JP5910720B1 - Paper manufacturing apparatus and waste water treatment method - Google Patents

Abstract

An object of the present invention is to find an addition condition of an oxidant for further improving the deodorization property, and to suppress the corrosion of a paper manufacturing apparatus and to reduce the cost. A paper manufacturing apparatus according to the present invention is selected from the group consisting of a wastewater treatment unit for treating water drained from a paper production unit for producing paper from raw materials, and treated water, scum and sludge. A treated water supply unit 40 for supplying at least one (hereinafter also referred to as “treated water”) to the same paper manufacturing unit 10 as the paper manufacturing unit 10 or another paper manufacturing unit 10 ′, and a wastewater processing unit. 30 or a weak oxidant supply unit 50 that supplies a weak oxidant having a redox potential of an aqueous solution smaller than that of an aqueous solution of sodium hypochlorite to treated water or the like in the treated water or the like supply unit 40; Of the above paper manufacturing units 10, 10 ′, etc., a sterilizing agent supply unit 60 for supplying a sterilizing agent to at least one of the paper manufacturing units 10, 10 ′ to which treated water is supplied by the processing water supply unit 40; Is provided. [Selection] Figure 1

Description

  The present invention relates to a paper manufacturing apparatus and a wastewater treatment method.

  In paper mills, the paper manufacturing process and the subsequent wastewater treatment process are neutral in pH, contain a large amount of starch, and have a water temperature of around 30-40 ° C. It tends to be easy to do. Furthermore, in the paper manufacturing process and wastewater treatment process, aluminum sulfate is generally used in large quantities as a raw material, chemical fixing agent, and flocculant, so a large amount of sulfate radicals are used in the paper manufacturing process or the subsequent drainage process. Included. In such an environment, the activity of sulfate-reducing bacteria becomes active, and sulfate radicals are reduced to hydrogen sulfide, which can cause off-flavors. In addition to hydrogen sulfide, the causes of off-flavors include organic acids (formic acid, acetic acid, propionic acid, lactic acid, butyric acid, etc.) that are mainly generated as metabolites of starch by microorganisms. Since these can affect not only the working environment in the factory but also the surrounding environment, it is extremely important to suppress the generation of substances that can cause off-flavors.

  Until now, the generation of off-flavors in paper mills is thought to be mainly due to the wastewater treatment process, and general deodorizing and deodorizing measures such as the use of weak oxidants exemplified by sodium chlorite have been taken. . However, for deodorizing and deodorizing measures in the paper manufacturing process, appropriate technology that meets the cost has not been established.

  Regarding deodorizing and deodorizing measures in the paper manufacturing process, a sodium hypochlorite aqueous solution of pH 4 or higher is introduced into a white water system tank or a recovery scum system tank, and the effective chlorine concentration in either tank is adjusted to 100 to 10 ppm. It has been proposed to deodorize each tank (see, for example, Patent Document 1).

JP 2005-336636 A

  However, in the technique described in Patent Document 1, sodium hypochlorite used as an oxidant reacts with starch remaining in the white water system tank and the recovery scum system tank, organic matter contained in sludge and scum, and the like. Decomposes into oxygen and sodium chloride. For this reason, the manager of the deodorizing treatment requires that sodium hypochlorite be excessively added in anticipation of decomposition of sodium hypochlorite. This excessive input can lead to a high concentration of salts contained in the circulating water and quality deterioration of polymer chemicals (such as a sticking agent, an antifoaming agent, a freeness of water, and a yield improving agent). Furthermore, since sodium hypochlorite has a high oxidizing power, excessive addition of sodium hypochlorite corrodes the metal of equipment and piping including white water system water tank and recovery scum system water tank, May affect paper manufacturing operations. The paper manufacturing process is a complex process with numerous tanks and chests, and it is important to consider where and how to add deodorant and deodorant chemicals to maximize cost effectiveness. However, this invention has not been fully studied.

  From the above, in the paper manufacturing apparatus, since the addition condition of the oxidant contributes to the deodorization property, it is required to make the addition condition of the oxidant more suitable.

  The present invention has been made to solve the above-mentioned problems, and its purpose is to find out the conditions for adding an oxidant for further improving the deodorizing property, and to suppress the corrosion of the paper manufacturing apparatus and reduce the cost. It is intended to reduce this.

  The present inventors have intensively studied to solve the above problems. As a result, the oxidation-reduction potential of the aqueous solution is hypochlorous acid with respect to at least one selected from the group consisting of treated water, scum and sludge generated by treating wastewater from the paper production department that produces paper from raw materials. By supplying a weak oxidizer that is lower than the redox potential of an aqueous solution of sodium, not only can the amount of oxidant be used, but also to sterilize sulfate-reducing bacteria and acetic acid bacteria in the paper production department. The effect of adding the bactericide to be used can be enhanced, and as a result, the present inventors have found that the paper manufacturing apparatus can be prevented from being corroded and the cost can be reduced while further improving the deodorizing property. Specifically, the present invention provides the following.

  (1) The present invention relates to a waste water treatment unit that treats water drained from a paper manufacturing unit that produces paper from raw materials, treated water treated in the waste water treatment unit, and scum present in the waste water treatment unit And at least one selected from the group consisting of sludge present in the wastewater treatment unit, a treated water supply unit for supplying the same or other paper production unit as the paper production unit, and the wastewater treatment unit or the Weak oxidation in which the redox potential of the aqueous solution is smaller than the redox potential of the aqueous solution of sodium hypochlorite for at least one selected from the group consisting of the treated water, the scum and the sludge in the treated water supply unit At least one selected from the group consisting of the treated water, the scum, and the sludge is supplied by the treated water supply unit among the weak oxidizing agent supply unit that supplies the agent and the one or more paper manufacturing units. A paper making apparatus and a sterilizing agent supply unit for supplying a disinfectant to at least one production unit.

  (2) Moreover, this invention is a measurement result in the 1st oxidation-reduction potential measurement part which measures the 1st oxidation-reduction potential with respect to the water contained in the waste water treatment part, and the 1st oxidation-reduction potential measurement part. The paper manufacturing apparatus according to (1), further comprising: a weak oxidant control unit that controls a supply condition of the weak oxidant so that is equal to or greater than a first threshold value.

  (3) Moreover, this invention is a paper manufacturing apparatus as described in (2) whose said 1st threshold value is a predetermined value of -250 mV or more.

  (4) In the present invention, the sterilizing agent is a bonded chlorine, which is a reaction product of hypochlorite and one or more compounds selected from the group consisting of ammonium salts, amines, amides and imides. The paper manufacturing apparatus in any one of (1) to (3) containing a compound.

  (5) Further, the present invention provides a first solution for water contained in a paper manufacturing unit to which at least one selected from the group consisting of the treated water, the scum and the sludge is supplied by the treated water supply unit. A second redox potential measuring unit that measures the redox potential of 2 and a bactericide that controls the supply conditions of the bactericide so that a measurement result of the second redox potential measuring unit is equal to or greater than a second threshold value. The paper manufacturing apparatus according to any one of (1) to (4), further including a control unit.

  (6) Moreover, this invention is a paper manufacturing apparatus as described in (5) whose said 2nd threshold value is predetermined value of -250 mV or more.

  (7) Further, the present invention provides an aqueous redox solution for at least one selected from the group consisting of treated water, scum, and sludge generated by treating waste water from a paper manufacturing department that produces paper from raw materials. Treated with a weak oxidizing agent whose potential is lower than the redox potential of an aqueous solution of sodium hypochlorite, and supplied with the weak oxidizing agent treated water treated with the weak oxidizing agent in one or more paper production departments A wastewater treatment method for supplying a disinfectant to at least one of the paper manufacturing departments.

  According to the present invention, the deodorizing property is further enhanced, the corrosion of the paper manufacturing apparatus is suppressed, and the cost can be reduced.

It is a block diagram for demonstrating schematic structure of the paper manufacturing apparatus 1 which concerns on this embodiment.

  Hereinafter, although embodiment of this invention is described, this embodiment does not limit this invention.

<Paper manufacturing apparatus 1>
FIG. 1 shows a schematic configuration of a paper manufacturing apparatus 1 according to an embodiment of the present invention. The paper manufacturing apparatus 1 includes a wastewater treatment unit 30 for treating water drained from a paper production unit 10 for producing paper from raw materials through a drainage unit 20, treated water treated by the wastewater treatment unit 30, At least one selected from the group consisting of scum present in the wastewater treatment unit and sludge present in the wastewater treatment unit (hereinafter also referred to as “treated water”) is the same paper production unit as the paper production unit 10 10 or other treated water supply unit 40 to be supplied to the paper manufacturing unit 10 'and the treated water in the wastewater treatment unit 30 or the treated water supply unit 40, the redox potential of the aqueous solution is sodium hypochlorite. Paper to which treated water or the like is supplied by the treated water supply unit 40 among the weak oxidant supply unit 50 that supplies a weak oxidant smaller than the redox potential of the aqueous solution and the one or more paper manufacturing units 10 and 10 ′. Kill at least one of the manufacturing departments 10 and 10 ' And a sterilizing agent supply unit 60 for supplying the agent.

[Paper Manufacturing Department 10]
The paper manufacturing unit 10 has a function of manufacturing paper from wood, used paper, and the like as raw materials. The configuration of the paper manufacturing unit 10 is not particularly limited, and a general configuration is sufficient. For example, the paper manufacturing unit 10 includes a pulp manufacturing unit 11 that manufactures pulp from raw materials, a preparation / papermaking unit 12 that forms and makes pulp manufactured by the pulp manufacturing unit 11, and A white water recovery unit 13 for recovering white water generated in the process.

[Pulp Manufacturing Department 11]
The pulp manufacturing unit 11 has a function of manufacturing pulp from raw materials and supplying the pulp to the preparation / papermaking unit 12. As an example, the pulp manufacturing unit 11 is supplied from a used paper pulper 111 that disaggregates used paper to produce used paper pulp, a broke tank 112 that contains broke pulp obtained by pulping waste paper, and a used paper pulper 111 and a broke tank 112. Mixing chest 113 for mixing raw materials, machine chest 114 for adding papermaking chemicals such as a sticker to the mixed raw materials mixed in mixing chest 113 to make pulp, and seed box for storing pulp sent from machine chest 114 115.

[Preparation / papermaking section 12]
The preparation / papermaking unit 12 has a function of preparing and papermaking the pulp manufactured by the pulp manufacturing unit 11. As an example, the preparation / papermaking unit 12 includes a pump 121 that sequentially transfers the pulp contained in the seed box 115 to the screen 122 and the cleaner 123 together with white water, and the screen 122 and the cleaner 123 that remove foreign matters contained in the pulp. And an inlet 124 for supplying pulp to the wire of the wire part 125 at an appropriate concentration, supply speed and supply angle, a wire part 125 and a press part 126 for dewatering the pulp, and a pulp in the wire part 125 and the press part 126 And a white water silo 127 that receives water dehydrated from the white water as white water. Part of the white water received by the white water silo 127 is supplied to the pump 121, and the rest is supplied to the collection unit 13.

[Recovery unit 13]
The collection unit 13 has a function of collecting white water supplied from the preparation / papermaking unit 12. As an example, the recovery unit 13 includes a seal pit 131 that transfers white water supplied from the preparation / papermaking unit 12 to the recovery device 132, a recovery device 132 that filters white water and recovers it as recovered water, and the recovery device. And a recovered water tank 133 for recovering the recovered water recovered at 132. A part of the recovered water is further filtered and reused by being returned to the waste paper pulper 111 or the broke tank 112. The remaining recovered water is transferred to the drainage unit 20 and then supplied to the drainage treatment unit 30.

[Drainage 20]
Following the description of the paper manufacturing unit 10, the drainage unit 20 will be described. The drainage unit 20 has a function of draining a part of the collected water stored in the collected water tank 133.

[Wastewater treatment unit 30]
The drainage treatment unit 30 has a function of treating the water drained from the drainage unit 20. The waste water treatment unit 30 includes a tank for processing by a sedimentation method, a pressurized flotation method, an activated sludge method, and the like, a storage unit for sludge and scum generated in the tank, a storage unit for treated water, and the like. “Scum” refers to a surface of microorganisms, fungi, suspended solids, fibers and the like.

  Although not essential, it is preferable that the waste water treatment unit 30 includes the off-flavor parameter measurement unit 31 that measures a parameter related to off-flavor substances in order to appropriately control the supply conditions of the weak oxidant in the weak oxidant control unit 51. Details of the off-flavor parameter measuring unit 31 will be described later.

[Treatment water supply unit 40]
The treated water supply unit 40 is the same as the paper manufacturing unit 10 described above for the scum present in the wastewater treatment unit 30 and the sludge present in the wastewater treatment unit 30 in addition to the treated water treated in the wastewater treatment unit 30. The paper supply unit 10 or another paper manufacture unit 10 '. In the present embodiment, the water is circulated between the paper manufacturing unit 10 and the waste water treatment unit 30, but is not limited thereto. The waste water from the paper manufacturing unit 10 may be processed by the waste water processing unit 30, and the treated water or the like may be supplied in series to another paper manufacturing unit 10 ′ via the treated water supply unit 40.

[Weak oxidant supply unit 50]
The weak oxidant supply unit 50 has an aqueous redox potential of sodium hypochlorite with respect to at least one selected from the group consisting of treated water, scum and sludge in the wastewater treatment unit 30 or the treated water supply unit 40. It has a function of supplying a weak oxidant smaller than the redox potential of the aqueous solution. In FIG. 1, the weak oxidant supply unit 50 is configured to supply a weak oxidant to at least one selected from the group consisting of treated water, scum and sludge in the wastewater treatment unit 30. The embodiment is not limited to this, and the weak oxidant supply unit 50 may be configured to supply a weak oxidant to the treated water or the like in the treated water supply unit 40.

[Weak oxidizing agent]
In the present specification, “weak oxidant” refers to an oxidant whose redox potential of an aqueous solution is lower than the redox potential of an aqueous solution of sodium hypochlorite. At this time, it is assumed that the concentration of the aqueous solution of the weak oxidizing agent is equal to the concentration of the aqueous solution of sodium hypochlorite. When the redox potential of the aqueous solution is higher than the redox potential of the aqueous sodium hypochlorite solution, the oxidizing agent reacts with starch remaining inside the wastewater treatment unit 30 or the like, organic matter contained in sludge and scum, etc. , Disassemble. For this reason, in order to decompose sulfides, hydrogen sulfide, etc., a large amount of oxidant is required, and unless a large amount of oxidant is supplied to the waste water treatment unit 30, generation of hydrogen sulfide may not be suitably suppressed. This is not preferable.

  The redox potential of the aqueous solution of the weak oxidizer is not particularly limited as long as it is lower than the redox potential of the aqueous solution of sodium hypochlorite, but the generation of hydrogen sulfide can be continuously suppressed with a small supply amount. Therefore, the redox potential of the aqueous solution of the weak oxidant is preferably 500 mV or less, and 400 mV or less, under the conditions of a concentration of 100 mg / L, pH 7, 25 ° C. (pure water, 10 mmol / L pH 7 phosphate buffer added). It is more preferable that

Specific examples of weak oxidizing agents include 2-bromo-2-nitropropane-1,3-diol (BNP), 2,2-dibromo-2-nitro-1-ethanol (DBNE), and 2,2-dibromo-3. -Nitrilopropionamide (DBNPA), hydrogen peroxide, chlorite, chlorosulfamate or peracetic acid. For reference, the properties of these weak oxidants are shown in Table 1. Among these, as mentioned in the examples, the weak oxidizing agent is preferably 2-bromo-2-nitropropane-1,3-diol, hydrogen peroxide, or chlorite. The appropriate weak oxidant varies depending on the organic substance, the reducing substance, the type of bacteria, etc. contained in the target water, and may be appropriately selected depending on the application.

  In addition, the kind of weak oxidizing agent may be used individually by 1 type, and may use multiple types together.

[Weak Oxidant Control Unit 51]
Although not an essential aspect, the weak oxidant supply unit 50 preferably includes a weak oxidant control unit 51 that controls the supply conditions of the weak oxidant in the weak oxidant supply unit 50. In the present specification, the “weak oxidant supply condition” refers to an addition amount per unit time, an addition time, an addition frequency, a place where addition is performed, or the like.

  The supply condition of the weak oxidant may be determined based on a parameter relating to a substance that can generate a bad odor. Parameters relating to substances that can cause off-flavors include measured values of redox potential of water, dissolved sulfide concentration in water, hydrogen sulfide concentration in air, and the like. As for these parameters, any one parameter may be used, or two or more parameters may be used in combination. When one parameter is used, it is preferable because deodorization can be achieved with a simpler system. When two or more parameters are combined, it is preferable because the supply conditions can be comprehensively studied and the supply conditions of the weak oxidant can be estimated more accurately.

  The method for determining the supply conditions of the weak oxidant is not particularly limited, but in order to prevent the organic acid-producing microorganisms and sulfate-reducing bacteria from breeding due to the reduction of the oxidation-reduction potential, the parameter measurement unit 31 described later is used. It is preferable to control the supply condition of the weak oxidant so that the measurement result in the above becomes an arbitrary threshold value or more. Hereinafter, based on the example of the oxidation-reduction potential, a method for controlling the supply condition of the weak oxidant will be described. Here, the threshold for the measurement result of the oxidation-reduction potential in the first oxidation-reduction potential measurement unit described later is referred to as a “first threshold”.

  Although the first threshold value is not particularly limited, the first threshold value is preferably set so that the sulfate-reducing bacteria can reduce the sulfate ion and suitably suppress the generation of hydrogen sulfide that can cause a strange odor. The threshold is preferably −250 mV or more, more preferably −200 mV or more, and further preferably −100 mV or more. In particular, not only the growth of sulfate-reducing bacteria but also the growth of organic acid-producing microorganisms can be suppressed, and not only hydrogen sulfide but also the production of organic acids can be suitably suppressed. Therefore, the first threshold value is 0 mV or more. Is particularly preferred.

  The upper limit of the first threshold is not particularly limited, but the first threshold is 300 mV or less in order to suppress an increase in the cost of the bactericide and the risk of environmental burden due to excessive addition of a weak oxidizing agent. It is preferable that it is 200 mV or less.

[Odor-odor parameter measurement unit 31]
Here, the description of the waste water treatment unit 30 is once returned. Although not essential, in order to suitably control the supply conditions of the weak oxidant in the weak oxidant control unit 41, the waste water treatment unit 30 preferably includes a odor parameter measurement unit 31 that measures a parameter related to a odor substance. In order to distinguish the odor parameter measurement unit 31 and the odor parameter measurement unit 70, the odor parameter measurement unit 31 is also referred to as a “first odor parameter measurement unit 31”, and the odor parameter measurement unit 70 is referred to as a “second odor parameter measurement unit 31. 70 ".

  The parameter measured by the first parameter measurement unit 31 may be used for control of the weak oxidant supply condition in the weak oxidant control unit 51. Examples of the first parameter measurement unit 31 include a first redox potential measurement unit, a first dissolved sulfide concentration measurement unit, and a first hydrogen sulfide concentration measurement unit. Hereinafter, these three types of parameter measurement units 31 will be described.

(First redox potential measurement unit)
The first oxidation-reduction potential measurement unit has a function of measuring the oxidation-reduction potential of water in the wastewater treatment unit 30 and / or the resupply unit 50. The installation location of the first oxidation-reduction potential measurement unit is not particularly limited, but in order to be able to respond quickly to changes in water due to the growth of microorganisms and fungi, the propagation of organic acid-producing microorganisms and sulfate-reducing bacteria It is preferable to make it easy to occur. The first oxidation-reduction potential measurement unit may directly measure the oxidation-reduction potential of water in the wastewater treatment unit 30, or may measure the oxidation-reduction potential of water collected from the wastewater treatment unit 30. In addition, when collecting water from the waste water treatment part 30, you may perform processes, such as filtration.

(First dissolved sulfide concentration measurement unit)
The first dissolved sulfide concentration measurement unit has a function of measuring the dissolved sulfide concentration of water in the wastewater treatment unit 30 and / or the resupply unit 50. The location of the first dissolved sulfide concentration measurement unit is not particularly limited, but in order to be able to respond quickly to changes in water due to the growth of microorganisms and fungi, the propagation of organic acid-producing microorganisms and sulfate-reducing bacteria It is preferable to make it a place where the occurrence of a tendency to occur. The first dissolved sulfide concentration measurement unit may directly measure the dissolved sulfide concentration of the water in the wastewater treatment unit 30 parts, or measure the dissolved sulfide concentration of the water collected from the wastewater treatment unit 30. Also good. In addition, when collecting water from the waste water treatment part 30, you may perform processes, such as filtration.

(First hydrogen sulfide concentration measurement unit)
The first hydrogen sulfide concentration measurement unit has a function of measuring the hydrogen sulfide concentration in the air near the wastewater treatment unit 30 and / or the resupply unit 50. The location where the hydrogen sulfide concentration measurement unit is installed is not particularly limited, but organic acid-producing microorganisms and sulfate-reducing bacteria can be propagated in order to respond quickly to the generation of hydrogen sulfide due to the propagation of sulfate-reducing bacteria. It is preferable to make it near a place where it easily occurs.

[Bactericidal agent supply unit 60, odor parameter measurement unit 70]
The paper manufacturing apparatus 1 supplies a sterilizing agent to at least one of the one or more paper manufacturing units 10, 10 ′, etc., to which the treated water is supplied by the processing water supply unit 40, etc. It is preferable to further include a bactericidal agent supply unit 60 to be supplied and a different odor parameter measurement unit 70 that measures a value related to a different odor parameter with respect to water sent from the bactericide supply unit 60.

  In the present invention, in addition to suppressing the amount of hydrogen sulfide generated in the paper manufacturing apparatus 1 by supplying the weak oxidant in the weak oxidant supply section 50, the disinfectant supply section 14 is provided in the paper manufacturing apparatus 1. It is significant that the deodorizing property is further improved, the corrosion of the paper manufacturing apparatus 1 is suppressed, and the cost is reduced.

  The location of the disinfectant supply unit 60 is not particularly limited, but in order to efficiently circulate the disinfectant inside the paper manufacturing unit 10 or 10 ', the disinfectant supply unit 60 is connected to the white water silo 127, It is preferably provided at a location communicating with the recovered water tank 133. In addition, it is preferable to provide the disinfectant supply unit 60 at a place where the residence time is relatively long and the spoilage is likely to proceed, that is, a place communicating with the waste paper pulper 111, the broke tank 112, and the mixing chest 113.

(Fungicide)
An example of the bactericidal agent is a combined chlorine type bactericidal agent. A combined chlorine-type disinfectant is obtained by reacting a chlorine donor that releases free chlorine with either ammonia, an ammonium salt, or an organic nitrogen compound under appropriate conditions. The chlorine donor is not particularly limited, but sodium hypochlorite is preferable. Further, the ammonium salt is not particularly limited, but ammonium halide such as ammonium bromide, ammonium chloride, ammonium sulfate, ammonium nitrate and the like are preferable, and the organic amine is preferably sulfamic acid, urea and the like. These can prevent the anaerobic state in which organic acid-producing microorganisms and sulfate-reducing bacteria can be active by increasing the redox potential of the circulating water of the paper manufacturing unit 10 due to its high oxidizing power. .

  Moreover, the compound which produces | generates hypochlorous acid and / or hypobromite in water as another example of a disinfectant is mentioned. For example, chlorine, chlorine dioxide, advanced bleaching powder, hypochlorous acid, sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, ammonium hypochlorite, magnesium hypochlorite, hypobromite, Sodium hypobromite, potassium hypobromite, calcium hypobromite, ammonium hypobromite, magnesium hypobromite, chlorinated and / or brominated hydantoins, chlorinated and / or brominated isocyanuric acid and The sodium salt, potassium salt, etc. are mentioned. These can also prevent the anaerobic state in which the organic acid-producing microorganisms and sulfate-reducing bacteria can be active by raising the oxidation-reduction potential of the circulating water of the paper production unit 10, 10 ′ by its oxidizing power.

  And an organic germicide is mentioned as another example of a germicide. Examples of organic fungicides include 2-bromo-2-nitropropane-1,3-diol, 2,2-dibromo-2-nitro-1-ethanol, 2,2-dibromo-3-nitrilopropionamide, 1, 4-bis (bromoacetoxy) -2-butene and the like can be mentioned.

  In addition, the kind of disinfectant may be used individually by 1 type, and may use multiple types together.

(Bactericide control unit 61)
Although not essential, the bactericide supply unit 60 preferably includes a bactericide control unit 61 that controls the supply conditions of the bactericide in the bactericide supply unit 14. In the present specification, the “bactericide supply condition” refers to the amount of addition per unit time, the time for addition, the frequency of addition, the location for addition, and the like.

  The supply condition of the bactericide may be determined based on a parameter related to the off-flavor substance. Examples of parameters relating to off-flavors include water redox potential, dissolved sulfide concentration in water, and measured values of hydrogen sulfide concentration in air. As for these parameters, any one parameter may be used, or two or more parameters may be used in combination. When one parameter is used, it is preferable because deodorization can be achieved with a simpler system. When two or more parameters are combined, it is preferable because the supply conditions can be comprehensively studied and the supply conditions of the weak oxidant can be estimated more accurately.

  The method for determining the supply conditions of the bactericide is not particularly limited, but in order to prevent the organic acid-producing microorganisms and sulfate-reducing bacteria from breeding due to the reduction of the oxidation-reduction potential, the parameter measurement unit 15 described later is used. It is preferable to control the supply conditions of the bactericidal agent so that the measurement result at is equal to or greater than the second threshold value.

  Although the second threshold is not particularly limited, the second threshold is preferably used in order to suitably suppress the sulfate-reducing bacteria from reducing sulfate ions and generating hydrogen sulfide that can cause a strange odor. The threshold is preferably −250 mV or more, more preferably −200 mV or more, and further preferably −100 mV or more. In particular, not only the growth of sulfate-reducing bacteria but also the growth of organic acid-producing microorganisms can be suppressed, and not only hydrogen sulfide but also the generation of organic acids can be suitably suppressed. Is particularly preferred.

  The upper limit of the second threshold value is not particularly limited, but the second threshold value is 500 mV or less in order to suppress an increase in the cost of the germicide and the risk of environmental burden due to excessive addition of the germicide. Is preferable, and it is more preferable that it is 400 mV or less.

[Odor-odor parameter measuring unit 70]
The off-flavor parameter measuring unit 70 has a function of measuring a value related to off-flavor parameters with respect to water sent from the bactericide supply unit 60. The measured value in the off-flavor parameter measuring unit 70 may be used for controlling the supply conditions of the bactericide in the bactericide control unit 61. The off-flavor parameter measurement unit 70 includes one or more selected from an oxidation-reduction potential measurement unit, a dissolved sulfide concentration measurement unit, a hydrogen sulfide concentration measurement unit in the air, and the like.

(Redox potential measurement unit)
The oxidation-reduction potential measuring unit has a function of measuring the oxidation-reduction potential of water in the paper manufacturing units 10, 10 ′. The installation location of the oxidation-reduction potential measuring device is not particularly limited, but the organic acid-producing microorganisms and sulfate-reducing bacteria propagate in order to respond quickly to changes in water caused by the propagation of microorganisms and bacteria. It is preferable to make it an easy place. Further, the oxidation-reduction potential measuring unit may directly measure the water of the paper manufacturing unit 10, 10 ′, or may measure the water collected from the paper manufacturing unit 10, 10 ′. In addition, when collecting water from paper manufacturing departments 10 and 10 ', processing, such as filtration, may be performed.

(Dissolved sulfide concentration measurement unit)
The dissolved sulfide concentration measuring unit has a function of measuring the dissolved sulfide concentration of water in the paper manufacturing unit 10, 10 ′. The location of the device for measuring the concentration of dissolved sulfide is not particularly limited, but organic acid-producing microorganisms and sulfate-reducing bacteria are propagated in order to respond quickly to changes in water caused by the propagation of microorganisms and fungi. It is preferable to make it an easy place. The dissolved sulfide concentration measuring unit may directly measure the dissolved sulfide concentration of water in the paper manufacturing unit 10 or 10 ′, or measure the dissolved sulfide concentration of water collected from the paper manufacturing unit 10. Also good. In addition, when collecting water from paper manufacturing departments 10 and 10 ', processing, such as filtration, may be performed.

(Hydrogen sulfide concentration measurement unit)
The hydrogen sulfide concentration measuring unit has a function of measuring the hydrogen sulfide concentration in the air in the vicinity of the paper manufacturing unit 10, 10 ′. The installation location of the hydrogen sulfide concentration measuring device is not particularly limited, but in order to be able to respond quickly to the generation of hydrogen sulfide due to the propagation of sulfate-reducing bacteria, it is located near the place where sulfate-reducing bacteria are likely to propagate. It is preferable to do this.

<Wastewater treatment method>
Next, the waste water treatment method according to this embodiment will be described. The waste water treatment method according to the present embodiment is an aqueous solution for at least one selected from the group consisting of treated water, scum, and sludge generated by treating waste water from the paper manufacturing unit 10 that produces paper from raw materials. A weak oxidant treated with a weak oxidant in one or more of the paper manufacturing units 10, 10 ′, etc. while being treated with a weak oxidant whose redox potential is lower than the redox potential of an aqueous solution of sodium hypochlorite. Including a step of supplying a disinfectant to at least one of the paper manufacturing units 10 and 10 ′ to which treated water is supplied.

  The drainage is not particularly limited as long as it is water drained from an apparatus for producing paper from raw materials, and is limited to whether or not this apparatus has the same configuration as the paper production units 10 and 10 'of FIG. It is not something. In addition, the waste water may have a large solid component content such as sludge and scum, or may have a small solid component content such as treated recovered water. Moreover, after discharge | emission, further processes, such as a chemical | medical agent process, may be performed.

  The method for supplying the weak oxidant is not particularly limited, and may be performed intermittently or continuously. In addition to providing the weak oxidant supply device 50 with the weak oxidant control unit 51 for controlling the supply condition of the weak oxidant, the supply condition is provided with the first off-flavor parameter measuring unit 31 in the waste water treatment unit 30. The weak oxidant control unit 51 may be controlled based on the measurement results of the redox potential, dissolved sulfide concentration, hydrogen sulfide concentration measurement unit and the like in the first off-flavor parameter measurement unit 31.

  The method for determining the supply condition of the weak oxidant is not particularly limited. For example, when the oxidation-reduction potential measurement unit is used as the first odor parameter measurement unit 31, the measurement result is equal to or greater than a specific threshold value. It is preferable to control the supply conditions of the weak oxidant. More specifically, the supply is preferably started when the oxidation-reduction potential is lower than the first threshold, and the supply is preferably performed so that the oxidation-reduction potential exceeds the first threshold. This is because it is possible to prevent the oxidation-reduction potential from decreasing and the organic acid-producing microorganisms and sulfate-reducing bacteria to proliferate. Further, the weak oxidizing agent may be added manually or automatically.

  The first threshold value is preferably −250 mV or more, and −200 mV so that the sulfate-reducing bacteria can suitably suppress the generation of hydrogen sulfide that can reduce sulfate ions and cause off-flavors. More preferably, it is -100 mV or more. In particular, not only the growth of sulfate-reducing bacteria but also the growth of organic acid-producing microorganisms can be suppressed, and not only hydrogen sulfide but also the production of organic acids can be suitably suppressed. Therefore, the first threshold value is 0 mV or more. Is particularly preferred.

  The upper limit of the first threshold is not particularly limited, but the first threshold is 300 mV or less in order to suppress an increase in the cost of the bactericide and the risk of environmental burden due to excessive addition of a weak oxidizing agent. It is preferable that it is 200 mV or less.

  Regardless of the type of weak oxidant, by setting the threshold to a value not less than the above lower limit and not more than the above upper limit, sulfate-reducing bacteria and organic acid-producing microorganisms with the minimum supply amount according to the weak oxidant Is preferable from the viewpoint of cost and environmental load.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<Test 1> Examination of deodorizing effect of scum by oxidizing agent

(Sample preparation)
After the wastewater contained in the drainage section 20 in the paper manufacturing apparatus 1 shown in FIG. 1 is solid-liquid separated by a pressurized floating separator Supercell (manufactured by Klofter), the wastewater is stored in a drainage pit for 1 hour to obtain a scum. It was. The concentration of hydrogen sulfide contained in the scum was measured and found to be about 10 ppm.

  Subsequently, 200 ml of scum was placed in a container having a capacity of 500 ml, the oxidizing agent shown in Table 2 was added so as to have the concentration shown in Table 1, and stirring was performed, thereby obtaining samples according to Examples and Comparative Examples. It was.

[Evaluation]
Using an oxidation-reduction potential electrode (product name: TPX999Si, manufactured by Toko Chemical Co., Ltd.), the oxidation-reduction potential of the samples according to Examples and Comparative Examples was 5 minutes after the addition of the oxidant and 30 minutes after the addition of the oxidant. It measured about each 90 minutes after addition. The results are shown in Table 3.

  When 2-bromo-2-nitropropane-1,3-diol, hydrogen peroxide, or sodium chlorite is added to the scum sample, it changes at a higher redox potential than when sodium hypochlorite is added. It was confirmed (Examples 1-3). Further, in Examples 1 to 3, it was confirmed that samples having a higher weak oxidant concentration had a higher redox potential at any time when compared with each type of weak oxidant. Although the optimum amount of weak oxidizer varies depending on the oxidizing power of the weak oxidizer and the environment of the water to be added, etc., the threshold value of the oxidation-reduction potential of the water contained in the wastewater treatment unit is set in advance, and the oxidation is close to this threshold By controlling the amount of weak oxidant added so that the reduction potential changes, the amount of weak oxidant used can be kept as small as possible regardless of the type of weak oxidant. Thereby, it is possible to reduce the corrosion of the paper manufacturing apparatus, cost reduction and environmental load.

  Among the weak oxidizers, 2-bromo-2-nitropropane-1,3-diol and hydrogen peroxide take some time from the addition of the weak oxidizer to the scum sample until the redox potential of the scum sample increases. In short, a high redox potential can be maintained for a longer time. On the other hand, sodium chlorite can increase the redox potential of a scum sample in a relatively short time after adding a weak oxidant to the scum sample, but the weak oxidant is 2-bromo-2-nitropropane. Compared with the case of -1,3-diol or hydrogen peroxide, the reduction of the redox potential of the scum sample starts in a short time. The difference in the redox potential of the scum sample over time due to the type of weak oxidant is presumed to be due to the difference in the oxidizing power of the weak oxidant.

<Test 2> Examination of deodorizing effect of scum by two-step addition of oxidizing agent and disinfectant

(Sample preparation)
First, sample preparation methods according to Examples 4 to 6 and Comparative Example 3 will be described. First, the same operations as in Examples 1 to 3 and Comparative Example 1 were performed. Samples obtained by the same operations as in Examples 1 to 3 and Comparative Example 1 are referred to as samples after addition of an oxidizing agent. Subsequently, the sample after the addition of the oxidant is allowed to stand at 40 ° C. for 2 hours, and the oxidant after the standing is applied to the 3% pulp slurry of the corrugated cardboard produced using the paper manufacturing apparatus 1 illustrated in FIG. After the addition, the sample was mixed and stirred at a rate of 20% (w / w). Then, a combined chlorine-type disinfectant (2% (w / w) with pure water) obtained by mixing and reacting ammonium bromide and sodium hypochlorite in a molar ratio of 1: 1 to the sample after addition of the oxidizing agent after stirring. Bond obtained by mixing an adjusted aqueous solution of ammonium bromide with an aqueous sodium hypochlorite solution prepared by adjusting the effective chlorine concentration based on Cl ₂ to 5000 mg / L with pure water while stirring at a weight ratio of 1: 1. (Chlorine-type disinfectant) was added and allowed to stand at 40 ° C. for 1 day. By doing in this way, the sample after the oxidizing agent and disinfectant addition which concern on Examples 4-6 and the comparative example 3 was obtained.

  Next, a sample preparation method according to Comparative Example 4 will be described. First, the same operation as in Comparative Example 2 was performed. A sample obtained by the same operation as in Comparative Example 2 is referred to as a pretreatment sample. Subsequently, the pretreated sample is allowed to stand at 40 ° C. for 2 hours, and the pretreated sample after standing is applied to the 3% pulp slurry of the corrugated cardboard produced using the paper manufacturing apparatus 1 illustrated in FIG. The mixture was mixed and stirred at a rate of 20% (w / w). And the pre-processing sample after stirring was left still at 40 degreeC for 1 day. By doing in this way, the sample concerning the comparative example 4 was obtained.

[Evaluation]
The oxidation-reduction potentials of the samples according to Examples 4 to 6 and Comparative Examples 3 to 4 were measured by the same method as in Test 1. Moreover, the hydrogen sulfide density | concentration of the sample which concerns on Examples 4-6 and Comparative Examples 3-4 was measured using the detection tube (Product name: No.4LL, the product made from GASTEC). The results are shown in Table 5.

  When the oxidizing agent is a weak oxidizing agent such as 2-bromo-2-nitropropane-1,3-diol, hydrogen peroxide or sodium chlorite, the redox potential of the sample is a positive value, It was confirmed that generation | occurrence | production can be prevented suitably (Examples 4-6). In particular, when the weak oxidant is 2-bromo-2-nitropropane-1,3-diol or hydrogen peroxide, the oxidation-reduction potential is sufficiently high even if the addition amount of the weak oxidant is small, and hydrogen sulfide is generated. (Examples 4 and 5) were confirmed.

  On the other hand, when the oxidizing agent was sodium hypochlorite, the redox potential of the sample was less than −250 mV, and no suitable hydrogen sulfide generation preventing effect was observed as in Examples 1 to 3 (Comparative Example 3). In particular, when the amount of sodium hypochlorite added is small, the value of the oxidation-reduction potential is almost as low as that in the case where no oxidizing agent was added (Comparative Example 4) (Comparative Examples 3-1, 3-2).

  From the above results, it was confirmed that by adding a weak oxidizing agent to a sample containing a large amount of organic matter such as scum, the effect of the bactericide added thereafter can be sufficiently exhibited.

  In addition, in Examples 4 to 6, it was confirmed that samples having higher weak oxidant concentration and bactericide concentration had higher redox potential when compared with each type of weak oxidant. Although the optimum addition amounts of the weak oxidizer and the bactericidal agent vary depending on the oxidizing power of the weak oxidizer and the bactericidal agent, the environment of water to which the weak oxidizer and the bactericidal agent are added, the first threshold value and the second threshold value described above. A threshold value is determined in advance, and the weak oxidizer and the sterilizer are controlled by controlling the addition amount of the weak oxidizer and the sterilizer so that the redox potential of the circulating water changes at values close to the first threshold value and the second threshold value. Regardless of the type of agent, the amount of weak oxidizing agent and fungicide used can be minimized. Thereby, it is possible to reduce the corrosion of the paper manufacturing apparatus, cost reduction and environmental load.

DESCRIPTION OF SYMBOLS 1 Paper manufacturing apparatus 10 Paper manufacturing part 20 Drainage part 30 Wastewater treatment part 40 Supply part etc. of treated water 50 Weak oxidizing agent supply part 60 Bactericidal agent supply part

Claims (6)

A wastewater treatment unit for treating water drained from a paper production unit for producing paper from raw materials;
At least one or more selected from the group consisting of treated water treated in the wastewater treatment unit, scum present in the wastewater treatment unit, and sludge present in the wastewater treatment unit is the same as the paper manufacturing unit or A treated water supply section for supplying to other paper manufacturing departments;
For at least one selected from the group consisting of the treated water, the scum and the sludge in the wastewater treatment section or the treated water supply section, the redox potential of the aqueous solution of sodium hypochlorite is the redox potential of the aqueous solution. A weak oxidant supply unit for supplying a weak oxidant smaller than the electric potential;
Among the one or more paper manufacturing units, a disinfectant is applied to at least one of the paper manufacturing units to which at least one selected from the group consisting of the treated water, the scum and the sludge is supplied by the treated water supply unit. A disinfectant supply unit for supplying ,
The paper manufacturing apparatus , wherein the disinfectant includes a combined chlorine compound that is a reaction product of hypochlorite and one or more compounds selected from the group consisting of ammonium salts, amines, amides, and imides . A first oxidation-reduction potential measuring unit that measures a first oxidation-reduction potential for water contained in the wastewater treatment unit;
The paper manufacture according to claim 1, further comprising: a weak oxidant control unit that controls a supply condition of the weak oxidant so that a measurement result in the first redox potential measurement unit is equal to or higher than a first threshold value. apparatus.   The paper manufacturing apparatus according to claim 2, wherein the first threshold value is a predetermined value of -250 mV or more. A second oxidation-reduction potential is measured for water contained in a paper manufacturing unit to which at least one selected from the group consisting of the treated water, the scum and the sludge is supplied by the treated water supply unit. A redox potential measurement unit;
The sterilizing agent control part which controls the supply conditions of the said sterilizing agent so that the measurement result in the said 2nd oxidation-reduction potential measurement part may become more than a 2nd threshold value is provided in any one of Claim 1 to 3 Paper manufacturing equipment. The paper manufacturing apparatus according to claim 4 , wherein the second threshold is a predetermined value of -250 mV or more. An aqueous solution in which the redox potential of the aqueous solution is sodium hypochlorite with respect to at least one selected from the group consisting of treated water, scum and sludge generated by treating waste water from the paper production department that produces paper from raw materials And at least one of the paper manufacturing units to which the weak oxidizing agent treated water treated with the weak oxidizing agent is supplied among the one or more paper manufacturing units. Supplying a bactericidal agent ,
A wastewater treatment method , wherein the disinfectant contains a combined chlorine compound that is a reaction product of hypochlorite and one or more compounds selected from the group consisting of ammonium salts, amines, amides, and imides .

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