FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
OZONE WATER PRODUCTION APPARATUS, WATER TREATMENT APPARATUS,
AND OZONE WATER PRODUCTION METHOD
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED
AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
Field
[0001] The present disclosure relates to an ozone water
production apparatus, a water treatment apparatus, and an
5 ozone water production method for producing ozone water for
use in, for example, removing organic substances.
Background
[0002] Membrane bioreactor is known as a method for
10 treating wastewater containing organic substances, in which
organic substances in water to be treated are decomposed
through biological treatment, and clear treated water is
obtained through solid-liquid separation using a separation
membrane that is also called a filtration membrane.
15 Continuous use of the separation membrane causes pollutants
including sludge, suspended solids, microorganisms, and
microbial metabolites to adhere or stick to the membrane
surface and the inside of the membrane. Consequently, the
filtration performance of the separation membrane degrades
20 over time. Therefore, a water treatment facility using a
separation membrane has a membrane cleaning facility for
cleaning the separation membrane, and the separation
membrane is periodically cleaned by the membrane cleaning
facility.
25 [0003] Cleaning with ozone has been proposed as a method
for cleaning a separation membrane in a membrane cleaning
facility. Ozone is unstable and easily self-decomposes,
and in particular, the life of ozone in water is extremely
short. For example, at ordinary temperature and pressure,
30 the half-life of ozone in water is about 10 minutes. The
half-life of ozone in water is also affected by pH,
temperature, and the like. For this reason, depending on
the distance, time, environment, and the like for
3
transporting generated ozone water to the separation
membrane to be cleaned, there may be non-negligible
ineffective consumption, i.e. self-decomposition in ozone
water, that is, consumption of ozone that does not
5 contribute to the cleaning of the separation membrane.
This leads to the problem that it is necessary to provide
an ozone gas generation source with an excessive capacity
or supply ozone gas for an excessive period of time in
order to compensate for the ineffective consumption of
10 ozone.
[0004] Patent Literature 1 discloses a membrane cleaning
method for cleaning a separation membrane by causing ozone
water to flow through the separation membrane to decompose
organic substances adhering to the separation membrane.
15 With the membrane cleaning method described in Patent
Literature 1, the self-decomposition of dissolved ozone is
reduced by maintaining the pH of ozone water at two to five
using a pH adjusting device, which solves the above problem.
20 Citation List
Patent Literature
[0005] Patent Literature 1: Japanese Patent No. 6430091
Summary
25 Technical Problem
[0006] However, with the technique described in Patent
Literature 1, the pH of ozone water is maintained at two to
five by supplying an acid, or an acid solution, to an ozone
water generation unit that dissolves ozone gas in solvent
30 water. Thus, there should be a storage unit for storing
acid near the ozone water generation unit, which imposes
restrictions on installation.
[0007] The present disclosure has been made in view of
4
the above, and an object thereof is to obtain an ozone
water production apparatus capable of reducing the
ineffective consumption of ozone while avoiding imposing
restrictions on installation.
5
Solution to Problem
[0008] In order to solve the above-described problems
and achieve the object, an ozone water production apparatus
according to the present disclosure includes a first gas
10 supply unit that supplies a first gas containing an oxygen
gas, and a second gas supply unit that supplies a second
gas containing at least one of carbon dioxide gas, nitrogen
gas, and nitrogen oxide gas. The ozone water production
apparatus also includes an electric discharge unit that
15 generates a third gas containing ozone gas by performing
electric discharge treatment on a gas containing the first
gas supplied by the first gas supply unit and the second
gas supplied by the second gas supply unit, and an ozone
water generation unit that generates ozone water by
20 dissolving the third gas in solvent water.
Advantageous Effects of Invention
[0009] The ozone water production apparatus according to
the present disclosure can achieve the effect of reducing
25 the ineffective consumption of ozone while avoiding
imposing restrictions on installation.
Brief Description of Drawings
[0010] FIG. 1 is a diagram illustrating an exemplary
30 configuration of a water treatment apparatus according to a
first embodiment.
FIG. 2 is a diagram illustrating an exemplary
configuration of a control circuit according to the first
5
embodiment.
FIG. 3 is a flowchart illustrating an exemplary
procedure for controlling ozone water production in a
condition control unit according to the first embodiment.
5 FIG. 4 is a diagram illustrating an exemplary
configuration of a water treatment apparatus according to a
second embodiment.
FIG. 5 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
10 according to a third embodiment.
FIG. 6 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
according to a fourth embodiment.
FIG. 7 is a diagram illustrating an exemplary
15 configuration of an ozone water production apparatus
according to a fifth embodiment.
FIG. 8 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
according to a sixth embodiment.
20 FIG. 9 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
according to a seventh embodiment.
FIG. 10 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
25 according to an eighth embodiment.
FIG. 11 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
according to a ninth embodiment.
FIG. 12 is a diagram illustrating an exemplary
30 configuration of an ozone water production apparatus
according to a tenth embodiment.
FIG. 13 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
6
according to an eleventh embodiment.
Description of Embodiments
[0011] Hereinafter, an ozone water production apparatus,
5 a water treatment apparatus, and an ozone water production
method according to embodiments will be described in detail
with reference to the drawings.
[0012] First Embodiment.
FIG. 1 is a diagram illustrating an exemplary
10 configuration of a water treatment apparatus according to
the first embodiment. The water treatment apparatus
according to the present embodiment purifies water to be
treated such as sewage or industrial wastewater using
membrane bioreactor (MBR). As illustrated in FIG. 1, the
15 water treatment apparatus includes a treatment tank 10, a
separation membrane 11, a membrane state measurement unit
20, a switching valve 21, a process control unit 22, a
filtered water pump 23, and an ozone water production
apparatus 100 that functions as a membrane cleaning
20 apparatus.
[0013] Water to be treated is introduced into the
treatment tank 10 through a pipe 1a for water to be treated.
The water to be treated is subjected to biodegradation
treatment with activated sludge in the treatment tank 10,
25 then subjected to filtration treatment from the primary
side to the secondary side of the membrane in the
separation membrane 11, and discharged via a filtered water
pipe 2a and a discharge pipe 2b. In the present embodiment,
purification is performed through MBR that involves solid30 liquid separation into activated sludge and membranefiltered clear water at the separation membrane 11;
therefore, a final sedimentation basin is not required, and
a very simple and compact water treatment apparatus can be
7
realized. The water treatment apparatus according to the
present embodiment performs a membrane filtration process
in which water to be treated is purified and a membrane
cleaning process in which the separation membrane 11 is
5 cleaned. The membrane cleaning process enables the
filtration performance of the separation membrane 11 to be
maintained.
[0014] The filtered water pipe 2a is equipped with the
membrane state measurement unit 20 and the switching valve
10 21. The switching valve 21 is connected to the discharge
pipe 2b equipped with the filtered water pump 23, and to a
membrane cleaning pipe 3d equipped with the ozone water
production apparatus 100. The switching valve 21 switches
the connection of the filtered water pipe 2a between the
15 discharge pipe 2b and the membrane cleaning pipe 3d based
on an instruction from the process control unit 22.
[0015] The process control unit 22 manages the membrane
filtration process and the membrane cleaning process. When
transitioning from the membrane filtration process to the
20 membrane cleaning process, the process control unit 22
instructs the switching valve 21 to connect the filtered
water pipe 2a to the membrane cleaning pipe 3d. When
transitioning from the membrane cleaning process to the
membrane filtration process, the process control unit 22
25 instructs the switching valve 21 to connect the filtered
water pipe 2a to the discharge pipe 2b. Once the filtered
water pipe 2a is connected to the discharge pipe 2b by the
switching valve 21, the membrane-filtered clear water is
discharged via the discharge pipe 2b. Once the filtered
30 water pipe 2a is connected to the membrane cleaning pipe 3d
by the switching valve 21, the separation membrane 11 is
cleaned by the ozone water production apparatus 100 which
is a membrane cleaning apparatus.
8
[0016] In the process in which clear water is obtained
through membrane filtration at the separation membrane 11
after biodegradation treatment, pollutants including sludge,
suspended solids, microorganisms, and microbial metabolites
5 adhere or stick to the surface and the inside of the
separation membrane 11. This causes an increase in
membrane permeation differential pressure, i.e. the
difference between the pressure on the secondary side of
the membrane and the atmospheric pressure during the
10 membrane filtration treatment, which results in time
degradation of filtration performance such as a decrease in
flux, i.e. the amount of filtered water per unit time and
per unit membrane filtration area. Therefore, in order to
maintain the filtration performance of the separation
15 membrane 11, it is necessary to perform the membrane
cleaning process of cleaning and removing pollutants from
the inside and the surface of the separation membrane. In
the membrane cleaning process according to the present
embodiment, while the membrane filtration is suspended,
20 ozone water is supplied as a cleaning liquid in the
direction from the secondary side to the primary side of
the separation membrane 11, which is opposite to the flow
of filtered water. This makes it possible to effectively
clean and remove pollutants from the separation membrane 11.
25 After the membrane permeation differential pressure and
flux of the separation membrane 11 are recovered by the
membrane cleaning process, the membrane filtration process
is resumed. According to this cleaning method, switching
between the membrane filtration process and the membrane
30 cleaning process can be performed at a desired timing with
the separation membrane 11 immersed in the water to be
treated in the treatment tank 10, and the retention of
filtration performance and the simplification of
9
maintenance of the water treatment apparatus can be
realized.
[0017] The process transition between the membrane
filtration process and the membrane cleaning process will
5 be described in detail. The membrane state measurement
unit 20 measures the state of contamination of the
separation membrane 11, and outputs the measured value to
the process control unit 22. For example, the membrane
state measurement unit 20 measures the membrane permeation
10 differential pressure and/or flux of the separation
membrane 11. The process control unit 22 compares the
measured value with a threshold stored in a storage unit
inside the process control unit 22, and determines whether
to perform the process transition based on the comparison
15 result. For example, in a case where the membrane state
measurement unit 20 measures the membrane permeation
differential pressure, the process control unit 22
determines to transition the process from the membrane
filtration process to the membrane cleaning process when
20 the measured value of the membrane permeation differential
pressure exceeds the threshold, and instructs the switching
valve 21 to connect the filtered water pipe 2a to the
membrane cleaning pipe 3d. Then, when the measured value
of the membrane permeation differential pressure falls
25 below the threshold, the process control unit 22 determines
to transition the process from the membrane cleaning
process to the membrane filtration process, and instructs
the switching valve 21 to connect the filtered water pipe
2a to the discharge pipe 2b. In a case where the membrane
30 state measurement unit 20 measures the flux, the process
control unit 22 transitions the process from the membrane
filtration process to the membrane cleaning process when
the measured value of the flux falls below the threshold,
10
and transitions the process from the membrane cleaning
process to the membrane filtration process when the
measured value exceeds the threshold.
[0018] Note that the threshold for determining the
5 process transition from the membrane cleaning process to
the membrane filtration process and the threshold for
determining the process transition from the membrane
filtration process to the membrane cleaning process may
differ. For example, in a case where the membrane state
10 measurement unit 20 measures the membrane permeation
differential pressure, the threshold for determining the
process transition from the membrane cleaning process to
the membrane filtration process may be set to a value
smaller than the threshold for determining the process
15 transition from the membrane filtration process to the
membrane cleaning process. In a case where the membrane
state measurement unit 20 measures the flux, the threshold
for determining the process transition from the membrane
cleaning process to the membrane filtration process may be
20 set to a value larger than the threshold for determining
the process transition from the membrane filtration process
to the membrane cleaning process. In a case where the
membrane state measurement unit 20 measures both the
membrane permeation differential pressure and flux of the
25 separation membrane 11, the process control unit 22 may
perform the process transition when either the membrane
permeation differential pressure or the flux satisfies the
process transition condition, or may perform the process
transition when both satisfy the process transition
30 condition.
[0019] As described above, by repeating the process
transition according to the measured value from the
membrane state measurement unit 20, the treatment of the
11
water to be treated can be continued without impairing a
desired filtration performance. The process transition
between the membrane filtration process and the membrane
cleaning process is not limited to the example described
5 above. For example, membrane cleaning may be periodically
performed by conducting the membrane cleaning process for a
certain period of time from when the operating time of the
membrane filtration process exceeds a predetermined time,
and then making the transition to the membrane filtration
10 process again and resetting the operating time. In this
case, the interval of performing the membrane filtration
process and the duration of the membrane cleaning process
may be changeable.
[0020] Next, the configuration and operation of the
15 ozone water production apparatus 100 will be described.
The ozone water production apparatus 100 includes an oxygen
gas supply unit 30, an other gas supply unit 31, an ozone
gas generation unit 32, an ozone water generation unit 34,
an ozone water state measurement unit 35, an ozone water
20 feed pump 36, a condition control unit 37, and a waste
ozone treatment apparatus 38.
[0021] The oxygen gas supply unit 30 is a first gas
supply unit that supplies oxygen gas, an example of a first
gas, to the ozone gas generation unit 32 via an oxygen gas
25 pipe 3a. The other gas supply unit 31 is a second gas
supply unit that supplies other gas, or a second gas, to
the ozone gas generation unit 32 via an other gas pipe 3b.
Other gas is, for example, carbon dioxide gas. Hereinafter,
an example in which carbon dioxide gas is used as other gas
30 will be described. However, other gas is not limited to
carbon dioxide gas, and may be nitrogen gas, nitrogen oxide
gas, or any other gas containing at least one of carbon
dioxide gas, nitrogen gas, and nitrogen oxide gas.
12
[0022] The oxygen gas supply unit 30 and the other gas
supply unit 31 are connected to the ozone gas generation
unit 32 via the oxygen gas pipe 3a and the other gas pipe
3b, respectively. Oxygen gas and other gas are supplied to
5 the ozone gas generation unit 32 via the oxygen gas pipe 3a
and the other gas pipe 3b. The ozone gas generation unit
32 generates ozone through electric discharge treatment
such as dielectric barrier discharge using oxygen gas and
other gas. That is, the ozone gas generation unit 32 is an
10 electric discharge unit that generates a third gas
containing ozone gas by performing electric discharge
treatment on a gas containing the first gas supplied by the
first gas supply unit and the second gas supplied by the
second gas supply unit. In the ozone gas generation unit
15 32, oxygen molecules are dissociated by the action of
electric discharge, and ozone is generated from the
dissociated oxygen atoms and oxygen molecules. Here, in
the ozone gas generation unit 32, carbon dioxide is
dissociated simultaneously in the same manner as oxygen
20 molecules are dissociated. Therefore, the third gas that
is the gas generated by the ozone gas generation unit 32
contains not only ozone but also a carbonate-based byproduct derived from carbon dioxide. Hereinafter, for the
sake of simplicity, the gas generated by the ozone gas
25 generation unit 32 is referred to as ozone gas, and as
described above, this ozone gas contains a carbonate-based
by-product.
[0023] The ozone gas generated by the ozone gas
generation unit 32 is supplied to the ozone water
30 generation unit 34 via an ozone gas pipe 3c. In addition,
solvent water is supplied to the ozone water generation
unit 34 via a solvent water pipe 3e. The ozone water
generation unit 34 stores the supplied solvent water. The
13
ozone water generation unit 34 includes an ozone injection
unit 33, and the ozone injection unit 33 generates ozone
water by dissolving the third gas generated by the ozone
gas generation unit 32 as described above in solvent water.
5 The ozone gas supplied via the ozone gas pipe 3c is
introduced into the solvent water. Consequently, ozone gas
is dissolved in the solvent water, and ozone water is
generated. The ozone water generated and stored by the
ozone gas generation unit 32 is supplied to the separation
10 membrane 11 to be cleaned via the ozone water feed pump 36
and the membrane cleaning pipe 3d. That is, the ozone
water by the ozone gas generation unit 32 is used as a
cleaning agent for cleaning the separation membrane 11.
Meanwhile, the ozone gas that has not been dissolved is
15 introduced into the waste ozone treatment apparatus 38 via
a waste ozone gas pipe 3f. The waste ozone treatment
apparatus 38 detoxifies the ozone gas and releases it to
the atmosphere.
[0024] The pH of ozone water generated and stored in the
20 ozone water generation unit 34 is preferably maintained at
six or less, and more preferably maintained within the
range of three to five in order to reduce the selfdecomposition of dissolved ozone. Hereinafter, a condition
for keeping ozone water acidic is referred to as an acidic
25 condition. The acidic condition may be a condition that
the pH is six or less as described above, or may be a
condition that the pH is within a predetermined range. The
predetermined range is, for example, but not limited to,
the range of three to five, that is, the range in which the
30 pH is three to five.
[0025] Carbonate-based by-products such as carbonate
ions and bicarbonate ions contained in the ozone gas
supplied from the ozone gas generation unit 32 lower the pH
14
of solvent water; therefore, the pH of ozone water
according to the present embodiment depends on how much
carbonate-based by-products are dissolved in solvent water
together with ozone gas. Therefore, the pH of ozone water
5 can be controlled by controlling the supply of carbon
dioxide from the other gas supply unit 31. Specifically,
by controlling the supply of carbon dioxide from the other
gas supply unit 31 so as to maintain the acidic condition,
the dissolution of carbonate-based by-products can be
10 controlled, the self-decomposition of dissolved ozone is
reduced, the life of dissolved ozone is prolonged, and the
dissolved ozone concentration is improved. Carbonate-based
by-products also act as radical scavengers that scavenge
hydroxyl radicals generated by the decomposition of ozone
15 in water. That is, carbonate-based by-products react with
hydroxyl radicals to inhibit the progress of ozone
decomposition reactions.
[0026] The temperature of the ozone water generation
unit 34 may be room temperature, but is preferably
20 maintained at 30°C or lower, and more preferably at 20°C or
lower, whereby the effect of reducing the selfdecomposition of dissolved ozone due to the retention of
low temperature can be obtained in addition to that of
reducing the self-decomposition of dissolved ozone due to
25 the retention of the above-described acidic condition.
Thus, the ozone water produced by the ozone water
production apparatus 100 according to the present
embodiment has stabilized, highly-concentrated, and longlived dissolved ozone in ozone water owing to the
30 carbonate-based by-products supplied from the ozone gas
generation unit 32.
[0027] The ozone water state measurement unit 35
measures an amount indicating a state related to the pH of
15
ozone water. The amount indicating a state related to the
pH of ozone water may be the pH itself of ozone water or
may be the dissolved ozone concentration. That is, the
ozone water state measurement unit 35 may measure the pH of
5 ozone water or may measure the dissolved ozone
concentration of ozone water. In FIG. 1, the ozone water
state measurement unit 35 is provided in the ozone water
generation unit 34, but the position of the ozone water
state measurement unit 35 is not limited to the position
10 indicated in FIG. 1, and the ozone water state measurement
unit 35 may be provided in the membrane cleaning pipe 3d.
[0028] The condition control unit 37 controls the
production of ozone water in cooperation with the process
control unit 22. As described above, the process control
15 unit 22 controls the process transition. The process
control unit 22 notifies the condition control unit 37 of
the start of the membrane cleaning process when
transitioning to the membrane cleaning process, and
notifies the condition control unit 37 of the start of the
20 membrane filtration process when completing the membrane
cleaning process and transitioning to the membrane
filtration process. In response to being notified of the
start of the membrane cleaning process, the condition
control unit 37 starts to produce and feed ozone water.
25 Specifically, as will be described later, the condition
control unit 37 controls the oxygen gas supply unit 30, the
other gas supply unit 31, and the ozone gas generation unit
32 based on various conditions for producing ozone water so
that ozone water is produced, and drives the ozone water
30 feed pump 36 so that ozone water is fed. The ozone water
fed by the ozone water feed pump 36 is supplied to the
separation membrane 11 via the membrane cleaning pipe 3d,
the switching valve 21, and the filtered water pipe 2a. In
16
response to being notified of the start of the membrane
filtration process after the membrane cleaning process, the
condition control unit 37 may stop the production of ozone
water and the feeding of ozone water, or may continue the
5 production of ozone water and stop the feeding of ozone
water. If the production of ozone water is continued in
the membrane filtration process, the produced ozone water
is stored in the ozone water generation unit 34, and when
being notified of the start of the membrane filtration
10 process again, the condition control unit 37 drives the
ozone water feed pump 36 to start to feed ozone water. If
the production of ozone water is continued in the membrane
filtration process, the condition control unit 37 may stop
the production of ozone water when, for example, the amount
15 of stored ozone water reaches a threshold.
[0029] As described above, the condition control unit 37
that controls the production of ozone water and the process
control unit 22 that controls the process according to the
state of the separation membrane 11 independently perform
20 different controls while performing control in cooperation
with each other, whereby a water treatment apparatus which
has a high degree of freedom and is advantageous in terms
of running cost can be realized.
[0030] The condition control unit 37 is implemented by
25 processing circuitry. The processing circuitry may be
dedicated hardware, or may be a control circuit including a
processor. In a case where the processing circuitry is
dedicated hardware, the processing circuitry is, for
example, a single circuit, a composite circuit, a
30 programmed processor, a parallel programmed processor, an
application specific integrated circuit (ASIC), a field
programmable gate array (FPGA), or a combination thereof.
[0031] FIG. 2 is a diagram illustrating an exemplary
17
configuration of a control circuit according to the present
embodiment. The processing circuitry that implements the
condition control unit 37 may be, for example, the control
circuit illustrated in FIG. 2. The control circuit
5 illustrated in FIG. 2 includes a processor 201 and a memory
202.
[0032] The processor 201 which is an arithmetic device
is exemplified by a central processing unit (CPU), a
graphics processing unit (GPU), a microprocessor, a
10 microcontroller, or a digital signal processor (DSP). The
memory 202 which is a storage unit is exemplified by a
semiconductor memory such as a random access memory (RAM),
a read only memory (ROM), a flash memory, an erasable
programmable read only memory (EPROM), and an electrically
15 erasable programmable read only memory (EEPROM, registered
trademark), a magnetic disk, or a flexible disk.
[0033] In a case where the condition control unit 37 is
implemented by the control circuit illustrated in FIG. 2,
the function of the condition control unit 37 is
20 implemented by software, firmware, or a combination of
software and firmware. Software and firmware are described
as a program and stored in the memory 202, and the function
of the condition control unit 37 is implemented by the
processor 201 reading and executing the program stored in
25 the memory 202. In addition, when information is recorded
during the execution of the program by the processor 201,
data is held in the memory 202. This program may be
provided by a program storage medium which is a storage
medium, or may be provided by a communication medium or the
30 like.
[0034] In addition, the condition control unit 37 may be
implemented by a combination of processing circuitry which
is dedicated hardware and the control circuit illustrated
18
in FIG. 2. Note that the process control unit 22 described
above is also implemented by processing circuitry similarly
to the condition control unit 37, and this processing
circuitry may be dedicated hardware, a control circuit
5 including a processor, or a combination thereof.
[0035] Next, the control of the condition control unit
37 will be described in detail. The condition control unit
37 is a control unit that controls the generation amount of
a by-product that is obtained through electric discharge
10 treatment on other gas such as carbon dioxide.
Specifically, when producing ozone water, the condition
control unit 37 controls each unit of the ozone water
production apparatus 100 so as to satisfy various
conditions related to the production of ozone water. The
15 various conditions include the acidic condition described
above. The various conditions include a gas condition and
an electric discharge condition in addition to the acidic
condition. Based on the target value of the dissolved
ozone concentration in the ozone water to be produced, the
20 condition control unit 37 determines the gas condition and
the electric discharge condition such that the pH
corresponding to the measured value from the ozone water
state measurement unit 35 described above satisfies the
acidic condition.
25 [0036] The gas condition is a condition which is related
to the gas flow rate value of oxygen gas and/or carbon
dioxide gas and determines the proportion of carbon dioxide
gas in the source gas. For example, the proportion of
carbon dioxide gas in the source gas may be increased or
30 reduced by keeping the flow rate of oxygen gas constant and
increasing or reducing the flow rate of carbon dioxide gas,
or the proportion of carbon dioxide gas in the source gas
may be increased or reduced by keeping the flow rate of
19
carbon dioxide gas constant and increasing or reducing the
flow rate of oxygen gas. In addition, the proportion of
carbon dioxide gas in the source gas may be increased or
reduced by increasing or reducing the flow rates of both
5 oxygen gas and carbon dioxide gas. Although the amount of
dissolved ozone can be increased by adjusting the electric
discharge power and the oxygen gas flow rate as appropriate,
in the present embodiment, dissolved ozone can be increased
by increasing the flow rate of carbon dioxide gas while
10 supplying a constant amount of oxygen gas.
[0037] The electric discharge condition is at least one
of gas pressure, temperature, current, voltage, and
electric discharge power in the electric discharge
treatment. That is, the electric discharge condition
15 indicates at least one of the gas pressure of the discharge
field which is the ozone gas generation field in the
electric discharge treatment of the ozone gas generation
unit 32, the current applied to the discharge field, the
electric discharge power based on the voltage, and the
20 temperature of the discharge field. For example, by
adjusting the electric discharge power, the gas pressure,
and the temperature of the discharge field in the ozone gas
generation unit 32, the dissociation amount of carbon
dioxide can be controlled, and the generation amount of
25 carbonate-based by-products can be adjusted. Note that the
temperature of the discharge field can be controlled by the
electric discharge power and/or the temperature of the
cooling water supplied to the ozone gas generation unit 32.
[0038] The pH of ozone water depends on the generation
30 amount of carbonate-based by-products. The generation
amount of carbonate-based by-products depends on the flow
rate of carbon dioxide gas supplied from the other gas
supply unit 31 and also depends on the electric discharge
20
condition. Therefore, the acidic condition can be
maintained by appropriately setting the gas condition and
the electric discharge condition.
[0039] The conditions for adjusting the generation
5 amount of carbonate-based by-products so as to maintain the
acidic condition are not limited to the above-described
examples. For example, by adjusting a plurality of gas
conditions and electric discharge conditions in combination,
it is possible to control the generation amount of
10 carbonate-based by-products which are by-products of
generating ozone gas while maintaining a desired generation
amount of ozone.
[0040] The pH range corresponding to the acidic
condition is stored in, for example, a storage unit in the
15 condition control unit 37. For example, the condition
control unit 37 determines the gas condition such that the
supply amount of carbon dioxide gas from the other gas
supply unit 31 increases when the pH corresponding to the
measured value from the ozone water state measurement unit
20 35 exceeds the upper limit value of the proper range
defined in the acidic condition, and controls the flow rate
in the other gas supply unit 31 based on the determined gas
condition. Consequently, the generation amount of
carbonate-based by-products can be increased, and the pH of
25 ozone water can be lowered. Such proper control of the pH
of ozone water results in stabilized, highly-concentrated,
and long-lived dissolved ozone in ozone water. In addition,
the condition control unit 37 determines the gas conditions
such that the supply amount of carbon dioxide gas from the
30 other gas supply unit 31 is reduced when the pH
corresponding to the measured value from the ozone water
state measurement unit 35 falls below the lower limit value
of the proper range defined in the acidic condition, and
21
controls the flow rate in the other gas supply unit 31
based on the determined gas condition. Consequently, the
generation amount of carbonate-based by-products can be
reduced, and the pH of ozone water can be increased. Note
5 that only the upper limit value may be defined as the
acidic condition, in which case the control of reducing the
supply amount of carbon dioxide gas need not be performed.
[0041] In a case where the ozone water state measurement
unit 35 measures the dissolved ozone concentration, the
10 range of dissolved ozone concentrations corresponding to
the proper range of pH defined as the acidic condition is
determined. The condition control unit 37 stores this
range of dissolved ozone concentrations in the storage unit,
and in the same manner as above, increases the supply
15 amount of carbon dioxide gas from the other gas supply unit
31 to increase the generation amount of carbonate-based byproducts when the measured value of the dissolved ozone
concentration is lower than the lower limit value of the
stored range. Consequently, it is possible to obtain
20 stabilized, highly-concentrated, and long-lived dissolved
ozone in ozone water. When the dissolved ozone
concentration is higher than the upper limit value of the
stored range, the supply amount of carbon dioxide gas from
the other gas supply unit 31 is reduced to reduce the
25 generation amount of carbonate-based by-products. Note
that only the upper limit value may be defined as the
acidic condition, in which case only the lower limit value
is defined as the range of dissolved ozone concentrations,
and thus the control of reducing the supply amount of
30 carbon dioxide gas need not be performed. In this manner,
the condition control unit 37 can control the generation
amount of carbonate-based by-products by adjusting the flow
rate of other gas supplied from the other gas supply unit
22
31.
[0042] In addition, the condition control unit 37 may
control the generation amount of carbonate-based byproducts by adjusting the electric discharge condition in
5 the electric discharge treatment, or may control the
generation amount of carbonate-based by-products by
combining the adjustment of the flow rate of other gas
supplied from the other gas supply unit 31 and the
adjustment of the electric discharge condition. As
10 described above, the condition control unit 37 controls the
generation amount of carbonate-based by-products such that
the measured value from the ozone water state measurement
unit 35 lies within a predetermined range.
[0043] Thus, the ozone water production method according
15 to the present embodiment includes a first gas supply step
of supplying oxygen gas and a second gas supply step of
supplying other gas. The ozone water production method
further includes an electric discharge step of generating a
gas containing ozone gas by performing electric discharge
20 treatment on a gas containing the oxygen gas supplied in
the first gas supply step and the other gas supplied in the
second gas supply step, and an ozone water generation step
of generating ozone water by dissolving the gas generated
in the electric discharge step in solvent water.
25 [0044] FIG. 3 is a flowchart illustrating an exemplary
procedure for controlling ozone water production in the
condition control unit 37 according to the present
embodiment. The processing illustrated in FIG. 3 is
started in a state where ozone water is not produced. The
30 condition control unit 37 determines whether to start the
production of ozone water (step S1), and in response to
determining not to start the production of ozone water (No
in step S1), repeats step S1. The condition control unit
23
37 determines to start the production of ozone water, for
example, when being notified by the process control unit 22
of the start of the membrane cleaning process. When the
production of ozone water is started in response to the
5 notification of the start of the membrane cleaning process
from the process control unit 22, the condition control
unit 37 also starts to feed ozone water by driving the
ozone water feed pump 36. Note that the condition control
unit 37 may start the production of ozone water
10 periodically, for example, regardless of the notification
of the start of each process from the process control unit
22. In this case, the produced ozone water is stored in
the ozone water generation unit 34. In response to being
notified of the start of the membrane filtration process,
15 the condition control unit 37 starts to feed ozone water by
driving the ozone water feed pump 36.
[0045] In response to determining to start the
production of ozone water (Yes in step S1), the condition
control unit 37 determines whether a measured value is
20 above a proper range (step S2). The measured value is a
result measured by the ozone water state measurement unit
35. This example assumes that the ozone water state
measurement unit 35 measures pH. This example also assumes
that the upper limit value and the lower limit value of pH
25 are defined as the proper range, and in step S2,
specifically, the condition control unit 37 determines
whether the measured value exceeds the upper limit value of
the proper range.
[0046] In response to determining that the measured
30 value is not above the proper range (No in step S2), the
condition control unit 37 determines whether the measured
value is below the proper range (step S3). Specifically,
the condition control unit 37 determines whether the
24
measured value is below the lower limit value of the proper
range. In response to determining that the measured value
is not below the proper range (No in step S3), the
condition control unit 37 determines whether to stop the
5 production of ozone water (step S4). For example, the
condition control unit 37 determines to stop the production
of ozone water when being notified by the process control
unit 22 of the start of the membrane filtration process.
As described above, the production of ozone water may be
10 continued even after the notification of the start of the
membrane filtration process, in which case the condition
control unit 37 stops the production of ozone water with a
trigger different from the notification of the start of the
membrane filtration process, for example, stops the
15 production of ozone water when the storage amount of ozone
water exceeds a threshold. In response to determining not
to stop the production of ozone water (No in step S4), the
condition control unit 37 returns to step S2.
[0047] In response to determining that the measured
20 value is above the proper range (Yes in step S2), the
condition control unit 37 increases the generation amount
of by-products associated with the generation of ozone gas
(step S5), and advances the processing to step S4. The
generation amount of by-products associated with the
25 generation of ozone gas indicates the generation amount of
by-products with respect to the generation amount of ozone
gas generated at the time of generating ozone gas. In step
S5, the condition control unit 37 adjusts the gas condition
so as to increase the generation amount of by-products
30 associated with the generation of ozone gas, for example,
by increasing the flow rate of carbon dioxide gas supplied
from the other gas supply unit 31. In addition, the
condition control unit 37 may increase the generation
25
amount of by-products associated with the generation of
ozone gas by adjusting the electric discharge condition, or
may increase the generation amount of by-products
associated with the generation of ozone gas by adjusting
5 both the gas condition and the electric discharge condition.
[0048] In response to determining that the measured
value is below the proper range (Yes in step S3), the
condition control unit 37 reduces the generation amount of
by-products associated with the generation of ozone gas
10 (step S6), and advances the processing to step S4. In step
S6, as in step S5, the condition control unit 37 may adjust
the gas condition, may adjust the electric discharge
condition, or may adjust both the gas condition and the
electric discharge condition.
15 [0049] In response to determining to stop the production
of ozone water (Yes in step S4), the condition control unit
37 ends the processing. After the end of the processing,
the processing illustrated in FIG. 3 is performed again.
Note that in a case where the ozone water state measurement
20 unit 35 measures the dissolved ozone concentration, the
condition control unit 37 only needs to determine in step
S2 whether the measured value is below the lower limit
value of the range of dissolved ozone concentrations
corresponding to the proper range of pH, and determine in
25 step S3 whether the measured value is above the upper limit
value of the range of dissolved ozone concentrations.
[0050] Through the above processing, the pH of the ozone
water produced by the ozone water production apparatus 100
is controlled by the dissolution of carbonate ions and
30 bicarbonate ions supplied from the ozone gas generation
unit 32, so that the acidic condition can be maintained.
By maintaining the pH of ozone water to satisfy the acidic
condition, the self-decomposition of dissolved ozone is
26
reduced, the life of dissolved ozone is prolonged, and the
dissolved ozone concentration is improved. Products of
reaction with carbonate-based by-products also act as
radical scavengers that scavenge hydroxyl radicals
5 generated by the decomposition of ozone in water. Thus, it
is possible to obtain stabilized, highly-concentrated, and
long-lived dissolved ozone in ozone water owing to the
products of reaction with carbonate-based by-products
supplied from the ozone gas generation unit 32.
10 [0051] In the example described above, the condition
control unit 37 dynamically controls the generation amount
of by-products such as carbonate-based by-products based on
the measured value from the ozone water state measurement
unit 35, but the method for controlling the generation
15 amount of by-products is not limited thereto. The gas
condition and/or the electric discharge condition may be
determined in advance so as to satisfy the acidic condition,
the oxygen gas supply unit 30 and the other gas supply unit
31 may respectively supply oxygen gas and other gas
20 according to the predetermined gas condition, and the ozone
gas generation unit 32 may perform the electric discharge
treatment according to the predetermined electric discharge
condition. The other gas supply unit 31 and the oxygen gas
supply unit 30 each include an adjustment unit that adjusts
25 the flow rate. In a case where the gas condition is
determined so as to satisfy the acidic condition, the
adjustment unit of the other gas supply unit 31 serves as a
control unit that controls the generation amount of byproducts. In a case where the electric discharge condition
30 is determined so as to satisfy the acidic condition, a
control unit that controls electric discharge in the ozone
gas generation unit 32 serves as a control unit that
controls the generation amount of by-products.
27
[0052] Although carbon dioxide gas is used as other gas
in the example described above, the same effect can be
obtained by using nitrogen or nitrogen oxide gas instead of
carbon dioxide as other gas. In the case of using nitrogen
5 or nitrogen oxide gas as other gas, the generation amount
of nitrate-based by-products generated simultaneously with
ozone through electric discharge is controlled so as to
maintain the acidic condition. Consequently, the pH of
ozone water is controlled by the dissolution of nitrate
10 ions supplied from the ozone gas generation unit 32, and
acts to maintain the acidic condition. By maintaining the
pH of ozone water at the acidic condition, the selfdecomposition of dissolved ozone is reduced, the life of
dissolved ozone is prolonged, and the dissolved ozone
15 concentration is improved. Nitrate-based by-products or
products of reaction with nitrate-based by-products also
act as radical scavengers that scavenge hydroxyl radicals
generated by the decomposition of ozone in water. Thus, it
is possible to obtain stabilized, highly-concentrated, and
20 long-lived dissolved ozone in ozone water owing to the
nitrate-based by-products or products of reaction with
nitrate-based by-products supplied from the ozone gas
generation unit 32. In addition, a mixed gas obtained by
mixing two or more of carbon dioxide, nitrogen, and
25 nitrogen oxide may be used as other gas. Therefore, other
gas only needs to contain at least one of carbon dioxide
gas, nitrogen gas, and nitrogen oxide gas. In a case where
a mixed gas is used as other gas, for example, a mixed gas
having 0.1% or more carbon dioxide with respect to the
30 oxygen flow rate can be used. In a case where a mixed gas
is used as other gas, the generation amount of nitratebased and carbonate-based by-products generated
simultaneously with ozone through electric discharge is
28
controlled so as to maintain the acidic condition.
[0053] Instead of oxygen, a first gas containing oxygen
such as air may be supplied to the ozone gas generation
unit 32, and the same effect can be obtained. That is, the
5 oxygen gas supply unit 30 as the first gas supply unit
supplies the first gas containing oxygen gas. In this case,
the generation amount of nitrate-based and carbonate-based
by-products generated simultaneously with ozone through
electric discharge is controlled so as to maintain the
10 acidic condition. Consequently, the pH of ozone water is
controlled by the dissolution of nitrate ions, carbonate
ions, bicarbonate ions, and the like supplied from the
ozone gas generation unit 32, and acts to maintain the
acidic condition. In the case of using air as the first
15 gas, nitrate-based by-products are generated from nitrogen
in the air, and thus no second gas needs to be used. That
is, in this case, the air serves as both the first gas and
the second gas. By maintaining the pH of ozone water at
the acidic condition, the self-decomposition of dissolved
20 ozone is reduced, the life of dissolved ozone is prolonged,
and the dissolved ozone concentration is improved.
Nitrate-based by-products or products of reaction with
nitrate-based by-products and carbonate-based by-products
also act as radical scavengers that scavenge hydroxyl
25 radicals generated by the decomposition of ozone in water.
Thus, it is possible to obtain stabilized, highlyconcentrated, and long-lived dissolved ozone in ozone water
owing to the nitrate-based by-products or products of
reaction with nitrate-based by-products and carbonate-based
30 by-products supplied from the ozone gas generation unit 32.
[0054] According to the present embodiment, the life of
dissolved ozone in generated ozone water can be prolonged.
Note that the life of dissolved ozone is shorter than the
29
life of ozone gas. Therefore, the distance by which ozone
water is transported is preferably short, and the ozone
water generation unit 34 is preferably located near the
separation membrane 11 to be cleaned. By placing the ozone
5 water generation unit 34 near the separation membrane 11,
the self-decomposition of ozone can be further reduced so
that highly efficient supply of ozone can be achieved.
Specifically, for example, the ozone water generation unit
34 is placed such that the distance for transporting ozone
10 water is shorter than the distance for transporting ozone
in a gas state. For example, by setting the length of the
ozone gas pipe 3c illustrated in FIG. 1 longer than the
total length of the membrane cleaning pipe 3d and the
filtered water pipe 2a, the distance for transporting ozone
15 water can be relatively reduced.
[0055] In the ozone gas generation unit 32, if the
oxygen gas purity in the source gas is 99% or more, highefficiency generation of ozone gas cannot be achieved. In
this case, by adding at least one of carbon dioxide,
20 nitrogen, or nitrogen oxide gas in trace amounts relative
to oxygen gas to the source gas, the electric discharge
state or the chemical reaction state is optimized so that
high-efficiency generation of ozone gas can be maintained.
That is, the addition of other gas to the source gas in the
25 present embodiment greatly contributes not only to
obtaining stabilized, highly-concentrated, and long-lived
dissolved ozone in generated ozone water but also to
enhancing the efficiency of the ozone gas generation unit
32.
30 [0056] As described above, it is possible to optimally
control the pH of ozone water by using carbonate-based byproducts or nitrate-based by-products produced at the time
of ozone gas production, and adjusting the gas condition or
30
the electric discharge condition in ozone gas generation
according to the measured value of pH or the measured value
of dissolved ozone concentration of the generated ozone
water. This results in stabilized, highly-concentrated,
5 and long-lived ozone water which is thus generated with
high efficiency, and a desired amount of ozone can be very
easily provided as ozone water for separation membrane
cleaning without causing an increase in size and complexity
of the ozone water production apparatus. In a case where
10 three fluids of solvent water, ozone gas, and acid or
alkali are individually adjusted and dissolved such that a
desired pH can be obtained, it takes time and effort to
individually adjust the three fluids. In contrast, in the
present embodiment, a desired pH is obtained by adjusting
15 two types of fluids, namely a mixed gas (e.g. ozone gas and
carbonate-based gas) which has been adjusted by the ozone
gas generation unit 32 and solvent water, and thus it is
possible to control the pH with less time and effort than
in the case of individually adjusting three fluids.
20 [0057] Second Embodiment.
FIG. 4 is a diagram illustrating an exemplary
configuration of a water treatment apparatus according to
the second embodiment. The water treatment apparatus
according to the present embodiment includes a regulating
25 valve 25 and a solvent water storage tank 26 in addition to
the components of the water treatment apparatus according
to the first embodiment. Components having the same
functions as those in the first embodiment are denoted by
the same reference signs as those in the first embodiment,
30 and explanations overlapping with those in the first
embodiment are omitted. Hereinafter, differences from the
first embodiment will be mainly described.
[0058] In the present embodiment, the discharge pipe 2b
31
is equipped with the regulating valve 25, and the discharge
pipe 2b is connected to the solvent water storage tank 26
via the regulating valve 25. The solvent water storage
tank 26 is connected to the solvent water pipe 3e for
5 supplying solvent water to the ozone water generation unit
34. Note that the water treatment apparatus may not
include the solvent water storage tank 26.
[0059] In the membrane filtration process, as described
in the first embodiment, filtered water flows through the
10 discharge pipe 2b via the filtered water pump 23. In the
present embodiment, the process control unit 22 also
controls the regulating valve 25. In the membrane
filtration process, the process control unit 22 controls
the regulating valve 25 such that at least part of the
15 filtered water flows toward the solvent water pipe 3e. The
filtered water that has passed through the discharge pipe
2b and the regulating valve 25 is stored as solvent water
in the solvent water storage tank 26. The solvent water
stored in the solvent water storage tank 26 is supplied to
20 the ozone water generation unit 34 via the solvent water
pipe 3e. In the absence of the solvent water storage tank
26, the filtered water that has passed through the
discharge pipe 2b and the regulating valve 25 is supplied
to the ozone water generation unit 34 via the solvent water
25 pipe 3e. Thus, in the present embodiment, solvent water is
filtered water filtered by the separation membrane 11.
[0060] Except for the above-described differences, the
operation according to the present embodiment is the same
as that in the first embodiment. The present embodiment
30 achieves the same effect as the first embodiment, and can
also reduce the running cost of solvent water by using
filtered water as solvent water, as compared with the case
of using tap water or the like as solvent water. In
32
addition, in the present embodiment, the water treatment
apparatus can be located even in a place with no tap water
supply source nearby. In addition, it is not necessary to
construct a long-distance pipe for introducing tap water to
5 the water treatment apparatus located in a place with no
tap water supply source nearby, which is economical. In
some cases, filtered water contains more organic substances
than tap water, and it is considered that ozone is partly
consumed for the decomposition of organic substances
10 contained in solvent water at the time of generating ozone
water. However, in the present embodiment, the amount of
ozone consumed by the decomposition of organic substances
contained in solvent water is much smaller than the
ineffective consumption amount of ozone that can be cut by
15 reducing the self-decomposition due to the effect of
maintaining the pH of ozone water in a proper range and the
hydroxyl radical scavenging effect as in the first
embodiment, and the present embodiment can achieve the same
effect as the first embodiment.
20 [0061] Third Embodiment.
FIG. 5 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
according to the third embodiment. The water treatment
apparatus according to the present embodiment is the same
25 as the water treatment apparatus according to the first
embodiment except that the ozone water production apparatus
100a illustrated in FIG. 5 is provided instead of the ozone
water production apparatus 100 of the water treatment
apparatus according to the first embodiment. Components
30 having the same functions as those in the first embodiment
are denoted by the same reference signs as those in the
first embodiment, and explanations overlapping with those
in the first embodiment are omitted. Hereinafter,
33
differences from the first embodiment will be mainly
described.
[0062] In the present embodiment, ozone gas that has not
been dissolved in solvent water in the ozone water
5 generation unit 34 is reused. The ozone water production
apparatus 100a according to the present embodiment includes
a circulation fan 39 instead of the waste ozone treatment
apparatus 38 of the ozone water production apparatus 100
according to the first embodiment. Undissolved ozone gas
10 is discharged from the ozone water generation unit 34 to
the waste ozone gas pipe 3f as waste ozone gas, which is
then introduced into the ozone gas pipe 3c by the
circulation fan 39. In this manner, in the present
embodiment, the third gas that has not been dissolved in
15 solvent water in the ozone water generation unit 34 is
introduced into the ozone water generation unit 34.
[0063] The present embodiment achieves the same effect
as the first embodiment, and can also improve the ozone gas
use efficiency by adding the ozone gas that has not been
20 consumed in the ozone water generation unit 34 to the ozone
gas supplied from the ozone gas generation unit 32. Other
expected benefits include reduction of power consumption
related to ozone generation in the ozone gas generation
unit 32 and reduction of running costs such as the amount
25 of power used and the source gas cost.
[0064] Fourth Embodiment.
FIG. 6 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
according to the fourth embodiment. The water treatment
30 apparatus according to the present embodiment is the same
as the water treatment apparatus according to the first
embodiment except that the ozone water production apparatus
100b illustrated in FIG. 6 is provided instead of the ozone
34
water production apparatus 100 of the water treatment
apparatus according to the first embodiment. Components
having the same functions as those in the first embodiment
are denoted by the same reference signs as those in the
5 first embodiment, and explanations overlapping with those
in the first embodiment are omitted. Hereinafter,
differences from the first embodiment will be mainly
described.
[0065] The ozone water production apparatus 100b
10 according to the present embodiment includes an ozone gas
concentration storage unit 40 and a circulation fan 41 in
addition to the components of the ozone water production
apparatus 100 according to the first embodiment. In the
ozone water production apparatus 100b according to the
15 fourth embodiment, the ozone gas generated in the ozone gas
generation unit 32 is supplied to the ozone water
generation unit 34 through the ozone gas concentration
storage unit 40. The ozone gas concentration storage unit
40 which is an ozone gas separation unit separates ozone
20 and oxygen in the ozone gas generated by the ozone gas
generation unit 32. Ozone separated by the ozone gas
concentration storage unit 40 is introduced into the ozone
water generation unit 34 as concentrated ozone gas.
Meanwhile, oxygen separated by the ozone gas concentration
25 storage unit 40 is returned as recycled oxygen gas to the
oxygen gas pipe 3a via the circulation fan 41 and an oxygen
recycle pipe 3g. Consequently, oxygen separated by the
ozone gas concentration storage unit 40 is reused as part
of the source gas in the ozone gas generation unit 32.
30 [0066] The main component of the ozone gas concentration
storage unit 40 in the present embodiment is, for example,
an adsorption cylinder filled with an adsorbent such as
silica gel. In the adsorption cylinder, through
35
temperature and pressure control, ozone and oxygen are
separated from a mixed gas containing ozone by utilizing
the difference in adsorption and desorption characteristics
between ozone and oxygen with respect to the adsorbent.
5 The ozone purity and ozone concentration of concentrated
ozone gas can be changed by controlling the temperature and
the pressure based on a command from the condition control
unit 37. That is, the ozone purity and ozone concentration
of concentrated ozone gas can be optimally set by adjusting
10 a command from the condition control unit 37.
[0067] By placing a desorption pump downstream of the
ozone gas concentration storage unit 40 and introducing a
desorption gas into the ozone gas concentration storage
unit 40, the desorption of ozone from the adsorbent may be
15 promoted when concentrated ozone gas is taken out from the
ozone gas concentration storage unit 40. As the desorption
gas, part of the source gas for use in the ozone gas
generation unit 32 may be used. In addition, by placing an
ejector downstream of the ozone gas concentration storage
20 unit 40 and introducing air around the ozone water
production apparatus 100b into the ejector as a driving
fluid, concentrated ozone gas may be sucked.
[0068] The present embodiment achieves the same effect
as the first embodiment, and can also expect reduction of
25 power consumption related to ozone generation and reduction
of running costs such as the amount of power used and the
source gas cost, since by separating the ozone gas produced
in the ozone gas generation unit 32 into ozone and oxygen,
optimally concentrated ozone gas can be introduced into the
30 ozone water generation unit 34, and oxygen gas can be
recycled as the source gas in the ozone gas generation unit
32 again.
[0069] Fifth Embodiment.
36
FIG. 7 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
according to the fifth embodiment. The water treatment
apparatus according to the present embodiment is the same
5 as the water treatment apparatus according to the first
embodiment except that the ozone water production apparatus
100c illustrated in FIG. 7 is provided instead of the ozone
water production apparatus 100 of the water treatment
apparatus according to the first embodiment. Components
10 having the same functions as those in the first embodiment
are denoted by the same reference signs as those in the
first embodiment, and explanations overlapping with those
in the first embodiment are omitted. Hereinafter,
differences from the first embodiment will be mainly
15 described.
[0070] The ozone water production apparatus 100c
according to the present embodiment includes a circulation
pump 42 in addition to the components of the ozone water
production apparatus 100 according to the first embodiment.
20 In the ozone water production apparatus 100c according to
the present embodiment, solvent water stored in the ozone
water generation unit 34 is supplied from the lower part of
the ozone water generation unit 34 to the upper part of the
ozone water generation unit 34 via a circulation pipe 3h
25 and the circulation pump 42. In this manner, the
circulation pump 42 causes solvent water to circulate in
the order of the top of the ozone water generation unit 34,
the bottom of the ozone water generation unit 34, the
bottom of the circulation pipe 3h, the top of the
30 circulation pipe 3h, and the top of the ozone water
generation unit 34. Therefore, in the ozone water
generation unit 34, a flow of solvent water is generated
from the top to the bottom of the ozone water generation
37
unit 34. On the other hand, ozone gas introduced from the
ozone gas generation unit 32 flows from the bottom to the
top in the ozone water generation unit 34 via the ozone
injection unit 33. That is, in the ozone water generation
5 unit 34, solvent water and ozone gas are in countercurrent
contact with each other. Note that the circulation pump 42
only needs to be operated while ozone gas is introduced
from the ozone gas generation unit 32 into the ozone water
generation unit 34.
10 [0071] The present embodiment achieves the same effect
as the first embodiment, and also improves the ozone water
generation efficiency due to the countercurrent contact of
solvent water and ozone gas and the resulting improvement
in the efficiency of ozone gas dissolution in solvent water.
15 Another expected benefit is capacity reduction of the waste
ozone treatment apparatus 38 due to the improvement of the
ozone gas use efficiency in ozone water generation and the
resulting reduction in the amount of undissolved ozone gas.
[0072] Sixth Embodiment.
20 FIG. 8 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
according to the sixth embodiment. The water treatment
apparatus according to the present embodiment is the same
as the water treatment apparatus according to the first
25 embodiment except that the ozone water production apparatus
100d illustrated in FIG. 8 is provided instead of the ozone
water production apparatus 100 of the water treatment
apparatus according to the first embodiment. Components
having the same functions as those in the first embodiment
30 are denoted by the same reference signs as those in the
first embodiment, and explanations overlapping with those
in the first embodiment are omitted. Hereinafter,
differences from the first embodiment will be mainly
38
described.
[0073] The ozone water production apparatus 100d
according to the present embodiment includes an ejector 43
and a circulation pump 44 instead of the ozone injection
5 unit 33 according to the first embodiment. In the ozone
water production apparatus 100d according to the present
embodiment, the ozone gas generation unit 32 is connected
to the ejector 43 via the ozone gas pipe 3c. The ozone
water generation unit 34 is connected to a circulation pipe
10 3i forming a circulation flow path of solvent water
together with the ozone water generation unit 34. The
solvent water introduced into the ozone water generation
unit 34 circulates through the ozone water generation unit
34 and the circulation pipe 3i by means of the circulation
15 pump 44. The ejector 43 generates ozone water by
performing gas-liquid mixing and dissolution using solvent
water as a driving fluid and ozone gas as a suction fluid.
[0074] The present embodiment achieves the same effect
as the first embodiment, and also improves the ozone water
20 generation efficiency due to the gas-liquid mixing and
dissolution of solvent water and ozone gas by means of the
ejector 43 and the resulting improvement in the efficiency
of ozone gas dissolution in solvent water. Another
expected benefit is capacity reduction of the waste ozone
25 treatment apparatus 38 due to the improvement of the ozone
gas use rate in ozone water generation and the resulting
reduction in the amount of undissolved ozone gas.
[0075] Seventh Embodiment.
FIG. 9 is a diagram illustrating an exemplary
30 configuration of an ozone water production apparatus
according to the seventh embodiment. The water treatment
apparatus according to the present embodiment is the same
as the water treatment apparatus according to the first
39
embodiment except that the ozone water production apparatus
100e illustrated in FIG. 9 is provided instead of the ozone
water production apparatus 100 of the water treatment
apparatus according to the first embodiment. Components
5 having the same functions as those in the first embodiment
are denoted by the same reference signs as those in the
first embodiment, and explanations overlapping with those
in the first embodiment are omitted. Hereinafter,
differences from the first embodiment will be mainly
10 described.
[0076] The ozone water production apparatus 100e
according to the present embodiment includes an ozone water
generation unit 34a instead of the ozone water generation
unit 34 according to the first embodiment, and additionally
15 includes a circulation pump 46. The solvent water pipe 3e
and the ozone water generation unit 34a are connected to a
circulation pipe 3j forming a circulation flow path of
solvent water together with the ozone water generation unit
34a and the solvent water pipe 3e. The circulation pipe 3j
20 is equipped with the circulation pump 46. The solvent
water supplied from the solvent water pipe 3e circulates by
means of the circulation pump 46 through the flow path
formed by the ozone water generation unit 34a, the
circulation pipe 3j, and a part of the solvent water pipe
25 3e. The ozone water generation unit 34a is equipped with a
plurality of barriers 45 forming a plurality of flow paths
of solvent water in the vertical direction. The plurality
of barriers 45 are located away from the upper surface or
the bottom surface of the ozone water generation unit 34a
30 so that one continuous flow path is formed in the ozone
water generation unit 34a.
[0077] In the example illustrated in FIG. 9, the ozone
water generation unit 34a is divided into two regions by a
40
central barrier 45 provided in contact with the bottom of
the ozone water generation unit 34a, and the ozone
injection unit 33 is located at the bottom of each region.
The central barrier 45 and the upper surface of the ozone
5 water generation unit 34a are separated from each other, so
that solvent water can flow from the right region into the
left region. Each region has a barrier 45 located in
contact with the upper surface of the ozone water
generation unit 34a and away from the bottom surface of the
10 ozone water generation unit 34a. Consequently, as
illustrated in FIG. 9, each region is further divided into
two subdivision regions. The subdivision regions will be
referred to as first to fourth subdivision regions in order
from the left. In the example illustrated in FIG. 9,
15 solvent water is introduced from the top of the first
subdivision region of the ozone water generation unit 34a
via the solvent water pipe 3e, flows through the first
subdivision region from the top to the bottom, and flows
into the second subdivision region at the bottom. In the
20 second subdivision region, the solvent water flows from the
bottom to the top and flows into the third subdivision
region at the top. In the third subdivision region, the
solvent water flows from the top to the bottom and flows
into the fourth subdivision region at the bottom. The
25 solvent water that has flowed from the bottom to the top in
the fourth subdivision region flows into the circulation
pipe 3j connected to the top of the ozone water generation
unit 34a.
[0078] In the present embodiment, the circulation flow
30 path of solvent water is formed in this way, whereby a flow
of solvent water from the top to the bottom of the ozone
water generation unit 34 is generated. Since the ozone
injection unit 33 is located at the bottom of each region,
41
a flow of ozone gas from the bottom to the top of the ozone
water generation unit 34 is generated. Therefore, solvent
water and ozone gas are in counterflow contact with each
other. In the example illustrated in FIG. 9, the ozone
5 water generation unit 34a is divided into two regions, and
the ozone injection unit 33 is provided in each region.
However, the ozone water generation unit 34a may be divided
into three or more regions, and the ozone injection unit 33
may be provided in each region. In addition, the ozone
10 water generation unit 34a may include one barrier 45 placed
in contact with the upper surface of the ozone water
generation unit 34a and away from the bottom surface of the
ozone water generation unit 34a, and may include one ozone
injection unit 33.
15 [0079] In the present embodiment, a flow path of solvent
water is formed by the barriers 45 in the ozone water
generation unit 34a, so that solvent water and ozone gas
are in countercurrent contact with each other. Thus, the
present embodiment achieves the same effect as the first
20 embodiment, and also improves the ozone water generation
efficiency due to the improvement in the efficiency of
ozone gas dissolution in solvent water. Another expected
benefit is capacity reduction of the waste ozone treatment
apparatus 38 due to the improvement of the ozone gas use
25 efficiency in ozone water generation and the resulting
reduction in the amount of undissolved ozone gas.
[0080] Eighth Embodiment.
FIG. 10 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
30 according to the eighth embodiment. The water treatment
apparatus according to the present embodiment is the same
as the water treatment apparatus according to the first
embodiment except that the ozone water production apparatus
42
100f illustrated in FIG. 10 is provided instead of the
ozone water production apparatus 100 of the water treatment
apparatus according to the first embodiment. Components
having the same functions as those in the first embodiment
5 are denoted by the same reference signs as those in the
first embodiment, and explanations overlapping with those
in the first embodiment are omitted. Hereinafter,
differences from the first embodiment will be mainly
described.
10 [0081] The ozone water production apparatus 100f
according to the present embodiment includes a membrane
module 47 instead of the ozone water generation unit 34
according to the first embodiment. The membrane module 47
includes a porous membrane such as a porous glass membrane.
15 In the present embodiment, the ozone gas produced in the
ozone gas generation unit 32 and solvent water are
introduced into the membrane module 47. The membrane
module 47 generates ozone water by bringing the introduced
ozone gas into contact with the solvent water in the pores
20 of the porous membrane to dissolve the ozone gas in the
solvent water. Ozone water is introduced into the membrane
cleaning pipe 3d by the ozone water feed pump 36. In the
present embodiment, the ozone water state measurement unit
35 is located in the membrane cleaning pipe 3d.
25 [0082] The present embodiment achieves the same effect
as the first embodiment, and also improves the ozone water
generation efficiency due to the dissolution of ozone gas
in solvent water with the use of the membrane module 47 and
the resulting improvement in the efficiency of ozone gas
30 dissolution in solvent water. The ozone gas use efficiency
in ozone water generation is also improved.
[0083] Ninth Embodiment.
FIG. 11 is a diagram illustrating an exemplary
43
configuration of an ozone water production apparatus
according to the ninth embodiment. The water treatment
apparatus according to the present embodiment is the same
as the water treatment apparatus according to the first
5 embodiment except that the ozone water production apparatus
100g illustrated in FIG. 11 is provided instead of the
ozone water production apparatus 100 of the water treatment
apparatus according to the first embodiment. Components
having the same functions as those in the first embodiment
10 are denoted by the same reference signs as those in the
first embodiment, and explanations overlapping with those
in the first embodiment are omitted. Hereinafter,
differences from the first embodiment will be mainly
described.
15 [0084] The ozone water production apparatus 100g
according to the present embodiment additionally includes a
fine bubble generator unit 48 in the ozone water generation
unit 34 according to the first embodiment. In the present
embodiment, the ozone gas generated by the ozone gas
20 generation unit 32 is introduced into the fine bubble
generator unit 48. The fine bubble generator unit 48
introduces the introduced ozone gas as fine bubbles into
the ozone water generation unit 34 in which solvent water
is stored. The fine bubbles generated by the fine bubble
25 generator unit 48 have a bubble diameter of 100 μm or less,
and preferably are ultrafine bubbles with a bubble diameter
of 1 μm or less. The fine bubble generator unit 48 may
generate fine bubbles using any method, e.g. a pressurized
dissolution method, a swirling flow method, or a micropore
30 method, and there is no restriction on the way bubbles are
generated.
[0085] The present embodiment achieves the same effect
as the first embodiment, and also improves the ozone water
44
generation efficiency due to the introduction of ozone gas
as fine bubbles and the resulting improvement in the
efficiency of ozone gas dissolution in solvent water.
Another expected benefit is capacity reduction of the waste
5 ozone treatment apparatus 38 due to the improvement of the
ozone gas use efficiency in ozone water generation and the
resulting reduction in the amount of undissolved ozone gas.
In addition, ozone gas in the form of ultrafine bubbles
keeps floating in the solvent water in Brownian motion, and
10 thus does not rise due to buoyancy and disappear on the
liquid surface like bubbles having a large bubble diameter;
therefore, the life of ozone water is expected to be
prolonged.
[0086] Tenth Embodiment.
15 FIG. 12 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
according to the tenth embodiment. The water treatment
apparatus according to the present embodiment is the same
as the water treatment apparatus according to the first
20 embodiment except that the ozone water production apparatus
100h illustrated in FIG. 12 is provided instead of the
ozone water production apparatus 100 of the water treatment
apparatus according to the first embodiment. Components
having the same functions as those in the first embodiment
25 are denoted by the same reference signs as those in the
first embodiment, and explanations overlapping with those
in the first embodiment are omitted. Hereinafter,
differences from the first embodiment will be mainly
described.
30 [0087] The ozone water production apparatus 100h
according to the present embodiment additionally includes a
fine bubble generator unit 49 and a circulation pump 50 in
the ozone water generation unit 34 according to the first
45
embodiment. The ozone water generation unit 34 is
connected to a circulation pipe 3k forming a circulation
flow path of solvent water together with the ozone water
generation unit 34. The fine bubble generator unit 49 and
5 the circulation pump 50 are provided in the circulation
pipe 3k. In the present embodiment, solvent liquid
circulates through the circulation flow path by means of
the circulation pump 50. The ozone gas generated by the
ozone gas generation unit 32 is introduced into the fine
10 bubble generator unit 49 of the ejector type. The fine
bubble generator unit 49 generates fine bubbles using
solvent liquid as a driving fluid and ozone gas as a
suction fluid. Fine bubbles have a bubble diameter of 100
μm or less, and preferably are ultrafine bubbles with a
15 bubble diameter of 1 μm or less. Ozone water is generated
by dissolving fine bubbles in solvent water. Ozone water
is introduced from the ozone water generation unit 34 into
the membrane cleaning pipe 3d by means of the ozone water
feed pump 36.
20 [0088] The present embodiment achieves the same effect
as the first embodiment, and also improves the ozone water
generation efficiency due to the formation of fine bubbles
from ozone gas and the resulting improvement in the
efficiency of ozone gas dissolution in solvent water.
25 Another expected benefit is capacity reduction of the waste
ozone treatment apparatus 38 due to the improvement of the
ozone gas use rate in ozone water generation and the
resulting reduction in the amount of undissolved ozone gas.
In addition, ozone gas in the form of ultrafine bubbles
30 keeps floating in the solvent water in Brownian motion, and
thus does not rise due to buoyancy and disappear on the
liquid surface like bubbles having a large bubble diameter;
therefore, the life of ozone water is expected to be
46
prolonged.
[0089] Eleventh Embodiment.
FIG. 13 is a diagram illustrating an exemplary
configuration of an ozone water production apparatus
5 according to the eleventh embodiment. The water treatment
apparatus according to the present embodiment is the same
as the water treatment apparatus according to the first
embodiment except that the ozone water production apparatus
100i illustrated in FIG. 13 is provided instead of the
10 ozone water production apparatus 100 of the water treatment
apparatus according to the first embodiment. Components
having the same functions as those in the first embodiment
are denoted by the same reference signs as those in the
first embodiment, and explanations overlapping with those
15 in the first embodiment are omitted. Hereinafter,
differences from the first embodiment will be mainly
described.
[0090] In the ozone water production apparatus 100i
according to the present embodiment, the membrane cleaning
20 pipe 3d is equipped with a switching valve 53, and the
switching valve 53 is connected to an ozone water pipe 3m
connected to the ozone water generation unit 34 and a
sodium hypochlorite solution pipe 3n for supplying a sodium
hypochlorite solution. The ozone water pipe 3m is equipped
25 with the ozone water feed pump 36. The switching valve 53
switches the connection of the membrane cleaning pipe 3d
between the ozone water pipe 3m and the sodium hypochlorite
solution pipe 3n. The switching of the switching valve 53
is performed at a desired timing in the membrane cleaning
30 process. In this manner, in the present embodiment, the
cleaning agent to be supplied to the separation membrane 11
is switchable between ozone water and the sodium
hypochlorite solution, and the separation membrane 11 is
47
cleaned using both the sodium hypochlorite solution as a
first cleaning agent and ozone water as a second cleaning
agent. Note that the sodium hypochlorite solution is fed
from a sodium hypochlorite solution supply unit 51 to the
5 membrane cleaning pipe 3d via a pump 52 and the switching
valve 53. The solvent of the sodium hypochlorite solution
can be of any type, and the solvent of the sodium
hypochlorite solution may be solvent water obtained from a
branch of the solvent water pipe 3e. Ozone water is fed
10 from the ozone water generation unit 34 to the membrane
cleaning pipe 3d via the ozone water feed pump 36 and the
switching valve 53.
[0091] In the membrane cleaning in the present
embodiment, ozone water and the sodium hypochlorite
15 solution are used as two types of cleaning agents having
different oxidizing powers. For example, in the membrane
cleaning process, first, membrane cleaning is performed
with the sodium hypochlorite solution which is the first
cleaning agent having a relatively small oxidizing power,
20 and then membrane cleaning is performed using ozone water
which is the second cleaning agent having a relatively
large oxidizing power. Here, oxidizing power refers to a
standard oxidation-reduction potential measured at 25°C
using a hydrogen electrode. The oxidizing power of the
25 first cleaning agent is less than 2.0 V, whereas the
oxidizing power of the second cleaning agent is 2.0 V or
more.
[0092] The first cleaning agent is effective for
oxidative decomposition removal of easily decomposable
30 organic substances among the pollutants adhering and
sticking to the separation membrane 11. In the membrane
cleaning with the first cleaning agent, oxidative
decomposition removal is not achieved for hardly
48
decomposable organic substances, but an effect such as
reduction in adhesion to the membrane can be obtained
through chemical action of the first cleaning agent.
Applying the second cleaning agent after the effect of the
5 first cleaning agent is obtained makes the oxidative
decomposition effect on hardly decomposable organic
substances remarkable, allowing pollutants to be removed
from the separation membrane 11. Cleaning can be
implemented by administration of a very small amount of
10 cleaning agent, as compared with the case where hardly
decomposable organic substances are oxidatively decomposed
with the second cleaning agent alone.
[0093] The present embodiment achieves the same effect
as the first embodiment, and can also improve, in
15 particular, the efficiency of oxidative decomposition of
hardly decomposable organic substances in pollutants by
cleaning the separation membrane in two stages using two
types of cleaning agents having different oxidizing powers.
Thus, the amount of ozone water used can be reduced, and
20 reduction of power consumption related to ozone generation
in the ozone gas generation unit 32 and reduction of
running costs such as the source gas cost are expected.
Note that since the effect of improving the membrane
cleaning efficiency with the use of the two types of
25 cleaning agents is very large and the amount of ozone water
used is also reduced, the effect of cost reduction with the
use of the two types of cleaning agents is larger than the
cost increase associated with the use of the two types of
cleaning agents. In addition, in the event that a problem
30 occurs in the ozone gas generation unit 32 or the ozone
water generation unit 34 due to some influence and the
cleaning operation with ozone water is stopped, it is also
possible to perform cleaning with the sodium hypochlorite
49
solution as a backup measure, which contributes to ensuring
the redundancy of the ozone water production apparatus 100i.
[0094]
The configurations and operations described in the
5 above first to eleventh embodiments may be combined as
appropriate. For example, the configuration and operation
of using filtered water as solvent water described in the
second embodiment may be applied to the water treatment
apparatus described in any of the third to eleventh
10 embodiments. The configuration and operation of reusing
ozone gas described in the third embodiment may be applied
to the water treatment apparatus described in any of the
fourth to eleventh embodiments. The configuration and
operation of using two types of cleaning agents described
15 in the eleventh embodiment may be applied to the water
treatment apparatus described in any of the second to tenth
embodiments. Other combinations of embodiments can also be
applied as appropriate.
[0095] Moreover, the ozone water production apparatus
20 described in any of the first to eleventh embodiments can
be applied not only to the cleaning of the separation
membrane in the water treatment apparatus but also to an
apparatus for reaction between ozone gas and a liquid
containing a solid, e.g. sewage sludge, paper pulp, and the
25 like.
[0096] The configurations described in the abovementioned embodiments indicate examples. The embodiments
can be combined with another well-known technique and with
each other, and some of the configurations can be omitted
30 or changed in a range not departing from the gist.
Reference Signs List
[0097] 1a pipe for water to be treated; 2a filtered
50
water pipe; 2b discharge pipe; 3a oxygen gas pipe; 3b
other gas pipe; 3c ozone gas pipe; 3d membrane cleaning
pipe; 3e solvent water pipe; 3f waste ozone gas pipe; 3g
oxygen recycle pipe; 3h, 3i, 3j, 3k circulation pipe; 3m
5 ozone water pipe; 3n sodium hypochlorite solution pipe; 10
treatment tank; 11 separation membrane; 20 membrane state
measurement unit; 21, 53 switching valve; 22 process
control unit; 23 filtered water pump; 25 regulating
valve; 26 solvent water storage tank; 30 oxygen gas
10 supply unit; 31 other gas supply unit; 32 ozone gas
generation unit; 33 ozone injection unit; 34, 34a ozone
water generation unit; 35 ozone water state measurement
unit; 36 ozone water feed pump; 37 condition control
unit; 38 waste ozone treatment apparatus; 39, 40 ozone
15 gas concentration storage unit; 41 circulation fan; 42, 44,
46, 50 circulation pump; 43 ejector; 45 barrier; 47
membrane module; 48, 49 fine bubble generator unit; 51
sodium hypochlorite solution supply unit; 52 pump; 100,
100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h, 100i ozone
20 water production apparatus.
51
WE CLAIM:
1. An ozone water production apparatus comprising:
a first gas supply unit to supply a first gas
containing an oxygen gas;
5 a second gas supply unit to supply a second gas
containing at least one of carbon dioxide gas, nitrogen gas,
and nitrogen oxide gas;
an electric discharge unit to generate a third gas
containing ozone gas by performing electric discharge
10 treatment on a gas containing the first gas supplied by the
first gas supply unit and the second gas supplied by the
second gas supply unit; and
an ozone water generation unit to generate ozone water
by dissolving the third gas in solvent water.
15
2. The ozone water production apparatus according to
claim 1, comprising
a control unit to control a generation amount of a byproduct that is obtained through the electric discharge
20 treatment on the second gas.
3. The ozone water production apparatus according to
claim 2, wherein the control unit controls the generation
amount by adjusting a flow rate of the second gas supplied
25 from the second gas supply unit.
4. The ozone water production apparatus according to
claim 2 or 3, wherein the control unit controls the
generation amount by adjusting an electric discharge
30 condition in the electric discharge treatment.
5. The ozone water production apparatus according to
claim 4, wherein the electric discharge condition is at
52
least one of gas pressure, temperature, current, voltage,
and electric discharge power in the electric discharge
treatment.
5 6. The ozone water production apparatus according to any
one of claims 2 to 5, comprising
an ozone water state measurement unit to measure an
amount indicating a state related to pH of the ozone water,
wherein
10 the control unit controls the generation amount based
on a measured value measured by the ozone water state
measurement unit.
7. The ozone water production apparatus according to
15 claim 6, wherein the ozone water state measurement unit
measures a pH of the ozone water.
8. The ozone water production apparatus according to
claim 6, wherein the ozone water state measurement unit
20 measures a dissolved ozone concentration of the ozone water.
9. The ozone water production apparatus according to any
one of claims 6 to 8, wherein the control unit controls the
generation amount such that the measured value lies within
25 a predetermined range.
10. The ozone water production apparatus according to any
one of claims 1 to 9, wherein the third gas that has not
been dissolved in the solvent water in the ozone water
30 generation unit is introduced into the ozone water
generation unit.
53
11. The ozone water production apparatus according to any
one of claims 1 to 10, comprising
an ozone gas separation unit to separate ozone gas and
oxygen gas in the third gas, wherein
5 the ozone gas separated by the ozone gas separation
unit is introduced into the ozone water generation unit,
and
the oxygen gas separated by the ozone gas separation
unit is introduced into the electric discharge unit.
10
12. The ozone water production apparatus according to any
one of claims 1 to 11, wherein in the ozone water
generation unit, the solvent water and the ozone gas are in
countercurrent contact with each other.
15
13. The ozone water production apparatus according to any
one of claims 1 to 11, comprising
a fine bubble generator unit to introduce the third
gas as fine bubbles into the ozone water generation unit.
20
14. The ozone water production apparatus according to any
one of claims 1 to 11, wherein the ozone water generation
unit is a membrane module including a porous membrane.
25 15. The ozone water production apparatus according to any
one of claims 1 to 14, wherein
the ozone water is used as a cleaning agent for
cleaning a separation membrane for solid-liquid separation
in a water treatment apparatus that purifies water to be
30 treated using membrane bioreactor, and
the solvent water is filtered water filtered by the
separation membrane.
54
16. The ozone water production apparatus according to
claim 15, comprising
a sodium hypochlorite solution supply unit to supply a
sodium hypochlorite solution, wherein
5 the cleaning agent to be supplied to the separation
membrane is switchable between the ozone water and the
sodium hypochlorite solution.
17. A water treatment apparatus including a separation
10 membrane for solid-liquid separation and that purifies
water to be treated using membrane bioreactor, the water
treatment apparatus comprising:
the ozone water production apparatus according to any
one of claims 1 to 14, wherein
15 the separation membrane is cleaned using ozone water
generated by the ozone water production apparatus.
18. An ozone water production method comprising:
a first gas supply step of supplying a first gas
20 containing an oxygen gas;
a second gas supply step of supplying a second gas
containing at least one of carbon dioxide gas, nitrogen gas,
and nitrogen oxide gas;
an electric discharge step of generating a third gas
25 containing ozone gas by performing electric discharge
treatment on a gas containing the first gas supplied in the
first gas supply step and the second gas supplied in the
second gas supply step; and
30
55
an ozone water generation step of generating ozone
water by dissolving the third gas in solvent water.