FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
MEMBRANE SEPARATION ACTIVATED SLUDGE SYSTEM AND MEMBRANE
CLEANING DEVICE;
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 SEPARATION ACTIVATED SLUDGE SYSTEM AND MEMBRANE
CLEANING DEVICE
5 TECHNICAL FIELD
[0001] The present invention relates to a membrane
separation activated sludge system and a membrane cleaning
device, and specifically, relates to a membrane separation
activated sludge system and a membrane cleaning device for
10 cleaning a separation membrane of a membrane separation
activated sludge device.
BACKGROUND ART
[0002] As a method for treating waste water, a membrane
15 separation activated sludge process using a membrane
separation activated sludge device, i.e., a membrane bio
reactor (MBR), is known. In the membrane separation
activated sludge process, waste water and microorganisms are
reacted with each other, whereby contaminants are removed as
20 sludge from the waste water and the resultant treated water
is acquired. In removing the contaminants, solid-liquid
separation of the contaminants and the waste water is
performed using a separation membrane of the MBR.
[0003] In the solid-liquid separation process using the
25 separation membrane, as the separation membrane continues to
3
be used, contaminants adhere to the surface of the separation
membrane or into pores of the separation membrane and thus
can cause clogging. When the clogging has occurred, solidliquid separation performance, i.e., filtration performance,
5 of the separation membrane might be gradually deteriorated.
[0004] In the membrane separation activated sludge process,
in order to suppress deterioration in filtration performance,
it is proposed that reverse flow cleaning (hereinafter,
referred to as "reverse cleaning") is performed to supply
10 cleaning water to the separation membrane in the direction
opposite to the filtration direction. For example, a method
in which contaminants adhered to the surface of the
separation membrane or contaminants adhered into pores of the
separation membrane are oxidized and separated using cleaning
15 water containing an oxidizing agent and thus are removed, is
proposed (for example, Patent Documents 1 to 3).
[0005] Patent Document 1 proposes a device for performing
reverse cleaning of a separation membrane using cleaning
water containing sodium hypochlorite. Patent Document 2
20 proposes a device for performing reverse cleaning of a
separation membrane using cleaning water containing ozone
which has greater oxidizing power than sodium hypochlorite.
Patent Document 3 proposes a device for performing reverse
cleaning of a separation membrane using cleaning water
25 containing sodium hypochlorite and then performing reverse
4
cleaning of the separation membrane using cleaning water
containing ozone.
CITATION LIST
5 PATENT DOCUMENT
[0006] Patent Document 1: Japanese Patent No. 6264095
Patent Document 2: Japanese Patent No. 6432914
Patent Document 3: Japanese Patent No. 5933854
10 SUMMARY OF THE INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION
[0007] In the conventional membrane cleaning devices as
shown in Patent Documents 1 to 3, methods of performing
reverse cleaning of the separation membrane using various
15 kinds of cleaning water are proposed for the purpose of
improving the cleaning effect. However, in the field of the
membrane cleaning device, further improvement of the cleaning
effect is required. For example, Patent Document 1 uses
cleaning water containing sodium hypochlorite which has
20 smaller oxidizing power than cleaning water containing ozone
but is inexpensive, and there is a possibility that the
cleaning is not completed within a set time. For example,
Patent Document 2 uses cleaning water containing ozone which
is more expensive than cleaning water containing sodium
25 hypochlorite but has greater oxidizing power. In this case,
5
the cleaning might be continued even after the cleaning is
completed within a set time, and thus wasteful cleaning
operation can arise. For example, in Patent Document 3, the
usage condition of cleaning water is set in advance, and
5 cleaning water containing sodium hypochlorite and cleaning
water containing ozone are used in combination. However, if
a condition different from a waste water condition assumed in
advance occurs, there is a possibility that the cleaning is
not completed or wasteful cleaning operation arises. In
10 other words, in the above conventional membrane cleaning
devices, the cleaning conditions for usage of respective
kinds of cleaning water are set in advance, and achievement
of flexible cleaning in accordance with the condition of
waste water is not considered. Therefore, further
15 improvement of the cleaning effect is required.
[0008] The present invention has been made to solve the
above problem, and an object of the present invention is to
provide a membrane separation activated sludge system and a
membrane cleaning device that enable further improvement of
20 the cleaning effect while considering achievement of flexible
cleaning operation in accordance with the condition of waste
water.
SOLUTION TO THE PROBLEMS
25 [0009] A membrane separation activated sludge system
6
according to the present invention filters out contaminants
from treatment target water containing the contaminants in a
filtration direction by a separation membrane and acquires
treated water. The membrane separation activated sludge
5 system includes a membrane cleaning device for cleaning the
separation membrane. The membrane cleaning device includes:
a first cleaning water supply unit which supplies first
cleaning water for cleaning the separation membrane, to the
separation membrane in a direction opposite to the filtration
10 direction; a second cleaning water supply unit which supplies
second cleaning water for cleaning the separation membrane,
to the separation membrane in the opposite direction, the
second cleaning water having oxidizing power different from
the first cleaning water; an accepting unit which accepts
15 selection of the first cleaning water or the second cleaning
water; and a control unit which performs control so as to,
when the selection accepted by the accepting unit indicates
the first cleaning water, drive the first cleaning water
supply unit, and when the selection accepted by the accepting
20 unit indicates the second cleaning water, drive the second
cleaning water supply unit.
[0010] A membrane cleaning device according to the present
invention cleans a separation membrane for filtering out
contaminants from treatment target water containing the
25 contaminants in a filtration direction. The membrane
7
cleaning device includes: a first cleaning water supply unit
which supplies first cleaning water for cleaning the
separation membrane, to the separation membrane in a
direction opposite to the filtration direction; a second
5 cleaning water supply unit which supplies second cleaning
water for cleaning the separation membrane, to the separation
membrane in the opposite direction, the second cleaning water
having oxidizing power different from the first cleaning
water; an accepting unit which accepts selection of the first
10 cleaning water or the second cleaning water; and a control
unit which performs control so as to, when the selection
accepted by the accepting unit indicates the first cleaning
water, drive the first cleaning water supply unit, and when
the selection accepted by the accepting unit indicates the
15 second cleaning water, drive the second cleaning water supply
unit.
EFFECT OF THE INVENTION
[0011] According to one aspect of the present invention,
20 it is possible to provide a membrane separation activated
sludge system and a membrane cleaning device that enable
further improvement of the cleaning effect while considering
achievement of flexible cleaning in accordance with the
condition of waste water.
25
8
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] [FIG. 1] FIG. 1 is a configuration diagram of a
membrane separation activated sludge system including a
membrane separation activated sludge device and a membrane
5 cleaning device according to embodiment 1.
[FIG. 2] FIG. 2 illustrates the configuration of
an accepting unit according to embodiment 2.
DESCRIPTION OF EMBODIMENTS
10 [0013] Hereinafter, with reference to the accompanying
drawings, embodiments of a membrane separation activated
sludge system and a membrane cleaning device according to the
present disclosure will be described in detail. The
embodiments described below are merely examples and the
15 present invention is not limited by these embodiments.
[0014] Embodiment 1
FIG. 1 is a configuration diagram of a membrane
separation activated sludge system including a membrane
separation activated sludge device 20 and a membrane cleaning
20 device 40 according to embodiment 1.
[0015] As shown in FIG. 1, the membrane separation
activated sludge system according to embodiment 1 includes
the membrane separation activated sludge device 20 having a
membrane separation tank 1 and a separation membrane 2, an
25 inflow pipe 5, a filtered water pipe 3a, the membrane
9
cleaning device 40, and a filtration pump 4.
[0016] The inflow pipe 5 is a pipe member for waste water
to flow as inflow water into the membrane separation tank 1.
The filtered water pipe 3a is a pipe member through which
5 inflow water filtered by the separation membrane 2 after
flowing into the membrane separation tank 1 is discharged as
filtered water from the membrane separation tank 1. The
filtration pump 4 is a pump member for promoting discharge of
the filtered water through the filtered water pipe 3a by
10 means of pressure.
[0017] The membrane separation tank 1 is a storage member
for storing the inflow water that has flowed in through the
inflow pipe 5 as treatment target water 6. The membrane
separation tank 1 stores the treatment target water 6 so as
15 not to leak the water, and therefore is formed using concrete.
In the treatment target water 6 stored in the membrane
separation tank 1, microorganisms (hereinafter, referred to
as activated sludge) for capturing contaminants contained in
the treatment target water 6 are present. Therefore, the
20 contaminants in the treatment target water 6 are captured in
the activated sludge.
[0018] The separation membrane 2 is a membrane member for
separating the activated sludge that has captured the
contaminants from the treatment target water 6, and resultant
25 water from which the contaminants have been captured and
10
removed. The separation membrane 2 is provided so as to be
immersed in the stored treatment target water 6 in the
membrane separation tank 1. The filtered water separated and
filtered by the separation membrane 2 is led to the filtered
5 water pipe 3a by the filtration pump 4.
[0019] The separation membrane 2 may be any member that
can separate solid and liquid in the treatment target water 6
containing the activated sludge, and a hollow fiber membrane,
a flat membrane, or the like may be applied. The separation
10 membrane 2 may be any member that can separate solid and
liquid in the treatment target water 6 containing the
activated sludge, and an ultrafiltration (UF) membrane, a
microfiltration (MF) membrane, or the like may be applied.
[0020] While the separation membrane 2 continues to
15 separate solid and liquid in the treatment target water 6
containing the activated sludge, in other words, while a
filtration process for leading the treatment target water 6
from the outside of the separation membrane 2 to the filtered
water pipe 3a is continued, there is a possibility that the
20 activated sludge and contaminants in the treatment target
water 6 adhere to the surface of the separation membrane 2 or
into pores of the separation membrane 2, thus causing
clogging. When the clogging has occurred, the filtration
rate is reduced and thus efficiency of water treatment using
25 the membrane separation activated sludge system might be
11
lowered.
[0021] The membrane cleaning device 40 is a cleaning
device for cleaning the separation membrane 2, and includes a
first cleaning water supply unit 8, a second cleaning water
5 supply unit 9, a control unit 10, and an accepting unit 11.
The membrane cleaning device 40 performs reverse cleaning to
supply cleaning water in a direction from the filtered water
pipe 3a to the outside of the separation membrane 2, which is
a direction opposite to the filtration direction. Through
10 the reverse cleaning, the membrane cleaning device 40 cleans
the separation membrane 2, thus contributing to improvement
in the water treatment efficiency.
[0022] The first cleaning water supply unit 8 is connected
to the filtered water pipe 3a via a first cleaning water
15 supply pipe 3b, and supplies first cleaning water to the
separation membrane 2 at a predetermined cleaning water flow
rate. The second cleaning water supply unit 9 is connected
to the filtered water pipe 3a via a second cleaning water
supply pipe 3c, and supplies second cleaning water having
20 oxidizing power different from the first cleaning water, to
the separation membrane 2, at a predetermined cleaning water
flow rate.
[0023] The control unit 10 controls operations of the
first cleaning water supply unit 8 and the second cleaning
25 water supply unit 9. The control unit 10 is connected to the
12
first cleaning water supply unit 8 via a signal line 50a, and
connected to the second cleaning water supply unit 9 via a
signal line 50b. When having accepted a selection
instruction for the cleaning water from the accepting unit 11
5 described later, the control unit 10 transmits a signal
corresponding to the accepted selection instruction to the
first cleaning water supply unit 8 and the second cleaning
water supply unit 9, to control operation of the first
cleaning water supply unit 8 and operation of the second
10 cleaning water supply unit 9, thereby selecting the cleaning
water.
[0024] The accepting unit 11 is an accepting unit that
accepts an instruction for reverse cleaning with first
cleaning water using the first cleaning water supply unit 8
15 and reverse cleaning with second cleaning water using the
second cleaning water supply unit 9, from the outside. The
accepting unit 11 is connected to the control unit 10 via a
signal line 50c. An example of the accepting unit 11 in
embodiment 1 is a selection switch. When an operator for the
20 membrane separation activated sludge system inputs a
selection instruction using the accepting unit 11, the
selection instruction accepted by the accepting unit 11 is
transmitted to the control unit 10 via the signal line 50c.
[0025] The first cleaning water supply unit 8 in
25 embodiment 1 supplies cleaning water containing sodium
13
hypochlorite, as an example of the first cleaning water, to
the separation membrane 2. The concentration of sodium
hypochlorite is not particularly limited, and is preferably
not less than 0.05 mg/L and not greater than 10000 mg/L, and
5 more preferably not less than 0.5 mg/L and not greater than
8000 mg/L. If the concentration of sodium hypochlorite is
lower than the above range, it is difficult to oxidize and
decompose the activated sludge and contaminants adhered to
the separation membrane 2 and there is a possibility that the
10 activated sludge and contaminants cannot be removed
efficiently. If the concentration of sodium hypochlorite is
higher than the above range, the consumption amount of the
oxidizing agent increases, which can lead to increase in
treatment cost.
15 [0026] The second cleaning water supply unit 9 in
embodiment 1 supplies cleaning water containing ozone, as an
example of the second cleaning water, to the separation
membrane 2. The second cleaning water containing ozone has
greater oxidizing power than the first cleaning water
20 containing sodium hypochlorite. The concentration of
dissolved ozone in the second cleaning water is not
particularly limited, and is preferably not less than 0.01
mg/L and not greater than 200 mg/L, and more preferably not
less than 0.1 mg/L and not greater than 100 mg/L. If the
25 concentration of dissolved ozone is lower than the above
14
range, it is difficult to oxidize and decompose the activated
sludge and contaminants adhered to the separation membrane 2
and there is a possibility that the activated sludge and
contaminants cannot be removed efficiently. If the
5 concentration of dissolved ozone is higher than the above
range, the consumption amount of the oxidizing agent
increases, which can lead to increase in treatment cost.
[0027] One example of substances that can cause clogging
in the separation membrane 2 is considered to be contaminants
10 adhered to the surface of the separation membrane or into
pores thereof. In general, contaminants are soluble organic
substances. Therefore, the contaminants can be removed
through oxidation and decomposition using an oxidizing agent.
However, as soluble organic substances, it is known that two
15 kinds of organic substances, i.e., easily decomposable
organic substances which are comparatively easy to oxidize
and decompose, and hardly decomposable organic substances
which are comparatively hard to oxidize and decompose, are
contained. Therefore, in the membrane separation activated
20 sludge system according to embodiment 1, focusing on presence
of the easily decomposable organic substances and the hardly
decomposable organic substances, the first cleaning water and
the second cleaning water different in oxidizing power are
prepared. Examples of the easily decomposable organic
25 substances which are comparatively easy to oxidize and
15
decompose include amino acids and low molecular weight
compounds, and examples of the hardly decomposable organic
substances which are comparatively hard to oxidize and
decompose include polymer compounds such as proteins,
5 polysaccharides, and oil and fat, and organic acids.
[0028] In a case of performing reverse cleaning of the
separation membrane 2 using the cleaning water containing
sodium hypochlorite as the first cleaning water, it is easy
to oxidize and decompose the easily decomposable organic
10 substances and remove them, but it is difficult to oxidize
and decompose the hardly decomposable organic substances and
remove them. On the other hand, in a case of performing
reverse cleaning of the separation membrane 2 using the
cleaning water containing ozone water as the second cleaning
15 water, it is easy to oxidize and decompose the easily
decomposable organic substances and the hardly decomposable
organic substances and remove them, but the cleaning cost
might become higher than in the case of using the first
cleaning water. This is because an ozone gas generating
20 process which needs power supply is required. In the
membrane separation activated sludge system according to
embodiment 1, the cleaning water containing sodium
hypochlorite and the cleaning water containing ozone water
are selected and controlled by the control unit 10 described
25 later, thus achieving flexible cleaning in accordance with
16
the condition of waste water and enabling further improvement
of the cleaning effect.
[0029] When having accepted a selection instruction from
the accepting unit 11, the control unit 10 selects the
5 cleaning water between the first cleaning water and the
second cleaning water different in oxidizing power, on the
basis of the accepted selection instruction. Thus, the
membrane cleaning device 40 in embodiment 1 selects the
second cleaning water containing ozone in a condition where
10 clogging of the separation membrane 2 is likely to occur
because, for example, the waste water contains a large amount
of contaminants, and selects the first cleaning water
containing sodium hypochlorite in a condition where clogging
of the separation membrane 2 is unlikely to occur because,
15 for example, the waste water contains a less amount of
contaminants. In this way, flexible reverse cleaning in
accordance with the condition of the waste water can be
achieved, thus enabling further improvement of the cleaning
effect.
20 [0030] In a case where, after the first cleaning water has
been selected and is being supplied, the condition of the
waste water is changed so that clogging of the separation
membrane 2 is likely to occur, by accepting a selection
instruction for the second cleaning water from the accepting
25 unit 11, the control unit 10 can stop the reverse cleaning
17
using the first cleaning water and perform reverse cleaning
using the second cleaning water having greater oxidizing
power. In a case where, after the second cleaning water has
been selected and is being supplied, the condition of the
5 waste water is changed so that clogging of the separation
membrane 2 is unlikely to occur, by accepting a selection
instruction for the first cleaning water from the accepting
unit 11, the control unit 10 can stop the reverse cleaning
using the second cleaning water and perform reverse cleaning
10 using the first cleaning water having smaller oxidizing power.
Accordingly, flexible reverse cleaning in accordance with the
condition of the waste water can be achieved, thus enabling
further improvement of the cleaning effect.
[0031] The second cleaning water containing ozone has
15 greater oxidizing power than the first cleaning water
containing sodium hypochlorite, and also has a higher
reaction rate in reaction with the contaminants adhered to
the separation membrane. Therefore, the ozone consumption
rate in the cleaning water is higher than the sodium
20 hypochlorite consumption rate. Accordingly, regarding a
cleaning flux which is a cleaning water flow rate per
membrane area of the separation membrane 2, the control unit
10 performs control so that the cleaning flux of the second
cleaning water containing ozone becomes greater than the
25 cleaning flux of the first cleaning water containing sodium
18
hypochlorite. From the above reason, the membrane separation
activated sludge system according to embodiment 1 can achieve
flexible reverse cleaning in accordance with the condition of
the waste water, thus enabling further improvement of the
5 cleaning effect.
[0032] In a case where, after the first cleaning water has
been selected and is being supplied, the condition of the
waste water is changed so that clogging of the separation
membrane 2 is likely to occur, by accepting a selection
10 instruction for the second cleaning water from the accepting
unit 11, the control unit 10 sets the cleaning flow rate of
the second cleaning water supply unit 9 to be greater than
the cleaning flow rate of the first cleaning water supply
unit 8 during the reverse cleaning using the first cleaning
15 water, so as to increase the cleaning flux thereof. Thus,
reverse cleaning using the second cleaning water having
greater oxidizing power is performed. In a case where, after
the second cleaning water has been selected and is being
supplied, the condition of the waste water is changed so that
20 clogging of the separation membrane 2 is unlikely to occur,
by accepting a selection instruction for the first cleaning
water from the accepting unit 11, the control unit 10 sets
the cleaning flow rate of the first cleaning water supply
unit 8 to be smaller than the cleaning flow rate of the
25 second cleaning water supply unit 9 during the reverse
19
cleaning using the second cleaning water, so as to decrease
the cleaning flux thereof. Thus, reverse cleaning using the
second cleaning water having smaller oxidizing power is
performed. In this way, the membrane separation activated
5 sludge system according to embodiment 1 can achieve more
flexible reverse cleaning in accordance with the condition of
the waste water while also considering the reaction rate
between the contaminants and the cleaning water, thus
enabling further improvement of the cleaning effect.
10 [0033] The membrane separation activated sludge system
according to embodiment 1 filters the treatment target water
6 using the separation membrane 2, thereby acquiring treated
water 7. In a case where, while the separation membrane 2
continues to be used, activated sludge or contaminants adhere
15 to the surface of the separation membrane 2 or into pores
thereof and thus clogging has occurred, the filtration
performance of the separation membrane 2 might be
deteriorated. In order to suppress deterioration of the
filtration performance of the separation membrane 2, the
20 membrane separation activated sludge system according to
embodiment 1 interrupts a filtration process of filtering the
treatment target water 6 using the separation membrane 2, and
performs a reverse cleaning process of reversely cleaning the
separation membrane 2 using the cleaning water. When the
25 reverse cleaning process is finished, the membrane separation
20
activated sludge system according to embodiment 1 restarts
the filtration process of filtering the treatment target
water 6 using the separation membrane 2. By repeatedly
performing the filtration process and the reverse cleaning
5 process as described above, the membrane separation activated
sludge system according to embodiment 1 can improve the water
treatment efficiency as compared to a membrane separation
activated sludge system of such a type that performs cleaning
by immersing the separation membrane 2 in cleaning water.
10 This is because it is unnecessary to perform work for taking
out the separation membrane 2 from the membrane separation
tank 1 and work for placing the taken separation membrane 2
into the membrane separation tank 1 again, which would be
necessary in the case of immersion.
15 [0034] The amount of easily decomposable organic
substances and the amount of hardly decomposable organic
substances in the contaminants depend on the water quality of
the inflow water (treatment target water) 6 flowing into the
membrane separation tank 1 and the operation condition of the
20 membrane separation activated sludge device 20. In addition,
the ratio of easily decomposable organic substances and
hardly decomposable organic substances in the contaminants
also depends on the water quality of the inflow water
(treatment target water) 6 flowing into the membrane
25 separation tank 1 and the operation condition of the membrane
21
separation activated sludge device 20. The water quality of
the inflow water (treatment target water) 6 changes from
moment to moment, and the operation condition of the membrane
separation activated sludge device 20 also changes in
5 accordance with change in the water quality. Therefore, the
amount of easily decomposable organic substances and the
amount of hardly decomposable organic substances in the
contaminants, and the ratio of the easily decomposable
organic substances and the hardly decomposable organic
10 substances, can easily change.
[0035] In the membrane separation activated sludge system
according to embodiment 1, the control unit 10 selects the
cleaning water in accordance with a selection instruction
accepted by the accepting unit 11. Thus, in accordance with
15 change in the water quality and change in the operation
condition, cleaning by the first cleaning water containing
sodium hypochlorite which is comparatively low in cost can be
selected when easily decomposable organic substances are a
main factor for clogging, and cleaning by the second cleaning
20 water containing ozone which is comparatively high in cost
but has greater oxidizing power can be selected when hardly
decomposable organic substances are a main factor for
clogging. Therefore, in the membrane separation activated
sludge system according to embodiment 1, the usage amount of
25 the oxidizing agent and the usage amount of the cleaning
22
water are reduced and flexible cleaning in accordance with
the condition of waste water can be achieved.
[0036] The control unit 10 may, for example, perform
reverse cleaning by driving the second cleaning water supply
5 unit 9, after reverse cleaning by driving the first cleaning
water supply unit 8 is finished. The control unit 10 may,
for example, perform reverse cleaning by driving the first
cleaning water supply unit 8, after reverse cleaning by
driving the second cleaning water supply unit 9 is finished.
10 The control unit 10 may, for example, perform reverse
cleaning by driving both the first cleaning water supply unit
8 and the second cleaning water supply unit 9. The control
unit 10 may, for example, perform the reverse cleaning by
driving the first cleaning water supply unit 8 and reverse
15 cleaning by driving the second cleaning water supply unit 9
alternately a plurality of times.
[0037] As described above, the membrane separation
activated sludge system according to embodiment 1 filters out
contaminants from the treatment target water 6 containing the
20 contaminants in the filtration direction by the separation
membrane 2 and acquires the treated water 7. The membrane
separation activated sludge system includes the membrane
cleaning device 40 for cleaning the separation membrane 2.
The membrane cleaning device 40 includes the first cleaning
25 water supply unit 8, the second cleaning water supply unit 9,
23
the accepting unit 11, and the control unit 10. The first
cleaning water supply unit 8 is a device for supplying, to
the separation membrane 2, the first cleaning water
containing the sodium hypochlorite, as an example of the
5 first cleaning water for cleaning the separation membrane 2,
and supplies the first cleaning water to the separation
membrane 2 in the direction opposite to the filtration
direction. The second cleaning water supply unit 9 is a
device for supplying, to the separation membrane 2, the
10 second cleaning water containing ozone, as an example of the
second cleaning water for cleaning the separation membrane 2,
and supplies the second cleaning water which has oxidizing
power different from the first cleaning water, to the
separation membrane 2 in the direction opposite to the
15 filtration direction. The accepting unit 11 is a device for
accepting selection of the first cleaning water or the second
cleaning water. When the accepting unit 11 has accepted
selection of the first cleaning water, the control unit 10
performs control to drive the first cleaning water supply
20 unit 8 and perform reverse cleaning of the separation
membrane 2 by the first cleaning water. When the accepting
unit 11 has accepted selection of the second cleaning water,
the control unit 10 performs control to drive the second
cleaning water supply unit 9 and perform reverse cleaning of
25 the separation membrane 2 by the second cleaning water. Thus,
24
the membrane separation activated sludge system according to
embodiment 1 can achieve flexible cleaning in accordance with
the condition of waste water which is the treatment target
water 6, thereby enabling improvement of the cleaning effect.
5 [0038] As described above, in the membrane separation
activated sludge system according to embodiment 1, in a case
where contaminants of the treatment target water 6 include
easily decomposable organic substances which are
comparatively easy to decompose and hardly decomposable
10 organic substances which are comparatively hard to decompose,
the first cleaning water having higher oxidizing-decomposing
characteristics for the easily decomposable organic
substances than for the hardly decomposable organic
substances, and the second cleaning water having higher
15 oxidizing-decomposing characteristics for the hardly
decomposable organic substances than the first cleaning water,
are prepared. Thus, the membrane separation activated sludge
system according to embodiment 1 can achieve more flexible
cleaning in accordance with the condition of waste water
20 which is the treatment target water 6, thereby enabling
improvement of the cleaning effect.
[0039] As described above, the control unit 10 included in
the membrane separation activated sludge system according to
embodiment 1 performs control so that the cleaning flux with
25 which the second cleaning water supply unit supplies the
25
second cleaning water to the separation membrane becomes
higher than the cleaning flux with which the first cleaning
water supply unit supplies the first cleaning water to the
separation membrane. Thus, the membrane separation activated
5 sludge system according to embodiment 1 can achieve even more
flexible cleaning in accordance with the condition of waste
water which is the treatment target water 6, thereby enabling
further improvement of the cleaning effect.
[0040] In the above embodiment 1, the case where the
10 membrane separation tank 1 is formed using concrete has been
described. However, the present invention is not limited
thereto. The membrane separation tank 1 may be formed using
a material such as stainless steel or resin in order to store
the treatment target water 6 so as not to leak the water.
15 [0041] In the above embodiment 1, the configuration of
selecting between reverse cleaning using the first cleaning
water and reverse cleaning using the second cleaning water
has been described. However, the present invention is not
limited thereto. In accordance with the selection
20 instruction accepted from the accepting unit 11, the control
unit 10 may perform control of the cleaning flux so that the
cleaning flow rate of the first cleaning water supply unit 8
becomes smaller than the cleaning flow rate of the second
cleaning water supply unit 9, to perform reverse cleaning by
25 supplying the first cleaning water and the second cleaning
26
water at the same time. This configuration can achieve more
flexible cleaning in accordance with the condition of the
waste water, thereby enabling further improvement of the
cleaning effect.
5 [0042] Embodiment 2
In embodiment 1, the membrane separation activated
sludge system configured such that the accepting unit 11
accepts a selection instruction from the outside, has been
described. In embodiment 2, the membrane separation
10 activated sludge system configured such that the accepting
unit 11 accepts a selection instruction from the inside will
be described below. The same components as those in
embodiment 1 will not be described.
[0043] FIG. 2 illustrates the configuration of the
15 accepting unit 11 according to embodiment 2. The accepting
unit 11 according to embodiment 2 includes a membrane
detection part 12, a storage part 13, and a determination
part 14.
[0044] The membrane detection part 12 is a device for
20 continuously or intermittently detecting the condition of
clogging of the separation membrane 2, and is connected to
the determination part 14 described later via a signal line
50d. The separation membrane 2 is provided with a sensor
(not shown) for detecting the condition of clogging of the
25 separation membrane 2. The membrane detection part 12
27
acquires a detection result from the sensor, and transmits
information about the acquired detection result to the
determination part 14 via the signal line 50d. The membrane
detection part 12 is, for example, a processor.
5 [0045] The storage part 13 is a device storing, in advance,
reverse cleaning methods corresponding to conditions of
clogging of the separation membrane 2, and is connected to
the determination part 14 described later via a signal line
50e. The storage part 13 stores, for example, a table
10 representing the correspondence relationship between a
plurality of detection values of the membrane detection part
12 and a plurality of driving control conditions of the first
cleaning water supply unit 8 and the second cleaning water
supply unit 9. The storage part 13 is, for example, a memory.
15 [0046] The determination part 14 is a device for
determining and accepting a reverse cleaning method
corresponding to the clogging condition of the separation
membrane 2. In other words, the determination part 14 is a
device for generating and accepting a selection instruction
20 for cleaning water on the basis of the determined reverse
cleaning method. The determination part 14 is connected to
the control unit 10 via a signal line 50f. The determination
part 14 accepts a selection instruction on the basis of the
detection result from the membrane detection part 12 and the
25 stored content in the storage part 13, and transmits the
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accepted selection instruction to the control unit 10. The
determination part 14 is, for example, a processor.
[0047] In the membrane separation activated sludge system
according to embodiment 2, the accepting unit 11 accepts a
5 selection instruction based on a detection result from the
membrane detection part 12, and the control unit 10 performs
selection of cleaning water in accordance with the selection
instruction accepted by the accepting unit 11. Thus, in
accordance with change in the water quality and change in the
10 operation condition, cleaning by the first cleaning water
containing sodium hypochlorite which is comparatively low in
cost can be automatically selected when easily decomposable
organic substances are a main factor for clogging, and
cleaning by the second cleaning water containing ozone which
15 is comparatively high in cost but has greater oxidizing power
can be automatically selected when hardly decomposable
organic substances are a main factor for clogging. Therefore,
the usage amount of the oxidizing agent and the usage amount
of the cleaning water are reduced and flexible cleaning in
20 accordance with the condition of waste water can be achieved.
[0048] The present invention is not limited to the
specific details and representative embodiments explained and
described above. Other modifications and effects that could
be easily derived by a person skilled in the art are also
25 included in the present invention. Therefore, various
29
alterations can be made without deviating from the ideas or
scope of the generic concept of the invention defined by the
accompanying claims and equivalents thereof.
5 DESCRIPTION OF THE REFERENCE CHARACTERS
[0049] 1 membrane separation tank
2 separation membrane
4 filtration pump
5 inflow pipe
10 8 first cleaning water supply unit
9 second cleaning water supply unit
10 control unit
11 accepting unit
20 membrane separation activated sludge device
15 40 membrane cleaning device
30
We Claim :
[1] A membrane separation activated sludge system which
filters out contaminants from treatment target water
containing the contaminants in a filtration direction by a
5 separation membrane and acquires treated water, the membrane
separation activated sludge system comprising a membrane
cleaning device for cleaning the separation membrane, wherein
the membrane cleaning device includes
a first cleaning water supply unit which
10 supplies first cleaning water for cleaning the separation
membrane, to the separation membrane in a direction opposite
to the filtration direction,
a second cleaning water supply unit which
supplies second cleaning water for cleaning the separation
15 membrane, to the separation membrane in the opposite
direction, the second cleaning water having oxidizing power
different from the first cleaning water,
an accepting unit which accepts selection of
the first cleaning water or the second cleaning water, and
20 a control unit which performs control so as to,
when the selection accepted by the accepting unit indicates
the first cleaning water, drive the first cleaning water
supply unit, and when the selection accepted by the accepting
unit indicates the second cleaning water, drive the second
25 cleaning water supply unit.
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[2] The membrane separation activated sludge system
according to claim 1, wherein
the first cleaning water is cleaning water
5 containing sodium hypochlorite, and
the second cleaning water is cleaning water
containing ozone.
[3] The membrane separation activated sludge system
10 according to claim 1 or 2, wherein
the contaminants include easily decomposable
organic substances and hardly decomposable organic substances,
the first cleaning water has higher oxidizingdecomposing characteristics for the easily decomposable
15 organic substances than for the hardly decomposable organic
substances, and
the second cleaning water has higher oxidizingdecomposing characteristics for the hardly decomposable
organic substances than the first cleaning water.
20
[4] The membrane separation activated sludge system
according to any one of claims 1 to 3, wherein
the control unit performs control so that a
cleaning flux with which the second cleaning water supply
25 unit supplies the second cleaning water to the separation
32
membrane becomes higher than a cleaning flux with which the
first cleaning water supply unit supplies the first cleaning
water to the separation membrane.
5 [5] A membrane cleaning device which cleans a
separation membrane for filtering out contaminants from
treatment target water containing the contaminants in a
filtration direction, the membrane cleaning device
comprising:
10 a first cleaning water supply unit which supplies
first cleaning water for cleaning the separation membrane, to
the separation membrane in a direction opposite to the
filtration direction;
a second cleaning water supply unit which supplies
15 second cleaning water for cleaning the separation membrane,
to the separation membrane in the opposite direction, the
second cleaning water having oxidizing power different from
the first cleaning water;
an accepting unit which accepts selection of the
20 first cleaning water or the second cleaning water; and
a control unit which performs control so as to,
when the selection accepted by the accepting unit indicates
the first cleaning water, drive the first cleaning water
supply unit, and when the selection accepted by the accepting
25 unit indicates the second cleaning water, drive the second
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cleaning water supply unit.
[6] The membrane cleaning device according to claim 5,
wherein
5 the first cleaning water is cleaning water
containing sodium hypochlorite, and
the second cleaning water is cleaning water
containing ozone.
10 [7] The membrane cleaning device according to claim 5
or 6, wherein
the contaminants include easily decomposable
organic substances and hardly decomposable organic substances,
the first cleaning water has higher oxidizing15 decomposing characteristics for the easily decomposable
organic substances than for the hardly decomposable organic
substances, and
the second cleaning water has higher oxidizingdecomposing characteristics for the hardly decomposable
20 organic substances than the first cleaning water.
[8] The membrane cleaning device according to any one
of claims 5 to 7, wherein
the control unit performs control so that a
25 cleaning flux with which the second cleaning water supply
34
unit supplies the second cleaning water to the separation
membrane becomes higher than a cleaning flux with which the
first cleaning water supply unit supplies the first cleaning
water to the separation membrane.