Description
Technical Field
The present invention relates to a water quality monitoring device, a water
treatment device, a water treatment system, a water quality monitoring method, and a
program5 .
Background Art
Reverse osmosis membranes used in seawater desalination plants are degraded by
turbidity components, organic matter, and other fouling substances contained in seawater
that is supplied to the reverse osmosis membranes. To prevent degradation of the reverse
10 osmosis membrane, a sand filtration device, a dual media filter (DMF), a ceramic membrane
filter (CMF), or other pretreatment device is usually provided upstream of the reverse
osmosis membrane. It is also known for a method for preventing degradation of the
reverse osmosis membrane, that monitoring the concentration of fouling substances
contained in water supplied to the reverse osmosis membrane.
15 Patent Literature 1 discloses a technique of measuring the viscosity of water
supplied to a membrane separation device by a torque meter and stopping the supply of
water to the membrane separation device when a value detected by the torque meter is equal
to or greater than a predetermined value.
Citation List
20 Patent Literature
Patent Literature 1
Japanese Patent No. 3132044
3
Summary of Invention
Technical Problem
Most part of fouling substances contained in seawater is treated by the pretreatment
device. Therefore, the amount of fouling substances contained in the water supplied to
the reverse osmosis membrane is about several 100 parts per billion (ppb). A change 5 in
viscosity due to a change in the concentration of fouling substances at several 100 ppb is
from about several tenths of one percent to several percent at most. However, a general
torque meter does not have a resolution capable of detecting changes in viscosity of about
several tenths of one percent to several percent by online measurement in plant
10 environments.
Solution to Problem
According to a first aspect of the present invention, a water quality monitoring
device which monitors water quality in a water treatment device that generates fresh water
using a reverse osmosis membrane includes a speed determination unit which determines
15 a speed of a wave passing through water present upstream of the reverse osmosis
membrane to measure a parameter correlated with a concentration of organic matter in the
water, and a concentration reduction processing unit which reduces the concentration of
organic matter in water present upstream of the reverse osmosis membrane when the speed
determined by the speed determination unit is greater than a predetermined threshold speed.
20 According to a second aspect of the present invention, the water quality monitoring
device according to the first aspect further includes a density determination unit which
determines a density of water present upstream of the reverse osmosis membrane, wherein,
when the speed determined by the speed determination unit is greater than the
predetermined threshold speed and the density determined by the density determination
4
unit is less than a predetermined threshold density, the concentration reduction processing
unit reduces the concentration of organic matter in water present upstream of the reverse
osmosis membrane.
According to a third aspect of the present invention, in the water quality
monitoring device according to the first or second aspect, the concentration reducti5 on
processing unit reduces the concentration of organic matter in water present upstream of
the reverse osmosis membrane using a different method for each range of the speed
determined by the speed determination unit.
According to a fourth aspect of the present invention, in the water quality
10 monitoring device according to any one of the first to third aspects, the concentration
reduction processing unit reduces the concentration of organic matter in water present
upstream of the reverse osmosis membrane by outputting a command to add a flocculant
to a chemical injection device which adds a flocculant to water that is supplied to a
pretreatment device provided upstream of the reverse osmosis membrane.
15 According to a fifth aspect of the present invention, in the water quality monitoring
device according to any one of the first to fourth aspects, the concentration reduction
processing unit reduces the concentration of organic matter in water present upstream of
the reverse osmosis membrane by activating a backwash device which backwashes a
pretreatment device provided upstream of the reverse osmosis membrane.
20 According to a sixth aspect of the present invention, the water quality monitoring
device according to the second aspect further includes a concentration determination unit
which determines a parameter correlated with a concentration of organic matter and a
parameter correlated with a concentration of inorganic microparticles on the basis of the
speed determined by the speed determination unit and the density determined by the
5
density determination unit, wherein the concentration reduction processing unit reduces
the concentration of organic matter in water present upstream of the reverse osmosis
membrane when the parameter correlated with the concentration of organic matter
determined by the concentration determination unit is greater than the predetermined
threshold speed and reduces the concentration of inorganic matter in water prese5 nt
upstream of the reverse osmosis membrane when the parameter correlated with the
concentration of inorganic matter determined by the concentration determination unit is
greater than the predetermined threshold speed.
According to a seventh aspect of the present invention, a water quality monitoring
10 device which monitors water quality in a water treatment device that generates fresh water
using a reverse osmosis membrane includes a speed determination unit which determines
a speed of a wave passing through water present upstream of the reverse osmosis
membrane to measure a parameter correlated with a concentration of organic matter in the
water, and a presentation unit which presents the parameter correlated with the speed
15 determined by the speed determination unit.
According to an eighth aspect of the present invention, the water quality monitoring
device according to the seventh aspect further includes a density determination unit which
determines a density of water present upstream of the reverse osmosis membrane, wherein
the presentation unit presents parameters correlated with the speed and the density.
20 According to a ninth aspect of the present invention, the water quality monitoring
device according to the eighth aspect further includes a concentration determination unit
which determines a parameter correlated with a concentration of organic matter and a
parameter correlated with a concentration of inorganic microparticles on the basis of the
speed determined by the speed determination unit and the density determined by the
6
density determination unit, wherein the presentation unit presents the parameter correlated
with the concentration of organic matter and the parameter correlated with the
concentration of inorganic microparticles.
According to a tenth aspect of the present invention, the water quality monitoring
device according to any one of the first to ninth aspects further includes a stora5 ge
processing unit which stores part of water present upstream of the reverse osmosis
membrane in a predetermined container when the speed determined by the speed
determination unit is greater than the predetermined threshold speed.
According to an eleventh aspect of the present invention, in the water quality
10 monitoring device according to any one of the first to tenth aspects, the speed
determination unit determines a speed of a wave passing through water before the water
passes through a pretreatment device provided upstream of the reverse osmosis membrane
and a speed of a wave passing through water after the water passes through the
pretreatment device.
15 According to a twelfth aspect of the present invention, a water treatment device
includes a reverse osmosis membrane, a wave transmitter which is provided upstream of
the reverse osmosis membrane and which generates a wave in water present upstream of
the reverse osmosis membrane, and a wave receiver which is provided upstream of the
reverse osmosis membrane and which detects the wave generated by the wave transmitter.
20 According to a thirteenth aspect of the present invention, the water treatment device
according to the twelfth aspect further includes a vibration tube through which water
present upstream of the reverse osmosis membrane flows, an oscillator which vibrates the
vibration tube, and a vibration detector which detects a vibrational amplitude of the
vibration tube, wherein the wave transmitter and the wave receiver are provided on the
7
vibration tube.
According to a fourteenth aspect of the present invention, a water treatment system
includes the water treatment device according to the twelfth or thirteenth aspect, and the
water quality monitoring device according to any one of the first to eleventh aspects.
According to a fifteenth aspect of the present invention, a water quality 5 monitoring
method includes a speed determining step including determining a speed of a wave passing
through water present upstream of a reverse osmosis membrane, and a concentration
reduction step including reducing a concentration of organic matter in water present
upstream of the reverse osmosis membrane when the determined speed is greater than a
10 predetermined threshold speed.
According to a sixteenth aspect of the present invention, a program causes a
computer for a water quality monitoring device, which monitors water quality in a water
treatment device that generates fresh water using a reverse osmosis membrane, to function
as a speed determination unit which determines a speed of a wave passing through water
15 present upstream of the reverse osmosis membrane to measure a parameter correlated with
a concentration of organic matter in the water, and a concentration reduction processing
unit which reduces the concentration of organic matter in water present upstream of the
reverse osmosis membrane when the speed determined by the speed determination unit is
greater than a predetermined threshold speed.
20 According to a seventeenth aspect of the present invention, a program causes a
computer for a water quality monitoring device, which monitors water quality in a water
treatment device that generates fresh water using a reverse osmosis membrane, to function
as a speed determination unit which determines a speed of a wave passing through water
present upstream of the reverse osmosis membrane to measure a parameter correlated with
8
a concentration of organic matter in the water, and a presentation unit which presents the
parameter correlated with the speed determined by the speed determination unit.
Advantageous Effects of Invention
According to at least one of the above aspects, the water quality monitoring device
measures the speed of a wave generated in water present upstream of the reverse osmo5 sis
membrane. The speed of the wave propagating in the water has a correlation with the
viscosity of the water. The speed of the wave is determined by a period of time during
which the wave propagates. Therefore, since it is possible to improve the temporal
resolution, it is possible to improve the detection accuracy of the wave speed. This
10 allows the water quality monitoring device to detect changes in the concentration of
fouling substances at several 100 ppb.
Brief Description of Drawings
Fig. 1 is a schematic diagram showing a configuration of a seawater treatment
system according to a first embodiment.
15 Fig. 2 is a cross-sectional view showing a structure of a measurement device
according to the first embodiment.
Fig. 3 is a schematic block diagram showing a configuration of a water quality
monitoring device according to the first embodiment.
Fig. 4 is a flowchart showing a sequence of a water quality monitoring process
20 according to the first embodiment.
Fig. 5 is a schematic diagram showing a configuration of a seawater treatment
system according to a second embodiment.
Fig. 6 is a flowchart showing a sequence of a water quality monitoring process
according to the second embodiment.
9
Fig. 7 is a schematic diagram showing a configuration of a seawater treatment
system according to a third embodiment.
Fig. 8 is a flowchart showing a sequence of a water quality monitoring process
according to the third embodiment.
Fig. 9 is a schematic block diagram showing a configuration of a water qualit5 y
monitoring device according to a fourth embodiment.
Fig. 10 is a flowchart showing a sequence of a water quality monitoring process
according to the fourth embodiment.
Fig. 11 is a schematic block diagram showing a configuration of a water quality
10 monitoring device according to a fifth embodiment.
Fig. 12 is a flowchart showing a sequence of a water quality monitoring process
according to the fifth embodiment.
Fig. 13 is a schematic diagram showing a configuration of a seawater treatment
system according to a sixth embodiment.
15 Fig. 14 is a schematic block diagram showing a configuration of a water quality
monitoring device according to the sixth embodiment.
Fig. 15 is a flowchart showing a sequence of a water quality monitoring process
according to the sixth embodiment.
Fig. 16 is a cross-sectional view showing a structure of a measurement device
20 according to a modified example.
Fig. 17 is a schematic block diagram showing a configuration of a computer
according to at least one of the embodiments.
Description of Embodiments
<>
10
A first embodiment is described below.
Fig. 1 is a schematic diagram showing a configuration of a seawater treatment
system according to the first embodiment. In Fig. 1, solid line arrows represent water
distribution pipes and dashed line arrows represent communication lines.
A seawater treatment system 1 is a system for producing fresh water from seawater5 .
The seawater treatment system 1 includes a water intake device 101, a first water storage
tank 102, a first pump 103, a DMF 104, a chemical injection device 105, a second water
storage tank 106, a second pump 107, a measurement device 108, a reverse osmosis
membrane 109, a third water storage tank 110, and a water quality monitoring device 111.
10 The water intake device 101 takes in seawater from a sea area which is a water
intake target. The water intake device 101 allows the taken-in seawater to be stored in
the first water storage tank 102.
The first pump 103 delivers seawater stored in the first water storage tank 102 to
the DMF 104.
15 The DMF 104 internally has two types of filtration layers. Examples of the
filtration layers include a sand layer and an anthracite layer. The DMF 104 passes
seawater delivered by the first pump 103 through the internal filtration layers to filter the
seawater. Seawater filtered by the DMF 104 is then stored in the second water storage
tank 106.
20 The chemical injection device 105 adds a flocculant to the seawater delivered by
the first pump 103.
The second pump 107 delivers seawater stored in the second water storage tank
106 to the reverse osmosis membrane 109. The second pump 107 operates at a higher
pressure than the first pump 103.
11
The measurement device 108 measures the quality of seawater stored in the second
water storage tank 106. The seawater stored in the second water storage tank 106 is water
present upstream of the reverse osmosis membrane 109.
The reverse osmosis membrane 109 passes only water molecules of the seawater
delivered by the second pump 107. Fresh water obtained by filtration through the revers5 e
osmosis membrane 109 is stored in the third water storage tank 110.
The water quality monitoring device 111 controls the chemical injection device 105
on the basis of the quality of seawater supplied to the reverse osmosis membrane 109.
Although the seawater treatment system 1 according to the present embodiment
10 has a configuration shown in Fig. 1, the present invention is not limited to this and the
seawater treatment system 1 may include at least the reverse osmosis membrane 109, the
measurement device 108, and the water quality monitoring device 111. For example, a
seawater treatment system 1 according to another embodiment may include a sand
filtration device, a CMF, or other pretreatment device instead of the DMF 104. A
15 seawater treatment system 1 according to another embodiment may include, for example,
a plurality of reverse osmosis membranes 109 connected in parallel or in series. A
seawater treatment system 1 according to another embodiment may include another
treatment device which reduces the concentration of organic matter in water present
upstream of the reverse osmosis membrane 109, instead of the chemical injection device
20 105. Examples of the treatment device which reduces the concentration of organic matter
in water present upstream of the reverse osmosis membrane 109 include a backwash
device for the DMF 104 and a pressure control device for the second pump 107. A water
treatment system according to another embodiment may generate fresh water from lake
water, dam water, or other water instead of seawater.
12
Fig. 2 is a sectional view showing a structure of a measurement device according
to the first embodiment.
The measurement device 108 includes a housing 201, a partition plate 202, a Ushaped
tube 203, an ultrasonic wave transmitter 204, an ultrasonic wave receiver 205, an
oscillator 206, a vibration detector 207, and a calculator 5 208.
The housing 201 forms an outer shell of the measurement device 108.
The partition plate 202 divides an inner space of the housing 201 into a first
compartment and a second compartment.
The U-shaped tube 203 is provided straddling both the first and second
10 compartments of the housing 201. Two ends of the U-shaped tube 203 protrude outward
from a wall of the first compartment of the housing 201. That is, the U-shaped tube 203
is provided so as to penetrate the partition plate 202 and the wall of the first compartment
of the housing 201. The two ends of the U-shaped tube 203 are attached to a pipe that
connects the second pump 107 and the reverse osmosis membrane 109. This structure
15 allows seawater, which is to be supplied to the reverse osmosis membrane 109, to flow
into the U-shaped tube 203. The U-shaped tube 203 is fixed to the partition plate 202
and the wall of the first compartment of the housing 201 such that the U-shaped tube 203
does not contact top and bottom surfaces of the housing 201. The U-shaped tube 203 is
formed of a highly corrosion-resistant material such as Hastelloy (registered trademark).
20 This can increase the durability of the measurement device 108.
The ultrasonic wave transmitter 204 is fixed to the U-shaped tube 203 in the first
compartment of the housing 201. The ultrasonic wave transmitter 204 emits an ultrasonic
wave toward the U-shaped tube 203.
The ultrasonic wave receiver 205 is provided opposite the ultrasonic wave
13
transmitter 204, across the U-shaped tube 203. The ultrasonic wave receiver 205 receives
the ultrasonic wave generated by the ultrasonic wave transmitter 204 through the U-shaped
tube 203.
The oscillator 206 is fixed to the U-shaped tube 203 in the second compartment of
the housing 201. The oscillator 206 applies vibrations of a predetermined frequency 5 to
the U-shaped tube 203. The oscillator 206 vibrates in a direction perpendicular to a plane
defined by the top and the two ends of the U-shaped tube 203.
The vibration detector 207 is fixed to the U-shaped tube 203 in the second
compartment of the housing 201. The vibration detector 207 detects a vibrational
10 amplitude of the U-shaped tube 203.
The calculator 208 measures a period of time from when the ultrasonic wave
transmitter 204 generates an ultrasonic wave to when the ultrasonic wave receiver 205
receives the ultrasonic wave. The calculator 208 according to the present embodiment
measures the period of time with six or more significant figures accuracy. The calculator
15 208 calculates the sonic speed of the ultrasonic wave on the basis of the period of time
from when the ultrasonic wave transmitter 204 generates the ultrasonic wave to when the
ultrasonic wave receiver 205 receives the ultrasonic wave. The calculator 208 calculates
a resonant frequency of the U-shaped tube 203 on the basis of a relationship between the
frequency of vibration by the oscillator 206 and the vibrational amplitude detected by the
20 vibration detector 207. The calculator 208 calculates the density of water filling the Ushaped
tube 203 on the basis of the resonant frequency of the U-shaped tube 203.
Although the measurement device 108 according to the present embodiment has a
structure shown in Fig. 2, the present invention is not limited to this and the measurement
device 108 may include at least a transmitter that generates a wave and a receiver that
14
receives the wave. For example, a measurement device 108 according to another
embodiment may not include the oscillator 206 and the vibration detector 207. A
measurement device 108 according to another embodiment may include, for example, an
ultrasonic wave transmitter 204 and an ultrasonic wave receiver 205 which are directly
attached to a pipe which connects a second pump 107 and a reverse osmosis membra5 ne
109. A transmitter according to another embodiment may be configured to generate
sound waves, light, or other waves instead of the ultrasonic waves. Although the ultrasonic
wave receiver 205 according to the present embodiment is provided opposite the ultrasonic
wave transmitter 204, the present invention is not limited to this. For example, an
10 ultrasonic wave receiver 205 according to another embodiment may be provided alongside
the ultrasonic wave transmitter 204. In this case, the ultrasonic wave receiver 205
receives the reflection of an ultrasonic wave generated by the ultrasonic wave transmitter
204.
Fig. 3 is a schematic block diagram showing a configuration of a water quality
15 monitoring device according to the first embodiment.
The water quality monitoring device 111 includes a speed determination unit 301,
a viscosity calculation unit 302, a presentation unit 303, an evaluation unit 304, and a
concentration reduction processing unit 305.
The speed determination unit 301 acquires information indicating the speed of the
20 ultrasonic wave from the measurement device 108.
The viscosity calculation unit 302 calculates the viscosity of water which is
supplied to the reverse osmosis membrane 109 on the basis of the information acquired by
the speed determination unit 301.
The presentation unit 303 allows a not-shown display device to display the
15
viscosity calculated by the viscosity calculation unit 302. The presentation unit 303 is an
example of a process execution unit that performs a process based on the speed of the
ultrasonic wave determined by the speed determination unit 301.
The evaluation unit 304 evaluates whether or not the viscosity of water which is
supplied to the reverse osmosis membrane 109 is greater than a predetermined threshol5 d
viscosity on the basis of the viscosity calculated by the viscosity calculation unit 302.
The evaluation unit 304 can detect changes of about several percent in the viscosity. This
is because the measurement device 108 measures the period of time from when an
ultrasonic wave is transmitted to when the ultrasonic wave is received with six or more
10 significant figure accuracy.
The concentration reduction processing unit 305 outputs a command to add a
flocculant to the chemical injection device 105 when the viscosity of water which is
supplied to the reverse osmosis membrane 109 is greater than the predetermined threshold
viscosity. Output of the command to add a flocculant is an example of a process for
15 reducing the concentration of organic matter in water present upstream of the reverse
osmosis membrane 109. A concentration reduction processing unit 305 according to
another embodiment may perform other processes for reducing the concentration of
organic matter in water present upstream of the reverse osmosis membrane 109. Other
processes for reducing the concentration of organic matter in water include a command to
20 increase the amount of a flocculant added, a command to change the type of the flocculant,
a command to backwash the reverse osmosis membrane 109, and the like. The
concentration reduction processing unit 305 is an example of a process execution unit
which performs a process based on the speed of an ultrasonic wave determined by the
speed determination unit 301.
16
It is known that the higher the concentration of fouling substances, the greater the
influence upon fouling of the reverse osmosis membrane 109. Even when the types of
fouling substances in water are the same, the higher the concentration of fouling
substances in water is, the greater the viscosity of water is. It is also known that the
greater the molecular mass of fouling substances, the greater the influence upon fouling o5 f
the reverse osmosis membrane 109. Even when the concentrations of fouling substances
in water are the same, the higher the molecular mass of fouling substances in water, the
greater the viscosity of water. That is, the level of viscosity of water corresponds to the
level of risk of fouling.
10 The viscosity of water is an example of a parameter correlated with the
concentration of organic matter. Other examples of a parameter correlated with the
concentration of organic matter include the speed of an ultrasonic wave, the estimated
concentration of organic matter, and the volume fraction of organic matter.
Although the water quality monitoring device 111 according to the present
15 embodiment has a structure shown in Fig. 3, the present invention is not limited to this.
For example, a presentation unit 303 according to another embodiment may allow the
display device to display the speed of the ultrasonic wave instead of the viscosity. In this
case, the water quality monitoring device 111 may not include the viscosity calculation
unit 302. A presentation unit 303 according to another embodiment may present
20 information using a different presentation method instead of displaying the information on
the display device. Examples of a different presentation method include audio output.
A water quality monitoring device 111 according to another embodiment may not include
the presentation unit 303. Although the evaluation unit 304 according to the present
embodiment evaluates whether or not the viscosity calculated by the viscosity calculation
17
unit 302 is greater than the threshold viscosity, the present invention is not limited to this.
For example, an evaluation unit 304 according to another embodiment may evaluate
whether or not the speed of an ultrasonic wave determined by the speed determination unit
301 is greater than a predetermined threshold speed. Since the speed of an ultrasonic
wave is positively correlated with the viscosity of water, evaluating whether or not 5 the
viscosity of water is greater than the threshold viscosity is equivalent to evaluating whether
or not the speed of an ultrasonic wave is greater than the threshold speed.
A sequence of a water quality monitoring process according to the present
embodiment will now be described.
10 Fig. 4 is a flowchart showing the sequence of the water quality monitoring process
according to the first embodiment.
The water quality monitoring device 111 performs the following water quality
monitoring process at regular intervals. When the water quality monitoring device 111
starts the water quality monitoring process, the speed determination unit 301 acquires
15 information indicating the speed of an ultrasonic wave from the measurement device 108
(step S401). The viscosity calculation unit 302 then calculates the viscosity of water that
is supplied to the reverse osmosis membrane 109 on the basis of the information acquired
by the speed determination unit 301 (step S402). A relationship between the speed of an
ultrasonic wave and the viscosity of water is previously obtained through experiments or
20 simulation. The presentation unit 303 then allows the display device to display the
viscosity calculated by the viscosity calculation unit 302 (step S403).
The evaluation unit 304 evaluates whether or not the viscosity calculated by the
viscosity calculation unit 302 is greater than the predetermined threshold viscosity (step
S404). The threshold viscosity according to the present embodiment is obtained by
18
multiplying an average viscosity of water that is supplied to the reverse osmosis membrane
109 by a factor of 1 or more (for example, 1.1). The threshold viscosity according to
another embodiment may be the viscosity of water which contains organic matter at 100
ppb higher than that of an average quality of water that is supplied to the reverse osmosis
membrane 109. In this case, the threshold viscosity can be determined previously b5 y
obtaining the viscosity of water obtained by dissolving a water-soluble polymer (for
example, polyethylene oxide, xanthan gum, or guar gum) at 100 ppb in water having an
average viscosity.
When the viscosity of water is equal to or less than the predetermined threshold
10 viscosity (step S404: NO), the water quality monitoring device 111 terminates the water
quality monitoring process and waits until the time of execution of a next water quality
monitoring process. On the other hand, when the viscosity of water is greater than the
predetermined threshold viscosity (step S404: YES), the concentration reduction
processing unit 305 outputs a command to add a flocculant to the chemical injection device
15 105 (step S405). The water quality monitoring device 111 then terminates the water
quality monitoring process and waits until the time of execution of a next water quality
monitoring process.
Upon receiving the addition command, the chemical injection device 105 adds a
flocculant to water that is supplied to the DMF 104. Adding the flocculant agglomerates
20 organic substances dissolved in water that is supplied to the DMF 104. The concentration
of organic substances stored in the second water storage tank 106 is reduced since the
agglomerated organic substances are easily filtered out by the DMF 104. This allows the
water quality monitoring device 111 to regulate the quality of water that is supplied to the
reverse osmosis membrane 109, thereby preventing degradation of the reverse osmosis
19
membrane 109.
As described above, according to the present embodiment, the water quality
monitoring device 111 detects changes in the viscosity of water that is supplied to the
reverse osmosis membrane 109 at a resolution of about several tenths of one percent to
several percent. This is because the measurement device 108 measures the period of tim5 e
from when an ultrasonic wave is transmitted to when the ultrasonic wave is received with
six or more significant figure accuracy. In the calculator 208, improving the resolution
of measurement of time is easier than improving the resolution of measurement of
rotational torque. Accordingly, by measuring the speed of an ultrasonic wave as in the
10 present embodiment, it is possible to obtain the viscosity of water easily and with a high
degree of accuracy.
In addition, according to the present embodiment, the measurement device 108
measures a parameter correlated with the viscosity of water without a moving part being
included. This allows the water quality monitoring device 111 to monitor seawater using
15 the measurement device 108 with high durability. Further, according to the present
embodiment, the ultrasonic wave transmitter 204 and the ultrasonic wave receiver 205 are
provided on an outer wall of the U-shaped tube 203. That is, according to the present
embodiment, the water quality monitoring device 111 measures a parameter correlated
with the viscosity of water with the ultrasonic wave transmitter 204 and the ultrasonic
20 wave receiver 205 not directly contacting water. This allows the water quality
monitoring device 111 to monitor seawater using the measurement device 108 with high
durability.
Furthermore, according to the present embodiment, the U-shaped tube 203 of the
measurement device 108 serves as a bypass for the pipe that connects the second pump
20
107 and the reverse osmosis membrane 109. This allows the measurement device 108 to
measure the speed of an ultrasonic wave and the density of water without manual sampling
of water that is supplied to the reverse osmosis membrane 109. This enables the water
quality monitoring device 111 to monitor the viscosity of water that is supplied to the
reverse osmosis membrane 109 in an online manner5 .
<>
A second embodiment is described below.
Fig. 5 is a schematic diagram showing a configuration of a seawater treatment
system according to the second embodiment.
10 The water quality monitoring device 111 of the seawater treatment system 1
according to the first embodiment evaluates whether or not it is necessary to add flocculant
on the basis of the result of measurement by the measurement device 108. On the other
hand, the water quality monitoring device 111 of the seawater treatment system 1
according to the second embodiment evaluates whether or not it is necessary to add a
15 flocculant and whether or not it is necessary to backwash the DMF 104 on the basis of the
result of measurement by the measurement device 108.
The seawater treatment system 1 according to the second embodiment includes a
backwash water tank 501, a backwash pump 502, a first valve 503, and a second valve 504
in addition to the elements of the first embodiment. In addition, the seawater treatment
20 system 1 according to the second embodiment includes not only the measurement device
108 on the pipe between the second pump 107 and the reverse osmosis membrane 109 but
also a measurement device 108 on a pipe between the first pump 103 and the DMF 104.
Concentrated water discharged from the reverse osmosis membrane 109 or
seawater is stored in the backwash water tank 501.
21
The backwash pump 502 backwashes the DMF 104 by delivering water stored in
the backwash water tank 501 to the DMF 104 through a water outlet of the DMF 104.
Water delivered to the DMF 104 by the backwash pump 502 is discharged to the sea or
effluent treatment facilities.
The first valve 503 is provided between the water outlet of the DMF 104 and 5 nd a
water outlet of the backwash pump 502. The first valve 503 is closed during a normal
operation of the seawater treatment system 1 and is opened during backwash treatment.
The second valve 504 is provided between the water outlet of the DMF 104 and a
water inlet of the second water storage tank 106. The second valve 504 is opened during
10 a normal operation of the seawater treatment system 1 and is closed during backwash
treatment.
A sequence of a water quality monitoring process according to the present
embodiment will now be described.
Fig. 6 is a flowchart showing the sequence of the water quality monitoring process
15 according to the second embodiment.
The water quality monitoring device 111 performs the following water quality
monitoring process at regular intervals. When the water quality monitoring device 111
starts the water quality monitoring process, the speed determination unit 301 acquires
information indicating the speed of an ultrasonic wave from each of the measurement
20 device 108 provided on a pipe between the first pump 103 and the DMF 104 and the
measurement device 108 provided on a pipe between the second pump 107 and the reverse
osmosis membrane 109 (step S601).
The viscosity calculation unit 302 then calculates the viscosity of water before
passing through the DMF 104 and the viscosity of water after passing through the DMF
22
104 on the basis of the information acquired by the speed determination unit 301 (step
S602). Specifically, the viscosity calculation unit 302 calculates the viscosity of water
before passing through the DMF 104 on the basis of the speed of an ultrasonic wave
measured by the measurement device 108 provided on the pipe between the first pump
103 and the DMF 104. The viscosity calculation unit 302 also calculates the viscosity 5 of
water after passing through the DMF 104 on the basis of the speed of an ultrasonic wave
measured by the measurement device 108 provided on the pipe between the second pump
107 and the reverse osmosis membrane 109. The presentation unit 303 then allows the
display device to display the viscosities calculated by the viscosity calculation unit 302
10 (step S603).
The evaluation unit 304 calculates the difference between the viscosity of water
before passing through the DMF 104 and the viscosity of water after passing through the
DMF 104 (step S604). The evaluation unit 304 then evaluates whether or not the
calculated viscosity difference is less than a predetermined threshold viscosity difference
15 (step S605). When the difference in viscosity between water before passing through the
DMF 104 and water after passing through the DMF 104 is small, this indicates a reduction
in the organic matter filtration ability of the DMF 104.
When the viscosity difference is less than the threshold viscosity difference (step
S605: YES), the concentration reduction processing unit 305 activates the backwash pump
20 502 after opening the first valve 503 and closing the second valve 504 (step S606).
Backwashing the DMF 104 can restore the organic matter filtration ability of the DMF
104. The concentration reduction processing unit 305 closes the first valve 503 and
opens the second valve 504 after activating the backwash pump 502 for a predetermined
period of time. The water quality monitoring device 111 then terminates the water
23
quality monitoring process and waits until the time of execution of a next water quality
monitoring process. Restoration of the organic matter filtration ability of the DMF 104
reduces the concentration of organic matter in water stored in the second water storage
tank 106 during a normal operation after backwashing. This allows the water quality
monitoring device 111 to regulate the quality of water that is supplied to the revers5 e
osmosis membrane 109, thereby preventing degradation of the reverse osmosis membrane
109.
On the other hand, when the viscosity difference is equal to or greater than the
threshold viscosity difference (step S605: NO), the evaluation unit 304 evaluates whether
10 or not the viscosity of water after passing through the DMF 104 is greater than a
predetermined threshold viscosity (step S607). When the viscosity of water after passing
through the DMF 104 is equal to or less than the predetermined threshold viscosity (step
S607: NO), the water quality monitoring device 111 terminates the water quality
monitoring process and waits until the time of execution of a next water quality monitoring
15 process.
On the other hand, when the viscosity of water after passing through the DMF 104
is greater than the predetermined threshold viscosity (step S607: YES), the concentration
reduction processing unit 305 outputs a command to add flocculant to the chemical
injection device 105 (step S608). The water quality monitoring device 111 then
20 terminates the water quality monitoring process and waits until the time of execution of a
next water quality monitoring process.
As described above, according to the present embodiment, the water quality
monitoring device 111 detects a reduction in the filtration ability of the DMF 104 on the
basis of the difference in viscosity between water before passing through the DMF 104
24
and water after passing through the DMF 104. This allows the water quality monitoring
device 111 to backwash the DMF 104 upon detecting a reduction in the filtration ability
of the DMF 104, thereby regulating the filtration ability of the DMF 104. That is, the
water quality monitoring device 111 can regulate the quality of water that is supplied to
the reverse osmosis membrane 109, thereby preventing degradation of the reverse osmo5 sis
membrane 109, not only when the quality of seawater taken in by the water intake device
101 has been reduced but also when the filtration ability of the DMF 104 has been reduced.
<>
A third embodiment is described below.
10 Fig. 7 is a schematic diagram showing a configuration of a seawater treatment
system according to the third embodiment.
A water quality monitoring device 111 of a seawater treatment system 1 according
to the third embodiment evaluates whether or not it is necessary to add a flocculant, the
type of the flocculant added, whether or not it is necessary to backwash the DMF 104, and
15 whether or not it is necessary to stop operation of the seawater treatment system 1 on the
basis of the result of measurement by the measurement device 108. Types of the
flocculant added by the chemical injection device 105 include an inorganic flocculant and
a polymer flocculant. Examples of the inorganic flocculant include ferric chloride.
Examples of the polymer flocculant include a cationic polymer flocculant such as a
20 polyacrylate ester compound. The polymer flocculant is used to additionally
agglomerate the organic matter agglomerated by the inorganic flocculant.
The seawater treatment system 1 according to the third embodiment does not
include the measurement device 108 between the first pump 103 and the DMF 104 among
the elements of the second embodiment. That is, the seawater treatment system 1
25
according to the third embodiment includes the backwash water tank 501, the backwash
pump 502, the first valve 503, and the second valve 504 in addition to the elements of the
first embodiment.
A sequence of a water quality monitoring process according to the present
embodiment will now be describe5 d.
Fig. 8 is a flowchart showing the sequence of the water quality monitoring process
according to the third embodiment.
The water quality monitoring device 111 performs the following water quality
monitoring process at regular intervals. When the water quality monitoring device 111
10 starts the water quality monitoring process, the speed determination unit 301 acquires
information indicating the speed of an ultrasonic wave from the measurement device 108
(step S801). The viscosity calculation unit 302 then calculates the viscosity of water that
is supplied to the reverse osmosis membrane 109 on the basis of the information acquired
by the speed determination unit 301 (step S802). The presentation unit 303 then allows
15 the display device to display the viscosity calculated by the viscosity calculation unit 302
(step S803).
The evaluation unit 304 evaluates whether or not the viscosity calculated by the
viscosity calculation unit 302 is greater than a first threshold viscosity (step S804). The
first threshold viscosity is obtained by multiplying an average viscosity of water that is
20 supplied to the reverse osmosis membrane 109 by a factor of 1 or more (for example, 1.1).
When the viscosity of water is equal to or less than the first threshold viscosity
(step S804: NO), the water quality monitoring device 111 terminates the water quality
monitoring process and waits until the time of execution of a next water quality monitoring
process.
26
On the other hand, when the viscosity of water is greater than the first threshold
viscosity (step S804: YES), the evaluation unit 304 evaluates whether or not the viscosity
calculated by the viscosity calculation unit 302 is greater than a second threshold viscosity
(step S805). The second threshold viscosity is greater than the first threshold viscosity.
The second threshold viscosity is obtained by multiplying an average viscosity of wate5 r
that is supplied to the reverse osmosis membrane 109 by a factor of 1 or more (for example,
1.2).
When the viscosity of water is equal to or less than the second threshold viscosity
(step S805: NO), the concentration reduction processing unit 305 outputs a command to
10 add an inorganic flocculant to the chemical injection device 105 (step S806). Upon
receiving the addition command, the chemical injection device 105 adds an inorganic
flocculant to water that is supplied to the DMF 104. The water quality monitoring device
111 then terminates the water quality monitoring process and waits until the time of
execution of a next water quality monitoring process.
15 On the other hand, when the viscosity of water is greater than the second threshold
viscosity (step S805: YES), the evaluation unit 304 evaluates whether or not the viscosity
calculated by the viscosity calculation unit 302 is greater than a third threshold viscosity
(step S807). The third threshold viscosity is greater than the second threshold viscosity.
The third threshold viscosity is obtained by multiplying an average viscosity of water that
20 is supplied to the reverse osmosis membrane 109 by a factor of 1 or more (for example,
1.3).
When the viscosity of water is equal to or less than the third threshold viscosity
(step S807: NO), the concentration reduction processing unit 305 outputs a command to
add a polymer flocculant to the chemical injection device 105 (step S808). Upon receiving
27
the addition command, the chemical injection device 105 adds a polymer flocculant to
water that is supplied to the DMF 104.
When the viscosity of water is greater than the second threshold viscosity, this
indicates that filtration by the DMF 104 is insufficient with only an inorganic flocculant
added. Therefore, the water quality monitoring device 111 according to the prese5 nt
embodiment additionally adds a polymer flocculant when the viscosity of water is greater
than the second threshold viscosity. This allows organic matter agglomerated by the
inorganic flocculant to be additionally agglomerated by the polymer flocculant such that
the organic matter is easily filtered out by the DMF 104.
10 On the other hand, when the viscosity of water is greater than the third threshold
viscosity (step S807: YES), the evaluation unit 304 evaluates whether or not the viscosity
calculated by the viscosity calculation unit 302 is greater than a fourth threshold viscosity
(step S809). The fourth threshold viscosity is greater than the third threshold viscosity.
The fourth threshold viscosity is obtained by multiplying an average viscosity of water
15 that is supplied to the reverse osmosis membrane 109 by a factor of 1 or more (for example,
1.5).
When the viscosity of water is equal to or less than the fourth threshold viscosity
(step S809: NO), the concentration reduction processing unit 305 activates the backwash
pump 502 after opening the first valve 503 and closing the second valve 504 (step S810).
20 The concentration reduction processing unit 305 closes the first valve 503 and opens the
second valve 504 after activating the backwash pump 502 for a predetermined period of
time. The water quality monitoring device 111 then terminates the water quality
monitoring process and waits until the time of execution of a next water quality monitoring
process.
28
When the viscosity of water is greater than the third threshold viscosity, this
indicates that filtration by the DMF 104 is insufficient with the flocculants added. That
is, when the viscosity of water is greater than the third threshold viscosity, there is a
possibility that the filtration ability of the DMF 104 has been reduced. Therefore, the water
quality monitoring device 111 according to the present embodiment backwashes the DM5 F
104 when the viscosity of water is greater than the third threshold viscosity.
On the other hand, when the viscosity of water is greater than the fourth threshold
viscosity (step S809: YES), the concentration reduction processing unit 305 stops
operation of the second pump 107 (step S811). This allows the concentration reduction
10 processing unit 305 to stop operation of the seawater treatment system 1. The water quality
monitoring device 111 then terminates the water quality monitoring process.
When the viscosity of water is greater than the fourth threshold viscosity, this
indicates that backwashing cannot restore the filtration ability of the DMF 104. That is,
when the viscosity of water is greater than the fourth threshold viscosity, there is a
15 possibility that an abnormality has occurred in the seawater treatment system 1.
Therefore, when the viscosity of water is greater than the fourth threshold viscosity, the
water quality monitoring device 111 stops operation of the seawater treatment system 1 to
prevent contaminated raw water from entering the reverse osmosis membrane 109.
Although the water quality monitoring device 111 stops operation of the seawater
20 treatment system 1 when the viscosity of water is greater than the fourth threshold viscosity
in the present embodiment, the present invention is not limited to this. For example, in
another embodiment, the water quality monitoring device 111 may reduce the amount of
water treated by the seawater treatment system 1 instead of stopping operation of the
seawater treatment system 1. In this case, the concentration reduction processing unit
29
305 reduces the pressure of the second pump 107 instead of stopping operation of the
second pump 107.
As described above, according to the present embodiment, the water quality
monitoring device 111 reduces the concentration of organic matter in water present
upstream of the reverse osmosis membrane 109 using a different method for each range 5 of
the viscosity of water that is supplied to the reverse osmosis membrane 109. This allows
the water quality monitoring device 111 to regulate the quality of water that is supplied to
the reverse osmosis membrane 109 using a method suitable for the amount of organic
matter included in water, thereby preventing degradation of the reverse osmosis membrane
10 109.
Although, in the present embodiment, the water quality monitoring device 111
reduces the concentration of organic matter in water present upstream of the reverse
osmosis membrane 109 using methods according to four ranges, i.e., a range greater than
the first threshold viscosity and equal to or less than the second threshold viscosity, a range
15 greater than the second threshold viscosity and equal to or less than the third threshold
viscosity, a range greater than the third threshold viscosity and equal to or less than the
fourth threshold viscosity, and a range greater than the fourth threshold viscosity, the
present invention is not limited to this. For example, in another embodiment, the water
quality monitoring device 111 may reduce the concentration of organic matter in water
20 present upstream of the reverse osmosis membrane 109 using methods according to at
least two of the four ranges. In another embodiment, the water quality monitoring device
111 may reduce the concentration of organic matter in water present upstream of the
reverse osmosis membrane 109 using methods according to five or more ranges.
<>
30
A fourth embodiment is described below.
The water quality monitoring device 111 of the seawater treatment system 1
according to the first to third embodiments takes measures for reducing the concentration
of organic matter when the viscosity of water is high. On the other hand, there is a
possibility that inorganic salts, inorganic colloids, and other inorganic microparticles 5 les may
be suspended in water that is supplied to the reverse osmosis membrane 109. Therefore,
when the increase in the viscosity of water is due to the suspension of inorganic
microparticles, there is a possibility that the quality of water is not sufficiently improved
by measures for reducing the concentration of organic matter.
10 The water quality monitoring device 111 of the seawater treatment system 1
according to the fourth embodiment determines whether to take measures against an
increase in organic matter or to take measures against an increase in the number of
inorganic microparticles when the viscosity of water is high.
The configuration of the seawater treatment system 1 according to the fourth
15 embodiment is the same as that of the seawater treatment system 1 according to the first
embodiment. The chemical injection device 105 according to the present embodiment
adds a flocculant for agglomerating inorganic microparticles in addition to the flocculant
for agglomerating organic matter.
Fig. 9 is a schematic block diagram showing a configuration of a water quality
20 monitoring device according to the fourth embodiment.
The water quality monitoring device 111 according to the fourth embodiment
includes a density determination unit 901 in addition to the elements of the first
embodiment.
The density determination unit 901 acquires information indicating the density of
31
water from the measurement device 108.
The water quality monitoring device 111 according to the fourth embodiment is
different from that of the first embodiment in the operations of the presentation unit 303,
the evaluation unit 304, and the concentration reduction processing unit 305.
The presentation unit 303 allows the display device to display the viscosit5 y
calculated by the viscosity calculation unit 302 and the density acquired by the density
determination unit 901.
The evaluation unit 304 evaluates whether or not it is necessary to add a flocculant
on the basis of the viscosity calculated by the viscosity calculation unit 302. The evaluation
10 unit 304 determines the type of a flocculant to be added on the basis of the density acquired
by the density determination unit 901.
The concentration reduction processing unit 305 outputs a command to add a
flocculant of the type determined by the determination unit to the chemical injection device
105.
15 A sequence of a water quality monitoring process according to the present
embodiment will now be described.
Fig. 10 is a flowchart showing the sequence of the water quality monitoring process
according to the fourth embodiment.
The water quality monitoring device 111 performs the following water quality
20 monitoring process at regular intervals. When the water quality monitoring device 111
starts the water quality monitoring process, the speed determination unit 301 acquires
information indicating the speed of an ultrasonic wave from the measurement device 108
(step S1001). The density determination unit 901 acquires information indicating the
density of water from the measurement device 108 (step S1002). The viscosity calculation
32
unit 302 then calculates the viscosity of water that is supplied to the reverse osmosis
membrane 109 on the basis of the information acquired by the speed determination unit
301 (step S1003). The presentation unit 303 then allows the display device to display the
viscosity calculated by the viscosity calculation unit 302 and the density acquired by the
density determination unit 901 (5 step S1004).
The evaluation unit 304 evaluates whether or not the viscosity calculated by the
viscosity calculation unit 302 is greater than the predetermined threshold viscosity (step
S1005). When the viscosity of water is equal to or less than the predetermined threshold
viscosity (step S1005: NO), the water quality monitoring device 111 terminates the water
10 quality monitoring process and waits until the time of execution of a next water quality
monitoring process. On the other hand, when the viscosity of water is greater than the
predetermined threshold viscosity (step S1005: YES), the evaluation unit 304 evaluates
whether or not the density acquired by the density determination unit 901 is greater than a
predetermined threshold density (step S1006). The threshold density according to the
15 present embodiment is an average density of water that is supplied to the reverse osmosis
membrane 109.
The density of inorganic microparticles is greater than the density of water. On
the other hand, the density of organic matter is less than the density of water. Therefore,
when a large amount of inorganic microparticles are suspended in water that is supplied to
20 the reverse osmosis membrane 109, the density of the water is greater than the average
density of water. When a large amount of organic matter is dissolved in water that is
supplied to the reverse osmosis membrane 109, the density of the water is equal to or less
than the average density of water.
When the density acquired by the density determination unit 901 is greater than the
33
predetermined threshold density (step S1006: YES), the concentration reduction
processing unit 305 outputs a command to add a flocculant for agglomerating inorganic
microparticles to the chemical injection device 105 (step S1007). On the other hand,
when the density acquired by the density determination unit 901 is equal to or less than
the predetermined threshold density (step S1006: NO), the concentration reducti5 on
processing unit 305 outputs a command to add a flocculant for agglomerating organic
matter to the chemical injection device 105 (step S1008).
As described above, the water quality monitoring device 111 according to the
present embodiment determines to take measures against an increase of inorganic
10 microparticles when the density of water is greater than the threshold density. In addition,
the water quality monitoring device 111 determines to take measures against an increase
of organic matter when the density of water is equal to or less than the threshold density.
This allows the water quality monitoring device 111 to take appropriate measures against
fouling according to the type of matter contained in the water.
15 In the present embodiment, when the density acquired by the density determination
unit 901 is greater than the predetermined threshold density, the chemical injection device
105 adds the flocculant for agglomerating inorganic microparticles, but the present
invention is not limited to this. For example, in another embodiment, if it can be
determined that the suspension of inorganic microparticles does not significantly affect the
20 fouling of the reverse osmosis membrane 109, the chemical injection device 105 may be
configured to add no flocculant when the density acquired by the density determination
unit 901 is greater than the predetermined threshold density.
In the present embodiment, the density determination unit 901 acquires information
indicating the density calculated based on the resonant frequency from the measurement
34
device 108 having the structure shown in Fig. 2, but the present invention is not limited to
this. For example, the measurement device 108 according to another embodiment may
calculate the density by measuring the weight of a specific amount of sampled water.
<>
A fifth embodiment is described below5 .
The water quality monitoring device 111 of the seawater treatment system 1
according to the fourth embodiment determines whether to take measures against an
increase in organic matter or to take measures against an increase of inorganic
microparticles according to the density of water. On the other hand, a water quality
10 monitoring device 111 of a seawater treatment system 1 according to the fifth embodiment
determines the proportions of organic matter and inorganic microparticles present in water
on the basis of the density of the water and determines whether to take measures against
an increase of organic matter or to take measures against an increase of inorganic
microparticles.
15 Fig. 11 is a schematic block diagram showing a configuration of the water quality
monitoring device according to the fifth embodiment.
The water quality monitoring device 111 according to the fifth embodiment
includes a volume fraction calculation unit 1101 in addition to the elements of the fourth
embodiment. The volume fraction calculation unit 1101 calculates the volume fractions
20 of organic matter and inorganic microparticles in water on the basis of the viscosity
calculated by the viscosity calculation unit 302 and the density determined by the density
determination unit 901.
Here, a method of calculating the volume fractions of organic matter and inorganic
microparticles in water will be described. The density ρ of water that is supplied to the
35
reverse osmosis membrane 109 is expressed by the following equation (1).
Math. 1
ρsw is the standard density of seawater. ρO is the density of organic matter. ρI is
the density of inorganic microparticles. ϕO is the volume fraction of organic matter. ϕ5 I
is the volume fraction of inorganic microparticles.
The relative viscosity ηr of water that is supplied to the reverse osmosis membrane
109 is expressed by the following equation (2). The relative viscosity is a value obtained
by dividing the viscosity measured by the measurement device 108 by the average
10 viscosity of water that is supplied to the reverse osmosis membrane 109.
Math. 2
kO is a coefficient of the viscosity of organic matter. kI is a coefficient of the
viscosity of inorganic microparticles.
15 For example, the coefficient kO of the viscosity of organic substances can be
determined previously by dissolving a water-soluble polymer (for example, polyethylene
oxide, xanthan gum, or guar gum) in water having an average viscosity while varying the
concentration of the water-soluble polymer and obtaining a linear equation indicating the
relationship between the volume fraction and the viscosity. The intercept of the linear
20 equation is 1.
For example, the coefficient kI of the viscosity of inorganic microparticles can be
determined previously by suspending inorganic microparticles (for example, silica fine
36
particles or calcium carbonate fine particles) in water having an average viscosity while
varying the concentration of the inorganic microparticles and obtaining a linear equation
indicating the relationship between the volume fraction and the viscosity. The intercept of
the linear equation is 1.
From the above equations (1) and (2), the volume fraction ϕO of the organic 5 matter
and the volume fraction ϕI of the inorganic microparticles can be expressed by the following
equations (3). The volume fraction calculation unit 1101 calculates the volume fraction
ϕO of the organic matter and the volume fraction ϕI of the inorganic microparticles on the
basis of equations (3).
10 Math. 3
The water quality monitoring device 111 according to the fifth embodiment is
15 different from that of the fourth embodiment in the operations of the presentation unit 303
and the evaluation unit 304.
The presentation unit 303 allows the display device to display the viscosity
calculated by the viscosity calculation unit 302, the density acquired by the density
determination unit 901, and the volume fraction calculated by the volume fraction
20 calculation unit 1101.
Based on the volume fraction calculated by the volume fraction calculation unit
37
1101, the evaluation unit 304 evaluates whether or not it is necessary to add a flocculant
used to agglomerate organic matter and a flocculant used to agglomerate inorganic
microparticles.
A sequence of a water quality monitoring process according to the present
embodiment will now be describe5 d.
Fig. 12 is a flowchart showing the sequence of the water quality monitoring process
according to the fifth embodiment.
The water quality monitoring device 111 performs the following water quality
monitoring process at regular intervals. When the water quality monitoring device 111
10 starts the water quality monitoring process, the speed determination unit 301 acquires
information indicating the speed of an ultrasonic wave from the measurement device 108
(step S1201). The density determination unit 901 acquires information indicating the
density of water from the measurement device 108 (step S1202). The viscosity calculation
unit 302 then calculates the viscosity of water that is supplied to the reverse osmosis
15 membrane 109 on the basis of the information acquired by the speed determination unit 301
(step S1203).
The volume fraction calculation unit 1101 then calculates the volume fractions of
organic matter and inorganic microparticles in water on the basis of the viscosity calculated
by the viscosity calculation unit 302 and the density determined by the density determination
20 unit 901 (step S1204). The presentation unit 303 then allows the display device to display
the viscosity calculated by the viscosity calculation unit 302, the density acquired by the
density determination unit 901, and the volume fractions calculated by the volume fraction
calculation unit 1101 (step S1205).
The evaluation unit 304 evaluates whether or not the volume fraction of organic
38
matter calculated by the volume fraction calculation unit 1101 is greater than a first
threshold volume fraction (step S1206). The first threshold volume fraction according to
the present embodiment is a volume fraction corresponding to 100 ppb of organic matter.
When the volume fraction of the organic matter is greater than the first threshold volume
fraction (step S1206: YES), the concentration reduction processing unit 305 outputs 5 a
command to add a flocculant for agglomerating organic matter to the chemical injection
device 105 (step S1207).
When the volume fraction of the organic matter is equal to or less than the first
threshold volume fraction (step S1206: NO) or when the concentration reduction processing
10 unit 305 has output a command to add a flocculant for agglomerating organic matter, the
evaluation unit 304 evaluates whether or not the volume fraction of the inorganic
microparticles calculated by the volume fraction calculation unit 1101 is greater than a
second threshold volume fraction (step S1208). The second threshold volume fraction
according to the present embodiment is a volume fraction of inorganic microparticles
15 corresponding to a silt density index (SDI) 3. When the volume fraction of the inorganic
microparticles is greater than the second threshold volume fraction (step S1208: YES), the
concentration reduction processing unit 305 outputs a command to add a flocculant for
agglomerating inorganic microparticles to the chemical injection device 105 (step S1209).
When the volume fraction of the organic matter is equal to or less than the first
20 threshold volume fraction (step S1208: NO) or when the concentration reduction processing
unit 305 has output a command to add a flocculant for agglomerating inorganic
microparticles, the water quality monitoring device 111 terminates the water quality
monitoring process and waits until the time of execution of a next water quality monitoring
process.
39
As described above, the water quality monitoring device 111 according to the
present embodiment determines whether or not to take measures against an increase of
organic matter and whether or not to take measures against an increase of inorganic
microparticles on the basis of the volume fractions of organic matter and inorganic
microparticles. This allows the water quality monitoring device 111 to take appropr5 iate
measures against fouling according to the type of matter contained in the water.
<>
A sixth embodiment is described below.
Fig. 13 is a schematic diagram showing a configuration of a seawater treatment
10 system according to the sixth embodiment.
When the quality of water that is supplied to the reverse osmosis membrane 109
has been reduced, a seawater treatment system 1 according to the sixth embodiment samples
the water.
The seawater treatment system 1 according to the sixth embodiment includes a
15 sample tank 1301 and a three-way valve 1302 in addition to the elements of the first
embodiment.
The three-way valve 1302 is provided at a branch point between a pipe, which
connects a pipe connected to the second pump 107 and the reverse osmosis membrane 109,
and a pipe connected to the sample tank 1301. The three-way valve 1302 switches the
20 destination of water pumped by the second pump 107 between the reverse osmosis
membrane 109 and the sample tank 1301.
Fig. 14 is a schematic block diagram showing a configuration of a water quality
monitoring device according to the sixth embodiment.
A water quality monitoring device 111 according to the sixth embodiment includes
40
a sampling processing unit 1401 in addition to the elements of the first embodiment.
The sampling processing unit 1401 controls the opening and closing of the threeway
valve 1302 on the basis of the result of evaluation by the evaluation unit 304. The
sampling processing unit 1401 is an example of a process execution unit which performs a
process on the basis of the speed of the ultrasonic wave determined by the spee5 d
determination unit 301.
Fig. 15 is a flowchart showing a sequence of a water quality monitoring process
according to the sixth embodiment.
The water quality monitoring device 111 performs the following water quality
10 monitoring process at regular intervals. When the water quality monitoring device 111
starts the water quality monitoring process, the speed determination unit 301 acquires
information indicating the speed of an ultrasonic wave from the measurement device 108
(step S1501). The viscosity calculation unit 302 then calculates the viscosity of water that
is supplied to the reverse osmosis membrane 109 on the basis of the information acquired
15 by the speed determination unit 301 (step S1502). The presentation unit 303 then allows
the display device to display the viscosity calculated by the viscosity calculation unit 302
(step S1503).
The evaluation unit 304 evaluates whether or not the viscosity calculated by the
viscosity calculation unit 302 is greater than the predetermined threshold viscosity (step
20 S1504). When the viscosity of water is equal to or less than the predetermined threshold
viscosity (step S1504: NO), the water quality monitoring device 111 terminates the water
quality monitoring process and waits until the time of execution of a next water quality
monitoring process. On the other hand, when the viscosity of water is greater than the
predetermined threshold viscosity (step S1504: YES), the sampling processing unit 1401
41
switches the opening and closing of the three-way valve 1302 such that the water pumped
by the second pump 107 is delivered to the sample tank 1301 (step S1505). The sampling
processing unit 1401 waits until a predetermined amount of water is stored in the sample
tank 1301 (step S1506). Upon finishing the waiting, the sampling processing unit 1401
switches the opening and closing of the three-way valve 1302 such that the water pumpe5 d
by the second pump 107 is delivered to the reverse osmosis membrane 109 (step S1507).
The concentration reduction processing unit 305 then outputs a command to add a
flocculant to the chemical injection device 105 (step S1508). The water quality monitoring
device 111 then terminates the water quality monitoring process and waits until the time of
10 execution of a next water quality monitoring process.
According to the present embodiment, when the quality of the water supplied to
the reverse osmosis membrane 109 has been reduced, the water quality monitoring device
111 can sample the water as described above. This allows the manager of the seawater
treatment system 1 to analyze the quality of the sampled water. That is, the water quality
15 monitoring device 111 according to the present embodiment can contribute to determining
the causative substances of fouling through water quality analysis.
Although the embodiments have been described in detail with reference to the
drawings, the specific configurations are not limited to those described above and various
design changes or the like can be made.
20 In the embodiments described above, the water quality monitoring device 111
evaluates whether or not to perform a process of reducing the concentration of organic
matter in water present upstream of the reverse osmosis membrane 109, but the present
invention is not limited to this. For example, in another embodiment, the manager of the
seawater treatment system 1 may perform the same processes as that of the above-described
42
embodiments by viewing parameters correlated with the concentration of organic matter
presented by the presentation unit 303. Examples of parameters correlated with the
concentration of organic matter are warnings indicating that the viscosity of water, the speed
of an ultrasound wave, the estimated concentration of organic matter, and the volume
fraction of organic matter are high. In this case, the water quality monitoring device 115 1
may include at least the speed determination unit 301 and the presentation unit 303. On
the other hand, in another embodiment, the water quality monitoring device 111 may not
include the presentation unit 303 when the water quality monitoring device 111 performs a
process of reducing the concentration of organic matter in water present upstream of the
10 reverse osmosis membrane 109.
Although the speed determination unit 301 according to the above embodiments
acquires information indicating the speed from the measurement device 108, the present
invention is not limited to this and the speed determination unit 301 may acquire another
physical quantity related to the speed. For example, in another embodiment, the speed
15 determination unit 301 may acquire information indicating the viscosity from the
measurement device 108 when the viscosity is calculated based on the speed of an ultrasonic
wave measured by the measurement device 108. For example, the speed determination
unit 301 according to another embodiment may acquire, from the measurement device 108,
information indicating a period of time from when an ultrasonic wave is transmitted to when
20 the ultrasonic wave is received.
Although the density determination unit 901 according to the above embodiments
acquires information indicating the density from the measurement device 108, the present
invention is not limited to this and the density determination unit 901 may acquire another
physical quantity related to the density. For example, the density determination unit 901
43
according to another embodiment may acquire the resonant frequency of the U-shaped tube
203 from the measurement device 108.
Fig. 16 is a cross-sectional view showing a structure of a measurement device
according to a modified example.
Both ends of the U-shaped tube 203 of the measurement device 108 according 5 to
the above-described embodiments are attached directly to the pipe connecting the second
pump 107 and the reverse osmosis membrane 109, but the present invention is not limited
to this. For example, in other embodiments, one or both ends of the U-shaped tube 203
may be attached to the pipe via a valve 1601 as shown in Fig. 16. Thus, while the
10 calculator 208 measures the period of time from when an ultrasonic wave is transmitted to
when the ultrasonic wave is received, it is possible to stop the flow of water in the U-shaped
tube 203 during measurement by closing the valve 1601.
Fig. 17 is a schematic block diagram showing a configuration of a computer
according to at least one of the embodiments.
15 The computer 1700 includes a CPU 1701, a main storage device 1702, an auxiliary
storage device 1703, and an interface 1704.
The water quality monitoring device 111 described above is mounted on the
computer 1700. The operations of the processing units described above are stored in the
auxiliary storage device 1703 in the form of a program. The CPU 1701 reads the program
20 from the auxiliary storage device 1703, develops the program in the main storage device
1702, and executes the above processes according to the program.
In at least one of the embodiments, the auxiliary storage device 1703 is an example
of a non-transitory tangible medium. Other examples of a non-transitory tangible medium
include a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, or a
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semiconductor memory connected via the interface 1704. Further, when this program is
delivered to the computer 1700 via a communication line, the computer 1700 may develop
the program in the main storage device 1702 upon receiving the program and execute the
above processes.
The program may be one for realizing some of the functions described above. 5 The
program may also be a so-called differential file (differential program) which realizes the
functions described above in combination with a program which has already been recorded
in the auxiliary storage device 1703.
Industrial Applicability
10 The water quality monitoring device 111 measures the speed of a wave generated
in water present upstream of the reverse osmosis membrane 109. Therefore, using a
computer capable of processing at an appropriate temporal resolution, the water quality
monitoring device 111 can detect changes in concentration of fouling substances at several
hundred ppb.
15 Reference Signs List
1 Seawater treatment system
108 Measurement device
109 Reverse osmosis membrane
111 Water quality monitoring device
20 204 Ultrasonic wave transmitter
205 Ultrasonic wave receiver
206 Oscillator
207 Vibration detector
301 Speed determination unit
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302 Viscosity calculation unit
303 Presentation unit
304 Evaluation unit
305 Concentration reduction processing unit
901 Density determination 5 n unit
1101 Volume fraction calculation unit
1401 Sampling processing unit

CLAIMS:
1. A water quality monitoring device that monitors water quality in a water treatment
device generating fresh water using a reverse osmosis membrane, the water quality
monitoring device comprising:
a speed determination unit configured to determine a speed of a wave passi5 ng
through water present upstream of the reverse osmosis membrane to measure a
parameter correlated with a concentration of organic matter in the water; and
a concentration reduction processing unit configured to reduce the
concentration of organic matter in water present upstream of the reverse osmosis
10 membrane when the speed determined by the speed determination unit is greater
than a predetermined threshold speed.
2. The water quality monitoring device according to claim 1, further comprising:
a density determination unit configured to determine a density of water
15 present upstream of the reverse osmosis membrane,
wherein, when the speed determined by the speed determination unit is
greater than the predetermined threshold speed and the density determined by the
density determination unit is less than a predetermined threshold density, the
concentration reduction processing unit reduces the concentration of organic matter
20 in water present upstream of the reverse osmosis membrane.
3. The water quality monitoring device according to claim 1 or 2, wherein the
concentration reduction processing unit reduces the concentration of organic matter
in water present upstream of the reverse osmosis membrane by using a method
25 corresponding to a speed range that includes the speed determined by the speed
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determination unit, the speed range being one of a plurality of speed ranges, the
method being different for each speed range.
4. The water quality monitoring device according to any one of claims 1 to 3, wherein
the concentration reduction processing unit reduces the concentration of organi5 c
matter in water present upstream of the reverse osmosis membrane by outputting a
command to add a flocculant to a chemical injection device, the chemical injection
device adding a flocculant to water that is supplied to a pretreatment device provided
upstream of the reverse osmosis membrane.
10
5. The water quality monitoring device according to any one of claims 1 to 4, wherein
the concentration reduction processing unit reduces the concentration of organic
matter in water present upstream of the reverse osmosis membrane by activating a
backwash device, the backwash device backwashing a pretreatment device provided
15 upstream of the reverse osmosis membrane.
6. The water quality monitoring device according to claim 2, further comprising:
a concentration determination unit configured to determine a parameter correlated
with a concentration of organic matter and a parameter correlated with a
20 concentration of inorganic microparticles on the basis of the speed determined by
the speed determination unit and the density determined by the density determination
unit,
wherein the concentration reduction processing unit reduces the
concentration of organic matter in water present upstream of the reverse osmosis
25 membrane when the parameter correlated with the concentration of organic matter
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determined by the concentration determination unit is greater than the predetermined
threshold speed; and
the concentration reduction processing unit reduces the concentration of
inorganic matter in water present upstream of the reverse osmosis membrane when
the parameter correlated with the concentration of inorganic matter determined b5 y
the concentration determination unit is greater than the predetermined threshold
speed.
7. A water quality monitoring device that monitors water quality in a water treatment
10 device generating fresh water using a reverse osmosis membrane, the water quality
monitoring device comprising:
a speed determination unit configured to determine a speed of a wave passing
through water present upstream of the reverse osmosis membrane to measure a
parameter correlated with a concentration of organic matter in the water; and
15 a presentation unit configured to present the parameter correlated with the
speed determined by the speed determination unit.
8. The water quality monitoring device according to claim 7, further comprising:
a density determination unit configured to determine a density of water
20 present upstream of the reverse osmosis membrane,
wherein the presentation unit presents parameters correlated with the speed
and the density.
9. The water quality monitoring device according to claim 8, further comprising:
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a concentration determination unit configured to determine a parameter
correlated with a concentration of organic matter and a parameter correlated with a
concentration of inorganic microparticles on the basis of the speed determined by
the speed determination unit and the density determined by the density determination
unit5 ,
wherein the presentation unit presents the parameter correlated with the
concentration of organic matter and the parameter correlated with the concentration
of inorganic microparticles.
10 10. The water quality monitoring device according to any one of claims 1 to 9, further
comprising:
a storage processing unit configured to store part of water present upstream
of the reverse osmosis membrane in a predetermined container when the speed
determined by the speed determination unit is greater than the predetermined
15 threshold speed.
11. The water quality monitoring device according to any one of claims 1 to 10, wherein
the speed determination unit determines a speed of a wave passing through water
before passing through a pretreatment device and a speed of a wave passing through
20 water after passing through the pretreatment device, the pretreatment device being
provided upstream of the reverse osmosis membrane.
12. A water treatment device comprising:
a reverse osmosis membrane;
25 a wave transmitter provided upstream of the reverse osmosis membrane and
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configured to generate a wave in water present upstream of the reverse osmosis
membrane; and
a wave receiver provided upstream of the reverse osmosis membrane and
configured to detect the wave generated by the wave transmitter.
5
13. The water treatment device according to claim 12, further comprising:
a vibration tube through that water present upstream of the reverse osmosis
membrane flows;
an oscillator configured to vibrate the vibration tube; and
10 a vibration detector configured to detect a vibrational amplitude of the
vibration tube,
wherein the wave transmitter and the wave receiver are provided on the
vibration tube.
15 14. A water treatment system comprising:
the water treatment device according to claim 12 or 13; and
the water quality monitoring device according to any one of claims 1 to 11.
15. A water quality monitoring method comprising the steps of:
20 determining a speed of a wave passing through water present upstream of a
reverse osmosis membrane; and
reducing a concentration of organic matter in water present upstream of the reverse
osmosis membrane when the determined speed is greater than a predetermined
threshold speed.
25
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16. A program causing a computer for a water quality monitoring device, that monitors
water quality in a water treatment device that generates fresh water using a reverse
osmosis membrane, to function as:
a speed determination unit configured to determine a speed of a wave passing
through water present upstream of the reverse osmosis membrane to measure 5 a
parameter correlated with a concentration of organic matter in the water; and
a concentration reduction processing unit configured to reduce the
concentration of organic matter in water present upstream of the reverse osmosis
membrane when the speed determined by the speed determination unit is greater
10 than a predetermined threshold speed.
17. A program causing a computer for a water quality monitoring device monitoring
water quality in a water treatment device that generates fresh water using a reverse
osmosis membrane, to function as:
15 a speed determination unit configured to determine a speed of a wave passing
through water present upstream of the reverse osmosis membrane to measure a
parameter correlated with a concentration of organic matter in the water; and
a presentation unit configured to present the parameter correlated with the
speed determined by the speed determination unit.