FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
FILTRATION MEMBRANE TREATMENT DEVICE, MEMBRANE FILTRATION
DEVICE, AND FILTRATION MEMBRANE TREATMENT 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 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED
2
DESCRIPTION
TECHNICAL FIELD
[0001] The present disclosure relates to a filtration
membrane treatment device, a membrane filtration device, and
5 a filtration membrane treatment method that enable ozone
treatment of a filtration membrane with a small variation.
BACKGROUND ART
[0002] If a treatment-target liquid is subjected to
10 separation by a filtration membrane, the filtration membrane
may be clogged with impurities and microorganisms in water.
Such clogging can be prevented by improving the water
permeability of such a filtration membrane in treatment of
the filtration membrane. As methods for improving the water
15 permeability of a filtration membrane, there are methods such
as a method in which a produced filtration membrane is
chemically treated and hydrophilized.
[0003] For example, Patent Document 1 describes a method
including: treating a polyvinylidene-based resin porous
20 membrane with a base, and then treating the polyvinylidenebased
resin porous membrane with an aqueous solution that
contains hydrogen peroxide or ozone; and further treating the
polyvinylidene-based resin porous membrane with an aqueous
solution that contains at least one type of salt selected
25 from among perchloric acid salts, perbromates, and periodic
3
acid salts, to perform hydrophilization. Furthermore, for
example, Patent Document 2 describes a method including
stopping passage of ozone water if a difference in pressure
reaches a predetermined value when a membrane module is being
5 cleaned with the ozone water, to perform hydrophilization.
CITATION LIST
PATENT DOCUMENT
[0004] Patent Document 1: Japanese Laid-Open Patent
10 Publication No. 2004-230280
Patent Document 2: Japanese Laid-Open Patent
Publication No. 2004-249168
SUMMARY OF THE INVENTION
15 PROBLEMS TO BE SOLVED BY THE INVENTION
[0005] Conventional filtration membrane treatment devices
and filtration membrane treatment methods involve:
hydrophilizing a membrane under a certain fixed condition
that, for example, the membrane is treated by being immersed
20 for 100 hours in ozone water having a concentration of 10
ppm; and evaluating the degree of hydrophilization with use
of, as an index of hydrophilization, the ratio between the
permeation amount of pure water after hydrophilization and
the permeation amount of pure water before hydrophilization.
25 In this method, a membrane is hydrophilized under a fixed
4
condition. Thus, this method takes into account neither the
fact that there is an individual difference among membranes
nor the fact that even identical polyvinylidene-based resin
porous membranes have different characteristics depending on
5 the manufacturer of the membranes. Therefore, a problem
arises in that there is a variation in the degree of
hydrophilization among membranes and appropriate treatment of
the membranes cannot be efficiently performed.
[0006] The present disclosure has been made to solve the
10 above problem, and an object of the present disclosure is to
provide a filtration membrane treatment device, a membrane
filtration device, and a filtration membrane treatment method
that enable ozone treatment of a filtration membrane with a
small variation.
15
SOLUTION TO THE PROBLEMS
[0007] A filtration membrane treatment device according to
the present disclosure is a filtration membrane treatment
device which performs ozone treatment on a filtration
20 membrane, the filtration membrane treatment device including:
a first supply portion which supplies an ozonecontaining
fluid to the filtration membrane;
a measurement portion which measures a measurement
value based on a pressure to the filtration membrane; and
25 a control portion which adjusts, on the basis of a
5
change in the measurement value measured by the measurement
portion, a supply amount of the ozone-containing fluid to be
supplied by the first supply portion.
A membrane filtration device according to the
5 present disclosure is a membrane filtration device which
treats a treatment-target liquid with use of the abovedescribed
filtration membrane treatment device, the membrane
filtration device including:
a storage tank which stores the treatment-target
10 liquid and in which the filtration membrane is immersed; and
a transfer portion which transfers, to outside of
the storage tank, the treatment-target liquid having been
filtered by the filtration membrane, wherein
the control portion causes the transfer portion to
15 stop and causes the first supply portion to supply the ozonecontaining
fluid to the filtration membrane immersed inside
the storage tank.
A filtration membrane treatment method according to
the present disclosure is a filtration membrane treatment
20 method including:
a supply step of supplying an ozone-containing
fluid to a filtration membrane;
a measurement step of measuring a measurement value
based on a pressure to the filtration membrane; and
25 a control step of adjusting a supply amount of the
6
ozone-containing fluid on the basis of a change in the
measurement value.
EFFECT OF THE INVENTION
5 [0008] The filtration membrane treatment device, the
membrane filtration device, and the filtration membrane
treatment method according to the present disclosure enable
ozone treatment of a filtration membrane with a small
variation.
10
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] [FIG. 1] FIG. 1 is a diagram showing a
configuration of a filtration membrane treatment device
according to embodiment 1.
15 [FIG. 2] FIG. 2 is a flowchart of a filtration
membrane treatment method by the filtration membrane
treatment device shown in FIG. 1.
[FIG. 3] FIG. 3 is a diagram showing a
configuration of another filtration membrane treatment device
20 according to embodiment 1.
[FIG. 4] FIG. 4 is a diagram showing a
configuration of another filtration membrane treatment device
according to embodiment 1.
[FIG. 5] FIG. 5 is a diagram showing a
25 configuration of another filtration membrane treatment device
7
according to embodiment 1.
[FIG. 6] FIG. 6 is a diagram showing a
configuration of another filtration membrane treatment device
according to embodiment 1.
5 [FIG. 7] FIG. 7 is a diagram showing a
configuration of another filtration membrane treatment device
according to embodiment 1.
[FIG. 8] FIG. 8 is a diagram showing a
configuration of a filtration membrane treatment device
10 according to embodiment 2.
[FIG. 9] FIG. 9 is a diagram showing a
configuration of another filtration membrane treatment device
according to embodiment 2.
[FIG. 10] FIG. 10 is a diagram showing a
15 configuration of a filtration membrane treatment device
according to embodiment 3.
[FIG. 11] FIG. 11 is a flowchart of a filtration
membrane treatment method by the filtration membrane
treatment device shown in FIG. 10.
20 [FIG. 12] FIG. 12 is a diagram showing a
configuration of another filtration membrane treatment device
according to embodiment 3.
[FIG. 13] FIG. 13 is a diagram showing a
configuration of a membrane filtration device in which a
25 filtration membrane treatment device is used, according to
8
embodiment 4.
[FIG. 14] FIG. 14 is a table showing the
specifications of filtration membrane treatment devices used
in Example 1, Comparative Example 1, and Comparative Example
5 2.
[FIG. 15] FIG. 15 is a table showing results of
Example 1.
[FIG. 16] FIG. 16 is a table showing results of
Comparative Example 1 and Comparative Example 2.
10
DESCRIPTION OF EMBODIMENTS
[0010] Embodiment 1
FIG. 1 is a diagram showing a configuration of a
filtration membrane treatment device according to embodiment
15 1. FIG. 2 is a flowchart of a filtration membrane treatment
method by the filtration membrane treatment device shown in
FIG. 1. FIG. 3 to FIG. 7 are diagrams showing configurations
of other filtration membrane treatment devices according to
embodiment 1. In each drawing, the filtration membrane
20 treatment device is for performing ozone treatment on a
filtration membrane 1 to purge the filtration membrane 1
having treated a treatment-target liquid, thereby using the
filtration membrane 1 for treatment of the treatment-target
liquid again.
25 [0011] Thus, the filtration membrane 1 is inevitably
9
formed of a material having ozone resistance. In addition,
the filtration membrane 1 is formed of a material that is
hydrophilized by ozone. Specifically, it is possible to use,
for example, a material formed of a fluorine-based
5 macromolecule. Representative examples of the material are
polyvinylidene difluoride (PVDF) and polytetrafluoroethylene
(PTFE).
[0012] The shape of the filtration membrane 1 is not
particularly limited, and, for example, a hollow fiber
10 membrane, a flat membrane, or a tubular membrane can be used.
In addition, a module type of the filtration membrane 1 is
not particularly limited, and, for example, an internal
pressure type module or an external pressure type module
accommodated in a cylindrical container, or an immersion type
15 module, can be used. Here, description will be given with an
example in which a hollow fiber membrane module of an
immersion type is used.
[0013] The filtration membrane treatment device includes a
first supply portion 3, a measurement portion 8, and a
20 control portion 11. The first supply portion 3 supplies an
ozone-containing fluid to the filtration membrane 1. The
measurement portion 8 measures a measurement value H based on
a pressure to the filtration membrane 1. The control portion
11 adjusts, on the basis of a change in the measurement value
25 H measured by the measurement portion 8, a supply amount of
10
the ozone-containing fluid to be supplied by the first supply
portion 3.
[0014] Here, the filtration membrane 1 is a hollow fiber
membrane module of an immersion type and thus filters the
5 treatment-target liquid from a primary side to a secondary
side. In addition, since a hollow fiber membrane module of
an immersion type is used as the filtration membrane 1, the
ozone-containing fluid will be described using an example of
a pouring method similar to so-called “reverse-pressure
10 cleaning” in which the ozone-containing fluid is poured from
the secondary side toward the primary side.
[0015] The filtration membrane 1 is accommodated inside
the accommodating tank 2. The accommodating tank 2 is filled
with a liquid 4 which is, for example, water. Thus, the
15 filtration membrane 1 is immersed in the liquid 4. This is
because the filtration membrane 1 is a hollow fiber membrane
module of an immersion type and performance deterioration
thereof due to drying has to be prevented. Therefore, a
filtration membrane 1 in which performance deterioration due
20 to drying does not occur does not necessarily need to be
subjected to ozone treatment in a state of being immersed in
the liquid 4 inside the accommodating tank 2.
[0016] The filtration membrane 1, the measurement portion
8, and the first supply portion 3 are connected by a first
25 pipe 7. The first supply portion 3 includes: a first
11
reservoir 5 which stores the ozone-containing fluid; and a
first pump 6 which is for supplying ozone from the first
reservoir 5 through the first pipe 7 to the filtration
membrane 1. As for the ozone-containing fluid, for example,
5 use of one or more types of ozone gas, ozone water produced
by dissolving ozone in a solvent such as water, or mixed
water obtained by mixing, with ozone water, a substance that
promotes generation of radicals due to decomposition of ozone,
is assumed.
10 [0017] The measurement portion 8 includes, as a
constituent for measuring the measurement value H based on
the pressure to the filtration membrane 1, a pressure gauge 9
which measures a pressure value in the first pipe 7 as a pipe
through which the fluid (here, ozone-containing fluid) to be
15 supplied to the filtration membrane 1 flows. The
specifications of the pressure gauge 9 is not limited as long
as the pressure gauge 9 is of a type that allows the measured
pressure value to be sent to the control portion 11. The
control portion 11 receives the measurement value H from the
20 pressure gauge 9 of the measurement portion 8 and controls,
by means of the first pump 6, the supply amount of the ozonecontaining
fluid to be supplied through the first pipe 7, on
the basis of a change in the measurement value H. The
accommodating tank 2 is provided with a first discharge
25 portion 10 by which an excess portion of the ozone-containing
12
fluid or the liquid 4 is discharged to outside.
[0018] Next, a filtration membrane treatment method by the
filtration membrane treatment device according to embodiment
1 configured as described above, will be described. First,
5 the filtration membrane treatment device according to the
present embodiment 1 is configured as described above, and
the change in the measurement value H based on the pressure
at the time of supplying the ozone-containing fluid to the
filtration membrane 1 is observed so that the degree of ozone
10 treatment is quantified and a timing of completion of ozone
treatment is determined.
[0019] Regarding this, earnest studies by the present
inventors led to the following findings. When the ozonecontaining
fluid is brought into contact with the filtration
15 membrane 1, a hydrophilic functional group such as a hydroxyl
group is added onto the molecular chain of the material that
forms the filtration membrane 1 and that is hydrophilized by
ozone. Thus, the hydrophilicity of the filtration membrane 1
is improved. Therefore, the water permeability (i.e., the
20 easiness of passage of water) of the filtration membrane 1 is
improved. Judging from this, it can be determined that the
filtration membrane 1 is purged by ozone treatment.
[0020] The present inventors further found that, if the
ozone-containing fluid is supplied to the filtration membrane
25 1 and ozone treatment of the filtration membrane 1 is
13
monitored and evaluated on the basis of the change in the
measurement value H based on the pressure, determination can
be performed by interpretation as an index of the water
permeability (the easiness of passage of water) of the
5 filtration membrane 1. Moreover, the present inventors found
that: if ozone treatment of the filtration membrane 1 is
performed by supplying the ozone-containing fluid, the
measurement value H based on the pressure to the filtration
membrane 1 gradually decreases; and, if the ozone treatment
10 is completed, the change in the measurement value H becomes
very small. The reason for this was found to be as follows,
as a result of earnest studies by the present inventors.
There is a limit to the amount of a hydrophilic group that
can be added onto the aforementioned molecular chain of the
15 filtration membrane 1, and, if the limit is exceeded, the
change in the degree of hydrophilization becomes very small
even when the ozone-containing fluid is supplied to the
filtration membrane 1.
[0021] Consequently, the present inventors found that
20 determination based on the change in the measurement value H
leads to decision of a breakpoint of the ozone treatment of
the filtration membrane 1, i.e., a point at which the ozone
treatment should be completed. As described above, the ozone
treatment of the filtration membrane 1 is synonymous with
25 hydrophilization of the filtration membrane 1. Therefore,
14
the present inventors found a limit of the hydrophilization
of the filtration membrane 1, i.e., a point at which the
hydrophilization should be completed. It is noted that the
above described findings apply also to the other embodiments,
5 and description thereof is omitted, as appropriate.
[0022] Hereinafter, the filtration membrane treatment
method will be described with reference to the flowchart in
FIG. 2 in consideration of these findings. First, the
control portion 11 drives the first pump 6, to perform a
10 supply step of supplying the ozone-containing fluid from the
first reservoir 5 of the first supply portion 3 through the
first pipe 7 to the filtration membrane 1 (step ST1 in FIG.
2). It is noted that the ozone-containing fluid continues to
be supplied such that the supply amount thereof is a fixed
15 amount.
[0023] Next, a measurement step of measuring the
measurement value H based on the pressure to the filtration
membrane 1, is performed while the supply step is continued.
First, the measurement portion 8 measures, as the measurement
20 value H, a first measurement value H1 after the first supply
portion 3 supplies the ozone-containing fluid for a first
time period T1, and the measurement portion 8 sends the first
measurement value H1 to the control portion 11 (step ST2 in
FIG. 2). Then, a second measurement value H2 after the
25 ozone-containing fluid is supplied for a second time period
15
T2 which is longer than the first time period T1, is measured
and sent to the control portion 11 (step ST3 in FIG. 3).
[0024] Preferable ranges of the first time period T1 and a
time period from the end of the first time period T1 to the
5 start of the second time period T2, for the measurement
performed as described above, are 1 minute to 20 minutes. If
the time periods are shorter than 1 minute, ozone treatment
has hardly progressed, and the difference from a previous
measurement value H or from an initial-state value is unclear,
10 whereby there is a possibility that completion of the ozone
treatment cannot be determined. Meanwhile, if the time
periods are longer than 20 minutes, the time period to the
next measurement is elongated, whereby there is a possibility
that, even though the ozone treatment has actually been
15 completed, determination of the completion is delayed and the
ozone treatment is unnecessarily continued. It is noted that
the first time period T1 and the time period from the end of
the first time period T1 to the start of the second time
period T2 may be equal to each other or may be individually
20 set. For example, it can also be assumed that: each time
period is initially set to be long at the start of the ozone
treatment; and the time period is set to be short at
approximation to a time point at which the treatment is
ordinarily considered to end.
25 [0025] Then, a control step of adjusting the supply amount
16
of the ozone-containing fluid on the basis of a change in the
measurement value H, is performed. The control portion 11
determines whether or not a change ratio α in the following
expression 1 between the first measurement value H1 and the
5 second measurement value H2 is equal to or smaller than a
threshold value α1 (the following expression 2) (step ST4 in
FIG. 2).
[0026] |H1-H2|÷|H1|=α ••• expression 1
[0027] α≤α1 ••• expression 2
10 [0028] If the change ratio α is equal to or smaller than
the threshold value α1 (YES), the supply of the ozonecontaining
fluid by the first supply portion 3 is suppressed.
Here, the control portion 11 causes the first pump 6 to stop,
to end the supply of the ozone-containing fluid to the
15 filtration membrane 1 (step ST5 in FIG. 2).
[0029] Meanwhile, if the change ratio α is larger than the
threshold value α1 (NO), the supply of the ozone-containing
fluid by the first supply portion 3 is continued, and the
process from step ST3 is repeated. If the operation is
20 repeated from step ST3, the previously measured second
measurement value H2 at the elapse of the second time period
T2 is regarded as a first measurement value H1 at the elapse
of the first time period T1 for the repetition. Then, a
second measurement value H2 at the subsequent elapse of the
25 second time period T2, is newly measured, and the method
17
described above is repeated. That is, the first measurement
value H1 at the elapse of the first time period T1 is the
previous measurement value H, and the second measurement
value H2 at the elapse of the second time period T2 is the
5 present measurement value H.
[0030] A preferable range of the threshold value α1 for
the change ratio α is 0 to 0.5. If the threshold value α1 is
larger than 0.5, there is a possibility that ozone treatment
is determined to have been completed even though there is
10 room for the ozone treatment to progress.
[0031] In the above-described embodiment 1, an example in
which the pressure value in the first pipe 7 is used as the
measurement value H has been described. However, the present
disclosure is not limited to this example. For example, the
15 trans-membrane pressure (TMP) value between the primary side
and the secondary side of the filtration membrane 1 may be
measured and used as the measurement value H. In this case,
for example, pressure gauges may be disposed respectively on
the primary side and the secondary side of the filtration
20 membrane 1, and a trans-membrane pressure value may be
calculated from the values at the pressure gauges and used as
the measurement value H. Alternatively, if a filtration
membrane 1 of an immersion type such as one in FIG. 1 is used,
a TMP may be calculated from a liquid level inside the
25 accommodating tank 2 and the pressure value at the pressure
18
gauge 9 and used as the measurement value H.
[0032] In addition, in the above-described embodiment 1,
an example in which the first supply portion 3 includes the
first reservoir 5 for storing the ozone-containing fluid and
5 supplies the ozone-containing fluid, has been described.
Although the ozone-containing fluid has not been particularly
described, another case can be assumed in which ozone gas is
used as the ozone-containing fluid. As shown in FIG. 3, a
first supply portion 3 includes an ozone gas generator 12.
10 The control portion 11 controls the amount of ozone gas to be
generated from the ozone gas generator 12. The ozone gas is
supplied through the first pipe 7 directly to the filtration
membrane 1, whereby the filtration membrane can be treated in
the same manner as in the above-described embodiment 1.
15 [0033] In the case where ozone gas is used as the ozonecontaining
fluid, the concentration of the ozone gas is
preferably 1 ppm to 1000 ppm. The reason is as follows. If
the concentration of the ozone gas is lower than 1 ppm, the
ozone treatment effect is low and it takes time to complete
20 ozone treatment. Meanwhile, if the concentration of the
ozone gas is higher than 1000 ppm, a member forming the
filtration membrane 1, the first pipe 7, or the like may be
degraded.
[0034] Another example of using ozone gas is shown in FIG.
25 4 in which a first supply portion 3 includes the ozone gas
19
generator 12, the first reservoir 5, and the first pump 6.
The control portion 11 controls the amount of ozone gas to be
generated from the ozone gas generator 12. The generated
ozone gas is stored as an ozone-containing fluid in the first
5 reservoir 5, and the stored ozone gas is supplied via the
first pump 6 to the filtration membrane 1, whereby the
filtration membrane can be treated in the same manner as in
the above-described embodiment 1. In this case, the inside
of the first reservoir 5 may be filled with a porosity such
10 as silica gel as an adsorbent so that the ozone gas is stored
while being adsorbed and condensed.
[0035] As another example, a case can be assumed in which
ozone water is used as the ozone-containing fluid. As shown
in FIG. 5, a first supply portion 3 includes the ozone gas
15 generator 12, a first reservoir 50, and the first pump 6.
The first reservoir 50 includes: a second pipe 13 through
which a solvent such as water for dissolving ozone gas is
supplied; and a second discharge portion 14 by which excess
ozone gas in the first reservoir 5 is discharged to outside.
20 Through the second pipe 13, for example, water is supplied to
the first reservoir 50. Then, ozone gas is supplied from the
ozone gas generator 12 into the first reservoir 50, and ozone
water is produced and stored in the first reservoir 5. The
stored ozone water is supplied via the first pump 6 to the
25 filtration membrane 1, whereby the filtration membrane can be
20
treated in the same manner as in the above-described
embodiment 1.
[0036] In the case where ozone water is used as the ozonecontaining
fluid, the concentration of the dissolved ozone
5 contained in the ozone water to be supplied to the filtration
membrane 1 is preferably 1 mg/L to 100 mg/L. The reason is
as follows. If the concentration of the dissolved ozone is
lower than 1 mg/L, the ozone treatment effect is low and it
takes time to complete the treatment. Meanwhile, if the
10 concentration of the dissolved ozone is higher than 100 mg/L,
there is a possibility that a large amount of oxygen gas
bubbles is generated owing to decomposition of ozone and
hinder the supply of the ozone water to the filtration
membrane 1.
15 [0037] In the case where ozone water is used as the ozonecontaining
fluid, a pH adjuster such as hydrochloric acid or
sulfuric acid may be added to the ozone water. The pH of the
ozone water to be supplied to the filtration membrane 1 is
not particularly limited as long as the pH is within a range
20 corresponding to the pH resistance of the filtration membrane
1. For example, in a case where polyvinylidene difluoride
(PVDF) is used for the filtration membrane 1, any pH can be
selected from between 1 pH to 14 pH as the pH of the ozone
water.
25 [0038] As another example, a case can be assumed in which
21
mixed water obtained by mixing, with ozone water, a substance
that promotes generation of radicals due to decomposition of
ozone (hereinafter, abbreviated as a promoter) is used as the
ozone-containing fluid. In this case, the mixed water
5 produced by mixing the ozone water and the promoter in
advance is stored in the first reservoir 5 shown in FIG. 1,
and the stored mixed water is supplied via the first pump 6
to the filtration membrane 1, whereby the filtration membrane
can be treated in the same manner as in the above-described
10 embodiment 1.
[0039] Another example of the case of using the mixed
water is shown in FIG. 6 in which a first supply portion 3
includes the ozone gas generator 12, the first reservoir 50,
the first pump 6, and an adding portion 15. The adding
15 portion 15 is for adding the promoter. A third pipe 16
connecting the adding portion 15 and the first pipe 7 to each
other is provided. The control portion 11 controls the
amount of the promoter to be added by the adding portion 15.
[0040] The promoter is supplied from the adding portion 15
20 through the third pipe 16 to the first pipe 7, the promoter
is mixed with the ozone water in the first pipe 7, and the
obtained mixed water is supplied to the filtration membrane 1,
whereby the filtration membrane can be treated in the same
manner as in the above-described embodiment 1. As the
25 promoter, for example, oxidizing agents such as hydrogen
22
peroxide water and sodium hypochlorite and alkalis such as
caustic soda and potassium hydroxide, can be used. Among
them, one type may be selected, or a plurality of types may
be used.
5 [0041] In the above-described embodiment 1, an example in
which the first supply portion 3 pours the ozone-containing
fluid from the secondary side to the primary side of the
filtration membrane 1, has been described. However, the
present disclosure is not limited to this example. An
10 example in which the first supply portion 3 supplies the
ozone-containing fluid from the primary side to the secondary
side of the filtration membrane 1, will be described. As
shown in FIG. 7, the ozone-containing fluid is supplied from
the first pump 6 through the first pipe 7 to the
15 accommodating tank 2. The ozone-containing fluid is
suctioned via a suction pump 30 from the first pipe 7
connected to the filtration membrane 1, and the ozonecontaining
fluid is supplied to the filtration membrane 1, so
that ozone treatment is performed on the filtration membrane
20 1. Then, the ozone-containing fluid suctioned via the
suction pump 30 is discharged to outside by the first
discharge portion 10. Also with this configuration, the
filtration membrane can be treated in the same manner as in
the above-described embodiment 1. It is noted that, in this
25 case, the pressure value measured by the pressure gauge 9 is
23
a negative value. However, since values are calculated with
absolute values as indicated in the above-described
expression 1, the calculation can be performed in the same
manner.
5 [0042] The filtration membrane treatment device according
to embodiment 1 configured as described above is a filtration
membrane treatment device which performs ozone treatment on a
filtration membrane, the filtration membrane treatment device
including:
10 a first supply portion which supplies an ozonecontaining
fluid to the filtration membrane;
a measurement portion which measures a measurement
value based on a pressure to the filtration membrane; and
a control portion which adjusts, on the basis of a
15 change in the measurement value measured by the measurement
portion, a supply amount of the ozone-containing fluid to be
supplied by the first supply portion.
The filtration membrane treatment method according
to embodiment 1 includes:
20 a supply step of supplying an ozone-containing
fluid to a filtration membrane;
a measurement step of measuring a measurement value
based on a pressure to the filtration membrane; and
a control step of adjusting a supply amount of the
25 ozone-containing fluid on the basis of a change in the
24
measurement value.
Thus, if the ozone-containing fluid is supplied to
the filtration membrane and ozone treatment of the filtration
membrane is monitored and evaluated on the basis of the
5 change in the measurement value based on the pressure,
determination can be performed by interpretation as an index
of the water permeability (the easiness of passage of water)
of the filtration membrane. Consequently, the point of
completion of ozone treatment of the filtration membrane can
10 be determined according to improvement in the water
permeability due to progression of hydrophilization of the
filtration membrane. Therefore, hydrophilization potential
latently belonging to the filtration membrane is maximized,
and ozone treatment can be assuredly completed regardless of
15 a variation based on an individual difference dependent on
the types, the properties, or manufacturing of filtration
membranes.
[0043] The filtration membrane filters a treatment-target
liquid from a primary side to a secondary side, and
20 the first supply portion is configured to either
pour the ozone-containing fluid from the secondary side to
the primary side of the filtration membrane, or suction or
inject the ozone-containing fluid from the primary side to
the secondary side of the filtration membrane. Thus, ozone
25 treatment can be performed according to the configuration of
25
the filtration membrane.
[0044] The measurement portion measures, as the
measurement value, each of a first measurement value H1 after
the first supply portion supplies the ozone-containing fluid
5 for a first time period and a second measurement value H2
after the supply is performed for a second time period which
is longer than the first time period.
The control portion causes the first supply portion
to continue the supply of the ozone-containing fluid if a
10 change ratio α in expression 1 between the first measurement
value H1 and the second measurement value H2 is equal to or
smaller than a threshold value α1, and causes the first
supply portion to suppress the supply of the ozone-containing
fluid if the change ratio α is larger than the threshold
15 value α1.
The measurement step includes measuring each of a
first measurement value H1 after the ozone-containing fluid
is supplied for a first time period and a second measurement
value H2 after the supply is performed for a second time
20 period which is longer than the first time period.
The control step includes: continuing the supply of
the ozone-containing fluid if a change ratio α in expression
1 between the first measurement value H1 and the second
measurement value H2 is equal to or smaller than a threshold
25 value α1; and suppressing the supply of the ozone-containing
26
fluid if the change ratio α is larger than the threshold
value α1.
Thus, it is possible to more assuredly control
ozone treatment of the filtration membrane on the basis of a
5 change between the measurement values which are the first
measurement value and the second measurement value based on
the pressures to the filtration membrane.
[0045] The control portion causes the first supply portion
to end the supply of the ozone-containing fluid if the change
10 ratio α between the measurement values is larger than the
threshold value α1. Thus, wasteful supply of the ozonecontaining
fluid can be reduced in ozone treatment of the
filtration membrane.
[0046] The first supply portion supplies, as the ozone15
containing fluid, at least one of ozone gas, ozone water
obtained by dissolving ozone, or ozone-mixed water obtained
by mixing, with ozone water, a substance that promotes
generation of radicals due to decomposition of ozone. Thus,
the filtration membrane can be assuredly subjected to ozone
20 treatment.
[0047] Regarding the measurement value from the
measurement portion, a pressure value in a pipe through which
a fluid being supplied to the filtration membrane is flowing
is measured as the measurement value, or a trans-membrane
25 pressure value between inside and outside of the filtration
27
membrane at a time of passage of the fluid through the
filtration membrane is measured as the measurement value.
Thus, the measurement value regarding the filtration membrane
can be assuredly measured, whereby the filtration membrane
5 can be assuredly subjected to ozone treatment.
[0048] The filtration membrane is formed of a material
that is hydrophilized by ozone, and
the control portion determines a degree of
hydrophilization of the filtration membrane on the basis of
10 the change in the measurement value. Thus, the degree of
hydrophilization can be determined through ozone treatment of
the filtration membrane according to the configuration of the
filtration membrane.
[0049] Embodiment 2
15 FIG. 8 and FIG. 9 are diagrams showing
configurations of filtration membrane treatment devices
according to embodiment 2. In the above-described embodiment
1, an example has been described in which the pressure value
of the fluid in the first pipe 7 or the trans-membrane
20 pressure (TMP) value of the filtration membrane 1 is used as
the measurement value H based on the pressure to the
filtration membrane 1. Meanwhile, in the present embodiment
2, a case will be described in which a value obtained in
consideration of a flow rate value of the fluid in the first
25 pipe 7 in addition to these measurement values is used as the
28
measurement value H based on the pressure to the filtration
membrane 1.
[0050] In the drawings, the same portions as those in the
above-described embodiment 1 will be denoted by the same
5 reference characters, and description thereof is omitted. A
measurement portion 8 in FIG. 8 includes: the pressure gauge
9; and a flowmeter 17 provided to the first pipe 7. A
measurement portion 8 in FIG. 9 includes: the pressure gauge
9; and the flowmeter 17 and a thermometer 170 provided to the
10 first pipe 7. A filtration membrane treatment method by the
filtration membrane treatment devices shown in FIG. 8 and FIG.
9 is performed according to the flowchart shown in FIG. 2 in
the same manner as in the above-described embodiment 1.
However, the filtration membrane treatment device shown in
15 FIG. 8 according to the present embodiment 2 is different in
that a value obtained by calculating the ratio between a
pressure value in the first pipe 7 obtained by the pressure
gauge 9 and a flow rate value in the first pipe 7 obtained by
the flowmeter 17, is used as the measurement value H.
20 [0051] That is, in the present embodiment 2, the value
calculated according to the following expression 3 is used as
the measurement value H.
[0052] H=Q÷P ••• expression 3
H: measurement value (L/h/kPa)
25 Q: flow rate value (L/h)
29
P: pressure value (kPa) or trans-membrane pressure
value (kPa)
[0053] The filtration membrane treatment method is
performed in the same manner as in the above-described
5 embodiment 1 with use of this measurement value H.
[0054] If the effective area of the filtration membrane 1
is known, the value calculated according to the following
expression 4 is used as the measurement value H.
[0055] H=Q÷A÷P ••• expression 4
10 A: effective area of filtration membrane 1 (m2)
[0056] The filtration membrane treatment method is
performed in the same manner as in the above-described
embodiment 1 with use of this measurement value H.
[0057] Meanwhile, in the filtration membrane treatment
15 device shown in FIG. 9 according to the present embodiment 2,
a correction based on the temperature of the ozone-containing
fluid in addition to the above-described flow rate value is
applied to the measurement value H. Specifically, the
measurement value H obtained according to the above-described
20 expression 3 or the above-described expression 4 is subjected
to a process as in the following expression 5, whereby a
measurement value H’ after the correction is obtained.
[0058] H’=H×(μt÷μs) ••• expression 5
H’: measurement value after correction based on
25 temperature
30
μs: viscosity value of ozone-containing fluid at
any reference temperature
μt: viscosity value of ozone-containing fluid at
temperature at time of measurement of measurement value
5 [0059] It is noted that, in the case of using water as a
solvent for ozone, the viscosity of the ozone-containing
fluid is equal to the viscosity of the water, and thus the
publicly-known viscosities of water can be used as μs and μt.
In determining μs, a reference temperature needs to be
10 arbitrarily selected but is not particularly limited. For
example, the reference temperature may be set, as appropriate,
to any normal temperature from 15°C to 30°C. The filtration
membrane treatment method is performed in the same manner as
in the above-described embodiment 1 with use of this
15 measurement value H’.
[0060] In each filtration membrane treatment device
according to embodiment 2 configured as described above, the
same advantageous effects as those in the above-described
embodiment 1 are exhibited, as a matter of course, and in
20 addition, regarding the measurement value from the
measurement portion, a ratio between the pressure value or
the trans-membrane pressure value and a flow rate value of
the fluid being supplied to the filtration membrane is
measured as the measurement value, and thus
25 a measurement value can be detected with excellent
31
accuracy without being influenced by the flow rate of the
ozone-containing fluid, whereby ozone treatment of the
filtration membrane can be optimally controlled.
[0061] Embodiment 3
5 FIG. 10 is a diagram showing a configuration of a
filtration membrane treatment device according to embodiment
3. FIG. 11 is a flowchart of a filtration membrane treatment
method by the filtration membrane treatment device shown in
FIG. 10. FIG. 12 is a diagram showing a configuration of
10 another filtration membrane treatment device according to
embodiment 3. In the drawings, the same portions as those in
the above-described embodiments are denoted by the same
reference characters, and description thereof is omitted. In
the above-described embodiments, examples have been described
15 in which the measurement value H based on the pressure to the
filtration membrane 1 is measured while the ozone-containing
fluid is being supplied to the filtration membrane 1.
Meanwhile, in the present embodiment 3, a case will be
described in which, when the measurement value H based on the
20 pressure to the filtration membrane 1 is measured, the ozonecontaining
fluid to the filtration membrane 1 is temporarily
stopped for the measurement.
[0062] In the drawings, the same portions as those in the
above-described embodiments are denoted by the same reference
25 characters, and description thereof is omitted. A second
32
supply portion 18 which supplies a measurement fluid
different from the ozone-containing fluid to the filtration
membrane 1, is provided. The second supply portion 18
includes a second reservoir 20 and a second pump 19. The
5 second reservoir 20 stores the measurement fluid. As long as
the measurement fluid is different from the ozone-containing
fluid, the measurement fluid is not particularly limited, and
any fluid containing no substance that causes contamination
of the filtration membrane 1 can be used. For example, use
10 of tap water, pure water, ultrapure water, an alkaline
chemical such as caustic soda, or an acidic chemical such as
hydrochloric acid, sulfuric acid, or citric acid, is assumed.
[0063] The second pump 19 supplies the measurement fluid
from the second reservoir 20 through a fourth pipe 21 to the
15 first pipe 7 and the filtration membrane 1. The first pipe 7
is provided with a valve 23, and the fourth pipe 21 is
provided with a valve 22.
[0064] When the measurement portion 8 measures the
measurement value H, the control portion 11 causes the valve
20 23 of the first pipe 7 to close and causes the first pump 6
to stop, thereby causing the first supply portion 3 to stop
the supply of the ozone-containing fluid. Meanwhile, the
control portion 11 causes the valve 22 of the fourth pipe 21
to open and drives the second pump 19, thereby causing the
25 measurement fluid to be supplied from the second reservoir 20
33
of the second supply portion 18 through the fourth pipe 21 to
the first pipe 7 and the filtration membrane 1. When the
measurement portion 8 ends measuring the measurement value H,
the control portion 11 causes the valve 22 of the fourth pipe
5 21 to close and causes the second pump 19 to stop, thereby
causing the second supply portion 18 to stop the supply of
the measurement fluid. Meanwhile, the control portion 11
causes the valve 23 of the first pipe 7 to open and drives
the first pump 6, thereby causing the ozone-containing fluid
10 to be supplied from the first reservoir 5 of the first supply
portion 3 through the first pipe 7 to the filtration membrane
1.
[0065] Next, the filtration membrane treatment method by
the filtration membrane treatment device according to
15 embodiment 3 configured as described above will be described
with reference to the flowchart in FIG. 11. First, the
control portion 11 drives the first pump 6, to perform a
supply step of supplying the ozone-containing fluid from the
first reservoir 5 of the first supply portion 3 through the
20 first pipe 7 to the filtration membrane 1 (step ST11 in FIG.
11).
[0066] Then, after the supply is performed for the first
time period T1, the control portion 11 causes the first pump
6 to stop and causes the valve 23 of the first pipe 7 to
25 close, thereby causing the supply of the ozone-containing
34
fluid to the filtration membrane 1 to stop and interrupting
the ozone treatment of the filtration membrane 1 (step ST12
in FIG. 11). Then, the control portion 11 causes the valve
22 of the fourth pipe 21 to open and drives the second pump
5 19, thereby causing the measurement fluid to be supplied from
the second reservoir 20 of the second supply portion 18
through the fourth pipe 21 to the first pipe 7 and the
filtration membrane 1. Then, the measurement step of
measuring the measurement value H based on the pressure to
10 the filtration membrane 1 is performed while the measurement
fluid continues to be supplied. The measurement portion 8
measures, as the measurement value H, a first measurement
value H1 after the ozone-containing fluid is supplied to the
filtration membrane 1 for the first time period T1, and the
15 measurement portion 8 sends the first measurement value H1 to
the control portion 11 (step ST13 in FIG. 11).
[0067] Then, the control portion 11 causes the second pump
19 to stop and causes the valve 22 of the fourth pipe 21 to
close, thereby causing the supply of the measurement fluid to
20 the filtration membrane 1 to stop. Meanwhile, the control
portion 11 drives the first pump 6, thereby causing the
ozone-containing fluid to be supplied from the first
reservoir 5 of the first supply portion 3 through the first
pipe 7 to the filtration membrane 1, whereby ozone treatment
25 of the filtration membrane 1 is restarted (step ST14 in FIG.
35
11).
[0068] Then, after the supply is performed for the second
time period T2, the control portion 11 causes the first pump
6 to stop and causes the valve 23 of the first pipe 7 to
5 close, thereby causing the supply of the ozone-containing
fluid to the filtration membrane 1 to stop and interrupting
the ozone treatment of the filtration membrane 1 (step ST15
in FIG. 11). Then, the control portion 11 causes the valve
22 of the fourth pipe 21 to open and drives the second pump
10 19, thereby causing the measurement fluid to be supplied from
the second reservoir 20 of the second supply portion 18
through the fourth pipe 21 to the first pipe 7 and the
filtration membrane 1.
[0069] Then, the measurement step of measuring the
15 measurement value H based on the pressure to the filtration
membrane 1 is performed while the measurement fluid continues
to be supplied. The measurement portion 8 measures, as the
measurement value H, a second measurement value H2 after the
ozone-containing fluid is supplied to the filtration membrane
20 1 for the second time period T2, and the measurement portion
8 sends the second measurement value H2 to the control
portion 11 (step ST16 in FIG. 11). Then, the control step of
adjusting the supply amount of the ozone-containing fluid on
the basis of the change in the measurement value H is
25 performed in the same manner as in the above-described
36
embodiment 1 (step ST17 and step ST18 in FIG. 11).
[0070] In the above-described embodiment 3, at least the
first pump 6 is stopped and the valve 23 is closed, whereby
the supply of the hydrophilization fluid to the filtration
5 membrane is stopped. In the case where, for example, ozone
gas is supplied as the hydrophilization fluid, the ozone gas
generator 12 may be stopped, or a bypass pipe or the like may
be separately provided above the first pipe 7 and flow paths
may be switched so that the supply of the ozone gas to the
10 filtration membrane 1 is temporarily interrupted.
[0071] Also in the case where the first supply portion 3
supplies the ozone-containing fluid from the primary side to
the secondary side of the filtration membrane 1 as shown in
FIG. 7 for the above-described embodiment 1, measurement with
15 the measurement fluid from the second supply portion 18 in
the above-described embodiment 3 can be performed in the same
manner. For example, as shown in FIG. 12, another filtration
membrane treatment device according to embodiment 3 is
configured by combining the configuration in FIG. 7 described
20 in the above-described embodiment 1 and the configuration in
FIG. 10 described in the present embodiment 3. That is, in
the same manner as in the above-described embodiment 3, the
control portion 11 causes the valve 22 of the fourth pipe 21
to open and drives the second pump 19, thereby causing the
25 measurement fluid to be supplied from the second reservoir 20
37
of the second supply portion 18 through the fourth pipe 21
and the first pipe 7 to the accommodating tank 2.
[0072] Then, the measurement fluid is suctioned via the
suction pump 30 from the first pipe 7 connected to the
5 filtration membrane 1, and the measurement fluid suctioned
via the suction pump 30 is discharged to outside by the first
discharge portion 10. Also with this configuration, the
filtration membrane treatment method can be performed in the
same manner as in the above-described embodiment 3. It is
10 noted that, in this case, the pressure value measured by the
pressure gauge 9 is a negative value. However, since values
with respect to pressure values are calculated with absolute
values as indicated in the above-described expressions, the
calculation can be performed in the same manner.
15 [0073] The filtration membrane treatment device according
to embodiment 3 configured as described above exhibits the
same advantageous effects as those in the above-described
embodiments, as a matter of course, and in addition, includes
a second supply portion which supplies a
20 measurement fluid which is different from the ozonecontaining
fluid to the filtration membrane, wherein
at a time of measurement by the measurement portion,
the control portion causes the first supply portion to stop,
causes the second supply portion to supply the measurement
25 fluid to the filtration membrane, and causes the measurement
38
portion to measure the measurement value. Consequently, if
the measurement value is measured with use of the measurement
fluid, no ozone treatment is performed on the filtration
membrane during the measurement since the measurement fluid
5 is different from the ozone-containing fluid. Thus, the
measurement value can be stabilized, and a more accurate
measurement value can be measured, whereby control of ozone
treatment of the filtration membrane is further improved.
[0074] In addition, the filtration membrane filters a
10 treatment-target liquid from a primary side to a secondary
side, and
the second supply portion is configured to either
pour the measurement fluid from the secondary side to the
primary side of the filtration membrane, or suction or inject
15 the measurement fluid from the primary side to the secondary
side of the filtration membrane. Consequently, ozone
treatment can be performed according to the configuration of
the filtration membrane.
[0075] Embodiment 4
20 FIG. 13 is a diagram showing a configuration of a
membrane filtration device in which a filtration membrane
treatment device is used, according to embodiment 4. In the
present embodiment 4, the filtration membrane 1 of any of the
filtration membrane treatment devices according to the above25
described embodiments is used for membrane filtration, and
39
both filtration of a treatment-target fluid by the filtration
membrane 1 and cleaning of the filtration membrane 1 can be
performed. That is, if the filtration membrane 1 is
contaminated by performing filtration such as waste water
5 treatment or water cleaning treatment on the treatment-target
liquid with use of the filtration membrane 1, the ozonecontaining
fluid is supplied to the filtration membrane 1,
whereby dirt having adhered on the filtration membrane 1 can
be separated and decomposed by the ozone-containing fluid.
10 Thus, the filtration membrane 1 is hydrophilized while the
filtration membrane 1 is cleaned.
[0076] As an example of this configuration, FIG. 13 shows
a configuration in which the filtration membrane treatment
device is incorporated in the membrane filtration device. In
15 the drawing, the same portions as those in the abovedescribed
embodiments are denoted by the same reference
characters, and description thereof is omitted. The membrane
filtration device shown in FIG. 13 is, for example, a
membrane separation bioreactor and includes: an aeration tank
20 25 as a storage tank which stores active sludge 26; and a
fifth pipe 24 through which the treatment-target fluid is
supplied to the active sludge 26 in the aeration tank 25.
The aeration tank 25 functions also as the accommodating tank
2 of the above-described filtration membrane treatment
25 devices. By the first discharge portion 10, an excess
40
portion of the active sludge 26 in the aeration tank 25 is
discharged. The first pipe 7 is connected to a sixth pipe 28,
and the sixth pipe 28 is provided with a third pump 27 as a
transfer portion. The sixth pipe 28 is provided with a valve
5 29. The third pump 27 is connected to a third discharge
portion 31.
[0077] Next, an operation of the membrane filtration
device according to embodiment 4 configured as described
above will be described. First, the treatment-target liquid
10 is supplied from the fifth pipe 24 to the aeration tank 25.
Then, the active sludge 26 stored in the aeration tank 25 and
the treatment-target liquid are mixed with each other.
Organic matter contained in the treatment-target liquid is
adsorbed and decomposed by the active sludge 26. At the same
15 time, the control portion 11 causes the valve 29 to open, and
the third pump 27 is driven. Then, the active sludge 26 is
filtered by the filtration membrane 1. A filtered-out fluid
obtained by the filtration is discharged through the first
pipe 7 and the sixth pipe 28 to the outside of the device by
20 the third discharge portion 31. At this time, the valve 23
of the first pipe 7 is in a closed state. The filtration
operation does not necessarily need to be continuously
performed but may be intermittently performed.
[0078] If dirt such as organic matter adheres on the
25 filtration membrane 1 in association with the filtration
41
operation, the trans-membrane pressure value of the
filtration membrane 1 increases. Ozone treatment of the
filtration membrane 1 is performed by stopping the filtration
operation in a case where the trans-membrane pressure value
5 reaches a predetermined value, in a case where the filtration
is performed for a predetermined time period, or at an
arbitrarily-selected timing.
[0079] The control portion 11 causes the third pump 27 to
stop and causes the valve 29 to close, thereby ending the
10 filtration operation. Then, the control portion 11 causes
the valve 23 of the first pipe 7 to open and drives the first
pump 6, thereby causing the ozone-containing fluid to be
supplied to the filtration membrane 1, whereby the filtration
membrane 1 is subjected to ozone treatment. The filtration
15 membrane treatment method can be performed in the same manner
as in the above-described embodiments, and thus description
thereof is omitted, as appropriate. If the ozone treatment
of the filtration membrane 1 is ended, the control portion 11
causes the first pump 6 to stop and causes the valve 23 of
20 the first pipe 7 to close, whereby the treatment of the
filtration membrane is ended. Then, the control portion 11
causes the valve 29 of the sixth pipe 28 to open and drives
the third pump 27, whereby filtration treatment by the
filtration membrane 1 is restarted.
25 [0080] It is noted that ozone treatment of the filtration
42
membrane 1 does not need to be performed each time of
cleaning of the filtration membrane 1, and instead, whether
ozone treatment needs to be performed may be determined and
ozone treatment may be performed each time it is determined
5 that ozone treatment needs to be performed. Alternatively,
filtration of the active sludge 26 may be started after ozone
treatment is performed in advance before the start of
filtration of the active sludge 26.
[0081] The membrane filtration device according to
10 embodiment 4 configured as described above exhibits the same
advantageous effects as those in the above-described
embodiments, as a matter of course, and in addition,
includes:
a storage tank which stores the treatment-target
15 liquid and in which the filtration membrane is immersed; and
a transfer portion which transfers, to outside of
the storage tank, the treatment-target liquid having been
filtered by the filtration membrane, wherein
the control portion causes the transfer portion to
20 stop and causes the first supply portion to supply the ozonecontaining
fluid to the filtration membrane immersed inside
the storage tank. Thus, if the filtration membrane treatment
device is incorporated in the membrane filtration device for
the treatment-target liquid and both filtration by the
25 filtration membrane and cleaning and hydrophilization of the
43
filtration membrane are performed, the cleaning of the
filtration membrane can be prevented from being excessively
or insufficiently performed.
[0082] Example 1
5 Hereinafter, Example 1 and Comparative Examples 1
and 2 will be described. Here, description will be given on
the basis of results of performing ozone treatment on the
filtration membrane 1 with use of the same device as the
filtration membrane treatment device shown in FIG. 8. The
10 main specifications of the filtration membrane treatment
device used in the present Example 1 is as shown in the table
in FIG. 14. In the present Example 1, before the start of
ozone treatment, pure water was poured from the secondary
side to the primary side of the filtration membrane 1 at
15 3(L/h), and an initial measurement value H was obtained in
advance with use of expression 4 on the basis of the flow
rate value of the pure water, a pressure value at this time,
and the effective area of the filtration membrane 1 (membrane
area). Ozone treatment was performed according to the
20 procedure of the flowchart shown in FIG. 2.
[0083] Ozone water was started to be supplied as the
ozone-containing fluid to the filtration membrane 1 at 3(L/h).
Then, a first measurement value H1 regarding the filtration
membrane 1 was measured after the elapse of 10 minutes which
25 was the first time period T1. The first measurement value H1
44
was calculated with use of expression 4. Then, a second
measurement value H2 was calculated after the elapse of the
second time period T2 which was 10 minutes from the elapse of
the first time period T1. Then, a change ratio α between the
5 first measurement value H1 and the second measurement value
H2 was calculated on the basis of expression 1 in a first
determination. Here, the threshold value α1 was set as
follows: α1=0.2. The change ratio α and the threshold value
α1 were compared with each other with use of expression 2.
10 [0084] As shown in the table in FIG. 15, the change ratio
α in the first determination was 0.4 and larger than the
threshold value α1, i.e., 0.2. Thus, the measurement value H
was measured again after the elapse of 10 minutes, and a
second determination was performed in the same manner as the
15 above-described first determination. In the second
determination, the second measurement value H2 in the first
determination was used as a first measurement value H1, and a
second measurement value H2 after the elapse of the second
time period T2, i.e., after the elapse of 30 minutes as a
20 cumulative treatment time period from the start of the ozone
treatment, was newly measured. The change ratio α at this
time was 0.38 and larger the threshold value α1, i.e., 0.2.
Thus, the measurement value H was measured again after the
elapse of 10 minutes, and a third determination was performed
25 in the same manner as the above-described determinations.
45
The change ratio α in the third determination was 0.28. Thus,
the measurement value H was measured again after the elapse
of 10 minutes, and a fourth determination was performed in
the same manner as the above-described determinations. The
5 change ratio α in the fourth determination was 0.08 and equal
to or smaller than the threshold value α1, i.e., 0.2. Thus,
the ozone treatment was ended.
[0085] Meanwhile, in Comparative Example 1 shown in FIG.
16, the filtration membrane treatment device used in Example
10 1 was used, and ozone treatment of the filtration membrane
was also performed under the same condition. In Comparative
Example 1, a measurement value was obtained only at the time
point at which 30 minutes of pouring of ozone water at 3(L/h)
as ozone treatment was ended. No measurement value was
15 measured before the time point. Meanwhile, in Comparative
Example 2 shown in FIG. 16, the filtration membrane was
subjected to ozone treatment with use of the filtration
membrane treatment device used in Example 1. In Comparative
Example 2, hydrophilization merely involved 90 minutes of
20 pouring of ozone water at 3(L/h), and no measurement value
was measured before the elapse of 90 minutes. Each
measurement value was calculated with use of expression 4 on
the basis of a pressure value, a flow rate value, and the
effective area of the filtration membrane in the same manner
25 as in the above-described Example 1.
46
[0086] The results of Example 1 are as shown in the table
in FIG. 15. The change ratio α 50 minutes after the start of
the ozone treatment was smaller than the threshold value α1,
i.e., 0.2, and the ozone treatment was completed. At this
5 time, the measurement value had increased from 11
(L/m2/h/kPa) which was an initial measurement value to 33.3
(L/m2/h/kPa). Thus, it can be confirmed that ozone treatment
was sufficiently performed and hydrophilization was promoted.
[0087] Meanwhile, the results of Comparative Examples 1
10 and 2 are as shown in the table in FIG. 16. In Comparative
Example 1, the measurement value in ozone treatment is 23
(L/m2/h/kPa). Since the measurement value in Example 1 is 33
(L/m2/h/kPa), ozone treatment was stopped while there was
room for ozone treatment, in Comparative Example 1.
15 [0088] Meanwhile, in Comparative Example 2, the
measurement value is 33.6 (L/m2/h/kPa), and ozone treatment
is considered to have been sufficient. However, this
measurement value is hardly different from the final
measurement value in Example 1 in which ozone treatment was
20 performed for 50 minutes. That is, 50 minutes is sufficient
for ozone treatment of the filtration membrane 1 used in the
present Example 1 and Comparative Example 2. Thus,
performing ozone treatment for 90 minutes as in Comparative
Example 2 is uneconomical and inefficient.
25 [0089] As described above, it has been confirmed that: the
47
present filtration membrane treatment method allows finding
of a point at which ozone treatment of the filtration
membrane is completed; and hydrophilization of the filtration
membrane can be assuredly completed by minimum necessary
5 ozone treatment. Judging from the above, the superiority of
the present example is obvious.
[0090] Although the disclosure is described above in terms
of various exemplary embodiments and implementations, it
should be understood that the various features, aspects and
10 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
instead can be applied, alone or in various combinations to
one or more of the embodiments of the disclosure.
15 It is therefore understood that numerous
modifications which have not been exemplified can be devised
without departing from the scope of the specification of the
present disclosure. For example, at least one of the
constituent parts may be modified, added, or eliminated. At
20 least one of the constituent parts mentioned in at least one
of the preferred embodiments may be selected and combined
with the constituent parts mentioned in another preferred
embodiment.
25 DESCRIPTION OF THE REFERENCE CHARACTERS
48
[0091] 1 filtration membrane
2 accommodating tank
3 first supply portion
30 suction pump
5 4 liquid
5 first reservoir
50 first reservoir
6 first pump
7 first pipe
10 8 measurement portion
9 pressure gauge
10 first discharge portion
11 control portion
12 ozone gas generator
15 13 second pipe
14 second discharge portion
15 adding portion
16 third pipe
17 flowmeter
20 170 thermometer
18 second supply portion
19 second pump
20 second reservoir
21 fourth pipe
25 22 valve
49
23 valve
24 fifth pipe
25 aeration tank
26 active sludge
5 27 third pump
28 sixth pipe
29 valve
30 suction pump
31 third discharge portion
10 H measurement value
H’ measurement value
H1 first measurement value
H2 second measurement value
T1 first time period
15 T2 second time period
50
We Claim:
[1] A filtration membrane treatment device which
performs ozone treatment on a filtration membrane, the
filtration membrane treatment device comprising:
5 a first supply portion which supplies an ozonecontaining
fluid to the filtration membrane;
a measurement portion which measures a measurement
value based on a pressure to the filtration membrane; and
a control portion which adjusts, on the basis of a
10 change in the measurement value measured by the measurement
portion, a supply amount of the ozone-containing fluid to be
supplied by the first supply portion.
[2] The filtration membrane treatment device according
15 to claim 1, wherein
the filtration membrane filters a treatment-target
liquid from a primary side to a secondary side, and
the first supply portion is configured to either
pour the ozone-containing fluid from the secondary side to
20 the primary side of the filtration membrane, or suction or
inject the ozone-containing fluid from the primary side to
the secondary side of the filtration membrane.
[3] The filtration membrane treatment device according
25 to claim 1 or 2, further comprising a second supply portion
51
which supplies a measurement fluid which is different from
the ozone-containing fluid to the filtration membrane,
wherein
at a time of measurement by the measurement portion,
5 the control portion causes the first supply portion to stop,
causes the second supply portion to supply the measurement
fluid to the filtration membrane, and causes the measurement
portion to measure the measurement value.
10 [4] The filtration membrane treatment device according
to claim 3, wherein
the filtration membrane filters a treatment-target
liquid from a primary side to a secondary side, and
the second supply portion is configured to either
15 pour the measurement fluid from the secondary side to the
primary side of the filtration membrane, or suction or inject
the measurement fluid from the primary side to the secondary
side of the filtration membrane.
20 [5] The filtration membrane treatment device according
to any one of claims 1 to 4, wherein
the measurement portion measures, as the
measurement value, each of a first measurement value H1 after
the first supply portion supplies the ozone-containing fluid
25 for a first time period and a second measurement value H2
52
after the supply is performed for a second time period which
is longer than the first time period, and
the control portion
causes the first supply portion to continue the
5 supply of the ozone-containing fluid if a change ratio α in
the following expression 1 between the first measurement
value H1 and the second measurement value H2 is larger than a
threshold value α1, and
causes the first supply portion to suppress the
10 supply of the ozone-containing fluid if the change ratio α is
equal to or smaller than the threshold value α1,
|H1-H2|÷|H1|=α ••• expression 1.
[6] The filtration membrane treatment device according
15 to claim 5, wherein the control portion causes the first
supply portion to end the supply of the ozone-containing
fluid if the change ratio α between the measurement values is
larger than the threshold value α1.
20 [7] The filtration membrane treatment device according
to any one of claims 1 to 6, wherein the first supply portion
supplies, as the ozone-containing fluid, at least one of
ozone gas, ozone water obtained by dissolving ozone, or
ozone-mixed water obtained by mixing, with ozone water, a
25 substance that promotes generation of radicals due to
53
decomposition of ozone.
[8] The filtration membrane treatment device according
to any one of claims 1 to 7, wherein
5 regarding the measurement value from the
measurement portion,
a pressure value in a pipe through which a
fluid being supplied to the filtration membrane is flowing is
measured as the measurement value,
10 a trans-membrane pressure value between inside
and outside of the filtration membrane at a time of passage
of the fluid through the filtration membrane is measured as
the measurement value, or
a ratio between the pressure value or the
15 trans-membrane pressure value and a flow rate value of the
fluid being supplied to the filtration membrane is measured
as the measurement value.
[9] The filtration membrane treatment device according
20 to any one of claims 1 to 8, wherein
the filtration membrane is formed of a material
that is hydrophilized by ozone, and
the control portion determines a degree of
hydrophilization of the filtration membrane on the basis of
25 the change in the measurement value.
54
[10] A membrane filtration device which treats a
treatment-target liquid with use of the filtration membrane
treatment device according to any one of claims 1 to 9, the
5 membrane filtration device comprising:
a storage tank which stores the treatment-target
liquid and in which the filtration membrane is immersed; and
a transfer portion which transfers, to outside of
the storage tank, the treatment-target liquid having been
10 filtered by the filtration membrane, wherein
the control portion causes the transfer portion to
stop and causes the first supply portion to supply the ozonecontaining
fluid to the filtration membrane immersed inside
the storage tank.
15
[11] A filtration membrane treatment method comprising:
a supply step of supplying an ozone-containing
fluid to a filtration membrane;
a measurement step of measuring a measurement value
20 based on a pressure to the filtration membrane; and
a control step of adjusting a supply amount of the
ozone-containing fluid on the basis of a change in the
measurement value.
25 [12] The filtration membrane treatment method according
55
to claim 11, wherein
the measurement step includes measuring each of a
first measurement value H1 after the ozone-containing fluid
is supplied for a first time period and a second measurement
5 value H2 after the supply is performed for a second time
period which is longer than the first time period, and
the control step includes:
continuing the supply of the ozone-containing
fluid if a change ratio α in the following expression 1
10 between the first measurement value H1 and the second
measurement value H2 is larger than a threshold value α1; and
suppressing the supply of the ozone-containing
fluid if the change ratio α is equal to or smaller than the
threshold value α1,
15 |H1-H2|÷|H1|=α ••• expression 1.