Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND SYSTEM FOR IRRIGATION
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority under 35 U.S.C. 119(e) to U.S. Provisional
Application Serial No. 60/805,512, entitled "ELECTRODIALYSIS FOR
DESALINATION OF SEAWATER AND BRACKISH WATER FOR
AGRICULTURAL USE" filed on June 22, 2006, and to U.S. Provisional Application
Serial No. 60/804,610, entitled "ELECTRODIALYSIS AND FILTRATION FOR
AGRICULTURAL WATER PRODUCTION," filed on June 13, 2006, both of which
incorporated herein by reference in their entirety.
. .t;:. -
BACKGROUND OF 1NVENTION
1. Field of the Invention
This invention relates to systems and methods of providing crop irrigation
water as well as potable water and, more particularly, to systems and methods
of
providing irrigation water and/or potable water from water having unacceptable
dissolved solids content.
2. Discussion of Related Art
Desalting or desalination refers to a water treatment process that removes
salt
from, for example, water. In some cases, the water source is brackish or
seawater and
desalting techniques thereof provides at least a portion of municipal
requirements for
potable, drinking water. Desalination techniques typically include those based
on
distillation as well as reverse osmosis techniques. The desalted water can
also be
consumed in commercial and industrial applications as, for example, process
feed
water, boiler feed water, and irrigation water. Particular examples of
industries that
may utilize desalted water include the pharmaceutical, mining, paper and pulp,
and
agricultural industries.
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SUMMARY OF THE INVENTION
Some aspects of the invention provide one or more embodiments involving a
method comprising introducing water to be treated into an electrically-driven
separation apparatus to provide irrigation water having a sodium adsorption
ratio
(SAR or RNa) value of less than about 20. The SAR value can be determined
according to the formula,
SAR = [Na]
jCa + Mg '
where [Na] is the sodium species concentration, in mol/rn3, in the irrigation
water,
[Ca] is the calcium species concentration, in mol/m3, in the irrigation water,
and [Mg]
is the magnesium species.,concentration, in mol/m3, in the irrigation water.
Other aspects of the invention provide one or more embodiments involving an
irrigation system comprising an electrically-driven separation apparatus
fluidly
connected to a source of water to be treated and an irrigation water
distribution system
fluidly connected to the electrically-driven separation apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings are not intended to be drawn to scale. In the
drawings, each identical or nearly identical component that is illustrated in
various
figures is represented by a like numeral. For purposes of clarity, not every
component
may be labeled in every drawing.
In the drawings:
FIG. 1 is a schematic illustration of a system in accordance with one or more
features of the invention;
FIG. 2 is a schematic illustration of an irrigation system in accordance with
further features of the invention;
FIG. 3 is another schematic illustration showing yet another system in
accordance with still further features of the invention;
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FIG. 4 is a graph showing representative ranges of acceptable levels of water
characteristics in accordance with some aspects of the invention;
FIG. 5 is a graph showing the predicted sodium adsorption ratio of desalted
water by electrodialysis relative to the total dissolved solids level
utilizing
monovalent selective cation membrane at various levels of selectivity, in
accordance
with some features of the invention;
FIG. 6 is a graph showing staged treatment aspects of the invention to produce
treated water having one or more desirable characteristics;
FIG. 7 is a graph showing the influence of membrane selectivity on the total
dissolved solids content of the product water treated in an apparatus in
accordance
with some embodiments f the invention; and
FIGS. 8A and 8B are graphs comparatively illustrating some of the
characteristics of treated water produced by systEms and techniques of the
invention
relative to other non-selective processes.
DETAILED DESCRIPTION
This invention is not limited in its application to the details of
construction and
the arrangement of components set forth in the following description or
illustrated in
the drawings. The invention is capable of embodiments and of being practiced
or of
being carried out in various ways beyond those exemplarily presented herein.
One or more aspects of the invention can involve systems and techniques for
providing water suitable for agricultural facilities. Other aspects of the
invention can
provide water potable water or water suitable for human use or consumption as
well
as for livestock and poultry. Some systems and techniques of the invention can
convert or otherwise render non-potable water suitable for agricultural,
livestock,
poultry, and/or human consumption. Still further aspects of the invention can
involve
systems and techniques that preferentially or selectively remove some species
over
other species from a fluid to be treated to provide a product having one or
more
desirable characteristics. In contrast with non-selective techniques, some
selective
removal aspects of the invention can be more cost effective by avoiding or
reducing
additional post-treatment processes such as, blending. Thus, the systems and
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techniques of the invention economically provide treated water that is more
suitable
for an intended use.
In some embodiments of the invention, some types of species are retained in
the treated stream while other types of species are preferentially removed.
The
resultant product fluid can be utilized in various applications and/or
otherwise satisfy
one or more objectives. Other aspects of the invention can involve systems and
techniques that provide water having one or more properties or characteristics
taiiored
to satisfy a particular purpose. Some embodiments of the invention can thus
involve
systems and techniques that provide one or more water streams or bodies that
have
one or more attributes that have been adjusted based on one or more parameters
of the
point of use or facility in which the stream or body is utilized.
Even further aspects of the invention can involve systems and techniques that
economicall.y=provide water for agricultural, industrial, commercial, and
residential
service. Further, some particular aspects of the invention can involve
providing water
to serve a plurality of requirements or levels of purity or quality. Thus in
some
embodiments, the systems and techniques of the invention can provide one or
more
water streams or bodies in a mixed use facility. Particularly advantageous
aspects of
the invention can involve providing the plurality of water streams or bodies,
each of
which may have differing water quality levels, from a source of water having
high
solids content, to a plurality of points of use, each of which may have
differing
requirements. Such aspects of the invention can provide systems and techniques
that
treat, for example, non-potable water to render it potable and/or suitable
for,irrigation,
for livestock and/or poultry consumption, and for human consumption or use.
In some aspects of the invention, water having a high level of one or more
objectionable species dissolved therein can be treated to remove or at least
reduce the
concentration of such species to an acceptable level. The one or more
objectionable
species can be any species that render the untreated water unsuitable for a
particular
application. For example, the water may contain a high level or undesirable
concentration of monovalent cations and/or anions which adversely or
undesirably
hinders retention of water in soil or adsorption of or other species,
including, for
example, divalent or even multivalent species. If the requirement is pertinent
to crop
irrigation, the undesirable condition or characteristic can involve water that
contains
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one or more species that affects the permeability and/or infiltration
properties of the
soil beingtirrigated. For example, some aspects of the invention can involve
rendering or treating water to preferentially remove monovalent species over
non-
monovalent species.
In accordance with one or more particular aspects, the invention can involve
embodiments directed to systems and/or methods comprising providing or
introducing
water to be treated into an electrically-driven separation apparatus. Some
embodiments of the invention can involve an irrigation system comprising an
electrically-driven separation apparatus fluidly connected, or at least
connectable, to
one or more sources of water to be treated and at least one irrigation water
distribution
system.
In other aspects of the invention, some embodiments thereof can involve a
method of providing potable water. Notably,~sF?me aspects of the invention can
provide irrigation water and/or potable water without thermally-driven
separation
techniques or unit operations. For example, in some embodiments of the
invention,
the method can comprise one or more acts or steps of providing water to be
treated
and treating at least a portion of the water to be treated in an electrically-
driven
separation apparatus to produce a first treated water. The method can further
comprise one or more acts of treating a portion of the water to be treated,
typically a
separate portion, in one or more pressure-driven separation apparatus to
produce a
second treated water. In some cases, the method can further comprise a step of
mixing the first treated water and the second treated water to produce the
potable
water_ The potable water typically has a target or desired total dissolved
solids (TDS)
content.
Aspects of the invention directed to systems that provide potable water can
comprise a source of water to be treated, a pressure-driven separation
apparatus
having an inlet that is fluidly connected, or at least connectable, to the
source of water
to be treated. The pressure-driven apparatus can also have one or more
outlets,
typically at least one product outlet as a treated water outlet. The pressure-
driven
apparatus typically also has at least one reject outlet as an outlet for a
stream
containing one or more species, typically the undesirable species, removed
from the
treated water. The system for providing potable water can further comprise one
or
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more electrically-driven separation apparatus which can be fluidly connected,
or
connectable, to the source of water to be treated, to the pressure-driven
separation
apparatus, or both. For example, as described in further detail below, one or
more
electrically-driven separation apparatus can be fluidly connected to a reject
outlet of
the pressure-driven separation apparatus. In accordance with particular
embodiments
of the invention, the system for providing potable water can further comprise
one or
more mixers having one or more inlets fluidly connected, or connectable, to
the
treated water outlet of the pressure-driven apparatus and the product water
outlet of
the electrically-driven separation apparatus. The mixer can comprise any
mixing unit
operation that facilitates at least partially blending or combining one or
more products
streams including, in some cases, a stream from the source of water to be
treated to
form a final product stream having one or more desirable characteristics.
The water to be treated can comprise seawater, brackish vcFater, and/or water
containing high concentrations of dissolved solids or salts. Other sources of
water to
be treated can comprise water that would be unsuitable for use in agricultural
facilities
because of infiltration and/or toxicity considerations.
The systems and techniques of the invention can comprise, where appropriate,
pre-treatment subsystems to facilitate one or more operating principles
thereof. One
or more pre-treatment and post-treatment unit operations may be utilized in
one or
more embodiments of the invention. For example, the systems and techniques of
the
invention may comprise a pre-treatment subsystem comprising one or a plurality
of
filters that separate or remove at least a portion of any suspended solids in
the water to
be treated. Such pre-treatment subsystems typically remove particulate
material that
would damage any downstream unit operation of the systems of the invention.
Other
pre-treatment unit operations include, for example, microfilters as well as
sedimentary-based systems that can remove suspended solids that are one micron
or
greater.
Further pre-treatment operations may be utilized to improve the effectiveness
of one or more unit operations of the invention. For example, a pre-treatment
subsystem can comprise cooler or heaters that, respectively, cool or heat the
water to
be treated prior to separation operations. Cooling of the raw feed stream, or
any
intermediate process stream may be performed to, for example, facilitate the
transport
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of an undesirable species, or to hinder the transport of a desirable species,
from the
stream to be treated. Likewise, heating may be performed to raise the
temperature of
the raw feed stream, or one or more intermediate process streams, to a desired
temperature that, for example, facilitates economical or efficient operation
of the one
or more separation apparatus. Non-limiting examples of heating processes may
involve heaters, furnaces, or heat exchangers that may be associated or be a
unit
operation of a process or system of the invention. For example, heating may be
provided through a heat exchanger of a power plant that is not necessarily
associated
with the treatment systems of the invention.
Post-treatment unit operations may polish, remove, or reduce the
concentration one or more species in the treated water. For example, one or
more iori
exchange columns may be utilized to remove species that are not readily
removed in
the electrically-driven separation-apparatus and/or the-pressure-driven
separation
apparatus. Non-limiting examples of species that would typically be removed or
at
least have a reduction in concentration to, preferably, non-toxic and/or non-
objectionable levels, in post-treatment operations include those that may
affect soil
aggregation, water infiltration, and/or would be toxic to plant growth such as
aluminum, arsenic, beryllium, cadmium, cobalt, chromium, copper, iron,
fluoride,
lithium, manganese, molybdenum, nickel, lead, selenium, tin, titanium,
tungsten,
vanadium, boron, and zinc. Other species that may be addressed by one or more
post-
treatment operations include those that may be toxic or objectionable to
humans,
poultry, and/or livestock in drinking water such as, but not limited to,
nitrates, nitrites,
and vanadium, and sulfides. Disinfecting processes may also be performed to at
least
partially inactivate or reduce the concentration of colony-forming
microorganisms
that may be harmful to human and/or livestock.
Alternatively, or in combination with the one or more polishing unit
operations, the systems and techniques of the invention may involve adding one
or
more species to at least a portion of the treated water. For example, gypsum
may be
added to adjust the concentration of one or more desirable species or adjust a
characteristic of the water. Other additives may include fertilizers or other
supplements that facilitate crop growth when the water is used for irrigation.
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An electrically-driven apparatus typically utilizes a potential field to
create a
motive force that induces one or more species, typically the target
species,.which can
include desirable as well as undesirable species, to migrate from the carrier
or fluid.
The electrically-driven apparatus can utilize one or more components that
segregate
the target species during migration and/or inhibit the return or reverse
process. Non-
limiting examples of such devices include electrodialysis (ED) devices,
including
current reversing electrodialysis (EDR) devices, as well as
electrodeionization (EDI)
devices. The present invention, however, is not limited to one or a
combination of
such electrically-driven apparatus and may be practiced in other apparatus
that
provide a motive force that facilitates the preferential migration of one or
more target
species over other species in the fluid to be treated.
The electrically-driven separation apparatus of the invention typically
utilize
ion selective membranes to.=facilitate separation phenomena. In some cases,
the
selectively permeable membrane can preferentially or selectively allow
transport of
some species relative to other species. For example, cation selective
membranes may
be utilized in some compartments of the electrically-driven separation
apparatus. In
other cases, anion selective membranes may be utilized in one or more
compartments.
In still other cases, the electrically-driven separation apparatus of the
invention may
comprise one or more monovalent selective membranes to selectively promote
transfer of the monovalent cationic or anionic species. Indeed, in some
embodiments
of the invention, the separation apparatus of the invention may comprise
monovalent
cation selective membranes and one or more monovalent anion selective
membranes,
typically in one or more concentrating compartments of the apparatus. Non-
limiting
examples of commercially available monovalent selective membranes include
NEOSEPTAO cation and anion selective membranes from ASTOM Corporation,
Tokyo, Japan or Tokuyama Corporation, Tokyo, Japan.
A pressure-driven separation apparatus typically utilizes one or more barriers
to inhibit migradon therethrough while allovving penetration of another. The
motive
force facilitating the separation phenomena typically involve pressurizing the
fluid to
be treated. Non-limiting examples of pressure-driven separation apparatus
include
microfiltration, nanofiltration (NF) apparatus as well as reverse osmosis (RO)
systems.
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One or more embodiments of the invention can be directed to a water
treatment system 100 as exemplarily shown in FIG. 1. System 100 can be a
system
for providing potable water, irrigation water, or both, to, for example, a
point of use
114. The treatment system 100 can comprise at least one separation unit
operation or
separation apparatus 110 that, in some cases, selectively removes one or more
species
or types of species from the source 102 of water to be treated. The system can
optionally comprise one or more monitoring subsystems that provide an
indication of
one or more operating characteristics of the treatment system. As illustrated,
system
100 can have one or more monitoring sensors 108 that typically provide an
indication
of water quality produced, or otherwise treated, from the separation apparatus
110. In
some aspects of the present invention, system 100 can utilize a control system
or
controller configured or constructed and arranged to regulate one or more
parameters
of one or more:u.nit operations in the systems of the invention. Referring
again:to-
FIG. 1, system 100 can thus have one or more controllers 106 that adjust at
least one
operating parameter of separation apparatus 110 typically to at least one
desired
condition. Any suitable control technique may be utilized to adjust the at
least one
operating parameter of any unit operation in system 100 to provide treated
water
having the one or more desired characteristics.
The systems and techniques of the invention may include one or more water
distribution systems that facilitate delivery of the treated water to one or
more points
of use. For example, the distribution system may include an irrigation
distribution
system that delivers irrigation water to various points of use in an
agricultural facility.
To facilitate the delivery of the treated water, the distribution system can
include one
or more storage systems, such as reservoirs, tanks, wells, or other vessels
and
containers. The irrigation systems of the invention may utilize overhead
and/or
surface irrigation techniques to convey water to a designated area. The
irrigation
system components can thus employ non-movable as well as mobile devices.
The one or more storage systems that may be considered as part of the
distribution system or be an ancillary subsystem of the treatment system. The
one or
more storage systems may further facilitate providing treated water having
desired
characteristics. For example, treated water having a first condition or
characteristic
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may be stored in one or more storage companions"prior to further treatment or
processing, e.g., blending, with another treated or untreated water body or
stream.
FIG. 2 is a schematic diagram exemplarily showing some features of the
invention pertinent to an irrigation system 200. Irrigation system 200 can
comprise a
5 separation apparatus 230 fluidly connected and, as illustrated, disposed to
receive
water to be treated from source 202 through irrigation water distribution
system 224.
Separation apparatus 220 can treat water from source 202 and provide treated
water to
a first point of use 228, illustrated herein as a first type of crop. Point of
use 228 can
be a portion of a crop that, for example, is at a stage of growth different
from at least
10 one portion of the entire crop. System 200 can further comprise one or more
second
separation apparatus 230. Separation apparatus 230 can also treat water from
source
202 and provide treated water to a second point of use 238, illustrated as a
second
type of'crop, through second irrigation distribution system 234. Point df use
228,
second point of use 238 may be a portion the same type of crop to be irrigated
as, for
example, first point of use 228 or a portion of a second crop at a different
stage of
growth. In accordance with some embodiments of the invention, separation
apparatus
230 can optionally provide treated water to first point of use 228, instead of
and/or to
supplement treated water from separation apparatus 220, through conduit or
connection 244. Some embodiments of the invention contemplate, at least
partially, a
staged treatment scheme. For example, first separation apparatus 220 may
provide
treated water having a first water quality or characteristic which can further
be treated
in second separation apparatus 230 through conduit or distribution system 242.
A
plurality of second separation apparatus 230 may be utilized with one or more
first
separation apparatus 220 to provide treated water to one or more points of
use. Some
embodiments of the invention may involve serial arrangement of separation
apparatus
and other embodiments may utilize separation apparatus in parallel
configurations to
provide treated water so as to satisfy the volumetric requirements of the one
or more
points of use. In some cases, however, a combination of serial and parallel
treatment
paths may be implemented to provide treated water at a rate or a plurality of
rates,
wherein each of the one or more treated water streams have one or more desired
characteristics.
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System 200 can include one or more controllers (not shown) to control one or
more operating parameters of any component or subsystem of system 200. Like
the
system exemplarily illustrated in FIG. 1, system 200 can have one or more
controllers
that can adjust one or more operating parameters. For example, one or more
controllers of system 200 can have adjust the current, potential, or both, of
the applied
electric field in any of the separation apparatus. Other parameters that may
be
adjusted include, for example, TDS content, pressure, temperature, pH, flow
ratio or
any combination, of any stream of the system.
In accordance with some aspects of the invention, the one or more
characteristics of the treated water stream can be any measured or derived
attribute of
the product stream so as to render it suitable for its intended use at point
114.
However, the invention is not limited as such; for example, the characteristic
of the
water ma.y. -be an attribute of the treated or product water stream in
terms:telative to
the water stream to be treated. The attribute or parameter can be a singular
or a
composite or aggregate characteristic of the water. Specific, non-limiting
examples of
such attributes can include the conductivity or resistivity of the water, the
presence,
absence, or concentration of one more particular species or kinds of species
in the
water, as well as combinations thereof.
In accordance with one or more embodiments of the invention, the systems
and techniques of the invention provide water having a desired water attribute
can be
represented or quantified as a composite character. The composite character
can
provide an indication of suitability of the treated water for a particular
purpose.
Consequently, the systems and techniques of the invention can involve
operations that
seek or at least promote providing water having one or more desired composite
characteristics. In irrigation applications, the treated water attribute can
be related to
its suitability as irrigation water. Thus, some aspects of the invention can
be directed
to treating non-potable and rendering the water, as treated water, suitable
for irrigation
in one or more agricultural facilities by adjusting one or more
characteristics thereof.
Some aspects of the invention can provide irrigation water tailored one or
more crops
grown or cultivated in one or more agricultural facilities. For example, with
reference
again to FIG. 2, the systems and techniques of the invention can provide a
first treated
water, having a first composite characteristic, to a first type of crop 228
and a second
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treated water, having a second composite characteristic, to a second type of
crop 238.
The second treated water can be used to supplement and/or adjust the
characteristic of
the first treated water and, conversely, the first treated water can be used
to adjust one
or more characteristics of the second treated water. The one or more
characteristics
can be adjusted to meet a particular requirement by, for example, mixing
together or
blending the one or more treated water streams. The particular target
characteristic
can be achieved by regulating the ratios or relative amounts or rates of the
treated
water streams to be mixed.
During typical operation, each of the one or more separation apparatus 220
and 230 typically generates one or more secondary streams. Typically, the one
or
more secondary streams contain an unacceptable level of one or more
undesirable
species. Any one or more secondary streams can be discharged as waste streams.
For
example, the waste stream typically containing the one or more species
transferred
from the stream treated in separation apparatus 230, can be discharged or
transferred
to the source of water to be treated 202 through conduit or distribution
system 236.
Likewise, other embodiments of the invention contemplate combining one or more
secondary streams, typically from one or more downstream separation apparatus,
with
a water stream to be treated in one or more upstream separation apparatus. The
waste
stream can also be discharged with other streams that may or may not be
directly
associated with the treatment system. For example, the stream to be discharged
may
be returned to the source of water to be treated after being mixed with one or
more
blow down streams from, for example, a cooling tower, which may not be a unit
operation of the treatment system. In other cases, however, the one or more
waste
streams may be stored and combined with water having very low salinity to
Ynitigate
water infiltration problems that could result in leaching soluble minerals,
and salts
such as calcium from surface soils.
In some embodiments of the invention, the secondary stream contained in
conduit 236 from second separation apparatus 230 can be introduced into first
separation apparatus 220, alone or combined, as shown in FIG. 2, with water to
be
treated from source 202 as delivered through conduit 222.
The schematically illustrated systems depicted in FIGS. 1 and 2 may further
comprise unit operations that facilitate the treatment of water. For example,
an
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optional system may be utilized upstream of separation apparatus 220 and 230
to filter
or otherwise remove at least a portion of suspended solids in the water from
source
202. Non-limiting examples of pre-treatment unit operations that may be
utilized to
reduce the concentration of at least one suspended solid entrained in the
water to be
treated include microfilters, settlers, and course particle filters.
Further, one or more unit operations may be utilized to further process one or
more of the treated water streams. For example, a polishing bed may further
remove
one or more species from one or more of the treated streams in distribution
systems
224 and 234. Non-limiting examples of such unit operations that can be
utilized to
remove at least a portion of weakly ionized or ionizable species, such as but
not
limited to, boron, selenite, and arsenic, include ion exchange colunms.
Further unit operations that facilitate post-treatment of one or more treated
water streams of the invention include those that add--or-otherwise adjust a
concentration of one or more desirable species or characteristics of the water
stream.
Post-treatment operations may be employed to render the one or more waste
streams
suitable for discharge to the environment.
Accordingly, a mixer may be disposed downstream of one or more separation
apparatus of the invention that facilitates incorporation of another treated
or untreated
water stream, disinfectants, nutrients, and/or desirable salts from one or
more sources
of such. In accordance with some embodiments of the invention, one or more
sources
of a salt can be disposed to be introduced into the treated water stream. For
example,
a separation apparatus may be utilized in the treatment or irrigation system
of the
invention that selectively removes or reduces the concentration of divalent or
other
non-monovalent species from a water stream to be treated. Such an optional
apparatus would typically provide at least product stream having a relatively
high
concentration of non-monovalent species which can be introduced to the treated
stream to adjust at least one characteristic thereof so as to provide a stream
or body of
water with a target or desirable condition. Examples of systems and techniques
that
advantageously provide beneficial species-rich streams include those disclosed
in
pending U.S. application serial no. i 1/474,299, titled "Electrically-Driven
Separation
Apparatus," the substance of which is incorporated herein by reference. In
some
cases, however, one or more otherwise unconnected or distinct sources of, for
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example, calcium and/or magnesium salts, may be utilized to adjust one or more
characteristics of the treated water stream prior to its use. Additionally,
one or more
intrinsic and/or extrinsic properties of the water stream may be further
adjusted. For
example, the water stream may be cooled or heated to adjust the temperature
thereof.
The pH of the water stream or body may also be adjusted by, for example,
adding one
or more acids or bases, to achieve a desired pH value. The desired property or
'
characteristic may be dependent on a plurality of factors including, for
example, the
pH of the soil to be irrigated, the salt tolerance the crops to be irrigated
and, in some
cases, the moisture content of the soil. Thus, some features of the invention
provide
further capabilities directed to achieving one or more desired composite
characteristics.
The further adjustment of the one or more properties or characteristics may be
performed af-ter-:treatment in the separation apparatus,-prior to use or
introdurg.tion to
the point of use, or during storage of the treated water in one or more
reservoirs.
However, some aspects of the invention contemplate beneficial or
economically attractive attributes of such secondary streams containing high
concentrations of one or more dissolved species, relative to the first or
treated product
stream and/or the stream introduced into the separation apparatus. For
example, the
secondary product stream may contain high dissolved solids and can serve as a
feed
stream that may be further processed to obtain additional products or at least
provide a
product stream having a high concentration of a desirable species.
One or more characteristics of the water utilized in some systems and
techniques of the invention can provide an indication of the suitability of
the water for
agricultural use. For example, the one or more characteristics of the water
can be
represented as the salinity as total dissolved salts or solids content, and/or
electrical
conductivity, as well as or in conjunction with any of the alkalinity, iron
content, and
pH of the water. In some cases, the level of salinity of the water can become
a
selective parameter when considered relative to the type of crops to be
irrigated by the
at least partially treated water. Thus, in accordance with some aspects of the
invention, the salinity of the water may be used to adjust at least one
operating
parameter of the systems of the invention. In other embodiments of the system
and
techniques of the invention, the characteristic value can be represented as a
ratio of
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the concentration of species that tends to render soil as water-impermeable
relative to
the concentration of species that tends to render soil as aggregating or water-
adsorbing.
In accordance with some aspects of the invention, the characteristic value can
5 provide an indication of the suitability of the water for irrigation
purposes, for human
consumption, and/or for livestock or poultry use. In some embodiments, the
characteristic value of a water stream or body can be represented as a ratio
of the
concentration of monovalent species relative to the concentration of divalent
species
in the water. For example, the characteristic value can be at least partially
expressed
10 as the sodium adsorption ratio or exchangeable sodium percentage.
Preferably, the
SAR value of a stream or body of water can provide an indication as to whether
the
water may be suitable to irrigate a type or kind of crop. Thus, in accordance
with
some aspects of the invention, some embodiments thereof relate-to systems and -
techniques that can involve controlling one or. more operating parameters
based at
15 least partially on a desired characteristic value that is at least
partially derived from at
least one requirement of a point of use. Where the point of use is, for
example, a crop
to be irrigated, the desired characteristic value can be based on the salt
tolerance of
the crop and/or one or more attributes or characteristics of the soil.
The sodium adsorption ratio value is typically determined according to the
formula (1),
SAR = [Na]
Ca + Mg
where [Na] is the sodium species concentration, in mol/m3, in the water, [Ca]
is the
calcium species concentration, in mol/m3, in the water, and [Mg] is the
magnesium
species concentration, in moUm3, in the water. Other characteristic values of
the
water may be utilized, alone or in conjunction with other characteristic
values. Thus,
in some cases, the characteristic value of the water that can serve as
indication of
water quality or suitability for its intended purpose involves the total
dissolved solids
concentration in the water, the pH, and/or the concentration of one or more
toxic or
hazardous species.
Adjusting the SAR value of the, for example, irrigation water, may be effected
by adjusting one or more operating parameters of the water system. For
example, the
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16
relative ratio of treated water having various associated SAR values may be
adjusted
to provide a composite or blended mixture of product water having the desired
SAR
value. Other techniques including reducing the flow rate of the water stream
through
the one or more separation apparatus or increase the residence or treatment
period can
facilitate achieving the desired SAR value. In addition or in conjunction with
such
techniques, the applied potential level through, for example, the electrically-
driven or
pressure-driven separation apparatus can also provide treated water having the
one or
more desired characteristics.
The treated water product of the systems of the invention may desalinate
seawater and/or brackish water to provide irrigation water that avoids or
reduces the
extent of any soil permeability and/or infiltration problems.
The one or more characteristic values of the treated water may be a relative
~=.- correlation between -species contained in the water. For exa;yple, the
characteristic -
value may be a ratio of dissolved sodium species to dissolved calcium. A
preferred
desirable sodium to calcium ratio of not more than about 3:1 may avoid or
reduce the
likelihood of water infiltration problems due to soil dispersion and plugging
and soil
surface pore sealing. Further, some embodiments of the invention can
selectively
reduce the concentration of monovalent sodium in irrigation water, a source of
relatively calcium-rich water can be provided to counteract any sodium-
dispersing
phenomena in irrigation.
The product water can have an SAR value in a range from about 2 to about 8.
The target or desirable SAR value may, however, depend on one or more factors
in
the agricultural facility. For example, the target SAR value depend on the
type of
crops grown in the facility, the stage of growth of one or more crops in the
facility,
and the soil conditions including the water infiltration, sodicity, and/or
alkalinity of
the soil. Particular guidelines that may be used to provide one or more target
characteristics of irrigating water include those provided by The Food and
Agriculture
Organization of the United Nations (FAO). For example, the exchangeable sodium
level, which can be correlated to the SAR value, can serve as a desirable
characteristic
value of water utilized for irrigation purposes. In particular, sensitive
crops such as,
but not limited to fruits, nuts, and citrus typically require irrigation water
having an
SAR value of up to about 8; other sensitive crops such as beans may tolerate
irrigation
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.,.
water having an SAR value of up to about 18; moderately tolerant crops such as
clover, oats, and rice may tolerate irrigation water having an SAR value of up
to about
18 to 46; and tolerant crops such as, but not limited to wheat, barley,
tomato, beets,
and tall wheat grass, may tolerate irrigation water having an SAR value of up
to about
46 to 102.
Infiltration issues typically arise when irrigation water does not enter the
soil
and becomes unavailable to crops. In contrast to salinity issues, which reduce
the
availability of water, infiltration problems can effectively reduce the
quantity of water
available for crop use. Water infiltration can increase with increasing
salinity and can
decrease with decreasing salinity or increasing sodium content relative to
calcium and
magnesium. Further, low salinity water, less than about 0.5 dSlm, is typically
corrosive and tends to leach surface soil of soluble minerals and salts, such
as
calcium, which in turn c.an==reduce soil aggregation and structure. -Soil
without or
having low salt content tends to be dispersive, as fine soil particles, which
fill pore
spaces, effectively sealing the soil surface and reducing the rate of water
infiltration.
The soil would tend to form a crust which reduces the amount of water entering
the
subsurface and can also prevent crop emergence. Thus, in some embodiments of
the
invention, the desired water quality may be further based on the salinity of
the
irrigation water. For example, FIG. 4, which is based on a publication by
Ayers, R.S.
and Westcot, D.W., titled "Water Quality for Agriculture," FAO Irrigation and
Drainage Paper 29 rev. 1, Food and Agriculture Organization of the United
Nations,
1989, 1994, and which shows the influence of salinity, as represented by TDS
concentration, and SAR on infiltration, can conjunctively provide desirable
salinity
levels and SAR values of irrigation water that reduces or avoids infiltration
problems.
In FIG. 4, seawater properties were used to derive TDS concentration values
from
electrical conductivity data from the above reference. In particular, the
correlations
between the density and salinity and between the salinity and electrical
conductivity
of seawater at 20 C were determined based on published physical properties.
These
correlations were then used to convert the electrical conductivity values of
seawater
from the above-identified reference into the corresponding TDS concentration,
which
were then mapped relative to the corresponding SAR values to obtain the
infiltration
guidelines presented in FIG. 4.
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Further embodiments of the invention may also provide suitable irrigation
water when it has a composite characteristic value such as having an SAR value
of
less than about 8 while having a TDS level of about 1,500 ppm or more.
Some embodiments of the invention can provide desalination systems and
techniques that selectively remove undesirable species which contrasts to non-
selective desalination techniques such as those based on thermal and pressure-
driven
processes. Further, some systems and techniques of the invention can provide
product
water stream without requiring the further addition of preferred species. For
example,
the invention can provide irrigation water that does not involve further
adjusting
characteristic values by the addition of supplemental species.
FIG. 3 illustrates further features and aspects of the invention. The
treatment
system 300 exemplarily illustrated can comprise a first separation apparatus
304 and a
second separation apparatus 306. Separation,apparatus 304 and 306 typically
treats a.
fluid from one or more sources 302. The water to be treated from source 302
typically contains a high or unacceptable level of dissolved species. The one
or more
separation apparatus can thus be utilized to at least partially remove or
reduce the
concentration of one or more undesirable species from the water. As
exemplarily
illustrated, treated water from separation apparatus 304 can be combined with
treated
water from separation apparatus 306 in one or more mixing operations or mixer
308
to provide a treated water stream having desired properties and/or
characteristics to
point of use 314. In accordance with some embodiments of the invention, the
treated
water may be rendered suitable to be used as potable and/or bathing water in
one or
more points of use 314.
First separation apparatus 304 may be an electrically-driven apparatus or a
pressure-driven apparatus. Likewise, second separation apparatus 306 may be an
electrically-driven separation apparatus or a pressure-driven separation
apparatus. In
accordance with some aspects of the invention, separation apparatus 304
removes at
least a portion of a plurality of undesirable species in water to be treated
from source
302. In some cases, first separation apparatus can indiscriminately remove at
least a
portion of a plurality of undesirable species from the water to be treated.
For
example, the first separation apparatus can utilize RO and/or NF based
techniques to
remove, typically without preference or selectivity, at least a portion of any
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undesirable species. The treated water stream resulting from the pressure-
driven
separation apparatus preferably exceeds potable water quality requirements.
The second separation apparatus can remove one or more undesirable species
from the water stream to be treated. In some cases, the separation apparatus
selectively removes at least a portion one or more undesirable species from
the water
to produce a product water stream. If the product water stream from the second
separation apparatus fails to meet or exceed potable water quality
requirements, a
portion of the treated water from the first separation apparatus that exceeds
the
potable water quality requirements may be incorporated or blended therewith.
For
example, where the first separation apparatus provides product water having a
TDS
level of about 250 mg/L and the second separation apparatus provides product
water
having a TDS level of about 1,000 mg/L, the product water streams can be
combined
in a vplumetric ratio of about-2:1 to produce a, blended product having==a-TDS
level of
about 500 mg/L. The target level can be a concentration that meets or exceeds
one or
more guidelines suggested by the World Health Organization_ Other water
streams
may also be blended with one or more products streams of the separation
apparatus of
the invention to provide drinking and/or bathing water that meet or exceed
guidelines
or requirements typically set by government regulatory organizations.
One or. more reject streams from the first separation apparatus, typically
containing relative high levels of species removed from the first treated
product
stream may be discharged to drain, directed to one or more ancillary points of
use
310, or returned to source 302. Further embodiments of the invention
contemplate
combining the reject water stream with water from source 302 through conduit
322 so
as to be treated in the second separation apparatus. A secondary or reject
water
stream from second separation apparatus may also be discharged to a drain,
directed
to one or more ancillary points of use 310 and/or 312, returned to source 302,
as
shown through conduit 316.
As noted above, ancillary systems may be utilized in the systems and
techniques of the invention in post-treatment operations. For example, one or
more
disinfecting systems such as those that irradiate, oxidize, or otherwise
reduce
microbiological activity in the water may be disposed to further treat the
water.
Further, one or more storage systems as may be also used as discussed above.
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Some features of the invention involve systems and techniques comprising
electrically-driven separation apparatus utilizing selective membranes as
discussed
above. As illustrated in FIG. 7, the quality of the treated water as
represented by for
example, TDS content can be influenced by the selectivity of the membrane
utilized.
5 FIGS. 8A and 8B show the capabilities of the selective separation apparatus
in
accordance with some aspects of the invention. As shown in FIG_ 8A, water,
having a
desirable set of characteristics, can be produced for irrigating crops by
utilizing an
electrically-driven separation apparatus. In some embodiments of the
invention,
electrically-driven separation apparatus utilize monovalent selective
membranes to
10 facilitate treating water, such as seawater and/or brackish water to
provide water
suitable for irrigation in agricultural facilities. In contrast, non-selective
techniques or
even non-monovalent selective techniques such as those that involve reverse
osmosis
= apparatus, distillation apparatus:as well as nanofiltration, cannot
flexiblyprovide
treated water that meets target characteristics. FIG. 8B illustrates in
particular that
15 electrically-driven separation apparatus comprising monovalent selective
membranes
may provide treated water having acceptable sodium adsorption ratio character
relative to TDS content above 2,500 or even 3,000 ppm. Thus, some aspects of
the
invention can provide systems and techniques that target removal of
undesirable
species while retaining less objectionable species.
20 Further, because some embodiments of the invention can selectively remove
monovalent species, any resultant secondary or concentrate streams would be
less
susceptible to scaling and fouling. This feature advantageously allows some
separation embodiments of the invention to operate at higher water recovery
rates,
compared to non-selective techniques, because the volumetric rate of any
secondary
streams can be effectively reduced without or with less concern for
undesirable
precipitation. Thus, some embodiments of the invention directed to utilizing
systems
and techniques that selectively separate monovalent species can be operated at
higher
recovery rates compared to non-selective ED and distillation based separation
apparatus, and even much higher recovery rates compared RO and NF based
separation apparatus. Significantly, because RO and NF based separation
systems
selectively reduce the concentration of non-monovalent species, these
processes
cannot effectively provide treated water having low SAR values.
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21
A further advantage of the selective separation systems and techniques of the
invention pertains to the reduction or removal of non-ionized species that
have little
or no influence on crop growth. For example, silica is typically not
preferentially
removed in the ED-based systems of the invention thereby avoiding any scaling
or
fouling concerns, in secondary streams, that typically arise when treating
silica-
containing water in RO and distillation apparatus. In addition, because
secondary
streams of some embodiments of the invention typically have reduced scalirig
tendencies, the recovery rates in the separation systems and techniques of the
invention are greater than the recovery rates of RO and distillation based
systems.
Controller 106 of the systems of the invention may be implemented using one
or more computer systems. The computer system may be, for example, a general-
purpose-computer such as those based on an Intel PENTIUMO-type processor, a
Motorola PowerPCO processor, a Sun U1traSPARCO.-processor, a Hewlett-Packard
PA-RISCO processor, or any other type of processor or combinations thereof.
The
computer system may be implemented using specially-programmed, special-purpose
hardware, for example, an application-specific integrated circuit (ASIC) or
controllers
intended for water treatment system.
The computer system can include one or more processors typically connected
to one or more memory devices, which can comprise, for example, any one or
more of
a disk drive memory, a flash memory device, a RAM memory device, or other
device
for storing data. The memory component or subsystem is typically used for
storing
programs and data during operation of the system 100 and/or the computer
system.
For example, the memory component may be used for storing historical data
relating
to the parameters over a period of time, as well as operating data. Software,
including
programming code that implements embodiments of the invention, can be stored
on a
computer readable and/or writeable nonvolatile recording medium, and then
typically
copied into the memory subsystem wherein it can then be executed by one or
more
processors. Such programming code may be written in any of a plurality of
programming languages, for example, Java, Visual Basic, C, C#, or C++,
Fortran,
Pascal, Eiffel, Basic, or any of a variety of combinations thereof.
Components of the computer sy5tem may be coupled by an interconnection
mechanism, which may include one or more busses that provide communication
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22
between components that are integrated within a same device and/or a network
that
provide communication or interaction between components that reside on
separate
discrete devices. The interconnection mechanism typically enables
communications,
including but not limited to data and instructions to be exchanged between
components of the system.
The computer system can also 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,
computer system may contain one or more interfaces that can connect the
computer
system to a communication network, in addition or as an altemative to the
network
that may be formed by one or more of the components of the system.
According to one or more embodiments of the invention, the one or more
input devices=.may include sensors for measuring parameters. Alternatively,
tbe-
sensors, the metering valves and/or pumps, or all of these components may be
connected to a communication network that is operatively coupled to the
computer
system. For example, one or more sensors 108 may be configured as input
devices
that are directly connected to controller 106, metering valves, pumps, and/or
components of apparatus 102 may be configured as output devices that are
connected
to controller 108. Any one or more of such subcomponents or subsystems may be
coupled to another computer system or component so as to communicate with the
computer system over a communication network. Such a configuration pemiits one
sensor to be located at a significant distance from another sensor or allow
any sensor
to be located at a significant distance from any subsystem and/or the
controller, while
still providing data therebetween.
The controller can include one or more computer storage media such as
readable and/or writeable nonvolatile recording medium in which signals can be
stored that define a program to be executed by the one or more processors. The
medium may, for example, be a disk or flash memory. In typical operation, the
processor can cause data, such as code that implements one or more embodiments
of
the invention, to be read from the storage medium into a memory that allows
for faster
access to the information by the one or more processors than does medium. The
memory is typically a volatile, random access memory such as a dynamic random
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23
access memory (DRAM) or static memory (SRAM) or other suitable devices that
facilitates information transfer to and from the one or more processors.
Although the control system is described by way of example as one type of
computer system upon which various aspects of the invention may be practiced,
it
should be appreciated that the invention is not limited to being implemented
in
software, or on the computer system as exemplarily shown. Indeed, rather than
implemented on, for example, a general purpose computer system, the
controller, or
components or subsections thereof, may alternatively be implemented as a
dedicated
system or as a dedicated programmable logic controller (PLC) or in a
distributed
control system. Further, it should be appreciated that one or more features or
aspects
of the invention may be implemented in software, hardware or firmware, or any
combination thereof. For example, one or more segments of an algorithm
executable
by controller 106 can be perforrned in separate computers; which in turn, can
be
communication through one or more networks.
Although various embodiments exemplarily shown have been described as
using sensors, it should be appreciated that the invention is not so limited.
The
invention contemplates the modification of existing facilities to retrofit one
or more
systems, subsystems, or components and implement the techniques of the
invention.
Thus, for example, an existing facility, especially an agricultural or crop-
growing
facility, can be modified to include one or more systems configured to provide
irrigation water, potable water, or both, accordance with any one or more
embodiments exemplarily discussed herein. Alternatively, existing systems
and/or
components or subsystems thereof can be modified to perform any one or more
acts
of the invention.
Examples
The function and advantages of these and other embodiments of the invention
can be further understood from the examples below, which illustrate the
benefits
and/or advantages of the one or more systems and techniques of the invention
but do
not exemplify the full scope of the invention.
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Example 1
This example describes the expected performance of anti/D apparatus when
utilized to selectively remove monovalent cations from a stream to be treated
and
produce treated water having a lower SAR value.
FIG. 5 is a graph showing the SAR value in the treated water utilizing various
monovalent selective membranes, with differing levels of selectivity. As
shown, if
the acceptable or desired SAR value is less than about 6, then a TDS level of
about
3,500 ppm can be achieved with a monovalent selective membrane having a
selectivity of about 5. Also, if the acceptable or desired SAR value is less
than about
3, then a TDS level of about 2,700 ppm can be achieved with a monovalent
selective
membrane having a selectivity of about 10.
The predicted energy requirement for the ED apparatus is less than the
;=predicted requirement utilizing the RO apparatus. Further, the predicted
energy
required to treat water in an electrically-driven separation apparatus of the
invention is
expected to be linearly affected by the salinity of the water to be trea=ted.
In some
embodiments of the invention, the temperature of the feed stream can be
adjusted to
reduce the energy required to facilitate cost effective separation in an
electrically-
driven separation apparatus. For example, increasing the temperature of the
feed
stream comprising seawater by about 25 C to provide for a product TDS level
of
about 1,500 ppm and a recovery of about 50 %, can result in a predicted energy
reduction of about 6 % in an ED module.
Example 2
This example describes the performance of a system utilizing the techniques
of the invention as substantially represented in the schematic illustration of
FIG. 1,
except that a controller was not utilized to adjust an operating parameter of
the
system.
The ED stack was comprised of ten effective cell pairs of concentrating and
diluting compartments, five cell pairs in a downward flow path and five cell
pairs in
an upward flow path, providing for an overall fluid stream process flow path
of about
28 inches. The cell pairs utilized cation selective membranes, CMS monovalent
selective homogeneous membranes from Tokuyama Corporation to preferentially
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remove sodium cations, an'd heterogeneous ion exchange membranes for the anion
selective membrane (IONPURETM anion membrane, 0.018 inches thick). Spacer
gaskets that were 0.020 inches thick and extruded screens about 70 % open area
and
0.020 inches thick were used to at least partially define the compartments.
The ED
5 apparatus was operated at an applied potential of about 2 volts per cell
pair, through
Ru02-coated titanium electrodes.
The feed water was prepared by dissolving Instant Ocean synthetic sea salt
mixture, available from Spectrum Brands Inc., in deionized water. Sodium
chloride
was added as needed to provide a feed solution that had an SAR value of
seawater
10 (about 54).
The module was operated in a once-through mode wherein both the dilute and
concentrate streams were returned to the feed tank. The electrode chambers
were
- constructed as dilute qqmpartments and fed separately. Calcium and magnesium
;~; =
species concentrations in the feed and product streams were determined by
standard
15 titration methods. The TDS level was calculated based on the measured
conductivity.
The sodium concentration was also calculated.
Tables 1 and 2 respectively show the inlet and product water stream
characteristics. As shown in Table 2, the systems and techniques of the
invention can
provide a product water stream having one or more desired characteristics. For
20 example, the systems and techniques of the invention can selectively reduce
the
concentration of monovalent species to provide water having a desired SAR
value.
Further, the data presented in the tables show that coupling two or more
electrically-driven separation apparatus can provide treated water having a
desired
SAR value. That is, a first electrically-driven separation apparatus can lower
the SAR
25 value of a water stream to provide an intermediate product stream having an
intermediate SAR value. The intermediate product stream can in turn be
introduced
into a second electrically-driven separation apparatus to provide treated
water having
the desired SAR value. In particular, FIG. 6 shows that the TDS level and SAR
value
can be reduced to desirable levels by utilizing ED apparatus, having
monovalent
selective membranes, in about three stages based on this configuration. Other
configurations may involve more or less stages to achieve one or more desired
water
characteristics.
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The data further shows that various parameter can be adjusted tailor the SAR
value in the product water. For example, the processing flow rate can be
increased or
decreased to achieve a target SAR value. Alternatively, or in conjunction with
adjusting the flow rate, the applied potential and/or overall flow path length
can be
used as an adjustable operating parameter in one or more aspects of the
invention.
Table 1. Feed Stream Characteristics.
Flow Rate Conductivity Ca Mg TDS Na SAR
L/m mS/em ppm m m m -
0.064 33.7 340 1940 24062 6397 29.4
0.072 33.7 340 1940 24062 6397 29.4
0.072 33.7 340 1940 24062 6397 29.4
0.076 34.7 352 1928 24836 6673 30.7
0.1 15.8 224 1196 10596 2418 14.1
0.122 33.7_ 340 1940.". 24062 6397.. 29.4
0.148 49.7 316 1784 37426 11339 54.4
Table 2. Product Stream Characteristics.
Flow Rate Conductivity Ca Mg TDS Na SAR
L/m mS/em ppm ppm m m -
0.064 16.0 236 1584 10766 2094 10.7
0.072 16.2 252 1588 10880 2116 10.8
0.072 22.1 284 1756 15164 3453 16.8
0.076 24.8 292 1720 17159 4192 20.5
0.1 5.2 124 740 3374 374 2.8
0.122 23.3 276 1724 16031 3800 18.6
0.148 36.4 268 1652 26163 7493 37.5
Example 3
This example compares the performance of electrically-driven separation
apparatus to the performance of thermally-driven and pressure-driven
separation
apparatus.
The ED module utilized had ten cell pairs in a folded flow path so that the
flow passed through five cell pairs of diluting and concentrating compartments
then
turned and passed through another five cell pairs. Each cell in the module was
comprised of a screen and a 0.020 inch thick spacer. The cells were 14 inches
by
1.2 inches. The monovalent cation selective membrane utilized was a CMS
membrane from Tokuyama Soda Corporation. The anion selective membrane utilized
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was an IONPURETM heterogeneous membrane. The ED module utilized platinum-
coated titanium plates. The applied voltages and current, flow rates and feed
compositions were varied to obtain various conditions of effective
selectivity.
Tables 3 and 41ist the feed and product water stream properties. FIG. 7 is a
graph showing the influence of the TDS level of the treated water relative to
the
selectivity of the membrane utilized in the ED module. The TDS content of the
feed
and product streams as well as the concentrations of sodium, calcium, and
magnesium
were analyzed. These measured values were utilized to calculate the effective
selectivity according to the formula (2):
AV Na
Selectivity = y "a
2 OV Ca -f- AV I,qs
VCa +VMg
where v is the molarity of ionic species i and Av is the change in the
molarity of ionic
species i.
Table 3. Feed Stream Characteristics.
Ca Mg TDS SAR Na
m Ppm m - m
1 126 428 37426 121.66 12822
2 141 1928 24836 75.42 -8283
3 136 1940 24062 72.92 8009
4 136 1940 24062 72.92 8009
5 136 1940 24062 72.92 8009
6 136 1940 24062 72.92 8009
7 355 5112 40268 72.13 12850
8 306 4396 35028 '67.75 11193
9 234 3396 27129 59.78 8674
10 163 2340 19281 51.29 6184
11 98 1336 11356 39.93 3651
12 90 1196 10596 39.45 3419
13 32 384 4014 26.5 1313
14 32 384 4014 26.5 1313
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Table 4_ Product Stream Characteristics and Calculated Selectivity.
Ca Mg TDS SAR Na Selectivity
ppm rn m - m -
1 107 396 26163 87.84 8852 1.8
2 -292 1720 17159 54.42 5614 1.4
3 276 1724 16031 50.72 5217 1.4
4 252 1588 10880 34.66 3420 1.5
284 1756 15164 47.14 4897 1.8
6 236 1584 10766 34.51 3386 1.4
7 804 5036 34123 60.92 10707 3.1
8 704 4276 29348 56.79 9217 2.5
9 536 3324 21566 47.05 6724 3.7
304 1972 8897 23.73 2604 1.7
11 188 1148 6187 22.26 1871 1.6
12 124 740 3374 14.58 986 0.9
13 44 236 1321 10.4 400 0.9
14 32 168 651 5.57 181 0.8
The data in Tables 3 and 4 as well as FIG. 7 show that as the TDS content of
the feed water decreases the selectivity of the cation selective membrane also
5 decreases. The correlation of selectivity to TDS determined to follow the
formula (3):
Selectivity = 0.5905 + (5x10-5 XTDS)
This selectivity/TDS relationship was then utilized to characterize the
capabilities electrically-driven separation apparatus in accordance with the
invention
in terms of a composite characteristic as represented in FIGS. 8A and 8B,
relative to
10 other non-selective techniques reverse osmosis, distillation, and
nanofiltration.
It is assumed that about 96 % of the monovalent cationic species in seawater
is
sodium and about 4 % is potassium. Further, all the cationic species is
assumed to
constitute about 37 % of the TDS content such that the change in TDS can be
determined according to the formula (4):
23 AN' + 40(Avi ce )+ 24(Av N,g )= 0.37(OTDS)
(0.96)
Further assuming that the divalent species calcium and magnesium behave
similarly when being removed in the electrically-driven separation apparatus,
the
following formula can be utilized:
AV C. _ OV Ms
VCa vMg
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29
The above assumptions utilizing formulas (2), (3), and (4) were used to
predict
the product water SAR value relative to TDS level. The results are presented
in
FIGS. 8A and 8B, the latter showing an enlarged section of the former. FIG.
8B,
which includes an overlay defining a region of preferred characteristics for
some
crops, shows that the separation techniques of the invention can provide a
plurality of
actual product streams that satisfy or span the limits the set of target
characteristics.
Notably, the separation systems and techniques of the invention provide
intermediate
and/or tailorable features that cannot be directly achieved with the non-
selective
alternatives. Nonetheless, to provide a comparative basis, intermediate
properties of
treated water were approximated by approximating an assumed blend of the
actual
resultant product with a proportionate amount of raw or untreated seawater.
For
example, to provide an estimate of the nature of the SAR/TDS relationship for
distilled water product, feed seawater was mixed with actual distillate water
to predict
the characteristic values of an intermediate product. Although such practices
are not
typical employed, the illustrated predicted intermediate characteristics, as
noted by the
dashed line connecting actual data, were presented to provide a comparison
relative to
the selective separation systems. The nature of the SAR/TDS relationship for
reverse
osmosis and nanofiltration systems were likewise approximated by estimating
the
properties of a theoretically blended product. Thus, for each of the discrete,
non-
tailorable technique, dashed lines connecting actual data points represent an
hypothetically achievable tailorable product whereas solid lines connecting
actual
data values show achievable tailorable product.
The actual distillate water properties were obtained from a publication by the
U.S. Dept. of Interior, Bureau of Reclamation, Denver Office, titled "Water
Treatment Technology Program Report," no. 7, 1995. The actual data for non-
selective ED product water properties were obtained from a publication by
Turek, M.,
"Cost Effective Electrodialytic Seawater Desalination," Desalination, no. 153,
pp.
371-376, 2002. The actual data for nanofiltered product water properties were
obtained from a publication by Tseng, et al., "Optimization of Dual-Staged NF
Membranes for Seawater Desalination," AWWA 2003 CA-NV An. Fall Conf., 2003.
Having now described some illustrative embodiments of the invention, it
should be apparent to those skilled in the art that the foregoing is merely
illustrative
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and not limiting. Numerous modifications and other embodiments are within the
scope of one of ordinary skill in the art and are contemplated as falling
within the
scope of the invention. In particular, although many of the examples presented
herein
involve specific combinations of inethod acts or system elements, it should be
5 understood that those acts and those elements may be combined in other ways
to
accomplish the same objectives. For example, ED and EDI apparatus may be
combined in a two-stage process wherein the ED apparatus reduces the TDS level
in
seawater to a range of about 5,000 ppm to about 6,000 ppm and the EDI
apparatus
subsequently reduces the TDS level to a range of about 1,500 ppm to about
10 2,000 ppm.
Further, acts, elements, and features discussed only in connection with one
embodiment are not intended to be excluded from a similar role in other
embodiments.
It is to be appreciated that various alterations, modifications, and
15 improvements can readily occur to those skilled in the art and that such
alterations,
modifications, and improvements are intended to be part of the disclosure and
within
the spirit and scope of the invention. For example, the sodium adsorption
ratio may
be represented according to an alternative formula (5):
Na
adjRNa=
Cax +Mg
2
20 where Na is the sodium concentration in the water, in me/L; Ca,' is a
modified calcium
value, in me/L, that represents calcium species concentration in the water
with
compensation due to the salinity of the water, the HCO3/Ca ratio (in me/L),
and the
estimated partial pressure of COa in the soil surface; and Mg is the
concentration of
magnesium species in the water, in me/L.
25 Moreover, it should also be appreciated that the invention is directed to
each
feature, system, subsystem, or technique described herein and any combination
of two
or more features, systems, subsystems, or techniques described herein and any
combination of two or more features, systems, subsystems, and/or methods, if
such
features, systems, subsystems, and techniques are not mutually inconsistent,
is
30 considered to be within the scope of the invention as embodied in the
claims.
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31
Use of ordinal terms such as "first," "second," "third," and the like in the
claims to modify a claim element does not by itself connote any priority,
precedence,
or order of one claim element over another or the temporal order in which acts
of a
method are performed, but are used merely as labels to distinguish one claim
element
having a certain name from another element having a same name (but for use of
the
ordinal term) to distinguish the claim elements.
Those skilled in the art should appreciate that the parameters and
configurations described herein are exemplary and that actual parameters
and/or
configurations will depend on the specific application in which the systems
and
techniques of the invention are used. Those skilled in the art should also
recognize or
be able to ascertain, using no more than routine experimentation, equivalents
to the
specific embodiments of the invention. It is therefore to be understood that
the
embodiments described herein are presented by way of example only and that,
within
the scope of the appended claims and equivalents thereto; the invention may be
practiced otherwise than as specifically described.
As used herein, the term "plurality" refers to two or more items or
components. The terms "comprising," "including," "carrying," "having,"
"containing," and "involving," whether in the written description or the
claims and the
like, are open-ended terms, i.e., to mean "including but not limited to."
Thus, the use
of such terrns is meant to encompass the items listed thereafter, and
equivalents
thereof, as well as additional items. Only the transitional phrases
"consisting of' and
"consisting essentially of," are closed or semi-closed transitional phrases,
respectively, with respect to the claims. Further the use of the term
"potable" with
reference to water, especially treated water, does not limit the scope of the
inventive
subject matter and can refer to water suitable for livestock use, including
consumption.
