the easily decolorizable component proceeds. More specifically, the second reaction tank 8 is a reaction tank for promoting the oxidative decolorization reaction of the chlorine-based oxidizing agent. Thus, the purpose of the second reaction tank 8 is to promote the decolorization reaction by the oxidation reaction of available chlorine.

[0042] This research also revealed that there are two types of decolorization reactions of red-colored substances in wastewater papermaking water: one that proceeds in a reaction time similar to that of a sterilization reaction, and one that takes a longer time. Based on this, the inventors determined that wastewater papermaking water contains components that are easily decolorized in a short reaction time of about 1 to 2 minutes (easily decolorized components) and components that are difficult to decolorize in a short reaction time of about 2 minutes (hardly decolorized components). Therefore, the primary purpose of the second reaction tank 8 was to decolorize the easily decolorized components.

[0043] In order to decolorize difficult-to-decolorize components to the desired water quality, a large-capacity reaction tank structure is required to extend the reaction time, but the inventors determined that this would make the entire device larger and difficult to introduce into small-scale seaweed production facilities (making it less practical). Therefore, in order to reduce the overall volume of the device (make it compact), the inventors conducted experiments to find a catalyst that would be effective in accelerating the decolorization reaction of difficult-to-decolorize components, and found an effective catalyst. Based on the results, they decided to shorten the reaction time by installing a decolorization reaction tank using a catalyst downstream of the second reaction tank 8. As a result, it became possible to reduce the overall capacity of the second and third reaction vessels 8 and 9.

[0044] Therefore, the configuration of the sterilization and decolorization reaction apparatus 1 of this embodiment makes it possible to provide a sterilization and decolorization reaction apparatus that is inexpensive enough to be introduced into small-scale seaweed production facilities, can sufficiently purify wastewater from seaweed making, and can contribute to reducing water bills and ultimately seaweed production costs.

[0045] The third reaction tank 9 is a reaction tank that uses a granular catalyst 11 that promotes the decomposition reaction of the difficult-to-decolorize components with residual chlorine. More specifically, the third reaction tank 9 is a reaction tank (a decolorization reaction tank using a catalyst, a catalytic reaction tank) for promoting the oxidative decolorization reaction of the chlorine-based oxidizing agent. If the third reaction tank 9 is filled with granular catalyst 11, the capacity of the third reaction tank 9 can be significantly reduced. However, since the catalyst filling method requires maintenance and management, it is preferable to determine whether to apply this method based on the conditions of the application site.

[0046] <About the decolorization reactor using a catalyst> This research also confirmed that nickel peroxide and cobalt peroxide catalysts are effective as granular catalysts 11. Catalysts of this type have been confirmed to be effective as decomposition catalysts for organic substances such as methanol, ethanol, and phenol contained in water, and have been put to practical use. In this study, we prototyped a granular catalyst to promote the decolorization reaction of difficult-to-decolorize components in the papermaking wastewater, and conducted repeated experiments to confirm the decolorization effect using the prototype catalyst to conduct research to find an effective catalyst. As a result, we were able to confirm the catalyst preparation conditions applicable to this purpose.

[0047] <About the catalyst> To achieve practical application of this system as a purification system for wastewater from papermaking water, it is necessary to achieve an effect with a short contact time. Therefore, the inventors determined that the residence time in the catalytic reaction tank (third reaction tank 9) should be approximately 1 to 5 minutes. Since it takes a long time for reactants to diffuse into the pores of a granular catalyst, they determined that a catalyst in which catalytically active components are supported on the outer surface of porous particles is desirable, and they worked to prepare an effective catalyst. As a result, they confirmed that an eggshell-type catalyst in which catalytically active metal components, primarily nickel peroxide or cobalt peroxide, are supported on the outer surface of porous synthetic zeolite particles with a particle size of 2 to 5 mm is effective.

[0048] The fourth reaction tank 10 is a reaction tank (gas-liquid contact reaction tank) in which the hydrogen-containing gas generated by the seawater electrolysis reaction is brought into contact with the treated water (sterilization and decolorization reaction treated water) from the third reaction tank 9, and the chlorine-based oxidizing components (residual chlorine) remaining in the sterilization and decolorization reaction treated water are reduced and decomposed for removal. The provision of this gas-liquid contact reactor is the most significant feature of this invention.

[0049] <Gas-liquid contact reactor> The gas-liquid contact reaction tank (fourth reaction tank 10) for the treated water (sterilization and decolorization reaction treated water) from the third reaction tank 9 and the hydrogen-containing gas generated by the seawater electrolysis reaction is sealed and is constructed so that the water level in the overflow water storage tank is approximately half the height of the partition plate 6 over which the sterilization and decolorization reaction treated water overflows. The hydrogen-containing gas flows into the gas phase of the gas-liquid contact reaction tank (fourth reaction tank 10) from a position higher than the water level in the overflow water storage tank, and comes into countercurrent contact with the sterilization and decolorization reaction treated water (residual chlorine-containing water) overflowing from above. The gas after gas-liquid contact treatment is constructed to be discharged from an exhaust port 15 provided in the reactor ceiling 14. With the above-mentioned configuration, hydrogen gas is dissolved in residual chlorine-containing water by gas-liquid contact, and the residual chlorine can be decomposed by the reduction action of hydrogen. Because this reaction proceeds in an extremely short time, the residual chlorine concentration in the treated water in the overflow water storage tank becomes the same as that of the original tap water. The treated water is sterile, colorless, and transparent, and can be reused for making laver seaweed, etc.

[0050] In the sterilization and decolorization reaction apparatus 1 of this embodiment, when the volume of the first reaction tank 7 is Vr1, the volume of the second reaction tank 8 is Vr2, and the volume of the third reaction tank 9 is Vr3, Vr1 <Vr2<Vr3 It fulfills a relationship. These relationships were determined based on the above-mentioned technical knowledge obtained through repeated purification experiments of wastewater from papermaking plants using electrolyzed seawater.

[0051] The results of the Examples and Comparative Examples show that the provision of a gas-liquid contact reactor allows for sufficient purification of papermaking wastewater.

[0052] In the above embodiment, the electrolyzed salt water is described as electrolyzed seawater. However, the present invention is not necessarily limited to this configuration. As long as the electrolyzed salt water is obtained by electrolyzing salt water, it may be, for example, electrolyzed artificial seawater or electrolyzed saline water. The electrolyzed brine water can be produced using an electrolysis reactor having the same structure as the seawater electrolysis reactor of the above embodiment. [Explanation of symbols]

[0053] 1. Sterilization and decolorization reactor 2. Sterilization and decolorization reaction tank 3, 4, 5, 6 Dividers 7. First Reactor 8. Second Reactor 9. Third Reactor 10. 4th Reactor 11 Granular catalyst 12 Treated water storage tank 13 Wallboard 14 Reactor ceiling 15 exhaust port 20 Nori production equipment 21. Papermaking Department 22 Seawater electrolysis reactor 23 Water Tank

Claims

1. This papermaking water recycling system comprises: a brine electrolysis reactor that generates brine electrolysis water by brine electrolysis reaction to sterilize and decolorize wastewater after papering seaweed in a papermaking apparatus; and a sterilization and decolorization reactor that decomposes and removes chlorine-based oxidizing components remaining in the sterilization and decolorization reaction treated water by bringing the hydrogen-containing gas generated by the brine electrolysis reaction into contact with the sterilization and decolorization reaction treated water, which is wastewater that has been sterilized and decolorized with the brine electrolysis water. This allows the sterilization and decolorization reaction treated water, from which chlorine-based oxidizing components have been decomposed and removed, to be reused as papermaking water.

2. The brine electrolysis reactor is a brine electrolysis reaction tank; and an anode material and a cathode material that are disposed in the brine electrolysis reaction tank and that electrolyze brine in the brine electrolysis reaction tank when a voltage is applied thereto; 2. The apparatus for reclaiming paper water according to claim 1, wherein a space is provided in the lower part of the brine electrolysis reaction tank in which exfoliated metal hydroxide crystals precipitated on the surface of the cathode material during the brine electrolysis reaction can be deposited.

3. 3. The papermaking water reclamation apparatus according to claim 2, wherein the anode material is made of a platinum-based electrode material, and the cathode material is made of titanium or SUS.

4. The sterilization and decolorization reaction apparatus comprises: a sterilization and decolorization reaction tank for sterilizing and decolorizing the wastewater using an oxidizing agent containing sodium hypochlorite as a main component contained in the electrolyzed brine; a gas-liquid contact reaction tank provided downstream of the sterilization and decolorization reaction tank for decomposing and removing chlorine-based oxidizing components remaining in the sterilization and decolorization reaction treated water; 2. The papermaking water recycling apparatus according to claim 1, wherein the sterilization and decolorization reaction tank and the gas-liquid contact reaction tank are push-flow type reaction tanks with a four-tank structure having a first reaction tank, a second reaction tank, a third reaction tank, and a fourth reaction tank in that order, separated by a partition plate.

5. The first reaction tank is a reaction tank in which a sterilization reaction proceeds, The second reaction tank is a reaction tank in which a decolorization reaction of an easily decolorizable component proceeds, The third reaction tank is a reaction tank using a granular catalyst that promotes the decomposition reaction of difficult-to-bleach components by residual chlorine, 5. The papermaking water reclamation apparatus according to claim 4, wherein the fourth reaction tank is a reaction tank that brings hydrogen-containing gas generated by the brine electrolysis reaction into contact with the treated water from the third reaction tank, thereby decomposing and removing chlorine-based oxidizing components contained in the treated water from the third reaction tank.

6. 6. The papermaking water reclamation apparatus according to claim 5, wherein the granular catalyst is an eggshell-type catalyst in which a catalytically active metal component, mainly composed of nickel peroxide or cobalt peroxide, is supported on the outer surface of porous particles.

7. When the volume of the first reaction tank is Vr1, the volume of the second reaction tank is Vr2, and the volume of the third reaction tank is Vr3, Vr1<Vr2<Vr3 5. The papermaking water recycling apparatus according to claim 4, wherein the following relationship is satisfied:

Images