- 1 -
Description
LARGE SCALE MEMBRANE SEPARATING INSTALLATION
Technical Field
[0001]
The present invention relates to a large scale
membrane separating installation, and to a technique of,
when cleaning a membrane unit with a chemical liquid,
efficiently uniformly distributing and contacting the
chemical liquid to and with the membrane unit.
Background Art
[0002]
In conventional submerged membrane separating
installations located in a reaction vessel, a membrane
unit constituting a basic unit has a plurality of
membrane cartridges installed in one casing. As known
from Japanese Patent Laid-Open No. 9-52026, in small
scale facilities using a small number of membrane
cartridges, during cleaning with a chemical liquid, the
cleaning chemical liquid is supplied to each of the
membrane cartridges by gravity injection.
[0003]
However, in large scale facilities, a plurality of
membrane units are arranged in a line or in a plurality
of lines depending on the increased volume of the
reaction vessel. In this case, when the cleaning chemical
liquid is supplied to each membrane cartridge by gravity
injection, the time required for the supply operation
increases to reduce the operation time of the facility
and thus the throughput of the facility.
[0004]

- 2 -
Thus, the inventors have contrived a method of
supplying a predetermined amount of cleaning chemical
liquid in a short time using a pump as shown in FIG. 19.
[0005]
In FIG. 19, in the reaction vessel, a plurality of
membrane units 1 are arranged in a line. In each of the
membrane units 1, a plurality of membrane cartridges (not
shown) are arranged parallel to one another. Each of the
membrane cartridges has filtration membranes like flat
membranes located on respective surfaces of a filter
plate so as to form a permeated liquid channel between
the filter plate and each of the filtration membranes.
The permeated liquid channel is in communication with a
collecting header via a tube.
[0006]
A header 2 is located along a direction in which the
membrane units 1 are arranged. The header 2 forms a
channel with a diameter (large diameter) required to
ensure a smooth flow. Branch pipes 3 branch from the
header 2 and connect to collecting headers of the
respective membrane units 1 via valves 4. Each of the
branch pipes 3 forms a channel having a smaller diameter
than the header 2. Each of the collecting headers is
provided for a casing of the corresponding membrane unit
1.
[0007]
The header 2 is located at a position of a
predetermined height h1 from a liquid level in the
reaction vessel. Furthermore, the header 2 has a pressure
release valve 5 located beside a terminal thereof in a
flow direction at a position of a predetermined height h2
from the header 2.
[0008]
The header 2 is in communication with a filtrate
recovery pipeline 6 at a start point thereof (inlet) in


- 3 -
the flow direction. The filtrate recovery pipeline 6 is
in communication with a treated water tank 7 and has a
first selector valve 8 and a plurality of treated water
pumps 9 interposed in the middle thereof. Furthermore,
cleaning liquid supply pipeline 11 is connected to the
filtrate recovery pipeline 6 via a second selector valve
10 .
[0009]
The cleaning liquid supply pipeline 11 is connected
to a submerged pump 12 provided in the treated water tank
7 and has an agitator 13 interposed in the middle thereof.
A cleaning chemical liquid supply pipeline 14 is
connected between the submerged pump 12 and the agitator
13. The cleaning chemical liquid supply pipeline 14 is in
communication with a chemical tank 15 and has a transfer
pump 16 interposed in the middle thereof.
[0010]
The effects of this configuration are described below.
During a filtration operation, the valve 4 and the first
selector valve 8 are open. The pressure release valve 5
and the second selector valve 10 are closed. In this
condition, the treated water pump 9 is driven to exert a
suction pressure on the membrane cartridges in each of
the membrane units 1. The suction pressure is used as a
driving pressure to subject a liquid in the reaction
vessel to a membrane separation treatment using the
membrane cartridges.
[0011]
A filtrate having permeated the filtration membrane
in each membrane cartridge flows through the tube (not
shown) into the collecting header (not shown). The
filtrate further flows through the branch pipe 3 to the
header 2 and then through the filtrate recovery pipeline
6 into the treated water tank 7.
[0012]

- 4 -
During a backwashing operation, the valve 4, the
pressure release valve 5, and the second selector valve
10 are open. The first selector valve 8 is closed. In
this condition, the submerged pump 12 is driven to supply
treated water in the treated water tank 7 to the header 2.
The transfer pump 16 is driven to supply a cleaning
chemical liquid to the header 2 together with the treated
water.
[0013]
The cleaning chemical liquid is mixed into the
treated water in the agitator 13, where the concentration
of the cleaning chemical liquid is adjusted to a
predetermined value. The cleaning chemical liquid then
flows through the cleaning liquid supply pipeline 11 into
the header 2. The concentration is adjusted by
controlling the submerged pump 12 and the transfer pump
16. The cleaning chemical liquid having flown into the
header 2 flows from the header 2 through the branch pipes
3 to the collecting headers of the respective membrane
units 1. The cleaning chemical liquid then flows into the
respective membrane cartridges via the tubes.
Disclosure of the Invention
[0014]
In the above-described operation, when the cleaning
chemical liquid is injected into the plurality of
membrane units 1, an appropriate amount of cleaning
chemical liquid needs to be injected into each of the
membrane units 1. However, the cleaning chemical liquid
is not always uniformly injected into the respective
membrane units 1.
[0015]
When the cleaning chemical liquid is injected into
the header 2, the pressure inside the header 2 increases.
If the pressure increases excessively and the facility

- 5 -
has no equipment such as a valve which can reduce the
increased pressure, the filtration membranes in the
membrane cartridges may be broken by the pressure acting
on the membrane cartridges through the branch pipe 3, the
collecting header, and the tube or by the inflow of a
large amount of cleaning chemical liquid resulting from
the pressure. Furthermore, the pressure inside the header
2 is also a cause of the nonuniform injection of the
cleaning chemical liquid.
[0016]
It is possible to provide a structure that
uniformizes the amount of cleaning chemical liquid
flowing through the branch pipes 3 by using pressure
reducing valves (flow regulating valves) provided in the
branch pipes 3 to cause a pressure loss while increasing
the pressure in the header 2. However, in this case, the
resultant flow rate of the chemical liquid may often be
lower than the required value. Purging a gas flowing back
from membrane units is also impossible.
[0017]
Furthermore, when the membrane units are connected to
the branch pipes 3, the injected chemical liquid
remaining in the membrane units may nonuniformly flow out
and leak from membrane surfaces in the membrane units due
to an uneven pressure in the branch pipe. This may also
prevent the chemical liquid remaining in the membrane
units from being kept uniform.
[0018]
Additionally, when the chemical liquid is supplied by
gravity, a pump, or the like in the above-described
configuration, a water head is limited and needs to be at
most 100 kPa. In particular, if each of the membrane
cartridges comprises a filtration membrane like a flat
membrane, the water head needs to be at most 40 kPa
(preferably at most 20 kPa).

- 6 -
[0019]
The present invention solves these problems. An
object of the present invention is to provide a large
scale membrane separating installation that can
simultaneously and uniformly distribute and contact the
cleaning chemical liquid to and with the membrane
cartridges in the plurality of membrane units.
[0020]
To accomplish this object, the present invention
provides a large scale membrane separating installation
including a plurality of membrane units arranged in a
reaction vessel and a plurality of branch pipes branching
from a header and connected to collecting headers of the
respective membrane units so that a cleaning chemical
liquid flows through the header and the branch pipes to
the respective membrane units, wherein a cleaning
chemical liquid distribution unit includes the header and
the branch pipes each having a smaller diameter than the
header, and the cleaning chemical liquid distribution
unit includes a pipeline configuration uniformly
distributing the cleaning chemical liquid to be supplied
to the membrane units.
[0021]
In this configuration, during a cleaning operation
with the chemical liquid, a predetermined flow rate of
cleaning chemical liquid flows through the header. The
cleaning chemical liquid flows through the header and the
branch pipes to the plurality of membrane units. At this
time, the cleaning chemical liquid distribution unit uses
an adjusting function provided by the pipeline
configuration to adjust a first force resulting mainly
from a pressure head and a second force resulting mainly
from a velocity head. The first force acts as a force
that pushes the cleaning chemical liquid in the header
toward an inlet of each of the branch pipes. The second

- 7 -
force acts as a force that sweeps away the cleaning
chemical liquid in the header in a pipe axis direction.
[0022]
Here, when the header is positioned above a liquid
level in the reaction vessel, the cleaning chemical
liquid flows in a non-full condition, that is, flows with
a gas phase present in the upper area of the header. The
cleaning chemical liquid thus flows through the branch
pipes to the collecting headers of the respective
membrane units. Moreover, to uniformly hold the chemical
liquid injected into the branch pipes, even in membrane
units each located at the tip of the corresponding branch
pipe, it is necessary to make the pressure in the branch
pipes uniform even after the cleaning chemical liquid has
passed through the branch pipes.
[0023]
At this time, to allow the cleaning chemical liquid
to flow uniformly into the branch pipes, it is necessary
to uniformly apply the supply pressure in the header to
the inlets of the branch pipes. Factors determining the
pressure (hereinafter referred to as the branch pipe
inlet supply pressure) include the amount of cleaning
chemical liquid supplied and flowing into the header, the
supply pressure (the pressure of the pump or the water
head in a vessel from which the cleaning chemical liquid
is fed), the flow velocity of the cleaning chemical
liquid flowing through the header, the ratio of the
header diameter and the branch pipe diameter, the
resistance of the pipeline, and gravity.
[0024]
A detailed description will be given below. FIGS. 1
and 2 show a configuration similar to that shown in FIG.
19. In FIG. 2, reference numeral la denotes an air
diffusing pipe in the membrane unit 1. Reference numeral
lb denotes a blower. FIG. 3 is a diagram as viewed in the

- 8 -
direction of arrow a-a in FIG. 1 and shows three cases in
which the branch pipes 3 have different structures. FIG.
4(a), (b) and (c) are graphs showing the flow rate of the
cleaning chemical liquid flowing from each of the branch
pipes 3 to the corresponding membrane unit 1 in each of
the configurations shown in FIG. 3. In the graph, for
reference numerals identifying the branch pipes 3, the
branch pipe 3 located closest to the start point (inlet)
of the header 2 in a flow direction is denoted by NO. 1.
The branch pipe 3 located closest to the terminal of the
header 2 in the flow direction is denoted by NO. 8.
[0025]
In the above-described configuration, when the branch
pipes 3 are connected to the header 2 in a horizontal
direction, the flow velocity of the cleaning chemical
liquid, one of the factors uniformizing the branch pipe
inlet supply pressure, has a greater impact than the
other factors.
[0026]
That is, as shown in FIG. 4(a), if the flow velocity
of the cleaning chemical liquid is high, the cleaning
chemical liquid has more difficulty flowing into the
branch pipes 3 located closer to the start point (inlet)
of the header. The cleaning chemical liquid flows more
easily into the branch pipes 3 located closer to the
terminal of the header 2.
[0027]
This phenomenon is attributed to the following. That
is, at the start point of the header, the second force
(resulting mainly from the velocity head) acts more
dominantly than the first force (resulting mainly from
the pressure head). The force sweeping away the cleaning
chemical liquid in the pipe axis direction of the header
2 dominates the force pushing the cleaning chemical
liquid toward the inlet of each branch pipe. On the other

_ 9 -
hand, at the terminal of the header, the flow of the
cleaning chemical liquid impacts the terminal of the
header 2 to increase the pressure head.
[0028]
When the branch pipes 3 are arranged so as to hang
from the header 2 in a vertical direction, the pressure
of the cleaning chemical liquid, one of the factors
uniformizing the branch pipe inlet supply pressure, has a
greater impact than the other factors.
[0029]
That is, as shown in FIG. 4(b), the cleaning chemical
liquid flows more easily into the branch pipes 3 located
closer to the start point (inlet) of the header. The
amount of cleaning chemical liquid reaching the terminal
of the header 2 decreases consistently with the distance
to the terminal of the header 2, making it more difficult
for the cleaning chemical liquid to flow into the branch
pipes 3 .
[0030]
This phenomenon is attributed to the following. That
is, in addition to the pressure head resulting from the
supply pressure of the pump, the gravity acts as a force
pushing the cleaning chemical liquid toward the inlet of
each branch pipe. Thus, at the start point of the header,
the first force (resulting mainly from the pressure head)
acts more dominantly than the second force (resulting
mainly from the velocity head). The force pushing the
cleaning chemical liquid toward the inlet of the branch
pipe dominates the force sweeping away the cleaning
chemical liquid in the pipe axis direction of the header
2. As a result, most of the cleaning chemical liquid
flows into the branch pipes 3 located closer to the start
point of the header, reducing the amount of cleaning
chemical liquid reaching the terminal of the header 2.
[0031]

- 10 -
Thus, according to the present invention, with the
"gravity" and "velocity head" taken into account, the
cleaning chemical liquid distribution unit includes the
pipeline configuration adjusting the first force and the
second force. This allows the cleaning chemical liquid to
flow uniformly to the plurality of membrane units through
the header and the branch pipes.
[0032]
A specific configuration of the cleaning chemical
liquid distribution unit is as follows. The header is
located along a direction in which the membrane units are
arranged and along a horizontal direction. Mounting axes
of the branch pipes are arranged parallel to one another.
The header is positioned above a liquid level in the
reaction vessel. Each of the branch pipes is inclined
with a falling gradient from the header toward the
collecting header at a predetermined angle.
[0033]
In this configuration, for example, the branch pipes
3 are inclined at 45 ° to the header 2 to adjust the
"gravity" and "velocity head" so as to uniformize the
branch pipe inlet supply pressure.
[0034]
That is, the rate of the gravity in the total force
of the gravity and the "pushing force", the first force,
to which the gravity is added, is adjusted by the
inclination of the branch pipes, to inhibit the flow of
an excessive amount of cleaning chemical liquid into the
branch pipes located closer to the start point of the
header, while the cleaning chemical liquid is swept away
toward the terminal of the header by the "sweeping force",
the second force. Thus, as shown in FIG. 4(c), the branch
pipe inlet supply pressure is uniformized such that the
cleaning chemical liquid flows uniformly into all the
branch pipes 3 .

- 11 -
[0035]
Furthermore, in this configuration, each branch pipe
has no valve reducing the pressure. The branch pipe is
not full of the cleaning chemical liquid, but a gas phase
is present therein. The branch pipe is also in
communication with the air, and all the branch pipes are
kept at a fixed pressure, the atmospheric pressure.
[0036]
Thus, the chemical liquid remaining inside the
membrane units can be kept uniform from membrane surfaces
in the membrane units each connected to the tip of the
corresponding branch pipe.
[0037]
That is, since each of the branch pipes is inclined
with the falling gradient from the header toward the
collecting header at the predetermined angle, the
cleaning chemical liquid can be uniformly distributed to
and contacted with the plurality of membrane units
through the header and the branch pipes.
[0038]
Another specific configuration of the cleaning
chemical liquid distribution unit is as follows. The
header is located along the direction in which the
membrane units are arranged and along the horizontal
direction. The mounting axes of the branch pipes are
arranged parallel to one another. The header is
positioned above the liquid level in the reaction vessel.
Each of the branch pipes has an overflow portion at a
predetermined height position above the header.
[0039]
In this configuration, the pressure head in the
header is set to a value at which the cleaning chemical
liquid is lifted to the overflow portion of each branch
pipe. In other words, the predetermined height position
of the overflow portion, formed in the branch pipe, is

- 12 -
set on the basis of the pressure head generated in the
cleaning chemical liquid in the header by the supply
pressure of the cleaning chemical liquid (the supply
pressure of the pump or the like) so that when the
cleaning chemical liquid flows through the overflow
portion, a gas phase is present in an upper area of the
overflow portion.
[0040]
During cleaning with the chemical liquid, the
cleaning chemical liquid flows so as to fill the header.
The cleaning chemical liquid flowing from the header to
the branch pipes overflows through the overflow portion
with a gas phase present in the upper area of the
overflow portion and flows to the collecting headers of
the respective membrane units.
[0041]
At this time, the interior of the header is full of
the cleaning chemical liquid to inhibit a possible
nonuniform branch pipe inlet supply pressure resulting
from the velocity head. Furthermore, the gravity does not
act as the "pushing force" pushing the cleaning chemical
liquid toward the inlet of the branch pipe. Instead, only
the pressure head (the supply pressure of the pump or the
like) acts as the "pushing force", the first force. The
pressure head lifts the cleaning chemical liquid to the
overflow portion against the gravity to allow the
cleaning chemical liquid to overflow.
[0042]
Therefore, since the branch pipe has the overflow
portion at the predetermined height position above the
header, the cleaning chemical liquid can be uniformly
distributed to and contacted with the plurality of
membrane units through the header and the branch pipes.
[0043]

- 13 -
Furthermore, an air open portion may be provided in
the overflow portion of each branch pipe. In this case,
the overflow portion is open to the air at the air open
portion. Thus, when the cleaning chemical liquid
overflows through the overflow portion, the gas phase in
the overflow portion is prevented from causing air lock.
The cleaning chemical liquid flows naturally downward
through the branch pipe under the atmospheric pressure to
the collecting header of the corresponding membrane unit.
The cleaning chemical liquid can thus be uniformly
distributed to and contacted with the plurality of
membrane units through the header and the branch pipes.
[0044]
Another specific configuration of the cleaning
chemical liquid distribution unit is as follows. The
header is located along the direction in which the
membrane units are arranged and along the horizontal
direction. The mounting axes of the branch pipes are
arranged parallel to one another. The header is
positioned below the liquid level in the reaction vessel.
Each of the branch pipes is connected to the header below
the liquid level.
[0045]
In this configuration, the cleaning chemical liquid
supplied to the header during cleaning with the chemical
liquid flows to each branch pipe so as to fill the header.
The cleaning chemical liquid then flows to the collecting
header of each membrane unit through the corresponding
branch pipe.
[0046]
At this time, since the header is positioned below
the liquid level in the reaction vessel, the interior of
the header is full of the cleaning chemical liquid. This
inhibits a possible nonuniform branch pipe inlet supply
pressure resulting from the velocity head.

- 14 -
[0047]
Furthermore, the water head corresponding to the
distance from the liquid level to the header acts as a
back pressure. Consequently, the gravity does not act as
the "pushing force" pushing the cleaning chemical liquid
toward the branch pipe inlet. Thus, only the pressure
head (the supply pressure of the pump or the like) acts
as the "pushing force", the first force, to push the
cleaning chemical liquid toward the branch pipe inlet.
The cleaning chemical liquid can thus be uniformly
distributed to and contacted with the plurality of
membrane units through the header and the branch pipes.
[0048]
Another specific configuration of the cleaning
chemical liquid distribution unit is as follows. The
header is located along the direction in which the
membrane units are arranged and along the horizontal
direction. The mounting axes of the branch pipes are
arranged parallel to one another. The header is
positioned at or above the liquid level. The header is
divided into a plurality of short pipelines each of which
is located for every predetermined number of membrane
units and each of which is in communication with a
cleaning chemical liquid supply source at a central part
thereof in a pipe axis direction.
[0049]
In the above-descried configuration, the cleaning
chemical liquid supplied to each header during cleaning
with the chemical liquid flows through the branch pipes
to the collecting headers of the respective membrane
units.
[0050]
At this time, since each of the short pipes of the
header is present for the corresponding one of the
membrane units and each short pipe is in communication

- 15 -
with the cleaning chemical liquid supply source at the
central part thereof in the pipe axis direction, the
liquid level and velocity head in the short pipes are
inhibited from being nonuniformly distributed. The
cleaning chemical liquid can thus be uniformly
distributed to and contacted with the plurality of
membrane units through the short pipes of the header and
the branch pipes.
[0051]
Another specific configuration of the cleaning
chemical liquid distribution unit is as follows. The
header is located at an equal distance in the vertical
direction from the plurality of membrane units circularly
arranged in the reaction vessel. The branch pipes
branching from the header are radially arranged. The
header is positioned at or above the liquid level.
[0052]
In this configuration, the cleaning chemical liquid
supplied to the header during cleaning with the chemical
liquid flows through the branch pipes to the collecting
headers of the respective membrane units.
[0053]
At this time, since the cleaning chemical liquid
flows from the header into the radially branching branch
pipes, the possible nonuniform distribution of the
velocity head in the header is avoided. The cleaning
chemical liquid can thus be uniformly distributed to and
contacted with the plurality of membrane units through
the header and the branch pipes.
[0054]
Another specific configuration of the cleaning
chemical liquid distribution unit is as follows. The
header is located along the direction in which the
membrane units are arranged and along the horizontal
direction. The mounting axes of the branch pipes are

- 16 -
arranged parallel to one another. The header is in
communication with the cleaning chemical liquid supply
source at the inlet of the header at one end thereof in
the pipe axis direction. The header has a pressure
control device provided at the other end thereof in the
pipe axis direction to maintain a pressure at less than
or equal to a set value.
[0055]
In this configuration, if an excessive amount of
cleaning chemical liquid is injected into the header to
exert an excessive pushing force pushing the cleaning
chemical liquid toward the inlet of each branch pipe, the
pressure control device is activated to release the
excessive pressure, preventing the excessive pressure
from acting on the membrane units.
[0056]
The pressure control device includes a pressure
sensing device, a valve device that is in communication
with the header, and a control device that opens the
valve device when a pressure detected by the pressure
sensing device reaches an upper limit value.
[0057]
Another specific configuration of the cleaning
chemical liquid distribution unit is as follows. The
header is located along the direction in which the
membrane units are arranged and along the horizontal
direction. The header is in communication with the
cleaning chemical liquid supply source at the inlet
thereof at one end thereof in the pipe axis direction and
with a return pipe at the outlet thereof at the other end
thereof in the pipe axis direction. The return pipe is in
communication with the inlet of the header or the
cleaning chemical liquid supply source.
[0058]

- 17 -
In this configuration, during cleaning with the
chemical liquid, a sufficient amount of cleaning chemical
liquid is allowed to flow to the header. The cleaning
chemical liquid flowing through the header flows through
the header and then the branch pipes to the collecting
headers of the respective membrane units. Part of the
cleaning chemical liquid returns to the inlet of the
header or the cleaning chemical liquid supply source
through the return pipe.
[0059]
Since the cleaning chemical liquid circulates through
the header and the return pipe, the velocity head is
inhibited from being nonuniformly distributed. This
prevents a possible nonuniform branch pipe inlet supply
pressure caused by the nonuniform distribution of the
velocity head. Furthermore, the "pushing force", the
first force, acts substantially uniformly over the entire
length of the header to uniformize the branch pipe inlet
supply pressure among all the branch pipes. The cleaning
chemical liquid can thus be uniformly distributed to and
contacted with the plurality of membrane units through
the header and the branch pipes.
[0060]
In particular, when the branch pipes are connected to
the header in the horizontal direction, the gravity does
not act as the force pushing the cleaning chemical liquid
toward the inlet of each branch pipe. Instead, only the
pressure head (the supply pressure of the pump or the
like) acts as the "pushing force", the first force. The
cleaning chemical liquid can thus be uniformly
distributed to and contacted with the plurality of
membrane units through the header and the branch pipes.
[0061]
The header is preferably located at the liquid level
position or above the liquid level position in the

- 18 -
reaction vessel in the horizontal direction. However, the
header may be located below the liquid level in the
reaction vessel. Furthermore, each branch pipe is
preferably connected to the header in the horizontal
direction. However, the branch pipe may be connected on a
slant to the header.
[0062]
When the header is positioned above the liquid level
in the reaction vessel, the cleaning chemical liquid
flows through the header in a non-full condition in which
a gas phase is present in the upper area of the header.
The cleaning chemical liquid thus flows through each
branch pipe to the collecting header of the corresponding
membrane unit.
Brief Description of the Drawings
[0063]
FIG. 1 is a front view of a large scale membrane
separating installation according to an embodiment of the
present invention;
FIG. 2 is a side view of the large scale membrane
separating installation according to the embodiment;
FIG. 3 is a sectional view taken along line a-a in
FIG. 1 illustrating differences in effects between the
embodiment of the present invention and conventional
embodiments;
FIG. 4(a), (b) and (c) are graphs showing differences
in effects among the configurations shown in FIG. 3;
FIG. 5 is an enlarged side view showing an essential
part of the large scale membrane separating installation
according to the embodiment of the present invention;
FIG. 6 is an enlarged front view showing an essential
part of the large scale membrane separating installation
according to the embodiment;

- 19 -
FIG. 7(a) and (b) are enlarged side views showing an
essential part of a large scale membrane separating
installation according to another embodiment of the
present invention, wherein FIG. 7(a) shows that a header
is located above a liquid level and FIG. 7(b) shows that
the header is located at the liquid level;
FIG. 8 is a schematic diagram showing a large scale
membrane separating installation according to another
embodiment of the present invention wherein a header is
located below the liquid level inside a vessel;
FIG. 9 is a schematic diagram showing a large scale
membrane separating installation according to another
embodiment of the present invention wherein a header is
located below the liquid level outside the vessel;
FIG. 10 is a front view of a large scale membrane
separating installation according to another embodiment
of the present invention;
FIG. 11 is a plan view of a large scale membrane
separating installation according to another embodiment
of the present invention;
FIG. 12 is an enlarged side view showing an essential
part of the large scale membrane installation device
according to the embodiment shown in FIG. 11;
FIG. 13 is a diagram showing the configuration of a
pressure control device according to another embodiment
of the present invention;
FIG. 14 is a front view of a large scale membrane
separating installation according to another embodiment
of the present invention;
FIG. 15 is a side view of the large scale membrane
separating installation according to the embodiment shown
in FIG. 14;
FIG. 16 is a front view of an essential part of a
large scale membrane separating installation according to
another embodiment of the present invention;

- 20 -
FIG. 17 is a diagram showing effects of the large
scale membrane separating installation according to the
present invention;
FIG. 18(a), (b) and (c) are diagrams illustrating
differences in effects between the embodiments of the
present invention and conventional embodiments; and
FIG. 19 is a front view showing a conventional large
scale membrane separating installation.
Best Mode for Carrying Out the Invention
[0064]
Embodiments of the present invention will be
described with reference to the drawings. The basic
configuration of large scale membrane separating
installations according to the present embodiments is
similar to that described with reference to FIGS. 1, 2,
and 16. Thus, the above-described reference numerals are
also used in the description below, and the description
of the basic configuration is omitted.
[0065]
In FIGS. 5 and 6, a plurality of membrane units 1 are
arranged in a reaction vessel. A header 2 is located
along a direction in which the membrane units 1 are
arranged and along a horizontal direction. A plurality of
branch pipes 3 branching from the header 2 are arranged
parallel to one another. Each of the branch pipes 3 is
connected to a collecting header (not shown) of a
corresponding one of the membrane units 1.
[0066]
The header 2 forms a channel with a diameter (large
diameter) required to ensure a smooth flow. Each of the
branch pipes 3 forms a channel with a diameter smaller
than that of the header 2. Each of the collecting headers
is provided for a casing of a corresponding one of the
membrane units 1.

- 21 -
[0067]
The header 2 is located in the horizontal direction
at a predetermined height h1 (for example, 1 m) from a
liquid level in the reaction vessel. Each branch pipe 3
is inclined with a falling gradient from the header 2
toward the corresponding collecting header at a
predetermined angle X (0BxNx0.2.
[0088]
The branch pipe inlet supply pressure in the header 2
can also be uniformized by a configuration shown in FIG.
10. In FIG. 10, the header 2 is located along the
direction in which the membrane units 1 are arranged and

- 27 -
along the horizontal direction. The header 2 is
positioned at or above the liquid level. The header 2 is
divided into a plurality of short pipes 2a each
corresponding to a predetermined number of membrane units
1. Each of the short pipes 2a is in communication with a
cleaning liquid supply pipeline 11 at a central part
thereof in a pipe axis direction. The branch pipes 3 can
be connected to the header 2 either in the horizontal
direction or in a vertical direction or in an inclining
direction.
[0089]
In this configuration, the cleaning chemical liquid
supplied to the header 2 during cleaning with the
chemical liquid flows through the branch pipes 3 to the
collecting headers of the respective membrane units. At
this time, since the header 2 is divided into the short
pipes 2a and each header 2 is in communication with the
cleaning liquid supply pipeline 11 at the central part
thereof in the pipe axis direction, the liquid level and
velocity head in the short pipes 2a of each header 2 are
inhibited from being nonuniformly distributed. The
cleaning chemical liquid can thus be uniformly
distributed to and contacted with the plurality of
membrane units 1 through the header 2 and the branch
pipes 3.
[0090]
The branch pipe inlet supply pressure in the header 2
can also be uniformized by a configuration shown in FIGS.
11 and 12. In FIGS. 11 and 12, the plurality of membrane
units 1, located in the reaction vessel, are circularly
arranged. The header 2 is located at an equal distance in
the vertical direction from the membrane units 1, that is,
at a central position of the membrane units 1. The header
2 is located at or above the liquid level. The branch
pipes 3 are arranged so as to branch radially from the

- 28 -
header 2 and connected to the collecting headers of the
respective membrane units 1.
[0091]
In this configuration, the cleaning chemical liquid
supplied to the header 2 during cleaning with the
chemical liquid flows through the branch pipes 3 to the
collecting headers of the respective membrane units 1. At
this time, since the cleaning chemical liquid flows into
the branch pipes 3 branching radially from the header 2,
the possible nonuniform distribution of the velocity head
in the header 2 is avoided. The pressure in the header 2
acts uniformly on the branch pipes 3, so that the
cleaning chemical liquid can be uniformly distributed to
and made in contact with the plurality of membrane units
1 through the header 2 and the branch pipes 3.
[0092]
Furthermore, as shown in FIG. 13, a pressure control
device 41 maintaining the pressure at less than or equal
to a set value may be provided at the terminal of the
header 2 in order to prevent an excessive pressure from
acting on the membrane units 1 through the header 2 and
the branch pipes 3. In this description, the header 2 is
positioned above the liquid level. However, the header 2
may be located below the liquid level.
[0093]
The pressure control device 41 is made up of a
pressure sensing device 42 that measures the pressure at
the terminal the header 2, a valve device 43 installed at
a position of a predetermined height h5 (for example, 2
m) from the liquid level in communication with the header
2, a control device 44 that opens the valve device 43
when the pressure detected by the pressure sensing device
42 reaches an upper limit value, and a valve device 45
provided in the cleaning liquid supply pipeline 11. A

- 29 -
second selector valve 10 may be configured so as to vary
the flow rate instead of providing the valve device 45.
[0094]
In this configuration, the design of the header 2 and
branch pipes 3 and the total inflow amount of cleaning
chemical liquid are adjusted such that for example, the
pressure in each branch pipe 3 is set to about 0 to 20
kPa. If the inflow of the liquid undergoes a high
resistance owing to unexpected dirt or the like in the
membrane unit, injection at a standard flow rate may
result in an excessive pushing force pushing the cleaning
chemical liquid toward the inlet of the branch pipe. Then,
when the detected pressure measured by the pressure
sensing device 42 of the pressure control device 41
reaches the upper limit value (which is set at, for
example, 20 kPa), the control device 44 controllably
opens and closes the valve devices 43 and 45 to release
the excessive pressure. This prevents the excessive
pressure from acting on the corresponding membrane unit 1,
to control the flow rate.
[0095]
The branch pipe inlet supply pressure in the header 2
can also be uniformized by a configuration shown in FIGS.
14 and 15.
[0096]
The header 2 is located along the direction in which
the membrane units 1 are arranged. The branch pipes 3
branching from the header 2 are connected to the
collecting headers of the respective membrane unit 1 (not
shown). The header 2 is located along the direction in
which the membrane units 1 are arranged and along the
horizontal direction. The header 2 is positioned at the
liquid level in the reaction vessel or at a predetermined
height from the liquid level. The branch pipes 3 are
connected to the header 2 in the horizontal direction.

- 30 -
[0097]
The header 2 is in communication with the cleaning
liquid supply pipeline 11 at the start point (inlet)
thereof in the flow direction. A first end of a return
pipe 51 is connected to the terminal (outlet) of the
header 2 in the flow direction. A second end of the
return pipe 51 is in communication with the inlet of the
header 2. An on-off valve 52 is provided in the return
pipe 51. The second end of the return pipe 51 can be
connected to the cleaning liquid supply pipeline 11.
Furthermore, as shown in FIG. 16, the first end of the
return pipe 51 may be connected to the branch pipe 3
positioned at the terminal of the header 2.
[0098]
In this configuration, during a filtration operation,
a valve 4 and a first selector valve 8 are open. The on-
off valve 52 and the second selector valve 10 are closed.
In this condition, a treated water pump 9 is driven to
apply a suction pressure to the membrane cartridges in
each of the membrane units 1. The suction pressure is
used as a driving pressure to perform a filtration
operation using the membrane cartridges. A filtrate
having permeated a filtration membrane flows through a
tube (not shown) into the collecting header (not shown).
The filtrate further flows through the branch pipe 3 to
the header 2 and then through a filtrate recovery
pipeline 6 into the treated water tank 7.
[0099]
During a backwashing operation, the valve 4, the
second selector valve 10 and the on-off valve 52 are open,
and the first selector valve 8 is closed. In this
condition, the submerged pump 12 is driven to supply
treated water in the treated water tank 7. The transfer
pump 16 is driven to supply the cleaning chemical liquid.
[0100]

- 31 -
At this time, since the header 2 is positioned above
the liquid level in the reaction vessel, the cleaning
chemical liquid flows through the header in the non-full
condition, that is, with the gas phase present in the
upper area of the header 2. The cleaning chemical liquid
flows through the header 2 and the branch pipes 3 to the
collecting headers of the respective membrane units. Part
of the cleaning chemical liquid returns to the inlet of
the header 2 or the cleaning liquid supply pipeline 11
through the return pipe 51. The cleaning chemical liquid
thus circulates through the header 2 and the return pipe
51.
[0101]
This inhibits the velocity head from being
nonuniformly distributed, preventing a possible
nonuniform branch pipe inlet supply pressure resulting
from the nonuniform distribution of the velocity head.
The "pushing force", the first force, acts substantially
uniformly over the entire length of the header 2 to
uniformize the branch pipe inlet supply pressure among
all the branch pipes 3. The cleaning chemical liquid can
thus be uniformly distributed to and contacted with the
plurality of membrane units 1 through the header 2 and
the branch pipes 3.
[0102]
Furthermore, since the branch pipes 3 are connected
to the header 2 in the horizontal direction, the gravity
does not act as the "pushing force" pushing the cleaning
chemical liquid toward the branch pipe inlet. Instead,
only the pressure head (in this case, the supply pressure
of the pump) acts as the "pushing force", the first force.
The cleaning chemical liquid can thus be uniformly
distributed to and contacted with the plurality of
membrane units 1 through the header 2 and the branch
pipes 3.

- 32 -
Embodiments
[0103]
Description will be given below of embodiments based
on calculations according to the present invention.
1. The cleaning chemical liquid flows through the
header 2 in the non-full condition (see FIG. 17).
1-1. The branch pipe 3 is located in the vertical
direction as shown in FIG. 18(a).
When Q=the flow rate in each branch pipe, a=the
channel cross section of the branch pipe, v=the flow
velocity in the branch pipe, V=the flow velocity in the
header, A=the channel cross section actually occupied by
the cleaning chemical liquid in the header, h=the water
level in the header, and g=9.8 m/s2, and it is assumed
that the installation has a single branch pipe, then
Q=vxa=sqrt(2gh)xa=VA.
[0104]
Thus, determining the channel cross section a of the
branch pipe and the flow rate Q in the branch pipe allows
the water level h in the header 2 to be determined
according to the formula:
h=QxQ/(axax2g).
Here, when the branch pipe diameter is assumed to be
50 mm and the flow rate in the branch pipe is assumed to
be 60 litters/min., a=0.002 m2, Q=0.001 m3/sec, and v=0.5.
The water depth in the header 2 is
h=0.001x0.001/(0.002x0.002x2x9.8)=0.0128 m=12.8 mm.
a) The header 2 has a diameter of 150 mm.
In this case, A=0.00073 m2 and V=Q/A=1.37 m/s.
Thus, to allow the cleaning chemical liquid to flow
uniformly through the 10 branch pipes 3, it is necessary
to set the inflow velocity to 10V=13.7 m/s.
[0105]
In a free fall from a height of 1 m, the cleaning
chemical liquid flows in at a flow velocity of 4.4 m/s.

- 33 -
Thus, for example, when the cleaning chemical liquid is
allowed to flow through the header 2 of diameter 150 mm
at the same flow rate, A=10Q/4.4=0.01/4.4=0.00227.
In this case, h=0.027 and
v=sqrt(2gh)=sqrt(2x9.8x0.027)=0.73.
The flow rate Ql in the first branch pipe:
Ql = 0 . 73x0.002 = 0.00146. The cleaning chemical liquid
flows through the first branch pipe at a flow rate about
1.5 times as large as a design value.
The flow rate Q2 in the second branch pipe:
Q2 is equivalent to Ql on the basis of
A=0.009854/4.4 = 0.00224 . As a result, the flow rates in
the first two branch pipes amount to nearly 30% of the
total value. Thus, the cleaning chemical liquid does not
flow to the last branch pipe.
[0106]
1-2. The branch pipe 3 is obliquely located at an
angle of 45° to the header as shown in FIG. 18(b).
As in the above-described case, Q=vxa=sqrt(2gh)xa=VA
and h=QxQ/(axax2g).
Here, when the branch diameter is assumed to be 50 mm
and the flow rate is assumed to be 60 litters/min.,
a=0.002 m2, Q=0.001 m3/sec, and the water depth h in the
header 2 = 0.001x0.001/(0.002x0.002x2x9.8)=0.0128 m=12.8
mm.
a) The header 2 has a diameter of 150 mm.
The center of the branch pipe is 0.022 m away from
the bottom surface thereof.
The total water depth is 0.0128+0.022=0.0348.
In this case, A=0.00298 m2 and V=Q/A=0.336 m/s.
This is the velocity at which the cleaning chemical
liquid flows in a free fall from a height of about 60 cm.
Therefore, when the header 2 has a diameter of 150 mm,
injection from a height of about 60 cm allows the

- 34 -
cleaning chemical liquid to be uniformly fed into each
branch pipe.
[0107]
1-3. The branch pipe 3 is located in the horizontal
direction as shown in FIG. 18 (c) .
As in the above-described case, Q=vxa=sqrt(2gh)xa=VA
and h=QxQ/(axax2g).
Here, when the branch diameter is assumed to be 50 mm
and the flow rate is assumed to be 60 litters/min.,
a=0.002 m2, Q=0.001 m3/sec, and the water depth h in the
header 2 = 0 . 001x0.001/(0.002x0.002x2x9 . 8) =0 . 0128 m=12.8
mm.
a) The header 2 has a diameter of 150 mm.
The center of the branch pipe is 0.075 m away from
the bottom surface thereof.
The total water depth is 0.0878.
In this case, A=0.0101 m2 and V=Q/A=0.10 m/s.
Thus, to allow the cleaning chemical liquid to flow
uniformly through the 10 branch pipes 3, it is necessary
to set the inflow velocity to 10V=1. m/s (from a height
of 0.05 m in a free fall).
In a free fall from a height of 1 m, the cleaning
chemical liquid flows in at a flow velocity of 4.4 m/s.
Thus, for example, when the cleaning chemical liquid is
allowed to flow through piping of diameter 100 mm at the
same flow rate, A=10Q/4.4 = 0.01/4.4 = 0 . 00227 .
In this case, the total water depth is 0.0325<0.075.
Thus, the water level is lower than the center (0.075) of
the branch pipe, preventing the cleaning chemical liquid
from flowing out of the first branch pipe.
As a result, the water level increases sequentially
from the terminal of the header, increasing the flow rate
in the corresponding branch pipes above the design value.
Furthermore, to bring the whole header into the full
condition, it is necessary that v=sqrt(2gh)=lm and

- 3 5 -
Q=10axsqrt(2gh)=10x0.002x1=0.2 m3/sec=120 ml/min. That is,
the flow rate needs to be doubled, preventing the header
from becoming full. Therefore, the water level increases
sequentially from the terminal of the header to increase
the flow rate in the corresponding branch pipes, while
reducing the flow rate in several branch pipes located
closer to the start point.

- 36 -
CLAIMS
1.- A large scale membrane separating installation
comprising a plurality of membrane units arranged in a
reaction vessel and a plurality of branch pipes branching
from a header and connected to collecting headers of the
respective membrane units so that a cleaning chemical
liquid flows through the header and the branch pipes to
the respective membrane units, wherein a cleaning
chemical liquid distribution unit comprises the header
and the branch pipes each having a smaller diameter than
the header, and the cleaning chemical liquid distribution
unit comprises a pipeline configuration uniformly
distributing the cleaning chemical liquid to be supplied
to the membrane units.
2. The large scale membrane separating installation
according to claim 1, wherein the cleaning chemical
liquid distribution unit adjusts a first force resulting
mainly from a pressure head and a second force resulting
mainly from a velocity head, and wherein the first force
acts as a force that pushes the cleaning chemical liquid
in the header toward an inlet of each of the branch pipes,
and the second force acts as a force that sweeps away the
cleaning chemical liquid in the header in a pipe axis
direction.
3 . The large scale membrane separating installation
according to claim 1, wherein the cleaning chemical
liquid distribution unit is configured such that the
header is located along a direction in which the membrane
units are arranged and along a horizontal direction,
mounting axes of the branch pipes are arranged parallel
to one another, the header is positioned above a liquid
level in the reaction vessel, and each of the branch
pipes is inclined with a falling gradient from the header
toward the collecting header at a predetermined angle.

- 37 -
4. The large scale membrane separating installation
according to claim 1, wherein the cleaning chemical
liquid distribution unit is configured such that the
header is located along a direction in which the membrane
units are arranged and along a horizontal direction,
mounting axes of the branch pipes are arranged parallel
to one another, the header is positioned above a liquid
level in the reaction vessel, and each of the branch
pipes has an overflow portion at a predetermined height
position above the header.
5 . The large scale membrane separating installation
according to claim 4, wherein an air open portion is
provided in the overflow portion of each branch pipe.
6. The large scale membrane separating installation
according to claim 1, wherein the cleaning chemical
liquid distribution unit is configured such that the
header is located along a direction in which the membrane
units are arranged and along a horizontal directions
mounting axes of the branch pipes are arranged parallel
to one another, the header is positioned below a liquid
level in the reaction vessel, and each of the branch
pipes is connected to the header below the liquid level.
7. The large scale membrane separating installation
according to claim 1, wherein the cleaning chemical
liquid distribution unit is configured such that the
header is located along a direction in which the membrane
units are arranged and along a horizontal direction,
mounting axes of the branch pipes are arranged parallel
to one another, the header is positioned at or above a
liquid level, and the header is divided into a plurality
of short pipelines each of which is located for every
predetermined number of membrane units and each of which
is in communication with a cleaning chemical liquid
supply source at a central part thereof in a pipe axis
direction.

^ - 3 8 -
8 . The large scale membrane separating installation
according to claim 1, wherein the cleaning chemical
liquid distribution unit is configured such that the
header is located at an equal distance in a vertical
direction from the plurality of membrane units circularly
arranged in the reaction vessel, the branch pipes
branching from the header are radially arranged, and the
header is positioned at or above a liquid level.
9. The large scale membrane separating installation
according to claim 1, wherein the cleaning chemical
liquid distribution unit is configured such that the
header is located along a direction in which the membrane
units are arranged and along a horizontal direction,
mounting axes of the branch pipes are arranged parallel
to one another, the header is in communication with a
cleaning chemical liquid supply source at an inlet of the
header at one end thereof in a pipe axis direction, and
the header has a pressure control device provided at the
other end thereof in the pipe axis direction to maintain
a pressure at less than or equal to a set value.
10. The large scale membrane separating installation
according to claim 9, wherein the pressure control device
comprises a pressure sensing device, a valve device that
is in communication with the header, and a control device
that opens the valve device when a pressure detected by
the pressure sensing device reaches an upper limit value.
11. The large scale membrane separating installation
according to claim 1, wherein the cleaning chemical
liquid distribution unit is configured such that the
header is located along a direction in which the membrane
units are arranged and along a horizontal direction, the
header is in communication with a cleaning chemical
liquid supply source at an inlet thereof at one end
thereof in a pipe axis direction and with a return pipe
at an outlet thereof at the other end thereof in the pipe

- 3 9 -
axis direction, and the return pipe is in communication
with the inlet of the header or the cleaning chemical
liquid supply source.

A large scale membrane separating installation
wherein a cleaning chemical liquid flows to membrane units through a header and branch pipes. A cleaning chemical liquid distribution unit comprises the header and the branch pipes having a diameter smaller than that of the header. The cleaning chemical liquid distribution
unit comprises a pipeline configuration uniformly
distributing the cleaning chemical liquid supplied to the membrane units.