JP6572582B2 - Water treatment method and water treatment system - Google Patents

Description

  The present invention relates to a water treatment method and a water treatment system. More specifically, the present invention relates to a water treatment method and a water treatment system for removing formaldehyde from water containing formaldehyde discharged from a retort apparatus or the like.

  Conventionally, wastewater discharged from factories or the like may contain formaldehyde. For example, the cooling effluent after a beverage can or a food can is subjected to pressure and heat sterilization processing by a retort apparatus contains a trace amount of formaldehyde derived from the paint on the surface of the can. A large amount of tap water, which is more expensive than industrial water, is used for the retort device because of food hygiene requirements. Therefore, in order to reduce costs, it is required to make the cooling effluent reusable by removing formaldehyde.

  As a method for removing formaldehyde from water containing formaldehyde, a method is known in which hydroxymethanesulfonic acid is produced by adding a hydrogen sulfite ion source compound to water and reacting formaldehyde with hydrogen sulfite ions. The hydroxymethanesulfonic acid thus produced can be removed by a reverse osmosis (RO) membrane (see, for example, Patent Documents 1 to 4).

JP 2014-083521 A Japanese Patent No. 5348297 Japanese Patent No. 5527473 Japanese Patent Publication No. 58-27996

  By the way, when removing formaldehyde by the above-mentioned method, in order to remove as much formaldehyde as possible, many bisulfite ion source compounds are added to water. As described above, when the bisulfite ion source concentration is increased by adding a large amount of the bisulfite ion source compound, many bisulfite ions may permeate the reverse osmosis membrane, making it difficult to reuse water. .

  The present invention has been made in view of the above problems, and it is possible to efficiently remove formaldehyde from water containing formaldehyde, and to suppress the permeation of hydrogen sulfite ions through a reverse osmosis membrane. An object is to provide a processing system.

The present invention relates to a water treatment method for removing formaldehyde from water containing formaldehyde discharged from a sterilization treatment device, wherein the sterilization treatment device is a retort device, a pasteurization device or a container washing used in a food factory or a beverage factory. a device, wherein the water discharged from the sterilization apparatus, first the medicine adding bisulfite ions 1.8 times or less of the amount of substance more than 1 times the amount of substance of formaldehyde to be discharged from the sterilizing apparatus A first reaction step in which formaldehyde and bisulfite ions are reacted for 10 minutes or more after the first injection step, and water of the formaldehyde discharged from the sterilization apparatus in the water after the first reaction step. A second chemical injection step of adding bisulfite ions having a substance amount of 4 to 8.2 times the amount of the substance; After the chemical injection step, a second reaction step in which formaldehyde and bisulfite ions are reacted for 2 minutes or more, and hydroxymethanesulfonic acid ions generated by reacting formaldehyde with bisulfite ions from the water after the second reaction step And a removal step of removing water with a reverse osmosis membrane.

Further, the present invention is a water treatment system for removing formaldehyde from water containing formaldehyde discharged from a sterilization treatment device , wherein the sterilization treatment device is a retort device, a pasteurize device or a paste used in a food factory or a beverage factory. A container cleaning apparatus, and a water distribution line through which water containing formaldehyde discharged from the sterilization apparatus is distributed, and a hydrogen sulfite ion source that dissolves in water and generates bisulfite ions are supplied to the water distribution line On the secondary side of the first chemical injection part and the first chemical injection part, a second chemical injection part for supplying a hydrogen sulfite ion source to the water distribution line, and water distributed through the water distribution line are supplied. Removal of hydroxymethane sulfonate ion formed by reaction of formaldehyde and bisulfite ion from water by reverse osmosis membrane A first chemical injection control unit for controlling a supply amount of a bisulfite ion source from the first chemical injection unit to the water distribution line, and a bisulfite ion from the second chemical injection unit to the water distribution line A control unit having a second chemical injection control unit that controls a supply amount of the source, and the first chemical injection control unit is configured for the amount of formaldehyde discharged from the sterilization apparatus per unit time. And controlling the first chemical injection unit to supply a bisulfite ion source having a substance amount of 1 to 1.8 times per unit time to the water distribution line, the second chemical injection control unit, The bisulfite ion source is supplied to the water distribution line with a substance amount that is 4 times or more and 8.2 times or less per unit time with respect to the amount of formaldehyde discharged from the sterilization apparatus per unit time. Control the two drug injection parts, the second The pouring part is disposed at a position where the water circulation time from the first chemical pouring part to the second chemical pouring part is 10 minutes or more, and the removing means removes the removal from the second chemical pouring part. It is related with the water treatment system arrange | positioned in the position from which the distribution | circulation time of the water to a means will be 2 minutes or more.

  Moreover, it is preferable that the said removal means is arrange | positioned in the position from which the circulation time of the water from the said 2nd chemical injection part to the said removal means will be less than 5 minutes.

  The water distribution line further includes a first buffer tank disposed in the water distribution line, the water distribution line supplying the first buffer tank with water discharged from the sterilization apparatus, and the first buffer tank. A first circulation line that circulates water in one buffer tank; and a second circulation line that circulates water in the first buffer tank to the second drug injection part side, wherein the first drug injection part is The bisulfite ion source is preferably supplied to the first circulation line.

  According to the present invention, it is possible to provide a water treatment method and a water treatment system capable of efficiently removing formaldehyde from water containing formaldehyde and suppressing permeation of hydrogen sulfite ions through a reverse osmosis membrane.

It is a figure showing the whole water treatment system composition concerning one embodiment of the present invention. It is a figure which shows the structure of the removal means with which the water treatment system which concerns on the said embodiment is provided. It is a figure shown about the procedure of the water treatment method which concerns on one Embodiment of this invention. It is the graph which showed the relationship between the elapsed time from the 1st chemical injection, and the density | concentration of the produced | generated formaldehyde in the Example of this invention.

Hereinafter, preferred embodiments of a water treatment system according to the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a water treatment system 1 according to an embodiment of the present invention.
The water treatment system 1 removes formaldehyde from the water containing formaldehyde discharged from the sterilization treatment apparatus 100. Examples of the sterilization apparatus 100 include a retort apparatus, a paste rise apparatus, a container cleaning apparatus, and the like (hereinafter sometimes referred to as “retort apparatus etc.”) used in food factories and beverage factories. The water discharged | emitted from a retort apparatus etc. contains 1-5 mg / L formaldehyde, for example.

  As shown in FIG. 1, the water treatment system 1 is disposed in the water distribution line L1, the first buffer tank 10, the second buffer tank 20, and the removing means 30 disposed in the water distribution line L1, and the water distribution line L1. And a control unit 40 that controls various devices to be operated.

  The water distribution line L1 includes a first distribution line L11, a second distribution line L12, a third distribution line L13, a permeate water line L14, a concentrated water line L15, a first circulation line L16, and a second circulation line. L17. Details of connection of the lines constituting the water distribution line L1 will be described in each configuration. The “line” in the present specification is a general term for lines capable of flowing a fluid such as a flow path, a radial path, and a pipeline.

The first distribution line L11 has an upstream side connected to the sterilization apparatus 100 and a downstream side connected to the first buffer tank 10. The first distribution line L <b> 11 supplies water containing formaldehyde discharged from the sterilization apparatus 100 to the first buffer tank 10.
The 1st buffer tank 10 stores the water supplied from the 1st distribution line L11. The first buffer tank 10 is provided with a water level sensor 101 that detects the water level in the tank.

Here, the 1st distribution line L11 can be equipped with a required pre-processing apparatus (not shown). For example, the cooling effluent from the retort device has a high temperature of 60 ° C. or higher, and may contain suspended substances derived from the retort (contents attached to the outside of the container during filling). There is a concern that a reverse osmosis membrane, which will be described later, is deteriorated or blocked. Therefore, it is preferable to install a cooling device such as a heat exchanger or a cooling tower as a pretreatment device for removing heat from the cooling waste water. Moreover, it is preferable to install a turbidity device equipped with a microfiltration membrane or an ultrafiltration membrane as a pretreatment device for turbidizing cooling wastewater.
Therefore, “formaldehyde-containing water” in this application is intended not only for untreated water discharged from the sterilization treatment apparatus 100 but also for water that has been discharged from the sterilization treatment apparatus 100 and passed through a required pretreatment apparatus. To do.

The first circulation line L16 circulates part of the water in the first buffer tank 10. In the first circulation line L <b> 16, the first drug injection unit 11, the pH adjusting drug injection unit 12, and the circulation pump 13 are arranged.
The 1st chemical injection part 11 supplies the bisulfite ion source which melt | dissolves in water and produces | generates bisulfite ion to the 1st circulation line L16. The bisulfite ion source supplied from the first chemical injection section 11 is not particularly limited as long as it is dissolved in water to generate bisulfite ions. For example, bisulfite, pyrosulfite, dithionite Salts, sulfites and sulfites. Examples of the salt include alkali metal salts such as sodium salt and potassium salt. As the hydrogen sulfite ion source, it is preferable to use a hydrogen sulfite such as sodium hydrogen sulfite or potassium hydrogen sulfite because of its high handleability. In addition, sodium hydrogensulfite is marketed as an aqueous solution having a concentration of 35% or more, and this aqueous solution can be used as it is as a chemical solution for the first chemical injection part 11 and the second chemical injection part 21 described later.

The pH adjusting chemical injection unit 12 supplies the pH adjusting agent to the first circulation line L16 on the secondary side of the first chemical injection unit 11. Since the pH of water tends to decrease due to the hydrogen sulfite ion source supplied by the first chemical injection section 11 and the second chemical injection section described later, the pH adjustment chemical injection section 12 is alkaline such as sodium hydroxide. Supply substances.
Circulation pump 13 is arranged in the 1st circulation line L16, pressurizes the water supplied from the primary side, and sends it out to the secondary side.

The second distribution line L12 has an upstream side connected to the first buffer tank 10 and a downstream side connected to the second buffer tank 20. The second distribution line L12 distributes the water in the first buffer tank 10. In the second distribution line L12, the water supply pump 14 and the second chemical injection section 21 are arranged.
The feed water pump 14 is arrange | positioned at the 2nd distribution line L12, pressurizes the water supplied from a primary side, and sends it out to a secondary side.

The second chemical injection section 21 further supplies a bisulfite ion source to the second distribution line L12 on the secondary side of the water supply pump 14. The hydrogen sulfite ion source supplied from the second chemical injection section 21 to the second circulation line L12 may be the same as the hydrogen sulfate ion source supplied from the first chemical injection section 11 to the first circulation line L16. it can.
The second buffer tank 20 stores water supplied from the second distribution line L12. The second buffer tank 20 has a water level sensor 201 that detects the water level in the tank.

The third distribution line L13 has an upstream side connected to the second buffer tank 20 and a downstream side connected to the removing means 30. The third distribution line L13 distributes the water in the second buffer tank 20. A pressurizing pump 22 is disposed in the third distribution line L13.
The pressurizing pump 22 is disposed in the third distribution line L13, pressurizes water supplied from the primary side, and sends it to the secondary side.

  The removing means 30 separates the water (feed water) pressurized by the pressure pump 22 with a reverse osmosis (RO) membrane. The removing means 30 separates the supplied water into permeated water (treated water) that permeates the RO membrane and concentrated water that does not permeate the RO membrane. The RO membrane includes a nanofiltration membrane (NF membrane) having pores looser than those of a normal RO membrane. The configuration of the removing means 30 will be described in detail later.

The upstream side of the permeated water line L14 is connected to the removing unit 30, and the permeated water (treated water) that has passed through the RO membrane in the removing unit 30 is circulated.
The upstream side of the concentrated water line L15 is connected to the removing unit 30, and the concentrated water that has not passed through the RO membrane in the removing unit 30 is circulated.

The second circulation line L17 has an upstream side connected to the concentrated water line L15 and a downstream side connected to the second buffer tank 20. The second circulation line L17 circulates a part of the water flowing through the concentrated water line L15 to the second buffer tank 20 side.
In addition, among the structures demonstrated above, the 2nd buffer tank 20, the 2nd chemical injection part 21, the pressurization pump 22, the removal means 30, a part of the downstream of the 2nd distribution line L12, the 3rd distribution line L13, A part on the upstream side of the permeate line L14, a part on the upstream side of the concentrated water line L15, the first circulation line L16 and the second circulation line L17 constitute an RO membrane device.

The control unit 40 includes a first chemical injection control unit 41 and a second chemical injection control unit 42. The first chemical injection control unit 41 controls the supply amount of the bisulfite ion source from the first chemical injection unit 11 to the first circulation line L16 (water circulation line L1). The second chemical injection control unit 42 controls the supply amount of the bisulfite ion source from the second chemical injection unit 21 to the second distribution line L12 (water distribution line L1).
The water treatment system 1 includes a valve, a pump, a sensor, and the like in addition to the configuration described above.

  FIG. 2 is a diagram illustrating a configuration of the removing unit 30. As shown in FIG. 2, the removing means 30 includes a plurality (specifically eight) of first RO membrane modules 31 and a plurality (specifically six) of the first RO membrane modules 31, which is smaller than the number of first RO membrane modules 31. The second RO membrane module 32, the plurality of first module supply water lines L311, the plurality of first module permeate water lines L312, the plurality of first module concentrated water lines L313, the assembly line L33, and the plurality of second modules A supply water line L321, a plurality of second module permeate water lines L322, and a plurality of second module concentrated water lines L323 are provided.

The plurality of first module supply water lines L311 are arranged branched from the downstream side of the third distribution line L13. The plurality of first RO membrane modules 31 are each connected to the downstream side of the first module supply water line L311. The plurality of first RO membrane modules 31 each separates supply water supplied from the third distribution line L13 into permeated water and concentrated water by the RO membrane.
The plurality of first module permeate lines L312 are respectively connected to the first RO membrane module 31 on the upstream side and gather on the upstream side of the permeate line L14 on the downstream side. The plurality of first module permeated water lines L312 supplies permeated water that has passed through the RO membrane in the first RO membrane module 31 to the permeated water line L14.

  The plurality of first module concentrated water lines L313 are connected to the first RO membrane module 31 on the upstream side. The first module concentrated water line L313 circulates the concentrated water that has not permeated the RO membrane in the first RO membrane module 31. The collecting line L33 is connected to the downstream side of the plurality of first module concentrated water lines L313. The concentrated water that has circulated through the plurality of first module concentrated water lines L313 is collected in the collecting line L33. The plurality of second module supply water lines L321 are each connected upstream to the assembly line L33. The second module supply water line L321 supplies the concentrated water collected in the collection line L33 as supply water to the second RO membrane module 32 described later.

The plurality of second RO membrane modules 32 are each connected to the downstream side of the second module supply water line L321. The plurality of second RO membrane modules 32 separate the supply water supplied from the second module supply water line L321 into permeated water and concentrated water, respectively, by the RO membrane.
Each of the plurality of second module supply water lines L321 is connected to the second RO membrane module 32 on the upstream side and gathers on the upstream side of the permeate line L14 on the downstream side. The plurality of second module supply water lines L321 supplies the permeated water that has permeated the RO membrane in the second RO membrane module 32 to the permeated water line L14.

  The plurality of second module concentrated water lines L323 each have an upstream side connected to the second RO membrane module 32, and a downstream side gathers upstream of the concentrated water line L15. The plurality of second module concentrated water lines L323 supplies the concentrated water that has not passed through the RO membrane in the second RO membrane module 32 to the concentrated water line L15.

Each of the first RO membrane module 31 and the second RO membrane module 32 (hereinafter also simply referred to as RO membrane module) is configured by accommodating 1 to 6 RO membrane elements (not shown) in a vessel. The reverse osmosis membrane forming the RO membrane element has a negatively charged skin layer using a crosslinked wholly aromatic polyamide or the like, that is, a skin layer that is easily negatively charged, and preferably has an operating pressure of 0 The water permeation coefficient is 1.3 × 10 ^{−11 to} 1.7 × 10 ⁻¹¹ when a sodium chloride aqueous solution having a concentration of 500 mg / L, pH 7.0, and a temperature of 25 ° C. is supplied under the conditions of 0.7 MPa and a recovery rate of 15%. m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ and a salt removal rate of 99% or more.

Here, the operating pressure refers to the average operating pressure defined in Japanese Industrial Standard JIS K3802: 1995 “Membrane Terminology”. Here, the inlet pressure (feed water pressure) and the primary side pressure of the RO membrane module are primary side. The average value of the outlet pressure (concentrated water pressure). The recovery rate refers to the ratio (%) of the flow rate (B) of the permeated water to the flow rate (A) of the supply water to the RO membrane module (that is, B / A × 100). The water permeation coefficient is a value obtained by dividing the permeate flow rate (m ³ / s) by the membrane area (m ² ) and the effective pressure (Pa), and is an index indicating the permeation performance of water through the reverse osmosis membrane. That is, the water permeation coefficient means the amount of water that permeates the unit area of the membrane per unit time when a unit effective pressure is applied. The effective pressure is defined in Japanese Industrial Standard JIS K3802: 1995 “Membrane Term” and is a pressure obtained by subtracting the osmotic pressure difference and the secondary pressure from the operating pressure (average operating pressure). The salt removal rate is a value calculated from the concentration of specific salts before and after permeating the membrane, and is an index indicating the solute blocking performance in the reverse osmosis membrane. The salt removal rate (%) is determined by the following formula (1) from the concentration (C ₁ ) of specific salts in the feed water and the concentration (C ₂ ) of specific salts in the permeated water.
[Formula 1] (1-C ₂ / C ₁ ) × 100 (1)

The reverse osmosis membrane having the above skin layer and properties is commercially available as an RO membrane element. As such an RO membrane element, for example, model name “TMG20-400” manufactured by Toray Industries, Inc. (water permeability coefficient under the above conditions is 1.7 × 10 ⁻¹¹ m ³ · m ⁻² · s ⁻¹ · Pa ^-1 ), model name “RE8040-BLN” manufactured by Eunjin Chemical Co., Ltd. (water permeability coefficient under the above conditions is 1.6 × 10 ⁻¹¹ m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ ) and Nitto “ESPA1” manufactured by Denko Co., Ltd. (water permeability coefficient under the above conditions is 1.6 × 10 ⁻¹¹ m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ ) and the like.

Subsequently, a water treatment method (operation of the water treatment system 1) by the water treatment system 1 will be described. FIG. 3 is a diagram illustrating a procedure of the water treatment method according to the present embodiment.
As shown in FIG. 3, the water treatment method according to the present embodiment includes a first chemical injection step ST1, a first reaction step ST2, a second chemical injection step ST3, a second reaction step ST4, and a removal step ST5. And comprising.

  In the first chemical injection step ST1, bisulfite ions having a substance amount of 1 to 1.8 times the substance amount of formaldehyde discharged from the sterilization apparatus 100 are added to the water discharged from the sterilization apparatus 100. Add. In the first chemical injection step ST1, the supply amount of bisulfite ions is controlled by the first chemical injection control unit 41. The first chemical injection control unit 41 supplies a hydrogen sulfite ion source having a substance amount that is 1 to 1.8 times per unit time with respect to the amount of formaldehyde discharged from the sterilization apparatus 100 per unit time. The 1st chemical injection part 11 is controlled to supply to the 1st circulation line L16 (water circulation line L1).

  When the supply amount of formaldehyde in the first chemical injection step ST1 is less than 1 times the amount of formaldehyde discharged from the sterilization treatment apparatus 100, the concentration of formaldehyde in the permeated water flowing through the permeate line L14 increases. . On the other hand, when the supply amount of formaldehyde in the first chemical injection step ST1 exceeds 1.8 times the amount of substance of formaldehyde discharged from the sterilization treatment apparatus 100, sulfite in the permeated water flowing through the permeate line L14. The hydrogen ion concentration increases.

  Moreover, in 1st chemical injection step ST1, a pH adjuster is supplied by the pH adjustment chemical injection part 12 with respect to the water to which the bisulfite ion source was supplied. In 1st chemical injection step ST1, it is preferable to adjust pH to 6.0 or more and 6.5 or less. When the pH of the water subjected to the treatment of the first chemical injection step ST1 is less than 6.0 or more than 6.5, the reaction rate between formaldehyde and bisulfite ions may be reduced. There is a possibility that the pH of the permeate flowing through the permeate line L14 may deviate from the tap water quality standard (5.8 to 8.6).

  In the first reaction step ST2, after the first chemical injection step ST1, formaldehyde and bisulfite ions are reacted for 10 minutes or more. The reaction time between formaldehyde and bisulfite ions in the first reaction step ST2 is determined by the water circulation time from the first chemical injection section 11 to the second chemical injection section 21. That is, the 2nd medicine injection part 21 is arranged in the position where the circulation time of water from the 1st medicine injection part 11 to the 2nd medicine injection part 21 becomes 10 minutes or more. In addition, the circulation time of the water from the 1st chemical injection part 11 to the 2nd chemical injection part 21 is the piping length between the 1st chemical injection part 11 and the 2nd chemical injection part 21, a pipe diameter, and piping. It is determined by the speed of the water flowing inside and the amount of water in the first buffer tank 10. And the distribution | circulation time of the water from the 1st chemical injection part 11 to the 2nd chemical injection part 21 can be set by changing the speed | rate etc. of the water which distribute | circulates the inside of piping.

  In the first reaction step ST2, when the reaction time between formaldehyde and bisulfite ions is less than 10 minutes, the formaldehyde concentration of the permeated water flowing through the permeated water line L14 increases.

  In the second chemical injection step ST3, bisulfite ions having a substance amount of 4 to 8.2 times the amount of formaldehyde discharged from the sterilization apparatus 100 are added to the water after the first reaction step ST2. . In the second chemical injection step ST3, the second chemical injection control unit 42 controls the supply amount of bisulfite ions. The second chemical injection control unit 42 supplies a bisulfite ion source having a substance amount that is 4 to 8.2 times per unit time with respect to the amount of formaldehyde discharged from the sterilization apparatus 100 per unit time. The 2nd chemical injection part 21 is controlled to supply to the 2nd distribution line L12 (water distribution line L1).

  When the amount of formaldehyde supplied in the second chemical injection step ST3 is less than four times the amount of formaldehyde discharged from the sterilization apparatus 100, the concentration of formaldehyde in the permeated water flowing through the permeated water line L14 increases. . On the other hand, when the amount of formaldehyde supplied in the second chemical injection step ST3 exceeds 8.2 times the amount of formaldehyde discharged from the sterilization treatment apparatus 100, the sulfurous acid in the permeate flowing through the permeate line L14. The hydrogen ion concentration increases.

  Further, in the second chemical injection step ST3, as in the first chemical injection step ST1, the pH of the water supplied with the bisulfite ion source is adjusted using a pH adjuster (for example, an alkaline substance such as sodium hydroxide). It is desirable to do it. In 2nd chemical injection step ST3, Preferably, pH is adjusted to 6.0 or more and 6.5 or less.

  In 2nd reaction step ST4, after 2nd chemical injection step ST3, formaldehyde and bisulfite ion are made to react for 2 minutes or more. The reaction time in the second reaction step ST4 is preferably less than 5 minutes. The reaction time between formaldehyde and bisulfite ions in the second reaction step ST4 is determined by the water circulation time from the second chemical injection section 21 to the removal means 30. That is, the removal means 30 is disposed at a position where the water circulation time from the second drug injection section 21 to the removal means 30 is 2 minutes or more. Moreover, it is preferable that the removal means 30 is arrange | positioned in the position from which the circulation time of the water from the 2nd chemical injection part 21 to the removal means 30 will be less than 5 minutes. In addition, the circulation time of the water from the 2nd chemical injection part 21 to the removal means 30 is the piping length between the 2nd chemical injection part 21 and the removal means 30, a pipe diameter, and the water which distribute | circulates the inside of piping. It is determined by the speed and the amount of water in the second buffer tank 20. And the circulation time of the water from the 2nd chemical injection part 21 to the removal means 30 can be set by changing the speed | rate etc. of the water which distribute | circulates the inside of piping.

  In the second reaction step ST4, when the reaction time between formaldehyde and bisulfite ions is less than 2 minutes, the formaldehyde concentration of the permeated water flowing through the permeated water line L14 increases. Further, in the second reaction step ST4, when the reaction time between formaldehyde and bisulfite ions exceeds 5 minutes, the second buffer is used to secure the residence time of water between the second chemical injection section 21 and the removing means 30. The tank 20 needs to be enlarged.

In the removal step ST5, hydroxymethanesulfonic acid ions generated by the reaction of formaldehyde and bisulfite ions are removed by the RO membrane. Specifically, in the removal step ST5, permeated water (treated water) from which hydroxymethanesulfonic acid ions have been removed by membrane-separating water (feed water) pressurized by the pressure pump 22 with the RO membrane of the removing means 30. )
The permeated water that has passed through the RO membrane of the removing means 30 and circulated through the permeated water line L14 is reused in a retort device or the like. Part of the concentrated water that has passed through the concentrated water line L15 without passing through the RO membrane of the removing means 30 is discharged out of the water treatment system 1, and the remaining part is circulated through the second circulation line L17.

According to the water treatment method and the water treatment system according to the present embodiment, the following effects are produced.
(1) In the present embodiment, the water treatment method for removing formaldehyde is a first chemical injection step ST1, a first reaction step ST2, a second chemical injection step ST3, a second reaction step ST4, and a removal step ST5. And provided. In the first chemical injection step ST1, hydrogen sulfite having a substance amount of 1 to 1.8 times the amount of formaldehyde discharged from the sterilization apparatus 100 is added to the water discharged from the sterilization apparatus 100. Ions were added, and in the first reaction step ST2, formaldehyde and bisulfite ions were reacted for 10 minutes or longer. Further, in the second chemical injection step ST3, bisulfite ions having a substance amount of 4 to 8.2 times the amount of formaldehyde discharged from the sterilization apparatus 100 in the water after the first reaction step ST2. In the second reaction step ST4 for 2 minutes or longer.
As a result, formaldehyde can be efficiently removed from water containing formaldehyde, and hydrogen sulfite ions can be prevented from passing through the reverse osmosis membrane.

(2) In the present embodiment, the water treatment system 1 further includes bisulfite ions on the secondary side of the first chemical injection unit 11 and the first chemical injection unit 11 that supplies the hydrogen sulfite ion source to the water distribution line L1. A second chemical injection section 21 for supplying a source to the water distribution line L1, a removal means 30 for removing hydroxymethanesulfonic acid ions produced by the reaction of formaldehyde and bisulfite ions from water by a reverse osmosis membrane, and a first The first bisulfite control unit 41 that controls the supply amount of the bisulfite ion source from the chemical injection unit 11 to the water distribution line L1, and the supply amount of the bisulfite ion source from the second chemical injection unit 21 to the water distribution line L1 The control part 40 which has the 2nd chemical injection control part 42 which controls is supposed to be provided. In addition, the first chemical injection control unit 41 has a quantity of bisulfite ion that is 1 to 1.8 times per unit time with respect to the amount of formaldehyde discharged from the sterilization apparatus 100 per unit time. The first chemical injection unit 11 is controlled so that the source is supplied to the water distribution line L1, and the second chemical injection control unit 42 is unit for the amount of formaldehyde discharged from the sterilization treatment apparatus 100 per unit time. The 2nd chemical injection part 21 shall be controlled to supply the bisulfite ion source of the substance quantity which will be 4 times or more and 8.2 times or less per time to water distribution line L1. Furthermore, the 2nd medicine injection part 21 is arrange | positioned in the position from which the circulation time of the water from the 1st medicine injection part 11 to the 2nd medicine injection part 21 becomes 10 minutes or more, and the removal means 30 is 2nd medicine. It arrange | positioned in the position where the circulation time of the water from the injection part 21 to the removal means 30 becomes 2 minutes or more.
Thus, as with the above water treatment method, formaldehyde can be efficiently removed from the water containing formaldehyde, and hydrogen sulfite ions can be prevented from passing through the reverse osmosis membrane.

(3) In this embodiment, the removal means 30 was arrange | positioned in the position where the circulation time of the water from the 2nd chemical injection part 21 to the removal means 30 will be less than 5 minutes.
Thereby, the residence time of the water from the 2nd chemical injection part 21 to the removal means 30 can be shortened. Therefore, the cost can be reduced by reducing the capacity of the piping between the second chemical injection section 21 and the removing means 30 and the reaction tank (second buffer tank 20).

(4) In the present embodiment, the water treatment system 1 further includes a first buffer tank 10 disposed in the water circulation line L1, and the water circulation line L1 uses the first buffer to discharge water discharged from the sterilization treatment apparatus 100. The first circulation line L11 supplied to the tank 10, the first circulation line L16 for circulating the water in the first buffer tank 10, and the first circulation line for circulating the water in the first buffer tank 10 to the second chemical injection section 21 side. 2 distribution lines. Moreover, the 1st chemical injection part 11 shall supply a bisulfite ion source to the 1st circulation line L16.
Thereby, the bisulfite ion supplied from the 1st chemical injection part 11 circulates through the 1st circulation line L16, and is fully stirred. In addition, the first circulation line L16 can sufficiently ensure the reaction time between formaldehyde and bisulfite ions supplied from the first chemical injection section 11.

  As mentioned above, although the water treatment system 1 and the water treatment method which concern on one Embodiment of this invention were demonstrated, this invention is not restrict | limited to the above-mentioned embodiment, It can change suitably.

  The removal means 30 shown in FIG. 2 performs single-stage water flow by using the concentrated water of the former module (first RO membrane module 31) group as feed water for the latter module (second RO membrane module 32) group. The recovery rate of the permeated water (treated water) can be increased as compared with the water flow through the RO membrane module. In addition, by reducing the number of rear-stage RO membrane modules less than the number of front-stage modules, the membrane surface flow velocity on the primary side of the RO membrane can be maintained in a predetermined range in each stage, and fouling can be suppressed.

  Next, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

<Example 1>
Using the water treatment system 1 according to the above embodiment, the cooling wastewater discharged from the retort device (sterilization treatment device 100) was treated. The properties of the cooling effluent are as follows.

[Properties of cooling drainage]
Formaldehyde concentration: 1 mg / L
Free residual chlorine concentration: 2mg / L
pH: 6.5 to 7.5 (within tap water quality standards)
Electrical conductivity: about 150 μS / cm Temperature: 60 ° C.

  The amount of sodium bisulfite supplied from the first chemical injection section 11 to the water distribution line L1 with respect to the amount of formaldehyde discharged from the retort device per unit time ("first chemical injection amount" in Table 1) 1.5 times. Further, the amount of sodium bisulfite supplied from the second chemical injection section 21 to the water distribution line L1 with respect to the amount of formaldehyde discharged from the retort device per unit time ("second chemical injection amount" in Table 1). ) Was 4.5 times.

  Further, the flow rate of water and the amount of water in the first buffer tank 10 are set such that the water flow time (first reaction time) from the first chemical injection unit 11 to the second chemical injection unit 21 is 15 minutes. Was set to an amount. Further, the water circulation speed (second reaction time) from the second chemical injection section 21 to the removal means 30 is 4.5 minutes for the water circulation speed and the amount of water in the second buffer tank 20. Set to quantity. The processing conditions in the removal means 30 (RO membrane apparatus 50) are as follows.

[Operation conditions of RO membrane device]
RO membrane element: TMG20-400 (manufactured by Toray Industries, Inc.)
Operating pressure: 0.6 MPa
Recovery rate: 80%
Feed water temperature: 30 ° C
Feed water pH: 6.0-6.5

The contents of formaldehyde (HCHO) and sodium bisulfite (SBS) in the permeated water (treated water) obtained by the treatment with the water treatment system 1 were measured by GC / MS. The measurement results are shown in Table 1. The permeated water can be determined to be reusable as cooling water for the retort device when the formaldehyde concentration is 0.08 mg / L or less (tap water quality standard) and the SBS concentration is 1.5 mg / L or less. In the solution, SBS exists as bisulfite ions, but the concentration is expressed as the concentration of sodium salt.
FIG. 4 is a graph showing the relationship between the elapsed time from the first chemical injection and the concentration of generated formaldehyde.

<Examples 2-8 and Comparative Examples 1-6>
For other examples and comparative examples, the same procedure as in Example 1 except that the first dose, the first reaction time, the second dose, and the second reaction time were adjusted to the values shown in Table 1. The water treatment was performed. Table 1 shows the contents of formaldehyde (HCHO) and sodium bisulfite (SBS) in the permeated water (treated water) obtained in each Example and Comparative Example.

<Comparative Example 7>
In Comparative Example 7, the first chemical injection amount and the first reaction time were adjusted to the values shown in Table 1, and the water treatment was performed in the same procedure as Example 1 except that the second chemical injection was not performed. . The “first reaction time” in Comparative Example 7 is the water circulation time from the first chemical injection section 11 to the removal means 30. Table 1 shows the contents of formaldehyde (HCHO) and sodium bisulfite (SBS) in the permeated water (treated water) obtained in Comparative Example 7.

  From the results shown in FIG. 4, in the water treatment of Example 1, the formaldehyde concentration is sufficiently lowered by performing the second chemical injection after the formaldehyde concentration is lowered to 0.3 mg / L by the first chemical injection. It was confirmed that it was possible. In addition, free residual chlorine was not detected in the reaction liquid after 10 minutes from the first chemical injection and the reaction liquid after 15 minutes.

From a comparison between Example 5 and Comparative Example 4, it was found that the water treatment of Example 5 had a lower formaldehyde concentration of the permeated water than the water treatment of Comparative Example 4. Further, from comparison between Example 2 and Comparative Example 2, it was found that the water treatment of Example 2 had a lower bisulfite ion concentration of permeated water than the water treatment of Comparative Example 2.
From these results, the amount of the first chemical injection is set to 1 to 1.8 times the amount of formaldehyde discharged from the retort device per unit time. It was confirmed that formaldehyde can be removed and that bisulfite ions can be prevented from passing through the RO membrane.

From a comparison between Example 6 and Comparative Example 5, it was found that the water treatment of Example 6 had a lower formaldehyde concentration of the permeated water than the water treatment of Comparative Example 5.
From this result, it was confirmed that formaldehyde can be efficiently removed from water containing formaldehyde by setting the first reaction time to 10 minutes or more.

From a comparison between Example 4 and Comparative Example 3, it was found that the water treatment of Example 4 had a lower formaldehyde concentration of the permeated water than the water treatment of Comparative Example 3. Moreover, from the comparison between Example 2 and Comparative Example 1, it was found that the water treatment of Example 2 had a lower bisulfite ion concentration of permeated water than the water treatment of Comparative Example 1.
From these results, the amount of the second chemical injection is more than 4 times and less than 8.2 times the amount of formaldehyde discharged from the retort device per unit time. It was confirmed that formaldehyde can be removed and that bisulfite ions can be prevented from passing through the RO membrane.

From a comparison between Example 6 and Comparative Example 6, it was found that the water treatment of Example 6 had a lower formaldehyde concentration of permeated water than the water treatment of Comparative Example 6.
From this result, it was confirmed that formaldehyde can be efficiently removed from water containing formaldehyde by setting the second reaction time to 2 minutes or longer.

From a comparison between Example 1 and Comparative Example 7, it was found that the water treatment of Example 1 had a lower formaldehyde concentration of the permeated water than the water treatment of Comparative Example 6.
From these results, it was confirmed that formaldehyde can be efficiently removed from water containing formaldehyde by adding a hydrogen sulfite ion source to water in two stages of the first chemical injection and the second chemical injection rather than in one stage. This is considered to be because when a large amount of the bisulfite ion source is added at once, a part of the bisulfite ion reacts with the residual chlorine prior to formaldehyde.

According to the study by the present inventors, it has been found that the oxidation-reduction reaction between residual chlorine and bisulfite ions proceeds much faster than the addition reaction between bisulfite ions and formaldehyde. For this reason, it is assumed that the presence of residual chlorine acts in the direction of inhibiting the production of hydroxymethanesulfonate ions.
Therefore, in the method of adding a hydrogen sulfite ion source to formaldehyde-containing water in two steps according to the present application, a relatively small amount of hydrogen sulfite ion is supplied by the first chemical injection, and the reaction is performed in a relatively long time in the first reaction. I am letting. As a result, as described above with reference to FIG. 4, residual chlorine is almost completely removed from the water and generation of hydroxymethanesulfonate ions is allowed to proceed. Further, in the present application, a relatively large amount of bisulfite ion is supplied by the second chemical injection, and the reaction is performed in a relatively short time by the second reaction. Thus, a high concentration of bisulfite ion is present in the unreacted trace formaldehyde to promote the production of hydroxymethane sulfonate ion.

  In addition, the cooling water used for a retort process adds sodium hypochlorite, and maintains a residual chlorine density | concentration to about 1-3 mg / L from the request | requirement on food hygiene. On the other hand, when the SBS concentration of the permeated water (treated water) that has passed through the removal step is higher than 1.5 mg / L, SBS and residual chlorine react during the preparation of cooling water. Sodium hypochlorite needs to be added. Therefore, by setting the standard of the SBS concentration of the permeated water (treated water) to be reused for the retort treatment to 1.5 mg / L or less as described above, it is performed to maintain residual chlorine at the target concentration. Control of the dosage of sodium chlorate becomes easy.

DESCRIPTION OF SYMBOLS 1 ... Water treatment system 11 ... 1st chemical injection part 21 ... 2nd chemical injection part 30 ... Removal means 40 ... Control part 41 ... 1st chemical injection control part 42 ... 2nd chemical injection control part 100 ... Sterilization processing apparatus L1 ... Water distribution line L11 ... 1st distribution line L12 ... 2nd distribution line L16 ... 1st circulation line ST1 ... 1st chemical injection step ST2 ... 1st reaction step ST3 ... 2nd chemical injection step ST4 ... 2nd reaction step ST5 ... Removal Step

Claims (4)

A water treatment method for removing formaldehyde from water containing formaldehyde discharged from a sterilizer,
The sterilization apparatus is a retort apparatus, a pasteurize apparatus or a container cleaning apparatus used in a food factory or a beverage factory,
A first chemical injection step of adding, to the water discharged from the sterilization apparatus, bisulfite ions having a substance amount of 1 to 1.8 times the amount of formaldehyde discharged from the sterilization apparatus;
A first reaction step in which formaldehyde and bisulfite ion are reacted for 10 minutes or longer after the first chemical injection step;
A second chemical injection step of adding to the water after the first reaction step bisulfite ions having a substance amount of 4 to 8.2 times the amount of formaldehyde discharged from the sterilization apparatus;
A second reaction step in which formaldehyde and bisulfite ion are reacted for 2 minutes or longer after the second chemical injection step;
A water treatment method comprising: removing from the water after the second reaction step, hydroxymethanesulfonic acid ions produced by the reaction of formaldehyde and bisulfite ions by a reverse osmosis membrane. A water treatment system for removing formaldehyde from water containing formaldehyde discharged from a sterilization treatment apparatus,
The sterilization apparatus is a retort apparatus, a pasteurize apparatus or a container cleaning apparatus used in a food factory or a beverage factory,
A water distribution line through which water containing formaldehyde discharged from the sterilization apparatus flows;
A first chemical injection section that supplies a hydrogen sulfite ion source that dissolves in water and generates bisulfite ions into the water distribution line;
On the secondary side of the first chemical injection part, a second chemical injection part that further supplies a hydrogen sulfite ion source to the water distribution line;
Removal means for removing the hydroxymethanesulfonic acid ions generated by the reaction of formaldehyde and bisulfite ions, which are supplied through the water flowing through the water distribution line, from the water by a reverse osmosis membrane;
A first chemical injection control unit for controlling the supply amount of the bisulfite ion source from the first chemical injection unit to the water distribution line, and a supply of the hydrogen sulfite ion source from the second chemical injection unit to the water distribution line A second medicine injection control unit for controlling the amount, and a control unit,
The first chemical injection control unit supplies the bisulfite ion source having a substance amount that is 1 to 1.8 times per unit time with respect to the amount of formaldehyde discharged from the sterilization apparatus per unit time. Controlling the first chemical injection part to supply to the water distribution line;
The second chemical injection control unit is configured to supply a bisulfite ion source having a substance amount that is not less than 4 times and not more than 8.2 times per unit time with respect to the amount of formaldehyde discharged from the sterilization apparatus per unit time. Controlling the second chemical injection part to supply to the water distribution line;
The second chemical injection part is arranged at a position where the circulation time of water from the first chemical injection part to the second chemical injection part is 10 minutes or more,
The said removal means is a water treatment system arrange | positioned in the position where the circulation time of the water from the said 2nd chemical injection part to the said removal means becomes 2 minutes or more.   3. The water treatment system according to claim 2, wherein the removing unit is disposed at a position where a water circulation time from the second chemical injection unit to the removing unit is less than 5 minutes. A first buffer tank disposed in the water distribution line;
The water circulation line includes a first circulation line that supplies water discharged from the sterilization apparatus to the first buffer tank, a first circulation line that circulates water in the first buffer tank, and the first A second distribution line that distributes the water in the buffer tank to the second drug injection side,
The water treatment system according to claim 2 or 3 , wherein the first chemical injection section supplies a hydrogen sulfite ion source to the first circulation line.

Images