WATER TREATMENT DEVICE AND METHOD
BACKGROUND
The invention relates generally to liquid treatment devices and methods. More
particularly, this invention relates to water treatment devices and methods.
Membrane desalination devices, for example, nanofiltration membrane devices or
reverse osmosis membrane devices are used in beverage plants to yield product water
because of their reliabilities in qualities of product water. However, the membrane
desalination devices have problems of scaling tendencies on their membranes, so the
product water recovery rate of a typical membrane desalination device is in the range
of from about 50% to about 90%. The rest 10-50% of feed water is usually
discharged as wastewater. Beverage plants in the world consume a large amount of
usable water everyday, thereby needing a huge amount of source water to be treated
by the membrane desalination devices and discharging a large amount of wastewater,
which leads to high costs and high waste and is undesirable.
In addition, people and almost every industry in the whole world also need more and
more usable water and can not afford discharging more wastewater.
Therefore, there is a need to develop a new water treatment device and method.
BRIEF DESCRIPTION
In one aspect, a water treatment device is provided, comprising: a membrane
desalination unit; a first conduit connected with the membrane desalination unit and
configured to transport a first stream of feed water to the membrane desalination unit;
a second conduit connected with the membrane desalination unit and configured to
transport a first stream of product water of lower salinity than the first stream of feed
water out of the membrane desalination unit; an electrical separation unit; a third
conduit connected with the membrane desalination unit and the electrical separation
unit and configured to transport a first stream of reject water of higher salinity than
the first stream of feed water from the membrane desalination unit to the electrical
separation unit; a fourth conduit connected with the electrical separation unit and
configured to transport a second stream of product water of lower salinity than the
first stream of reject water out from the electrical separation unit; a precipitation unit;
a fifth conduit connected with the precipitation unit and the electrical separation unit
and configured to transport a second stream of reject water of higher salinity than the
first stream of reject water from the electrical separation unit to the precipitation unit;
a sixth conduit connected with the precipitation unit and the electrical separation unit
and configured to transport a second stream of feed water of lower salinity than the
second stream of reject water from the precipitation unit to the electrical separation
unit; a seventh conduit connected with the precipitation unit and configured to release
a discharge stream of water; and a chemical injection unit in communication with at
least one of the electrical separation unit and the precipitation unit.
In another aspect, a method is provided. The method comprises: providing a
membrane desalination unit; providing a first conduit connected with the membrane
desalination unit and configured to transport a first stream of feed water to the
membrane desalination unit; providing a second conduit connected with the
membrane desalination unit and configured to transport a first stream of product water
of lower salinity than the first stream of feed water out of the membrane desalination
unit; providing an electrical separation unit; providing a third conduit connected with
the membrane desalination unit and the electrical separation unit and configured to
transport a first stream of reject water of higher salinity than the first stream of feed
water from the membrane desalination unit to the electrical separation unit; providing
a fourth conduit connected with the electrical separation unit and configured to
transport a second stream of product water of lower salinity than the first stream of
reject water out from the electrical separation unit; providing a precipitation unit;
providing a fifth conduit connected with the precipitation unit and the electrical
separation unit and configured to transport a second stream of reject water of higher
salinity than the first stream of reject water from the electrical separation unit to the
precipitation unit; providing a sixth conduit connected with the precipitation unit and
the electrical separation unit and configured to transport a second stream of feed water
of lower salinity than the second stream of reject water from the precipitation unit to
the electrical separation unit; providing a seventh conduit connected with the
precipitation unit and configured to release a discharge stream of water; and providing
a chemical injection unit in communication with at least one of the electrical
separation unit and the precipitation unit.
These and other advantages and features will be better understood from the following
detailed description of preferred embodiments of the invention that is provided in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a water treatment device in accordance with one
embodiment of the invention; and
FIG. 2 is a schematic diagram of part of a water treatment device comprising an
electrodialysis reversal (EDR) unit and a precipitation unit used in the experimental
example.
DETAILED DESCRIPTION
Preferred embodiments of the present disclosure will be described hereinbelow with
reference to the accompanying drawings. In the following description, well-known
functions or constructions are not described in detail to avoid obscuring the disclosure
in unnecessary detail.
Approximating language, as used herein throughout the specification and claims, may
be applied to modify any quantitative representation that could permissibly vary
without resulting in a change in the basic function to which it is related. Accordingly,
a value modified by a term or terms, such as "about" or "substantially", is not to be
limited to the precise value specified. In some instances, the approximating language
may correspond to the precision of an instrument for measuring the value. Moreover,
the suffix "(s)" as used herein is usually intended to include both the singular and the
plural of the term that it modifies, thereby including one or more of that term.
FIG. 1 is a schematic diagram of a water treatment device 100 in accordance with one
embodiment of the present invention. The water treatment device 100 comprises: a
membrane desalination unit 102; a first conduit 104 connected with the membrane
desalination unit and configured to transport a first stream of feed water 106 to the
membrane desalination unit; a second conduit 108 connected with the membrane
desalination unit and configured to transport a first stream of product water 110 of
lower salinity than the first stream of feed water out of the membrane desalination
unit; an electrical separation unit 112; a third conduit 114 connected with the
membrane desalination unit and the electrical separation unit and configured to
transport a first stream of reject water 116 of higher salinity than the first stream of
feed water from the membrane desalination unit to the electrical separation unit; a
fourth conduit 118 connected with the electrical separation unit and configured to
transport a second stream of product water 120 of lower salinity than the first stream
of reject water out from the electrical separation unit; a precipitation unit 122; a fifth
conduit 124 connected with the precipitation unit and the electrical separation unit and
configured to transport a second stream of reject water 126 of higher salinity than the
first stream of reject water from the electrical separation unit to the precipitation unit;
a sixth conduit 128 connected with the precipitation unit and the electrical separation
unit and configured to transport a second stream of feed water 130 of lower salinity
than the second stream of reject water from the precipitation unit to the electrical
separation unit; a seventh conduit 132 connected with the precipitation unit and
configured to release a discharge stream of water 134; and a chemical injection unit
136 in communication with at least one of the electrical separation unit and the
precipitation unit.
In the illustrated embodiment, the fourth conduit 118 is connected with the first
conduit 104 and configured to transport the second stream of product water 120 to
mix with the first stream of feed water 106. The membrane desalination unit 102 may
comprise a nanofiltration membrane device, a reverse osmosis membrane device or a
combination thereof. The product water recovery rate of a typical membrane
desalination device is in the range of from about 50% to about 90%. The electrical
separation unit 112 may comprise an electrodialysis reversal (EDR) desalination
device, a supercapacitive desalination (SCD) device, or a combination thereof. The
water recovery of an EDR or SCD plus precipitation unit is typically in the range of
from about 80% to about 99%. Therefore, the overall water recovery of the water
treatment device 100 is in the range of from about 90% to about 99.9% and a
volumetric flow rate of the first stream of product water 110 is in the range of from
about 90% to about 99.9% of a volumetric flow rate of the first stream of feed water
106. For applications like beverage plants which need water of high quality, the water
treatment device 100 yields much usable product water and discharge little
wastewater.
In some embodiments, the fourth conduit 118 may be not connected with the first
conduit 104 and configured to transport the second stream of product water 120 into
another water treatment device (not shown) or directly out. In such way, product
water of the water treatment device 100 are in two separate streams 110, 120. The
total water recovery rate is still high.
In some instances, some dissolved alkalies, such as bicarbonates, will turn into
unsolvable or barely solvable salts, e.g., calcium carbonate (CaC0 3) to build up/scale
in the electrical separation unit because of the high concentration of water that is
handled by the electrical separation unit and the precipitation unit. In some
embodiments, the chemical injection unit 136 comprises an acid injection unit
providing hydrochloric acid or sulfuric acid to reduce alkalinity by reacting
hydrochloric acid or sulfuric acid with bicarbonates.
The chemical injection unit 136 may be in communication with the electrical
separation unit and/or the precipitation unit directly, or through the third conduit 114
and/or the fifth conduit 124.
In the illustrated example, the water treatment device 100 comprises a filtration
device 138 in communication with the sixth conduit 128 to prevent particles (not
shown, if any) from entering into the electrical separation unit 112. The filtration
device 138 may comprise a cartridge filter.
In another aspect, a method is provided. The method comprises: providing a
membrane desalination unit 102; providing a first conduit 104 connected with the
membrane desalination unit and configured to transport a first stream of feed water
106 to the membrane desalination unit; providing a second conduit 108 connected
with the membrane desalination unit and configured to transport a first stream of
product water 110 of lower salinity than the first stream of feed water out of the
membrane desalination unit; providing an electrical separation unit 112; providing a
third conduit 114 connected with the membrane desalination unit and the electrical
separation unit and configured to transport a first stream of reject water 116 of higher
salinity than the first stream of feed water from the membrane desalination unit to the
electrical separation unit; providing a fourth conduit 118 connected with the electrical
separation unit and configured to transport a second stream of product water 120 of
lower salinity than the first stream of reject water out from the electrical separation
unit; providing a precipitation unit 122; providing a fifth conduit 124 connected with
the precipitation unit and the electrical separation unit and configured to transport a
second stream of reject water 126 of higher salinity than the first stream of reject
water from the electrical separation unit to the precipitation unit; providing a sixth
conduit 128 connected with the precipitation unit and the electrical separation unit and
configured to transport a second stream of feed water 130 of lower salinity than the
second stream of reject water from the precipitation unit to the electrical separation
unit; providing a seventh conduit 132 connected with the precipitation unit and
configured to release a discharge stream of water 134; and providing a chemical
injection unit 136 in communication with at least one of the electrical separation unit
and the precipitation unit.
For certain arrangements, the electrical separation unit may be an SCD device. The
term "SCD device" may generally indicate supercapacitors that are employed for
desalination of seawater or deionization of other brackish waters to reduce the amount
of salt or other ionized impurities to a permissible level for domestic and industrial
use. In certain applications, the supercapacitor desalination device may comprise one
or more supercapacitor desalination cells (not shown). As is known, in non-limiting
examples, each supercapacitor desalination cell may at least comprise a pair of
electrodes, a spacer, and a pair of current collectors attached to the respective
electrodes. A plurality of insulating separators may be disposed between each pair of
adjacent SCD cells when more than one supercapacitor desalination cell stacked
together is employed.
In embodiments of the invention, the current collectors may be connected to positive
and negative terminals of a power source (not shown), respectively. Since the
electrodes are in contact with the respective current collectors, the electrodes may act
as anodes and cathodes, respectively.
During the charging state of the supercapacitor desalination device 112, an input
stream 116 from the membrane desalination device 102 passes through a valve (not
shown) and enters into the SCD device for desalination. In this state, the flow path of
an input stream 130 to the SCD device 112 is closed by valve (not shown). Positive
and negative electrical charges from the power source accumulate on surfaces of the
anode(s) and the cathode(s), respectively and attract anions and cations from the
ionized input stream 116, which causes them to be adsorbed on the surfaces of the
anode(s) and the cathode(s), respectively. As a result of the charge accumulation on
the anode(s) and the cathode(s), an outflow stream, such as an output stream 120 from
the SCD device 112 passing through valve (not shown) may have a lower salinity
(concentration of salts or other ionic impurities) as compared to the input stream 116
In the discharging state of the supercapacitor desalination device 112, the adsorbed
anions and cations dissociate from the surfaces of the anode(s) and the cathode(s),
respectively. The input stream 130 is pumped by pump (not shown) from the
precipitation unit 122, and passes through filter (not shown) and valve (not shown) to
enter the SCD device 112 to carry ions (anions and cations) therefrom. An outflow
stream 126 flowing from the SCD device 112 and passing through the valve (not
shown) has a higher salinity (concentration of the salt or other ionic impurities) as
compared with the input stream 130. In this state, the flow path of the input stream
116 to the SCD device 112 is closed by the valve (not shown). In certain applications,
filter may not be provided.
After discharging of the SCD device is complete, the SCD device is placed in the
charging state for a period of time for preparation of a subsequent discharging. That
is, the charging and the discharging of the SCD device are alternated for treating input
streams 116 and 130, respectively.
As the water is circulated through the SCD unit and the precipitation unit in the
discharging state, the concentration of salts or other ionic impurities in the water
increases so as to produce precipitate in the precipitation unit 122. The precipitate
particles (solids) with diameters larger than a specified diameter may settle by gravity
in the lower portion of the precipitation unit 122. Other precipitate particles with
diameters smaller than the specified diameter may be dispersed in the water.
When the precipitation rate plus a blow down rate of stream 134 equals the charged
species removal rate from the input stream 116, where the rates are averaged over one
or more charging-discharging cycles, the degree of saturation or supersaturation of the
streams circulating between the SCD unit and the precipitation unit may stabilize and
a dynamic equilibrium may be established.
In certain examples, the energy released in the discharging state may be used to drive
an electrical device (not shown), such as a light bulb, or may be recovered using an
energy recovery cell, such as a bi-directional DC-DC converter.
In other non-limiting examples, similar to the SCD cells stacked together, the
supercapacitor desalination device may comprise a pair of electrodes, a pair of current
collectors attached to the respective electrodes, one or more bipolar electrodes
disposed between the pair of electrodes, and a plurality of spacers disposed between
each of the pairs of adjacent electrodes for processing first stream of reject water 116
in a charging state and second stream of feed water 130 in a discharging state. Each
bipolar electrode has a positive side and a negative side, separated by an ionimpermeable
layer.
In some embodiments, the current collectors may be configured as a plate, a mesh, a
foil, or a sheet and formed from a metal or metal alloy. The metal may include
titanium, platinum, iridium, or rhodium, for example. The metal alloys may include
stainless steel, for example. In other embodiments, the current collectors may
comprise graphite or plastic material, such as polyolefin, which may include
polyethylene. In certain applications, the plastic current collectors may be mixed with
conductive carbon blacks or metallic particles to achieve a certain level of
conductivity.
The electrodes and/or bipolar electrodes may include electrically conductive
materials, which may or may not be thermally conductive, and may have particles
with small sizes and large surface areas. In some examples, the electrically
conductive material may include one or more carbon materials. Non-limiting
examples of the carbon materials include activated carbon particles, porous carbon
particles, carbon fibers, carbon aerogels, porous mesocarbon microbeads, or
combinations thereof. In other examples, the electrically conductive materials may
include a conductive composite, such as oxides of manganese, or iron, or both, or
carbides of titanium, zirconium, vanadium, tungsten, or combinations thereof.
Additionally, the spacer may comprise any ion-permeable, electronically
nonconductive material, including membranes and porous and nonporous materials to
separate the pair of electrodes. In non-limiting examples, the spacer may have or
itself may be space to form flow channels through which a liquid for processing
passes between the pair of electrodes.
In certain examples, the electrodes, the current collectors, and/or the bipolar
electrodes may be in the form of plates that are disposed parallel to each other to form
a stacked structure. In other examples, the electrodes, the current collectors, and/or
the bipolar electrodes may have varied shapes, such as a sheet, a block, or a cylinder.
Further, the electrodes, the current collectors, and/or the bipolar electrodes may be
arranged in varying configurations. For example, the electrodes, the current collectors,
and/or the bipolar electrodes may be disposed concentrically with a spiral and
continuous space therebetween.
For certain arrangements, the electrical separation unit may be an electrodialysis
reversal (EDR) device. The term "EDR" may indicate an electrochemical separation
process using ion exchange membranes to remove ions or charged species from water
and other fluids.
As is known, in some non-limiting examples, the EDR device comprises a pair of
electrodes configured to act as an anode and a cathode, respectively. A plurality of
alternating anion- and cation-permeable membranes are disposed between the anode
and the cathode to form a plurality of alternating dilute and concentrate channels
therebetween. The anion-permeable membrane(s) are configured to be passable for
anions. The cation-permeable membrane(s) are configured to be passable for cations.
Additionally, the EDR device may further comprise a plurality of spacers disposed
between each pair of the membranes, and between the electrodes and the adjacent
membranes.
Accordingly, while an electrical current is applied to the EDR device 112, water, such
as the streams 116 and 130 (as shown in FIG. 1) pass through the respective
alternating dilute and concentrate channels, respectively. In the dilute channels, the
first stream 116 is ionized. Cations in the first stream 116 migrate through the cationpermeable
membranes towards the cathode to enter into the adjacent channels. The
anions migrate through the anion-permeable membranes towards the anode to enter
into other adjacent channels. In the adjacent channels (concentrate channels) located
on each side of a dilute channel, the cations may not migrate through the anionpermeable
membranes, and the anions may not migrate through the cation permeable
membranes, even though the electrical field exerts a force on the ions toward the
respective electrode (e.g. anions are pulled toward the anode). Therefore, the anions
and cations remain in and are concentrated in the concentrate channels.
As a result, the second stream of feed water 130 passes through the concentrate
channels to carry the concentrated anions and cations out of the EDR unit 112 so that
the outflow stream 126 may be have a higher salinity than the input stream 130. After
the circulation of the liquid in the EDR unit 112, the precipitation of the salts or other
impurities may occur in the precipitation unit 122.
In some examples, the polarities of the electrodes of the EDR device 112 may be
reversed, for example, every 15-50 minutes so as to reduce the fouling tendency of the
anions and cations in the concentrate channels. Thus, in the reversed polarity state,
the dilute channels from the normal polarity state may act as the concentrate channels
for the second stream 130, and the concentrate channels from the normal polarity state
may function as the dilution channels for the input stream 116.
In some EDR applications, the electrodes may include electrically conductive
materials, which may or may not be thermally conductive, and may have particles
with small sizes and large surface areas. The spacers may comprise any ionpermeable,
electronically nonconductive material, including membranes and porous
and nonporous materials. In non-limiting examples, the anion permeable membrane
may comprise a quaternary amine group. The cation permeable membrane may
comprise a sulfonic acid group or a carboxylic acid group.
In some embodiments, the precipitation of the salts or other impurities may not occur
very quickly until the degree of saturation or supersaturation thereof is very high. For
example, calcium sulfate (CaS0 4) often reaches a degree of supersaturation of about
400% before precipitation occurs in about 5 minutes, which may be disadvantageous
to the precipitation system. Accordingly, in certain examples, seed particles (not
shown) may be added into the precipitation unit to induce quick precipitation on
surfaces thereof at a lower degree of supersaturation of the salts or other ionic
impurities. Additionally, agitation devices and/or pumps may be provided to facilitate
suspension of the seed particles in the precipitation unit.
In non-limiting examples, the seed particles may have an average diameter range from
about 1 to about 500 microns, and may have a concentration range of from about 0.1
weight percent (wt %) to about 30 wt % of the weight of the water in a precipitation
zone of the precipitation unit. In some examples, the seed particles may have an
average diameter range from about 5 to about 100 microns, and may have a
concentration range of from about 0.1 wt % to about 20 wt % of the weight of the
liquid in the precipitation zone. In certain applications, the seed particles may
comprise solid particles including, but not limited to CaS0 4 particles and their
hydrates to induce the precipitation. The CaS0 4 particles may have an average
diameter range from about 10 microns to about 200 microns. In some examples, the
CaS0 4 seed particle concentration may be in a range of from about 0.1 wt % to about
2.0 wt % of the weight of the liquid in the precipitation zone, so that the concentration
of CaS0 4 in the solution leaving the precipitation unit 122 may be controlled in a
range of from about 100% to about 150% of saturation.
It should be noted that seed particles are not limited to any particular seed particles,
and may be selected based on specific applications.
EXAMPLE
The following example is included to provide additional guidance to those of ordinary
skill in the art in practicing the claimed invention. Accordingly, this example does not
limit the invention as defined in the appended claims.
Experiments using nano-filtration (NF) membranes or reverse osmosis ( O)
membranes were not conducted and major ion species and total dissolved solids (TDS)
in feed stream, product stream and reject stream of an industrial NF unit are shown in
Table 1 below as an example. There are no or nearly zero suspended solids in the feed,
product and reject streams of the industrial NF membrane device.
Table 1
FIG. 2 shows a schematic diagram of part of a water treatment device comprising an
electrodialysis reversal (EDR) unit 11 and a precipitation unit 12 and used in the
experimental example.
Water was made in the lab to have the same composition as that of the reject stream
of table 1 to simulate as an NF reject stream 54. The NF reject stream 54 was fed into
a feed tank 50 and mixed with an acid injection stream 64 to be at least partially
neutralized in alkalinity thereof. The acid injection stream 64 was pumped through an
acid injection pump 62 from an acid tank (acid injection unit) 60. The acid injection
stream 64 comprised hydrochloric acid (about 37% concentration by weight) which
reacted with alkalinity as shown in the following formula: HC1 + HCO3 H20 +
C0 2 + CI . The resulted carbon dioxide gas was released from the feed tank 50.
Agitation device (not shown) was used in the feed tank to enhance the mixing and the
reaction. Gas sparing device or other de-gassing device (not shown) may be also used
in the feed tank or in a separate location to enhance the removal of carbon dioxide gas
from the water. Acid additives that may be added into the feed tank 50 include but are
not limited to hydrochloric acid and sulfuric acid.
After the alkalinity reduction in the feed tank 50, the water stream 13 was pumped
into the dilute channels of the EDR unit 11 through the feed pump 52 under the
guidance of flow reversal valve 31 along first input pipes, as indicated by solid line 33.
At the same time, a concentrate stream 17 from a solid-liquid separation zone 24 of
the precipitation unit 12 was introduced into the concentrate channels of the EDR unit
11 through the concentrate recirculation pump 18 under the guidance of flow reversal
valve 32 along first input pipe, as indicated by solid line 34. A cartridge filter 19 was
used between the concentrate recirculation pump 18 and the EDR unit 11 to prevent
particles from entering into the EDR unit 11.
While an electrical current is applied to the EDR unit 11 through a power supply (not
shown), cations in the dilute channels migrate through the cation exchange
membranes towards the cathode to enter into the adjacent concentrate channels.
Anions migrate through the anion exchange membranes towards the anode to enter
into other adjacent concentrate channels. In the adjacent concentrate channels located
on each side of a dilute channel, cations may not migrate through the anion-permeable
membranes, and the anions may not migrate through the cation exchange membranes,
even though the electrical field exerts a force on the ions toward the respective
electrode (e.g. anions are pulled toward the anode). Therefore, the anions and cations
remain in and are concentrated in the concentrate channels.
As a result, the feed stream 13 passed through the dilute channels of the EDR unit 11
was partially desalinated so that the corresponding outflow stream 14 had a lower
salinity than the input stream 13. The concentrate stream 17 passed through the
concentrate channels to carry the concentrated anions and cations out of the EDR
device 11 so that the corresponding outflow stream 16 had a higher salinity than the
input stream 17. The product stream 14 and the output brine stream 16 flowed out
through the control of the flow reversal valves 35 and 36, respectively and enter into
respective first output pipes, as indicated by solid lines 37 and 38. The brine stream
16 was fed into a precipitation zone 28 of the precipitation unit 12.
In order to reduce the scaling tendency of the anion exchange membranes and cation
exchange membranes in the concentrate channels, the polarities of the electrodes of
the EDR unit 11 were reversed every 1000 seconds. Thus, in the reversed polarity
state, the dilute channels from the normal polarity state acted as the concentrate
channels to receive the concentrate stream 17, and the concentrate channels from the
normal polarity state functioned as the dilute channels to receive the feed stream 13.
The streams 13 and 17 entered the EDR device 11 along respective second input pipes,
as indicated by broken lines 39 and 40. The dilute stream 14 and the outflow stream
16 flowed along respective second output pipes, as indicated by broken lines 4 1 and
42.
The outside vessel 20 of the precipitation unit 12 comprises a cylindrical upper
portion having a diameter of 250 mm and a height of 500 mm and a conic lower
portion having a cone angle of 90 degrees. A total operating volume of the
precipitation unit 12 is about 20 liters. Gypsum particles (200 g) were added as seed
particles in the precipitation zone 28 in the precipitation element 2 1 and the confining
element 22 before start up of the experiment and maintained in suspension by
agitation of the agitation device 23 to enhance the precipitation in the precipitation
unit 12.
The flow rates of both the feed stream 13 and the concentrate stream 17 were set as
0.5 liter per minute (1pm). There was precipitation happening in the precipitation unit
12. To maintain a stable quantity of seed particles in the precipitation unit 12, about
300 ml of slurry was discharged through a discharge stream 30 from the conic lower
portion of the precipitation unit 12 in each cycle (2000 seconds) through a pump 25.
The pump 25 helped a recirculation stream 43 back into the precipitation unit 12 or
the discharge stream 30 for discharge of slurry. A valve 26 controlled the discharge
stream 30 and the recirculation stream 43. At the same time, to keep a constant water
volume in the precipitation unit 12, an overflow stream 29 was designed for
overflowed water from the solid-liquid separation zone 24 of the precipitation unit 12
for safeguard. The discharge stream 30 and the overflow stream join 29 to form the
stream 27. The flow rate of the pump 25 was about 6 litters per minute. A valve 204
was disposed on the lower portion of vessel 20 to facilitate evacuating the vessel 20.
In each cycle, there was about 400 ml of water discharged through the overflow
stream 29. Therefore, a total volume of discharged water was about 700 ml per cycle
while the total feed water volume was about 16.7 liters. The water recovery of the
EDR unit 11 plus the precipitation unit 12 was then calculated to be about 95.8%.
Table 2 shows major compositions of each stream into and out from the EDR unit 11
and the precipitation unit 12. Due to the addition of hydrochloric acid and its reaction
with bicarbonate in the feed tank 50, the stream 13 has higher chloride concentration
and lower bicarbonate concentration than the reject stream in Table 1.
Table 2
The result above also shows that the total dissolved solids (TDS) in the product
stream 14 of the EDR unit 11 is in such a range that the product stream 14 can be sent
back as a feed stream for an unit.
Take an industrial NF unit having a water recovery of about 85% for example and
please refer back to FIG. 1, when a first stream of feed water 106 having a volumetric
flow rate of 1296.4 1pm is transported through the first conduit 104 into the membrane
desalination unit 102, a first stream of reject water 116 having a volumetric flow rate
of 227.1 1pm and a higher salinity than the first feed stream of feed water 106 is
transported from the membrane desalination unit 102 to the electrical separation unit
112 through the third conduit 114 connected with the membrane desalination unit
(industrial unit) and the electrical separation unit 112. The fourth conduit 118
connects the electrical separation unit 112 and is configured to transport a second
stream of product water 120 (having a volumetric flow rate of 217.6 1pm) of lower
salinity than the first stream of reject water out from the electrical separation unit 112
to mix with the first stream of feed water 106. Thus, the volumetric flow rate of total
feed stream to the membrane desalination unit 102 (NF unit) is 1514.0 1pm. With an
85% water recovery rate, the first stream of product water 110 of the membrane unit
has a volumetric flow rate of 1286.9 1pm.
The fifth conduit 124 connects with the precipitation unit 122 and the electrical
separation unit 112 and is configured to transport a second stream of reject water 126
of higher salinity than the first stream 116 of reject water from the electrical
separation unit 112 to the precipitation unit 122. The sixth conduit 128 connected with
the precipitation unit 122 and the electrical separation unit 112 is configured to
transport a second stream of feed water 130 of lower salinity than the second stream
of reject water 126 from the precipitation unit to the electrical separation unit. The
seventh conduit 132 connected with the precipitation unit is configured to release a
discharge stream of water 134. The above experimental result shows that the electrical
separation unit 112 and the precipitation unit 122 has a water recovery rate of 95.8%,
so the average volumetric flow rate of the discharge stream of water 134 is 9.5 1pm.
Thus, the overall device 100 (i.e., NF 102 + EDR 112 + precipitation unit 122) has a
feed stream with a volumetric flow rate of 1296.4 1pm, a product stream with a
volumetric flow rate of 1286.9 1pm and a waste stream with a volumetric flow rate of
9.5 1pm. Therefore, water recovery of the overall device 100 is 99.3%. Bicarbonates
were effectively removed and there is no scaling in the device 100.
While the disclosure has been illustrated and described in typical embodiments, it is
not intended to be limited to the details shown, since various modifications and
substitutions can be made without departing in any way from the spirit of the present
disclosure. As such, further modifications and equivalents of the disclosure herein
disclosed may occur to persons skilled in the art using no more than routine
experimentation, and all such modifications and equivalents are believed to be within
the spirit and scope of the disclosure as defined by the following claims.
WHAT IS CLAIMED IS:
1. A water treatment device (100), comprising:
a membrane desalination unit (102);
a first conduit (104) connected with the membrane desalination unit and configured to
transport a first stream of feed water (106) to the membrane desalination unit;
a second conduit (108) connected with the membrane desalination unit and configured
to transport a first stream of product water ( 110) of lower salinity than the first stream
of feed water out of the membrane desalination unit;
an electrical separation unit ( 112);
a third conduit ( 114) connected with the membrane desalination unit and the electrical
separation unit and configured to transport a first stream of reject water ( 116) of
higher salinity than the first stream of feed water from the membrane desalination unit
to the electrical separation unit;
a fourth conduit ( 118) connected with the electrical separation unit and configured to
transport a second stream of product water (120) of lower salinity than the first stream
of reject water out from the electrical separation unit;
a precipitation unit (122);
a fifth conduit (124) connected with the precipitation unit and the electrical separation
unit and configured to transport a second stream of reject water (126) of higher
salinity than the first stream of reject water from the electrical separation unit to the
precipitation unit;
a sixth conduit (128) connected with the precipitation unit and the electrical
separation unit and configured to transport a second stream of feed water (130) of
lower salinity than the second stream of reject water from the precipitation unit to the
electrical separation unit;
a seventh conduit (132) connected with the precipitation unit and configured to
release a discharge stream of water (134); and
a chemical injection unit (136) in communication with at least one of the electrical
separation unit and the precipitation unit.
2 . The water treatment device according to claim 1, wherein the fourth conduit is
connected with the first conduit and configured to transport the second stream of
product water to mix with the first stream of feed water.
3 . The water treatment device according to claim 1, wherein the membrane
desalination unit comprises a nanofiltration membrane device or a reverse osmosis
membrane device.
4 . The water treatment device according to claim 1, wherein the electrical
separation unit comprises an electrodialysis reversal desalination device or a
supercapacitive desalination device.
5 . The water treatment device according to claim 1, wherein the chemical
injection unit comprises an acid injection unit comprising hydrochloric acid or
sulfuric acid.
6 . The water treatment device according to claim 1, wherein the chemical
injection unit (136) is in communication with at least one of the third conduit, and the
fifth conduit.
7 . The water treatment device according to claim 1, further comprising a
filtration device (138) in communication with the fifth conduit.
8 . A water treatment method comprising:
providing a membrane desalination unit (102);
providing a first conduit (104) connected with the membrane desalination unit and
configured to transport a first stream of feed water (106) to the membrane
desalination unit;
providing a second conduit (108) connected with the membrane desalination unit and
configured to transport a first stream of product water ( 110) of higher purity than the
first stream of feed water out of the membrane desalination unit;
providing an electrical separation unit ( 112);
providing a third conduit ( 114) connected with the membrane desalination unit and
the electrical separation unit and configured to transport a first stream of reject water
( 116) of higher salinity than the first stream of feed water from the membrane
desalination unit to the electrical separation unit;
providing a fourth conduit ( 118) connected with the electrical separation unit and
configured to transport a second stream of product water (120) of lower salinity than
the first stream of reject water out from the electrical separation unit;
providing a precipitation unit (122);
providing a fifth conduit (124) connected with the precipitation unit and the electrical
separation unit and configured to transport a second stream of reject water (126) of
higher salinity than the first stream of reject water from the electrical separation unit
to the precipitation unit;
providing a sixth conduit (128) connected with the precipitation unit and the electrical
separation unit and configured to transport a second stream of feed water (130) of
lower salinity than the second stream of reject water from the precipitation unit to the
electrical separation unit;
providing a seventh conduit (132) connected with the precipitation unit and
configured to release a discharge stream of water (134); and
providing a chemical injection unit (136) in communication with at least one of the
electrical separation unit and the precipitation unit.
9 . The water treatment method according to claim 8, wherein the membrane
desalination unit comprises a nanofiltration membrane device or a reverse osmosis
membrane device and wherein the electrical separation unit comprises an
electrodialysis reversal desalination device or a supercapacitive desalination device.
10. The water treatment method according to claim 9, wherein the chemical
injection unit comprises hydrochloric acid or sulfuric acid.