Description
Technical Field
The present invention relates to a water treatment device that removes a solute
from a liquid to be treated, which is a treatment target, using a reverse osmosis membrane
to obtain a liquid having a low solute concentration, a 5 nd a method for operating the same.
Background Art
A water treatment device equipped with a reverse osmosis membrane device is a
water treatment device for obtaining freshwater from seawater or purifying industrial water
to obtain clean water.
10 A water treatment device described in Patent Literature 1 below is such a water
treatment device. Such a water treatment device has a plurality of reverse osmosis
membrane devices connected in series to a flow of a liquid to be treated, which is a
treatment target. In this water treatment device, a device for adding a disinfectant or an
alkaline fluid is installed upstream from the plurality of water treatment devices to prevent
15 organic materials from being adhered to or deposited on a reverse osmosis membrane or
the like.
Citation List
Patent Literature
Patent Literature 1
20 Japanese Unexamined Patent Application, First Publication No. 2008-238051
Summary of Invention
Technical Problem
In the technology described in Patent Literature 1 above, adhesion of fungus to a
reverse osmosis membrane or the like can be reliably inhibited, so that a drop in treatment
25 capability can be prevented. For this reason, water treatment can be continued over a
long period of time. However, a technology capable of continuing water treatment over a
longer period of time is required.
Accordingly, an object of the present invention is to provide a water treatment
3
device capable of continuing water treatment over a long period of time, and a method for
operating the same.
Solution to Problem
A water treatment device as an aspect according to the invention to achieve the
object includes: a primary reverse osmosis membrane device 5 having a primary casing and
a primary reverse osmosis membrane dividing an inside of the primary casing into a
primary liquid-passing part and a primary permeating part; a liquid-to-be-treated line
configured to feed a liquid to be treated, which is a treatment target, to the primary
liquid-passing part; a primary water feeder configured to feed the liquid to be treated to the
10 primary liquid-passing part under pressure via the liquid-to-be-treated line; a secondary
reverse osmosis membrane device having a secondary casing and a secondary reverse
osmosis membrane dividing an inside of the secondary casing into a secondary
liquid-passing part and a secondary permeating part; a primary treated liquid line
configured to feed a primary treated liquid, which is obtained by the liquid to be treated
15 passing through the primary reverse osmosis membrane device, to the secondary
liquid-passing part; a secondary water feeder installed on the primary treated liquid line
and configured to feed the primary treated liquid to the secondary permeating part at a
pressure higher than an osmotic pressure of the primary treated liquid; a bypass line
configured to connect the liquid-to-be-treated line and a position on the primary treated
20 liquid line, which is located between the primary reverse osmosis membrane device and
the secondary water feeder, and cause the liquid to be treated to bypass the primary reverse
osmosis membrane device; and a bypass-switching device configured to convert an
operation state including a normal operation state, in which the liquid to be treated is fed
from the liquid-to-be-treated line to the primary liquid-passing part of the primary reverse
25 osmosis membrane device and the primary treated liquid is fed from the primary reverse
osmosis membrane device to the secondary water feeder, to a bypass operation state in
which the liquid to be treated is fed from the liquid-to-be-treated line to the secondary
water feeder via the bypass line.
In the normal operation state of the water treatment device, the liquid to be treated
30 is fed into the primary liquid-passing part of the primary reverse osmosis membrane device
via the liquid-to-be-treated line by the primary water feeder. The primary treated liquid,
4
which is obtained by causing the liquid to be treated to pass through the primary reverse
osmosis membrane device, is fed to the secondary liquid-passing part of the secondary
reverse osmosis membrane device via the primary treated liquid line by the secondary
water feeder at the pressure higher than the osmotic pressure of the primary treated liquid.
For this reason, a part of the primary treated liquid 5 fed into the secondary liquid-passing
part under pressure drives reverse osmosis across the secondary reverse osmosis membrane,
and reaches the inside of the secondary permeating part as a permeated liquid. Of the
primary treated liquid fed into the secondary liquid-passing part, the primary treated liquid
that does not reach the inside of the secondary permeating part is discharged from the
10 secondary liquid-passing part with a solute concentrated.
In the normal operation state of the water treatment device, foreign materials are
easily deposited on the primary liquid-passing part of the primary reverse osmosis
membrane device disposed upstream of the secondary reverse osmosis membrane device.
For this reason, treatment capability of the primary reverse osmosis membrane device is
15 gradually reduced. Specifically, when the foreign materials are adhered to the inside of
the primary liquid-passing part and the treatment capability of the primary reverse osmosis
membrane device is reduced, there is a necessity of replacing this primary reverse osmosis
membrane device or overhauling this primary reverse osmosis membrane device.
Then, in the water treatment device, when the aforementioned necessity occurs,
20 the normal operation state of the primary reverse osmosis membrane device is switched to
the bypass operation state by the bypass-switching device.
In the bypass operation state, the liquid to be treated does not flow into the
primary reverse osmosis membrane device and is fed to the secondary liquid-passing part
of the secondary reverse osmosis membrane device under pressure by the secondary water
25 feeder via the bypass line and the primary treated liquid line. Like the above primary
treated liquid, the liquid to be treated fed into the secondary liquid-passing part under
pressure is treated by the secondary reverse osmosis membrane device.
In the bypass operation state, as described above, the liquid to be treated does not
flow into the primary reverse osmosis membrane device. For this reason, in the bypass
30 operation state, for example, the primary reverse osmosis membrane device can be
5
replaced with another primary reverse osmosis membrane device, or the primary reverse
osmosis membrane device can be overhauled.
As described above, in the bypass operation state of the water treatment device,
the primary reverse osmosis membrane device can be, for example, replaced with another
primary reverse osmosis membrane device while 5 treatment of the liquid to be treated is
performed by the secondary reverse osmosis membrane device. For this reason, in the
water treatment device, water treatment can be continued over a long period of time.
Since the bypass operation state is an operation state for, for example, replacing the
primary reverse osmosis membrane device with another primary reverse osmosis
10 membrane device, a process of performing the bypass operation state is temporarily
performed during a process of performing the normal operation state. For this reason,
even if this bypass operation state is performed, a large quantity of foreign materials can be
prevented from being deposited in the secondary liquid-passing parts of the plurality of
secondary reverse osmosis membrane devices, and a drop in treatment capability of the
15 secondary reverse osmosis membrane devices can be inhibited
Here, in the water treatment device, the primary water feeder may be a water
feeder that feeds the liquid to be treated to the primary liquid-passing part at a pressure
equal to or lower than the osmotic pressure of the liquid to be treated, and the primary
treated liquid line may be connected to the primary liquid-passing part side of the primary
20 casing and the secondary liquid-passing part side of the second casing.
In the primary reverse osmosis membrane device of the water treatment device,
the liquid to be treated does not drive reverse osmosis across the primary reverse osmosis
membrane, and passes through the primary liquid-passing part. For this reason, when
compared to a case in which the liquid to be treated drives reverse osmosis across the
25 primary reverse osmosis membrane in the primary reverse osmosis membrane device, a
drop in capability of discharging an inflowed liquid, namely treatment capability, can be
inhibited in the primary reverse osmosis membrane device. Therefore, in the water
treatment device, water treatment can be continued over a long period of time.
In any one water treatment device, in which a primary water feeder feeds a liquid
30 to be treated to a primary liquid-passing part at a pressure equal to or lower than an
6
osmotic pressure of the liquid to be treated, the primary casing may be formed with a
liquid-to-be-treated inflow port and a primary treated liquid outflow port, which
communicate the primary liquid-passing part and an outside with each other, and a
permeated liquid outflow port which communicates the primary permeating part and the
outside with each other, and the liquid-to-be-5 treated line may be connected to the
liquid-to-be-treated inflow port, and the primary treated liquid line may be connected to the
primary treated liquid outflow port.
The water treatment device, in which the casing is formed with the permeated
liquid outflow port, may include a backwashing device that feeds a backwashing liquid
10 which has a solute concentration that is lower than that of the liquid to be treated from the
permeated liquid outflow port to the primary permeating part, and a cleaning liquid
discharge line that discharges a liquid containing the backwashing liquid, which is fed to
the primary permeating part, passes through the primary reverse osmosis membrane, and
reaches the primary liquid-passing part, to the outside via the liquid-to-be-treated line or
15 the primary treated liquid line.
In the water treatment device, the inside of the primary reverse osmosis membrane
device can be backwashed. For this reason, in the water treatment device, even when
treatment capability of the primary reverse osmosis membrane device has dropped, the
treatment capability can be easily restored.
20 The water treatment device provided with the backwashing device may include a
backwashing-switching device configured to switch the operation state between the normal
operation state, in which the liquid to be treated is fed from the liquid-to-be-treated line
into the primary liquid-passing part via the liquid-to-be-treated inflow port and the primary
treated liquid fed from the primary liquid-passing part is fed to the secondary water feeder
25 via the primary treated liquid line, and a backwashing state, in which the liquid containing
the backwashing liquid, which is fed from the backwashing device to the primary
permeating part and reaches the primary liquid-passing part via the primary reverse
osmosis membrane, is discharged from the cleaning liquid discharge line to the outside via
the liquid-to-be-treated line or the primary treated liquid line.
30 In the water treatment device, an operation state of the primary reverse osmosis
7
membrane device can be easily switched to the backwashing state.
In the water treatment device provided with the backwashing-switching device,
the cleaning liquid discharge line may be connected to the liquid-to-be-treated line; the
water treatment device may include a backward passing liquid line that connects the
liquid-to-be-treated line and the primary 5 treated liquid line and guides the liquid to be
treated passing through the liquid-to-be-treated line from the primary treated liquid outflow
port to the primary liquid-passing part via the primary treated liquid line; the cleaning
liquid discharge line may be connected to the liquid-to-be-treated line at a position closer
to the liquid-to-be-treated inflow port side than a position at which the backward passing
10 liquid line is connected; and the backwashing-switching device may switch the operation
state between the normal operation state and the backwashing state, in which the
backwashing liquid from the backwashing device is fed to the primary permeating part, the
liquid to be treated is fed from the liquid-to-be-treated line into the primary liquid-passing
part via the backward passing liquid line, the primary treated liquid line, and the primary
15 treated liquid outflow port, and the liquid to be treated and the backwashing liquid flowing
out of the liquid-to-be-treated inflow port are discharged from the cleaning liquid discharge
line to the outside.
In the primary reverse osmosis membrane device, many foreign materials are
trapped at an upstream portion in the primary liquid-passing part, in other words, at a
20 portion of the liquid-to-be-treated inflow port side in the primary liquid-passing part, and
the many foreign materials are deposited at this portion. In the backwashing state in the
water treatment device, the liquid to be treated flows from the primary treatment outflow
port side to the liquid-to-be-treated inflow port side in the primary liquid-passing part, and
then flows in a direction opposite to the normal operation state. For this reason, in the
25 water treatment device, foreign materials deposited in the primary liquid-passing part of
the primary reverse osmosis membrane device can be efficiently removed.
The water treatment device provided with the backwashing-switching device may
include a controller configured to instruct the backwashing-switching device to switch the
operation state from the normal operation state to the backwashing state when preset
30 conditions are met.
8
The water treatment device provided with the backwashing-switching device may
include a differential pressure gauge configured to detect a pressure difference between a
pressure in the liquid-to-be-treated line and a pressure in the primary treated liquid line at a
position closer to the primary reverse osmosis membrane device side than the secondary
water feeder, and a controller configured to instruct 5 the backwashing-switching device to
switch the operation state from the normal operation state to the backwashing state when
the pressure difference detected by the differential pressure gauge in the normal operation
state is equal to or higher than a preset value.
When an amount of deposition of foreign materials in the primary liquid-passing
10 part of the primary reverse osmosis membrane device increases, resistance of the liquid to
be treated flowing in the primary liquid-passing part increases. A pressure difference
between a pressure of the liquid to be treated flowing into the liquid-to-be-treated inflow
port of the primary reverse osmosis membrane device and a pressure of the primary treated
liquid flowing out of the primary treated liquid outflow port is increased, and a flow rate of
15 the liquid passing through the primary liquid-passing part is reduced. Therefore, in the
water treatment device, when the pressure difference between the pressure in the
liquid-to-be-treated line and the pressure in the primary treated liquid line at the position
closer to the primary reverse osmosis membrane device side than the secondary water
feeder is higher than or equal to the preset value in the normal operation state, the
20 operation state of the primary reverse osmosis membrane device is switched to the
backwashing state. The inside of the primary reverse osmosis membrane device is
backwashed, and the flow rate of the liquid passing through the primary liquid-passing part
is restored.
In any one water treatment device provided with a controller, the controller may
25 instruct a bypass-switching device to switch an operation state from the normal operation
state to the bypass operation state and to switch the operation state from the bypass
operation state to the normal operation state.
In the water treatment device, the operation state of the primary reverse osmosis
membrane device can be easily switched to the bypass operation state.
30 In any one water treatment device provided with a backwashing device, the
9
backwashing device may have a backwashing liquid tank which is disposed at a higher
position than a primary reverse osmosis membrane device and in which a backwashing
liquid is stored, and a backwashing liquid line that connects the backwashing liquid tank
and a permeated liquid outflow port.
In the water treatment device, the backwashing 5 liquid in the primary permeating
part drives forward osmosis across the primary reverse osmosis membrane depending on
positive osmotic pressure and flows into the primary liquid-passing part. In the water
treatment device, a liquid pressure of a liquid level difference between a liquid level of the
backwashing liquid in the backwashing liquid tank and a liquid level of the backwashing
10 liquid in the primary permeating part is applied to the backwashing liquid in the primary
permeating part. For this reason, in the water treatment device, even when a pressure of
the backwashing liquid is not increased by a pump or the like, air stagnation or the like in
the primary permeating part can be prevented. Therefore, in the water treatment device,
power consumption caused by backwashing the inside of the primary reverse osmosis
15 membrane device can be inhibited.
Any one of the water treatment devices provided with the backwashing device
may include a permeated liquid feed line along which a permeated liquid, which is
obtained by the primary treated liquid passing through a secondary reverse osmosis
membrane of a secondary reverse osmosis membrane device, is fed to the backwashing
20 device as the backwashing liquid.
Since the permeated liquid is very low in solute concentration when compared to
the liquid to be treated, the permeated liquid easily drives forward osmosis across the
primary reverse osmosis membrane. Therefore, in the water treatment device, the
permeated liquid is used as the backwashing liquid so that backwashing can be efficiently
25 performed. Moreover, in the water treatment device, since the permeated liquid made by
the water treatment device itself is used, a cost for securing backwashing liquid can be
suppressed.
Any one water treatment device may include a disinfectant feeder configured to
feed a disinfectant for killing organisms in the primary liquid-passing part to the primary
30 liquid-passing part.
10
In the water treatment device, even when organisms such as fungi are propagated
in the primary liquid-passing part, the organisms can be removed. The disinfectant feeder
may feed the disinfectant into the primary liquid-passing part and the secondary
liquid-passing part.
Any one of the water treatment devices may 5 include an acidic agent feeder
configured to feed an acidic agent for removing scale in the secondary liquid-passing part
to the secondary liquid-passing part.
In the water treatment device, even when scale is deposited on the secondary
liquid-passing part, the scale can be removed. The acidic agent feeder may feed the
10 acidic agent into the primary liquid-passing part and the secondary liquid-passing part.
Any one water treatment device, in which a primary casing is formed with a
liquid-to-be-treated inflow port and a primary treated liquid outflow port, may include a
plurality of primary reverse osmosis membrane devices, inclusive of the aforementioned
primary reverse osmosis membrane device. A liquid-to-be-treated line may have a
15 liquid-to-be-treated main line that is connected to a primary water feeder, and
liquid-to-be-treated branch lines that branch from the liquid-to-be-treated main line to
respective primary reverse osmosis membrane devices and are connected to the
liquid-to-be-treated inflow ports of the respective primary reverse osmosis membrane
devices. The primary treated liquid line may have a primary treated liquid main line that
20 is connected to a secondary water feeder, and primary treated liquid branch lines that
branch from the primary treated liquid main line to respective primary reverse osmosis
membrane devices and are connected to the primary treated liquid outflow ports of the
respective primary reverse osmosis membrane devices. A bypass line causes a liquid to
be treated from the primary water feeder to bypass all the plurality of primary reverse
25 osmosis membrane devices.
In the water treatment device, the plurality of primary reverse osmosis membrane
devices are adapted to be disposed in parallel with respect to the liquid to be treated. For
this reason, in the water treatment device, when a capability of any one of the plurality of
primary reverse osmosis membrane devices is reduced, the other primary reverse osmosis
30 membrane devices can be maintained in the normal operation state while performing a
11
capability restoring treatment of the one primary reverse osmosis membrane device. For
this reason, in the water treatment device, water treatment can be continued over a long
period of time.
In any one of the water treatment devices, the primary reverse osmosis membrane
device and the secondary reverse osmosis membrane device 5 may be the same type of
reverse osmosis membrane device
In the water treatment device, since a foreign material deposition characteristic of
the primary reverse osmosis membrane device is the same as that of the secondary reverse
osmosis membrane device, a trapping characteristic of foreign materials that can be
10 deposited in the secondary liquid-passing part of the secondary reverse osmosis membrane
device and are trapped by the primary reverse osmosis membrane device can be enhanced.
It is preferable that the primary reverse osmosis membrane and the secondary reverse
osmosis membrane be formed of the same material or that a member for securing a flow
path of the primary liquid-passing part and a member for securing a flow path of the
15 secondary liquid-passing part be formed the same and of the same material to enhance the
trapping characteristic of foreign materials that can be deposited in the secondary
liquid-passing part of the secondary reverse osmosis membrane device and trapped by the
primary reverse osmosis membrane device.
A method for operating a water treatment device, which includes a plurality of
20 reverse osmosis membrane devices, each of which has a casing and a reverse osmosis
membrane dividing an inside of the casing into a liquid-passing part and a permeating part,
wherein the casing is formed with first and second ports that communicate the
liquid-passing part and an outside with each other and a third port that communicates the
permeating part and the outside with each other, as an aspect according to the invention to
25 achieve the object includes: a normal operating process which sets at least one of the
plurality of reverse osmosis membrane devices as a primary reverse osmosis membrane
device and the remaining reverse osmosis membrane devices as secondary reverse osmosis
membrane devices, and which feeds a liquid to be treated, which is a treatment target, from
the first port of the primary reverse osmosis membrane device into the liquid-passing part
30 under pressure, and feeding a liquid, which is obtained by the liquid to be treated passing
through the primary reverse osmosis membrane device, from the first ports of the
12
secondary reverse osmosis membrane devices into the liquid-passing parts of the
secondary reverse osmosis membrane devices as a primary treated liquid at a pressure
higher than an osmotic pressure of the primary treated liquid; a bypass-operating process
of causing the liquid to be treated to bypass the primary reverse osmosis membrane device,
and feeding the liquid to be treated from the first ports 5 of the secondary reverse osmosis
membrane devices into the liquid-passing parts of the secondary reverse osmosis
membrane devices at a pressure higher than an osmotic pressure of the liquid to be treated;
and a bypass-switching process of converting an operation state including a normal
operation state, which is a running operation state of the normal operating process, to a
10 bypass operation state, which is a running operation state of the bypass-operating process.
Here, in the method for operating a water treatment device, the normal operating
process may include feeding the liquid to be treated from the first port of the primary
reverse osmosis membrane device into the liquid-passing part at a pressure equal to or
lower than the osmotic pressure of the liquid to be treated, and feeding the liquid, which is
15 obtained by the liquid to be treated passing through the primary liquid-passing part and
being discharged from the second port, from the first ports of the secondary reverse
osmosis membrane devices into the liquid-passing parts as the primary treated liquid.
The method for operating a water treatment device, in which the liquid to be
treated is fed to the liquid-passing part of the primary reverse osmosis membrane device at
20 a pressure equal to or lower than the osmotic pressure of the liquid to be treated, may
include a backwashing process of feeding a backwashing liquid, which has a solute
concentration that is lower than that of the liquid to be treated, from the third port of the
primary reverse osmosis membrane device to the permeating part, and discharging a liquid
containing the backwashing liquid, which passes through the reverse osmosis membrane of
25 the primary reverse osmosis membrane device and reaches the liquid-passing part, to the
outside.
In the method for operating a water treatment device which performs the
backwashing process, the backwashing process may include feeding the liquid to be treated
from the second port of the primary reverse osmosis membrane device into the
30 liquid-passing part, and discharging the liquid to be treated to the outside via the first port
of the primary reverse osmosis membrane device along with the backwashing liquid that
13
reaches the liquid-passing part of the primary reverse osmosis membrane device.
Any one method for operating a water treatment device which performs the
backwashing process may include a backwashing-switching process of switching an
operation state between the normal operation state and the backwashing state, which is a
running 5 operation state of the backwashing process.
The method for operating a water treatment device which performs the
backwashing-switching process may include a pressure difference-detecting process of
detecting a pressure difference between a pressure of the liquid to be treated flowing
inward from the first port of the primary reverse osmosis membrane device and a pressure
10 of the primary treated liquid flowing out of the second port of the primary reverse osmosis
membrane device in the normal operation state. The backwashing-switching process may
include switching the operation state from the normal operation state to the backwashing
state when the pressure difference detected in the pressure difference-detecting process is
equal to or higher than a preset value.
15 In any one of the methods of operating a water treatment device which performs
the backwashing process, the backwashing process may include using a permeated liquid,
which is obtained by the primary treated liquid passing through the reverse osmosis
membranes of the secondary reverse osmosis membrane devices, as the backwashing
liquid.
20 In any one of the methods of operating a water treatment device which performs
the backwashing process, the water treatment device may include a plurality of primary
reverse osmosis membrane devices, inclusive of the primary reverse osmosis membrane
device. The water treatment device may perform the normal operation state in which,
when the backwashing process is performed on a first sub-device group of at least one of
25 the plurality of primary reverse osmosis membrane devices, the liquid to be treated is fed
into the liquid-passing part via first ports of a second sub-device group made up of the
other primary reverse osmosis membrane devices, and the primary treated liquid from the
liquid-passing part is fed to the secondary reverse osmosis membrane devices under
pressure. The bypass-operating process may include causing the liquid to be treated to
30 bypass all the plurality of primary reverse osmosis membrane devices.
14
Advantageous Effects of Invention
In an aspect of the present invention, water treatment can be continued over a long
period of time.
Brief Description of Drawings
Fig. 1 is a system diagram of a water treatment 5 device in a first embodiment
according to the present invention.
Fig. 2 is a development perspective view of major parts of a reverse osmosis
membrane device in the first embodiment according to the present invention.
Fig. 3 is a sectional view taken along line III-III in Fig. 2.
10 Fig. 4 is a system diagram (a normal operation state) of a primary treatment
system in the first embodiment according to the present invention.
Fig. 5 is a system diagram (a backwashing state) of the primary treatment system
in the first embodiment according to the present invention.
Fig. 6 is a system diagram (a bypass operation state) of the primary treatment
15 system in the first embodiment according to the present invention.
Fig. 7 is a system diagram (a normal operation state) of a primary treatment
system in a second embodiment according to the present invention.
Fig. 8 is a system diagram (a backwashing state) of the primary treatment system
in the second embodiment according to the present invention.
20 Fig. 9 is a system diagram (a bypass operation state) of the primary treatment
system in the second embodiment according to the present invention.
Description of Embodiments
Hereinafter, various embodiments of a water treatment device according to the
present invention will be described in detail with reference to the drawings.
25 (First embodiment)
15
A first embodiment of a water treatment device according to the present invention
will be described using Figs. 1 to 6.
The water treatment device of the present embodiment is a device that separates
seawater acting as a liquid to be treated into a concentrated liquid and freshwater and
obtains freshwater as treated water. However, 5 in the present invention, the liquid to be
treated may not be seawater and, for example, may be river water or industrial waste water.
As illustrated in Fig. 1, the water treatment device of the present embodiment is
provided with a primary treatment system 10 that primary treats seawater SW, which is a
liquid to be treated, to obtain a primary treated liquid W1, a secondary treatment system 70
10 that secondarily treats the primary treated liquid W1 to obtain a permeated liquid PW,
which is freshwater, and a secondarily treated liquid S2, which is a concentrated liquid, and
a controller 1 that controls operations of various valves or the like in the primary and
secondary treatment systems 10 and 70.
Both the primary treatment system 10 and the secondary treatment system 70 are
15 provided with a reverse osmosis membrane device. A reverse osmosis membrane device
80 is, as illustrated in Figs. 2 and 3, a spiral type reverse osmosis membrane device and has
a liquid-collecting pipe 95, a plurality of membrane devices 85 each of which has a reverse
osmosis membrane 86, and a cylindrical casing 81 covering the liquid-collecting pipe 95
and the plurality of membrane devices 85.
20 A liquid-to-be-treated inflow port (a first port) 82 into which a liquid that becomes
a treatment target flows is formed at one end of the cylindrical casing 81. A treated liquid
outflow port (a second port) 83 from which the liquid that does not pass through the
reverse osmosis membrane 86 flows and a permeated liquid outflow port (a third port) 84
from which a permeated liquid which is the liquid that passes through the reverse osmosis
25 membrane 86 flows are formed at the other end of the cylindrical casing 81.
The liquid-collecting pipe 95 is disposed along a center axis of the cylindrical
casing 81. A plurality of liquid-collecting holes 96 passing from an outer circumferential
side to an inner circumferential side are formed in the liquid-collecting pipe 95. An end
of the liquid-collecting pipe 95 which is close to the other end of the casing 81 is
30 connected to the permeated liquid outflow port 84.
16
Each of the membrane devices 85 has a reverse osmosis membrane 86 having a
sack shape, a permeated liquid flow path member 87 that is disposed in the saclike reverse
osmosis membrane 86 and secures a flow path of a permeated liquid that passes through
the reverse osmosis membrane 86, and a mesh spacer 88 that is disposed along an outer
surface of the saclike reverse osmosis membrane 86 5 and secures a flow path of the liquid
that is the treatment target. Therefore, in the reverse osmosis membrane device 80 of the
present embodiment, an inner side of the saclike reverse osmosis membrane 86 constitutes
a permeating part 92, and an outer side of the saclike reverse osmosis membrane 86
constitutes a liquid-passing part 91.
10 The plurality of membrane devices 85 are wound around the liquid-collecting pipe
95 in a spiral shape. An inner portion of the saclike reverse osmosis membrane 86 of
each of the membrane devices 85 communicates with the liquid-collecting holes 96 of the
liquid-collecting pipe 95. Therefore, the permeating part 92 communicates with the
outside via the permeated liquid outflow port 84 of the casing 81. An outer portion of the
15 saclike reverse osmosis membrane 86 of each of the membrane devices 85, namely the
liquid-passing part 91, communicates with the outside via the liquid-to-be-treated inflow
port 82 of the casing 81 and via the treated liquid outflow port 83 of the casing 81.
As illustrated in Fig. 1, the primary treatment system 10 is provided with, in
addition to a plurality of primary reverse osmosis membrane devices 80S, each of which
20 functions as the reverse osmosis membrane device 80 described above, a primary water
feed pump (a primary water feeder) 11 that pumps the seawater SW, which is the liquid to
be treated, and feeds the seawater SW to the primary reverse osmosis membrane devices
80S under pressure, a strainer 12 that removes foreign materials in the seawater SW which
the primary water feed pump 11 suctions, a cartridge filter 13 that removes fine foreign
25 materials contained in the seawater SW from the primary water feed pump 11, a
disinfectant feeder 20 that feeds a disinfectant for killing organisms such as fungi that are
present in the seawater SW fed to the primary reverse osmosis membrane devices 80S, an
acidic agent feeder 30 that feeds an acidic agent for removing inorganic scale in the
primary reverse osmosis membrane devices 80S, and a backwashing device 40 that
30 backwashes the insides of the primary reverse osmosis membrane devices 80S.
Hereinafter, the casings 81 and the reverse osmosis membranes 86 of the primary
17
reverse osmosis membrane devices 80S are referred to as primary casings 81 and primary
reverse osmosis membranes 86s, the liquid-passing parts 91 of the primary reverse osmosis
membrane devices 80S are referred to as primary liquid-passing parts 91s, the permeating
parts 92 of the primary reverse osmosis membrane devices 80S are referred to as primary
permeating parts 92s, the liquid-to-be-treated 5 inflow ports 82 of the primary reverse
osmosis membrane devices 80S are referred to as liquid-to-be-treated inflow ports 82s, the
treated liquid outflow ports 83 of the primary reverse osmosis membrane devices 80S are
referred to as primary treated liquid outflow ports 83s, and the permeated liquid outflow
ports 84 of the primary reverse osmosis membrane devices 80S are referred to as
10 permeated liquid outflow ports 84s.
A liquid-to-be-treated suction line 51 is connected to a suction port of the primary
water feed pump 11. The aforementioned strainer 12 is provided for the
liquid-to-be-treated suction line 51. A discharge port of the primary water feed pump 11
and the liquid-to-be-treated inflow ports 82s of the primary reverse osmosis membrane
15 devices 80S are connected by a liquid-to-be-treated discharge line (a liquid-to-be-treated
line) 52. The plurality of primary reverse osmosis membrane devices 80S are connected
in parallel to this liquid-to-be-treated discharge line 52. For this reason, the
liquid-to-be-treated discharge line 52 has a liquid-to-be-treated discharge main line 52m
that is connected to the primary water feed pump 11, and liquid-to-be-treated branch lines
20 52b that branch off from the liquid-to-be-treated discharge main line 52m to the respective
primary reverse osmosis membrane devices 80S and are connected to liquid-to-be-treated
inflow ports 82s of the primary reverse osmosis membrane devices 80S. The
aforementioned cartridge filter 13 is provided for the liquid-to-be-treated discharge main
line 52m. Liquid-to-be-treated inflow sluice valves 61 are installed on the plurality of
25 liquid-to-be-treated branch lines 52b, respectively.
The primary water feed pump 11 feeds the seawater SW into the primary
liquid-passing parts 91s of the primary reverse osmosis membrane devices 80S at a
pressure equal to or lower than an osmotic pressure of the seawater SW on the primary
reverse osmosis membranes 86s of the primary reverse osmosis membrane devices 80S.
30 The osmotic pressure of the seawater SW is approximately 30 bar. For this reason, the
primary water feed pump 11 is operated with a discharge pressure of, for example, about 5
bar.
18
The disinfectant feeder 20 has a disinfectant tank 21 in which a disinfectant is
stored, a disinfectant line 22 that connects the disinfectant tank 21 and the
liquid-to-be-treated discharge line 52, and a disinfectant pump 25 that feeds the
disinfectant in the disinfectant tank 21 to the liquid-to-be-treated discharge line 52 under
pressure. The disinfectant line 22 has a disinfectant 5 main line 22m that is connected to
the disinfectant tank 21 and disinfectant branch lines 22b that branch off from the
disinfectant main line 22m to the respective liquid-to-be-treated branch lines 52b and are
connected to the corresponding liquid-to-be-treated branch lines 52b. The disinfectant
pump 25 and a disinfectant sluice valve 26 are installed on the disinfectant main line 22m.
10 Disinfectant flow control valves 27 are respectively installed on the disinfectant branch
lines 22b. In the present embodiment, for example, a chlorine-based disinfectant such as
hypochlorous acid is used as the disinfectant. However, any disinfectant may be used as
the disinfectant according to a type of liquid to be treated as long as it can kill organisms
such as fungi.
15 The acidic agent feeder 30 has an acidic agent tank 31 in which the acidic agent is
stored, an acidic agent line 32 that connects the acidic agent tank 31 and the
liquid-to-be-treated discharge line 52, and an acidic agent pump 35 that feeds the acidic
agent in the acidic agent tank 31 into the liquid-to-be-treated discharge line 52 under
pressure. The acidic agent line 32 has an acidic agent main line 32m that is connected to
20 the acidic agent tank 31 and acidic agent branch lines 32b that branch off from the acidic
agent main line 32m to the plurality of respective liquid-to-be-treated branch lines 52b and
are connected to the corresponding liquid-to-be-treated branch lines 52b. The acidic
agent pump 35 and an acidic agent sluice valve 36 are installed on the acidic agent main
line 32m. Acidic agent flow control valves 37 are respectively installed on the acidic
25 agent branch lines 32b. In the present embodiment, for example, a sulfuric acid aqueous
solution is used as the acidic agent. However, when the liquid to be treated is the
seawater SW, other chemicals such as hydrochloric acid, nitric acid, etc. may be used as
the acidic agent as long as inorganic ions in the seawater SW, for example calcium ions,
magnesium ions, etc., can be precipitated to dissolve and remove scale adhered to the
30 reverse osmosis membranes 86.
The backwashing device 40 has a backwashing liquid tank 41 in which a
backwashing liquid BW is stored, a backwashing liquid line 42 that connects the
19
backwashing liquid tank 41 and the permeated liquid outflow ports 84s of the primary
reverse osmosis membrane devices 80S, and backwashing liquid sluice valves 46 that are
installed on the backwashing liquid line 42. The backwashing liquid tank 41 is provided
at a position higher than the primary reverse osmosis membrane devices 80S. The
backwashing liquid line 42 has a backwashing 5 liquid main line 42m that is connected to
the backwashing liquid tank 41, and backwashing liquid branch lines 42b that branch off
from the backwashing liquid main line 42m to the plurality of respective primary reverse
osmosis membrane devices 80S and are connected to the permeated liquid outflow ports
84s of the primary reverse osmosis membrane devices 80S. The aforementioned
10 backwashing liquid sluice valves 46 are respectively installed on the backwashing liquid
branch lines 42b.
A primary treated liquid line 55, along which the primary treated liquid W1
flowing out of the primary treated liquid outflow ports 83s is guided to the secondary
treatment system 70, is connected to the primary treated liquid outflow ports 83s of the
15 primary reverse osmosis membrane devices 80S. The primary treated liquid line 55 has a
primary treated liquid suction line 56 that guides the primary treated liquid W1 flowing
from the plurality of primary reverse osmosis membrane devices 80S to a secondary water
feed pump 71 (to be described below), and a primary treated liquid discharge line 73 that
guides the primary treated liquid W1, a pressure of which is raised by the secondary water
20 feed pump 71, to the secondary treatment system 70. The primary treated liquid suction
line 56 has a primary treated liquid suction main line 56m that is connected to a suction
port of the secondary water feed pump 71, and primary treated liquid branch lines 56b that
branch off from the primary treated liquid suction main line 56m to the plurality of
respective primary reverse osmosis membrane devices 80S and are connected to the
25 primary treated liquid outflow ports 83s of the primary reverse osmosis membrane devices
80S. Cleaning liquid discharge lines 58 are respectively connected to the primary treated
liquid branch lines 56b. Cleaning liquid sluice valves 63 are installed on the cleaning
liquid discharge lines 58. Primary treated liquid sluice valves 62 are respectively
installed on the primary treated liquid branch lines 56b at positions closer to the secondary
30 treatment system 70 than positions at which the cleaning liquid discharge lines 58 are
connected.
The primary treatment system 10 is further provided with differential pressure
20
gauges 89, each of which detects a pressure difference P between a pressure of the
seawater SW flowing into the primary liquid-passing part 91s of each of the primary
reverse osmosis membrane devices 80S and a pressure of the primary treated liquid W1
flowing out of the primary liquid-passing part 91s of the primary reverse osmosis
membrane devices 80S. The differential pressure gauges 5 89 are respectively provided for
the plurality of primary reverse osmosis membrane devices 80S. Each of the differential
pressure gauges 89 detects a pressure difference P between a pressure of the
liquid-to-be-treated branch line 52b at a position closer to the primary reverse osmosis
membrane device 80S than the liquid-to-be-treated inflow sluice valve 61 and a pressure of
10 the primary treated liquid branch line 56b at a position closer to the primary reverse
osmosis membrane device 80S than a position at which the cleaning liquid discharge line
58 is connected. In other words, in each of the primary reverse osmosis membrane
devices 80S, the differential pressure gauge 89 detects the pressure difference P between
the pressure of the seawater SW flowing from the liquid-to-be-treated inflow port 82s into
15 the primary liquid-passing part 91s and the pressure of the primary treated liquid W1
flowing out of the primary liquid-passing part 91s via the primary treated liquid outflow
port 83s.
The primary treatment system 10 is further provided with a bypass line 59 that
connects the liquid-to-be-treated discharge main line 52m and the primary treated liquid
20 suction main line 56m and causes the seawater SW to bypass all of the primary reverse
osmosis membrane devices 80S, and a bypass sluice valve 65 that is installed on the bypass
line 59.
The secondary treatment system 70 is provided with, in addition to a plurality of
secondary reverse osmosis membrane devices 80M, each of which functions as the reverse
25 osmosis membrane device 80 described above, the aforementioned secondary water feed
pump (the secondary water feeder) 71 that feeds the primary treated liquid W1 flowing out
of the primary liquid-passing parts 91s of the primary reverse osmosis membrane devices
80S to the secondary reverse osmosis membrane devices 80M under pressure, and a
permeated liquid pump 72 that feeds the permeated liquid PW, which passes through
30 secondary reverse osmosis membranes 86m which are the reverse osmosis membranes 86
of the secondary reverse osmosis membrane devices 80M, to many places under pressure
21
as freshwater.
Hereinafter, the casings 81 and the reverse osmosis membranes 86 of the
secondary reverse osmosis membrane devices 80M are used as secondary casings 81 and
the secondary reverse osmosis membranes 86m, the liquid-passing parts 91 of the
secondary reverse osmosis membrane devices 80M are 5 used as secondary liquid-passing
parts 91m, the permeating parts 92 of the secondary reverse osmosis membrane devices
80M are used as secondary permeating parts 92m, the liquid-to-be-treated inflow ports 82
of the secondary reverse osmosis membrane devices 80M are used as liquid-to-be-treated
inflow ports 82m, the treated liquid outflow ports 83 of the secondary reverse osmosis
10 membrane devices 80M are used as secondarily treated liquid outflow ports 83m, and the
permeated liquid outflow ports 84 of the secondary reverse osmosis membrane devices
80M are used as permeated liquid outflow ports 84m.
The secondary water feed pump 71 is installed on the aforementioned primary
treated liquid line 55. In other words, the primary treated liquid suction main line 56m of
15 the primary treated liquid line 55 is connected to the suction port of the secondary water
feed pump 71, and the primary treated liquid discharge line 73 of the primary treated liquid
line 55 is connected to a discharge port of the primary treated liquid line 55. The
secondary water feed pump 71 feeds the primary treated liquid W1 into the secondary
liquid-passing parts 91m of the secondary reverse osmosis membrane devices 80M at a
20 pressure higher than an osmotic pressure of the primary treated liquid W1 on the secondary
reverse osmosis membranes 86m of the secondary reverse osmosis membrane devices 80M.
Like the osmotic pressure of the seawater SW, which is the liquid to be treated, the osmotic
pressure of the primary treated liquid W1 is approximately 30 bar. For this reason, the
secondary water feed pump 71 is operated with a discharge pressure of, for example, about
25 65 bar, which is higher than 30 bar. The primary treated liquid discharge line 73 is
connected to a liquid-to-be-treated inflow port 82m of a first stage secondary reverse
osmosis membrane device 80Ma among the plurality of secondary reverse osmosis
membrane devices 80M.
The secondary liquid-passing parts 91m of the plurality of secondary reverse
30 osmosis membrane devices 80M are connected in series by secondarily treated liquid lines
97. To be specific, as described above, the primary treated liquid discharge line 73 is
22
connected to the liquid-to-be-treated inflow port 82m of the first stage secondary reverse
osmosis membrane device 80Ma among the plurality of secondary reverse osmosis
membrane devices 80M. The secondarily treated liquid outflow port 83m of the first
stage secondary reverse osmosis membrane device 80Ma and a liquid-to-be-treated inflow
port 82m of a second stage secondary reverse 5 osmosis membrane device 80Mb are
connected by the secondarily treated liquid line 97. In addition, the secondarily treated
liquid outflow port 83m of the second stage secondary reverse osmosis membrane device
80Mb and a liquid-to-be-treated inflow port 82m of a third stage secondary reverse
osmosis membrane device are connected by the secondarily treated liquid line 97. A
10 concentrated liquid line 98 is connected to a secondarily treated liquid outflow port 83m of
a final stage secondary reverse osmosis membrane device 80Mc.
The permeated liquid PW passing through the secondary reverse osmosis
membranes 86m of the plurality of secondary reverse osmosis membrane devices 80M is
fed to the aforementioned permeated liquid pump 72 via a permeated liquid line 74. The
15 permeated liquid line 74 has a permeated liquid discharge line 76 that is connected to a
discharge port of the permeated liquid pump 72, a permeated liquid suction main line 75m
that is connected to a suction port of the permeated liquid pump 72, and permeated liquid
suction branch lines 75b that branch off from the permeated liquid suction main line 75m
to the plurality of respective secondary reverse osmosis membrane devices 80M. The
20 permeated liquid suction branch lines 75b are respectively connected to the permeated
liquid outflow ports 84m of the secondary reverse osmosis membrane devices 80M.
The permeated liquid discharge line 76 and the backwashing liquid tank 41 of the
primary treatment system 10 are connected by a permeated liquid feed line 77 that feeds
the permeated liquid PW to the backwashing liquid tank 41 as the backwashing liquid. A
25 permeated liquid flow control valve 78 is installed on the permeated liquid feed line 77.
In the present embodiment, a bypass-switching device is made up of the
liquid-to-be-treated inflow sluice valves 61, the primary treated liquid sluice valves 62, and
the bypass sluice valve 65. A backwashing-switching device is made up of the primary
treated liquid sluice valves 62, the backwashing liquid sluice valves 46, and the cleaning
30 liquid sluice valves 63.
23
An operation of the water treatment device described above will be described.
First, a normal operating process of desalinating the seawater SW, which is the
liquid to be treated, will be described.
In the normal operation state, which is a running operation state of the normal
operating process, as illustrated in Fig. 4, each 5 of the liquid-to-be-treated inflow sluice
valves 61 and each of the primary treated liquid sluice valves 62 are opened. Meanwhile,
in the normal operation state, the disinfectant sluice valve 26, the disinfectant flow control
valves 27, the acidic agent sluice valve 36, the acidic agent flow control valves 37, the
backwashing liquid sluice valves 46, the cleaning liquid sluice valves 63, and the bypass
10 sluice valve 65 are closed.
The seawater SW pumped by the primary water feed pump 11 flows from the
liquid-to-be-treated inflow ports 82s of the primary reverse osmosis membrane devices
80S into the primary liquid-passing parts 91s of the primary reverse osmosis membrane
devices 80S via the strainer 12, the cartridge filter 13, the liquid-to-be-treated discharge
15 main line 52m, and the plurality of liquid-to-be-treated branch lines 52b. However, the
seawater SW is fed into the primary liquid-passing parts 91s by the primary water feed
pump 11 at or below an osmotic pressure of the seawater SW. For this reason, the
seawater SW passes through the primary liquid-passing parts 91s to flow from the primary
treated liquid outflow ports 83s of the primary reverse osmosis membrane devices 80S to
20 the primary treated liquid branch lines 56b as the primary treated liquid W1 without
driving reverse osmosis across the primary reverse osmosis membranes 86s.
Foreign materials, which are foreign materials of the seawater SW such as fungi
or inorganic matter that pass through the strainer 12 or the cartridge filter 13, are adhered
to the mesh spacers 88 (see Figs. 2 and 3) for securing flow paths in the primary
25 liquid-passing parts 91s or sides of the primary liquid-passing parts 91s of the primary
reverse osmosis membranes 86s in a process of passing through the primary liquid-passing
parts 91s. For this reason, in the primary treated liquid W1 flowing along the primary
treated liquid line 55, an amount of foreign materials that can be adhered to the mesh
spacers 88 for securing flow paths in the secondary liquid-passing parts 91m of the
30 secondary reverse osmosis membrane devices 80M or the secondary liquid-passing parts
24
91m sides of the secondary reverse osmosis membranes 86m is significantly reduced.
As illustrated in Fig. 1, the primary treated liquid W1 flowing to the primary
treated liquid branch line 56b of each of the plurality of primary reverse osmosis
membrane devices 80S flows into the secondary water feed pump 71 via the primary
treated liquid suction main line 56m. The primary 5 treated liquid W1 is fed into the
secondary liquid-passing part 91m of the first stage secondary reverse osmosis membrane
device 80Ma by the secondary water feed pump 71 at a pressure exceeding the osmotic
pressure of the primary treated liquid W1. For this reason, part of the primary treated
liquid W1 fed into the secondary liquid-passing part 91m of the first stage secondary
10 reverse osmosis membrane device 80Ma drives reverse osmosis across the secondary
reverse osmosis membrane 86m of the first stage secondary reverse osmosis membrane
device 80Ma and reaches the secondary permeating part 92m of the first stage secondary
reverse osmosis membrane device 80Ma. Of the primary treated liquid W1 fed into the
secondary liquid-passing part 91m of the first stage secondary reverse osmosis membrane
15 device 80Ma, the primary treated liquid W1 that does not reach the secondary permeating
part 92m flows from the secondarily treated liquid outflow port 83m of the first stage
secondary reverse osmosis membrane device 80Ma into the secondary liquid-passing part
91m of the second stage secondary reverse osmosis membrane device 80Mb via the
secondarily treated liquid line 97. A pressure loss of the primary treated liquid W1 in a
20 process of passing through the secondary liquid-passing part 91m of each of the secondary
reverse osmosis membrane devices 80M is less than 1 bar. For this reason, the part of the
primary treated liquid W1 fed into the secondary liquid-passing part 91m of the second
stage secondary reverse osmosis membrane device 80Mb drives reverse osmosis across the
secondary reverse osmosis membrane 86m of the second stage secondary reverse osmosis
25 membrane device 80Mb and reaches the secondary permeating part 92m of the second
stage secondary reverse osmosis membrane device 80Mb. Of the primary treated liquid
W1 fed into the secondary liquid-passing part 91m of the second stage secondary reverse
osmosis membrane device 80Mb, the primary treated liquid W1 that does not reach the
secondary permeating part 92m flows from the secondarily treated liquid outflow port 83m
30 of the second stage secondary reverse osmosis membrane device 80Mb into the secondary
liquid-passing part 91m of the third stage secondary reverse osmosis membrane device
80M via the secondarily treated liquid line 97. Hereinafter, the primary treated liquid W1
25
is also treated by the secondary reverse osmosis membrane devices 80M following the
third stage secondary reverse osmosis membrane device 80M in the same way.
The secondarily treated liquid S2, which is the treated liquid flowing out of the
secondary liquid-passing part 91m of the final stage secondary reverse osmosis membrane
device 80Mc, flows into the concentrated liqui 5 d line 98 and is discharged, for example, to a
sea or a treatment plant via the concentrated liquid line 98.
Meanwhile, the permeated liquid PW reaching the secondary permeating parts
92m of the plurality of secondary reverse osmosis membrane devices 80M flows into the
permeated liquid pump 72 via the permeated liquid suction branch line 75b provided for
10 each of the plurality of secondary reverse osmosis membrane devices 80M and the
permeated liquid suction main line 75m as freshwater. The permeated liquid PW flowing
into the permeated liquid pump 72 is raised in pressure by the permeated liquid pump 72,
and is fed to many places via the permeated liquid discharge line 76.
Part of the permeated liquid PW whose pressure is raised by the permeated liquid
15 pump 72 is fed to the backwashing liquid tank 41 via the permeated liquid feed line 77
connected to the permeated liquid discharge line 76. The backwashing liquid tank 41 is
provided with, for example, a liquid level gauge. The permeated liquid flow control
valve 78 installed on the permeated liquid feed line 77 is opened when a backwashing
liquid level detected in the backwashing liquid tank 41 by the liquid level gauge is equal to
20 or lower than a preset level, and the part of the permeated liquid PW whose pressure is
raised by the permeated liquid pump 72 is fed to the backwashing liquid tank 41.
When an amount of adhesion of foreign materials of the seawater SW such as
fungi or inorganic matter increases at the mesh spacers 88 disposed in the primary
liquid-passing parts 91s of the primary reverse osmosis membrane devices 80S or at the
25 sides of the primary liquid-passing parts 91s of the primary reverse osmosis membranes
86s, resistance of the seawater SW flowing into the primary liquid-passing parts 91s
increases so that a pressure difference P between a pressure of the seawater SW flowing
into each of the primary liquid-passing parts 91s of the primary reverse osmosis membrane
devices 80S and a pressure of the primary treated liquid W1 flowing out of each of the
30 primary liquid-passing parts 91s increases and a flow rate of the liquid passing through
26
each of the primary liquid-passing parts 91s is reduced. For this reason, water treatment
capability in the entire water treatment device is reduced.
Accordingly, in the present embodiment, when the pressure difference P detected
by any one of the plurality of differential pressure gauges 89 is equal to or greater than a
preset value, the controller 1 outputs, as illustrated in Fig. 5 5, a closing instruction to the
primary treated liquid sluice valve 62 that corresponds to the one primary reverse osmosis
membrane device 80S at which the pressure difference P is detected by the differential
pressure gauge 89 and an opening instruction to the backwashing liquid sluice valve 46 and
the cleaning liquid sluice valve 63 (a backwashing-switching process). As described
10 above, the backwashing-switching device is made up of the primary treated liquid sluice
valves 62, the backwashing liquid sluice valves 46, and the cleaning liquid sluice valves
63.
To be specific, the controller 1 outputs the opening instruction to the cleaning
liquid sluice valve 63 corresponding to the one primary reverse osmosis membrane device
15 80S and the closing instruction to the primary treated liquid sluice valve 62 corresponding
to the one primary reverse osmosis membrane device 80S. Afterwards, the controller 1
outputs the opening instruction to the backwashing liquid sluice valve 46 corresponding to
the one primary reverse osmosis membrane device 80S.
Like the normal operation state, the seawater SW flows from the
20 liquid-to-be-treated inflow ports 82s of the respective primary reverse osmosis membrane
devices 80S into the primary liquid-passing parts 91s of the respective primary reverse
osmosis membrane devices 80S via the liquid-to-be-treated discharge main line 52m and
the plurality of liquid-to-be-treated branch lines 52b. The seawater SW passes through
the primary liquid-passing parts 91s, and flows out of the primary treated liquid outflow
25 ports 83s of the respective primary reverse osmosis membrane devices 80S to the
respective primary treated liquid branch lines 56b as the primary treated liquid W1.
The primary treated liquid W1 flowing from the one primary reverse osmosis
membrane device 80S to the primary treated liquid branch line 56b corresponding to this
primary treated liquid branch line 56b is discharged to the outside via the cleaning liquid
30 discharge line 58 and the cleaning liquid sluice valve 63.
27
The backwashing liquid BW in the backwashing tank flows from the permeated
liquid outflow port 84s of the one primary reverse osmosis membrane device 80S into the
primary permeating part 92s via the backwashing liquid main line 42m, the backwashing
liquid branch line 42b connected to the one primary reverse osmosis membrane device 80S,
and the backwashing liquid sluice valve 46 installed 5 on the backwashing liquid branch line
42b.
A concentration of a solute (salt) contained in the backwashing liquid BW
(freshwater) in the primary permeating parts 92s of the primary reverse osmosis membrane
devices 80S is lower than a concentration of a solute (salt) contained in the seawater SW in
10 the primary liquid-passing parts 91s. For this reason, the backwashing liquid BW in the
primary permeating parts 92s drives forward osmosis across the primary reverse osmosis
membranes 86s depending on a positive osmotic pressure and flows into the primary
liquid-passing parts 91s. Furthermore, since the backwashing liquid tank 41 is disposed
at a place that is higher than the primary reverse osmosis membrane devices 80S, a liquid
15 pressure of a liquid level difference between a liquid level of the backwashing liquid BW
in the backwashing liquid tank 41 and a liquid level of the backwashing liquid BW in the
primary permeating parts 92s is applied to the backwashing liquid BW in the primary
permeating parts 92s. Therefore, the backwashing liquid BW in the primary permeating
parts 92s passes through the primary reverse osmosis membranes 86s and more easily
20 flows into the primary liquid-passing parts 91s. In this process, foreign materials adhered
to either the mesh spacers 88 for securing flow paths in the primary liquid-passing parts
91s or the sides of the primary liquid-passing parts 91s of the primary reverse osmosis
membranes 86s are stripped from the mesh spacers 88 or the primary reverse osmosis
membranes 86s. These foreign materials are discharged from the primary treated liquid
25 outflow ports 83s of the primary reverse osmosis membrane devices 80S to the outside via
the primary treated liquid suction line 56, the cleaning liquid discharge lines 58, and the
cleaning liquid sluice valves 63 along with the backwashing liquid BW and the seawater
SW in the primary liquid-passing parts 91s. That is, operation states of the primary
reverse osmosis membrane devices 80S become backwashing states, and the primary
30 reverse osmosis membrane devices 80S are backwashed by the backwashing liquid BW (a
backwashing process).
The primary treated liquid W1 flowing out of the primary reverse osmosis
28
membrane devices 80S excluding the one primary reverse osmosis membrane device 80S
merges at the primary treated liquid suction main line 56m via the primary treated liquid
branch line 56b and is fed into the secondary liquid-passing parts 91m of the plurality of
secondary reverse osmosis membrane devices 80M of the secondary treatment system 70
by the secondary water feed pump 71 at a pressure exceeding 5 the osmotic pressure of the
primary treated liquid W1. Therefore, the primary reverse osmosis membrane devices
80S excluding the one primary reverse osmosis membrane device 80S is maintained in the
normal operation state. For this reason, even when the one primary reverse osmosis
membrane device 80S is backwashed, a desalinization treatment of the seawater SW in the
10 water treatment device of the present embodiment is continued.
Depending on the backwashing described above, when the pressure difference P
between the pressure of the seawater SW flowing into the primary liquid-passing part 91s
of the one primary reverse osmosis membrane device 80S and the pressure of the primary
treated liquid W1 flowing out of the primary liquid-passing part 91s is reduced and the
15 flow rate of the liquid passing through the primary liquid-passing part 91s is restored, the
controller 1 outputs the opening instruction to the primary treated liquid sluice valve 62
and the closing instruction to the backwashing liquid sluice valve 46 and the cleaning
liquid sluice valve 63 (the backwashing-switching process). As a result, as illustrated in
Fig. 4, the operation state of the one primary reverse osmosis membrane device 80S returns
20 to the normal operation state.
Even when the one primary reverse osmosis membrane device 80S is backwashed,
if the pressure difference P between the pressure of the seawater SW flowing into the
primary liquid-passing part 91s of the primary reverse osmosis membrane device 80S and
the pressure of the primary treated liquid W1 flowing out of the primary liquid-passing part
25 91s is reduced, the controller 1 outputs the opening instruction to the disinfectant sluice
valve 26 and the disinfectant flow control valve 27 corresponding to the one primary
reverse osmosis membrane device 80S and a driving instruction to the disinfectant pump
25. As a result, the disinfectant in the disinfectant tank 21 flows into the primary
liquid-passing part 91s of the one primary reverse osmosis membrane device 80S via the
30 disinfectant main line 22m, the disinfectant branch line 22b, and the liquid-to-be-treated
branch line 52b along with the seawater SW.
29
If organisms such as fungi are propagated in the primary liquid-passing parts 91s
and are adhered to the mesh spacers 88 for securing the flow paths in the primary
liquid-passing parts 91s or the sides of the primary liquid-passing parts 91s of the primary
reverse osmosis membranes 86s, the organisms such as fungi are killed and stripped from
the mesh spacers 88 or the primary reverse 5 osmosis membranes 86s. The killed
organisms are discharged from the primary treated liquid outflow port 83s of the one
primary reverse osmosis membrane device 80S to the outside via the primary treated liquid
branch line 56b, the cleaning liquid discharge line 58, and the cleaning liquid sluice valve
63 along with the seawater SW and the disinfectant flowing into the primary liquid-passing
10 part 91s.
Even when the inside of the one primary reverse osmosis membrane device 80S is
disinfected, if the pressure difference P between the pressure of the seawater SW flowing
into the primary liquid-passing part 91s of this primary reverse osmosis membrane device
80S and the pressure of the primary treated liquid W1 flowing out of the primary
15 liquid-passing part 91s is reduced, the controller 1 outputs the closing instruction to the
disinfectant sluice valve 26 and the disinfectant flow control valve 27 and a stop
instruction to the disinfectant pump 25 and stops a disinfecting treatment of the inside of
the primary reverse osmosis membrane device 80S. Then, the controller 1 outputs the
opening instruction to the acidic agent sluice valve 36 and the acidic agent flow control
20 valve 37 corresponding to the one primary reverse osmosis membrane device 80S and the
driving instruction to the acidic agent pump. As a result, the acidic agent in the acidic
agent tank 31 flows into the primary liquid-passing part 91s of the one primary reverse
osmosis membrane device 80S via the acidic agent main line 32m, the acidic agent branch
line 32b, and the liquid-to-be-treated branch line 52b along with the seawater SW.
25 If inorganic matters are deposited in each of the primary liquid-passing parts 91s
as scale, the scale is dissolved. The dissolved scale is discharged from the primary
treated liquid outflow port 83s of the one primary reverse osmosis membrane device 80S to
the outside via the primary treated liquid branch line 56b, the cleaning liquid discharge line
58, and the cleaning liquid sluice valve 63 along with the seawater SW and the acidic agent
30 flowing into the primary liquid-passing parts 91s.
In the above description, a dissolving treatment of an inorganic scale component
30
is performed after the disinfecting treatment. However, the disinfecting treatment may be
performed after the dissolving treatment of an inorganic scale component.
Even when the backwashing treatment, the disinfecting treatment, and the
dissolving treatment of an inorganic scale component are performed on any one of the
primary reverse osmosis membrane devices 80S, if the 5 pressure difference P between the
pressure of the seawater SW flowing into the primary liquid-passing part 91s of this
primary reverse osmosis membrane device 80S and the pressure of the primary treated
liquid W1 flowing out of the primary liquid-passing part 91s is reduced, the necessity of,
for example, replacing this primary reverse osmosis membrane device 80S with another
10 primary reverse osmosis membrane device 80S or overhauling this primary reverse
osmosis membrane device 80S occurs. In this case, the liquid-to-be-treated inflow sluice
valve 61, the primary treated liquid sluice valve 62, and the backwashing liquid sluice
valve 46 which correspond to this primary reverse osmosis membrane device 80S are
closed. In this state, this primary reverse osmosis membrane device 80S is, for example,
15 replaced with another primary reverse osmosis membrane device 80S.
The necessity of replacing all of the primary reverse osmosis membrane devices
80S with other primary reverse osmosis membrane devices 80S or overhauling each of the
primary reverse osmosis membrane devices 80S may occur.
Accordingly, in this case, in the present embodiment, for example, an operator of
20 the water treatment device instructs the controller 1 to switch the operation state of each of
the primary reverse osmosis membrane devices 80S from the normal operation state to a
bypass operation state.
As illustrated in Fig. 6, when the controller 1 receives a switching instruction, the
controller 1 outputs the closing instruction to the plurality of the liquid-to-be-treated inflow
25 sluice valves 61 and the plurality of primary treated liquid sluice valves 62 and the opening
instruction to the bypass sluice valve 65 (a bypass-switching process). As described
above, the bypass-switching device is made up of the liquid-to-be-treated inflow sluice
valves 61, the primary treated liquid sluice valves 62, and the bypass sluice valve 65. To
be specific, the controller 1 outputs the closing instruction to the plurality of
30 liquid-to-be-treated inflow sluice valves 61 and the opening instruction to the bypass sluice
31
valve 65 first. Next, the controller 1 outputs the closing instruction to the primary treated
liquid sluice valves 62.
As a result, the seawater SW from the liquid-to-be-treated discharge main line
52m does not flow into each of the primary reverse osmosis membrane devices 80S via the
liquid-to-be-treated branch line 52b and flows into the 5 secondary water feed pump 71 via
the bypass line 59 and the primary treated liquid suction main line 56m (a bypass-operating
process).
The seawater SW flowing into the secondary water feed pump 71 is fed into the
secondary liquid-passing parts 91m of the plurality of secondary reverse osmosis
10 membrane devices 80M of the secondary treatment system 70 by the secondary water feed
pump 71 at a pressure exceeding the osmotic pressure of the seawater SW and is treated by
the plurality of secondary reverse osmosis membrane devices 80M similarly as above.
In the bypass operation state, which is a running operation state of the
bypass-operating process, the seawater SW does not flow into each of the primary reverse
15 osmosis membrane devices 80S. For this reason, in the bypass operation state, a task of,
for example, replacing each of the primary reverse osmosis membrane devices 80S with
another primary reverse osmosis membrane device 80S or overhauling each of the primary
reverse osmosis membrane devices 80S is performed.
As described above, in the present embodiment, since the primary reverse osmosis
20 membrane devices 80S are disposed upstream from the secondary reverse osmosis
membrane devices 80M and since foreign materials that can be deposited on the secondary
liquid-passing parts 91m of the secondary reverse osmosis membrane devices 80M are
trapped by the primary reverse osmosis membrane devices 80S, a drop in water treatment
capability in the secondary reverse osmosis membrane devices 80M can be inhibited. In
25 the present embodiment, especially since the primary reverse osmosis membrane devices
80S and the secondary reverse osmosis membrane devices 80M are the same type of
reverse osmosis membrane device 80 and have the same deposition characteristics of
foreign materials, a trapping characteristic of foreign materials, which can be deposited in
the secondary liquid-passing parts 91m of the secondary reverse osmosis membrane
30 devices 80M and are trapped by the primary reverse osmosis membrane devices 80S, can
32
be enhanced. In the primary reverse osmosis membrane devices 80S, the seawater SW
only passes through the primary liquid-passing parts 91s without driving reverse osmosis
across the primary reverse osmosis membranes 86s. For this reason, in comparison with a
case in which the seawater SW drives reverse osmosis across the primary reverse osmosis
membranes 86s in the primary reverse osmosis membrane 5 devices 80S, a drop in the
capability of discharging an inflowed liquid, namely the treatment capability, can be
inhibited in the primary reverse osmosis membrane devices 80S. To enhance the trapping
characteristic of foreign materials, which can be deposited on the secondary liquid-passing
parts 91m of the secondary reverse osmosis membrane devices 80M and are trapped by the
10 primary reverse osmosis membrane devices 80S, it is preferable that the primary reverse
osmosis membranes 86s and the secondary reverse osmosis membranes 86m be formed of
the same material and that members for securing the flow paths of the primary
liquid-passing parts 91s and members for securing the flow paths of the secondary
liquid-passing parts 91m be formed the same and of the same material.
15 Therefore, in the present embodiment, a drop in the water treatment capability in
the water treatment device can be inhibited. As a result, water treatment can be
performed over a long period of time.
Further, in the present embodiment, even if the operation state of one primary
reverse osmosis membrane device 80S is set to the backwashing state or a state in which
20 the disinfecting treatment or the dissolving treatment of inorganic scale is performed on the
one primary reverse osmosis membrane device 80S, the desalinization treatment of the
seawater SW can be continued by another primary reverse osmosis membrane device 80S
and the plurality of secondary reverse osmosis membrane devices 80M. Therefore, in the
present embodiment, from this viewpoint, water treatment can be continued over a long
25 period of time.
Further, in the present embodiment, the bypass-operating process is performed
while the desalinization treatment of the seawater SW is performed by the plurality of
secondary reverse osmosis membrane devices 80M, and thereby the plurality of primary
reverse osmosis membrane devices 80S can be, for example, replaced with other primary
30 reverse osmosis membrane devices 80S. For this reason, in the present embodiment,
from this viewpoint, water treatment can be continued over a long period of time. Since
33
the bypass-operating process is a process of, for example, replacing the plurality of
primary reverse osmosis membrane devices 80S with other primary reverse osmosis
membrane devices 80S, the bypass-operating process is temporarily performed during the
normal operating process. For this reason, even if this bypass-operating process is
performed, a large quantity of foreign materials can 5 be prevented from being deposited on
the secondary liquid-passing parts 91m of the plurality of secondary reverse osmosis
membrane devices 80M, and a drop in the treatment capability of the plurality of
secondary reverse osmosis membrane devices 80M can be inhibited.
Since the water treatment device of the present embodiment is provided with the
10 backwashing device 40 that backwashes the primary reverse osmosis membrane devices
80S, the disinfectant feeder 20 that disinfects the primary reverse osmosis membrane
devices 80S, and the acidic agent feeder 30 that dissolves an inorganic scale component of
the primary reverse osmosis membrane devices 80S, even when the treatment capability of
the primary reverse osmosis membrane devices 80S is reduced, this treatment capability
15 can be easily restored.
In the backwashing device 40 of the present embodiment, since a liquid pressure
is applied to the backwashing liquid BW in the primary permeating parts 92s of the
primary reverse osmosis membrane devices 80S using a liquid level difference, air
stagnation or the like in the primary permeating parts 92s can be prevented even when the
20 backwashing liquid BW is not raised in pressure by the pump or the like. Therefore,
power consumption can be inhibited in the backwashing device 40.
(Second embodiment)
A second embodiment of the water treatment device according to the present
invention will be described using Figs. 7 to 9.
25 Like the water treatment device of the first embodiment, as illustrated in Fig. 7, a
water treatment device of the present embodiment is provided with a primary treatment
system 10a, a secondary treatment system 70, and a controller 1. The secondary
treatment system 70 of the present embodiment is identical to the secondary treatment
system 70 of the first embodiment. Meanwhile, when compared to the primary treatment
30 system 10 of the first embodiment, the primary treatment system 10a of the present
34
embodiment has different piping lines around primary reverse osmosis membrane devices
80S although various devices themselves including the primary reverse osmosis membrane
devices 80S are the same.
Even in the present embodiment, the plurality of primary reverse osmosis
membrane devices 80S are connected in parallel to a liquid-5 to-be-treated discharge line 52.
As in the first embodiment, the liquid-to-be-treated discharge line 52 has a
liquid-to-be-treated discharge main line 52m that is connected to a primary water feed
pump 11, and liquid-to-be-treated branch lines 52b that branch off from the
liquid-to-be-treated discharge main line 52m to the plurality of respective primary reverse
10 osmosis membrane devices 80S and are connected to liquid-to-be-treated inflow ports 82s
of the primary reverse osmosis membrane devices 80S. Liquid-to-be-treated inflow
sluice valves 61 are respectively installed on the liquid-to-be-treated branch lines 52b.
Cleaning liquid discharge lines 58a are respectively connected to the liquid-to-be-treated
branch lines 52b at positions closer to the primary reverse osmosis membrane devices 80S
15 than positions at which the liquid-to-be-treated inflow sluice valves 61 are provided.
Cleaning liquid sluice valves 63 are installed on the cleaning liquid discharge lines 58a.
As in the first embodiment, a primary treated liquid line 55 has a primary treated
liquid suction line 56 that guides a primary treated liquid W1 flowing out of the plurality of
primary reverse osmosis membrane devices 80S to a secondary water feed pump 71, and a
20 primary treated liquid discharge line 73 that guides the primary treated liquid W1, a
pressure of which is raised by the secondary water feed pump 71, to the secondary
treatment system 70. The primary treated liquid suction line 56 has a primary treated
liquid suction main line 56m that is connected to the secondary water feed pump 71, and
primary treated liquid branch lines 56b that branch off from the primary treated liquid
25 suction main line 56m to respective primary reverse osmosis membrane devices 80S and
are connected to primary treated liquid outflow ports 83s of the primary reverse osmosis
membrane devices 80S. Primary treated liquid sluice valves 62 are respectively installed
on the primary treated liquid branch lines 56b.
Further, the primary treatment system 10a of the present embodiment has
30 backward passing liquid lines 54 respectively provided for the plurality of primary treated
liquid branch lines 56b. One end of each of the backward passing liquid lines 54 is
35
connected to the liquid-to-be-treated discharge main line 52m, and the other end of each of
the backward passing liquid lines 54 is connected to the primary treated liquid branch line
56b. The other ends of the backward passing liquid lines 54 are connected to the primary
treated liquid branch lines 56b at positions closer to the primary reverse osmosis
membrane devices 80S than positions at which the primary 5 treated liquid sluice valves 62
are provided. The backward passing liquid lines 54 are connected to the
liquid-to-be-treated discharge line 52 and the primary treated liquid suction line 56 and
guide seawater SW, which passes through the liquid-to-be-treated discharge line 52, from
the primary treated liquid outflow ports 83s to primary liquid-passing parts 91s of the
10 primary reverse osmosis membrane devices 80S via the primary treated liquid suction line
56. Backward passing liquid sluice valves 64 are respectively installed on the backward
passing liquid lines 54.
Differential pressure gauges 89 are respectively provided for the plurality of
primary reverse osmosis membrane devices 80S. Each of the differential pressure gauges
15 89 detects a pressure difference P between a pressure of the liquid-to-be-treated branch
line 52b at a position closer to the primary reverse osmosis membrane device 80S than the
liquid-to-be-treated inflow sluice valve 61 and a pressure of the primary treated liquid
branch line 56b at a position closer to the primary reverse osmosis membrane device 80S
than a position at which the backward passing liquid line 54 is connected.
20 As in the first embodiment, a backwashing liquid line 42 of a backwashing device
40 has a backwashing liquid main line 42m that is connected to a backwashing liquid tank
41, and backwashing liquid branch lines 42b that branch off from the backwashing liquid
main line 42m to the plurality of respective primary reverse osmosis membrane devices
80S. Backwashing liquid sluice valves 46 are respectively installed on the backwashing
25 liquid branch lines 42b.
As in the first embodiment, a disinfectant line 22 of a disinfectant feeder 20 has a
disinfectant main line 22m that is connected to a disinfectant tank 21 and disinfectant
branch lines 22b that branch off from the disinfectant main line 22m. However, the
disinfectant branch lines 22b in the present embodiment are connected to the
30 corresponding backward passing liquid lines 54. A disinfectant pump 25 and a
disinfectant sluice valve 26 are installed on the disinfectant main line 22m. Disinfectant
36
flow control valves 27 are respectively installed on the disinfectant branch lines 22b.
As in the first embodiment, an acidic agent line 32 of an acidic agent feeder 30 of
the present embodiment has an acidic agent main line 32m that is connected to an acidic
agent tank 31, and acidic agent branch lines 32b that branch off from the acidic agent main
line 32m. However, the acidic agent branch 5 lines 32b in the present embodiment are
connected to the corresponding backward passing liquid lines 54. An acidic agent pump
35 and an acidic agent sluice valve 36 are installed on the acidic agent main line 32m.
Acidic agent flow control valves 37 are respectively installed on the acidic agent branch
lines 32b.
10 In the present embodiment, a bypass-switching device is made up of the
liquid-to-be-treated inflow sluice valves 61, the primary treated liquid sluice valves 62, and
a bypass sluice valve 65. A backwashing-switching device is made up of the
liquid-to-be-treated inflow sluice valves 61, the primary treated liquid sluice valves 62, the
backward passing liquid sluice valves 64, the backwashing liquid sluice valves 46, and the
15 cleaning liquid sluice valves 63.
As in the first embodiment, in a normal operation state of the present embodiment,
as illustrated in Fig. 7, the liquid-to-be-treated inflow sluice valves 61 and the primary
treated liquid sluice valves 62 are opened. As in the first embodiment, in this normal
operation state, the disinfectant sluice valve 26, the disinfectant flow control valves 27, the
20 acidic agent sluice valve 36, the acidic agent flow control valves 37, the backwashing
liquid sluice valves 46, the cleaning liquid sluice valves 63, and the bypass sluice valve 65
are closed. Further, in the normal operation state of the present embodiment, the
backward passing liquid sluice valves 64 are closed.
For this reason, in the normal operation state of the present embodiment, as in the
25 first embodiment, the seawater SW pumped by the primary water feed pump 11 flows from
the liquid-to-be-treated inflow ports 82s of the primary reverse osmosis membrane devices
80S into the primary liquid-passing parts 91s of the primary reverse osmosis membrane
devices 80S via a strainer 12, a cartridge filter 13, the liquid-to-be-treated discharge main
line 52m, and the plurality of liquid-to-be-treated branch lines 52b. The seawater SW
30 passes through the primary liquid-passing parts 91s without driving reverse osmosis across
37
the primary reverse osmosis membranes 86s and flows from the primary treated liquid
outflow ports 83s of the primary reverse osmosis membrane devices 80S to the primary
treated liquid branch lines 56b as the primary treated liquid W1.
Therefore, even in the present embodiment, as in the first embodiment, foreign
materials that can be deposited on secondary liquid-passing parts 5 91m of secondary reverse
osmosis membrane devices 80M can be trapped by the primary reverse osmosis membrane
devices 80S.
As in the first embodiment, the primary treated liquid W1 flowing to the primary
treated liquid branch lines 56b merges at the primary treated liquid suction main line 56m
10 and is fed into the secondary liquid-passing parts 91m of the plurality of secondary reverse
osmosis membrane devices 80M of the secondary treatment system 70 by the secondary
water feed pump 71 at a pressure exceeding an osmotic pressure of the primary treated
liquid W1.
Even in the present embodiment, when a pressure difference P detected by any
15 one of the plurality of differential pressure gauges 89 is equal to or higher than a preset
value, the controller 1 outputs, as illustrated in Fig. 8, an opening instruction to the
backwashing liquid sluice valve 46, the cleaning liquid sluice valve 63, and the backward
passing liquid sluice valve 64 which correspond to the one primary reverse osmosis
membrane device 80S, at which the pressure difference P is detected by the differential
20 pressure gauge 89, and a closing instruction to the liquid-to-be-treated inflow sluice valve
61 and the primary treated liquid sluice valve 62 (a backwashing-switching process). As
described above, the backwashing-switching device is made up of the liquid-to-be-treated
inflow sluice valves 61, the primary treated liquid sluice valves 62, the backward passing
liquid sluice valves 64, the backwashing liquid sluice valves 46, and the cleaning liquid
25 sluice valves 63.
To be specific, the controller 1 outputs the opening instruction to the cleaning
liquid sluice valve 63 and the closing instruction to the primary treated liquid sluice valve
62 first. Next, the controller 1 outputs the opening instruction to the backwashing liquid
sluice valve 46. The controller 1 outputs the opening instruction to the backward passing
30 liquid sluice valve 64 and the closing instruction to the liquid-to-be-treated inflow sluice
38
valve 61.
As a result, part of the seawater SW flows from the primary treated liquid outflow
port 83s of the one primary reverse osmosis membrane device 80S into the primary
liquid-passing part 91s of the one primary reverse osmosis membrane device 80S via the
liquid-to-be-treated discharge line 52, the backward 5 passing liquid line 54 corresponding to
the one primary reverse osmosis membrane device 80S, and the primary treated liquid
suction line 56. The seawater SW flowing into the primary liquid-passing part 91s is
discharged from the liquid-to-be-treated inflow port 82s of the one primary reverse
osmosis membrane device 80S to the outside via the primary treated liquid suction line 56,
10 the cleaning liquid discharge line 58a, and the cleaning liquid sluice valve 63. A
backwashing liquid BW (freshwater) in the backwashing tank flows from the permeated
liquid outflow port 84s of the one primary reverse osmosis membrane device 80S into the
primary permeating part 92s via the backwashing liquid main line 42m, the backwashing
liquid branch line 42b connected to the one primary reverse osmosis membrane device 80S,
15 and the backwashing liquid sluice valve 46 installed on the backwashing liquid branch line
42b. As in the first embodiment, the backwashing liquid BW in the primary permeating
part 92s drives forward osmosis across the primary reverse osmosis membrane 86s and
flows into the primary liquid-passing part 91s. In this process, foreign materials adhered
to a mesh spacer 88 for securing a flow path in the primary liquid-passing part 91s or a side
20 of the primary liquid-passing part 91s of the primary reverse osmosis membrane 86s are
stripped from the mesh spacer 88 or the primary reverse osmosis membrane 86s. These
foreign materials are discharged from the liquid-to-be-treated inflow port 82s of the one
primary reverse osmosis membrane device 80S to the outside via the liquid-to-be-treated
branch line 52b, the cleaning liquid discharge line 58a, and the cleaning liquid sluice valve
25 63 along with the backwashing liquid BW and the seawater SW in the primary
liquid-passing part 91s. That is, an operation state of the one primary reverse osmosis
membrane device 80S becomes a backwashing state, and this primary reverse osmosis
membrane device 80S is backwashed by the backwashing liquid BW (a backwashing
process).
30 As in the first embodiment, the primary treated liquid W1 flowing out of the
primary reverse osmosis membrane devices 80S excluding the one primary reverse
osmosis membrane device 80S merges at the primary treated liquid suction main line 56m
39
via the primary treated liquid branch line 56b and is fed into the secondary liquid-passing
parts 91m of the plurality of secondary reverse osmosis membrane devices 80M of the
secondary treatment system 70 by the secondary water feed pump 71 at a pressure
exceeding the osmotic pressure of the primary treated liquid W1. Therefore, even if the
one primary reverse osmosis membrane device 80S 5 is backwashed, the primary reverse
osmosis membrane device 80S excluding the one primary reverse osmosis membrane
device 80S is maintained in the normal operation state, and a desalinization treatment of
the seawater SW in the water treatment device is continued.
In the present embodiment, a flow of liquid in the primary liquid-passing parts 91s
10 in the backwashing state is a flow from the primary treated liquid outflow ports 83s side to
the liquid-to-be-treated inflow ports 82s side and has an opposite direction of the flow of
the first embodiment. In the primary reverse osmosis membrane devices 80S, many
foreign materials are trapped at upstream portions in the primary liquid-passing parts 91s,
in other words, at portions of the liquid-to-be-treated inflow ports 82s side in the primary
15 liquid-passing parts 91s. The many foreign materials are deposited on these portions.
For this reason, in the present embodiment, the foreign materials deposited on the primary
liquid-passing parts 91s can be more efficiently removed than in the first embodiment.
When the backwashing described above is performed, for example, for a given
time, the controller 1 outputs the opening instruction to the liquid-to-be-treated inflow
20 sluice valves 61 and the primary treated liquid sluice valves 62 and the closing instruction
to the backwashing liquid sluice valves 46, the cleaning liquid sluice valves 63, and the
backward passing liquid sluice valves 64. As a result, as illustrated in Fig. 7, the
operation state of the one primary reverse osmosis membrane device 80S returns to the
normal operation state.
25 Even when the one primary reverse osmosis membrane device 80S is backwashed,
if the pressure difference P between the pressure of the seawater SW flowing into the
primary liquid-passing part 91s of the primary reverse osmosis membrane device 80S and
the pressure of the primary treated liquid W1 flowing out of the primary liquid-passing part
91s is reduced in the normal operation state, the controller 1 outputs, as in the first
30 embodiment, the opening instruction to the disinfectant sluice valve 26 and the disinfectant
flow control valve 27 corresponding to the one primary reverse osmosis membrane device
40
80S and a driving instruction to the disinfectant pump 25. Further, like the
backwashing-switching process that switches from the normal operation state to the
backwashing state, the controller 1 outputs the opening instruction to the backwashing
liquid sluice valve 46, the cleaning liquid sluice valve 63, and the backward passing liquid
sluice valve 64 and the closing instruction to the liquid-5 to-be-treated inflow sluice valve 61
and the primary treated liquid sluice valve 62. As a result, the disinfectant in the
disinfectant tank 21 flows from the primary treated liquid outflow port 83s of the one
primary reverse osmosis membrane device 80S into the primary liquid-passing part 91s via
the disinfectant branch line 22b, the backward passing liquid line 54, and the primary
10 treated liquid branch line 56b.
In the present embodiment, a flow of the liquid in the primary liquid-passing parts
91s in a disinfecting state is a flow from the primary treated liquid outflow ports 83s side
to the liquid-to-be-treated inflow ports 82s side and has an opposite direction of the flow of
the first embodiment. For this reason, organisms such as fungi adhered to the primary
15 liquid-passing parts 91s can be more efficiently removed than in the first embodiment.
In the present embodiment, like the above disinfecting treatment, the acidic agent
feeder 30 is driven to dissolve an inorganic scale component of the primary reverse
osmosis membrane devices 80S.
Even in the present embodiment, for example, an operator of the water treatment
20 device instructs the controller 1 to switch the operation state of each of the primary reverse
osmosis membrane devices 80S from the normal operation state to a bypass operation
state.
As in the first embodiment, as illustrated in Fig. 9, when the controller 1 receives
a switching instruction, the controller 1 outputs the closing instruction to the plurality of
25 liquid-to-be-treated inflow sluice valves 61 and the plurality of primary treated liquid
sluice valves 62 which constitute a part of the bypass-switching device and the opening
instruction to the bypass sluice valve 65 which constitutes a part of the bypass-switching
device (a bypass-switching process). As described above, the bypass-switching device is
made up of the liquid-to-be-treated inflow sluice valves 61, the primary treated liquid
30 sluice valves 62, and the bypass sluice valve 65.
41
As a result, the seawater SW from the liquid-to-be-treated discharge main line
52m does not flow into all of the primary reverse osmosis membrane devices 80S via the
respective liquid-to-be-treated branch lines 52b and flows into the secondary water feed
pump 71 via the bypass line 59 and the primary treated liquid suction main line 56m (a
5 bypass-operating process).
The seawater SW flowing into the secondary water feed pump 71 is fed into the
secondary liquid-passing parts 91m of the plurality of secondary reverse osmosis
membrane devices 80M of the secondary treatment system 70 by the secondary water feed
pump 71 at a pressure exceeding an osmotic pressure of the seawater SW and is treated by
10 the plurality of secondary reverse osmosis membrane devices 80M similarly as above.
In the bypass operation state, which is a running operation state of the
bypass-operating process, as in the first embodiment, the seawater SW does not flow into
all of the primary reverse osmosis membrane devices 80S. For this reason, in the bypass
operation state, a task of, for example, replacing each of the primary reverse osmosis
15 membrane devices 80S with another primary reverse osmosis membrane device 80S or
overhauling each of the primary reverse osmosis membrane devices 80S is performed.
As described above, in the present embodiment, the same effects as the first
embodiment are obtained. Further, in the present embodiment, foreign materials inside
the primary liquid-passing parts 91s of the primary reverse osmosis membrane devices 80S
20 can be more efficiently removed than in the first embodiment.
(Modification)
In each of the above embodiments, the plurality of primary reverse osmosis
membrane devices 80S are provided. However, the number of primary reverse osmosis
membrane devices 80S may be one. Even in this case, the bypass-operating process is
25 performed while the desalinization treatment of the seawater SW is performed by the
plurality of secondary reverse osmosis membrane devices 80M, and thereby the primary
reverse osmosis membrane devices 80S can be, for example, replaced with other primary
reverse osmosis membrane devices 80S.
In each of the above embodiments, both the primary reverse osmosis membrane
42
devices 80S and the secondary reverse osmosis membrane devices 80M are spiral type
reverse osmosis membrane devices. However, the reverse osmosis membrane devices
may not be a spiral type, and may, for example, be various types such as, for example, a
hollow fiber type, a tubular type, and the like. In each of the above embodiments, the
primary reverse osmosis membrane devices 80S 5 and the secondary reverse osmosis
membrane devices 80M are the same type of reverse osmosis membrane device.
However, the primary reverse osmosis membrane devices 80S and the secondary reverse
osmosis membrane devices 80M may be different types of reverse osmosis membrane
device. However, it is preferable that the primary reverse osmosis membrane devices 80S
10 and the secondary reverse osmosis membrane devices 80M be the same type so as to
enhance the trapping characteristic of foreign materials that can be deposited on the
secondary liquid-passing parts 91m of the secondary reverse osmosis membrane devices
80M and be trapped by the primary reverse osmosis membrane devices 80S.
The backwashing-switching device of the first embodiment is made up of the
15 primary treated liquid sluice valves 62, the backwashing liquid sluice valves 46, and the
cleaning liquid sluice valves 63. However, the backwashing-switching device may not
use the above three kinds of sluice valve. For example, in place of the primary treated
liquid sluice valves 62 and the cleaning liquid sluice valves 63, three-way valves having
functions of these sluice valves may be used. Moreover, the backwashing-switching
20 device of the second embodiment is made up of the liquid-to-be-treated inflow sluice
valves 61, the primary treated liquid sluice valves 62, the backward passing liquid sluice
valves 64, the backwashing liquid sluice valves 46, and the cleaning liquid sluice valves 63.
However, the backwashing-switching device may not use the above five kinds of sluice
valve. For example, in place of the liquid-to-be-treated inflow sluice valves 61 and the
25 cleaning liquid sluice valves 63, three-way valves having functions of these sluice valves
may be used. In place of the primary treated liquid sluice valves 62 and the backward
passing liquid sluice valves 64, three-way valves having functions of these sluice valves
may be used.
The bypass-switching device of each of the above embodiments is made up of the
30 liquid-to-be-treated inflow sluice valves 61, the primary treated liquid sluice valves 62, and
the bypass sluice valve 65. However, for example, when there is only one primary
reverse osmosis membrane device 80S, three-way valves having functions of these sluice
43
valves may be used in place of the liquid-to-be-treated inflow sluice valves 61 and the
bypass sluice valve 65. For example, when there is only one primary reverse osmosis
membrane device 80S, three-way valves having functions of these sluice valves may be
used in place of the primary treated liquid sluice valves 62, and the bypass sluice valve 65.
In each of the above embodiments, when a 5 pressure difference P between
upstream and downstream sides of each of the primary liquid-passing parts 91s is equal to
or higher than a preset value, switching from the normal operation state to the backwashing
state is performed. However, the switching from the normal operation state to the
backwashing state may be adapted to be periodically performed.
10 In each of the above embodiments, freshwater, which is the permeated liquid PW
flowing out of the secondary reverse osmosis membrane devices 80M of the secondary
treatment system 70, is used as the backwashing liquid BW. However, freshwater may
not be used as the backwashing liquid BW for backwashing the primary reverse osmosis
membrane devices 80S if there is water having a lower concentration of a solute (salt) than
15 the seawater SW, which is the liquid to be treated. For example, water in which the solute
(salt) is mixed somewhat may be used.
In the primary treatment systems of the above embodiments, the acidic agent
feeder and the disinfectant feeder are provided. However, in the primary treatment
systems, the acidic agent feeder and the disinfectant feeder may not be provided. The
20 acidic agent feeder may be provided, for example, for the secondary treatment system only.
In the secondary treatment systems of the above embodiments, the acidic agent feeder, the
disinfectant feeder, and the backwashing device are not provided, but these devices may be
provided for the secondary treatment systems. When the acidic agent feeder is provided
for either of the treatment systems, a reductant feeder may be provided to neutralize a
25 liquid acidified by the acidic agent being fed thereto. The disinfecting treatment and the
dissolving treatment of an inorganic scale component may be performed on the secondary
reverse osmosis membrane devices 80M of the secondary treatment system by the acidic
agent feeder and the disinfectant feeder provided for the above primary treatment system.
In this case, the acidic agent and the disinfectant are fed to the secondary reverse osmosis
30 membrane devices 80M via the primary treated liquid line 55 or both the backward passing
liquid lines 54 and the primary treated liquid line 55. The reverse osmosis membrane
44
devices located downstream in the flow of the liquid to be treated tend to have a larger
amount of deposition of inorganic scale than the reverse osmosis membrane devices
located upstream in the flow of the liquid to be treated. For this reason, a mode in which
the acidic agent feeder can positively feed the acidic agent to the secondary liquid-passing
parts 91m of the downstream secondary reverse 5 osmosis membrane devices 80M is more
preferable than a mode in which the acidic agent feeder feeds the acidic agent to the
primary liquid-passing parts 91s of the upstream primary reverse osmosis membrane
devices 80S.
The primary water feed pump 11 of each of the above embodiments feeds a liquid
10 to be treated to the primary reverse osmosis membrane devices at a pressure equal to or
lower than the osmotic pressure of the liquid to be treated. However, the primary water
feed pump may feed the liquid to be treated to the primary reverse osmosis membrane
devices at a higher pressure than the osmotic pressure of the liquid to be treated. In this
case, the permeated liquid passing through the primary reverse osmosis membranes is
15 adapted to be fed to the secondary reverse osmosis membrane devices via the secondary
water feed pump.
In the above embodiments, the seawater SW is fed to the primary reverse osmosis
membrane devices 80S via the strainer 12, the primary water feed pump 11, and the
cartridge filter 13. However, for example, various devices may be further added to the
20 primary treatment system. For example, a sand filter may be provided between the
strainer 12 and the primary water feed pump 11. Conversely, the cartridge filter 13 or the
like may be omitted from the primary treatment system. An order of installation of the
strainer 12, the primary water feed pump 11, the cartridge filter 13, the sand filter provided
as needed, etc. may be appropriately changed. To be specific, for example, the primary
25 water feed pump 11 may be disposed upstream of the strainer 12.
Industrial Applicability
In an aspect of the present invention, water treatment can be continued over a long
period of time.

We Claim:
1. A water treatment device, comprising:
a primary reverse osmosis membrane device having a primary casing and
a primary reverse osmosis membrane dividing an inside of the primary casing into
a primary liquid-passing 5 part and a primary permeating part;
a liquid-to-be-treated line configured to feed a liquid to be treated, which
is a treatment target, to the primary liquid-passing part;
a primary water feeder configured to feed the liquid to be treated to the
primary liquid-passing part under pressure via the liquid-to-be-treated line;
10 a secondary reverse osmosis membrane device having a secondary casing
and a secondary reverse osmosis membrane dividing an inside of the secondary
casing into a secondary liquid-passing part and a secondary permeating part;
a primary treated liquid line configured to feed a primary treated liquid,
which is obtained by the liquid to be treated passing through the primary reverse
15 osmosis membrane device, to the secondary liquid-passing part;
a secondary water feeder installed on the primary treated liquid line and
configured to feed the primary treated liquid to the secondary permeating part at a
pressure higher than an osmotic pressure of the primary treated liquid;
a bypass line configured to connect the liquid-to-be-treated line and a
20 position on the primary treated liquid line, which is located between the primary
reverse osmosis membrane device and the secondary water feeder, and cause the
liquid to be treated to bypass the primary reverse osmosis membrane device; and
a bypass-switching device configured to convert an operation state
including a normal operation state, in which the liquid to be treated is fed from the
25 liquid-to-be-treated line to the primary liquid-passing part of the primary reverse
osmosis membrane device and the primary treated liquid is fed from the primary
reverse osmosis membrane device to the secondary water feeder, to a bypass
operation state in which the liquid to be treated is fed from the liquid-to-be-treated
49
line to the secondary water feeder via the bypass line.
2. The water treatment device according to Claim 1, wherein:
the primary water feeder is a water feeder that feeds the liquid to be
treated to the primary liquid-passing part at a pressure lower than or equal to an
5 osmotic pressure of the liquid to be treated; and
the primary treated liquid line is connected to the primary liquid-passing
part side of the primary casing, and is connected to the secondary liquid-passing
part side of the secondary casing.
3. The water treatment device according to Claim 2, wherein:
10 the primary casing is formed with a liquid-to-be-treated inflow port and a
primary treated liquid outflow port, which communicate the primary
liquid-passing part and an outside with each other, and a permeated liquid outflow
port which communicates the primary permeating part and the outside with each
other; and
15 the liquid-to-be-treated line is connected to the liquid-to-be-treated
inflow port, and the primary treated liquid line is connected to the primary treated
liquid outflow port.
4. The water treatment device according to Claim 3, further comprising:
a backwashing device configured to feed a backwashing liquid, a solute
20 concentration of which is lower than that of the liquid to be treated, from the
permeated liquid outflow port to the primary permeating part; and
a cleaning liquid discharge line configured to discharge a liquid
containing the backwashing liquid, which is fed to the primary permeating part,
passes through the primary reverse osmosis membrane, and reaches the primary
25 liquid-passing part, to the outside via the liquid-to-be-treated line or the primary
treated liquid line.
5. The water treatment device according to Claim 4, further comprising a
50
backwashing-switching device configured to switch the operation state between
the normal operation state, in which the liquid to be treated is fed from the
liquid-to-be-treated line into the primary liquid-passing part via the
liquid-to-be-treated inflow port and the primary treated liquid fed from the
primary liquid-passing part is fed to the secondary 5 water feeder via the primary
treated liquid line, and a backwashing state, in which the liquid containing the
backwashing liquid, which is fed from the backwashing device to the primary
permeating part and reaches the primary liquid-passing part via the primary
reverse osmosis membrane, is discharged from the cleaning liquid discharge line
10 to the outside via the liquid-to-be-treated line or the primary treated liquid line.
6. The water treatment device according to Claim 5, wherein:
the cleaning liquid discharge line is connected to the liquid-to-be-treated
line;
the water treatment device includes a backward passing liquid line that
15 connects the liquid-to-be-treated line and the primary treated liquid line and
guides the liquid to be treated passing through the liquid-to-be-treated line from
the primary treated liquid outflow port to the primary liquid-passing part via the
primary treated liquid line;
the cleaning liquid discharge line is connected to the liquid-to-be-treated
20 line at a position closer to the liquid-to-be-treated inflow port side than a position
at which the backward passing liquid line is connected; and
the backwashing-switching device switches the operation state between
the normal operation state and the backwashing state, in which the backwashing
liquid from the backwashing device is fed to the primary permeating part, the
25 liquid to be treated is fed from the liquid-to-be-treated line into the primary
liquid-passing part via the backward passing liquid line, the primary treated liquid
line, and the primary treated liquid outflow port, and the liquid to be treated and
the backwashing liquid flowing out of the liquid-to-be-treated inflow port are
discharged from the cleaning liquid discharge line to the outside.
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7. The water treatment device according to Claim 5 or 6, further comprising:
a differential pressure gauge configured to detect a pressure difference
between a pressure in the liquid-to-be-treated line and a pressure in the primary
treated liquid line at a position closer to the primary reverse osmosis membrane
device side tha 5 n the secondary water feeder; and
a controller configured to instruct the backwashing-switching device to
switch the operation state from the normal operation state to the backwashing
state when the pressure difference detected by the differential pressure gauge in
the normal operation state is equal to or higher than a preset value.
10 8. The water treatment device according to any one of Claims 3 to 7, further
comprising a plurality of primary reverse osmosis membrane devices, inclusive of
the primary reverse osmosis membrane device,
wherein the liquid-to-be-treated line has a liquid-to-be-treated main line
that is connected to the primary water feeder, and liquid-to-be-treated branch lines
15 that branch off from the liquid-to-be-treated main line to the plurality of
respective primary reverse osmosis membrane devices and are connected to the
liquid-to-be-treated inflow ports of the respective primary reverse osmosis
membrane devices, and
the primary treated liquid line has a primary treated liquid main line that
20 is connected to the secondary water feeder, and primary treated liquid branch lines
that branch off from the primary treated liquid main line to respective primary
reverse osmosis membrane devices and are connected to the primary treated liquid
outflow ports of the respective primary reverse osmosis membrane devices, and
the bypass line causes the liquid to be treated from the primary water
25 feeder to bypass all of the plurality of primary reverse osmosis membrane devices.
9. The water treatment device according to any one of Claims 1 to 8, wherein the
primary reverse osmosis membrane device and the secondary reverse osmosis
membrane device are the same type of reverse osmosis membrane device.
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10. A method for operating a water treatment device including a plurality of reverse
osmosis membrane devices, each of which has a casing and a reverse osmosis
membrane dividing an inside of the casing into a liquid-passing part and a
permeating part, wherein the casing is formed with first and second ports that
communicate the liquid-passing part and an 5 outside with each other, and a third
port that communicates the permeating part and the outside with each other, the
method comprising:
a normal operating process which sets at least one of the plurality of
reverse osmosis membrane devices as a primary reverse osmosis membrane
10 device and the remaining reverse osmosis membrane devices as secondary reverse
osmosis membrane devices, and which feeds a liquid to be treated, which is a
treatment target, from the first port of the primary reverse osmosis membrane
device into the liquid-passing part under pressure, and feeding a liquid, which is
obtained by the liquid to be treated passing through the primary reverse osmosis
15 membrane device, from the first ports of the secondary reverse osmosis membrane
devices into the liquid-passing parts of the secondary reverse osmosis membrane
devices as a primary treated liquid at a pressure higher than an osmotic pressure of
the primary treated liquid;
a bypass-operating process of causing the liquid to be treated to bypass
20 the primary reverse osmosis membrane device, and feeding the liquid to be treated
from the first ports of the secondary reverse osmosis membrane devices into the
liquid-passing parts of the secondary reverse osmosis membrane devices at a
pressure higher than an osmotic pressure of the liquid to be treated; and
a bypass-switching process of converting an operation state including a
25 normal operation state, which is a running operation state of the normal operating
process, to a bypass operation state, which is a running operation state of the
bypass-operating process.
11. The method according to Claim 10, wherein the normal operating process
includes feeding the liquid to be treated from the first port of the primary reverse
30 osmosis membrane device into the liquid-passing part at a pressure equal to or
53
lower than the osmotic pressure of the liquid to be treated, and feeding the liquid,
which is obtained by the liquid to be treated passing through the primary
liquid-passing part and being discharged from the second port, from the first ports
of the secondary reverse osmosis membrane devices into the liquid-passing parts
5 as the primary treated liquid.
12. The method according to Claim 11, further comprising a backwashing process of
feeding a backwashing liquid, a solute concentration of which is lower than that of
the liquid to be treated, from the third port of the primary reverse osmosis
membrane device to the permeating part, and discharging a liquid containing the
10 backwashing liquid, which passes through the reverse osmosis membrane of the
primary reverse osmosis membrane device and reaches the liquid-passing part, to
the outside.
13. The method according to Claim 12, wherein the backwashing process includes
feeding the liquid to be treated from the second port of the primary reverse
15 osmosis membrane device into the liquid-passing part, and discharging the liquid
to be treated to the outside via the first port of the primary reverse osmosis
membrane device along with the backwashing liquid that reaches the
liquid-passing part of the primary reverse osmosis membrane device.
14. The method according to Claim 12 or 13, further comprising a
20 backwashing-switching process of switching the operation state between the
normal operation state and a backwashing state, which is a running operation state
of the backwashing process.
15. The method according to any one of Claims 12 to 14, wherein:
the water treatment device includes a plurality of primary reverse
25 osmosis membrane devices, inclusive of the primary reverse osmosis membrane
device;
the water treatment device performs the normal operation state in which,
when the backwashing process is performed on a first sub-device group of at least
one of the plurality of primary reverse osmosis membrane devices, the liquid to be
54
treated is fed into the liquid-passing part via first ports of a second sub-device
group made up of the other primary reverse osmosis membrane devices, and the
primary treated liquid from the liquid-passing part is fed to the secondary reverse
osmosis membrane devices under pressure; and
the bypass-operating process includes causing 5 the liquid to be treated to
bypass all of the plurality of primary reverse osmosis membrane devices.