JP2000126780A - Chlorine-sterilization system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cost by extending a maintenance period by reducing the adhesion and growth of scale on an electrode material and to sterilize a subject process economically by preparing salt water by a pure water means and a produced salt which passed through a pure water apparatus for raw water and generating NaClO in an electrolytic cell. SOLUTION: Water from a river is led to a flocculation-precipitation basin 1 and after being mixed with a flocculant 1a, passed through a filtration basin 2, a contact basin 5, and an active carbon basin 5 to improve water quality. When hydrogen discharged from an electrolytic cell 15 and a hypo-salt tank 16 is led to the inlet side of a water removing unit MS, since it is converted into water, produced water taken up from the bottom side of the unit MS is supplied as raw water to a pure water apparatus 12 through an injection valve 12d. Purified salt 11a and water from the injection valve 12a of the pure water apparatus 12 are mixed in a salt water tank 11 to prepare salt water. The salt water is introduced into the electrolytic cell 15 through a mixer 14 by a salt water pump 13. In the electrolytic cell 15, pure water from the pure water apparatus 12 is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called chlorine mixing pond for disinfecting chlorine in a water treatment process from the viewpoint of environmental health, and more particularly to a chlorine disinfection system for a water supply and sewerage process.

[0002]

2. Description of the Related Art In water supply and sewerage systems, water intake from rivers is filtered, stored in a distribution reservoir, and then transmitted. However, the distribution reservoir is required to disinfect with chlorine to eliminate pathogenic bacteria and transmit water. . For example, pursuant to the Water Supply Law, the residual water to be retained by the water tap is set to 0.1 ppm or more, and the water injection plant controls chlorine injection. Also, sewage is required to be chlorinated in order to be discharged into rivers after sewage treatment.

[0003] Conventionally, chlorine gas (C
1) or sodium hypochlorite (NaClO). The treated water of these water and sewage systems is basically operated continuously for 24 hours, and chlorine sterilization is also consumed by organic matter and ammonia nitrogen in the water, so that storage equipment is required and continuous operation is required. However,
Chlorine is highly toxic and has special safety and security controls. When using liquefied chlorine, it is necessary to notify or obtain permission from the competent authority depending on the facility size and content. This shall not apply to the use of other disinfectants.

Therefore, in recent years, NaClO has been used as a disinfectant.
There is an increasing number of cases of storing and using (hypochlorite). It has been recognized that producing and using hyposalt at the installation site is economical. The produced hyposalt is a method in which water and salt are mixed as raw materials to produce salt water, which is electrolyzed to produce NaClO.
No. 3 publication can be mentioned.

On the other hand, in the water purification process, an advanced water purification treatment for removing odorous substances and toxic substances such as trihalomethane in water by providing an ozone contact pond and mixing ozone gas and water to be treated has been put to practical use. For sterilization of Escherichia coli and the like, it is obliged to establish a chlorine mixing pond and perform the chlorine sterilization treatment.

[0006]

However, since hypochlorite is a deep yellow liquid having an effective chlorine concentration of about 5 to 12% and is highly alkaline, the storage tank is a cylindrical vertical floor-standing indoor type made of titanium and FRP. A plurality of tanks each having a capacity of 10 m ₃ / unit are provided, and are refilled by a transportation vehicle approximately every 10 days to cope with continuous consumption. The higher the concentration of the available chlorine component NaClO, the more unstable the available chlorine component during storage and the lower the NaClO concentration.
Since it is transformed into O _{3 and the} like, the smaller the tank storage amount is, the more advantageous it is. However, it is disadvantageous because refilling with a transport vehicle increases and costs are increased.

[0007] On the other hand, the generated hypochlorite is used as a raw material to generate NaClO by electrolyzing salt water in which water and salt are mixed, and impurities in the water are converted to a positive electrode (Pt material) and −
Since it adheres and forms as a scale (Ca or Mg component) on the surface with the pole (Ti material), there is a drawback that the current efficiency of the actual amount generated by Faraday's law is reduced. Required maintenance work.

[0008] It is an object of the present invention to provide a disinfection system which improves the production hypochlorite apparatus and economically disinfects a symmetric process.

[0009]

According to a first aspect of the present invention, there is provided a sterilization system for producing salt water by using pure water means and purified salt which have passed through a pure water apparatus with respect to raw water, and supplying the salt water to an electrolysis tank. The purpose of the present invention is to produce NaClO to minimize the scale generated on the electrode material, to lengthen the maintenance period, and to reduce the cost.

[0010] The sterilization system according to the second aspect of the present invention is provided with control means for controlling and supplying an appropriate amount of NaClO on the output side of the electrolysis tank using a supply valve of NaClO and a water distribution value of a treated water meter. Therefore, it is possible to drive economically.

According to a third aspect of the present invention, in the sterilization system, a plurality of electrode blocks of the electrolysis tank are divided into a plurality of sets, and a plurality of switches are opened and closed according to the increase / decrease value of the treated water meter. An object of the present invention is to improve the reliability by equalizing the life of the electrode block by the operation mode command of the electrode block.

In the sterilization system according to the present invention, when the water treatment process has an ozone contact pond, an exhaust ozone treatment device is always attached, so that hydrogen gas (H ₂₎ which is an unnecessary component of the electrolysis tank is used. ) To react water with H ₂ and ozone (O ₃ ) to produce water (H ₂ O), guide the water to the inlet of a pure water system, and save energy by means of reuse.

[0013] In the sterilization system according to the fifth aspect, the means for providing a turbulent cover around the tip of the NaClO pouring into the chlorine mixing pond allows the NaClO and the treated water to mix well, thereby reducing the mixing time. The purpose is to shorten the size of the chlorine mixing pond to obtain economic effects.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows the water supply process.
The water intake from the river is led to the coagulation sedimentation basin 1 and the coagulant 1a
The sludge 1b accumulates in the lower part of the pond because the waste is solidified to improve the turbidity by mixing unnecessary substances in the water. However, the sludge is periodically carried out by a sludge treatment machine (not shown). Next, the water is further purified through the filtration pond 2, and the flow meter 3a becomes the treated water amount. Furthermore, as a process for improving water quality, the ozone contact pond 4 and the activated carbon pond 5 are combined to make delicious water.

The ozone contact pond 4 generates ozone (O ₃ ) gas by the ozone generator 4a and mixes it with water as bubbles from the lower part of the pond, but the remaining amount of ozone digestion is discharged into the upper space of the pond (generally). About 20% of the injected amount of ozone gas is discharged). Since the discharged ozone is harmful, the discharged ozone treatment device 4b is externally supplied with 0.1 p by the water removal unit MS, the heater H, the ozone decomposer MnO _2, and the discharge fan F.
It is discharged as ozone below pm.

When hydrogen (H ₂ ) discharged from the electrolysis tank 15 and the hypochlorite tank 16 is led to the inlet side of the water removal unit MS, it is converted into water by the reaction of the reaction formula (Formula 6). The produced water taken out from the bottom side of the removing unit MS is fed as raw water into the pure water device 12 via the injection valve 12d. The raw material water flows into the chlorine mixing pond 7 from the activated carbon pond 5 or a hyposalt injector 6 is provided in the middle of the piping to supply Na.
ClO and H ₂ O are reacted according to the reaction formulas (Chem. 4) and (Chem. 5) and sterilized.

The hyposalt injector 6a may be provided as a spare at the inlet side of the chlorine mixing pond 7 with the hyposalt injector 6a. There is a residual salt meter 7a on the outlet side, which is a control value as to whether or not sterilization is sufficient. The sterilized water is supplied to the distribution reservoir 8, and the distribution pump 9 supplies water according to demand. Therefore, the flow meter 3b becomes a management value indicating the amount of water supply. The water from the activated carbon pond 5 and the above-mentioned generated water are supplied to the pure water apparatus 1 via the injection valves 12c and 12d.
2 is supplied.

[0019] The process controller 10 generates various sensor data and an open / close signal by the process controller 10, operates the whole process monitor and controls for 24 hours, and supplies safe and delicious water.

On the other hand, for the production of hyposalt, a salt water is prepared by mixing a purified salt 11a in a salt water tank 11 and water from an injection valve 12a of a pure water apparatus 12. The salt water is supplied to the electrolysis tank 15 at a constant salt water concentration through the mixer 14 by the salt water pump 13. By using pure water from the pure water device 12 in the electrolysis tank 15, the scale (Ca or Mg component) adheres to the surface of the negative electrode (Ti material) of the present invention as compared with the conventional negative electrode. This makes it difficult to reduce the current efficiency, eliminates the need for maintenance work for periodically stopping and flowing and removing hydrochloric acid, and increasing the operating efficiency of the water treatment process. Details regarding this point will be described later.

The electrolysis tank 15 is divided into a plurality of electrode blocks, and is connected to a DC power supply 15a through a switch 15b.
Or, if given as P2 or P3, a + electrode (P plane)
In the reaction formula (Chem. 1), the reaction of the reaction formula (Chem. 3) occurs in the negative electrode (N surface) and the reaction formula (Chem. 3) occurs in the liquid. Store to some extent.

[0022]

[Formula 1] P surface = 2Cl ~ ⇒Cl ₂ + 2e ~

[0023]

## STR2 ## N surface = 2Na positive ions + 2H ₂ O + 2e ~ ⇒
2NaOH + H ₂

[0024]

Embedded image In the liquid = 2NaOH + Cl ₂ ⇒2NaClO + H ₂

[0025]

Embedded image NaClO + H ₂ O⇔HClO + NaOH

[0026]

[Formula 5] HClO⇔ClO ~ + H plus ion

[0027]

Embedded image increasing the pressure by _{H 2 O + O 3 + H} 2 ⇒2H 2 O + O 2 TsugiAshio pump 16a, hypochlorite injection valve 1
An appropriate amount is controlled by 6b, and is discharged from the hypochlorite injector 6 into the water of the chlorine mixing pond 7 and sterilized. The control unit 17 controls the flow rate data of the flow meter 3a and the flow meter 3b, the residual salt meter 7a, the DC power supply 15a, and the pure water apparatus 12 as a whole to perform optimal hyposalt generation and injection.

That is, the operation of the control unit 17 will be described with reference to FIG. When the flow rate detection value from the flow meter 3b and the hypochlorite concentration value from the residual salt meter 7a are input to the control unit 17, the control unit 1
In FIG. 7, in response to a hypochlorite injection target value (for example, 20 mg / L) command, the treated water amount of the flow meter (Q1) 3b and the residual salt meter 7a
Using the actual measurement value (0.1 mg / L or less), the calculation (basic injection amount-residual salt content + consumption amount = corrected basic injection rate) is performed, and a constant (process structure and conditions specific to the application site) and correction (application The sub-salt injection amount is determined in consideration of the site-specific residence time, insolation amount, and injection history data), and the throttle amount of the hypo-salt injection valve 16b is variably designated. The hypochlorite injection valve 16b may be manually operated.

The calculation unit calculates the amount of generation from the amount of hypochlorite injection. The condition is determined from the remaining amount of hypochlorite and the generation reference value by the liquid level meter of the hypochlorite tank 16, and the electrolysis command is calculated. The switch 15b is closed by the DC power supply 15a, and NaClO is generated in the electrolysis tank 15 and sent to the hypochlorite tank 16. Accordingly, since an appropriate amount of hyposalt is injected, the present invention eliminates the extra hyposalt tank 16 unlike the prior art, and reduces the installation space and reduces the rate of autolysis of hyposalt by storing a large amount of NaClO. , More economical operation became possible. Details regarding this point will be described later with reference to FIG.

In this embodiment, the raw water of the pure water apparatus 12 is taken out from the front side of the chlorine mixing pond 7 and taken out from the lower end of the MS of the waste ozone treatment apparatus 4b.
Although it is obtained through 2d (FIG. 1), when the electrolysis command is small, the amount of raw water used is also small, so that one open / close valve 12d is opened and the other open / close valve 12c is closed, so that energy saving operation can be performed.

As shown in FIG. 2, the hypochlorite injector 6 generates turbulent water at the end of the turbulent flow cover 16c, and ejects an appropriate amount of NaClO solution from the central portion by the hypochlorite injection valve 16b. Since the mixing reaction is well performed, it is possible to prevent hyposalt from being injected in vain.

FIG. 3 shows a plurality of electrode blocks of the electrolysis tank 15, in which the + electrodes are indicated by P1 to P3. The pole may be common as N; As shown in FIG. 5, the amount of electrolysis at this time was 1.326 × 0.6 (gr) NaCl at 1 Ah, assuming n1 points when there was one electrode block.
O can be generated by the Faraday rule. H2 generated at that time
The gas is 0.422 L. When the number of the electrode blocks is two, the number is n2, and when the number is three, the number is n3. Thus, the amount of NaClO can be increased. In addition, when the amount of use of the NaClO at the n1 point is n
When driving cyclically from 1 to n2 to n3 to n1,
The electrode life is uniform, the maintenance period is lengthened, and an economic effect is obtained. Of course, switching from n1 to n2 is performed by the switch 15b in FIG.

On the other hand, as shown in FIG. 6, the conventional electrode life is 2.5 × 10 ³ (h), where the horizontal axis represents the operation time (h) and the vertical axis represents the scale adhesion (gr). Occasionally, scale adhesion at the point x occurred, and the aforementioned hydrochloric acid was circulated to remove Ca and Mg as scale components (A curve). According to the present invention, since the pure water apparatus is used, the curve becomes a B curve, the amount of scale adhesion is remarkably reduced, and the operation time can be prolonged.

FIG. 7 shows the characteristic of the hypochlorite autolysis rate (%) with respect to the standing time (horizontal axis) of NaClO, which changes to NaClO ₃ at a rate of about 1% / day. Since the amount of available hypochlorous acid (NaClO) decreases, it can be seen that it is more economical to produce NaClO suitable for the amount used as shown in FIG. 1 of the present invention.

FIG. 8 shows the running cost (RC) on the vertical axis.
And the horizontal axis is the treated water volume (Q) at the target site,
A characteristic is that if you purchase hyposalt and put multiple storage tanks,
The B characteristic shows the case where chlorine is purchased and the storage tank is placed, and the C characteristic shows the case where the storage tank is minimized by the generated hyposalt according to the present invention, and it can be seen that the total cost is excellent economically.

[0036]

As described above, according to the chlorine disinfection system of the present invention, the following effects can be achieved.

(1) Since a pure water apparatus is provided on the input side of the electrolysis tank, the maintenance period for electrolytic cleaning is prolonged, the maintenance cost is reduced, and the operating efficiency of the water treatment plant is improved.

(2) NaClO is placed on the output side of the electrolysis tank.
There is a control device that can indicate the appropriate amount of NaClO according to the supply throttle valve and the detected value of the treated water meter, so the extra storage tank is reduced, the installation space is minimized, and economical operation becomes possible. Was.

(3) As an electrolysis tank in which a plurality of electrode blocks are divided into a plurality of sets, cyclic operation or parallel operation can be performed with each switch, so that operation reliability is improved and electric cost during operation is improved. Can be kept low.

(4) Since the waste ozone gas from the ozone contact pond and the unnecessary H2 gas on the electrolysis tank side are mixed to produce water and can be reused in the pure water apparatus, energy saving operation is achieved.

(5) Since the hypochlorite injector is provided with a turbulent flow cover, it reacts well with the treated water, so that the residence time of the chlorine mixing pond can be shortened. It can be kept low.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a chlorine sterilization system for a water purification process according to an embodiment of the present invention.

FIG. 2 is a detailed view of the hypochlorite injector used in FIG.

FIG. 3 is a side sectional view showing the electrolysis tank used in FIG.

FIG. 4 is a block diagram illustrating a configuration in a control unit used in FIG. 1;

FIG. 5: DC power supply (Ah) and NaC in electrolysis tank
FIG. 4 is a characteristic diagram with the amount of 10 produced (gr).

FIG. 6 is a characteristic diagram showing a relationship between a scale adhesion amount (gr) and an operation time in an electrolysis tank.

FIG. 7 is a characteristic diagram of NaClO self-decomposition rate in a hypochlorite tank.

FIG. 8 is a characteristic diagram comparing running costs of the generated hypochlorite system of the present invention and an alternative method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Coagulation sedimentation basin, 1a ... Coagulant, 1b ... Sludge, 2 ... Filtration pond, 3 ... Flow meter, 4 ... Ozone contact pond, 4a ... Ozone generator, 4b ... Waste ozone treatment apparatus, 5 ... Activated carbon pond, 6 ... hyposalt injector, 6a ... hyposalt injector, 7 ... chlorine mixing pond, 7a
... Remaining salt meter, 8 ... Distribution reservoir, 9 ... Distribution pump, 10 ... Process control unit, 11 ... Salt water tank, 11a ... Purified salt, 12 ... Pure water device, 12a-12b ... Injection valve, 13 ... Salt water pump, 1
4 mixer, 15 electrolysis tank, 15a DC power supply, 1
5b: switch, 16: hyposalt tank, 16a: hyposalt pump, 16b: hyposalt injection valve, 16c: turbulent cover,
16d: liquid level meter, 17: control unit.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 1/50 550 C02F 1/50 550L A61L 2/16 A61L 2/16 Z 2/24 2/24 C02F 1 / 46 C02F 1/46 Z 1/78 1/78 (72) Inventor Masamitsu Nakazawa 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture Inside the Kokubu Plant of Hitachi, Ltd. (72) Inventor Masayuki Yamashita Hitachi City, Ibaraki Prefecture 1-1-1, Kokubucho, Kokubu Plant, Hitachi, Ltd. (72) Inventor Shigeo Shiono 1-1-1, Kokubuncho, Hitachi, Hitachi City, Ibaraki Prefecture F-term in Hitachi Kokubu Plant, Ltd. 4C058 AA20 BB07 CC04 DD07 EE30 JJ07 4D050 AA02 AA03 AA15 AB06 BB02 BB06 BD02 BD03 BD04 BD06 BD08 CA06 CA15 CA16 4D061 DA02 DA08 DB01 EA02 EB04 EB20 EB30 EB37 EB39 ED13 FA06 FA13 FA14 FA16 GA02 GA19 G C02 GC06 GC12 GC19

Claims (5)

[Claims] 1. An apparatus for sterilizing water by supplying sodium hypochlorite obtained by electrolysis to a chlorine mixing pond for water treatment, wherein a pure water apparatus is provided on an input side of the electrolysis tank. Chlorine sterilization system. 2. An apparatus for sterilizing water by supplying sodium hypochlorite obtained by electrolysis to a chlorine mixing pond for water treatment, comprising: a supply throttle valve, a treated water meter at an output side of the electrolysis tank; A chlorine sterilization system, comprising: a control device for instructing a throttle amount of a supply throttle valve corresponding to a detection value of a treated water meter. 3. An apparatus for sterilizing water by supplying sodium hypochlorite obtained by electrolysis to a chlorine mixing pond for water treatment, wherein an output side of an electrolysis tank in which a plurality of electrode blocks are divided into a plurality of sets. A chlorine disinfection system comprising a supply throttle valve, a treated water meter, a switch connected to each of the electrode blocks, and a control device for instructing opening and closing of each switch in accordance with a detected value of the treated water meter. . 4. An apparatus for sterilizing water by supplying sodium hypochlorite obtained by electrolysis to a chlorine mixing pond for water treatment, wherein an ozone contact pond is provided during the water treatment process, A chlorine disinfection system, wherein hydrogen gas at the outlet side of the electrolysis tank is connected to the inlet side. 5. The chlorine disinfection system according to claim 1, wherein a sodium hypochlorite injector having a turbulent flow cover is provided in the chlorine mixing pond.