Field
The present invention relates to a filtration treatment
system of raw water which desalinates, for example, seawater,
and a method of washing a filtration device.
5 Background
In a desalination treatment system in which
desalination is performed by using, for example, seawater as
raw water, pretreatment of seawater to be supplied to the
desalination treatment device is performed. As a filtration
10 treatment device for this pretreatment, a filtration device
to remove impurities is installed on the upstream side of
the desalination treatment device. As this filtration device,
for example, a filtration device (DMF: Dual Media Fileter)
in which a plurality of granular filtration layers with
15 silica sand, anthracite or the like are layered is used.
Turbidity causing materials (SS) and the like are
removed by filtering seawater by using this filtration
device. In the case in which water-soluble organic
substances (biological polysaccharides and the like) are
20 contained in seawater, water-soluble organic substances are
also removed through adsorption to the surface of the filter
medium installed in the filtration device and adsorption to
the floc formed by, for example, a flocculant such as iron
chloride.
25 However, the pressure loss increases due to clogging
when the filter medium is contaminated by filtration, and in
the related art, backwashing of the filtration device is
thus regularly performed to remove dirt and to recover the
performance.
30 Here, seawater (concentrated water concentrated by the
desalination device) is usually used upon backwashing of the
filtration device. Here, with regard to removal of turbidity
causing materials in which inorganic substance are mostly
3
composed, there is not a serious problem even when seawater
is used since it is possible to remove the fine particles
attached to the filter medium by peeling off them through a
physical action such as an abrupt flow at the time of
5 backwashing, or the like.
However, in the case of containing water-soluble
organic substances in raw water, the adsorption amount of
the water-soluble organic substances to the filter medium or
the like to be adsorbed to the floc of iron chloride or the
10 surface of the filter medium is determined so as to be in
the adsorption equilibrium with the concentration thereof in
the liquid in principle. Water-soluble organic substances to
be the target of removal are originally present in seawater,
and the adsorption amount thereof thus gradually increases
15 along with the lapse of operation time and increases until
it reaches the equilibrium adsorption amount with respect to
the concentration thereof in seawater as long as seawater is
used for backwashing.
In addition, at the time of operating the desalination
20 treatment, the organic substances adsorbed to the flocs of
iron chloride and the like are removed in advance on the
upstream side to be introduced into the filtration device
and the concentration of organic substances in seawater
decreases, thus the organic substances adsorbed to the
25 filter medium are contrarily desorbed at the time of
backwashing and there is also a problem that the removal
efficiency does not increase. In other words, a certain
amount of water-soluble organic substances always remain as
long as backwashing is performed by using seawater.
30 In view of the above, in the related art, it is
proposed that it is effective to use fresh water that is
permeated water manufactured by the desalination device
instead of seawater (concentrated water) when performing
4
backwashing in a case in which the pressure loss increases
before and after the filtration device and clogging of the
filter medium and the like are caused (Patent Literature 1).
Citation List
5 Patent Literature
Patent Literature 1: Japanese Laid-open Patent
Publication No. 61-274714
Summary
Technical Problem
10 However, in the case of carrying out the backwashing
proposed in Patent Literature 1, there is a problem that the
yield of fresh water of the product decreases since a large
amount of fresh water that is permeated water thus
manufactured is consumed at the time of backwashing.
15 Accordingly, it is significantly desired to develop a
method of washing a filtration device, which is capable of
decreasing the amount of fresh water of the product used as
much as possible when performing washing of the filtration
device.
20 In view of the above problems, an object of the present
invention is to provide a filtration treatment system of raw
water and a method of washing a filtration device, which are
capable of, for example, decreasing the amount of fresh
water of the product used as much as possible when
25 performing washing of the filtration device.
The first embodiment of the invention to solve the
problem is a filtration treatment system of raw water
including a raw water supply line that is configured to
supply raw water, a filtration device that is provided on
30 the raw water supply line and configured to filter
impurities in the raw water, a separation device that is
provided on a rear side of the filtration device and
5
equipped with a separation membrane to separate filtered raw
water into permeated water and concentrated water in which a
solute including a salt or fine particles are enriched, an
organic substance monitoring device that is provided on
5 either front or rear or both front and rear of the
filtration device and configured to monitor an amount of an
organic substance in the raw water, and a control device
that is configured to execute backwashing of the filtration
device with the permeated water as backwashing water in a
10 case in which the amount of the organic substance in the raw
water is determined to exceed a reference value as a result
of monitoring by the organic substance monitoring device.
According to the present invention, it is possible to
efficiently perform recovery of the filtration performance
15 by removing the organic substances of the filtration device
while suppressing the amount of permeated water used since
permeated water is not always used at the time of
backwashing by using permeated water for backwashing in a
case in which the amount of organic substances exceeds the
20 reference value.
The second embodiment is the filtration treatment
system of raw water according to the first embodiment,
wherein the control device executes backwashing of the
filtration device with the raw water or the concentrated
25 water as the backwashing water in a case in which the amount
of the organic substance in the raw water is determined to
be equal to or less than the reference value as a result of
monitoring by the organic substance monitoring device.
According to the present invention, it is possible to
30 achieve a decrease in amount of permeated water used when
carrying out backwashing by usually using raw water or
concentrated water in a case in which the amount of organic
substances in raw water is equal to less than the reference
6
value and by using permeated water for backwashing in a case
in which the amount of organic substances in raw water
exceeds the reference value.
The third embodiment is a filtration treatment system
5 of raw water including a raw water supply line that is
configured to supply raw water, a filtration device that is
provided on the raw water supply line and configured to
filter impurities in the raw water, a separation device that
is provided on a rear side of the filtration device and
10 equipped with a separation membrane to separate filtered raw
water into permeated water and concentrated water in which a
solute including a salt or fine particles are enriched, an
organic substance monitoring device that is provided on
either front or rear or both front and rear of the
15 filtration device and configured to monitor an amount of an
organic substance in the raw water, and a control device
that is configured to execute backwashing of the filtration
device with the concentrated water as backwashing water in a
case in which the amount of the organic substance in the raw
20 water is determined to be equal to or less than a reference
value as a result of monitoring by the organic substance
monitoring device and execute backwashing of the filtration
device with the permeated water as the backwashing water in
a case in which the amount of the organic substance in raw
25 water is determined to exceed the reference value as a
result of monitoring by the organic substance monitoring
device.
According to the present invention, it is possible to
achieve a decrease in amount of permeated water used when
30 carrying out backwashing by usually using concentrated water
in a case in which the amount of organic substances in raw
water is equal to less than the reference value and by using
permeated water for backwashing in a case in which the
7
amount of organic substances in raw water exceeds the
reference value.
The fourth embodiment is the filtration treatment
system of raw water according to any one of the first to
5 third embodiments, wherein the organic substance monitoring
device includes an organic substance concentration
measurement device configured to measure a concentration of
the organic substance in the raw water.
According to the present invention, it is possible to
10 measure the confirmation of the amount of organic substances
in the raw water by the concentration of organic substances.
The fifth embodiment is the filtration treatment system
of raw water according to any one of the first to fourth
embodiments, wherein the organic substance monitoring device
15 is provided on a rear side of the filtration device and
includes a turbidity measuring device configured to measure
a turbidity in raw water from the filtration device.
According to the present invention, it is possible to
perform the confirmation of the amount of organic substances
20 in the raw water by a turbidity measuring device which
measures the turbidity.
The sixths embodiment is the filtration treatment
system of raw water according to any one of the first to
fifth embodiments, wherein the control device executes
25 backwashing of the filtration device with the permeated
water at every set period.
According to the present invention, the organic
substances on the filtration layer is removed and the
accumulation of organic substances is suppressed by
30 performing backwashing by using permeated water at every set
period of time since the amount of organic substances
adsorbed to the filtration layer of the filtration device
gradually increases even in a case in which the amount of
8
organic substances in the raw water does not remarkably
increase.
The seventh embodiment of the invention is the
filtration treatment system of raw water according to any
5 one of the first to sixth embodiments, including a plurality
of the separation devices, wherein the plurality of
separation devices are connected to permeated water lines to
discharge the permeated water in series, the filtration
device is connected to a permeated water line of permeated
10 water to be discharged from the separation device provided
on an upstream side of the separation device at a final
stage, and the control device performs backwashing of the
filtration device with permeated water to be discharged from
the separation device provided on the upstream side of the
15 separation device at the final stage in a case of executing
backwashing of the filtration device with the permeated
water.
According to the present invention, in the case of
improving the separation performance by installing the
20 separation device equipped with a separation membrane to
obtain permeated water at a plurality of stages and in
series, it is possible to obtain a sufficient backwashing
effect without significantly decreasing the treatment
efficiency of the separation plant by using permeated water
25 from a separation device that is provided on the upstream
side of the separation device at the final stage and
equipped with a separation membrane on the leading side
having a relatively low separation rate instead of using
permeated water from the separation device at the final
30 stage as the permeated water to be used for backwashing.
The eights embodiment of the invention is the
filtration treatment system of raw water according to any
one of the first to seventh embodiments, wherein the
9
filtration device includes filtration device main body that
has a plurality of filtration layers layered in a vertical
axis direction in an interior, a supply line that is
configured to supply the raw water from a top portion side
5 of the filtration device main body, a filtered raw water
supply line that is configured to discharge filtered raw
water filtered from a bottom portion side of the filtration
device main body and supply the filtered raw water to the
separation device, a backwashing water introduction line
10 that is configured to introduce backwashing water from the
bottom portion side of the filtration device main body, an
overflow line that is configured to collect the backwashing
water overflowed from a top portion side of the filtration
layers of the filtration device main body, and a backwashing
15 water discharge line that is configured to discharge the
backwashing water of the filtration device main body from
the bottom portion side of the filtration device main body.
According to the present invention, it is possible to
decrease the concentration of organic substances in the
20 washing water and to improve the washing effect when the
interior of the filtration device is washed by once
discharging the backwashing water contaminated with the
organic substances in the filtration device.
The ninth embodiment of the invention is the filtration
25 treatment system of raw water according to any one of the
first to eighth embodiment, wherein the control device
executes backwashing by carrying out a treatment in which
the backwashing water discharge line is opened, the
backwashing water in an interior of the filtration device
30 main body is drained through the backwashing water discharge
line, then the backwashing water discharge line is closed,
and the backwashing water is introduced into the interior of
the filtration device main body through the backwashing
10
water introduction line at least once or more in a case in
which the control device determines to execute backwashing
of the filtration device.
According to the present invention, it is possible to
5 decrease the concentration of organic substances in the
washing water and to improve the washing effect when the
interior of the filtration device is washed by draining the
backwashing water remaining in the interior of the
filtration device main body and then supplying backwashing
10 water.
The tenth embodiment of the invention is the filtration
treatment system of raw water according to any one of the
first to ninth embodiments, wherein the control device
executes backwashing with the permeated water after
15 detecting that the concentration of the organic substance is
decreased to a concentration equal to or less than a
threshold concentration lower than a predetermined
concentration in a case in which a state in which the
concentration of the organic substance exceeds the
20 predetermined concentration continues for a predetermined
time or longer through monitoring by the organic substance
monitoring device.
According to the present invention, the filtration
layer of the filtration device is contaminated immediately
25 after the operation is restarted after backwashing is
performed and the backwashing operation is immediately
required even if the backwashing operation is carried out in
a state in which the concentration of organic substances in
raw water is still high. Hence, it is possible to save the
30 amount of permeated water used and to perform effective
washing by continuously performing the operation as it is
even though the concentration of organic substances in raw
water exceeds a predetermined value and performing
11
backwashing by using the permeated water after the
concentration of organic substances in the raw water is
decreased.
The eleventh embodiment of the invention is a method of
5 washing a filtration device that removes a suspended solid
in raw water, the method including an organic substance
monitoring step of monitoring an amount of an organic
substance in the raw water, and a permeated water
backwashing step of backwashing the filtration device by
10 using permeated water obtained by removing a solute
including a salt or fine particles from the filtered raw
water as backwashing water in a case in which an amount of
an organic substance in the raw water monitored in the
organic substance monitoring step exceeds a reference value.
15 According to the present invention, it is possible to
efficiently perform recovery of the filtration performance
by removing the organic substances of the filtration device
while suppressing the amount of permeated water used since
permeated water is not always used at the time of
20 backwashing by using permeated water for backwashing in a
case in which the amount of organic substances exceeds the
reference value.
The twelfth embodiment is a method of washing a
filtration device that is configured to remove a suspended
25 solid in raw water, the method including an organic
substance monitoring step of monitoring an amount of an
organic substance in the raw water, and a step of performing
backwashing of the filtration device by using concentrated
water as backwashing water in a case in which an amount of
30 an organic substance in the raw water monitored in the
organic substance monitoring is determined to be equal to or
less than a reference value and performing backwashing of
the filtration device by using permeated water as the
12
backwashing water in a case in which the amount of the
organic substance in the raw water is determined to exceed
the reference value as a result of monitoring by the organic
substance monitoring device.
5 According to the present invention, it is possible to
achieve a decrease in amount of permeated water used when
carrying out backwashing by usually using concentrated water
in a case in which the amount of organic substances in raw
water is equal to or less than the reference value and by
10 using permeated water for backwashing in a case in which the
amount of organic substances in raw water exceeds the
reference value.
Advantageous Effects of Invention
According to the present invention, it is possible to
15 efficiently perform recovery of the filtration performance
by removing the organic substances of the filtration device
while suppressing the amount of permeated water used since
permeated water is not always used at the time of
backwashing by using permeated water for backwashing in a
20 case in which the amount of organic substances exceeds the
reference value.
Brief Description of Drawings
FIG. 1 is a schematic diagram of a desalination
treatment system according to a first embodiment.
25 FIG. 2 is a schematic diagram of another desalination
treatment system according to the first embodiment.
FIG. 3-1 is a diagram illustrating the relation of the
pressure loss and the concentration of organic substances
with the elapsed days.
30 FIG. 3-2 is a diagram illustrating the relation of the
pressure loss and the concentration of organic substances
with the elapsed days.
13
FIG. 3-3 is a diagram illustrating the relation of the
pressure loss and the concentration of organic substances
with the elapsed days.
FIG. 4 is a schematic diagram of a desalination
5 treatment system according to a fourth embodiment.
FIG. 5-1 is a diagram illustrating an operation state
of a filtration device of the fourth embodiment.
FIG. 5-2 is a diagram illustrating an operation state
of a filtration device of the fourth embodiment.
10 FIG. 5-3 is a diagram illustrating an operation state
of a filtration device of the fourth embodiment.
FIG. 6 is a schematic diagram of a desalination
treatment system according to a fifth embodiment.
Description of Embodiments
15 Hereinafter, the present invention will be described in
detail with reference to the drawings. Incidentally, the
present invention is not limited to the following
embodiments. In addition, the constituent elements in the
following embodiments include those that can easily be
20 assumed by those skilled in the art, those that are
substantially the same, and so-called equivalents.
Furthermore, the constituent elements disclosed in the
following embodiments can be appropriately combined.
First embodiment
25 Filtration treatment systems of raw water according to
embodiments of the present invention will be described with
reference to the drawings. Hereinafter, a desalination
treatment system will be described by taking a desalination
device equipped with a separation membrane which enriches a
30 solute such as a salt or fine particles as an example of a
separation device in the present embodiment. FIG. 1 is the
schematic diagram of a desalination treatment system
14
according to a first embodiment. FIG. 2 is the schematic
diagram of another desalination treatment system according
to the first embodiment.
As illustrated in FIG. 1, a desalination treatment
5 system 10A according to the present embodiment is equipped
with a raw water supply line L10 that supplies raw water 11,
a filtration device 12 that is provided on the raw water
supply line L10 and filters impurities in the raw water 11,
a salt concentrator 23 that is provided on a rear side of
10 the filtration device 12 and equipped with a separation
membrane 23a to separate filtered raw water 11A into
permeated water 21 and concentrated water 22 in which a
solute including a salt or fine particles are enriched, and
an outlet side organic substance monitoring device 25A that
15 is provided on a rear side of the filtration device 12 and
monitors an amount of an organic substance in the raw water
11, and a part 21a of the permeated water 21 is used for
backwashing of the filtration device 12 in a case in which
an amount of an organic substance in the raw water 11 is
20 determined to exceed a reference value (threshold value) as
a result of monitoring by this organic substance monitoring
device 25A.
In FIG. 1, a reference sign 31 illustrates a control
device, a reference sign 32 illustrates a flow path
25 switching unit, a reference sign L11 illustrates a filtered
raw water supply line which supplies the raw water 11A
filtered by the filtration device 12 to the salt
concentrator 23, a reference sign L12 illustrates a
permeated water line which discharges the permeated water 21
30 from the salt concentrator 23, a reference sign L13
illustrates a concentrated water line which discharges the
concentrated water 22 from the salt concentrator 23, a
reference sign L21 illustrates a backwashing water supply
15
line, a reference sign L22 illustrates a permeated water
branch line that is connected to the backwashing water
supply line L21 by the flow path switching unit 32 and
branches the part 21a of the permeated water 21 from the
5 permeated water line L12, and a reference sign L23
illustrates a concentrated water branch line that is
connected to the backwashing water supply line L21 by the
flow path switching unit 32 and branches a part 22a of the
concentrated water 22 from the concentrated water line L13,
10 respectively.
Here, the raw water 11 of the present invention is, for
example, water to be treated that is subjected to a water
treatment by the separation device 23 using a separation
membrane such as an ultrafiltration membrane (UF membrane),
15 a nanofiltration membrane (NF membrane), and a reverse
osmosis membrane (RO membrane), and examples thereof may
include seawater, mine wastewater, and cooling tower
wastewater.
The organic substance contained in this raw water 11 is
20 a water-soluble polymer, and it also includes, for example,
those caused by metabolism of microorganisms or the like,
and examples thereof may include neutral polysaccharides.
The molecular weight of this neutral polysaccharide is, for
example, 10,000 or more, but it may exceed, for example, one
25 million, or it may exceed, for example, ten millions. In
addition, there is also a case in which a polymer component
having a molecular weight of 10,000 or less is included.
Here, in the case of installing the outlet side organic
substance monitoring device 25A of the filtration device 12,
30 inorganic substance-based impurities are captured by the
filtration layers 12a and 12b of the filtration device 12,
and it is thus possible to ascertain the amount of organic
substance-based impurities.
16
In the filtration device 12, a carbon-based material
such as anthracite is used as the filtration layer 12a on
the upper layer side, a granular filter medium such as
silica sand is used as the filtration layer 12b of a lower
5 layer, the filtration layers 12a and 12b provided in a
filtration device main body 12c by being layered, and the
raw water 11 is introduced from a top portion 12d side and
passes through the filtration layers 12a and 12b so that the
suspended solids in the raw water 11 are captured.
10 Here, as the organic substance monitoring device of the
present invention, it is possible to use an organic
substance concentration meter which directly measures the
concentration of organic substances in the raw water 11 and
a turbidity measuring device which indirectly measures the
15 concentration of organic substances.
Examples of the organic substance concentration meter
may include a total organic carbon (TOC) meter, an
ultraviolet visible spectrophotometer, COD (Chemical Oxygen
Demand), and SFF (Soluble Fouling Factor. For example, see
20 Japanese Laid-open Patent Publication No. 2012-213676).
Incidentally, the measurement may be either online automatic
measurement or analysis by sampling.
Here, in the case of taking the TOC meter as an example,
it is desirable that the reference value of the TOC
25 concentration is, for example, 2 mg/kg or more, preferably
2.5 mg/kg or more, and more preferably 3 mg/kg or more.
Moreover, the part 21a of the permeated water 21 is
introduced from a bottom portion 12e of the filtration
device 12 as a backwashing water 30 to perform backwashing
30 when the concentration of organic substances is determined
to exceed the reference value as a result of measurement by
the organic substance concentration meter.
In other words, in the case of using an organic
17
substance concentration meter as the outlet side organic
substance monitoring device 25A, backwashing is carried out
by using the part 21a of the permeated water 21 as the
backwashing water 30 in a case in which the concentration of
5 organic substances in the raw water 11 exceeds the reference
value, but the control device 31 determines and switches the
flow path by the flow path switching unit 32 and backwashing
is carried out by using the part 22a of the concentrated
water 22 for backwashing of the filtration device 12 in a
10 case in which the concentration of organic substances is
equal to or less than the reference value.
In the related art, washing has been performed always
by using fresh water as the backwashing water 30 when
backwashing is carried out when there is an increase in
15 pressure loss in the filtration device.
In contrast, in the present embodiment, only in a case
in which the amount of organic substances in the raw water
11 is determined to exceed the reference value as a result
of measurement by the outlet side organic substance
20 monitoring device 25A, the control device 31 instructs the
flow path switching unit 32 to change the flow path so that
the fresh water of the part 21a of the permeated water 21
becomes the backwashing water 30, and the part 21a of the
permeated water 21 is introduced from the bottom portion 12e
25 of the filtration device 12, and backwashing is performed,
and it is thus possible to decrease the amount of permeated
water used when carrying out backwashing.
In addition, as the turbidity measuring device which
measures the amount of organic substances, it is preferable
30 to use the SDI value (Silt Density Index) prescribed in ASTM
D4189, the FI value (Fouling Index) prescribed in JIS K 3802,
and the like.
Here, in the case of measuring the amount of organic
18
substances by using a turbidity measuring device as the
outlet side organic substance monitoring device 25A, the
turbidity measuring device is required to be provided on the
rear side of the filtration device 12. This is because
5 there are turbidity causing materials which are mostly
composed of inorganic substances and turbidity causing
materials which are mostly composed of organic substances as
the turbidity causing materials which are contained in the
raw water 11. Moreover, the turbidity causing materials
10 which are mostly composed of inorganic substances removed by
introducing the raw water 11 into the filtration device 12,
and the turbidity causing materials in the filtered raw
water 11A on the rear side are measured and regarded as the
turbidity causing materials which are mostly composed of
15 organic substances.
In a case in which SDI is used as an index to measure
the turbidity causing materials, the backwashing water 30 to
be used in backwashing is switched from the concentrated
water 22 of seawater to freshwater of the permeated water 21
20 by the flow path switching unit 32 in a case in which SDI
measured at the downstream of the outlet of the filtration
device 12 is equal to or more than the reference value (for
example, 3 or more, or 3.5 or more, or even 6 or more).
In this manner, in the present embodiment, backwashing
25 is performed by using fresh water of a part 21a of the
permeated water 21 regardless of the value of pressure loss
in a case in which the concentration of organic substances
is increased to be equal to or more than the reference value
as a result of measurement by the outlet side organic
30 substance monitoring device 25A.
Incidentally, in the related art, it is controlled such
that backwashing is performed based on an increase in
pressure loss, but in the present embodiment, only a change
19
in pressure loss is not taken into consideration, but when
the amount of organic substances is equal to or more than
the reference value, it is determined that there is an
influence by the organic substances, and backwashing is
5 carried out by using fresh water of the part 21a of the
permeated water 21.
Incidentally, there is a case in which contamination of
the filtration layers 12a and 12b of the filtration device
12 occurs in a case in which seawater at the inlet is dirty
10 although the pressure loss does not increase, that case
corresponds to a case in which the pretreatment function of
the filtration device 12 cannot be sufficiently exerted, and
it is thus possible to prevent filtering clogging and the
like in advance by carrying out washing through backwashing
15 before the function of the filtration device 12 is greatly
decreased by the pressure loss.
In this manner, it is possible to quickly remove dirt
due to the organic substances of the filter medium and to
maintain the organic substance removal performance by the
20 filtration device 12 by controlling the washing timing of
backwashing based on the amount of organic substances in
seawater but not by the pressure loss in the related art.
In particular, the amount of organic substances to be
adsorbed to the filter medium also increases by adsorption
25 equilibrium as the concentration of organic substances in
seawater of the raw water 11 increases. Thereafter, the
adsorbed organic substances desorb more than usual in a case
in which the concentration of organic substances in seawater
decreases, and the concentration of organic substances in
30 seawater on the outlet side is thus increased more than on
the inlet side in some cases. For that reason, it is
required to promote particularly the removal of organic
substances through backwashing using fresh water after the
20
concentration of organic substances in seawater is increased.
According to the present embodiment, a part of the
permeated water is not always used at the time of
backwashing by using a part of the permeated water for
5 backwashing in a case in which the concentration of organic
substances exceeds the reference value, and it is thus
possible to efficiently perform recovery of the filtration
performance by removing the organic substances of the
filtration device while suppressing the amount of the
10 permeated water used.
In the present embodiment, as a device which monitors
this concentration of organic substances, the outlet side
organic substance monitoring device 25A of the filtration
device 12 is installed, but the present invention is not
15 limited thereto.
Specifically, as illustrated in a desalination
treatment system 10B of FIG. 2, it is also possible to
monitor the amount of organic substances attached to the
filtration device 12 by installing an inlet side organic
20 substance monitoring device 25B and the outlet side organic
substance monitoring device 25A.
In addition, in the case of being illustrated in FIG. 2,
only the inlet side organic substance monitoring device 25B
may be installed on the inlet side of the filtration device
25 12.
In this manner, according to the present embodiment, by
a method of washing the filtration device 12 by removing
suspended solids and the like in the raw water, including
monitoring step of monitoring the organic substances in the
30 raw water 11, and washing the filtration device 12 by using
a part of the permeated water 21 obtained by removing the
concentrated water 22 in which a solute such as a salt or
fine particles are enriched from the filtered raw water for
21
backwashing in a case in which the organic substances in the
raw water 11 exceed the reference value, a part of the
permeated water 21 is not always used at the time of
backwashing, and it is thus possible to efficiently perform
5 recovery of the filtration performance by removing the
organic substances of the filtration device 12 while
suppressing the amount of the permeated water 21 used.
In the present embodiment, the filtration treatment
system of raw water has been described by taking a
10 desalination treatment system for seawater desalination in
which a solute such as a salt or fine particles are enriched
as an example, but the present invention is not limited
thereto, and the filtration treatment system of raw water
can also be applied to water treatment systems, for example,
15 a sewage treatment for removing fine particles in raw water
and a wastewater treatment of brackish water (water in which
seawater and fresh water are mixed and the amount of salts
is smaller than in seawater; brackish water)
In the present embodiment, washing of the filtration
20 device 12 is performed by using the permeated water 21 and
the concentrated water 22 which are separated by the
separation device 23, but raw water may also be used as long
as it is raw water which can be applied for backwashing.
Second embodiment
25 The method of backwashing a filtration device of a
desalination treatment system according to embodiments of
the present invention will be described with reference to
the drawings. Incidentally, in the present embodiment, it
is described based on the desalination treatment system 10A
30 illustrated in FIG. 1. FIGS. 3-1 and 3-2 are diagrams which
illustrate the relation of the pressure loss and the
concentration of organic substances with the elapsed days.
In the first embodiment, the part 21a of the permeated
22
water 21 of fresh water is used as the backwashing water 30
in a case in which backwashing is carried out based on the
concentration of organic substances without considering the
pressure loss in the filtration device 12.
5 In contrast, in the present embodiment, the backwashing
water 30 is switched from the concentrated water 22 of
seawater to the permeated water 21 of fresh water after a
certain period of time has elapsed even in a case in which
the concentration of organic substances in seawater of the
10 raw water 11 does not increase to be equal to or more than
the reference value (threshold value).
Here, the set period to switch the backwashing water
can be appropriately changed depending on the quality of
seawater of the raw water 11, and for example, it can be
15 prescribed as every day, every other day, every week, every
two weeks, every month, and the like.
FIG. 3-1 illustrates an example of the switching
operation of backwashing water to be used at the time of
backwashing for one week in the diagram illustrating the
20 relation of the pressure loss and the concentration of
organic substances with the elapsed days. In FIG. 3-1, the
left vertical axis shows the pressure loss, and the
reference value (X) is prescribed. The right vertical axis
shows the concentration of organic substances, and the
25 reference value (Y) is prescribed.
In addition, as the interval of backwashing,
backwashing may be regularly carried out, backwashing may be
carried out when the pressure loss exceeds the reference
value, or both of them may be concurrently used, and any of
30 them may be employed.
In the operation in FIG. 3-1, it is a case in which
backwashing is carried out one time a day at every
predetermined time, and in the operation, the concentrated
23
water 22 is used as the backwashing water 30 from the first
day to the sixth day, and the permeated water 21 is used as
the backwashing water 30 on the seventh day.
Here, in the operation of FIG. 3-1, the pressure loss
5 and the concentration of organic substances are lower than
the reference values (X and Y), and backwashing by the
permeated water 21 is thus performed on the seventh day for
the first time. Thereafter, backwashing by the permeated
water 21 is performed on every seventh day regardless of the
10 value of pressure loss.
According to the present invention, the amount of
organic substances adsorbed to the filtration layers 12a and
12b of the filtration device 12 gradually increases even in
a case in which the amount of the organic substances in the
15 raw water 11 does not remarkably increase, and thus the
organic substances on the filtration layers 12a and 12b are
removed and the accumulation of organic substances is
suppressed by performing backwashing by using the part 21a
of the permeated water 21 when a certain period of time
20 elapses.
In contrast, in an example illustrated in FIG. 3-2, it
is a case in which the concentration of organic substances
exceeds the reference value (Y) on the third day through
monitoring by the outlet side organic substance monitoring
25 device 25A, and in the backwashing operation on the fourth
day, backwashing is carried out by using the permeated water
21 as the backwashing water 30.
Third embodiment
The method of backwashing a filtration device of a
30 desalination treatment system according to embodiments of
the present invention will be described with reference to
the drawings. Incidentally, in the present embodiment, it
is described based on the desalination treatment system 10A
24
illustrated in FIG. 1. FIG. 3-3 is a diagram which
illustrates the relation of the pressure loss and the
concentration of organic substances with the elapsed days.
In the present embodiment, as illustrated in FIG. 3-3,
5 it is assumed a case in which the concentration of organic
substances does not immediately decrease in a case in which
the concentration of organic substances in the raw water 11
is increased.
In such a case, backwashing is not carried out until
10 the concentration of organic substances decreases after the
concentration is increased through monitoring by the outlet
side organic substance monitoring device 25A, and washing is
performed by using fresh water of the part 21a of the
permeated water 21 when the concentration of organic
15 substances is decreased to be equal to or less than the
normal reference (Z).
Specifically, as illustrated in FIG. 3-3, in a case in
which the concentration of organic substances is equal to or
more than the reference value (Y) on the fourth day and it
20 continues until the fifth day, when an increase in pressure
loss is equal to or more than the reference value (X),
backwashing is performed by using the fresh water of the
part 21a of the permeated water 21 as the backwashing water
30 in the case of a second embodiment, but backwashing is
25 carried out by using a part 22a of the concentrated water 22
without using fresh water of the part 21a of the permeated
water 21 as the backwashing water 30 in the case of the
present embodiment.
Moreover, backwashing is carried out by using fresh
30 water of the part 21a of the permeated water 21 as the
backwashing water 30 in a case in which the concentration of
organic substances decreases to be equal to or less than the
normal value (Z) in the middle of the fifth day.
25
Incidentally, backwashing is carried out by using a
part 22a of the concentrated water 22 as the backwashing
water 30 on the fifth day as well in a case in which the
concentration of organic substances does not decrease to be
5 equal to or less than the normal value (Z) even on the fifth
day.
The filtration layer of the filtration device 12 is
contaminated immediately in the case of restarting the
operation after backwashing is performed and the backwashing
10 operation is required again even if the backwashing
operation is carried out in a state in which the
concentration of organic substances in the raw water 11 is
still high. Hence, as in the present embodiment, it is
possible to save the amount of permeated water 21 used and
15 to perform effective washing by continuously performing the
operation as it is and using the concentrated water for
backwashing in a case in which the concentration of organic
substances in the raw water 11 exceeds the reference value
(Y) and the state continues for a predetermined time and by
20 performing backwashing by using the permeated water 21 after
it is detected that the concentration of organic substances
in the raw water 11 is decreased to be equal to or less than
the reference value (Y) of the threshold value.
Fourth embodiment
25 The desalination treatment system according to
embodiments of the present invention will be described with
reference to the drawings. FIG. 4 is the schematic diagram
of a desalination treatment system according to the fourth
embodiment. FIGS. 5-1 to 5-3 are diagrams which illustrate
30 the operation states of the filtration device of the fourth
embodiment.
A desalination treatment system 10C of the present
embodiment has the same device configuration as that of the
26
desalination treatment system 10A of FIG. 1, but it is
provided with a discharge mechanism of backwashing water
when backwashing the filtration device.
As illustrated in FIG. 4, the filtration device 12
5 according to the present embodiment is equipped with the
filtration device main body 12c having a plurality of
filtration layers 12a and 12b layered in the vertical axis
direction in the interior, a raw water supply line L10 that
is connected to the top portion 12d of the filtration device
10 main body 12c and supplies the raw water 11 from this top
portion 12d side, a filtered raw water supply line L11 that
is connected to the bottom portion 12e of the side wall of
the filtration device main body 12c, discharges the raw
water 11A filtered from this side wall side and supplies the
15 raw water 11A to the salt concentrator 23, a backwashing
water supply line L21 that is connected to the bottom
portion 12e of the filtration device main body 12c and
introduces the backwashing water 30 from this the bottom
portion 12e side, an overflow line L31 that is connected to
20 the top portion 12d side of the side wall of the filtration
device main body 12c and discharges the backwashing water 30
from the top portion 12d side of the filtration layer 12a as
an overflowed water 30A, and a backwashing water discharge
line L32 that is connected to the bottom portion 12e of the
25 filtration device main body 12c and discharges a backwashing
water 30B which cannot overflow from this bottom portion 12e
side.
As illustrated in FIGS. 5-1 to 5-3, in the filtration
device 12 according to the present embodiment, the raw water
30 11 is introduced from the top portion 12d of the filtration
device main body 12c through the raw water supply line L10.
The control device 31 controls the introduction of the raw
water 11 into the filtration device main body 12 by
27
controlling a valve V10 provided on the raw water supply
line L10.
In addition, the filtered raw water 11A is discharged
from the bottom portion 12e side of the filtration device
5 main body 12c through the filtered raw water supply line L11.
The control device 31 controls the discharge of the filtered
raw water 11A from the filtration device 12c by controlling
a valve V11 provided on the filtered raw water supply line
L11.
10 In addition, the backwashing water 30 is introduced
from the bottom portion 12e side of the filtration device
main body 12c through the backwashing water supply line L21.
The control device 31 controls the introduction of the
backwashing water 30 into the filtration device main body
15 12c by controlling a valve V12 provided on the backwashing
water supply line L21.
In addition, the overflowed water 30A is discharged
from the top portion 12d side of the filtration layer 12a of
the filtration device main body 12c through the overflow
20 line L31. The control device 31 controls the discharge of
the overflowed water 30A which has flowed into the overflow
line L31 by controlling a valve V13 provided on the overflow
line L31.
Furthermore, the backwashing water 30B which cannot
25 overflow is discharged from the bottom portion 12e side of
the filtration device main body 12c through the backwashing
water discharge line L32. The control device 31 controls
the discharge and storage of the backwashing water 30B which
cannot overflow, namely, the backwashing water 30B stored in
30 the region on the vertically lower side of the overflow line
L31 of the filtration device main body 12 by controlling the
opening and closing of a valve V14 provided on the
backwashing water discharge line L32.
28

The normal operation of the present embodiment is a
case in which the raw water 11 is filtered by the filtration
device 12.
5 In the case of this normal operation, as illustrated in
FIG. 5-1, the control device 31 controls the valves V10 and
V11 to open and the valves V12, V13, and V14 to close. In the
desalination treatment system 10C, the raw water 11 is
introduced into the filtration device main body 12c and the
10 suspended substances in the raw water 11 are captured by the
filtration layers 12a and 12b. Incidentally, in FIG. 5-1,
FIG. 5-2, and FIG. 5-3, the black mark of valve is a case in
which the valve is closed and the white mark of valve is a
case in which the valve is open.
15
Next, as illustrated in FIG. 5-2, a backwashing
operation is executed when it is determined that the
concentration of organic substances in the raw water 11
exceeds the reference value by the outlet side organic
20 substance monitoring device 25A.
In the case of this backwashing operation, the control
device 31 controls the valves V12 and V13 to open and the
valves V10, V11, and V14 to close and thus stops the
introduction of the raw water 11.
25 Moreover, as the backwashing water 30, the flow path
switching unit 32 is switched so that a part 21a of the
permeated water 21 is introduced from the bottom portion 12e
of the filtration device main body 12c. The introduced
backwashing water 30 is discharged to the outside as the
30 overflowed water 30A through the overflow line L31 on the
upper side of the filtration layer 12a, and backwashing is
performed.
29

Thereafter, as illustrated in FIG. 5-3, the
introduction of the backwashing water 30 is stopped, and the
control device 31 controls the valves V10, V11, V12, and V13
5 to close and the valve V14 to open. The desalination
treatment system 10C discharges the backwashing water 30B
which cannot overflow and thus remains in the filtration
device main body 12c through the backwashing water discharge
line L32 and drains the backwashing water 30B which is in
10 the interior of the filtration device main body 12c and
cannot overflow.
According to the present embodiment, it is possible to
decrease the concentration of organic substances in the
washing water and to improve the washing effect when the
15 interior of the filtration device 12 is washed by once
discharging the backwashing water 30B which is contaminated
with the organic substances in the filtration device 12 and
cannot overflow and then supplying the permeated water 21.
This operation that the backwashing water 30B is
20 drained, water in the interior of the filtration device main
body 12c is drained, then the backwashing water 30 is
introduced again to perform backwashing, and the water is
drained again may be repeated at least one time or more.
Fifth embodiment
25 The method of backwashing a filtration device of a
desalination treatment system according to embodiments of
the present invention will be described with reference to
the drawings. FIG. 6 is the schematic diagram of a
desalination treatment system according to the present
30 embodiment.
A desalination treatment system 10D illustrated in FIG.
6 is provided with the salt concentrator 23 having a
plurality of stages (a first salt concentrator 23A, a second
30
salt concentrator 23B,   ) in series in the desalination
treatment system 10A of the first embodiment.
In the present embodiment, as illustrated in FIG. 6,
the first salt concentrator 23A is provided at the
5 subsequent stage of the filtration device 12 and the second
salt concentrator 23B is provided at the subsequent stage of
the first salt concentrator 23A. Moreover, the raw water 11A
filtered by the filtration device 12 is first introduced
into the first salt concentrator 23A and separated into a
10 permeated water 21A and a concentrated water 22A in which a
solute such as a salt or fine particles are enriched by the
separation membrane 23a of the first salt concentrator 23A.
Next, the separated permeated water 21A is introduced into
the second salt concentrator 23B through the permeated water
15 line L12A and the separated into a permeated water 21B and a
concentrated water 22B in which a solute such as a salt or
fine particles are enriched by the separation membrane 23b
of the second salt concentrator 23B. The permeated water 21B
separated by the separation membrane 23b of the second salt
20 concentrator 23B is discharged through the permeated water
line L12B and utilized as produced water (fresh water).
Moreover, in the present embodiment, backwashing of the
filtration device 12 is performed by using a part 21Aa of
the permeated water 21A from the (leading) first salt
25 concentrator 23A on the filtration device 12 side.
As a result, it is possible to obtain a sufficient
backwashing effect, for example, without relatively
decreasing the fresh water production efficiency in a
desalination plant to desalinate seawater by using the part
30 21Aa of the permeated water 21A of the first salt
concentrator 23A as the backwashing water 30 without using
the permeated water 21B of fresh water manufactured by the
salt concentrator at the final stage as the backwashing
31
water 30 to be used for backwashing.
Here, when the desalination treatment is performed by
using seawater as the raw water 11, about 90% or more of the
organic substances in the seawater is removed when the
5 seawater passes through the first salt concentrator 23A, and
a sufficient backwashing effect can be thus obtained even
when a part 21Aa of the permeated water 21A of the first
salt concentrator 23A is utilized as the backwashing water
30.
10 Accordingly, it is possible to save the power required
for treating the water to be used for backwashing by the
second salt concentrator 23B or the subsequent salt
concentrator by using the part 21Aa of the permeated water
21A from the first salt concentrator 23A instead of the
15 finally manufactured fresh water, and the operation
efficiency of the desalination plant for seawater is thus
improved.
According to the present embodiment, in a case in which
a plurality of salt concentrators 23 (the first salt
20 concentrator 23A, the second salt concentrator 23B,   ) to
obtain permeated water are installed in series to improve
the desalination performance, it is possible to obtain a
sufficient backwashing effect without relatively decreasing
the treatment efficiency of the salt concentration plant by
25 using a part 21Aa of the permeated water 21A from the first
salt concentrator 23A that is on the leading side and has a
relatively low salt removal rate instead of using permeated
water of the final product as the permeated water to be used
for backwashing.
30 In the present embodiment, two salt concentrators are
illustrated, but in the case of installing a plurality of
stages of three or more, it is preferable to perform
backwashing of the filtration device 12 by using permeated
32
water from a separation device (for example, the separation
device at the first or second stage in a case in which three
separation devices are installed in series) provided on the
upstream side of a separation device other than the
5 separation device (separation device at the final stage)
provided at the position farthest from the filtration device
12.
In addition, in the case of installing three or more
salt concentrators 23 in series, a part of the permeated
10 water 21B or the like from the second or subsequent salt
concentrator 23B or the like from the filtration device 12
side is also used in some cases in consideration of the
concentration of organic substances and the like.
15 Reference Signs List
10A to 10D DESALINATION TREATMENT SYSTEM
11 RAW WATER
12 FILTRATION DEVICE
21 PERMEATED WATER
20 22 CONCENTRATED WATER
23 SALT CONCENTRATOR
23A FIRST SALT CONCENTRATOR
23B SECOND SALT CONCENTRATOR
25A OUTLET SIDE ORGANIC SUBSTANCE MONITORING DEVICE
25 25B INLET SIDE ORGANIC SUBSTANCE MONITORING DEVICE

We Claim:
1. A filtration treatment system of raw water comprising:
a raw water supply line that is configured to supply
5 raw water;
a filtration device that is provided on the raw
water supply line and configured to filter impurities in
the raw water;
a separation device that is provided on a rear side
10 of the filtration device and equipped with a separation
membrane to separate filtered raw water into permeated
water and concentrated water in which a solute including
a salt or fine particles are enriched;
an organic substance monitoring device that is
15 provided on either front or rear or both front and rear
of the filtration device and configured to monitor an
amount of an organic substance in the raw water; and
a control device that is configured to execute
backwashing of the filtration device with the permeated
20 water as backwashing water in a case in which the amount
of the organic substance in the raw water is determined
to exceed a reference value as a result of monitoring by
the organic substance monitoring device.
25 2. The filtration treatment system of raw water according
to claim 1, wherein the control device executes
backwashing of the filtration device with the raw water
or the concentrated water as the backwashing water in a
case in which the amount of the organic substance in the
30 raw water is determined to be equal to or less than the
reference value as a result of monitoring by the organic
substance monitoring device.
34
3. A filtration treatment system of raw water comprising:
a raw water supply line that is configured to supply
raw water;
a filtration device that is provided on the raw
5 water supply line and configured to filter impurities in
the raw water;
a separation device that is provided on a rear side
of the filtration device and equipped with a separation
membrane to separate filtered raw water into permeated
10 water and concentrated water in which a solute including
a salt or fine particles are enriched;
an organic substance monitoring device that is
provided on either front or rear or both front and rear
of the filtration device and configured to monitor an
15 amount of an organic substance in the raw water; and
a control device that is configured to execute
backwashing of the filtration device with the
concentrated water as backwashing water in a case in
which the amount of the organic substance in the raw
20 water is determined to be equal to or less than a
reference value as a result of monitoring by the organic
substance monitoring device and execute backwashing of
the filtration device with the permeated water as the
backwashing water in a case in which the amount of the
25 organic substance in raw water is determined to exceed
the reference value as a result of monitoring by the
organic substance monitoring device.
4. The filtration treatment system of raw water according
30 to any one of claims 1 to 3, wherein the organic
substance monitoring device includes an organic
substance concentration measurement device configured to
measure a concentration of the organic substance in the
35
raw water.
5. The filtration treatment system of raw water according
to any one of claims 1 to 4, wherein the organic
5 substance monitoring device is provided on a rear side
of the filtration device and includes a turbidity
measuring device configured to measure a turbidity in
raw water from the filtration device.
10 6. The filtration treatment system of raw water according
to any one of claims 1 to 5, wherein the control device
executes backwashing of the filtration device with the
permeated water at every set period.
15 7. The filtration treatment system of raw water according
to any one of claims 1 to 6, comprising:
a plurality of the separation devices, wherein
the plurality of separation devices are connected to
permeated water lines to discharge the permeated water
20 in series,
the filtration device is connected to a permeated
water line of permeated water to be discharged from the
separation device provided on an upstream side of the
separation device at a final stage, and
25 the control device performs backwashing of the
filtration device with permeated water to be discharged
from the separation device provided on the upstream side
of the separation device at the final stage in a case of
executing backwashing of the filtration device with the
30 permeated water.
8. The filtration treatment system of raw water according
to any one of claims 1 to 7, wherein the filtration
36
device includes:
a filtration device main body that has a plurality
of filtration layers layered in a vertical axis
direction in an interior;
5 a supply line that is configured to supply the raw
water from a top portion side of the filtration device
main body;
a filtered raw water supply line that is configured
to discharge filtered raw water filtered from a bottom
10 portion side of the filtration device main body and
supply the filtered raw water to the separation device;
a backwashing water introduction line that is
configured to introduce backwashing water from the
bottom portion side of the filtration device main body;
15 an overflow line that is configured to collect the
backwashing water overflowed from a top portion side of
the filtration layers of the filtration device main
body; and
a backwashing water discharge line that is
20 configured to discharge the backwashing water of the
filtration device main body from the bottom portion side
of the filtration device main body.
9. The filtration treatment system of raw water according
25 to claim 8, wherein the control device executes
backwashing by carrying out a treatment in which the
backwashing water discharge line is opened, the
backwashing water in an interior of the filtration
device main body is drained through the backwashing
30 water discharge line, then the backwashing water
discharge line is closed, and the backwashing water is
introduced into the interior of the filtration device
main body through the backwashing water introduction
37
line at least once or more in a case in which the
control device determines to execute backwashing of the
filtration device.
5 10. The filtration treatment system of raw water according
to any one of claims 1 to 9, wherein
the control device executes backwashing with the
permeated water after detecting that the concentration
of the organic substance is decreased to a concentration
10 equal to or less than a threshold concentration lower
than a predetermined concentration
in a case in which a state in which the
concentration of the organic substance exceeds the
predetermined concentration continues for a
15 predetermined time or longer through monitoring by the
organic substance monitoring device.
11. A method of washing a filtration device that removes a
suspended solid in raw water, the method comprising:
20 an organic substance monitoring step of monitoring
an amount of an organic substance in the raw water; and
a permeated water backwashing step of backwashing
the filtration device by using permeated water obtained
by removing a solute including a salt or fine particles
25 from the filtered raw water as backwashing water in a
case in which an amount of an organic substance in the
raw water monitored in the organic substance monitoring
step exceeds a reference value.
30 12. A method of washing a filtration device that is
configured to remove a suspended solid in raw water, the
method comprising:
an organic substance monitoring step of monitoring
38
an amount of an organic substance in the raw water; and
a step of performing backwashing of the filtration
device by using concentrated water as backwashing water
in a case in which an amount of an organic substance in
5 the raw water monitored in the organic substance
monitoring is determined to be equal to or less than a
reference value and performing backwashing of the
filtration device by using permeated water as the
backwashing water in a case in which the amount of the
10 organic substance in the raw water is determined to
exceed the reference value as a result of monitoring by
the organic substance monitoring device.