FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
MEMBRANE CLEANING DEVICE, MEMBRANE SEPARATION ACTIVATED
SLUDGE SYSTEM, AND MEMBRANE CLEANING 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
MEMBRANE CLEANING DEVICE, MEMBRANE SEPARATION ACTIVATED
SLUDGE SYSTEM, AND MEMBRANE CLEANING METHOD
5
TECHNICAL FIELD
[0001] The present disclosure relates to a membrane
cleaning device, a membrane separation activated sludge
system, and a membrane cleaning method.
10
BACKGROUND ART
[0002] In a membrane separation activated sludge process
which is a waste water treatment method using a membrane
separation activated sludge device, i.e., a membrane bio
15 reactor (MBR), waste water and microorganisms are reacted
with each other, and generated contaminants are removed as
sludge. The generated contaminants are removed from the
waste water by solid-liquid separation using a separation
membrane. The separation membrane filters out the
20 contaminants contained in the waste water to separate the
contaminants therefrom. Due to continuous use of the
separation membrane, contaminants adhere to the surface of
the separation membrane or into the pores of the separation
membrane and thus can cause clogging. The filtration
25 performance, that is, the solid-liquid separation
3
performance, of the separation membrane in which clogging has
occurred is gradually deteriorated. Therefore, it is
proposed that a separation membrane is cleaned by a cleaning
method called “reverse cleaning” in which cleaning water
5 containing an oxidizing agent such as ozone is injected
thereinto in the direction opposite to the filtration
direction. In the conventional membrane cleaning device,
ozone gas is dissolved in dissolution water to generate ozone
water by a semi-batch method. That is, the dissolution water
10 is supplied to an ozone water generation unit capable of
storing the dissolution water, and the supply of the
dissolution water is stopped at the time at which a
predetermined amount is reached. Then, ozone gas is
continuously supplied to the dissolution water maintained in
15 the predetermined amount, thereby generating ozone water from
the dissolution water. When feeding the ozone water
generated by the ozone water generation unit and cleaning a
separation membrane, the supply of ozone gas is continued
while the feeding of the dissolution water to the ozone water
20 generation unit is stopped, in order to maintain the
dissolved ozone concentration of the ozone water (see, for
example, Patent Document 1).
CITATION LIST
25 PATENT DOCUMENT
4
[0003] Patent Document 1: Japanese Patent No. 6430091
SUMMARY OF THE INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION
5 [0004] However, in the above-described membrane cleaning
device, during cleaning of the separation membrane, the water
amount in the ozone water generation unit decreases, and the
water level of the ozone water in the ozone water generation
unit falls. Here, ozone gas supplied to the ozone water in
10 the ozone water generation unit rises toward the water
surface. Thus, if the water level of the ozone water is low,
the contact time of gas and liquid becomes shortened, causing
a problem that the dissolution efficiency of ozone gas is
decreased.
15 [0005] The present disclosure has been made to solve the
above problem, and an object of the present disclosure is to
obtain a membrane cleaning device, a membrane separation
activated sludge system, and a membrane cleaning method which
are capable of preventing a decrease in the dissolution
20 efficiency of ozone gas.
SOLUTION TO THE PROBLEMS
[0006] A membrane cleaning device according to the present
disclosure is a membrane cleaning device for cleaning a
25 separation membrane for separating contaminants contained in
5
treatment target water from the treatment target water, with
ozone water stored in an ozone water generation unit, the
membrane cleaning device including: an ozone gas supply unit
for supplying ozone gas to the ozone water generation unit; a
5 dissolution water supply unit for supplying dissolution water
to the ozone water generation unit; an ozone water feeding
unit for feeding the ozone water stored in the ozone water
generation unit to the separation membrane; and a control
unit for, in a state where the ozone gas supply unit is
10 caused to supply the ozone gas from the ozone gas supply unit
to the ozone water generation unit, causing the dissolution
water supply unit to supply the dissolution water from the
dissolution water supply unit to the ozone water generation
unit and causing the ozone water feeding unit to feed the
15 ozone water from the ozone water generation unit to the
separation membrane.
[0007] Moreover, a membrane cleaning method according to
the present disclosure is a membrane cleaning method for
cleaning a separation membrane for separating contaminants
20 contained in treatment target water from the treatment target
water, with ozone water stored in an ozone water generation
unit, the membrane cleaning method including: an ozone gas
supply step of supplying ozone gas to the ozone water
generation unit; a dissolution water supply step of supplying
25 dissolution water to the ozone water generation unit; an
6
ozone water feeding step of feeding the ozone water stored in
the ozone water generation unit to the separation membrane;
and a continuous operation step of performing the dissolution
water supply step and the ozone water feeding step while
5 supplying the ozone gas to the ozone water generation unit.
EFFECT OF THE INVENTION
[0008] With the membrane cleaning device and the membrane
cleaning method according to the present disclosure, it is
10 possible to prevent a decrease in the dissolution efficiency
of ozone gas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] [FIG. 1A] FIG. 1A is a configuration diagram
15 showing a membrane separation activated sludge system and a
membrane cleaning device according to Embodiment 1, and
illustrates a dissolution water supply step.
[FIG. 1B] FIG. 1B is a configuration diagram
showing the membrane separation activated sludge system and
20 the membrane cleaning device according to Embodiment 1, and
illustrates an ozone gas supply step.
[FIG. 1C] FIG. 1C is a configuration diagram
showing the membrane separation activated sludge system and
the membrane cleaning device according to Embodiment 1, and
25 illustrates a continuous operation step.
7
[FIG. 2] FIG. 2 is a diagram showing a
configuration example of a control unit according to
Embodiment 1.
[FIG. 3] FIG. 3 is a flowchart showing the
5 operation of the membrane cleaning device according to
Embodiment 1.
[FIG. 4A] FIG. 4A is a configuration diagram
showing a membrane separation activated sludge system and a
membrane cleaning device according to Embodiment 2, and
10 illustrates an ozone gas supply step.
[FIG. 4B] FIG. 4B is a configuration diagram
showing the membrane separation activated sludge system and
the membrane cleaning device according to Embodiment 2, and
illustrates a continuous operation step.
15 [FIG. 5] FIG. 5 is a diagram showing an example of
the hardware configuration of the control unit according to
Embodiment 1.
DESCRIPTION OF EMBODIMENTS
20 [0010] Hereinafter, embodiments of a membrane separation
activated sludge system and a membrane cleaning device
according to the present disclosure will be described in
detail with reference to the accompanying drawings. The
embodiments described below are examples.
25 [0011] Embodiment 1
8
Embodiment 1 will be described with reference to
FIG. 1A to FIG. 3. FIG. 1A to FIG. 1C are configuration
diagrams showing a membrane separation activated sludge
system and a membrane cleaning device according to Embodiment
5 1, FIG. 1A illustrates a dissolution water supply step, FIG.
1B illustrates an ozone gas supply step, and FIG. 1C
illustrates a continuous operation step. When an arrow is
provided to each pipe, it indicates that fluid flowing in the
pipe flows in the direction of the arrow. When no arrow is
10 provided, it indicates that there is no flow in that step.
As shown in FIG. 1A, a membrane separation activated sludge
system 100 includes a membrane separation activated sludge
device 20 having a membrane separation tank 1 and a
separation membrane 2, and a membrane cleaning device 40 for
15 cleaning the separation membrane 2. An inflow pipe 5 which
is a pipe member through which waste water or the like flows
is connected to the membrane separation tank 1, and waste
water or the like flows into the membrane separation tank 1
via the inflow pipe 5. The waste water or the like that has
20 flowed into the membrane separation tank 1 is stored as
treatment target water 6 in the membrane separation tank 1.
[0012] In the membrane separation tank 1, a side surface
and a bottom surface are formed by concrete, so that water
leakage in the membrane separation tank 1 is prevented. In
25 the treatment target water 6 stored in the membrane
9
separation tank 1, in addition to contaminants,
microorganisms (hereinafter, referred to as activated sludge)
for capturing the contaminants are contained. Therefore, the
contaminants in the treatment target water 6 are contained in
5 the treatment target water 6 in a state of being captured in
the activated sludge.
[0013] The separation membrane 2 is a rectangular
parallelepiped-shaped membrane member in which each surface
is formed by a membrane such as a hollow fiber membrane, and
10 the direction from the outside of a rectangular
parallelepiped-shaped space demarcated by each surface
described above toward the inside of this space is the
filtration direction of the separation membrane 2. The
separation membrane 2 is disposed in the membrane separation
15 tank 1 and immersed in the treatment target water 6. In
addition, one end of a filtered water pipe 3a is inserted
inside the separation membrane 2. The filtered water pipe 3a
is a pipe member through which the treatment target water 6
filtered by the separation membrane 2 is discharged as
20 treated water 7 to the outside of the system, and a
filtration pump 4 for sucking the treated water 7 by using
pressure is provided on the filtered water pipe 3a. When the
filtration pump 4 operates, the treated water 7 inside the
separation membrane 2 flows into the filtered water pipe 3a,
25 and the treatment target water 6 outside the separation
10
membrane 2 flows into the separation membrane 2. At this
time, the treatment target water 6 flowing through the
separation membrane 2 is filtered, and the activated sludge
in the treatment target water 6 is separated by the
5 separation membrane 2. Since the activated sludge captures
the contaminants in the treatment target water 6 as described
above, the contaminants contained in the treatment target
water 6 are also separated when the activated sludge in the
treatment target water 6 is separated. The activated sludge
10 and the contaminants separated from the treatment target
water 6 adhere to the separation membrane 2. The treatment
target water 6 from which the contaminants have been removed
as described becomes the treated water 7, is sucked by the
filtration pump 4, flows through the filtered water pipe 3a,
15 and is discharged from the other end of the filtered water
pipe 3a to the outside of the system as described above. The
membrane forming the separation membrane 2 is not limited to
the above-described hollow fiber membrane, and a flat
membrane or the like may be used. In addition, it is
20 sufficient that the separation membrane 2 is a membrane
member capable of separating solid and liquid in the
treatment target water 6 containing the activated sludge, and
thus an ultrafiltration (UF) membrane, a microfiltration (MF)
membrane, or the like can also be used as the separation
25 membrane 2.
11
[0014] When separation of solid and liquid in the
treatment target water 6 by the separation membrane 2 is
continued, in other words, when a filtration process for
filtering the treatment target water 6 that is present
5 outside the separation membrane 2 is continued, there is a
possibility that the activated sludge and the contaminants in
the treatment target water 6 adhere to the surface of the
separation membrane 2 or into the pores of the separation
membrane 2, thus causing clogging. When the clogging has
10 occurred, there is a possibility that the filtration rate by
the separation membrane 2 is reduced and the rate of
treatment of the treatment target water 6 is reduced. As
described above, the continuous use of the separation
membrane 2 may decrease the water treatment efficiency of the
15 membrane separation activated sludge system 100. Therefore,
it is necessary to clean the separation membrane 2 as
appropriate to prevent clogging and the like.
[0015] The membrane cleaning device 40 is a cleaning
device for cleaning the separation membrane 2. The membrane
20 cleaning device 40 includes a dissolution water supply unit 8
for supplying dissolution water to an ozone water generation
unit 9, the ozone water generation unit 9 for dissolving
ozone gas in the dissolution water to generate ozone water,
an ozone gas supply unit 10 for supplying ozone gas to the
25 ozone water generation unit 9, an ozone water feeding unit 11
12
for injecting the ozone water generated by the ozone water
generation unit 9 into the inside of the separation membrane
2, and a control unit 12 for controlling the operation of the
dissolution water supply unit 8, the ozone gas supply unit
5 10, and the ozone water feeding unit 11 according to a step.
The dissolution water supply unit 8, the ozone gas supply
unit 10, and the ozone water feeding unit 11 are connected to
the control unit 12 via signal lines 50a, 50b, and 50c,
respectively. In FIG. 1A to FIG. 1C, arrows at the signal
10 lines 50a to 50c indicate that the control unit 12 operates
the target function unit(s) in a step shown in each drawing.
For example, in the dissolution water supply step of FIG. 1A,
the dissolution water supply unit 8 operates, but the ozone
gas supply unit 10 and the ozone water feeding unit 11 do not
15 operate. In addition, the control unit 12 is connected to a
dissolved ozone sensor 9b of the ozone water generation unit
9, that is, a concentration measurement unit, via a signal
line 51.
[0016] The dissolution water supply unit 8 is connected to
20 the ozone water generation unit 9 via a dissolution water
supply pipe 3c. The dissolution water is water in which
ozone gas is dissolved in the ozone water generation unit 9
to generate ozone water, and is supplied from the dissolution
water supply unit 8 through the dissolution water supply pipe
25 3c to the ozone water generation unit 9. The dissolution
13
water supply unit 8 starts or stops supply of the dissolution
water to the ozone water generation unit 9 in accordance with
a control signal from the control unit 12. The dissolution
water is not particularly limited, and, for example, tap
5 water, industrial water, or the treated water 7 obtained as a
result of filtration with the separation membrane 2 can be
used. When the treated water 7 is used as the dissolution
water, a pipe through which the treated water 7 is fed from
the filtered water pipe 3a to the dissolution water supply
10 unit 8 and a pump for feeding the treated water 7 are
required, but it is not necessary to newly introduce water
from the outside, so that the cost required for cleaning can
be reduced.
[0017] The ozone water generation unit 9 is connected to
15 the ozone water feeding unit 11 via an ozone water feeding
pipe 3b1. The ozone water generation unit 9 is configured to
be capable of storing liquid therein, and is capable of
storing the dissolution water supplied from the dissolution
water supply unit 8 and the ozone water generated from the
20 dissolution water. A gas diffusing unit 9a connected to the
ozone gas supply unit 10 via an ozone gas supply pipe 3d is
provided at a bottom portion within the ozone water
generation unit 9. The ozone gas supplied from the ozone gas
supply unit 10 is discharged as air bubbles from the gas
25 diffusing unit 9a, whereby the ozone gas is injected to the
14
dissolution water in the ozone water generation unit 9. A
connection portion (not shown) between the ozone water
generation unit 9 and the dissolution water supply pipe 3c is
provided at one side wall of the ozone water generation unit
5 9, and a connection portion (not shown) between the ozone
water generation unit 9 and the ozone water feeding pipe 3b1
is provided at another side wall of the ozone water
generation unit 9. In addition, the connection portion
between the ozone water generation unit 9 and the dissolution
10 water supply pipe 3c is provided at a higher position than
the connection portion between the ozone water generation
unit 9 and the ozone water feeding pipe 3b1. Moreover, an
exhaust ozone gas pipe 3e communicating with the outside of
the ozone water generation unit 9 is provided at an upper
15 portion of the ozone water generation unit 9. The exhaust
ozone gas pipe 3e is a pipe through which the ozone gas that
has not been dissolved in the ozone water generation unit 9
is discharged as exhaust ozone gas to the outside of the
system.
20 [0018] The position at which the gas diffusing unit 9a is
provided is not limited to the bottom portion of the ozone
water generation unit 9, but the gas diffusing unit 9a is
preferably provided at as low a position as possible since
air bubbles of ozone gas discharged from the gas diffusing
25 unit 9a flow upward toward the water surface of the
15
dissolution water. When the gas diffusing unit 9a is
provided at a lower position, the contact time of the
dissolution water and the ozone gas can be extended to
improve the dissolution efficiency. In addition, the
5 position of the connection portion between the ozone water
generation unit 9 and the dissolution water supply pipe 3c
and the position of the connection portion between the ozone
water generation unit 9 and the ozone water feeding pipe 3b1
are not particularly limited, but the distance therebetween
10 is preferably as large as possible. In addition, by
providing the connection portion with the dissolution water
supply pipe 3c at a higher position than the connection
portion with the ozone water feeding pipe 3b1 as described
above, the dissolution efficiency of ozone gas can be
15 improved. This is because, in this case, since the
dissolution water flows in from a high position, the flow of
the dissolution water becomes downward flow, and the flow of
the dissolution water and the flow of ozone gas are counter
flows. In this case, counter flow contact occurs between the
20 dissolution water and the ozone gas, so that the dissolution
efficiency is improved.
[0019] The ozone water generation unit 9 is provided with
the dissolved ozone sensor 9b. The dissolved ozone sensor 9b
continuously or intermittently measures the dissolved ozone
25 concentration of the ozone water (including the case where
16
the dissolution water is mixed; the same applies below) in
the ozone water generation unit 9, and transmits the
measurement result to the control unit 12 via the signal line
51.
5 [0020] The ozone water generation unit is not particularly
limited as long as the ozone water generation unit has a
structure that allows ozone gas to be dissolved in the
dissolution water to generate ozone water. The ozone water
generation unit 9 of Embodiment 1 is configured as an ozone
10 water generation unit that is capable of storing the
dissolution water therein and has both a function of storing
the dissolution water therein and a function of dissolving
ozone gas in the dissolution water, but a storage tank for
storing the dissolution water therein and a dissolution
15 mechanism for dissolving ozone gas in the dissolution water
stored in the storage tank may be separately provided. As a
method for dissolving ozone gas in the dissolution water, in
addition to the method (gas diffusing method) in which the
gas diffusing unit 9a is provided in the ozone water
20 generation unit 9, an ozone gas dissolving method such as an
ejector method or a dissolution membrane method can be used.
[0021] The ozone gas supply unit 10 supplies ozone gas to
the gas diffusing unit 9a in the ozone water generation unit
9 via the ozone gas supply pipe 3d. The ozone gas supply
25 unit 10 starts or stops supply of ozone gas to the ozone
17
water generation unit 9 in accordance with a control signal
from the control unit 12. The ozone gas supply unit 10
includes a source gas supply unit (not shown) and an ozonizer
(not shown) for generating ozone gas from oxygen supplied
5 from the source gas supply unit. As a source gas generation
unit, for example, a liquid oxygen tank or an oxygen
generator utilizing vacuum pressure swing adsorption (VPSA)
is used, but the source gas generation unit is not
particularly limited as long as the source gas generation
10 unit is capable of supplying oxygen. As the ozonizer, for
example, a discharge ozonizer can be used.
[0022] The dissolution water supply unit 8 or the ozone
water generation unit 9 may be provided with pH adjustment
means, and the pH of either one of or both the ozone water
15 and the dissolution water may be adjusted to 2 to 6. Selfdecomposition of ozone is less likely to occur as the pH is
lower. Thus, by adjusting the pH of the dissolution water as
described above, self-decomposition of ozone can be
suppressed, and ozone water can be efficiently generated.
20 The same effect is also achieved in the case of adjusting the
pH of the ozone water. In these cases, the required amount
of ozone gas can be reduced, so that the cost required for
cleaning can be reduced. In addition, either one of or both
the dissolution water supply unit 8 and the ozone water
25 generation unit 9 may be provided with temperature adjustment
18
means, and the water temperatures of the ozone water and the
dissolution water may be adjusted to a certain temperature or
lower. The solubility of ozone is higher as the water
temperature is lower. Thus, by adjusting the water
5 temperature to the certain temperature or lower, ozone water
having a higher concentration is generated, and the cleaning
effect of the ozone water is improved. In this case, the
required amount of the dissolution water can be reduced, so
that the cost required for cleaning can be reduced.
10 [0023] The ozone water feeding unit 11 is connected to the
ozone water generation unit 9 via the ozone water feeding
pipe 3b1 and also connected to the filtered water pipe 3a via
an ozone water feeding pipe 3b2. The ozone water feeding
unit 11 is a unit to which the ozone water generated by the
15 ozone water generation unit 9 is fed from the ozone water
generation unit 9 and which injects the ozone water into the
inside of the separation membrane 2 via a filtration pipe 3a.
When the ozone water is fed into the inside of the separation
membrane 2 by the ozone water feeding unit 11, the ozone
20 water flows from the inside of the separation membrane 2 to
the outside of the separation membrane 2 (in the direction
opposite to the filtration direction), so that reverse
cleaning of the separation membrane 2 is performed.
Accordingly, contaminants and sludge adhering to the
25 separation membrane 2 are separated from the separation
19
membrane 2, so that the separation membrane 2 is cleaned.
The ozone water feeding unit 11 starts or stops feeding of
the ozone water to the separation membrane 2 in accordance
with a control signal from the control unit 12.
5 [0024] The control unit 12 transmits control signals to
the dissolution water supply unit 8, the ozone gas supply
unit 10, and the ozone water feeding unit 11 and performs
control of switching a step to be performed. That is, the
control signals from the control unit 12 have a function as a
10 switching signal for switching the step to be performed.
Steps performed in Embodiment 1 include a “dissolution water
supply step”, an “ozone gas supply step”, an “ozone water
feeding step”, and a “continuous operation step”. The
“dissolution water supply step” is a step of supplying the
15 dissolution water from the dissolution water supply unit 8 to
the ozone water generation unit 9. As shown in FIG. 1A, in
the dissolution water supply step, the dissolution water
supply unit 8 operates according to a control signal from the
control unit 12, and the dissolution water flows in the
20 dissolution water supply pipe 3c from the dissolution water
supply unit 8 to the ozone water generation unit 9. On the
other hand, since the ozone gas supply unit 10 does not
operate, there is no flow of ozone gas in the ozone gas
supply pipe 3d, and no exhaust ozone gas is discharged from
25 the exhaust ozone gas pipe 3e as well. In addition, since
20
the ozone water feeding unit 11 also does not operate, there
is also no flow of the ozone water in the ozone water feeding
pipes 3b1 and 3b1. In the dissolution water supply step,
treatment of the treatment target water 6 by the membrane
5 separation activated sludge device 20 can also be performed
in parallel. FIG. 1A shows that the treatment target water 6
flows through the inflow pipe 5 into the membrane separation
tank 1, and the treated water 7 sucked by the filtration pump
4 flows through the filtered water pipe 3a and is discharged
10 to the outside of the system.
[0025] The “ozone gas supply step” is a step of generating
ozone water by a semi-batch method in which ozone gas is
continuously supplied to the dissolution water stored in a
predetermined amount. As shown in FIG. 1B, in the ozone gas
15 supply step, the ozone gas supply unit 10 operates according
to a control signal from the control unit 12, and ozone gas
flows in the ozone gas supply pipe 3d from the ozone gas
supply unit 10 to the ozone water generation unit 9. In
addition, exhaust ozone gas is discharged from the exhaust
20 ozone gas pipe 3e. On the other hand, since the dissolution
water supply unit 8 does not operate, there is no flow of the
dissolution water in the dissolution water supply pipe 3a.
In addition, since the ozone water feeding unit 11 also does
not operate, there is also no flow of the ozone water in the
25 ozone water feeding pipes 3b1 and 3b1. Also, in the ozone
21
gas supply step, similar to the dissolution water supply
step, treatment of the treatment target water 6 by the
membrane separation activated sludge device 20 can be
performed in parallel.
5 [0026] The “ozone water feeding step” is a step of feeding
the ozone water stored in the ozone water generation unit 9
to the separation membrane 2 to clean the separation membrane
2. In addition, the “continuous operation step” is a step
of, in a state where ozone gas is supplied from the ozone gas
10 supply unit 10 to the ozone water generation unit 9,
generating ozone water by a continuous method in which the
dissolution water is supplied from the dissolution water
supply unit 8 to the ozone water generation unit 9 and the
ozone water is fed from the ozone water feeding unit 11 to
15 the separation membrane 2, and feeding the ozone water to the
separation membrane 2 to clean the separation membrane 2. In
other words, in the continuous operation step, by newly
supplying the dissolution water to the ozone water generation
unit 9 while feeding the ozone water from the ozone water
20 generation unit 9 to the separation membrane 2, cleaning of
the separation membrane 2 by the ozone water and generation
of ozone water by the continuous method are performed in
parallel. That is, the “continuous operation step” of
Embodiment 1 is a step of performing the dissolution water
25 supply step and the ozone water feeding step while supplying
22
ozone gas to the ozone water generation unit 9. As shown in
FIG. 1C, in the continuous operation step, the dissolution
water supply unit 8, the ozone gas supply unit 10, and the
ozone water feeding unit 11 operate according to control
5 signals from the control unit 12. Accordingly, the
dissolution water flows in the dissolution water supply pipe
3c from the dissolution water supply unit 8 to the ozone
water generation unit 9, and ozone gas flows in the ozone gas
supply pipe 3d from the ozone gas supply unit 10 to the ozone
10 water generation unit 9. In addition, exhaust ozone gas is
discharged from the exhaust ozone gas pipe 3e. Moreover, the
ozone water flows in the ozone water feeding pipe 3b1 from
the ozone water generation unit 9 to the ozone water feeding
unit 11, and the ozone water flows in the ozone water feeding
15 pipe 3b2 from the ozone water feeding unit 11 to the filtered
water pipe 3a. The ozone water flowing in the filtered water
pipe 3a flows into the inside of the separation membrane 2,
and reverse cleaning of the separation membrane 2 is
performed as described above. In the continuous operation
20 step, it is necessary to cause the ozone water to flow into
the separation membrane 2 via the filtered water pipe 3a, and
thus treatment of the treatment target water 6 by the
membrane separation activated sludge device 20 is not
performed.
23
[0027] A specific configuration of the control unit 12
will be described. FIG. 2 is a diagram showing a
configuration example of the control unit according to
Embodiment 1. The control unit 12 includes an ozone
5 concentration reception unit 13, a storage unit 14, a
determination unit 15, and a control signal transmission unit
16. The ozone concentration reception unit 13 and the
determination unit 15 are connected to each other via a
signal line 52a. The storage unit 14 and the determination
10 unit 15 are connected to each other via a signal line 52b.
In addition, the determination unit 15 and the control signal
transmission unit 16 are connected to each other via a signal
line 52c. The ozone concentration reception unit 13 is
connected to the dissolved ozone sensor 9b via the signal
15 line 51, and receives data of a dissolved ozone
concentration, which is a measurement result of the dissolved
ozone sensor 9b, via the signal line 51. The ozone
concentration reception unit 13 transmits the received data
of the dissolved ozone concentration to the determination
20 unit 15 via the signal line 52a. In the storage unit 14, a
dissolved ozone concentration that is a predetermined
threshold value is stored. The threshold value stored in the
storage unit 14 is a threshold value for determining whether
or not switching of the continuous operation step can be
24
performed. The ozone concentration reception unit 13
corresponds to an ozone concentration acquisition unit.
[0028] The determination unit 15 determines a step to be
performed by the membrane cleaning device 40. The
5 determination unit 15 acquires data of a measured value of
the dissolved ozone concentration of the ozone water in the
ozone water generation unit 9 from the ozone concentration
reception unit 13, and compares the measured value of the
dissolved ozone concentration with the threshold value stored
10 in the storage unit 14. When the measured value of the
dissolved ozone concentration is equal to or higher than the
threshold value, the determination unit 15 determines the
continuous operation step as the step to be performed. When
the measured value of the dissolved ozone concentration is
15 less than the threshold value, the determination unit 15
determines the ozone gas supply step as the step to be
performed. As described above, the determination unit 15
determines whether or not switching of the step to be
performed between the ozone gas supply step and the
20 continuous operation step can be performed, on the basis of
the dissolved ozone concentration of the ozone water in the
ozone water generation unit 9.
[0029] When the determined step and the currently
performed step are different from each other, the
25 determination unit 15 generates a control signal for
25
switching the step to be performed, and transmits the
generated control signal to the control signal transmission
unit via the signal line 52. The control signal transmission
unit 16 transmits the control signal received from the
5 determination unit 15, to the dissolution water supply unit
8, the ozone gas supply unit 10, and the ozone water feeding
unit 11 via the signal lines 50a, 50b, and 50c, respectively.
[0030] For example, when switching from the ozone gas
supply step to the continuous operation step is performed, a
10 control signal for starting feeding is generated as a control
signal to the dissolution water supply unit 8, and a control
signal for starting feeding is also generated as a control
signal to the ozone water feeding unit 11. The operation of
the ozone gas supply unit 10 does not change before and after
15 the step switching (supply of ozone gas is continued), and
thus a control signal to the ozone gas supply unit 10 is not
generated in this case.
[0031] FIG. 5 is a diagram showing an example of a
hardware configuration that realizes the control unit 12.
20 Each function unit of the control unit 12 described above is
realized by a processor 71 executing a program stored in a
memory 72 or a hard disk 73. Alternatively, a plurality of
processors 71 and a plurality of memories 72 or hard disks 73
may cooperate to realize each function of the control unit
25 12. In addition, the control unit 12 includes a reception
26
circuit 74, and receives data from the dissolved ozone sensor
9b via the reception circuit 74. The data of the dissolved
ozone concentration received from the dissolved ozone sensor
9b, a result of calculation by the processor 71, and the
5 above-described predetermined threshold value are stored in
the memory 72 or the hard disk 73. Moreover, the control
unit 12 includes a transmission circuit 75, and transmits
control signals to the dissolution water supply unit 8, the
ozone gas supply unit 10, and the ozone water feeding unit 11
10 via the transmission circuit 75.
[0032] Next, operation will be described. FIG. 3 is a
flowchart showing the operation of the membrane cleaning
device according to Embodiment 1. First, it is checked
whether a predetermined amount of the dissolution water is
15 stored in the ozone water generation unit 9 (step ST001).
When the predetermined amount of the dissolution water is
stored in the ozone water generation unit 9, the operation
proceeds to step ST003.
[0033] When the predetermined amount of the dissolution
20 water is not stored in the ozone water generation unit 9, the
dissolution water is supplied to the ozone water generation
unit 9 (step ST002, the dissolution water supply step).
First, the step to be performed is switched to the
dissolution supply step by the control unit 12.
25 Specifically, the control unit 12 transmits a control signal
27
for starting feeding, to the dissolution water supply unit 8,
to start feeding of the dissolution water. The dissolution
water fed from the dissolution water supply unit 8 flows to
the ozone water generation unit 9 via the dissolution water
5 supply pipe 3c, whereby the dissolution water is supplied to
the ozone water generation unit 9. After the start of supply
of the dissolution water, step ST001 is regularly performed
to check the dissolution water stored in the ozone water
generation unit 9. When the predetermined amount of the
10 dissolution water is stored in the ozone water generation
unit 9, the operation proceeds to step ST003.
[0034] When the predetermined amount of the dissolution
water is stored in the ozone water generation unit 9, supply
of ozone gas from the ozone gas supply unit 10 to the ozone
15 water generation unit 9 is started in a state where supply of
the dissolution water from the dissolution water supply unit
8 to the ozone water generation unit 9 is stopped (step
ST003). Specifically, the control unit 12 transmits a
control signal for stopping feeding, to the dissolution water
20 supply unit 8 to stop the feeding of the dissolution water.
In addition, the control unit 12 transmits a control signal
for starting supply, to the ozone gas supply unit 10 to start
supply of ozone gas. Accordingly, the step to be performed
is switched to the ozone gas supply step, and generation of
25 ozone water by the semi-batch method is started. When
28
feeding of the dissolution water is not performed as in the
case where step ST002 is skipped, an operation of stopping
feeding is unnecessary.
[0035] In the ozone gas supply step, ozone gas is
5 dissolved in the dissolution water stored in the ozone water
generation unit 9 to generate ozone water (step ST004). The
ozone gas supplied from the ozone gas supply unit 10 flows to
the gas diffusing unit 9a in the ozone water generation unit
9 via the ozone gas supply pipe 3d, and air bubbles of the
10 ozone gas are injected from the gas diffusing unit 9a into
the dissolution water. The air bubbles of the ozone gas flow
toward the water surface of the dissolution water above the
gas diffusing unit 9a. While flowing upward in the
dissolution water, the air bubbles of the ozone gas come into
15 contact with the dissolution water, and part thereof is
dissolved in the dissolution water. The ozone gas that has
not been dissolved is discharged to the outside of the system
via the exhaust ozone gas pipe 3e. By dissolving the ozone
gas in the dissolution water as described above, ozone water
20 is generated. During the ozone gas supply step, the
dissolved ozone sensor 9b continuously or intermittently
measures the dissolved ozone concentration of the ozone water
in the ozone water generation unit 9 and transmits the
measurement result to the control unit 12.
29
[0036] At a predetermined timing during the ozone gas
supply step, it is determined whether the dissolved ozone
concentration of the generated ozone water is equal to or
higher than a predetermined threshold value, and it is
5 determined whether or not to switch the step to be performed
from the ozone gas supply step to the continuous operation
step (step ST005). The determination unit 15 of the control
unit 12 compares the measured value of the dissolved ozone
concentration of the ozone water in the ozone water
10 generation unit 9 with a threshold value stored in the
storage unit 14. When the measured value of the dissolved
ozone concentration is less than the threshold value, the
ozone gas supply step is continued (step ST006). Thereafter,
step ST005 is regularly performed, and whether or not to
15 switch the step to be performed is determined on the basis of
the result of the comparison between the measured value of
the dissolved ozone concentration and the threshold value.
[0037] When the measured value of the dissolved ozone
concentration is equal to or higher than the threshold value,
20 while the supply of ozone gas to the ozone water generation
unit 9 is continued, supply of the dissolution water to the
ozone water generation unit 9 and feeding of the ozone water
to the separation membrane 2 are started (step ST007).
Specifically, the control unit 12 transmits a control signal
25 for starting feeding, to each of the dissolution water supply
30
unit 8 and the ozone water feeding unit 11 to start supply of
the dissolution water from the dissolution water supply unit
8 to the ozone water generation unit 9 and feeding of the
ozone water from the ozone water generation unit 9 to the
5 separation membrane 2. Accordingly, the step to be performed
is switched from the ozone gas supply step to the continuous
operation step, cleaning of the separation membrane 2 by the
ozone water is started, and generation of ozone water is
switched from the semi-batch method to the continuous method.
10 The supply of ozone gas from the ozone gas supply unit 10 to
the ozone water generation unit 9 is also continued after
switching to the continuous operation step.
[0038] In the continuous operation step, while the supply
of ozone gas to the ozone water generation unit 9 is
15 continued, the dissolution water is supplied from the
dissolution water supply unit 8 to the ozone water generation
unit 9, and the ozone water is fed from the ozone water
generation unit 9 to the separation membrane 2 to clean the
separation membrane 2 (step ST008). The supply of the
20 dissolution water is the same as in the dissolution water
supply step as step ST002. Feeding of the ozone water is
performed by the ozone water feeding unit 11. First, the
ozone water in the ozone water generation unit 9 is fed from
the ozone water generation unit 9 via the ozone water feeding
25 pipe 3b1 to the ozone water feeding unit 11. Next, the ozone
31
water fed to the ozone water feeding unit 11 is fed via the
ozone water feeding pipe 3b2 to the filtered water pipe 3a,
and the ozone water is injected from the filtered water pipe
3a into the inside of the separation membrane 2. As
5 described above, when the ozone water is fed into the inside
of the separation membrane 2, the ozone water flows from the
inside of the separation membrane 2 to the outside of the
separation membrane 2 (in the direction opposite to the
filtration direction), so that the separation membrane 2 is
10 cleaned by reverse cleaning. As described above, that is, in
a state where the ozone gas supply unit 10 is caused to
supply ozone gas from the ozone gas supply unit 10 to the
ozone water generation unit 9, the control unit 12 performing
the continuous operation step performs the dissolution water
15 supply step by causing the dissolution water supply unit 8 to
supply the dissolution water from the dissolution water
supply unit 8 to the ozone water generation unit 9, and also
performs the ozone water feeding step by causing the ozone
water feeding unit 11 to feed the ozone water from the ozone
20 water generation unit 9 to the separation membrane 2. Also,
during the continuous operation step, the measurement of the
dissolved ozone concentration by the dissolved ozone sensor
9b is continued.
[0039] In the continuous operation step of Embodiment 1,
25 both supply of the dissolution water to the ozone water
32
generation unit 9 and feeding of the ozone water from the
ozone water generation unit 9 are performed. Therefore, by
appropriately setting a supply amount of the dissolution
water and a feeding amount of the ozone water, the water
5 amount and the water level in the ozone water generation unit
9 are maintained. In addition, since supply of ozone gas is
performed, a decrease in the dissolved ozone concentration is
also suppressed.
[0040] At a predetermined timing during the continuous
10 operation step, it is determined whether the dissolved ozone
concentration of the ozone water in the ozone water
generation unit 9 is less than a predetermined threshold
value, and it is determined whether or not to switch the step
to be performed from the continuous operation step to the
15 ozone gas supply step (step ST009). The determination unit
15 of the control unit 12 compares the measured value of the
dissolved ozone concentration of the ozone water in the ozone
water generation unit 9 with a threshold value stored in the
storage unit 14. When the measured value of the dissolved
20 ozone concentration is equal to or higher than the threshold
value, the determination unit 15 determines whether or not
cleaning of the separation membrane 2 has been completed
(step ST011). When cleaning has been completed, the supply
of ozone gas to the ozone water generation unit 9, the supply
25 of the dissolution water to the ozone water generation unit
33
9, and the feeding of the ozone water to the separation
membrane 2 are stopped (step ST013). Specifically, the
control unit 12 transmits a control signal for stopping
feeding, to each of the dissolution water supply unit 8 and
5 the ozone water feeding unit 11 to stop the supply of the
dissolution water from the dissolution water supply unit 8 to
the ozone water generation unit 9 and the feeding of the
ozone water from the ozone water generation unit 9 to the
separation membrane 2, and the control unit 12 also transmits
10 a control signal for stopping supply, to the ozone gas supply
unit 10 to stop the supply of ozone gas from the ozone gas
supply unit 10 to the ozone water generation unit 9. When
cleaning of the separation membrane 2 is not yet completed,
the continuous operation step is continued (step ST012).
15 Thereafter, step ST009 is regularly performed, and whether or
not to switch the step to be performed is determined on the
basis of the result of the comparison between the measured
value of the dissolved ozone concentration and the threshold
value.
20 [0041] When the measured value of the dissolved ozone
concentration is less than the threshold value, while the
supply of ozone gas to the ozone water generation unit 9 is
continued, the supply of the dissolution water to the ozone
water generation unit 9 and the feeding of the ozone water to
25 the separation membrane 2 are stopped (step ST010).
34
Specifically, the control unit 12 transmits a control signal
for stopping feeding, to each of the dissolution water supply
unit 8 and the ozone water feeding unit 11 to stop the supply
of the dissolution water from the dissolution water supply
5 unit 8 to the ozone water generation unit 9 and the feeding
of the ozone water from the ozone water generation unit 9 to
the separation membrane 2. Accordingly, the step to be
performed is switched from the separation membrane step to
the ozone gas supply step, cleaning of the separation
10 membrane 2 is stopped, and generation of ozone water is also
switched from the continuous method to the semi-batch method.
Then, the operation returns to step ST004. As described
above, the control unit 12 controls the step to be performed,
such that: the continuous operation step is performed when
15 the measured value of the dissolved ozone concentration of
the ozone water in the ozone water generation unit 9 is equal
to or higher than the threshold value; and the ozone gas
supply step is performed when the measured value of the
dissolved ozone concentration of the ozone water in the ozone
20 water generation unit 9 is less than the threshold value.
[0042] The order of step ST009 and step ST011 may be
changed. That is, in the continuous operation step,
determination as to completion of cleaning is performed
first, and whether or not switching to the ozone gas supply
35
step can be performed may be determined when cleaning is not
yet completed.
[0043] Moreover, the threshold value used in step ST005,
that is, a threshold value for determining whether or not
5 switching from the ozone gas supply step to the continuous
operation step can be performed, and the threshold value used
in step ST009, that is, a threshold value for determining
whether or not switching from the continuous operation step
to the ozone gas supply step can be performed, may be the
10 same or different from each other.
[0044] According to Embodiment 1, a decrease in the
dissolution efficiency of ozone gas can be prevented. More
specifically, in a state where the ozone gas supply unit is
caused to supply ozone gas from the ozone gas supply unit to
15 the ozone water generation unit, the separation membrane is
cleaned by the continuous operation step in which the
dissolution water supply unit is caused to supply the
dissolution water from the dissolution water supply unit to
the ozone water generation unit, and the ozone water
20 generation unit is caused to feed the ozone water from the
ozone water generation unit to the separation membrane.
During the continuous operation step, supply of the
dissolution water from the dissolution water supply unit to
the ozone water generation unit is performed, so that a
25 decrease in the water amount in the ozone water generation
36
unit and a fall in the water level due to feeding of the
ozone water, and shortening of the gas-liquid contact time
due to this decrease and this fall are suppressed.
Therefore, in ozone water generation by the continuous method
5 in the continuous operation step, a decrease in the
dissolution efficiency of ozone gas is prevented. In
addition, since supply of ozone gas from the ozone gas supply
unit to the ozone water generation unit is also performed,
even when the ozone gas that has not been dissolved is
10 discharged as exhaust ozone gas to the outside of the system
or self-decomposition of ozone occurs, the amount of ozone
gas in the ozone water generation unit is maintained.
Moreover, since the water amount in the ozone water
generation unit is maintained in the continuous operation
15 step, it is not necessary to supply the dissolution water
again when performing the ozone gas supply step again.
Therefore, the time required for generating a predetermined
amount of ozone water can be shortened.
[0045] Moreover, since the continuous operation step is
20 performed when the dissolved ozone concentration of the ozone
water is equal to or higher than the threshold value, and the
ozone gas supply step is performed when the dissolved ozone
concentration of the ozone water is less than the threshold
value, poor cleaning due to ozone water having an
25 insufficient concentration can be suppressed. This is
37
especially effective for the case where there is a
possibility that the water quality changes and the dissolved
ozone concentration decreases when generating ozone water by
the continuous method, such as the case where treated water
5 whose water quality is likely to change is used as the
dissolution water.
[0046] The control unit according to Embodiment 1 performs
switching between the ozone gas supply step and the
continuous operation step on the basis of the water quality
10 of the ozone water, more specifically, the concentration of
the dissolved ozone in the ozone water. However, the water
temperature, the pH, and the organic substance concentration
of the ozone water may be used as the water quality of the
ozone water which serves as a reference for determining the
15 step switching. In these cases as well, the water
temperature, the pH, or the organic substance concentration
of the ozone water in the ozone water generation unit is
measured, and switching between the ozone gas supply step and
the continuous operation step is performed on the basis of
20 comparison between the measured value and a threshold value.
More specifically, when the measured value of the water
temperature, the pH, or the organic substance concentration
is less than the threshold value, switching from the ozone
gas supply step to the continuous operation step is
25 performed, and when the measured value of the water
38
temperature, the pH, or the organic substance concentration
is equal to or higher than the threshold value, switching
from the continuous operation step to the ozone gas supply
step is performed. Accordingly, the same effect as when
5 using the dissolved ozone concentration as in Embodiment 1
can be achieved.
[0047] Moreover, switching from the ozone gas supply step
to the continuous operation step may be performed on the
basis of the supply time of ozone gas or the supply amount of
10 ozone gas. In the case of switching the step on the basis of
the supply time of ozone gas, the control unit is provided
with a timer, the elapsed time from the start of the ozone
gas supply step is regarded as a supply time of ozone gas,
and whether or not the step switching can be performed is
15 determined. In the case of switching the step on the basis
of the supply amount of ozone gas, the control unit is
provided with a calculator for the supply amount of ozone
gas, and whether or not the step switching can be performed
is determined on the basis of a calculation result. In the
20 case of using the supply amount of ozone gas, it is also
conceivable to measure the supply amount of ozone gas at the
ozone gas supply unit or the ozone gas supply pipe and
transmit the measurement result to the control unit.
[0048] The ozone water generation unit may be provided
25 with a water quality adjustment unit for adjusting water
39
quality such as water temperature, pH, and organic substance
concentration. By positively adjusting the water quality by
the water quality adjustment unit, it is possible to prevent
a decrease in the dissolution efficiency of ozone gas and
5 poor cleaning of the separation membrane, so that it is
possible to further improve the cleaning effect.
[0049] Moreover, the timing of start of supply of the
dissolution water and the timing of start of feeding of the
ozone water at the start of the continuous operation step may
10 be the same, or feeding of the ozone water may be started
first, and feeding of the dissolution water may be started at
the time at which the water level in the ozone water
generation unit reaches a certain level or lower.
[0050] Embodiment 2
15 Next, Embodiment 2 will be described with reference
to FIG. 4A and FIG. 4B. Portions identical or corresponding
to those in FIG. 1A to FIG. 3 are designated by the same
reference characters, and the description thereof is omitted.
Embodiment 2 is different from Embodiment 1 in that, for
20 example, a plurality of ozone water generation units are
included. FIG. 4A and FIG. 4B are configuration diagrams
showing a membrane separation activated sludge system and a
membrane cleaning device according to Embodiment 2, FIG. 4A
illustrates an ozone gas supply step, and FIG. 4B illustrates
25 a continuous operation step. A dissolution water supply step
40
is the same as that in Embodiment 1 except for the cases
described in particular below, and thus is not shown. As
shown in FIG. 4A, a membrane separation activated sludge
system 200 includes a membrane separation activated sludge
5 device 20 having a membrane separation tank 1 and a
separation membrane 2, and a membrane cleaning device 401 for
cleaning the separation membrane 2.
[0051] The membrane cleaning device 401 is a cleaning
device for cleaning the separation membrane 2. The membrane
10 cleaning device 401 includes a dissolution water supply unit
8 for supplying dissolution water to a first ozone water
generation unit 91, the first ozone water generation unit 91
and a second ozone water generation unit 92 for dissolving
ozone gas in the dissolution water to generate ozone water,
15 an ozone gas supply unit 10 for supplying ozone gas to the
second ozone water generation unit 92, an ozone water feeding
unit 11 for injecting the ozone water generated by the second
ozone water generation unit 92 into the inside of the
separation membrane 2, and a control unit 12 for switching
20 the operation of the dissolution water supply unit 8, the
ozone gas supply unit 10, and the ozone water feeding unit 11
according to a step. The second ozone water generation unit
92 is provided with a dissolved ozone sensor 9b for measuring
the dissolved ozone concentration of the ozone water in the
25 second ozone water generation unit 92, and the control unit
41
12 is connected to the dissolved ozone sensor 9b via a signal
line 51.
[0052] The dissolution water supply unit 8 is connected to
the first ozone water generation unit 91 via a dissolution
5 water supply pipe 3c. The dissolution water is water in
which ozone gas is dissolved in the first ozone water
generation unit 91 and the second ozone water generation unit
92 to generate ozone water, and is supplied from the
dissolution water supply unit 8 through the dissolution water
10 supply pipe 3c to the first ozone water generation unit 91.
[0053] The first ozone water generation unit 91 is
connected to the second ozone water generation unit 92 via a
dissolution water feeding pipe 3f, and the second ozone water
generation unit 92 is connected to the ozone water feeding
15 unit 11 via an ozone water feeding pipe 3b1. The first ozone
water generation unit 91 and the second ozone water
generation unit 92 are configured to be capable of storing
liquid therein, and are capable of storing the dissolution
water supplied from the dissolution water supply unit 8 and
20 the ozone water generated from the dissolution water. The
dissolution water stored in the first ozone water generation
unit 91 is supplied to the second ozone water generation unit
92 via the dissolution water feeding pipe 3f.
[0054] A gas diffusing unit 91a and a gas diffusing unit
25 92a are provided at a bottom portion of the first ozone water
42
generation unit 91 and a bottom portion of the second ozone
water generation unit 92, respectively. The gas diffusing
unit 92a is connected to the ozone gas supply unit 10 via an
ozone gas supply pipe 3d, and the ozone gas supplied from the
5 ozone gas supply unit 10 is discharged as air bubbles from
the gas diffusing unit 92a, whereby the ozone gas is injected
into the dissolution water in the second ozone water
generation unit 92. An ozone gas transfer pipe 3g connected
to the gas diffusing unit 91a of the first ozone water
10 generation unit 91 is connected to an upper portion of the
second ozone water generation unit 92, and the ozone gas that
has not been dissolved in the second ozone water generation
unit 92 is supplied as dissolution ozone gas to the first
ozone water generation unit 91 via the ozone gas transfer
15 pipe 3g. The undissolved ozone gas supplied via the ozone
gas transfer pipe 3g is discharged as air bubbles from the
gas diffusing unit 91a, whereby the undissolved ozone gas is
injected into the dissolution water in the first ozone water
generation unit 91. The ozone gas that has not been
20 dissolved in the first ozone water generation unit 91 is
discharged to the outside of the system via an exhaust ozone
gas pipe 3e which is provided at an upper portion of the
first ozone water generation unit 91.
[0055] A connection portion (not shown) between the first
25 ozone water generation unit 91 and the dissolution water
43
supply pipe 3c is provided at one side wall of the first
ozone water generation unit 91, and a connection portion (not
shown) between the first ozone water generation unit 91 and
the dissolution water feeding pipe 3f is provided at another
5 side wall of the first ozone water generation unit 91. In
addition, the connection portion between the first ozone
water generation unit 91 and the dissolution water supply
pipe 3c is provided at a higher position than the connection
portion between the first ozone water generation unit 91 and
10 the dissolution water feeding pipe 3f. Accordingly, the
dissolution water flows in from a high position and the flow
of the dissolution water becomes downward flow, so that the
flow of ozone gas which is upward flow from the gas diffusing
unit 91a and the flow of the dissolution water are counter
15 flows. In this case, counter flow contact occurs between the
dissolution water and the ozone gas, so that the dissolution
efficiency in the first ozone water generation unit 91 is
improved.
[0056] A connection portion (not shown) between the second
20 ozone water generation unit 92 and the dissolution water
feeding pipe 3f is provided at one side wall of the second
ozone water generation unit 92, and a connection portion (not
shown) between the second ozone water generation unit 92 and
the ozone water feeding pipe 3b1 is provided at another side
25 wall of the second ozone water generation unit 92. In
44
addition, the connection portion between the second ozone
water generation unit 92 and the dissolution water feeding
pipe 3f is provided at a higher position than the connection
portion between the second ozone water generation unit 92 and
5 the ozone water feeding pipe 3b1. Accordingly, in the second
ozone water generation unit 92 as well, the flow of the
dissolution water and the flow of ozone gas are counter
flows, and the dissolution efficiency in the second ozone
water generation unit 92 is improved due to counter flow
10 contact.
[0057] In the “dissolution water supply step” in
Embodiment 2, first, the dissolution water is supplied from
the dissolution water supply unit 8 to the first ozone water
generation unit 91, and the dissolution water supplied to the
15 first ozone water generation unit 91 is supplied to the
second ozone water generation unit 92. At this time, supply
of the dissolution water to the second ozone water generation
unit 92 may be started after a predetermined amount of the
dissolution water is stored in the first ozone water
20 generation unit 91. Others are the same as in the
“dissolution water supply step” in Embodiment 1.
[0058] In the “ozone gas supply step” in Embodiment 2, as
shown in FIG. 4A, supply of the dissolution water from the
first ozone water generation unit 91 to the second ozone
25 water generation unit 92 is stopped. In addition, the ozone
45
gas supplied from the ozone gas supply unit 10 is dissolved
in the dissolution water in the second ozone water generation
unit 92, and the ozone gas that has not been dissolved in the
second ozone water generation unit 92 is supplied as
5 undissolved ozone gas to the first ozone water generation
unit 91 and dissolved in the dissolution water in the first
ozone water generation unit 91. Accordingly, generation of
ozone water by a semi-batch method is performed in both the
first ozone water generation unit 91 and the second ozone
10 water generation unit 92. The dissolution water in which the
undissolved ozone gas has been dissolved in the first ozone
water generation unit 91 is supplied to the second ozone
water generation unit 92 via the dissolution water feeding
pipe 3f, and ozone gas is further dissolved in the second
15 ozone water generation unit 92. Others are the same as in
the “ozone gas supply step” in Embodiment 1.
[0059] The “ozone water feeding step” in Embodiment 2 is a
step of feeding the ozone water stored in the second ozone
water generation unit 92 to the separation membrane 2 to
20 clean the separation membrane 2. In addition, the
“continuous operation step” in Embodiment 2 is a step of, as
shown in FIG. 4B, supplying the dissolution water from the
dissolution water supply unit 8 to the first ozone water
generation unit 91, feeding the ozone water from the second
25 ozone water generation unit 92, and also supplying the
46
dissolution water from the first ozone water generation unit
91 to the second ozone water generation unit 92. In
addition, similar to the case of the above-described ozone
gas supply step, ozone gas is dissolved in the dissolution
5 water both in the first ozone water generation unit 91 and
the second ozone water generation unit 92. Accordingly,
generation of ozone water by a continuous method is performed
in both the first ozone water generation unit 91 and the
second ozone water generation unit 92. Others are the same
10 as in the “continuous operation step” in Embodiment 1.
[0060] In Embodiment 2, the two ozone water generation
units are provided. However, three or more ozone water
generation units may be provided. The ozone gas that has not
been dissolved in a certain ozone water generation unit may
15 be supplied as undissolved ozone gas to another ozone water
generation unit, and the undissolved ozone gas may be
injected into the dissolution water stored in the other ozone
water generation unit. In addition, the undissolved ozone
gas that has not been dissolved in the other ozone water
20 generation unit may be supplied to still another ozone water
generation unit.
[0061] According to Embodiment 2, the same effect as in
Embodiment 1 can be achieved.
Moreover, a plurality of ozone water generation
25 units are provided, and an ozone gas transfer pipe through
47
which the ozone gas that has not been dissolved in one ozone
water generation unit is transferred as undissolved ozone gas
to another ozone water generation unit is provided.
Accordingly, the ozone gas that has not been dissolved in one
5 ozone water generation unit can be dissolved in another ozone
water generation unit without being discharged as exhaust
ozone gas, so that the dissolution efficiency of ozone gas
can be further improved.
[0062] Although the disclosure is described above in terms
10 of various exemplary embodiments and implementations, it
should be understood that the various features, aspects, and
functionality described in one or more of the individual
embodiments are not limited in their applicability to the
particular embodiment with which they are described, but
15 instead can be applied, alone or in various combinations to
one or more of the embodiments of the disclosure.
It is therefore understood that numerous
modifications which have not been exemplified can be devised
without departing from the scope of the present disclosure.
20 For example, at least one of the constituent components may
be modified, added, or eliminated. At least one of the
constituent components mentioned in at least one of the
preferred embodiments may be selected and combined with the
constituent components mentioned in another preferred
25 embodiment.
48
DESCRIPTION OF THE REFERENCE CHARACTERS
[0063] 1 membrane separation tank
2 separation membrane
5 3b1, 3b2 ozone water feeding pipe
3c dissolution water supply pipe
3d ozone gas supply pipe
3f dissolution water feeding pipe
3g ozone gas transfer pipe
10 8 dissolution water supply unit
9 ozone water generation unit
9b dissolved ozone sensor
91 first ozone water generation unit
92 second ozone water generation unit
15 10 ozone gas supply unit
11 ozone water feeding unit
12 control unit
13 ozone concentration reception unit
14 storage unit
20 15 determination unit
20 membrane separation activated sludge device
40, 401 membrane cleaning device
100, 200 membrane separation activated sludge
system
25
49
We Claim :
[1] A membrane cleaning device for cleaning a
separation membrane for separating contaminants contained in
treatment target water from the treatment target water, with
5 ozone water stored in an ozone water generation unit, the
membrane cleaning device comprising:
an ozone gas supply unit for supplying ozone gas to
the ozone water generation unit;
a dissolution water supply unit for supplying
10 dissolution water to the ozone water generation unit;
an ozone water feeding unit for feeding the ozone
water stored in the ozone water generation unit to the
separation membrane; and
a control unit for, in a state where the ozone gas
15 supply unit is caused to supply the ozone gas from the ozone
gas supply unit to the ozone water generation unit, causing
the dissolution water supply unit to supply the dissolution
water from the dissolution water supply unit to the ozone
water generation unit and causing the ozone water feeding
20 unit to feed the ozone water from the ozone water generation
unit to the separation membrane.
[2] The membrane cleaning device according to claim 1,
wherein, on the basis of a water quality of the ozone water,
25 the control unit determines whether or not to cause the
50
dissolution water supply unit to supply the dissolution water
from the dissolution water supply unit to the ozone water
generation unit and whether or not to cause the ozone water
feeding unit to feed the ozone water from the ozone water
5 generation unit to the separation membrane.
[3] The membrane cleaning device according to claim 2,
wherein
the control unit includes an ozone concentration
10 acquisition unit for acquiring a dissolved ozone
concentration of the ozone water, a storage unit for storing
a predetermined threshold value, and a determination unit for
determining whether or not feeding of the dissolution water
and the ozone water can be performed, and
15 when the dissolved ozone concentration is equal to
or higher than the predetermined threshold value,
in a state where the ozone gas supply unit is
caused to supply the ozone gas from the ozone gas supply unit
to the ozone water generation unit,
20 the determination unit causes the dissolution water
supply unit to supply the dissolution water from the
dissolution water supply unit to the ozone water generation
unit and causes the ozone water feeding unit to feed the
ozone water from the ozone water generation unit to the
25 separation membrane.
51
[4] The membrane cleaning device according to any one
of claims 1 to 3, wherein
the ozone water generation unit includes a first
5 ozone water generation unit connected to the dissolution
water supply unit, a second ozone water generation unit
connected to the ozone gas supply unit and the ozone water
feeding unit, an ozone gas transfer pipe through which ozone
gas that has not been dissolved in the second ozone water
10 generation unit is transferred as undissolved ozone gas to
the first ozone water generation unit, and a dissolution
water feeding pipe through which the dissolution water is fed
from the first ozone water generation unit to the second
ozone water generation unit, and
15 the undissolved ozone gas is dissolved in the
dissolution water in the first ozone water generation unit,
and the dissolution water in which the undissolved ozone gas
has been dissolved is fed from the first ozone water
generation unit to the second ozone water generation unit.
20
[5] A membrane separation activated sludge system
comprising: a membrane separation activated sludge device
having a membrane separation tank and a separation membrane
disposed in the membrane separation tank, and causing
25 treatment target water containing contaminants to flow
52
through the separation membrane in a filtration direction to
remove the contaminants from the treatment target water to
obtain treated water; and a membrane cleaning device cleaning
the separation membrane with ozone water stored in an ozone
5 water generation unit, wherein
the membrane cleaning device includes
an ozone gas supply unit for supplying ozone
gas to the ozone water generation unit;
a dissolution water supply unit for supplying
10 dissolution water to the ozone water generation unit;
an ozone water feeding unit for feeding the
ozone water stored in the ozone water generation unit to the
separation membrane; and
a control unit for, in a state where the ozone
15 gas supply unit is caused to supply the ozone gas from the
ozone gas supply unit to the ozone water generation unit,
causing the dissolution water supply unit to supply the
dissolution water from the dissolution water supply unit to
the ozone water generation unit and causing the ozone water
20 feeding unit to feed the ozone water from the ozone water
generation unit to the separation membrane.
[6] A membrane cleaning method for cleaning a
separation membrane for separating contaminants contained in
25 treatment target water from the treatment target water, with
53
ozone water stored in an ozone water generation unit, the
membrane cleaning method comprising:
an ozone gas supply step of supplying ozone gas to
the ozone water generation unit;
5 a dissolution water supply step of supplying
dissolution water to the ozone water generation unit;
an ozone water feeding step of feeding the ozone
water stored in the ozone water generation unit to the
separation membrane; and
10 a continuous operation step of performing the
dissolution water supply step and the ozone water feeding
step while supplying the ozone gas to the ozone water
generation unit.
15 [7] The membrane cleaning method according to claim 6,
wherein a step to be performed is switched between the ozone
gas supply step and the continuous operation step on the
basis of a water quality of the ozone water.
20 [8] The membrane cleaning method according to claim 7,
wherein when a dissolved ozone concentration of the ozone
water is equal to or higher than a predetermined threshold
value, the continuous operation step is set as the step to be
performed.
25
54
[9] The membrane cleaning method according to any one
of claims 6 to 8, wherein
the ozone water generation unit includes a first
ozone water generation unit to which the dissolution water is
5 supplied, and a second ozone water generation unit to which
the ozone gas is supplied, and
the ozone gas that has not been dissolved in the
second ozone water generation unit is transferred as
undissolved ozone gas to the first ozone water generation
10 unit, the undissolved ozone gas is dissolved in the
dissolution water in the first ozone water generation unit,
and the dissolution water in which the undissolved ozone gas
has been dissolved is fed from the first ozone water
generation unit to the second ozone water generation unit.