Technical Field
The present invention relates to a scale detection device and a method for a
concentrating device, and a water reclamation treatment system.
Background Art
Mine wastewater, for example, contains pyrite (FeS2), which oxidizes t5 o
produce SO4
2-. In order to neutralize the mine wastewater, Ca(OH)2, which is low-cost,
is used. Therefore, the mine wastewater contains Ca2+ and SO4
2- in abundance.
It is known that saline water, sewage and industrial waste water also contain
Ca2+ and SO4
2- in abundance. In a cooling tower, heat exchange is performed between
10 cooling water and high-temperature exhaust gas discharged from a boiler. A portion of
the cooling water becomes steam due to this heat exchange, so the ions in the cooling
water are concentrated. Accordingly, the cooling water discharged from the cooling
tower (blowdown water) contains high concentrations of ions such as Ca2+ and SO4
2-.
The water containing large quantities of ions is typically released into the
15 environment after being desalinated. Known examples of concentrating device for
performing desalination treatment include a reverse osmosis membrane device, a
nanofiltration membrane device, and an ion exchange membrane device.
However, in the desalination treatment using these devices, if cations (e.g.
calcium ions (Ca2+)) and anions (e.g. sulfate ions, (SO4
2-)) at high concentrations are
20 concentrated on a membrane upon recovering reclaimed water thereof, the
concentrations may exceed the solubility limit of calcium sulfate (gypsum (CaSO4)),
which is a poorly soluble mineral salt. This may become problematic, because
deposition may be formed on the membrane surface as scales, causing the reduction in
permeation flux (flux) of reclaimed water.
25 Therefore, monitoring methods for mineral salt crystalline formation have been
proposed in the conventional art, such as a method in which a cell monitoring the
reverse osmosis membrane in the reverse osmosis membrane device was used to
monitor the reverse osmosis membrane and the formation of the mineral salt crystals
was visually observed (Patent Document 1).
30 Citation List
Patent Literature
Patent Document 1: Japanese Unexamined Patent Application Publication No.
2009-524521A
3
Summary of Invention
Technical Problem
However, the monitoring method in the Patent Document 1 includes detecting
the deposition of mineral salt crystals on the monitoring cell and monitoring using the
monitoring cell and may fail to detect signs of crystal deposition in advance since th5 e
deposition of mineral salt crystal is also occurring on the reverse osmosis membrane.
Thus, a scale monitoring device is desired, which is able to detect crystal
deposition on a reverse osmosis membrane of a reverse osmosis membrane device in
advance, upon water treatment of water to be treated using the reverse osmosis device.
10 In view of the problem described above, the present invention aims to provide a
scale detection device and method, which are able to detect crystal deposition on a
filtering membrane of a concentrating device in advance, and a water reclamation
treatment system.
Solution to Problem
15 To solve the problems described above, the first invention of the present
invention relates to a scale detection device of a concentrating device comprising: a
concentrating device including a filtering membrane, concentrating salt in a water to
be treated containing at least calcium sulfate to obtain reclaimed water; and a scale
detection device disposed in a branched line branched from a concentrated water line
20 discharging concentrated water having a high concentration of salt, the scale detection
unit further concentrating salt in the concentrated water to obtain reclaimed water for
detection, and including a detection membrane detecting the absence or presence of
scale component deposition in the concentrated water.
The second invention relates to the scale detection device of the concentrating
25 device according to the first invention, which comprises a booster pump to increase a
pressure of the concentrated water supplied to the detection membrane in the scale
detection unit.
The third invention relates to the scale detection device of the concentrating
device according to the first or the second invention, which comprises a valve that
30 reduces an amount of the concentrated water for detection separat ed at the detection
membrane.
The fourth invention relates to the scale detection device of the concentrating
device according to the third invention, which comprises a circulation line that feeds
the concentrated water for detection separated at the detection membrane back to an
35 inlet of the detection membrane.
The fifth invention relates to the scale detection device of the concentrating
device according to any one of the first to the fourth inventions, which comprises a
4
heat exchange device that performs heat exchange on the concentrated water supplied
to the scale detection unit.
The sixth invention relates to the scale detection device of the concentrating
device according to any one of the first to the fifth inventions, in which an effect of a
scale inhibitor is canceled out by supplying an acid to the concentrated water exitin5 g
from the concentrating device, when scale deposition on the filtering membrane of the
concentrating device is prevented by supplying the scale inhibitor to the water to be
treated before introduction to the concentrating device.
The seventh invention relates to the scale detection device of the concentrating
10 device according to any one of the first to the sixth inventions, in which the scale
component is calcium sulfate and the detection membrane is a reverse osmosis
membrane.
The eighth invention relates to the scale detection device of the concentrating
device according to any one of the first to the seventh inventions, in which the water
15 to be treated is any one of mine wastewater, blowdown water of a power plant cooling
tower, accompanying water during machining using oil or gas, saline water, and
industrial waste water.
The ninth invention of the present invention is a scale detection method of the
concentrating device, which comprises a salt concentrating step of concentrating salt
20 in water to be treated containing at least calcium sulfate by a filtering membrane, and
separating the water to be treated into reclaimed water and concentrated water; and a
scale detection step of obtaining reclaimed water for detection by further
concentrating salt in a portion of separated and salt -concentrated water, and detecting
the absence or presence of scale component deposition in the concentrated water.
25 The tenth invention relates to the scale detection method of the concentrating
device according to the ninth invention, in which a pressure of the concentrated water
supplied to a detection membrane in the scale detection step is increased to improve a
concentration ratio.
The eleventh invention relates to the scale detection method of the
30 concentrating device according to the ninth or the tenth invention, in which an amount
of concentrated water for detection separated at the detection membrane is reduced to
improve the concentration ratio.
The twelfth invention relates to the scale detection method of the concentrating
device according to any one of the ninth to eleventh inventions, in which the
35 concentrated water for detection separated at the detection membrane is sent back to
an inlet of the detection membrane to improve the concentration ratio.
The thirteenth invention relates to the scale detection device of the
concentrating device according to any one of the ninth to the twelfth inventions, in
5
which the concentrated water supplied to the scale detection unit is subjected to heat
exchange to increase the amount of the scale deposition.
The fourteenth invention relates to the scale detection device of the
concentrating device according to any one of the ninth to the thirteenth inventions, in
which an effect of a scale inhibitor is canceled out by supplying an acid to th5 e
concentrated water exiting from the concentrating device, when scale deposition on
the filtering membrane of the concentrating device is prevented by supplying the scale
inhibitor to the water to be treated before introduction to the concentrating device.
A fifteenth invention of the present invention is a water reclamation treatment
10 system comprising: a first scale inhibitor-supplying unit supplying a scale inhibitor to
water to be treated containing a calcium sulfate component; a first pH-adjusting unit
adjusting a pH of discharged water to which the scale inhibitor has been supplied
using a pH-adjusting agent; a first concentrating device provided downstream of the
first pH-adjusting unit, the first concentrating device concentrating salt in the water to
15 be treated and separating the water to be treated into first reclaimed water and first
concentrated water; a crystallizing tank provided downstream of the first
concentrating device, the crystallizing tank crystallizing calcium sulfate from the first
concentrated water; a first scale detection unit provided in a first branch line branched
from a first concentrated water line discharging the first concentrated water with sal t
20 therein concentrated at the first concentrating device, the first scale detection unit
obtaining a first reclaimed water for detection by further concentrating salt from the
first concentrated water and including a first detecting membrane detecting the
absence or presence of scale component deposition in the concentrated water.
A sixteenth invention of the present invention is a water reclamation treatment
25 system according to the fifteenth invention, further comprising: a second scale
inhibitor-supplying unit supplying a scale inhibitor to the first concentrated water,
calcium sulfate having been separated from the first concentrated water; a second pHadjusting
unit adjusting a pH of the first concentrated water, the scale inhibitor having
been supplied to the first concentrated water; a second concentrating device provided
30 downstream of the second pH-adjusting unit, the second concentrating device
concentrating salt in the first concentrated water and separating the first concentrated
water into second reclaimed water and second concentrated water; and a second scale
detection unit provided in a second branch line branched from a second concentrated
water line discharging the second concentrated water with salt therein concentrated at
35 the second concentrating device, the second scale detection unit obtaining a second
reclaimed water for detection by further concentrating salt from the second
concentrated water and including a second detecting membrane detecting the absence
or presence of scale component deposition in the second concentrated water.
6
Advantageous Effects of Invention
According to the present invention, by having a scale detection unit, crystal
deposition on the filtering membrane in the concentrating device is detected in
advance, when the water to be treated is treated using the concentrating device.
Brief Description of Drawing5 s
FIG. 1 is a schematic diagram of a scale detection device of a concentrating
device according to Embodiment 1.
FIG. 2 is a graph illustrating the relationship between the time of water
treatment operation (horizontal axis), the amount of scale deposition on the filtering
10 membrane (left vertical axis) and the permeation flux (right vertical axis).
FIG. 3 is a schematic diagram of a scale detection device of another
concentrating device according to Embodiment 1.
FIG. 4 is a schematic diagram of a scale detection device of another
concentrating device according to Embodiment 1.
15 FIG. 5 is a schematic diagram of a scale detection device of a concentrating
device according to Embodiment 2.
FIG. 6 is a schematic diagram of a scale detection device of a concentrating
device according to Embodiment 3.
FIG. 7 is a schematic diagram of a scale detection device of a concentrating
20 device according to Embodiment 4.
FIG. 8 is a graph illustrating the temperature dependence of calcium sulfate
solubility.
FIG. 9 is a schematic diagram of a scale detection device of a concentrating
device according to Embodiment 5.
25 FIG. 10 is a schematic diagram of a configuration of a water reclamation
treatment system according to Embodiment 6.
FIG. 11 is a schematic diagram of a configuration of another water reclamation
treatment system according to Embodiment 6.
Description of Embodiments
30 The following is a detailed description of preferred embodiment s of the present
invention with reference to the attached drawings. Note that the present invention is
not limited by the embodiments, and when a plurality of embodiments are present, the
invention is intended to include a configuration combining these embodiments.
Example 1
35 FIG. 1 is a schematic diagram of a scale detection device of a concentrating
device according to Embodiment 1. FIG. 2 is a graph illustrating the relationship
7
between the time of water treatment operation (horizontal axis), the amount of scale
deposition on the filtering membrane (left vertical axis) and the permeation flux (right
vertical axis). FIG. 3 and FIG. 4 are schematic diagrams of scale detection devices of
other concentrating devices according to Embodiment 1.
As illustrated in FIG. 1, the scale detection device of a concentrating devic5 e
according to the present embodiment includes: a reverse osmosis membrane device 13
that is a concentrating device including a reverse osmosis membrane 13a, which is a
filtering membrane for concentrating salts from water to be treated 11 containing at
least calcium sulfate, and obtaining reclaimed water 12; and a scale detection unit 15
10 disposed in a branch line L14 branching from a concentrated water line L13 that
discharges concentrated water 14 having a high concentration of salts, the scale
detection unit 15 including a detection membrane 15a for further concentrating the
salt from the concentrated water 14 and obtaining reclaimed water for detection 16 as
well as detecting the absence or presence of scale component deposition in the
15 concentrated water 14. In FIG. 1, the reference sign 20 denotes a pressure gauge, 21
denotes a flow meter, L11 denotes an introduction line for water to be treated, and L12
denotes a discharge line for reclaimed water. In the present embodiment, a reverse
osmosis membrane device is used as a concentrating device to obtain reclaimed water
for description as an example, however the present invention is not limited to this
20 example. The concentrating device is not particularly limited as long as it is a device
that concentrates the water to be treated and produces reclaimed water using a
filtering membrane.
The water to be treated 11 herein is water that contains calcium sulfate as a
scale component, such as mine wastewater. blowdown water of a power plant cooling
25 tower, accompanying water during machining using oil or gas, saline water, and
industrial waste water, for example.
The water to be treated 11 is pressurized to a predetermined pressure using a
booster pump P1 disposed in the introduction line for the water to be treated L11, and
introduced to a reverse osmosis membrane device 13 including a reverse osmosis (RO)
30 membrane 13a.
At the reverse osmosis membrane device 13 as a salt concentrating step, salts in
the water to be treated 11 are concentrated while the water passed through the reverse
osmosis membrane 13a is reclaimed as reclaimed water 12 and collected.
From the concentrated water 14, in which the salts are concentrated, calcium
35 sulfate and the like are collected (refer to Embodiment 6 described below).
In the present embodiment, a branched line L14 is disposed, branching from a
portion of the concentrated water line L13 that discharges the concentrated water 14.
Also, the scale detection unit 15 is disposed in the branched line L14, the scale
8
detection unit 15 including a detection membrane 15a, which further concentrates salts
in the branched concentrated water 14, and obtains reclaimed water for detection 16 as
well as detects the absence or presence of scale component deposition in the
concentrated water 14.
The detection membrane 15a is preferably a reverse osmosis (RO) membrane5 .
Especially, it is more preferable that the detection membrane 15a has the same
characteristics as that of the reverse osmosis membrane 13a in the reverse osmosis
membrane device 13 disposed in the main line, so that they exhibit the same
membrane behavior.
10 In the present invention, the concentrated water 14 is supplied to the detection
membrane 15. Consequently, the scale component can be detected earlier than at the
reverse osmosis membrane 13a, because the salt concentration is greater than that of
water to be treated 11, which is introduced to the reverse osmosis membrane 13a of
the reverse osmosis membrane device 13, and concentration is accelerated.
15 To verify presence or absence of the scale component, the flow meter for
detection 22 is used. The flow meter 22 is disposed in the reclaimed water discharge
line for detection L15, which discharges the reclaimed water for detection 16.
Specifically, the scale is not deposited when the flow meter for detection 22
indicates the permeation flux (flux) of the reclaimed water for detection 16 to be a
20 predetermined value. The scale deposition on the detection membrane 15a reduces the
permeation flux, and by detecting the reduction, it is possible to wash the reverse
osmosis membrane 13a of the reverse osmosis membrane device 13 in the main line
before the scale deposition on the reverse osmosis membrane 13a occurs.
Using FIG. 2, the relationship between the time of water treatment operation
25 (horizontal axis), the amount of scale deposition on the filtering membrane (left
vertical axis) and the permeation flux (right vertical axis) is described below.
In FIG. 2, the solid line A indicates the permeation flux (flux) of the reclaimed
water 12 that permeates through the reverse osmosis membrane 13a of the reverse
osmosis membrane device 13 in the main line, and the solid line B indicates the level
30 of the scale deposition on the reverse osmosis membrane 13a of the reverse osmosis
membrane device 13 in the main line. In FIG. 2, the dashed line a indicates the
permeation flux of the reclaimed water that permeates through the reverse osmosis
membrane 15a, and the dashed line b indicates the level of the scale deposition on the
reverse osmosis membrane 15a.
35 As illustrated in FIG. 2, (1) scale component in the concentrated water 14 starts
to deposit on the detection membrane 15a as the time of operation passes . Then, (2)
the decrease in the permeation flux (flux) at the detection membrane 15a is detected.
9
When the decrease in the permeation flux is detected at the detection membrane
15a, the flushing cleaning of the reverse osmosis membrane device 13 is performed.
In flushing cleaning, a part of the reclaimed water 12 is sent back to the inlet of the
reverse osmosis membrane device 13 through the cleaning line L20, and the surface of
the reverse osmosis membrane 13a of the reverse osmosis membrane device 13 i5 s
cleaned.
Unless the flushing cleaning is performed, the amount of the scale deposition
on the reverse osmosis membrane 13a increases as illustrated in the solid line B,
resulting in the large decrease in the permeation flux as illustrated in the solid line A.
10 According to the present embodiment, it is possible to detect the signs of the
scale deposition in advance because of the condition that facilitates the early scale
detection, as the salts are separated at the detection membrane 15a from the
concentrated water for detection 17, in which the salt has been rapidly concentrated to
yield a high scale component concentration.
15 As a result, the reverse osmosis membrane 13a of the reverse osmosis
membrane device 13 in the main line can be cleaned regularly before the scale
deposition, and steady water treatment can be provided.
In the present embodiment, the presence or absence of the scale component is
detected by monitoring the flow rate of the reclaimed water for detection 16 using a
20 flow meter for detection 22, but the present invention is not limited to this
embodiment. For example, as illustrated in FIG. 3, the presence or absence of the
scale deposition may be detected by monitoring the pressure change using a pressure
gauge for detection 23 disposed in the branched line L14.
Alternatively, the presence or absence of the scale deposition may be detected
25 by monitoring turbidity of the concentrated water for detection 17, using a turbidity
meter 24 disposed in the separation line for the concentrated water for detection L16,
where the concentrated water for detection 17 is separated.
Alternatively, an electric conductivity meter may be disposed, instead of the
turbidity meter 24, to monitor the change in electrical conductivity to detect the
30 degree of turbidity.
The detection membrane 15a of the scale detection unit 15 may be discarded
every time or may be recycled after regeneration.
According to the present embodiment, by including a scale detection unit 15
including the detection membrane 15a, which is a reverse osmosis membrane, crystal
35 deposition on the reverse osmosis membrane 13a of the reverse osmosis membrane
device 13 is detected in advance, when the water to be treated 11 is treated using the
reverse osmosis membrane device 13 in the main line.
Embodiment 2
10
Next, a cooling tower discharge water reclamation treatment system pertaining
to Embodiment 2 will be described. FIG. 5 is a schematic diagram of a scale detection
device of the concentrating device.
As illustrated in FIG. 5, the scale detection device of the concentrating device
pertaining to the present Embodiment, based on Embodiment 1, further includes 5 a
second booster pump P2 disposed in the branched line L14 to increase the water
pressure of the branched concentrated water 14 and feed the branched concentrated
water 14 to the detection membrane 15a to accelerate the concentration.
By this configuration, the permeation flux, which permeates through the
10 detection membrane 15a, is increased, and the concentration ratio of the concentrated
water for detection 17 may be improved. As a result, the scale deposition can be
detected at an earlier stage than in Embodiment 1, due to the accelerated scale
deposition at the detection membrane 15a.
If the pressure of the water to be treated 11 introduced to the reverse osmosis
15 membrane device 13 is 1 MPa, for example, the pressure of the concentrated water 14
may be increased by 4 MPa approximately, so that the permeation flux, which
permeates through the detection membrane 15a, may be increased.
Alternatively, an adjustment valve V11 may be disposed in the separation line
for the concentrated water for detection L16 and the branched water flow rate of the
20 concentrated water for detection 17 may be reduced by throttling the adjustment valve
V11 to accelerate the concentration.
Embodiment 3
Next, a cooling tower discharge water reclamation treatment system pertaining
to Embodiment 3 will be described. FIG. 6 is a schematic diagram of a scale detection
25 device of the concentrating device.
As illustrated in FIG. 6, the scale detection device of the concentrating device
pertaining to the present embodiment, based on Embodiment 1, further includes a
circulation line L17, which feeds back a part of the concentrated water for detection 17
from the separation line for the concentrated water for detection L16 to the branched
30 line L14. Thus, the concentrated water for detection 17 can be returned to the inlet -side
of the detection membrane 15a again.
In the present embodiment, because the part of the concentrated water for
detection 17 is returned to the inlet-side of the detection membrane 15a, the
concentrated water 14 with a greater concentration ratio is supplied to the detection
35 membrane 15a compared to the case where the part of the concentrated water for
detection 17 is not circulated for reuse as in Embodiment 1. As a result, the
concentration ratio of the concentrated water 14 may be greater compared to the case
in which the part of the concentrated water for detection 17 is not circulated for reuse .
11
Thus, deposition of calcium sulfate can be detected at an earlier stage than in
Embodiment 1, due to the accelerated deposition of calcium sulfate.
Embodiment 4
Next, a cooling tower discharge water reclamation treatment system pertaining
to Embodiment 4 will be described. FIG. 7 is a schematic diagram of a scale detectio5 n
device of the concentrating device.
As illustrated in FIG. 7, the scale detection device of the concentrating device
pertaining to the present embodiment, based on Embodiment 1, includes a heat
exchange device 25 disposed in a branched line L14 so that the temperature of the
10 concentrated water 14 may be changed.
FIG. 8 is a graph illustrating the temperature dependence of calcium sulfate
solubility.
As illustrated in FIG. 8, the solubility of calcium sulfate is dependent of
temperature. Specifically, the solubility is at maximum at approximately 40 degrees C
15 and the solubility decreases at lower or higher temperatures. Hence, the temperature
of the concentrated water 14 is adjusted by a heat exchange device 25 so that the
deposition of the calcium sulfate is accelerated.
Specifically, when the concentrated water 14 at the temperature of 30° is
separated, for example, the temperature of the concentrated water 14 can be reduced
20 by 10 degrees C approximately by the heat exchange device 25.
Thus, reduction of the solubility of calcium sulfate due to the temperature
change in the concentrated water 14 can accelerate the deposition of calcium sulfate .
As a result, deposition of calcium sulfate can be detected at an earlier stage than in
Embodiment 1, due to the increased deposition ratio of calcium sulfate in the
25 concentrated water 14 and the accelerated deposition of calcium sulfate compared to
the case in which the concentrated water 14 is not cooled.
As illustrated in FIG. 8, the solubility may decrease at higher temperatures
compared to the case in which the temperature of the concentrated water 14 is
decreased by the heat exchange device 25. However, when a polymer reverse osmosis
30 membrane is used for the detection membrane 15a, the upper temperature limit for
acceptable durability of the membrane is at around 40°.
Thus, it is preferable to decrease the temperature when a conventional reverse
osmosis membrane with poor thermal durability is used for the detection membrane
15a.
35 Embodiment 5
Next, a cooling tower discharge water reclamation treatment system pertaining
to Embodiment 5 will be described. FIG. 9 is a schematic diagram of a scale detection
device of the concentrating device.
12
As illustrated in FIG. 9, the scale detection device of the concentrating device
pertaining to the present embodiment, based on Embodiment 1, aims to cancel out the
effect of the scale inhibitor by supplying an acid 27a from an acid supplying device 27
to the concentrated water 14 that exits from the reverse osmosis membrane device 13
when the scale inhibitor 26a is supplied to the water to be treated 11 from the scal5 e
inhibitor supplying unit 26 to inhibit the scale deposition on the reverse osmosis
membrane 13a of the reverse osmosis membrane device 13, before the water to be
treated 11 is introduced to the reverse osmosis membrane device 13.
Here, the scale inhibitor 26a is an agent having a function of suppressing the
10 creation of crystal nuclei in the water to be treated 11 and suppressing crystal growth
by being adsorbed to the surface of crystal nuclei contained in the water to be treated
11 (seed crystals, deposited small-diameter scales in excess of the saturated
concentration, or the like). In addition, the scale inhibitor also has a function of
dispersing particles in the water to be treated such as deposited crystals (function of
15 preventing aggregation). Examples of the scale inhibitor 26a include phosphonic
acid-based scale inhibitors, polycarboxylic acid-based scale inhibitors, and mixtures
thereof. A specific example of the scale inhibitor is FLOCON 260 (trade name,
produced by BWA).
As described above, the scale inhibitor 26a is an agent to suppress the creation
20 of scales on the surface of the reverse osmosis membrane 13a in the main line and to
prevent clogging of the membrane. By supplying the acid 27a to decrease the pH, the
effect of the scale inhibitor can be canceled out.
In the present embodiment, sulfuric acid is supplied as the acid 27a from the
acid supplying unit 27 to the concentrated water 14, to maintain the pH thereof at 4 or
25 less. As a result, the effect of the scale inhibitor 26a is canceled out, and the
deposition of calcium sulfate is accelerated. Thus, it is possible to detect the scale
deposition at the earlier stage than the case in which the acid 27a is not supplied.
Embodiment 6
FIG. 10 is a schematic diagram of a water reclamation treatment system of
30 Embodiment 6. As illustrated in FIG. 10, a water reclamation treatment system 100A
pertaining to the present embodiment includes: a first scale inhibitor-supplying unit
51A which supplies a scale inhibitor 26a to the water to be treated 11, such as cooling
tower discharge water and mine wastewater; a first pH-adjusting unit 54A which
adjusts a pH of the water to be treated 11, to which the scale inhibitor 26a has been
35 supplied, using a pH-adjusting agent 53; a first reverse osmosis membrane device 13A
which is provided downstream of the first pH-adjusting unit 54A, and removes salts in
the water to be treated 11 and separates the water into first reclaimed water 12A and
first concentrated water 14A; and a first crystallizing unit 63, which includes a first
13
crystallizing tank 61 which is provided downstream of the first reverse osmosis
membrane device 13A and crystallizes calcium sulfate 60 from the first concentrated
water 14A, and a seed crystal-supplying unit 62 which supplies seed crystals of
calcium sulfate (calcium sulfate seeds) 60a to the first crystallizing tank 61. In the FIG.
10, the reference sign L15A denotes the discharge line for the reclaimed water fo5 r
detection, which discharges the first reclaimed water for detection 16A; L16A denotes
the separation line for the concentrated water for detection, which separates the first
concentrated water for detection 17A; L15B denotes the discharge line for the
reclaimed water for detection, which discharges the second reclaimed water for
10 detection; and L16B denotes the separation line for the concentrated water for detection,
which separates the second concentrated water for detection 17B.
In the present embodiment, the scale inhibitor 26a is supplied from the first
scale inhibitor-supplying unit 51A to the water to be treated 11. Subsequently, the pH
of the water to be treated 11 supplied to the first reverse osmosis membrane device
15 13A is adjusted to not less than 10, preferably not less than 10.5, and more preferably
not less than 11. The pH gauge 55A measures the pH of the water to be treated 11 at
the inlet of the first reverse osmosis membrane device 13A. The controller that is not
illustrated in the figure adjusts the degree of opening of the valve and inputs alkali
from the tank of the first pH-adjusting unit 54A into the water to be treated 11 such
20 that the value measured by the pH gauge 55A reaches a predetermined pH control
value.
In the first reverse osmosis membrane device 13A, the pH-adjusted water to be
treated 11 is subjected to desalination treatment . The water passed through the reverse
osmosis membrane 13a is recovered as a first reclaimed water 12A. The ions and the
25 scale inhibitor 26a contained in the water to be treated 11 cannot pass through the
reverse osmosis membrane 13a. Therefore, in the unpermeated side of the reverse
osmosis membrane 13a, a first concentrated water 14A having a high ion
concentration is present.
By means of the first desalinating step, silica is contained in the first
30 concentrated water 14A in a dissolved state in the water to be treated. Even if calcium
sulfate and calcium carbonate in the first concentrated water 14A are concentrated at
their respective saturation concentrations or higher, scale generation is suppressed by
the calcium scale inhibitor used as the scale inhibitor 26a.
When Mg2+ is contained in the water to be treated 11, the Mg2+ concentration
35 contained in the first concentrated water 14A is increased by means of the first
desalinating step. However, generation of magnesium hydroxide scale is suppressed
by magnesium scale inhibitor used as the scale inhibitor 26a. The first concentrated
water 14A is fed toward the crystallizing tank 61.
14
The first concentrated water 14A discharged from the first reverse osmosis
membrane device 13A is stored in the crystallizing tank 61. The calcium sulfate seed
crystals 60a from the seed crystal-supplying unit 62 is added to the first concentrated
water 14A in the crystallizing tank 61.
Since the pH of the first concentrated water 14A from the first reverse osmosi5 s
membrane device 13A is not less than 10, calcium sulfate 60 is in the dissolved state
in the presence of calcium scale inhibitor. However, when enough seed crystals 60a
are present, the calcium sulfate 60 crystallizes with the seed crystals 60a as nuclei
even if scale inhibitor is present.
10 Therefore, calcium sulfate 60, which has been grown from the seed crystals 60a
to a large diameter (for example, particle size not less than 10 μm) precipitates on the
bottom of the crystallizing tank 61. The precipitated calcium sulfate 60 is discharged
from the bottom of the crystallizing tank 61.
The first concentrated water 14A, from which calcium sulfate 60 was separated,
15 is fed to the downstream second reverse osmosis membrane device 13B. Water that
passes through the downstream second reverse osmosis membrane device 13B is
recovered as the second reclaimed water 12B. The second concentrated water 14B of
the second reverse osmosis membrane device 13A is discharged outside the system.
By disposing the second reverse osmosis membrane device 13B, it becomes
20 possible to further recover the second reclaimed water 12B from the first concentrated
water 14A, from which calcium sulfate 60 has been removed, after being treated by
the first reverse osmosis membrane device 13A. Thus, the amount of reclaimed water
12 is the total of the first reclaimed water 12A and the second reclaimed water 12B,
and the water recovery rate of the reclaimed water is improved. Furthermore, to
25 prevent scale deposition, scale inhibitor 26a is supplied from a second scale inhibitor -
supplying unit 51B, and pH adjustment in this case is controlled by a second pHadjusting
unit 54B. The control method is similar to that used for the first scale
inhibitor-supplying unit 51A and the first pH-adjusting unit 54A.
In the cooling tower discharge water reclamation treatment systems 100A of the
30 present embodiment, the ions are concentrated in the first reverse osmosis membrane
device 13A, while calcium sulfate 60 is removed in the crystallizing tank 61. For this
reason, the first concentrated water 14A that flows into the downstream second reverse
osmosis membrane device 13B has a lower ion concentration than that of before
treatment. Thus, the osmotic pressure in the second reverse osmosis membrane device
35 13B located downstream becomes lower, and the required power is reduced.
A water reclamation treatment system 100A pertaining to the present
embodiment includes: a second scale inhibitor-supplying unit 51B which supplies a
scale inhibitor 26a to the first concentrated water 14A from which calcium sulfate has
15
been separated; a second pH-adjusting unit 54B which adjusts a pH of the first
concentrated water 14A, to which the scale inhibitor 26a has been supplied, using a
pH-adjusting agent 53; and a second reverse osmosis membrane device 13A which is
provided downstream of the pH-adjusting unit 54B and further removes salts in the
first concentrated water 14A and separates the water into second reclaimed water 125 B
and second concentrated water 14B.
This system includes: the first scale detection unit 15A which includes a
branched line L14A branched from the separation line L13A of the first concentrated
water 14A from the first reverse osmosis membrane device 13A and the detection
10 membrane 15a; and the second scale detection unit 15B which includes a branched
line L14B branched from the separation line L13B of the second concentrated water 14B
from the second reverse osmosis membrane device 13B and the detection membrane
15b, separately. Thus, scale deposition in the first reverse osmosis membrane device
13A and the second reverse osmosis membrane device 13B can be detected in advance,
15 and the stable water reclamation treatment is provided continuously.
At the first scale detection unit 15A, the first concentrated water 14A is
separated into the first reclaimed water for detection 16A and the first concentrated
water for detection 17A by the detection membrane 15a, so that the absence or
presence of scale component deposition in the first concentrated water 14A can be
20 detected. Likewise, at the second scale detection unit 15B, the second concentrated
water 14B is separated into the second reclaimed water for detection 16B and the
second concentrated water for detection 17B by the detection membrane 15b, so that
the absence or presence of scale component deposition in the second concentrated
water 14B can be detected.
25 The first scale detection unit 15A and the second scale detection unit 15B can
detect the crystal deposition on the first reverse osmosis membrane 13a and the second
reverse osmosis membrane 13b in advance by detecting the crystal deposition on the
first reverse osmosis membrane 13a in the first reverse osmosis membrane device 13A
and on the second reverse osmosis membrane 13b of the second reverse osmosis
30 membrane device 13B in advance, respectively, using the configurations of the
Embodiments 1 to 5, described above.
Thereby, when calcium sulfate, which is the scale component, is present in the
water to be treated 11 at an abnormally high concentration, it is possible to perform
flushing cleaning to avoid troubles caused by the scale deposition on the reverse
35 osmosis membrane in the main line, upon detecting the signs of scale deposition on
the first and the second reverse osmosis membrane, 13a and 13b, of the first and the
second reverse osmosis membrane device, 13A and 13B in the main line.
16
Also, as in the cooling tower discharge water reclamation treatment system
100B illustrated in FIG. 11, a liquid cyclone 71 as a calcium sulfate separating means
may be provided downstream of the crystallizing tank 61, such that calcium sulfate 60
and supernatant water are separated in the liquid cyclone 71, and the separated
calcium sulfate 60 is dehydrated by removing a separated liquid 73 using 5 a
dehydrating device 72, thereby reliably separating the calcium sulfate 60.
Reference Signs List
11 Water to be treated
10 12 Reclaimed water
13a Reverse osmosis membrane
13 Reverse osmosis membrane device
14 Concentrated water
15a Detection membrane
15 15 Scale detection unit
16 Reclaimed water for detection
17 Concentrated water for detection

We Claim:
1. A scale detection device of a concentrating device, the scale detection device
comprising:
a concentrating device including a filtering membrane concentrating sal5 t
in a water to be treated containing at least calcium sulfate to obtain reclaimed
water; and
a scale detection unit disposed in a branched line branched from a
concentrated water line discharging concentrated water having a high
10 concentration of salt, the scale detection unit further concentrating salt in the
concentrated water to obtain reclaimed water for detection, and including a
detection membrane detecting the absence or presence of scale component
deposition in the concentrated water.
15 2. The scale detection device of a concentrating device according to claim 1,
further comprising
a booster pump to increase a pressure of the concentrated water supplied
to the detection membrane in the scale detection unit.
20 3. The scale detection device of a concentrating device according to claim 1 or 2,
further comprising
a valve that reduces an amount of the concentrated water for detection
separated at the detection membrane.
25 4. The scale detection device of a concentrating device according to claim 3,
further comprising
a circulation line that feeds the concentrated water for detection
separated at the detection membrane back to an inlet of the detection membrane.
30 5. The scale detection device of a concentrating device according to any one of
claims 1 to 4, further comprising
a heat exchange device that performs heat exchange on the concentrated
water supplied to the scale detection unit.
35 6. The scale detection device of a concentrating device according to any one of
claims 1 to 5, wherein
an effect of a scale inhibitor is canceled out by supplying an acid to the
concentrated water exiting from the concentrating device,
18
when scale deposition on a filtering membrane of the concentrating
device is prevented by supplying the scale inhibitor to the water to be treated
before introduction to the concentrating device.
7. The scale detection device of a concentrating device according to any one o5 f
claims 1 to 6, wherein
the scale component is calcium sulfate and the detection membrane is a
reverse osmosis membrane.
10 8. The scale detection device of a concentrating device according to any one of
claims 1 to 7, wherein
the water to be treated is any one of mine wastewater, blowdown water
of a power plant cooling tower, accompanying water during machining using
oil or gas, saline water, and industrial waste water.
15
9. A scale detection method of a concentrating device, the scale detection method
comprising:
a salt concentrating step of concentrating salt in water to be treated
containing at least calcium sulfate by a filter membrane and separating the
20 water to be treated into reclaimed water and concentrated water;
and a scale detection step of obtaining reclaimed water for detection by
further concentrating salt in a portion of separated and salt -concentrated water,
and detecting the absence or presence of scale component deposition in the
concentrated water.
25
10. The scale detection method of a concentrating device according to claim 9,
wherein
a pressure of the concentrated water supplied to a detection membrane in
the scale detection step is increased to improve a concentration ratio.
30
11. The scale detection method of a concentrating device according to claim 9 or
10, wherein
an amount of concentrated water for detection separated at the detection
membrane is reduced to improve the concentration ratio.
35
12. The scale detection method of a concentrating device according to any one of
claims 9 to 11, wherein
19
the concentrated water for detection separated at the detection membrane
is sent back to an inlet of the detection membrane to improve the concentration
ratio.
13. The scale detection method of a concentrating device according to any one o5 f
claims 9 to 12, wherein
the concentrated water supplied to the scale detection unit is subjected to
heat exchange to increase the amount of scale deposition.
10 14. The scale detection method of a concentrating device according to any one of
claims 9 to 13, wherein
an effect of a scale inhibitor is canceled out by supplying an acid to the
concentrated water exiting from the concentrating device,
when scale deposition on a filtering membrane of the concentrating device is prevented by supplying the scale inhibitor to the water to be treated
before introduction to the concentrating device.
15. A water reclamation treatment system comprising:
a first scale inhibitor-supplying unit supplying a scale inhibitor to water
20 to be treated containing a calcium sulfate component;
a first pH-adjusting unit adjusting a pH of discharged water to which the
scale inhibitor has been supplied using a pH-adjusting agent;
a first concentrating device provided downstream of the first pHadjusting
unit, the first concentrating device concentrating salt in the water to
25 be treated and separating the water to be treated into first reclaimed water and
first concentrated water;
a crystallizing tank provided downstream of the first concentrating
device, the crystallizing tank crystallizing calcium sulfate from the first
concentrated water;
30 a first scale detection unit provided in a first branch line branched from
a first concentrated water line discharging the first concentrated water with salt
therein concentrated at the first concentrating device, the first scale detection
unit obtaining a first reclaimed water for detection by further concentrating salt
from the first concentrated water and including a first detecting membrane
35 detecting the absence or presence of scale component deposition in the
concentrated water. 16. Tlie water reclaination treatment system according to claiin 15, furtlier
comprising:
a second scale inliibitor-supplying unit supplying a scale inhibitor to tlie
first coiicentrated water, calciuni sulfate having been separated from the first
colicelitrated water;
a second pH-adjusting unit adjusting a pH of the first coiicentrated water,
the scale inhibitor having been supplied to tl~efi rst concentrated water;
a second coiicentratiiig device provided dowllstream of the second pHadjusting
unit, tlie second concentrating device concentratiilg salt in the first
coiicentrated water aiid separating the first concentrated water into second
reclaimed water and second coiicentrated water; aiid
a second scale detection unit provided in a second branch line branched
from a second concentrated water line discharging the second concentrated
water wit11 salt thereill coiiceiltrated at the secoild concentrating device, the
second scale detection unit obtaining a second reclaimed water for detection by
further coilcentrating salt from the second coiicentrated water and including a
second detecting membrane detecting the absence or presence of scale
component deposition in the secoiid concentrated water.