U.S. patent application number 14/772324 was filed with the patent office on 2016-01-14 for electrochemical water treatment system and method.
The applicant listed for this patent is EVOQUA WATER TECHNOLOGIES, LLC., HYDRONOVATION, INC. Invention is credited to Anil Jha, Ramandeep Mehmi, Peter Naylor, Kee Hoe Ng, Benjamin Rush.
Application Number | 20160010222 14/772324 |
Document ID | / |
Family ID | 51580825 |
Filed Date | 2016-01-14 |
United States Patent
Application |
20160010222 |
Kind Code |
A1 |
Jha; Anil ; et al. |
January 14, 2016 |
ELECTROCHEMICAL WATER TREATMENT SYSTEM AND METHOD
Abstract
Systems and methods for treating water are provided. In certain
examples, the water to be treated is seawater. The systems and
methods may utilize an electrochemical water treatment device
comprising ion exchange membranes. In at least one example, the
electrochemical water treatment device may be configured to perform
a desalination process on seawater. In some examples, the ion
exchange membranes may be configured to provide a ratio of a pH of
the concentrate stream and a pH of the dilution stream to be in a
range of from about 0.9 to about 1.2.
Inventors: |
Jha; Anil; (San Francisco,
CA) ; Rush; Benjamin; (Oakland, CA) ; Mehmi;
Ramandeep; (Livermore, CA) ; Naylor; Peter;
(San Francisco, CA) ; Ng; Kee Hoe; (Singapore,
SG) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HYDRONOVATION, INC
EVOQUA WATER TECHNOLOGIES, LLC. |
San Francisco
Alpharetta |
CA
GA |
US
US |
|
|
Family ID: |
51580825 |
Appl. No.: |
14/772324 |
Filed: |
March 12, 2014 |
PCT Filed: |
March 12, 2014 |
PCT NO: |
PCT/US14/24246 |
371 Date: |
September 2, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61798756 |
Mar 15, 2013 |
|
|
|
Current U.S.
Class: |
205/746 ;
204/242 |
Current CPC
Class: |
Y02W 10/37 20150501;
C02F 1/4693 20130101; C02F 1/4695 20130101; Y02A 20/124 20180101;
C02F 2209/05 20130101; C02F 1/469 20130101; C02F 2303/22 20130101;
C02F 1/4691 20130101; C02F 2209/06 20130101; C02F 2103/06 20130101;
Y02A 20/134 20180101; C02F 1/4602 20130101; C02F 2201/46115
20130101; C02F 2209/001 20130101; C25B 1/46 20130101; Y02W 10/33
20150501; C02F 2201/46 20130101 |
International
Class: |
C25B 1/46 20060101
C25B001/46; C02F 1/469 20060101 C02F001/469 |
Claims
1. A water treatment system comprising: an electrochemical water
treatment device comprising at least one ion exchange membrane; a
concentrate stream in fluid communication with the at least one ion
exchange membrane; and a dilution stream in fluid communication
with the at least one ion exchange membrane, wherein the at least
one ion exchange membrane is configured to provide a ratio of a pH
of the concentrate stream and a pH of the dilution stream to be in
a range of from about 0.9 to about 1.2.
2. The water treatment system of claim 1, wherein the ratio of the
pH of the concentrate stream to the pH of the dilution stream is in
a range of from about 0.9 to about 1.1.
3. The water treatment system of claim 2, wherein the ratio of the
pH of the concentrate stream to the pH of the dilution stream is in
a range of from about 1.0 to about 1.1.
4. The water treatment system of claim 1, wherein the pH of the
concentrate stream is in a range of from about 5.0 to about
7.0.
5. The water treatment system of claim 1, wherein the pH of the
dilution stream is less than about 0.7 pH units lower than the pH
of the concentrate stream.
6. The water treatment system of claim 5, wherein the pH of the
dilution stream is less than about 0.5 pH units lower than the pH
of the concentrate stream.
7. The water treatment system of claim 1, further comprising a feed
stream having a conductivity of at least about 40,000 .mu.S/cm in
fluid communication with the concentrate stream and the dilution
stream.
8. The water treatment system of claim 7, wherein the feed stream
is seawater.
9. The water treatment system of claim 7, wherein a conductivity of
the dilution stream is less than or about 1000 .mu.S/cm.
10. The water treatment system of claim 1, wherein the water
treatment system does not require a separate source of acidic water
for the concentrate stream.
11. The water treatment system of claim 1, wherein the water
treatment system does not require a reverse polarity cycle.
12. A method of treating water comprising: feeding water to an
electrochemical water treatment device comprising at least one ion
exchange membrane; passing the feed water through a concentrating
compartment of the electrochemical water treatment device to
produce a concentrate stream; and passing the feed water through a
dilution compartment of the electrochemical water treatment device
to produce a dilution stream, wherein the at least one ion exchange
membrane is configured to provide a ratio of a pH of the
concentrate stream and a pH of the dilution stream to be in a range
of from about 0.9 to about 1.2.
13. The method of claim 12, wherein the ratio of the pH of the
concentrate stream to the pH of the dilution stream is in a range
of from about 1.0 to about 1.1.
14. The method of claim 12, wherein the method further comprises
recirculating the concentrate stream, and the pH of the
recirculating concentrate stream is in a range of from about 5.0 to
about 7.0.
15. The method of claim 12, wherein the pH of the dilution stream
is less than about 0.7 pH units lower than the pH of the
concentrate stream.
16. The method of claim 15, wherein the pH of the dilution stream
is less than about 0.5 pH units lower than the pH of the
concentrate stream.
17. The method of claim 13, wherein the conductivity of the feed
water is at least about 40,000 .mu.S/cm.
18. The method of claim 17, wherein the method further comprises
storing at least a portion of the dilution stream, and a
conductivity of the stored portion of the dilution stream is less
than or about 1000 .mu.S/cm.
19. The method of claim 12, wherein the method does not require a
separate source of acidic water for the concentrate stream.
20. The method of claim 12, wherein the method does not require a
reverse polarity cycle.
Description
FIELD OF THE DISCLOSURE
[0001] Aspects generally relate to a system and method for treating
water by contacting a source of feed water with at least one ion
exchange membrane housed in an electrochemical water treatment
device.
SUMMARY
[0002] One or more aspects of the present disclosure involve
embodiments directed to a water treatment system. The system can
comprise an electrochemical water treatment device comprising at
least one ion exchange membrane, a concentrate stream in fluid
communication with the at least one ion exchange membrane, and a
dilution stream in fluid communication with the at least one ion
exchange membrane, wherein the at least one ion exchange membrane
is configured to provide a ratio of a pH of the concentrate stream
and a pH of the dilution stream to be in a range of from about 0.9
to about 1.2.
[0003] According to one or more further aspects, the ratio of the
pH of the concentrate stream to the pH of the dilution stream is in
a range of from about 0.9 to about 1.1. In accordance with a
further aspect, the ratio of the pH of the concentrate stream to
the pH of the dilution stream is in a range of from about 1.0 to
about 1.1. In accordance with some embodiments, the pH of the
concentrate stream is in a range of from about 5.0 to about 7.0. In
accordance with some embodiments, the pH of the dilution stream is
less than about 0.7 pH units lower than the pH of the concentrate
stream. In a further aspect, the pH of the dilution stream is less
than about 0.5 pH units lower than the pH of the concentrate
stream. According to one or more further aspects, the system
further comprises a feed stream having a conductivity of at least
about 40,000 .mu.S/cm in fluid communication with the concentrate
stream and the dilution stream. In accordance with some
embodiments, the feed stream is seawater. In accordance with some
embodiments, a conductivity of the dilution stream is less than or
about 1000 .mu.S/cm. In accordance with some embodiments, the water
treatment system does not require a separate source of acidic water
for the concentrate stream. In accordance with some embodiments,
the water treatment system does not require a reverse polarity
cycle.
[0004] One or more aspects of the present disclosure are directed
to a method of treating water. The method can comprise feeding
water to an electrochemical water treatment device comprising at
least one ion exchange membrane, passing the feed water through a
concentrating compartment of the electrochemical water treatment
device to produce a concentrate stream, and passing the feed water
through a dilution compartment of the electrochemical water
treatment device to produce a dilution stream, wherein the at least
one ion exchange membrane is configured to provide a ratio of a pH
of the concentrate stream and a pH of the dilution stream to be in
a range of from about 0.9 to about 1.2.
[0005] According to one or more further aspects, the ratio of the
pH of the concentrate stream to the pH of the dilution stream is in
a range of from about 1.0 to about 1.1. According to one or more
further aspects, the method further comprises recirculating the
concentrate stream, and the pH of the recirculating concentrate
stream is in a range of from about 5.0 to about 7.0. According to
some embodiments, the pH of the dilution stream is less than about
0.7 pH units lower than the pH of the concentrate stream. According
to further embodiments, the pH of the dilution stream is less than
about 0.5 pH units lower than the pH of the concentrate stream. In
accordance with at least one embodiment, the conductivity of the
feed water is at least about 40,000 .mu.S/cm. According to one or
more further aspects, the method further comprises storing at least
a portion of the dilution stream, and a conductivity of the stored
portion of the dilution stream is less than or about 1000 .mu.S/cm.
In accordance with some embodiments, the method does not require a
separate source of acidic water for the concentrate stream. In
accordance with some embodiments, the method does not require a
reverse polarity cycle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] Non-limiting embodiments of the systems and methods
described herein will be described by way of example, and
optionally, with reference to the accompanying drawings. In the
following description, various embodiments of the systems and
methods described herein are described with reference to the
following drawings, in which:
[0007] FIG. 1 is a schematic illustration of an electrochemical
water treatment device in accordance with one or more
embodiments;
[0008] FIG. 2 is a process flow diagram of a water treatment system
in accordance with one or more embodiments;
[0009] FIG. 3 is a process flow diagram of a water treatment system
in accordance with one or more embodiments; and
[0010] FIG. 4 is a chart illustrating at least one result from a
comparison study performed in accordance with one or more
embodiments.
DETAILED DESCRIPTION
[0011] Water that contains hardness species such as calcium and
magnesium may be undesirable for some uses, for example, in
industrial, commercial, residential, or household applications.
Hard water requires more soap and synthetic detergents for home
laundry and washing, and contributes to scaling in pipes, boilers
and industrial equipment. Hardness is caused by compounds of
calcium and magnesium, as well as a variety of other metals, and is
primarily a function of the geology of the area where the ground
water is located. Water acts as an excellent solvent and readily
dissolves minerals it comes in contact with. As water moves through
soil and rock, it dissolves very small amounts of minerals and
holds them in solution. Calcium and magnesium dissolved in water
are the two most common minerals that make water "hard," although
iron, strontium, and manganese may also contribute. The hardness of
water is referred to by three types of measurements: grains per
gallon (gpg), milligrams per liter (mg/L), or parts per million
(ppm). Hardness is usually reported as an equivalent quantity of
calcium carbonate (CaCO.sub.3). One grain of hardness equals 17.1
mg/L or 17.1 ppm of hardness. The typical guidelines for a
classification of water hardness are: zero to 60 mg/L of calcium
carbonate is classified as soft; 61 mg/L to 120 mg/L as moderately
hard; 121 mg/L to 180 mg/L as hard; and more than 180 mg/L as very
hard.
[0012] Alkalinity and hardness are both important components of
water quality. Alkalinity is a measure of the amount of acid
(hydrogen ion) water can absorb (buffer) before achieving a
designated pH. Total alkalinity indicates the quantity of base
present in water, for example, bicarbonates, carbonates,
phosphates, and hydroxides. Hardness represents the overall
concentration of divalent salts for example, calcium, magnesium,
and iron, but does not identify which of these elements is/are the
source of hardness.
[0013] Hard water contains greater than about 60 ppm of calcium
carbonate and is often treated prior to use by being passed through
a water softener. Typically, the water softener is of the
rechargeable ion exchange type and is charged with cation resin in
the sodium form and anion resin in the chloride form. As water
passes through the resin bed, major contributors to hardness, such
as calcium and magnesium species, are exchanged for sodium. In this
manner, the water can be softened by a water softening system as
the concentration of divalent cations and, in particular, calcium
and magnesium ions, decrease.
[0014] Ion exchange is the reversible interchange of ions between a
solid (for example, an ion exchange resin) and a liquid (for
example, water). Since ion exchange resins act as "chemical
sponges," they are ideally suited for effective removal of
contaminants from water and other liquids. Ion exchange technology
is often used in water demineralization and softening, wastewater
recycling, and other water treatment processes. Ion exchange resins
are also used in a variety of specialized applications, for
example, chemical processing, pharmaceuticals, mining, and food and
beverage processing.
[0015] In water softening systems, the hardness ions become
ionically bound to oppositely charged ionic species that are mixed
on the surface of the ion exchange resin. The ion exchange resin
eventually becomes saturated with ionically bound hardness ion
species and must be regenerated. Regeneration involves replacing
the bound hardness species with more soluble ionic species, such as
sodium chloride. The hardness species bound on the ion exchange
resin are replaced by the sodium ions and the ion exchange resins
are ready again for a subsequent water-softening step. However, an
equivalent of sodium is added to the treated water for every
equivalent of calcium that is removed. Thus, although the water is
softened, the hardness is replaced with sodium ions that some
consumers may find undesirable. Furthermore, when these ion
exchange beds are recharged, the resulting brine must be disposed
of and is often discharged to a septic system where the brine
becomes available to re-enter the ground water. In certain regions,
discharge of brine to a domestic septic system, a municipal waste
stream, or to the environment is regulated or prohibited.
[0016] Other methods of softening water include the use of reverse
osmosis devices that can supply high purity water, but generally do
so at a slow rate and require the use of a high pressure pump.
Furthermore, many reverse osmosis membranes can be fouled by the
presence of dissolved materials such as silica, which may often be
found in well water.
[0017] Quality drinking water is often associated with highly
purified water. However, as long as the water is free of microbial
contamination, the best drinking water may not necessarily be the
most chemically pure. For example, water that has been purified to
a high resistivity, for example, greater than about 1 megaOhm, may
be so devoid of ionic content that it becomes "hungry" and
corrosive to material, such as copper, that may be used in water
piping systems. Taste may also be affected by, for instance, the
removal of bicarbonate species. Furthermore, beneficial or
desirable chemicals that have been added to the water, for example,
fluoride and chlorine species, may be removed along with
undesirable species, resulting in water that may need to be
re-fortified. In some regions, minimum levels of calcium may be
necessary in order to comply with health and safety regulations and
a high purity system that removes greater than, for example, 90% to
99% of the calcium from the water supply, may be inappropriate.
[0018] Devices for purifying fluids using electrical fields are
commonly used to treat water and other liquids containing dissolved
ionic species. Within these devices are concentrating and diluting
(or depletion) compartments separated by ion-selective membranes.
An example of such a device is shown in FIG. 1, and includes an
electrochemical water treatment apparatus featuring alternating
electroactive semipermeable anion and cation exchange membranes.
Spaces between the membranes are configured to create liquid flow
compartments with inlets and outlets. An applied electric field
imposed via electrodes causes dissolved ions, attracted to their
respective counter-electrodes, to migrate through the anion and
cation exchange membranes. This generally results in the liquid of
the diluting compartment being depleted of ions, and the liquid in
the concentrating compartment being enriched with the transferred
ions.
[0019] As used herein, the phrases "treatment device" or
"purification device" or "apparatus" pertain to any device that can
be used to remove or reduce the concentration level of any
undesirable species from a fluid to be treated. Examples of
suitable treatment apparatuses include, but are not limited to,
ion-exchange resin devices, reverse osmosis, electrodeionization,
electrodialysis, ultrafiltration, microfiltration, and capacitive
deionization devices.
[0020] In certain non-limiting embodiments, the methods and systems
disclosed herein comprise an electrochemical water treatment
device. As used herein, the phrase "electrochemical water treatment
device" refers to any number of electrochemical water treatment
devices, non-limiting examples including, but not limited to,
electrodeionization devices, electrodialysis devices, capacitive
deionization devices, and any combination thereof. The
electrochemical water treatment devices may include any device that
functions in accordance with the principles of the systems and
methods described herein as long as they are not inconsistent or
contrary these operations.
[0021] In certain embodiments, the electrochemical treatment device
may include electrochemical deionization units. Non-limiting
examples of such devices include electrodialysis (ED),
electrodialysis reversal (EDR), electrodeionization (EDI),
capacitive deionization, continuous electrodeionization (CEDI), and
reversible continuous electrodeionization (RCEDI).
[0022] Electrodeionization (EDI) is a process that removes, or at
least reduces, one or more ionized or ionizable species from water
using electrically active media and an electric potential to
influence ion transport. The electrically active media typically
serves to alternately collect and discharge ionic and/or ionizable
species and, in some cases, to facilitate the transport of ions,
which may be continuously, by ionic or electronic substitution
mechanisms. EDI devices can comprise electrochemically active media
of permanent or temporary charge, and may be operated batch-wise,
intermittently, continuously, and/or even in reversing polarity
modes. EDI devices may be operated to promote one or more
electrochemical reactions specifically designed to achieve or
enhance performance. Further, such electrochemical devices may
comprise electrically active membranes, such as semi-permeable or
selectively permeable ion exchange or bipolar membranes. Continuous
electrodeionization (CEDI) devices are EDI devices known to those
skilled in the art that operate in a manner in which water
purification can proceed continuously, while ion exchange material
is continuously recharged. CEDI techniques can include processes
such as continuous deionization, filled cell electrodialysis, or
electrodiaresis. Under controlled voltage and salinity conditions,
in CEDI systems, water molecules can be split to generate hydrogen
or hydronium ions or species and hydroxide or hydroxyl ions or
species that can regenerate ion exchange media in the device and
thus facilitate the release of the trapped species therefrom. In
this manner, a water stream to be treated can be continuously
purified without requiring chemical recharging of ion exchange
resin.
[0023] Electrodialysis (ED) devices operate on a similar principle
as CEDI, except that ED devices typically do not contain
electroactive media between the membranes. Because of the lack of
electroactive media, the operation of ED may be hindered by feed
waters of low salinity because of elevated electrical resistance.
Also, because the operation of ED on high salinity feed waters can
result in elevated electrical current consumption, ED apparatuses
have heretofore been most effectively used on source waters of
intermediate salinity. In ED based systems, because there is no
electroactive media, splitting water is inefficient and operating
in such a regime is generally avoided.
[0024] A capacitive deionization (CapDI) device is used to remove
an ionic material from a medium, for example, hard water, by
applying a voltage to a pair of electrodes having nanometer-sized
pores to polarize the pair of electrodes. This allows ionic
material to be adsorbed onto a surface of at least one of the pair
of electrodes. In the CapDI device, a low DC voltage is applied to
the pair of electrodes and the medium containing dissolved ions
then flows between the two electrodes. Anions dissolved in the
medium are adsorbed and concentrated in the positive electrode, and
cations dissolved in the medium are adsorbed and concentrated in
the negative electrode. When a current is supplied in a reverse
direction, for example, by electrically shorting the two
electrodes, the concentrated ions are desorbed from the negative
electrode and the positive electrode. Since the CapDI device does
not use a high potential difference, the energy efficiency is high.
The CapDI device may remove detrimental ions as well as hardness
components, when ions are adsorbed onto the electrodes. The CapDI
device does not use a chemical to regenerate the electrodes, and
therefore the CapDI device has a relatively low environmental
impact.
[0025] As shown in FIG. 1, CEDI and ED devices may include a
plurality of adjacent cells or compartments that are separated by
selectively permeable membranes that allow the passage of either
positively or negatively charged species, but typically not both.
Dilution or depletion compartments are typically interspaced with
concentrating or concentration compartments in such devices. In
some embodiments, a cell pair may refer to a pair of adjacent
concentrating and diluting compartments. As water flows through the
depletion compartments, ionic and other charged species are
typically drawn into concentrating compartments under the influence
of an electric field, such as a DC field. Positively charged
species are drawn toward a cathode, typically located at one end of
a stack of multiple depletion and concentration compartments, and
negatively charged species are likewise drawn toward an anode of
such devices, typically located at the opposite end of the stack of
compartments. The electrodes are typically housed in electrolyte
compartments that may be partially isolated from fluid
communication with the depletion and/or concentration compartments.
Once in a concentration compartment, charged species are typically
trapped by a barrier of selectively permeable membrane that may be
at least partially defining the concentration compartment. For
example, anions may be prevented from migrating further toward the
cathode, out of the concentration compartment, by a cation
selective membrane. Once captured in the concentrating compartment,
trapped charged species can be removed in a concentrate stream.
[0026] In CEDI and ED devices, the DC field is typically applied to
the cells from a source of voltage and electric current applied to
the electrodes (anode or positive electrode, and cathode or
negative electrode). The voltage and current source (collectively
"power supply") can be itself powered by a variety of means such as
an AC power source, or for example, a power source derived from
solar, wind, or wave power. At the electrode/liquid interfaces,
electrochemical half cell reactions occur that initiate and/or
facilitate the transfer of ions through the membranes and
compartments. For example, in FIG. 1, when a voltage is applied
across the cathode and anode, bicarbonate, calcium, hydroxide and
hydrogen ions may form in the solution.
[0027] The specific electrochemical reactions that occur at the
electrode/interfaces can be controlled to some extent by the
concentration of salts in the specialized compartments that house
the electrode assemblies. For example, a feed to the anode
electrolyte compartments that is high in sodium chloride will tend
to generate chlorine gas and hydrogen ion, while such a feed to the
cathode electrolyte compartment will tend to generate hydrogen gas
and hydroxide ion. Generally, the hydrogen ion generated at the
anode compartment will associate with a free anion, such as
chloride ion, to preserve charge neutrality and create hydrochloric
acid solution, and analogously, the hydroxide ion generated at the
cathode compartment will associate with a free cation, such as
sodium, to preserve charge neutrality and create sodium hydroxide
solution. The reaction products of the electrode compartments, such
as generated chlorine gas and sodium hydroxide, can be utilized in
the process as needed for disinfection purposes, for membrane
cleaning and defouling purposes, and for pH adjustment
purposes.
[0028] The performance of electrochemical water treatment devices,
especially in hard water applications, may be limited by
precipitation formed from hard ions such as calcium and magnesium.
When water exceeds the solubility limit, hard ions, such as calcium
and magnesium, drop out as crystals. One of the methods for
determining the solubility limit is the Langelier Saturation Index
(LSI). The Langelier Saturation Index (sometimes called the
Langelier Stability Index) is a calculated number used to predict
the calcium carbonate stability of water. LSI may be calculated
according to a standard method, for example, ASTM D 3739. The
resulting value indicates whether the water will precipitate,
dissolve, or be in equilibrium with calcium carbonate.
[0029] The Langelier saturation level approaches the concept of
saturation using pH as a main variable. The LSI is expressed as the
difference between the actual system pH and the saturation pH. LSI
can be interpreted as the pH change required to bring water to
equilibrium. Water with an LSI of 1.0 is one pH unit above
saturation. Reducing the pH by 1 unit will bring the water into
equilibrium. This occurs because the portion of total alkalinity
present as CO.sub.3.sup.-2 decreases as the pH decreases. For
LSI>0, water is super saturated and tends to precipitate a scale
layer of CaCO.sub.3. For LSI=0 or close to 0, water is saturated
(in equilibrium) with CaCO.sub.3. A scale layer of CaCO.sub.3 is
neither precipitated nor dissolved. Water quality, changes in
temperature, or evaporation could change the index. For LSI<0,
water is under saturated and tends to dissolve solid
CaCO.sub.3.
[0030] If the actual pH of the water is below the saturation pH,
the LSI is negative and the water has a very limited scaling
potential. If the actual pH exceeds the saturation pH, then LSI is
positive, and being supersaturated with CaCO.sub.3, the water has a
tendency to form scale. At increasing positive index values, the
scaling potential increases.
[0031] LSI values are also dependent on temperature, with LSI
becoming more positive as the water temperature increases. This may
have particular implications in situations where well water is
used. The temperature of the water when it first exits the well is
often significantly lower than the temperature inside the building
served by the well, or inside the laboratory or process unit where
the LSI measurement is made. The resulting increase in temperature
can cause scaling, especially in hot water heaters. Conversely,
systems that reduce water temperature will have less scaling.
[0032] One of the potential problems in electrochemical water
treatment processes is the risk of forming insoluble calcium or
magnesium deposits. These deposits are formed at conditions of high
Ca 2.sup.+ and/or Mg 2.sup.+ concentration and at high pH values.
Thus, LSI increases in the concentrating compartments of
electrochemical water treatment devices due to the increase in hard
ion concentration, or where the water is removed without reduction
of hard ion concentration. Most electrochemical water treatment
devices are designed to maintain the LSI at values of about 0 to 2.
In order to maintain these values, more water is required in the
concentrating compartment, resulting in higher volumes of waste
water. This contributes to inefficiencies in operating the
electrochemical water treatment device.
[0033] Frequently, electrochemical water treatment devices are
designed to remove as many ions as possible. For many industrial
and commercial uses, this highly purified water may be beneficial;
however, this level of purity may be undesirable for other
applications, for example, a household or municipal water supply,
where some level of cation content may be beneficial. Furthermore,
highly purified water may be corrosive and may be prone to attack
copper pipes that are often present in water distribution systems.
Some water distribution systems may include lead soldered joints,
and heavy metals, such as lead, may also leach into water passing
through the pipes.
[0034] As used herein, "hardness" refers to a condition that
results from the presence of polyvalent cations, for example
calcium, magnesium, or other metals, in water, that adversely
affect the cleansing capability of the water and the "feel" of the
water, and may increase scaling potential. Hardness is usually
quantified by measuring the concentration of calcium and magnesium
species. In certain embodiments, undesirable species can include
hardness ion species.
[0035] Electrical conductivity (EC) is a measure of water's ability
to "carry" an electrical current, and, indirectly, a measure of
dissolved solids or ions in the water. Deionized water has a very
low conductivity value (nearly zero); hence, the more dissolved
solids and ions occurring in the water, the more electrical current
the water is able to conduct. A conductivity probe in conjunction
with a temperature sensor is capable of determining the electrical
resistance of a liquid. Fresh water usually reflects electrical
conductivity in units of micro Siemens (.mu.S/cm).
[0036] Total Dissolved Solids (TDS) are the total amount of mobile
charged ions, including minerals, salts, or metals dissolved in a
given volume of water, expressed in units of mg per unit volume of
water (mg/L), also referred to as parts per million (ppm). TDS is
directly related to the purity and quality of water and water
purification systems and affects everything that consumes, lives
in, or uses water, whether organic or inorganic. The term
"dissolved solids" refers to any minerals, salts, metals, cations
or anions dissolved in water, and includes anything present in
water other than the pure water (H.sub.20) molecule and suspended
solids. In general, the total dissolved solids concentration is the
sum of the cations and anions in the water. Parts per million (ppm)
is the weight-to-weight ratio of any ion to water. TDS is based on
the electrical conductivity (EC) of water, with pure water having
virtually no conductivity.
[0037] As used herein, the term "system yield" also refers to
treatment system recovery, meaning the measure of waste versus
production. System yield/recovery rates are determined using the
following calculation:
System yield=[Product volume/(Waste volume+Product volume)]*100
[0038] The systems and methods described herein are directed to
water treatment or purification systems and methods of providing
treated water in industrial, commercial, residential, household,
and municipal settings. For example, one or more embodiments may be
suitable for treating water supplied to a municipal water treatment
facility. According to another example, one or more embodiments may
be suitable for treating water supplied to an industrial process,
such as a manufacturing or production facility. One or more
embodiments will be described using water as the fluid but should
not be limited as such. For example, where reference is made to
treating water, it is believed that other fluids can be treated
according to the systems and methods described herein. Moreover,
the treatment systems and apparatuses described herein are believed
to be applicable in instances where reference is made to a
component of the system or to a method that adjusts, modifies,
measures or operates on the water or a property of the water. The
fluid to be treated may also be a fluid that is a mixture
comprising water.
[0039] In at least one aspect, the systems and methods described
herein provide purified or treated water from a variety of source
types. Possible water sources include well water, surface water,
municipal water, seawater, and rain water. The treated product may
be for general use, industrial use, or for human consumption or
other domestic uses, for example, bathing, laundering, and
dishwashing. As used herein, the term "treated" in reference to
water or fluid, references water exhibiting properties that are
suitable for one or more various applications, such as residential,
commercial, industrial, municipal, and the like. For example, in
certain embodiments, treated water may have a conductivity in a
range of from about 100 to about 400 .mu.S/cm. In at least one
embodiment, the treated water may have a conductivity in a range of
from about 300 to about 400 .mu.S/cm. In some embodiments, treated
water may have a conductivity in a range of from about 250 to about
350 .mu.S/cm. According to some embodiments, the treated water may
have a conductivity of less than 500 .mu.S/cm. In at least some
embodiments, the treated water may have a conductivity of less than
or about 1000 .mu.S/cm. In some embodiments, the treated water may
have an alkalinity in a range of from about 50 to about 200 ppm. In
certain embodiments, the treated water may have an alkalinity in a
range of from about 50 to about 150 ppm. In even other embodiments,
the treated water may have an alkalinity in a range of from about
80 to about 120 ppm. In one or more embodiments, treated water may
have a hardness in a range of from about 1 to about 10 gpg.
According to some embodiments, treated water may have a hardness in
a range of from about 1 to about 5 gpg. In certain other
embodiments, treated water may have a hardness of about 4 gpg. The
conductivity, alkalinity, and hardness of the treated water may be
any value or range of values for these respective properties that
is suitable for a desired residential and commercial application,
and may be specifically tailored for a specific use or user.
[0040] In another aspect, the systems and methods described herein
may be operated to reduce the likelihood of formation of any scale
or foulants that are generated while producing treated water. The
formation of scale or foulants in the treatment system, including
its components, such as pumps, valves, and fluid lines, may be
inhibited by substituting the flowing liquid from one having a high
tendency to form scale to a liquid having a low to small tendency
to produce scale, such as water having a low LSI.
[0041] The treatment system in accordance with one or more
embodiments may receive water from a source and subsequently pass
it through a treatment process to produce a product stream
possessing targeted characteristics. The treatment system may have
a water storage system in fluid communication with at least one or
more treatment devices. Non-limiting examples of suitable treatment
device may include: electrochemical water treatment devices,
reverse osmosis devices, electrodialysis devices, ion exchange
resin devices, capacitive deionization devices, microfiltration
devices, and/or ultrafiltration devices.
[0042] In accordance with one or more embodiments a water treatment
system is provided. In some embodiments, the water treatment system
includes an electrochemical water treatment device. The
electrochemical water treatment device may include at least one ion
exchange membrane. The at least one ion exchange membrane may be an
anion exchange membrane, a cation exchange membrane, or a
combination of both. For example, the device may include a series
of alternating anion and cation exchange membranes. The
electrochemical water treatment device may further comprise at
least one compartment to house the ion exchange membrane(s). In
certain embodiments, the electrochemical water treatment device may
include a plurality of alternating depleting compartments and
concentrating compartments positioned between a pair of electrodes.
The pair of electrodes may be a cathode and an anode. The water
treatment system may include a concentrate stream and a dilution
stream. The concentrate stream and dilution stream may be in fluid
communication with at least one ion exchange membrane.
[0043] In certain embodiments, the at least one ion exchange
membrane may be configured to provide a ratio of a pH of the
concentrate stream and a pH of the dilution stream to be less than
about 1.0. This may be possible due to one or more properties or
characteristics of the ion exchange membrane(s) used to create the
concentrate and dilution streams. For example, the ion exchange
membranes may be configured to produce a dilution stream that has a
pH that is consistently higher than a pH of the concentrate
stream.
[0044] According to at least one embodiment, the water treatment
system may be used to perform a desalination process. For example,
a source of feed water to the system may have a conductivity of at
least about 30,000 .mu.S/cm. In another example, the source of feed
water may have a conductivity of at least about 40,000 .mu.S/cm. In
certain instances, the seawater may have a conductivity of about
50,000 .mu.S/cm. In at least one embodiment, the feed stream to the
water treatment system may comprise seawater. The water treatment
system may include one or more electrochemical water treatment
devices that include one or more ion exchange membranes, as
described above. In certain embodiments, the at least one ion
exchange membrane may be configured to provide a ratio of a pH of
the concentrate stream and a pH of the dilution stream to be in a
range of from about 0.9 to about 1.2 In some embodiments, the ratio
may be in a range of from about 0.9 to about 1.1. In still other
embodiments, the ratio may be in a range of from about 1.0 to about
1.1. In at least one embodiment, the ratio may be about 1.0. In one
or more embodiments, the concentrate stream may have a pH that is
less than 8.0. In certain embodiments, the concentrate stream may
have a pH that is less than 7.0. In still other embodiments, the
concentrate stream may have a pH that is less than 6.0. In some
embodiments, the concentrate stream may have a pH in a range of
from about 5.0 to about 7.0. In various embodiments, the
concentrate stream may be acidic, and have a pH value that is less
than 7.0. In accordance with some embodiments, the pH of the
dilution stream is less than about 0.7 pH units lower than the pH
of the concentrate stream. In further embodiments, the pH of the
dilution stream is less than about 0.5 units lower than the pH of
the concentrate stream. In at least one embodiment, the pH of the
dilution stream may be about the same as the pH of the concentrate
stream.
[0045] According to certain aspects, the desalination process may
be performed in one or more separate stages. For example, a
multi-stage process may be employed, with each stage removing a
certain percentage of unwanted ions. For example, each stage may
remove between five and ten percent of the unwanted ions from the
feed water. In other examples, each stage may remove about 20% of
the unwanted ions. In one example, the desalination process is
configured to produce a dilution stream with a conductivity of less
than about 1000 .mu.S/cm. This may be accomplished using one or
more process stages.
[0046] Although the above-discussed desalination process was
directed toward seawater, other types of feed liquids may also be
used to achieve the same results. For example, brine, having a
conductivity of about 500,000 .mu.S/cm, or brackish water, having a
conductivity of about 100,000 .mu.S/cm, may be treated using the
systems and methods described herein to achieve similar results.
Other liquids, such as leachate from landfills or drainage from
mines and wetlands or bogs are also within the scope of this
disclosure. Notably, the ion exchange membranes may be configured
to withstand a certain level of chlorine, which may enhance their
ability to treat liquids with such high conductivities.
[0047] In at least one aspect, the systems and methods described
herein provide a concentrate stream that may circulate through the
electrochemical water treatment device. In certain aspects, the
concentrate stream may have an LSI that inhibits scale formation.
For example, the concentrate stream may have an LSI of less than or
about 1, less than or about 0.5, or less than or about 0.2.
[0048] In some embodiments, the systems and methods described
herein may provide liquids, such as water, having certain desired
properties related to conductivity, alkalinity, pH, TDS and LSI.
For example, the dilution stream may have a conductivity in a range
of from about 250 to about 350 .mu.S/cm. In various embodiments,
the conductivity of the dilution stream may be about 300 .mu.S/cm.
In at least one embodiment, the conductivity of the dilution stream
may be less than about 1000 .mu.S/cm. In one or more embodiments,
the dilution stream may have a pH that is greater than 5.0. In
certain embodiments, the dilution stream may have a pH that is
greater than 6.0. In other embodiments, the dilution stream may
have a pH that is greater than 7.0. In some embodiments, the
dilution stream may have a pH in a range of from about 5.0 to about
8.0. In other embodiments, the dilution stream may have a pH in a
range of from about 5.0 to about 7.0. In various embodiments, the
dilution stream may have an alkalinity in a range of from about 80
ppm to about 150 ppm. For example, the dilution stream may have an
alkalinity in a range of from about 90 ppm to about 120 ppm. In
some embodiments, the dilution stream may have an alkalinity of
about 100 ppm. In multiple embodiments, the water treatment system
may be configured to produce a dilution stream with a hardness of
about 4 gpg.
[0049] In at least one embodiment, the systems and methods provide
a dilution or product stream that is in compliance with water
quality criteria established by the World Health Organization
(WHO). For example, current WHO standards require drinking water to
have a pH between 6.5-8.5 and a TDS of no more than 500 ppm.
[0050] In one or more embodiments, the water treatment system does
not require a separate source of acidic water for the concentrate
stream, as may be the case for other types of water treatment
systems. The separate source of acidic water may be necessary in
other types of systems to maintain a desired pH of the concentrate
stream. For example, other types of systems may require a separate
cation exchange device that is in fluid communication with the
concentrate stream. The cation exchange device may provide an
intermittent or continuous supply of acidic water to the
concentrate stream. This requirement may increase the cost and
maintenance of the overall system. The water treatment systems
described herein therefore offer the advantage of not requiring
this type of equipment, thus minimizing or eliminating these
additional costs.
[0051] In at least one embodiment, the water treatment system does
not require a reverse polarity cycle. As will be appreciated by one
of ordinary skill in the art, a controller may reverse the
direction of the applied field from a power source to the
electrochemical water treatment device according to a predetermined
schedule or according to an operating condition, such as water
quality, or any other operating parameter in the treatment system.
The function of the concentrating and depleting compartments is
also switched, as well as the functionality of the respective
concentrate and dilution streams. Performing a reverse polarity
cycle may add additional time, costs, complexity, and size to the
system. The water treatment systems described herein thus allow a
distinct advantage over other types of systems that may require
reverse polarity cycles as part of the operating process.
[0052] Various aspects of the water treatment systems and methods
disclosed herein may provide operationally cost effective
advantages over other systems currently available on the market.
For example, with reference to FIG. 4, and as will be discussed in
further detail below, the electrochemical water treatment device
may be capable of providing the same treated water (for example,
provide water with a hardness of 4 gpg), but the process may be
much shorter in duration. This efficiency may be linked to a
characteristic of the ion exchange membranes that are used in the
electrochemical water treatment device. For example, the membranes
may be particularly selective to calcium, thus affecting hardness,
and the speed at which the feed water is cleaned. Further, the LSI
of the concentrate stream may be very low (for example, 0.1-0.2),
keeping scaling to a minimum without the requirement for any
additional equipment or materials. This benefit may also be
attributed to one or more characteristics of the ion exchange
membranes. For example, the membranes may be particularly less
selective to bicarbonate, thus affecting the alkalinity and the
subsequent pH.
[0053] In various embodiments, the ion exchange membranes may
possess properties related to selectivity of one or more ions. For
example, the membranes may be selective toward calcium and
de-selective toward bicarbonate. This may contribute toward one or
more advantages of the disclosed system over other types of water
treatment systems. For example, other systems may require an
additional source of acidic water to maintain or provide a low pH
in the concentrate stream, and may require periodic reverse
polarity cycling to maintain certain levels of operating
efficiencies. The elimination of these additional pieces of
equipment and processes may allow the disclosed electrochemical
water treatment devices to decrease processing time, reduce module
size, reduce module duty cycle, increase production rate, and
reduce the cost, complexity, and size of the overall system.
[0054] In accordance with one or more embodiments, a method of
treating water is provided. In at least one embodiment, the feed
water may have a conductivity of at least about 40,000 .mu.S/cm. In
at least one embodiment, the feed water may be seawater. The method
may further comprise passing the feed water through the
concentrating and diluting compartment of the electrochemical water
treatment device to produce a product stream with a conductivity of
about 300 .mu.S/cm. In other embodiments, the product stream may
have a conductivity in a range of from about 300 .mu.S/cm to about
400 .mu.S/cm. According to at least one embodiment, the method
comprises storing at least a portion of the dilution stream, and a
conductivity of the stored portion of the dilatation stream may be
in a range of from about 300 .mu.S/cm to about 400 .mu.S/cm. In one
or more embodiments, passing the feed water through the
concentrating and diluting compartments of the electrochemical
water treatment device produces a concentrate stream and a product
stream. In at least one embodiment, a ratio of a pH of the product
stream to a pH of the concentrate stream is less than about 1.0. In
other embodiments, the ratio is in a range of from about 0.9 to
about 1.2. In further embodiments, the range may be from about 1.0
to about 1.1. According to at least one embodiment, the pH of the
concentrate stream is in a range of from about 5.0 to about 7.0. In
a further embodiment, the method may comprise recirculating the
concentrate stream, and the recirculating concentrate stream may
have a pH in a range of from about 5.0 to about 7.0. In one
embodiment, the pH of the dilution stream is less than about 0.7 pH
units lower than the pH of the concentrate stream. In a further
embodiment, the pH of the dilution stream is less than about 0.5
units lower than the pH of the concentrate stream. According to
certain embodiments, the pH of the concentrate stream and the
dilution stream may both be acidic, or both may be less than about
7.0. In some embodiments, an LSI of the concentrate stream is less
than about 1.0. In various embodiments, the method does not require
the addition of a separate source of acidic water to the
concentrate stream. In certain embodiments, the method does not
require a reverse polarity cycle.
[0055] According to one or more aspects, the electrochemical water
treatment device may include at least one ion exchange membrane.
The ion exchange membranes may include anion and cation exchange
membranes. In various aspects, ion exchange membranes may have low
electrical resistance, high permselectivity, high chemical
stability, and high mechanical strength. In at least one aspect, an
ion exchange membrane may have a resistivity of less than about 1.5
Ohm-cm.sup.2 and an apparent permselectivity of at least about 95%.
Ion exchange membranes that are suitable for use in the systems and
methods disclosed herein are available from Evoqua Water
Technologies (Lowell, Mass.).
[0056] The electrical resistivity of an ion exchange membrane is
generally an expression of how strongly the membrane resists the
flow of electric current. When resistivity is high, more current,
and thus more energy, may need to be applied to the electrochemical
cell to facilitate ion transfer across the membrane to perform the
desired electrochemical separation process. As used herein, the
terms "electrical resistance" and "electrical conductivity" may be
used interchangeably and refer to the resistance of a material to
the flow of electrical current and may be expressed as electrical
resistance per unit area (.OMEGA.cm.sup.2). The electrical
resistance of a membrane may be determined by the ion-exchange
capacity and the mobility of an ion within a membrane matrix. In
general, electrical resistance is proportional to ion
concentration, meaning that electrical resistance increases with
increasing ion concentration. Thus, in general, the lower the
resistivity of the ion exchange membrane, the more efficient the
membrane. In electrochemical processes, it may be desirable to use
ion exchange membranes with low electrical resistance, since they
may save energy and reduce ohmic losses during operation.
[0057] As used herein, the term "permselectivity" refers to an ion
exchange membrane's ability to be permeable to one chemical species
but impermeable with respect to another chemical species. For
example, in certain instances the ion exchange membrane may be
permeable to counter-ions, but impermeable to co-ions. This means,
for example, that when an electric current is applied to an
electrochemical cell having both anion and cation exchange
membranes, cations in solution will cross the cation membrane but
anions will not cross. When, as in this example, anions are allowed
to cross the cation membrane, the overall efficiency of the process
is reduced. In certain instances it may be desirable to have
membranes with a high permselectivity, where the membranes are
highly permeable to counter-ions and highly impermeable to
co-ions.
[0058] The ion exchange membrane may be constructed from a
polymeric substrate that is covered by a polymeric layer. In
various aspects, the polymeric layer may be cross-linked. In at
least one embodiment, the cross-linked polymeric layer may react
with the polymeric substrate to yield a hydrophobic surface.
[0059] The ion exchange membranes may comprise polymeric materials
that facilitate the transport of either positive or negative ions
across the membrane. Ion exchange membrane properties, including
resistivity and permselectivity, may be controlled, in part, by the
amount, type, and distribution of fixed ionic groups in the
membrane. For example, strong base anion exchange membranes may
generally comprise quaternary amines, and weak base anion exchange
membranes may generally comprise tertiary amines. The amines may
have fixed positive charges that allow anionic species to permeate
across the membrane.
[0060] In various embodiments, the ion exchange membranes may be
generally heterogeneous membranes. The heterogeneous membranes may
include a polymeric layer that is coated on top of a substrate and
the polymeric layer may provide fixed charges on the outer surface
of the membrane. In other embodiments, the ion exchange membranes
may be generally homogeneous. Homogeneous membranes may be produced
by the polymerization of monomers and may include a polymeric
microporous substrate. Reactive monomers may be used to fill the
pores of the substrate, yielding a membrane with a highly uniform
microstructure. The reactive monomers may be selected to
functionally remove specific ions. For example, the reactive
monomer may be selected to remove bicarbonate.
[0061] In one or more aspects, the methods and systems described
herein provide treated water while decreasing the ionic load
discharged from the treatment system. For example, the total amount
of waste water discharged as a result of the treatment process may
be significantly less than conventional treatment processes, and
may be less than 25%, less than 20%, or less than 10% of the total
volume of water treated.
[0062] One or more embodiments of the treatment systems disclosed
here may include one or more fluid control devices, such as pumps,
valves, regulators, sensors, pipes, connectors, controllers, power
sources, and any combination thereof.
[0063] In accordance with one or more embodiments, the treatment
systems disclosed here may comprise one or more pumps. A variety of
pumps for pumping and/or circulating fluid may be used in
conjunction with the treatment system. Pumps may be internal and/or
external to one or more of the components of the treatment system,
and/or may be otherwise integrated with the treatment system.
Non-limiting examples of pumps include electrical pumps, air driven
pumps, and hydraulic pumps. The pump may be driven by a power
source that can be any conventional power source, for example,
gasoline driven motors, diesel driven motors, solar-powered motors,
electric motors, and any combination thereof.
[0064] In accordance with one or more embodiments, the methods and
systems disclosed here further comprise one or more valves.
Non-limiting examples of valves suitable for control according to
one or more embodiments include, but are not limited to, check
valves, gate valves, bypass valves, solenoid valves, other types of
hydraulic valves, other types of pneumatic valves, relief valves,
and any combination thereof. Suitable valves include one-way and/or
multi-way valves. In certain non-limiting embodiments, the valve
can be a pilot valve, a rotary valve, a ball valve, a diaphragm
valve, a butterfly valve, a flutter valve, a swing check valve, a
clapper valve, a stopper-check valve, a lift-check valve, and any
combination thereof. The valves may be manually actuated (for
example, by an operator) and/or hydraulically, pneumatically,
solenoid, or otherwise actuated, including control actuated by a
process controller or control system. The valves may be an on/off
type of valve, or may be a proportional type of valve.
[0065] The treatment system, in some embodiments of the systems and
methods described herein, further comprises one or more sensors or
monitoring devices configured to measure at least one property of
the water or an operating condition of the treatment system.
Non-limiting examples of sensors include composition analyzers, pH
sensors, temperature sensors, conductivity sensors, pressure
sensors, and flow sensors. In certain embodiments, the sensors
provide real-time detection that reads, or otherwise senses, the
properties or conditions of interest. A few non-limiting examples
of sensors suitable for use in one or more embodiments include
optical sensors, magnetic sensors, radio frequency identification
(RFID) sensors, Hall effect sensors, and any combination
thereof.
[0066] In certain non-limiting embodiments of the systems and
methods described herein, the treatment system further comprises a
flowmeter for sensing the flow of fluid. A non-limiting example of
a flowmeter suitable for certain aspects of the treatment system
disclosed here includes a Hall effect flowmeter. Other non-limiting
examples of flowmeters suitable for certain aspects of the
treatment system include mechanical flowmeters, including a
mechanical-drive Woltman-type turbine flowmeter.
[0067] According to one or more aspects, the systems and methods
disclosed herein may include a control system disposed or
configured to receive one or more signals from one or more sensors
in the treatment system. The control system can be further
configured to provide one or more output or control signals to one
or more components of the treatment system. One or more control
systems can be implemented using one or more computer systems. The
computer system may be, for example, a general-purpose computer
such as those based on readily available systems. In some
embodiments, the control system can include one or more processors
connected to one or more memory devices. Software, including
readily available programming code that implements embodiments of
the systems and methods disclosed herein, may be used by the
control system.
[0068] Components of a control system may be coupled by one or more
interconnection mechanisms, which may include one or more busses,
for example, between components that are integrated within a same
device, and/or one or more networks, for example, between
components that reside on separate discrete devices.
[0069] The control system can further include one or more input
devices, for example, a keyboard, mouse, trackball, microphone,
touch screen, and one or more output devices, for example, a
printing device, display screen, or speaker. In addition, the
control system may contain one or more interfaces that can connect
to a communication network.
[0070] According to one or more embodiments, one or more input
devices may include one or more sensors for measuring the one or
more parameters of the fluids in the treatment system. For example,
sensors may be configured as input devices that are directly
connected to the control system. For purposes of this disclosure,
the term "monitoring" may be defined to include, in a non-limiting
manner, acts such as recording, observing, evaluating, identifying,
etc. In certain embodiments, the treatment system also includes a
controller for adjusting, monitoring, or regulating at least one
operating parameter and its components of the treatment system. In
certain embodiments, the controller regulates the operating
conditions of the treatment system in an open-loop or closed-loop
control scheme. In yet another embodiment, the controller can
further comprise a communication system, for example, a remote
communication device, for transmitting or sending the measured
operating condition or operating parameter to a remote station.
[0071] FIG. 2 is a process flow diagram of a water treatment system
20 in accordance with one or more embodiments. The water treatment
system includes an electrochemical water treatment device 200.
Electrochemical water treatment device 200 may have a series of
alternating cation and anion exchange membranes positioned between
a cathode and anode. The treatment system may further include a
concentrate stream 210 and dilution stream 230 that are in fluid
communication with at least one ion exchange membrane in the
electrochemical water treatment device 200. The concentrate and
dilution streams may also be in fluid communication with a manifold
(not shown), which functions to collect liquid exiting from one or
more compartments of the electrochemical water treatment device
200. For example, a storage tank 240 may be in fluid communication
with the dilution stream 230 and function to store treated water
260 for further use. Concentrate stream 210 and dilution stream 230
may also be in fluid communication with a pump 250 that functions
to circulate the respective streams throughout the water treatment
system 20. Water treatment system 20 may further include a reject
or waste stream 220 and a reject make-up stream 270 that are in
fluid communication with the concentrate stream 210.
[0072] FIG. 3 is another process flow diagram of a treatment system
30 according to one or more embodiments. A liquid circuit is
illustrated where a feed stream 304 is introduced to treatment
system 30. The feed stream 304 may provide or be in fluid
communication with a water source. Non-limiting examples of the
water source include potable water sources, for example, municipal
water, well water, non-potable water sources, for example, brackish
or salt-water (seawater), pre-treated semi-pure water, and any
combination thereof. In some instances, a treatment system, for
example, a purification system, and/or a chlorine removal system,
treats the water before it comprises the feed stream. The feed
stream may contain dissolved salts or ionic or ionizable species
including sodium, chloride, chlorine, calcium ions, magnesium ions,
carbonates, sulfates or other insoluble or semi-soluble species or
dissolved gases, such as silica and carbon dioxide. The feed stream
may also contain additives, such as fluoride, chlorate, and bromate
species. In the alternative, these species may be added to treated
water after one or more processing steps.
[0073] In accordance with one or more embodiments, treatment system
30 includes a fluid distribution system. The distribution system
comprises components that are fluidly connected to provide fluid
communication between components of the treatment system, for
example, providing fluid communication between treated water from
storage system 380, to product stream 360. The distribution system
can comprise any arrangement of pipes, valves, tees, pumps,
manifolds, and any combination thereof, to provide fluid
communication throughout treatment system 30 and throughout one or
more product streams or storage systems available to a user. In
certain embodiments, the distribution system further comprises a
household or residential water distribution system including, but
not limited to, connections to one or more points of use such as, a
sink faucet, a showerhead, a washing machine, and a dishwasher. For
example, treatment system 30 may be connected to the cold, hot, or
both, water distribution systems of a household. Pumps and vacuum
sources may be in fluid communication with various components of
the fluid distribution system for purposes of controlling liquid
flow by pressurizing the liquid. The pressurized liquid stream may
further comprise a regulator where the pressure can be more readily
controlled. Fluid may also be caused to flow by gravity.
[0074] The liquid circuit may further comprise one or more bypass
valves 312 which may allow liquid to flow through one part of water
treatment system 30 and prevent flow through another part of the
system. For example bypass valve 312 may function to allow fluid
from feed stream 304 to bypass water treatment system 30 and exit
with product stream 360, or conversely allow feed stream 304 to
flow into the water treatment system through valve 302, flowmeter
316, and pre-filter 305.
[0075] Pre-filter device 305 may be a preliminary filter or
pre-treatment device designed to remove a portion of any
undesirable species from the water before the water is further
introduced into one or more components of treatment system 30.
Non-limiting examples of pre-filter devices include, for example,
carbon or charcoal filters that may be used to remove at least a
portion of any chlorine, including active chlorine, or any species
that may foul or interfere with the operation of any of the
components of the treatment system process flow. Additional
examples of pre-treatment devices include, but are not limited to,
ionic exchange devices, mechanical filters, and reverse osmosis
devices. Pre-treatment systems can be positioned anywhere within
treatment system 30. For example, water that enters storage system
380 after being treated by electrochemical water treatment device
300 may contain little or no chlorine (or any other alternative
disinfectant). To retain a residual chlorine level in storage
system 380, the water can be mixed with untreated water from feed
stream 304. Preferably, the chlorinated water is added at a rate
adequate to result in mixed water that contains enough chlorine to
inhibit bacteriologic activity. Active chlorine refers to chlorine
containing species that exhibit anti-microbial activity. An
effective chlorine concentration is defined herein as a
concentration of active chlorine compounds, for example, sodium
hypochlorite that inhibits the growth of bacteria, such as e. coli,
in storage system 380. Therefore, the ratio at which the feed water
and treated water are mixed in storage system 380 may be dependent
upon a number of factors, including the efficiency of
electrochemical water treatment device 300, the desired effective
chlorine concentration, the rate at which water contained in
storage system 380 is depleted, the temperature of storage system
380, and the source and quality of the feed water. Pre-treatment
devices may also be, for example, a particulate filter, aeration
device, or a chlorine-reducing filter, and may comprise several
devices, or a number of devices arranged in parallel or in a
series. Pre-treatment device 305 can be positioned upstream or
downstream of the storage system 380, or positioned upstream of
electrochemical water treatment device 300 so that at least some
chlorine species are retained in the storage system 380 but are
removed before water enters the electrochemical water treatment
device 300.
[0076] According to some embodiments, pre-treatment devices may be
configured to add one or more sources of desirable minerals or
other substances to the treated water. For example, bicarbonates
and/or fluoride may be added to the treated water after being
processed by an electrochemical water treatment device.
[0077] In accordance with certain embodiment of the systems and
methods described herein, treatment system 30 may also comprise one
or more probes or sensors 306, for example, a water property
sensor, capable of measuring at least one physical property in
treatment system 30. For example, the sensor 306 can be a device
that measures water conductivity, pH, temperature, pressure,
composition, and/or flow rates. The probe or sensor can be
installed or positioned within treatment system 30 to measure a
particularly preferred water property. For example, a probe or
sensor 306 can be a water conductivity sensor installed in or
otherwise placed in fluid communication with storage system 380 so
that it measures the conductivity of the water. This may provide an
indication of the quality of water available for product stream
360. In another embodiment, the probe or sensor can comprise a
series or a set of sensors in various configurations or
arrangements in treatment system 30. The set of sensors can be
constructed, arranged, and connected to a controller so that the
controller can monitor, intermittently or continuously, the quality
of water in, for example, storage system 380. This arrangement
allows the performance of treatment system 30 to be further
optimized.
[0078] In accordance with other embodiments of the systems and
methods described herein, treatment system 30 may include a
combination of sets of sensors in various locations in the liquid
streams or other components throughout treatment system 30. For
example, the probe or sensor can be a flow sensor measuring a flow
rate from feed stream 304, and can further include any one or more
of a pH meter, a nephelometer, a composition analyzer, a
temperature sensor, and a pressure sensor monitoring the operating
conditions of treatment system 30.
[0079] Storage system 380 may store or accumulate water from feed
stream 304 and may also serve to store treated water for product
stream 360 and may further provide water to electrochemical water
treatment device 300. In accordance with some embodiments of the
systems and methods described herein, storage system 380 comprises
a tank, vessel or reservoir that has inlets and outlets for fluid
flow. In certain non-limiting embodiments, the storage system
comprises a tank that has a volume capacity in a range of from
about 5 gallons to about 200 gallons. In certain non-limiting
embodiments, storage system 380 may comprise several tanks or
vessels, and each tank or vessel, in turn, may have several inlets
and/or outlets positioned at various locations. The inlets and
outlets may be positioned on each vessel at various locations
depending on, among other things, the demand and flow rate to
product stream 360, the capacity or efficiency of electrochemical
water treatment device 300, and the capacity or hold-up of storage
system 380.
[0080] Storage system 380 may further comprise various components
or elements that perform desirable functions or avoid undesirable
consequences. For example, the tanks or vessels may have internal
components, such as baffles, that are positioned to disrupt any
internal flow currents or areas of stagnation. In some embodiments,
storage system 380 further comprises a heat exchanger for heating
or cooling the stored fluid. For example, storage system 380 may
comprise a vessel constructed with a heating coil, which can have a
heating fluid at an elevated temperature relative to the
temperature of the fluid in the vessel. The heating fluid can be
hot water in a closed-loop flow with a furnace or other
heat-generating unit so that the heating fluid temperature is
raised in the furnace. The heating fluid, in turn, raises the
vessel fluid temperature by heat transfer. Other examples of
auxiliary or additional components include, but are not limited to,
pressure relief valves designed to relieve internal pressure in the
storage system. In accordance with further embodiments, the
treatment system can comprise at least two tanks or vessels or two
zones in one or more tanks or vessels, each of which can be, at
least partially, fluidly isolated from the other. For example, the
treatment system can comprise two vessels fluidly connected to a
feed stream and to one or more treatment devices. The two tanks or
vessels can be fluidly isolated from each other by conduits and
valves so that the first can be placed in service with one or more
treatment devices while the second can be removed from service for,
for example, maintenance or cleaning. In accordance with one or
more embodiments of the systems and methods described herein, the
tank or reservoir system is connected to, or in thermal
communication with, a heat exchanger and, optionally, to a fluid
treatment device. The fluid treatment device can be an
electrochemical water treatment device, a reverse osmosis device,
an ion-exchange resin bed, an electrodialysis device, a capacitive
deionization device, or combinations thereof.
[0081] In certain embodiments, liquid exiting electrochemical water
treatment device 300 as dilution stream 330 may be directed by
valve 312 to storage system 380. In addition, storage system 380
may store or accumulate water from feed stream 304. Thus, storage
system 380 may include treated water as well as untreated, or
minimally treated, water. Storage system 380 may be configured so
that these two sources of water are mixed together, or
alternatively, the two water sources may be segregated. For
example, one source of water may enter the bottom of storage system
380 through one or more inlets and proceed in plug-flow manner in
an upward direction to one or more outlets positioned at the top of
storage system 380.
[0082] In various embodiments, a dilution stream 330 may flow in a
circulating loop through electrochemical water treatment device
300. The circulating dilution stream may provide fluid
communication between one or more depletion compartments in
electrochemical water treatment system 300 and storage system 380.
Likewise, a concentrate stream 310 may flow in a circulating loop
through electrochemical water treatment device 300 and may be in
fluid communication between one or more concentration compartments
in electrochemical water treatment device.
[0083] Water treatment system 30 may further include one or more
gate valves 302 and flow meters 308. For example, the fluid path
flowing from storage system 380 to product stream 360 may include
gate valve 302, flow meter 308, and one or more sensors 306, for
example, an ionic conductivity probe. In one or more embodiments,
concentrate stream 310 may include water from concentrate make-up
stream 314 that is fed from feed stream 304 and passes through
pre-filter 305. A valve (not shown) may be positioned at the
junction of the concentrate make-up stream 314 and concentrate
stream 310.
[0084] In certain non-limiting embodiments, the valve 312 may be a
solenoid valve. The solenoid valve may be a one-way or multi-way
valve, including three-way and four-way valves. The solenoid valve
may be an on/off type of valve, a proportional type of valve, and
any combination thereof. For example, a four-way solenoid valve 312
may include a first port that is in fluid communication a
concentrate compartment of electrochemical water treatment device.
A second port may be in fluid communication with a dilution
compartment of electrochemical water treatment device 300. A second
four-way solenoid valve 312 may be positioned downstream of one or
more outlets of electrochemical water treatment device 300. For
example, a first and second port of valve 312 may be in fluid
communication with an outlet of a concentrate and dilution chamber
of electrochemical water treatment device 300, and feed the
concentrate stream and dilution stream respectively.
[0085] In one or more embodiments, a control system may be in
communication with a multi-way valve. For example, a three-way
solenoid valve may allow either one of two incoming fluids to be
directed to an outlet. When the valve is in the "off" position,
fluid flow from one of the incoming fluid streams may be
interrupted. When the valve is in the "on" position fluid flow from
the other incoming fluid stream may be interrupted. For example,
valve 312 may be used to direct fluid flow from concentrate stream
310 and storage system 380 to electrochemical treatment device 300.
The exact selection of which or both of these streams may be used
may be controlled by one or more components of the control
system.
[0086] Treatment system 30 may further comprise a liquid circuit
that allows fluid communication between one or more outlets of
electrochemical water treatment device 300, and storage system 380.
For example, a third port of valve 312 may be in fluid
communication with at least one outlet of electrochemical water
treatment device 300. In certain embodiments, the outlet of the
electrochemical water treatment device comprises ion-depleted water
from one or more depletion compartments of electrochemical water
treatment device 300. A fourth port of valve 312 may be in fluid
communication with a sensor 306, for example, an ionic conductivity
probe. The liquid circuit may also be in fluid communication with
at least one inlet to storage system 380. An outlet of storage
system 380 may be in fluid communication with at least one inlet to
electrochemical water treatment device 300. The liquid circuit may
include one or more pumps 350 to aid in directing fluid throughout
the treatment system 30, for example, for directing fluid into one
or more inlets of electrochemical water treatment device 300.
[0087] The systems and methods described herein further provide a
treatment system where a controller may provide a signal that
actuates a valve so that fluid flow is adjusted based on a variety
of operating parameters. These parameters may include, but are not
limited to, the properties of water from feed stream 304, the
properties of water in storage system 380, the properties of water
in dilution stream 330, the properties of water in concentrate
stream 310, and any combination thereof. Other parameters may
include the properties of water exiting storage system 380, the
demand of water necessary to provide to product stream 360, the
operating efficiency or capacity of electrochemical water treatment
device 300, the operating parameters associated with
electrochemical water treatment device 300, and any combination
thereof. Specific measured parameters may include, but are not
limited to, water conductivity, pH, turbidity, composition,
temperature, pressure, flow rate, and any combination thereof.
[0088] In one or more embodiments, a controller may receive signals
from one or more sensors so that the controller is capable of
monitoring the operating parameters of treatment system 30. For
example, a conductivity sensor may be positioned within storage
system 380 so that the conductivity is monitored by the controller.
In one or more embodiments, a controller may receive a signal from
one or more sensors so that the controller is capable of monitoring
the operating parameters of the dilution stream, such as
conductivity. In operation, the controller may increase, decrease,
or otherwise adjust the voltage, current, or both, supplied from a
power source to one or more components of the treatment system. The
controller may include algorithms that may modify an operating
parameter of treatment system 30 based on one or more measured
properties of the liquid flowing in the system. For example, in
some embodiments, the controller may increase or decreases the flow
rate of the concentrate stream 310 and the dilution stream 330.
[0089] The controller may be configured, or configurable by
programming, or may be self-adjusting such that it is capable of
maximizing any of the service life, the efficiency, or reducing the
operating cost of treatment system 30. For example, the controller
may include a microprocessor having user-selectable set points or
self-adjusting set points that adjust the applied voltage, current,
or both, to valve(s) 312, the flow rate through concentrate stream
310, and the flow rate out to discharge stream 320.
[0090] In accordance with another embodiment of the systems and
methods described herein, the controller regulates the operation of
the treatment system by incorporating adaptive or predictive
algorithms, which are capable of monitoring demand and water
quality and adjusting the operation of any one or more components
of the treatment system 30. For example, in a residential
application, the controller may be predictive in anticipating
higher demand for treated water during early morning hours to
supply product stream 360 that services a showerhead.
[0091] In certain non-limiting embodiments, radio frequency
identification (RFID) is utilized to provide real-time detection of
certain properties or conditions in treatment system 30. In certain
embodiments, a plurality of inline identifying tag readers or
optical sensors are configured to track or sense certain properties
or conditions of the liquid as it is transported through the
treatment system. The RFID may be combined with one or more
additional sensors, for example, a flowmeter. For example, an
embedded tag may be placed in the cartridge of pre-filter device
305 and used in combination with a flowmeter to determine various
properties or conditions, for example, the usable volume remaining
in the cartridge, and the number of days remaining before the
cartridge is exhausted and needs to be replaced.
[0092] In certain non-limiting embodiments, valves 312 can be
actuated to provide liquid to be treated from storage system 380 to
electrochemical water treatment device 300 and transfer the treated
liquid to storage system 380. In some arrangements, the liquid
circuit may include connections so that untreated liquid may be
mixed with liquid that would exit any of the electrode compartments
of electrochemical water treatment device 300. In several
embodiments, the liquid circuit may further include connections to
and from storage system 380 so that, for example, treated liquid
exiting the depleting compartment of electrochemical water
treatment device 300 may be transferred to storage system 380 and
mixed with untreated liquid from feed stream 304. The resulting
mixture may be delivered to product stream 360, and, optionally, to
the one or more ion exchange membranes of the electrochemical water
treatment device 300 in parallel or series flow paths.
[0093] In accordance with another embodiment of the systems and
methods described herein, a controller, through a sensor or set of
sensors, may monitor or measure at least one water property of the
water storage system 380 and also measure a flow rate flowing in
product stream 360. The controller may adjust an operating
parameter of electrochemical water treatment device 300 and/or
valve 312 based on the measured properties. In one or more
embodiments of the systems and methods described herein, one or
more sensors may measure at least one property of feed stream 304
and water in storage system 380.
[0094] In certain embodiments, storage system 380 may be connected
downstream of feed stream 304 and may be in fluid communication
with electrochemical water treatment device 300. For example, water
from feed stream 304 may flow in and mix with the bulk water
contained within storage system 380. Bulk water may exit storage
system 380 and be directed to product stream 360 or exit through
and be directed through valve 312 into electrochemical water
treatment device 300 for treatment. In certain embodiments, treated
water leaving electrochemical water treatment device 300 may mix
with water from feed stream 304 by entering storage system 380. In
this way, a liquid circuit may be formed between storage system
380, electrochemical water treatment device 300 and feed stream
304, and may function as a method for replenishing the water
leaving the system 30 via product stream 360.
[0095] In accordance with further embodiments of the systems and
methods described herein, one or more disinfecting and/or cleaning
apparatus components may be utilized with the treatment system.
Such disinfecting or cleaning systems can comprise any apparatus
that destroys or renders inactive, at least partially, any
microorganisms, such as bacteria, that can accumulate in any
component of the treatment system. Examples of cleaning or
disinfecting systems include those that can introduce a
disinfectant or disinfecting chemical compounds, such as halogens,
halogen-donors, acids or bases, as well as systems that expose
wetted components of the treatment system to hot water temperatures
capable of sanitization. In accordance with still further
embodiments of the systems and methods described herein, the
treatment system may include final stage or post treatment systems
or subsystems that provide final purification of the fluid prior to
delivery at a point of use. Examples of such post treatment systems
include, but are not limited to those that expose the fluid to
actinic radiation or ultraviolet radiation, and/or ozone or remove
undesirable compounds by microfiltration or ultrafiltration. Thus,
the treatment system may be utilized for household service and
installed, for example, under a sink and provide treated water that
is further treated by exposure to ultraviolet radiation before
being delivered to a point of use, such as a faucet.
[0096] In accordance with further embodiments, the treatment system
may comprise systems and techniques that permit disinfection of any
component of the treatment system. For example, the treatment
system may be exposed to a disinfecting solution or a disinfectant.
The disinfectant may be any material that can destroy or at least
render inactive at least a portion of any viable microorganisms,
such as bacteria, present in any component or subsystem of the
treatment system. Examples of disinfectants may include bases,
acids, or sanitizers, such as a halogen or halogen-donating
compounds and peroxygen or peroxygen-donating compounds that
destroy or render bacteria inactive. The disinfectant may be
introduced into the treatment system by any suitable device or
technique. For example, chlorine may be introduced into the storage
system. Chlorine may be introduced by injection of a hypochlorate
species from a disinfectant reservoir fluidly connectable to any
suitable portion of the treatment system. The chlorinated water can
be further circulated through at least a portion of the treatment
system thereby exposing wetted portions of the system to the
disinfectant.
[0097] In accordance with another embodiment, discharge water
comprising, for example, water exiting the system via waste or
reject stream 320 may be used for auxiliary purposes to serve or
provide additional or secondary benefits. For example, discharge
water may be used to provide, for example, irrigating water to
residential and commercial, and industrial uses. Discharge water
may also be used for recovery of collected or concentrated
salts.
[0098] In one or more embodiments, the treatment system may include
a mixing system that is fluidly connected to at least one of a
fluid distribution system and a storage system. The mixing or
blending system may include one or more connections in the fluid
distribution system as well as connections to a feed stream. The
mixing system may provide fluid mixing of, for example, untreated
water with treated water to produce service water that may be fed
to one or more product streams. For example, the mixing system may
comprise at least one tee, a mixing tank, or both, that fluidly
connects an outlet of the storage system and the feed stream. The
mixing system, in some cases, may include a valve that regulates
the flow of any of the untreated water streams, treated water
streams, and any other stream flowing to the product streams. In
another embodiment, the valve may be a proportional valve that
mixes the treated water with untreated water according to a
predetermined ratio. In another embodiment, the valve may be
actuated by a controller based on, for example, the flow rate, the
water property, and the particular service associated with the
product stream. For example, if low hardness water is required for
the product stream, then the controller may regulate the amount of
untreated water, if any, that can be mixed with treated water by
actuating a valve. This may be accomplished by using closed-loop
control with a sensor measuring the conductivity of the mixed water
stream. In another embodiment, the valve may regulate the flow rate
of the treated water that is mixed with the untreated water
according to certain requirements of the product stream. In other
embodiments, the treatment device may be operated to reach a
set-point that is lower than any required by one or more product
streams so that any mixing of treated water with untreated water
can produce service water that satisfies the particular
requirements of each product stream.
[0099] Those of ordinary skill should recognize that the treatment
system can be adjustable to accommodate fluctuations in demand as
well as variations in water quality requirements. For example, the
systems and methods described herein may produce low LSI water that
is available to the treatment system as a whole, during extended
idle periods. The low LSI water, in some embodiments, may be used
to flush the wetted components of the treatment system, which may
reduce the likelihood of scaling and increase the service life not
only the individual components, but also the treatment system as a
whole. In accordance with some embodiments, the systems and methods
described herein provide for producing treated liquids, such as
water, having a low conductivity. The treatment system may comprise
a fluid circuit that provides treated or, in some cases, softened
water or, in other cases, low conductivity water, and/or low LSI
water, to one or more product streams and subsequently, one or more
points of use.
[0100] In another embodiment of the systems and methods described
herein, treatment system 30 may comprise one or more flow
regulators for regulating liquid flow. For example, a flow
regulator may regulate the volume of fluid discharged from the
system via a waste stream. According to another embodiment of the
systems and methods described herein, the flow regulator may be a
valve that may be intermittently opened and closed according to a
predetermined schedule for a predetermined period of time to allow
a predetermined volume of water to flow. The volume of flowing
fluid may be adjusted by, for example, changing the frequency
and/or duration that the flow regulator is opened and closed. In
some embodiments, the flow regulator may be controlled or regulated
by a controller, through, for example, an actuation signal. The
controller may provide an actuation signal, such as a radio,
current or a pneumatic signal, to an actuator, with a motor or
diaphragm that opens and closes the flow regulator. The fluid
regulated by a valve or flow regulator may be any fluid located in
the water treatment system.
EXAMPLES
[0101] The function and advantages of these and other embodiments
will be more fully understood from the following examples. The
examples are intended to be illustrative in nature and are not to
be considered as limiting the scope of the embodiments discussed
herein.
Example 1
Comparison Study
[0102] An electrochemical treatment system in accordance with one
or more embodiments of the systems and methods described herein and
shown schematically in FIG. 2 was evaluated for performance against
a control treatment system. A comparison study was conducted to
evaluate the performance characteristics for both systems in
cleaning a 28 gallon volume of feed water from 20 gpg to 4 gpg. The
feed streams for both systems were identical in composition. Water
was treated by an electrochemical device under the conditions
outlined in Table 1 below.
TABLE-US-00001 TABLE 1 Electrochemical Treatment System Conditions;
High Efficiency Electrodeionization (HEED) Module: 15 cell pairs;
0.065'' cell thickness filled with open weave supporting screens
Compartment size: 7'' .times. 7'' cross section Flow Rate of all
streams 1.5 gpm Applied Voltage 2 Volts/cell pair No cycle
switching/No requirement for additional source of acidic water
[0103] In addition, water was treated by a control device (a CEDI
device) under the conditions outlined in Table 2 below.
TABLE-US-00002 TABLE 2 Control Treatment System Conditions (CEDI
device) Module: 30 cell pairs; 0.065'' cell thickness with mixed
bed ion exchange resin Compartment size: 7'' .times. 7'' cross
section Flow Rate of all streams 2.0 gpm Applied Voltage 2
Volts/cell pair Requires cycle switching/Requires additional source
of acidic water to lower pH of concentrate stream
[0104] The results of the comparison study are shown in Table 3 and
indicate that the 15 cell pair electrochemical test device was able
to reduce hardness as quickly as a 30 cell pair CEDI module under
conditions of equivalent flow rate and volts/cell pair.
TABLE-US-00003 TABLE 3 Comparison Study Results Water
Electrochemical Property Feed CEDI (control) test device Total 325
ppm/20 gpg 70 ppm/4 gpg 70 ppm/4 gpg Hardness Calcium 210 ppm 41
ppm 41 ppm Conductivity 1050 .mu.S/cm 180 .mu.S/cm 300 .mu.S/cm
Alkalinity 220 ppm Dilution: 40 ppm Dilution: 100 ppm pH 7.3
Dilution: 6.9 Dilution: 7.8 Concentrate: 7.4 Concentrate: 7.1 LSI 0
Concentrate: 1.2 Concentrate: 0.2
[0105] The electrochemical test device yields a product with a
conductivity of 300 .mu.S/cm, and indicates that the conductivity
does not need to be reduced as far as required in the control CEDI
device to achieve the same reduction in hardness. The cleaning rate
is thus significantly improved and a comparison between the
processing times required by both systems is illustrated
graphically in FIG. 4. As shown, the electrochemical test device
requires at least 25% less time to reduce the hardness of the feed
stream than the CEDI control device. The reduced process time may
allow other advantages, including a reduction in the size of the
module, a reduction in the module duty cycle, and an increase in
the production rate. Furthermore, the electrochemical test device
does not use or require cycle switching, as did the CEDI control
device. A direct comparison between properties of the feed and the
product water produced by the electrochemical test device is shown
below in Table 4.
TABLE-US-00004 TABLE 4 Water Properties of Feed and Product Streams
20 gpg Feed 4 gpg Product mg/L as mg/L as Water Property gpg
CaCO.sub.3 gpg CaCO.sub.3 TH (gpg as CaCO.sub.3) 19.3 337 4 70 MgH
(gpg as CaCO.sub.3) 8.1 139 1.7 29 CaH (gpg as CaCO.sub.3) 11.6 219
2.4 41 HCO/Alkalinity 220 5.8 100 (mg/L as CaCO.sub.3) Sulfate 73
Chloride 106 Na+ 213 TDS (ppm) 550 pH 7.3 7.8 Conductivity
(.mu.S/cm) 1023 .mu.S/cm 300 .mu.S/cm
[0106] The results from an LSI analysis of the electrochemical test
device are shown below in Table 5. The LSI for the concentrate
stream of the test device is significantly lower than that for the
CEDI control device. This is shown in the table below, with the
test device consistently producing LSI values at about 0.2 or
less.
TABLE-US-00005 TABLE 5 LSI Analysis of Electrochemical Test Device
Product Concentrate Time(s) Conductivity Hardness pH Conductivity
pH Ca HCO.sub.3 Temp.(C) LSI 0 1050 19 7.25 1050 18.0 0 700 879 15
7.30 2888 6.91 620 480 19 0.11 1400 680 12 7.39 2456 6.96 530 440
19.4 0.12 2100 521 9 7.59 2190 7.05 475 440 20 0.2 2800 392 6 7.86
2058 7.11 450 400 20.2 0.2 3500 300 4 7.9
[0107] The ionic conductivity probe used for the study was a Myron
L Company.TM. Ultrameter II. The pH was measured by a pH meter
available from Oakton.TM.. The alkalinity, calcium content, and
total hardness were all measured using titration instruments
available from Hach.TM. including model types AL-AP, EDTA, and HA
71A respectively.
Example 2
Desalination Study 1
[0108] In an effort to determine the effectiveness of the ion
exchange membranes used in Example 1, an electrochemical treatment
system was evaluated using seawater as a source of feed water.
Seawater, having an average conductivity of about 40,000 .mu.S/cm
was fed into the concentrate and dilution streams and was treated
by an electrochemical device under the conditions outlined in Table
6 below. This arrangement effectively functioned as a desalination
process. The dilution and concentrate streams were continuously
recirculated, with flow rates at about 500 ml/min. The cation
exchange membrane (CEM) and anion exchange membranes (AEM) used in
the electrochemical device were obtained from Evoqua Water
Technologies (Lowell, Mass.). The anion exchange membrane had an
ion permselectivity of about 89%. The inter-membrane spacing was
between 0.4 and 0.5 mm, although smaller distances are within the
scope of this disclosure.
TABLE-US-00006 TABLE 6 Desalination Study 1 - Electrochemical
Treatment System Conditions Module 10 cell pairs; SWT G2 CEM/AEM;
10 Volts Dilution stream inlet seawater; inlet 42.05 mS/cm; 16.5
psi Dilution stream outlet 500 ml/min; 0 psi; 1 liter,
recirculating Concentrate stream inlet seawater; inlet 42.05 mS/cm;
16 psi Concentrate stream outlet 485 ml/min; 0 psi; 2 liters,
recirculating
[0109] The pH and conductivity of the dilution and the concentrate
streams exiting the compartments of the electrochemical were
measured at several points in time, and the results are shown below
in Table 7. The electrochemical test device was capable of reducing
the conductivity of the seawater to a value of about 300 .mu.S/cm.
The pH of the concentrate stream was reduced from a value of 7.65
to a value of 6.28. This signifies that the pH of the concentrate
stream can be reduced to be slightly acidic. This is in contrast to
other electrochemical systems, where the concentrate stream may be
basic, and thus more susceptible to creating a precipitate.
Further, the ratio of the pH of the concentrate stream to the pH of
the dilution stream was maintained at a value of about 1.0. In this
example, the acidity of the concentrate stream means that an
additional source of acid does not need to be added to the
concentrate stream, which decreases processing costs.
TABLE-US-00007 TABLE 7 Desalination Study 1 Results Dilution Stream
Ratio: pH Time Conductivity Concentrate Stream concentrate/ (min)
(.mu.S/cm) pH pH pH dilute 0 42.05 8.17 7.65 0.94 100 5.64 6.72
7.42 1.10 125 2.45 6.39 6.83 1.07 225 0.5 5.83 6.33 1.09 230 0.32
5.79 6.28 1.08
Example 3
Desalination Study 2
[0110] To affirm the findings of Experiment 2, a second experiment
was conducted using an electrochemical treatment system similar to
that described in Experiment 2. Seawater was again used as the
source of feed, with specific process conditions outlined in Table
8 below.
TABLE-US-00008 TABLE 8 Desalination Study 2 - Electrochemical
Treatment System Conditions Module 10 cell pairs; SWT G2 CEM/AEM;
10 Volts Dilute stream inlet seawater; inlet 41.8 mS/cm; 6.5 psi
Dilute stream outlet 436 ml/min; 0 psi; 1 liter, recirculating
Concentrate stream inlet seawater; inlet 41.8 mS/cm; 16 psi
Concentrate stream outlet 400 ml/min; 0 psi; 2 liters,
recirculating
[0111] The results from the pH and conductivity measurement data
are shown below in Table 9. The conductivity of the feed stream was
reduced to a value of about 400 .mu.S/cm. The pH of the concentrate
stream was reduced to a value of 5.65, which is even more acidic
than the result obtained in Experiment 2. Again, the ratio of the
pH of the concentrate stream to the dilution stream yielded a value
of about 1.0.
TABLE-US-00009 TABLE 9 Desalination Study 2 Results Dilution Stream
Ratio: pH Time Conductivity Concentrate Stream concentrate/ (min)
(.mu.S/cm) pH pH pH dilute 1 40.98 8.44 7.37 0.87 160 4.3 6.49 7.09
1.09 175 2.34 6.41 6.73 1.05 220 0.4 5.65 5.65 1.00
[0112] It is to be appreciated that embodiments of the methods and
apparatuses discussed herein are not limited in application to the
details of construction and the arrangement of components set forth
in the following description or illustrated in the accompanying
drawings. The methods and apparatuses are capable of implementation
in other embodiments and of being practiced or of being carried out
in various ways. Examples of specific implementations are provided
herein for illustrative purposes only and are not intended to be
limiting. In particular, acts, elements and features discussed in
connection with any one or more embodiments are not intended to be
excluded from a similar role in any other embodiment.
[0113] Also, the phraseology and terminology used herein is for the
purpose of description and should not be regarded as limiting. Any
references to embodiments or elements or acts of the systems and
methods herein referred to in the singular may also embrace
embodiments including a plurality of these elements, and any
references in plural to any embodiment or element or act herein may
also embrace embodiments including only a single element. The use
herein of "including," "comprising," "having," "containing,"
"involving," and variations thereof is meant to encompass the items
listed thereafter and equivalents thereof as well as additional
items. References to "or" may be construed as inclusive so that any
terms described using "or" may indicate any of a single, more than
one, and all of the described terms. Any references to front and
back, left and right, top and bottom, upper and lower, and vertical
and horizontal are intended for convenience of description, not to
limit the present systems and methods or their components to any
one positional or spatial orientation.
[0114] Having described above several aspects of at least one
embodiment, it is to be appreciated various alterations,
modifications, and improvements will readily occur to those skilled
in the art. Such alterations, modifications, and improvements are
intended to be part of this disclosure and are intended to be
within the scope of the systems and methods disclosed herein.
Accordingly, the foregoing description and drawings are by way of
example only.
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