Note: Descriptions are shown in the official language in which they were submitted.
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TREATMENT OF WASTEWATER
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application
Serial No.
61/570,115, filed December 13, 2011, and U.S. Provisional Application Serial
No.
61/721,853, filed November 2, 2012. The entire contents of the above
applications are
incorporated by reference herein.
FIELD OF APPLICATION
[0002] This application relates generally to systems and methods for removing
to contaminants from water and wastewater.
BACKGROUND
[0003] Certain undesirable materials are found to be contaminants in water and
wastewater. Water streams can be contaminated with substances like iron,
manganese,
organic matter, suspended solids, hydrogen sulfide, or bacteria. Iron causes
taste and
odor problems in potable water, causes staining in laundry, wash, swimming
pool, or
process water, and it causes fouling and deposits in boiler and cooling water
systems. In
many aqueous systems such as drain water, bilge water, grease traps, and
holding tanks,
odors can be caused by sulfides, mercaptans, and organic matter. These odors
can be
treated by oxidizing agents, but the oxidizers can be difficult to administer
in low-flow or
unattended areas. There remains a need for improved methods to treat metals,
organics,
bacteria, suspended solids, and odor compounds in water streams.
[0004] Wastewater management is a major problem in the petroleum industry.
Petroleum
industry wastewater includes oilfield produced water and aqueous refinery
effluents.
Petroleum industry wastewater also includes flowback water from hydraulic
fracturing of
oil-containing or natural-gas-containing geological formations.
[0005] Contaminants found in oilfield produced water, flowback water, and
aqueous
refinery effluents can include, at varying levels, materials such as: (1)
dispersed oil and
grease, if not removed by mechanical pretreatment separators can clog post-
treatment
equipment; (2) benzene, toluene, ethylbenzene and xylenes (BTEX), a volatile
fraction;
(3) water-soluble organics; (4) sparingly soluble nonvolatile organics,
including
aromatics with molecular weights higher than BTEX but lower than asphaltenes;
(5)
treatment chemicals, such as drilling, completion, stimulation and production
chemicals;
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(6) produced solids like clays, silicates and metal sulfides, usually removed
by
mechanical separators; and (7) total dissolved solids including metals, a
particular
problem because many metals are considered toxic. A variety of treatments are
available
to remove these contaminants, including the use of organophilic clays,
activated carbon
type adsorbents, ion exchange resins, coalescers, coagulants, filters,
absorbers, alpha
hydroxy acids, dithiocarbamates for metals, and media filtration. There
remains a need in
the art, however, to identify more effective, efficient and cost-conscious
solutions to these
wastewater problems.
[0006] The urgency for improved wastewater management in the petroleum
industry is
heightened by rising public concern over environmental hazards and toxicities.
For
selenium, as an example, the U.S. Environmental Protection Agency (EPA) plans
to
incorporate new discharge limits as low as 5 ppb. Current technologies for
selenium
removal include adsorption & precipitation, ion exchange, chemical or
biological
reduction, oxidation, and membrane treatment (nano-filtration or reverse
osmosis). Even
using these methods, it may be difficult and costly to meet the standards that
the EPA is
considering. Zinc and its compounds are another set of regulated inorganic
contaminants
in petroleum refinery wastewater. These compounds originate from many sources
within
a refinery including artificial addition, and require end-of-pipe treatment.
Zinc
compounds and other metals can be removed from wastewater using technologies
such as
lime precipitation, coagulation & flocculation, activated carbon adsorption,
membrane
process, ion exchange, electrochemical process, biological treatment, and
chemical
reaction to achieve in practical large scale. Some regulatory agencies have
set discharge
limits for these and other metals that exceed the capacity for commercial
metals removal
processes. A pressing need exists to improve methods for removing metals from
wastewater in light of the increasing regulatory scrutiny of such wastewater
contaminants.
[0007] Petroleum industry wastewater also includes water used for hydraulic
fracturing.
In the recovery of oil and gas from geological formations, hydraulic
fracturing is a
process of pumping fluids into a wellbore at high pressures to fracture the
hydrocarbon-
bearing rock structures. This fracturing increases the porosity or
permeability of the
formation and can increase the flow of oil and gas to the wellbore, resulting
in improved
recovery. Hydraulic fracturing for hydrocarbon-containing formations typically
uses
water obtained from two sources: 1) surface water derived from water wells,
streams,
lakes, and the like, that has not been previously used in the fracturing
process; and 2)
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water that has been used in, and/or flows back from fracturing operations
("frac flowback
water"). Processes exist for treating both surface and flowback water sources
to prepare
them for use or re-use in hydraulic fracturing. Without appropriate treatment,
contaminants entering the frac water can cause formation damage, plugging,
lost
production and increased demand for further chemical additives.
[0008] Frac flowback water typically contains contaminants that were
introduced into the
system during the hydraulic fracturing process. Such contaminants may be
introduced
from the surface water originally used in the process, or they may enter the
flowback
water from its previous exposure to the reservoir. These contaminants include
dissolved
metals, salts, and organics, dispersed particulates, and organics emulsions.
Such
contaminants alter the properties of the fluid and can prevent their reuse as
a hydraulic
fracturing fluid.
[0009] For example, iron in hydraulic fracturing water can cause corrosion,
plugging of
downhole formations and equipment, an elevated demand for frac additive
chemicals, and
membrane fouling in treatment processes. Techniques available for removing
iron from
frac water include aeration and sedimentation, softening with lime soda ash,
and ion
exchange. Aeration and other chemical oxidation practices are known for
household well
water treatment to remove iron. Oxidation converts the soluble iron II (Fe+2)
form to the
less soluble iron III (Fe+3) oxidation state, causing it to precipitate, often
as iron
hydroxide, which is collected by filtration or sedimentation. Greensand iron
removal is
one of the typical methods. However, greensand impregnated with potassium
permanganate is only capable of treating iron concentrations up to a few ppm,
while the
iron concentration in oilfield frac flowback water and produced water can be
as high as
300 ppm. Current methods of oxidant encapsulation and controlled release for
soil and
ground water remediation are not suitable for oilfield frac flow back water
iron removal
since the oxidant release rate is too slow for continuous flow through
process. Ion
Exchange and chelating resins cannot remove iron effectively from frac
flowback water
due to the co-existence of the high concentrations of other multivalent
cations. There
remains a need in the art, therefore, to provide water treatment systems and
methods that
can remove iron contaminants effectively from water to be used in hydraulic
fracturing,
especially frac flowback water, where iron contaminants reach high levels.
[0010] Furthermore, in many solid-liquid separators the removal of gelatinous
particles
such as iron hydroxides and other metal hydroxides is a challenge. Filtration
is one
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method of removal, although it has significant challenges to overcome. Small
gelatinous
particles can pass through all but the finest openings. Filters for their
removal can
quickly become plugged, especially with high concentrations of particles. When
this
happens, the only way to restore effective operation is to either backwash or
replace the
filter, both of which will typically cause disruptions the process continuity.
Gelatinous
particles can also be removed through clarification. This method tends to be
preferable to
filtration for higher concentrations of particles. Clarifiers allow particles
sufficient time
to settle out by spontaneous separation due to density. Often a flocculant is
used to bind
small particles together, which improves their settling rate. The faster the
settling rate of
the particle impurities, the smaller the clarifier needs to be. Even when
flocculants are
used with clarifiers, these agents have a limited efficacy. Additionally, the
underflow
from these clarifiers is typically high in water concentration.
[0011] Larger, denser gelatinous particles are easier to separate from water
and retain less
water in the solids concentrate stream. Thus they settle faster, requiring
smaller settling
tanks. They do not deform when filtered, and therefore do not plug the filter
as quickly.
They can even be used in continuous filter operations, with the filtered
particles being
removed from the filter during operation, preventing the need for downtime.
There
remains a need in the art, therefore, for systems and methods to remove
gelatinous
particles from fluid streams, especially fine gelatinous particles. It would
be desirable to
incorporate these systems and methods into an integrated water treatment
system with
other treatment modalities to interface with the hydraulic fracturing
processes efficiently,
and that prepare water in a cost-effective way for use in these processes.
[0012] Taken generally, the on-site removal of the various contaminants in
frac flowback
water allows it to be used in subsequent hydraulic fracturing operations,
providing
significant benefits due to reduced costs and environmental impact. The
capability for
on-site treatment of frac flowback water is particularly advantageous, because
it does not
require the transportation of the water to and from off-site treatment
facilities.
SUMMARY
[0013] Disclosed herein, in embodiments, are systems and methods for water
treatment,
comprising one or more systems selected from the group consisting of: a
bacteria-removal
substrate modifier system; a dissolved-metals removal substrate-modifier
system; a
suspended-solids removal substrate-modifier system; a hardness-removal system;
an
organic-removal or oil-removal substrate-modifier system; and an oxidizing
agent
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technology system. In an exemplary embodiment, the system comprises a
dissolved-
metals removal substrate-modifier system; a suspended-solids removal substrate-
modifier
system; and an oxidizing agent technology system. Further disclosed herein, in
embodiments, are systems and methods for removing an oxidizable target
contaminant
from a fluid, comprising: an oxidizing agent, wherein adding the oxidizing
agent to the
oxidizable target contaminant forms an oxidized species that precipitates as
an insoluble
precipitate in the fluid; a substrate that forms a removable complex with the
insoluble
precipitate, thereby sequestering the oxidizable target contaminant; and a
removal system
for removing the removable complex from the fluid. In embodiments, the
oxidizable
target contaminant comprises iron. In embodiments, the substrate comprises
diatomaceous earth. In embodiments, the insoluble precipitate is modified to
form a
flocculated precursor having affinity for the substrate, whereby flocculated
precursor
complexes with the substrate to form the removable complex. In embodiments,
the
removable complex comprises an agglomerate comprising the substrate and the
flocculated precursor, the flocculated precursor comprising the insoluble
precipitate. In
embodiments, the substrate is a modified substrate, which can comprise anchor
particles.
In embodiments, the anchor particles are tether-bearing anchor particles. In
embodiments, the system further comprises an activator added to the fluid,
wherein the
activator binds to the insoluble precipitate. In embodiments, the removable
complex
comprises an anchor particle, a tether polymer attached thereto, and an
activator that
binds to the tether and that binds to the insoluble precipitate. In
embodiments, the anchor
particles can be less dense than the fluid. In embodiments, the anchor
particles can
comprise gas bubbles, which may be formed by a chemical action of the
oxidizing agent.
In embodiments, the system may further comprise a hydrophobic modifier.
[0014] Further disclosed herein, in embodiments, are methods for removing a
dissolved
contaminant from a fluid stream, comprising: converting the dissolved
contaminant to an
insoluble form; introducing an anchor particle into the fluid stream, wherein
the anchor
particle has an affinity for the insoluble form to form a removable complex
therewith; and
removing the removable complex from the fluid stream. In embodiments, the
anchor
particle is less dense than the fluid stream. In embodiments, the anchor
particle
comprises gas bubbles. In embodiments, the affinity of the anchor particle for
the
insoluble form is mediated by a tether polymer attached to the anchor
particle. In
embodiments, the method further comprises adding an activator polymer to the
fluid
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stream, wherein the activator particle attaches to the insoluble form to
produce a
flocculated complex attachable to the anchor particle. In embodiments, the
dissolved
contaminant comprises iron, and the step of converting the dissolved
contaminant to the
insoluble form comprises oxidizing the iron. In embodiments, the insoluble
form is an
insoluble precipitate. In embodiments, the removable complex comprises gas
bubbles. In
embodiments, a hydrophobic activator may be added to the fluid stream, wherein
the
hydrophobic activator attaches to the insoluble form to produce a hydrophobic
complex
attachable to the anchor particle.
[0015] In other embodiments, methods are disclosed herein for removing a metal
ion
species from a fluid stream, where the metal iron species is a soluble metal
ionic species,
and where the steps of the method include oxidizing the soluble metal ion
species with an
oxidizing agent to form an insoluble oxidized species; flocculating the
insoluble oxidized
species to form flocculated particulates; providing a substrate that has
affinity for the
flocculated particulates; introducing the substrate into the fluid stream to
contact the
flocculated particulates, whereby contacting the substrate with the
flocculated particulates
forms a removable complex; and removing the removable complex from the fluid
stream,
thereby removing the metal ion species. The metal ion species can be a ferrous
ion. The
substrate can comprise diatomaceous earth, and the substrate can be combined
with an
additive comprising the metal ion species in an oxidized or a reduced state.
In an
embodiment, the substrate comprises diatomaceous earth and the additive
comprises a
ferrous ion. In an embodiment, the substrate comprises diatomaceous earth and
the
additive comprises a ferric ion. In an embodiment, the substrate can be coated
with the
additive, and the substrate can be diatomaceous earth and the additive coating
can
comprise a ferrous or a ferric ion.
[0016] BRIEF DESCRIPTION OF FIGURE
[0017] The Figure is a diagram of a water treatment system in accordance with
these
systems and methods.
DETAILED DESCRIPTION
[0018] Disclosed herein are systems and methods for removing contaminants from
an
aqueous stream using systems and methods that add treatment agents comprising
anchor
particles and tethers, with optional activating agents or activators, all as
described below
in more detail. The anchor particles and tethers, with optional addition of
activators, can
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remove the contaminants from the fluid stream by forming removable complexes
with
them. In embodiments, these systems and methods may be applied to particular
applications, for example removal of contaminants in aqueous streams
associated with the
petroleum industry.
A. CONTAMINANT REMOVAL FROM AQUEOUS STREAMS
1. Anchor Particles, Tethers and Activators Generally
[0019] In certain embodiments, target contaminants are made insoluble by
addition of
precipitating agent or by chemical reaction such as oxidation. The insoluble
solids thus
formed are then bound to an added particle, yielding a removable complex which
has
superior separation characteristics compared to the solids. Such particles
(termed "anchor
particles" and discussed below in more detail) may be modified to target
dissolved
contaminants, thereby making them insoluble or immobilized. Removable
complexes
form between the anchor particles and the target contaminants, and these
particle-solid
complexes can be removed by ordinary techniques such as particle filtration or
settling.
[0020] In the disclosed systems and methods, contaminants can be removed from
an
aqueous stream by converting the contaminants into a form that is easier to
remove, and
then removing the contaminants. In embodiments, difficult-to-separate
particles are
bound to easy-to-separate particles to take advantage of the separation
properties of the
latter. In embodiments, the separation properties of the easy-to-separate
particles include
rapid settling, rapid rising, rapid floating, rapid centrifuging, or rapid
filtering. The easy-
to-separate particles, the "anchor particles," form removable complexes with
the difficult-
to-separate particles, called "target particles." Exemplary anchor particles
are coarse sand
and cellulose fibers. An exemplary target particle is precipitated ferric
hydroxide.
[0021] As used herein, the term "anchor particle" refers to a particle that
facilitates the
separation of fine particles from a fluid stream, where such a particle can
have any shape
or size, including spherical, amorphous, flake, fiber, or needle morphology,
and where
such a particle can be made of organic or inorganic materials, gas bubbles, or
a
combination thereof Organic materials for anchor particles can include one or
more
materials such as starch, modified starch, polymeric spheres (both solid and
hollow), and
the like. Anchor particle sizes can range from a few nanometers to few hundred
microns.
In certain embodiments, macroscopic particles in the millimeter range may be
suitable. In
embodiments, an anchor particle may comprise materials such as lignocellulosic
material,
cellulosic material, minerals, vitreous material, cementitious material,
carbonaceous
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material, plastics, elastomeric materials, and the like. In embodiments,
cellulosic and
lignocellulosic materials may include wood materials such as wood flakes, wood
fibers,
wood waste material, wood powder, lignins, cellulose fibers, wood pulp, or
fibers from
woody plants.
[0022] In embodiments, the anchor particle can be added from an extrinsic
source. In
embodiments, the anchor particle can be produced intrinsically, for example by
the
formation of gas bubbles through chemical means during the separation process.
In
embodiments, the anchor particle can be denser than the medium containing the
contaminants. Contaminants that complex with such anchor particles tend to
sink out of
suspension, allowing their separation via gravity, centrifugation, and the
like. In other
embodiments, the anchor particle can be less dense than the medium containing
the
contaminants. Contaminants that complex with such anchor particles tend to
float
towards the surface of a suspension, allowing their separation via skimming or
other
mechanical means. In embodiments, the anchor particle can have a density
similar to that
of the fluid stream, so that it neither floats nor sinks, but remains in
suspension. Such
neutral buoyancy complexes can be removed by conventional means such as
filtration,
centrifugation, and the like.
[0023] In certain contaminated water sources, such as those having a high
Total Dissolved
Solids (TDS) content of 50,000-150,000 ppm, or in some cases 150,000-350,000
ppm or
greater, the precipitated contaminants (i.e., target particles) are amenable
to flotation, in
part due to the higher density of the water and in part due to the higher
surface tension.
For situations where flotation represents a more suitable approach to
contaminant
removal, anchor particles can be selected that have a lower density than the
fluid stream,
so that the contaminants complexed thereto can be removed by flotation. Anchor
particles having a density lower than the density of the aqueous stream, such
as hollow
anchor particles or gas bubbles, facilitate the floating of target particles
for removal as a
flotation sludge.
[0024] In certain embodiments, a low density anchor particle may include a gas
bubble,
such as air, nitrogen, oxygen, carbon dioxide, methane, propane, butane, and
mixtures
thereof The gas bubbles can be introduced to the aqueous stream by chemical
means or
by mechanical means; they may be introduced extrinsically or produced
intrinsically.
The chemical means of intrinsic gas bubble introduction can include the
reaction or
decomposition of gas-evolving substances, such as peroxides, azo compounds,
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carbonates, bicarbonates, gas hydrates, and the like. The use of some
oxidants, such as
hydrogen peroxide and bleach, can cause bubble generation within the system.
One
mechanism of bubble formation by hydrogen peroxide is the decomposition of
peroxide
in the presence of iron or enzymes such as catalase, causing the release of
oxygen.
Bleaching chemicals such as sodium hypochlorite can release chlorine-
containing gases,
including chloramines when reacting with residual ammonia or ammonium in the
water.
The gas bubbles generated by these reactions can deposit themselves onto the
flocs, and
after sufficient bubble attachment the bubbles make the flocs buoyant and
float.
Mechanical means for extrinsic gas bubble introduction can include air
entrainment,
lo pump cavitation, gas sparging, gas diffusing, impingement, sonication,
and dissolved gas
evolution. In embodiments the gas bubble anchor particles have an average
diameter of
10-1000 microns.
[0025] In one embodiment, an anchor particle can be modified to promote its
binding to a
target particle. The modifying agent is called a "tether," a material that has
a specific
affinity with an untreated and/or a modified target particle. As an example,
an anchor
particle can be treated prior to use with a cationic polymer such as
poly(diallyldimethyl
ammonium chloride) (PDAC), epichlorohydrin/dimethylamine polymer, chitosan,
polyethylenimine, polyallylamine, poly(styrene/maleic anhydride imide), and
the like,
which will act as a tether in interactions with the target particle. In these
embodiments,
anchor particles can be attached to the tether as a separate step, with the
tether-bearing
anchor particles then added to the fluid stream containing the target
particles. In other
embodiments, a cationic polymer can be added to the fluid containing the
target particles
simultaneously with or separately from the addition of the anchor particles,
so that tether-
bearing anchor particles are not formed as a separate step. In either case, a
tether, for
example a cationic tether such as PDAC, can bind to anionic target particles
or target
particles that have been modified so as to become anionic.
[0026] The tether can attach to the anchor particle by electrostatic
attraction, hydrophobic
attraction, van der Waals forces, covalent bonding, ionic bonding, or any
other type of
bonding that allows the tether to interact with one or more anchor particles
and become
attached thereto. Certain anchor particles, for example, can acquire an
anionic charge
when placed in an aqueous solution so that a cationic tether like PDAC can
readily bind
to a plurality of such anchor particles by electrostatic interaction.
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[0027] The target particles are often not anionic themselves, so more must be
done than
simply contacting them with cationic anchor particles or anchor particles
bearing a
cationic tether; in such an embodiment, the target particles can be given a
negative charge
so that they are attracted to the cationic tethering polymers. This can be
done with an
anionic polymer, such as (acrylic acid/acrylamide) copolymers, and their
salts, which acts
as an activating agent to clump together the target particles. The activating
agent acts as a
flocculant, presenting a mass of agglomerated, negatively-charged target
particles to
interact with the cationic anchor particles or the anchor particles bearing a
cationic tether.
[0028] As used herein, the term "activation" refers to the interaction of an
activating
lo material, such as a polymer, with suspended particles in a liquid
medium, such as an
aqueous solution. An "activator polymer" can carry out this activation. In
embodiments,
high molecular weight polymers can be introduced into the particulate
dispersion as
Activator polymers, so that these polymers interact, or complex, with fine
particles. The
polymer-particle complexes interact with other similar complexes, or with
other particles,
and form agglomerates. This "activation" step can function as a pretreatment
to prepare
the surface of the fine particles for further interactions in the subsequent
phases of the
disclosed system and methods. For example, the activation step can prepare the
surface
of the fine particles to interact with other polymers that have been
rationally designed to
interact therewith in a "tethering" step. In another embodiment, activation
can be
accomplished by chemical modification of the particles. For example, oxidants
or
bases/alkalis can increase the negative surface energy of particulates, and
acids can
decrease the negative surface energy or even induce a positive surface energy
on
suspended particulates. In another embodiment, electrochemical oxidation or
reduction
processes can be used to affect the surface charge on the particles. In
another
embodiment of the activation step, hydrophobic modifiers can be used to
prepare the
surface of the fine particles for enhanced interaction with the anchor
particles. These
chemical modifications can produce activated particulates that have a higher
affinity for
anchor particles, tethers or tether-bearing anchor particles as described
below.
Negatively charged polymers can include anionic polymers can be used,
including, for
example, olefinic polymers, such as polymers made from polyacrylate,
polymethacrylate,
partially hydrolyzed polyacrylamide, and salts, esters and copolymers thereof
(such as
(sodium acrylate/acrylamide) copolymers), phosphonated polymers, sulfonated
polymers,
such as sulfonated polystyrene, 2-AMPS polymers, and salts, esters and
copolymers
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thereof In embodiments, these negatively charged polymers can act as
activators for
target particles. Positively charged polymers can include polyvinylamines,
polyallylamines, polydiallyldimethylammoniums (e.g., the chloride salt),
branched or
linear polyethyleneimine, crosslinked amines (including
epichlorohydrin/dimethylamine,
and epichlorohydrin/alkylenediamines), quaternary ammonium substituted
polymers, such
as (acrylamide/dimethylaminoethylacrylate methyl chloride quat) copolymers and
trimethylammoniummethylene- substituted polystyrene, and the like.
[0029] In embodiments, these positively charged polymers can act as tethers,
to attach to
anionic target particles or to attach to "activated" target particles that
have been made
anionic by the activation process. As tethers, these polymers attach the fine
target
particles to anchor particles, thereby forming removable complexes. In certain
embodiments, a variety of hydrophobic modifiers can prepare the surface of the
fine
particles to form complexes with low density anchor particles such as gas
bubbles. In
embodiments, the hydrophobic modifiers make the activated particles easier to
separate
by flotation methods due to hydrophobic modifiers having a lower density than
the
aqueous fluid. Hydrophobic modifiers can include fatty acids, fatty acid
salts, paraffin
wax, slack wax, paraffins, 2-ethylhexanol, 2,2,4-Trimethy1-1,3-pentanediol
monoisobutyrate, Texanol, 1,1,3-triethoxybutane, carbinols, methyl isobutyl
carbinol,
alkylamines, tallowamine, octylamine, octadecylamine, pine oil, tall oil, fuel
oil, crude oil
and the like.
2. Anchor Particles, Tethers and Activators in Water Treatment
[0030] In an embodiment, systems and methods for removing contaminants from a
fluid
stream are provided herein, comprising the steps of: (a) converting dissolved
contaminants to an insoluble form, (b) contacting the contaminants with an
anchor
particle that has an affinity for the contaminants, and (c) removing the
contaminants and
anchor particles from the fluid stream.
[0031] In an embodiment, systems and methods for removing contaminants from a
fluid
stream are provided herein, comprising the steps of: (a) contacting the
contaminants in the
fluid stream with an oxidizing agent, thereby oxidizing the contaminants
within the fluid
stream, (b) contacting the oxidized contaminants with an anchor particle that
has an
affinity for the contaminants, and (c) removing the oxidized contaminants and
anchor
particles from the fluid stream.
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[0032] In one embodiment, these systems and methods can be used to remove an
oxidizable contaminant from a fluid stream. In this embodiment, an oxidizing
agent is
initially added into the stream of water containing a target contaminant,
where the target
contaminant precipitates when it oxidizes, forming an insoluble precipitate.
The oxidizing
agent and contaminant can react with the target contaminant in an appropriate
vessel,
such as a contact vessel, a fluid container, a sufficiently long length of
tube or pipe, or the
like, such that the target contaminant in the effluent from the vessel or
conduit has reacted
with the oxidizing agent to form the insoluble precipitate. The precipitate
thus formed
becomes the target particles to be removed by use of anchor particles, using
the
methodologies described above. In an embodiment, the target particles can be
treated
initially with an anionic "activator" polymer, so that the target particles
bear a negative
charge. The activated target particles are then contacted with anchor
particles or tether-
bearing anchor particles, forming removable complexes that comprise the target
particles
aggregated with the anchor particles. The removable complexes are removed from
the
water by a solid-liquid separation operation such as filtration, inclined mesh
filtration,
flotation or clarification, taking advantage of the sinking or floating
properties of the
anchor particle. Anchor particles can be selected for their ready removability
from the
water containing the contaminant following their incorporation into the
removable
complexes. Removable complexes can float or sink, or remain suspended in a
fluid
stream, depending upon the physical properties of the component anchor
particles.
Exemplary anchor particles more dense than the fluid stream can include
materials like
cellulose (e.g., paper pulp), diatomaceous earth, rice hulls, and cellulose
acetate;
exemplary anchor particles more dense than the fluid stream can include
materials like
gas bubbles or foamed plastics. The method used for separating the removable
complexes from the fluid may depend upon the anchor particle that is selected.
Cellulose-
based removable complexes, for example, can be easily removed by a filter or
screen.
Sand-based removable complexes settle very quickly in water, making them easy
to
remove by either sedimentation or filtration. Bubble-based removable complexes
can
float to the surface, where they are removable by skimming or other mechanical
means.
[0033] The oxidant used to oxidize the target contaminant can be either
metered or added
in excess. Oxidant addition can be controlled by measuring oxidant residual or
oxidation-
reduction potential (ORP) after the contact volume. Oxidant can also be added
in excess.
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If needed, an oxidant removal step could be added in which excess oxidant is
consumed
before the product water is released from the treatment process.
[0034] In addition to oxidants, or in place of oxidants, other chemical means
of
precipitation can be used to form an insoluble precipitant from the target
contaminant. In
embodiments, the precipitant is selected so that it only precipitates with the
target
contaminant in the wastewater. Once all target contaminants have been made
into
insoluble precipitates, they must be removed from the wastewater. This can be
done by
any number of solid-liquid separation methods, from filtration to
clarification.
3. Water Treatment Using Substrate-Modifier Technologies
to [0035] Systems and methods using substrates with modifiers can be used
for removing
bacteria, dissolved metals, oil, suspended solids, and fine precipitates
(e.g., insoluble
oxidized contaminants) from water. The systems and methods for water
treatment,
described below, can be combined in any order, and with one or more of the
treatment
technologies in use. The treatment technologies, though described separately,
can be
used together in series or in parallel, and as a continuous process having
multiple steps or
treatment inputs, or as sequence of discontinuous processes. In embodiments,
substrates
for all selected treatment processes can be modified with two or more
chemically
different entities, creating a multi-functional particle for the purpose of
sequestering
multiple target contaminants.
[0036] As used herein, a substrate is a substance that provides a platform for
the
attachment of modifiers that are specific for the contaminant being removed.
For
particular treatments, the substrates are selected to provide advantageous
attachment of
modifiers for sequestering the specific contaminant. The substrate/modifier
composition
can be used as a treatment medium for removing contaminants from water. As
examples
of the substrate/modifier platform, the anchor particles system and the tether-
bearing
anchor particles system are described herein.
[0037] Particles useful as substrates (e.g., anchor particles) include
materials denser than
the fluid suspending the target contaminants, or materials that are less dense
than that
fluid. Examples of anchor particle substrates include quartz sand,
diatomaceous earth
(DE), cellulose acetate fibers, -20/+60 mesh rice hulls, -80 mesh rice hulls,
polystyrene
beads, bagasse, and the like. Substrates capable of supporting modifiers in
accordance
with these systems and methods can include organic or inorganic materials.
Exemplary
substrates, whether organic or inorganic, can be formed in any morphology,
whether
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regular or irregular, plate-shaped, flake-like, cylindrical, spherical, needle-
like, fibrous,
etc. Substrate particles can include natural materials or synthetic materials,
either as a
single substance or as a composite.
[0038] Organic substrates can include fibrous material, particulate matter,
amorphous
[0039] Natural organic substrates can comprise materials of vegetable or
animal origin.
Vegetable substrates can be predominately cellulosic, e.g., derived from
cotton, jute, flax,
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deciduous leaves from trees, shrubs and the like, leaves or needles from
coniferous plants,
and leaves from grasses. Vegetable sources can include fibers derived from the
skin or
bast surrounding the stem of a plant, such as flax, jute, kenaf, hemp, ramie,
rattan,
soybean husks, vines or banana plants. Vegetable sources can include fruits of
plants or
seeds, such as coconuts, peach pits, mango seeds, and the like. Vegetable
sources can
include the stalks or stems of a plant, such as wheat, rice, barley, bamboo,
and grasses.
Vegetable sources can include wood, wood processing products such as sawdust,
and
wood, and wood byproducts such as lignin. Animal sources of organic substrates
can
include materials from any part of a vertebrate or invertebrate animal, fish,
bird, or insect.
Such materials typically comprise proteins, e.g., animal fur, animal hair,
animal hoofs,
and the like. Animal sources can include any part of the animal's body, as
might be
produced as a waste product from animal husbandry, farming, meat production,
fish
production or the like, e.g., catgut, sinew, hoofs, cartilaginous products,
etc. Animal
sources can include the dried saliva or other excretions of insects or their
cocoons, e.g.,
silk obtained from silkworm cocoons or spider's silk. Animal sources can be
derived
from feathers of birds or scales of fish.
[0040] Inorganic substrates useful as anchor particles in accordance with
these systems
can include one or more materials such as calcium carbonate, dolomite, calcium
sulfate,
kaolin, talc, titanium dioxide, sand, diatomaceous earth, aluminum hydroxide,
silica,
other metal oxides and the like. Examples of inorganic substrates include
clays such as
attapulgite and bentonite. In embodiments, the inorganic substrate can include
vitreous
materials, such as ceramic particles, glass, fly ash and the like. The
substrates may be
solid or may be partially or completely hollow. For example, glass or ceramic
microspheres may be used as substrates. Vitreous materials such as glass or
ceramic may
also be formed as fibers to be used as substrates. Cementitious materials,
such as
gypsum, Portland cement, blast furnace cement, alumina cement, silica cement,
and the
like, can be used as substrates. Carbonaceous materials, including carbon
black, graphite,
lignite, anthracite, activated carbon, carbon fibers, carbon microparticles,
and carbon
nanoparticles, for example carbon nanotubes, can be used as substrates. In
embodiments,
inorganic materials are desirable as substrates. Modifications of substrate
materials to
enhance surface area are advantageous. For example, finely divided or granular
mineral
materials are useful. Materials that are porous with high surface area and
permeability
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are useful. Advantageous materials include zeolite, bentonite, attapulgite,
diatomaceous
earth, perlite, pumice, sand, and the like.
[0041] As disclosed herein, gas bubbles can act as a substrate for forming
anchor particles.
Advantageously, gas bubbles can form floating removable complexes, allowing
for the
removal of the removable complexes from the surface of the fluid stream. Some
other
substrates for anchor particles may also form floating removable complexes,
while others
yet will have the tendency to sink or to remain suspended in the fluid stream
(e.g., the
aqueous solution). For example, substrates such as hollow spheres, porous
materials,
foamed materials and a variety of plastics, like gas bubbles, can have a
density that is
lo lower than the aqueous stream.
a. Substrate-modifier systems for removing bacteria
[0042] In embodiments, removal of bacteria from aqueous streams can be
desirable.
Contaminating bacteria can include aerobic or anaerobic bacteria, pathogens,
and biofilm
formers. In embodiments, a substrate and a modifier can be used for removing
bacteria
from processed water and surface water to prepare such water for other
beneficial uses.
The bacterial cells may be killed, disrupted, collected, or otherwise
prevented from
proliferating.
[0043] In embodiments, a substrate, as described above, can be selected to be
modified
with a modifier, thereby producing a modified substrate as a treatment medium.
In
embodiments, the substrate is a granular material with high surface area to
offer high
permeability to flow while providing efficient contact of the water with the
modifier. In
embodiments, the modifier can be a cationic material that can be deposited on
the
substrate by covalent, ionic, hydrophobic, hydrostatic interactions, or by
saturation,
coating, or deposition from a solution. Examples of modifiers include cationic
polymers,
cationic surfactants, and cationic covalent modifiers. Cationic polymers can
include
linear or branched polyethylenimine, poly-DADMAC, epichlorohydrin/DMA
condensation polymers, amine/aldehyde condensates, chitosan, cationic
starches, styrene
maleic anhydride imide (SMAI), and the like. Cationic surfactants can include
cetyltrimethylammonium bromide (CTAB), alkyldimethylbenzyl quats,
dialkylmethylbenzylammonium quats, and the like. Cationic covalent modifiers
can
include quaternization reagents like Dow Q-188 or organosilicon quaternary
ammonium
compounds. Examples of the organosilicon quaternary ammonium compounds are 3-
trihydroxysilylpropyldimethylalkyl (C6-C22) ammonium halide, 3-
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trimethoxysilylpropyldimethylalkyl (C6-C22) ammonium halide, 3-
triethoxysilylpropyldimethylalkyl (C6-C22) ammonium halide, and the like. In
other
embodiments, the modifier can be an oxidizing compound such as potassium
permanganate, sodium hypochlorite, and sodium percarbonate. The modified
substrate
can be coated with a hydrophobic layer to cause slow release of the oxidizer.
b. Substrate-modifier systems for removing dissolved metals
[0044] In embodiments, removal of dissolved metals from aqueous streams can be
desirable. Contaminating dissolved metals can include iron, zinc, arsenic,
manganese,
calcium, magnesium, chromium, copper, strontium, barium, radium, and the like.
In
lo embodiments, a treatment medium comprising a substrate and a modifier
can be used for
removing dissolved metals from surface water and produced water to prepare
such water
for use in hydraulic fracturing. The dissolved metals may be complexed,
immobilized,
precipitated, or otherwise removed from the fluid stream.
[0045] In embodiments, a substrate, as described above, is selected to be
modified with a
modifier, thereby producing a modified substrate as a treatment medium. The
modifier is
preferably capable of being immobilized onto the substrate by mechanisms of
bonding,
complexing, or adhering. In embodiments, the modifier can be a polymer that
has an
affinity for the surface of the substrate. In embodiments, the modifier can be
applied to
the substrate in the form of a solution. In embodiments, the modifier is
insoluble in water
after it is affixed to the substrate. In embodiments, the modifier has a metal
chelating
group, and can be deposited on the substrate by covalent, ionic, hydrophobic
or
hydrostatic interactions, or by saturation, coating, or deposition from a
solution.
Examples of modifiers include compounds or polymers containing anionic chelant
functional groups selected from the list comprising phosphate, phosphonate,
xanthate,
dithiocarbamate, hydroxamate, carboxylate, sulfate, and sulfide. Examples of
modifiers
include fatty acids, fatty amides, and vinyl polymers with the above listed
chelant groups.
Examples of modifiers based on vinyl polymers include comonomers of
vinylphosphonic
acid, vinylidenediphosphonic acid, 2-acrylamido-2-methylpropane sulfonic acid
(2-
AMPS), acrylamide-N-hydroxamic acids, itaconic acid, maleic acid, and salts
thereof In
embodiments, inorganic salts such as ferric chloride tetrahydrate can be used
as
modifiers.
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c. Substrate-modifier systems for removing suspended solids
[0046] Suspended solids are often removed from fluid streams by filtration or
sedimentation. In the case of finely divided solids or colloids, however,
sedimentation is
slow and filtration can be difficult. While filtration technologies, for
example, sand
filtration, is known in the art to remove finely divided suspended solids from
liquids,
these contaminants have low affinity for the medium, so their removal can be
inefficient.
Conventional filtration methods are also subject to plugging, resulting in a
decreased
throughput or an elevated pressure. The substrate-modifier system enables the
collection
of fine particulates into a form that is more easily filtered, resulting in
more efficient
removal of the fine particulates.
[0047] In hydraulic fracturing, suspended solids in the frac fluid can cause
formation
damage, plugging and lost production. Hence, the removal of such substances
from the
frac fluid is desirable. Suspended solids can include materials like clays,
weighting
agents, barite, drilling muds, silt, and the like. In embodiments, a treatment
medium
comprising a substrate and a modifier can be used for removing suspended
solids from
surface water and produced water more rapidly and efficiently than currently-
practiced
technologies, to prepare such water for use in hydraulic fracturing.
[0048] In embodiments, a substrate, as described above, is selected to be
modified with a
modifier, thereby producing a modified substrate as a treatment medium. In
embodiments, the substrate is a granular material with high surface area to
offer high
permeability to flow while providing efficient contact of the water with the
modifier.
Modifiers useful in the removal of suspended solids according to these systems
and
methods include cationic polymers, cationic surfactants and cationic covalent
modifiers.
Examples of cationic polymers include linear or branched polyethylenimine,
poly-
DADMAC, epichlorohydrin/DMA condensation polymers, amine/aldehyde condensates,
chitosan, cationic starches, styrene maleic anhydride imide (SMAI), and the
like.
Examples of cationic surfactants include cetyltrimethylammonium bromide
(CTAB),
alkyldimethylbenzyl quats, dialkylmethylbenzylammonium quats, and the like.
Examples
of cationic covalent modifiers include quaternization reagents like Dow Q-188
or
organosilicon quaternary ammonium compounds. Examples of the organosilicon
quaternary ammonium compounds are 3-trihydroxysilylpropyldimethylalkyl (C6-
C22)
ammonium halide, 3-trimethoxysilylpropyldimethylalkyl (C6-C22) ammonium
halide, 3-
triethoxysilylpropyldimethylalkyl (C6-C22) ammonium halide, and the like.
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d. Substrate-modifier systems for removing hardness
[0049] Hardness ions like Ca, Mg, Ba, Fe, Sr, and the like, can cause scaling
and plugging
of equipment and producing zones of the petroleum formation as a result of
hydraulic
fracturing operations. These multivalent cations also cause precipitation or
higher dose
requirements of certain additives needed in fracturing, for example friction
reducing
agents. For these reasons, elevated hardness is undesirable in frac water.
Typical
concentrations of hardness ions in fresh water sources are in the range of 20-
250 mg/L as
CaCO3. Flowback water from a fracturing operation can contain much higher
concentrations of hardness ions, up to 30,000 mg/L as CaCO3, as a result of
contacting
underground sources of such materials.
[0050] Conventional treatments for softening water (i.e., removing hardness
ions) include
ion exchange, distillation, reverse osmosis (RO) desalination, and lime
softening, and
each has known disadvantages. Ion exchange requires periodic regeneration with
brine
and this corrosive brine is a handling and disposal issue. Distillation and RO
are energy-
and equipment-intensive. Lime softening is sometimes practiced on a large
scale in
municipal water treatment systems, but the process generates a lime sludge
that is
difficult to dewater and manage. To avoid some or all of these disadvantages,
the
systems and methods disclosed herein utilize a two-step process: 1)
precipitation of
hardness ions, and 2) removal of the precipitate with a substrate-modifier
system.
[0051] In embodiments, the first step can involve precipitation of hardness
ions by using
an alkali source such as sodium carbonate, sodium bicarbonate, or sodium
hydroxide.
Treatment with the alkali causes formation of calcium carbonate crystals. The
precipitation step can remove a variety of metals that contribute to hardness,
including
Ca, Mg, Ba, Sr, Fe, Cu, Ag, Ni, Cd, Cr, Zn, and Pb ions as precipitated
carbonates or
hydroxides, and the precipitated solids facilitate removal of other suspended
solids, oil
and bacteria. All of these solids are collected as a sludge and the resulting
water is
clarified. After the precipitation, the CaCO3 particles need to be removed
from the water
to complete the treatment.
[0052] Removing the CaCO3 particles can take place by contacting them with a
substrate-
modifier system. Advantageously, a mineral substrate can be used, with a size
between
0.01-5 mm in diameter. The substrate particles can be modified with polymers
such as
linear or branched polyethylenimine, poly-DADMAC, epichlorohydrin/DMA
condensation polymers, amine/aldehyde condensates, chitosan, cationic
starches, and
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styrene maleic anhydride imide (SMAI). In other embodiments, the modifier
polymers
can be anionic types such as acrylamide/acrylate copolymers or carboxymethyl
cellulose;
or nonionic types such as polyacrylamide or dextran.
e. Substrate-modifier systems for removing oil and organics
[0053] In embodiments, a treatment medium comprising a substrate and a
modifier can be
used for removing oil, dissolved organic compounds, and suspended organic
compounds
from water. In hydraulic fracturing, suspended or emulsified oil in the frac
fluid can cause
formation damage, plugging, microbial growth, and elevated demands for
additive
chemicals. Hence the removal of oil from frac fluid components is desirable.
Contaminating oil in frac fluids can include oil from the petroleum reservoir,
lubricants,
or drilling fluid additives.
[0054] In embodiments, a substrate, as described above, is selected to be
modified with a
modifier, thereby producing a modified substrate as a treatment medium. In
embodiments, the substrate is a granular material with high surface area to
offer high
permeability to flow while providing efficient contact of the water with the
modifier. In
embodiments, the modifier can be a hydrophobic cationic material that can be
deposited
on the substrate by covalent or ionic bonding. The modifier can be applied by
saturation,
coating, or deposition from a solution. Examples of modifiers include cationic
polymers
and cationic surfactants. In embodiments, the modifier can be an organosilicon
quaternary ammonium compound. Examples of the organosilicon quaternary
ammonium
compounds are 3-trihydroxysilylpropyldimethylalkyl (C6-C22) ammonium halide, 3-
trimethoxysilylpropyldimethylalkyl (C6-C22) ammonium halide, 3-
triethoxysilylpropyldimethylalkyl (C6-C22) ammonium halide, and the like.
4. Oxidizing Agent Technologies
[0055] Systems and methods that provide oxidizing agents as part of a
treatment system
can involve four steps: (1) oxidizing the contaminant in the aqueous stream;
(2) adding a
treatment medium (i.e., a modified substrate) to collect the oxidized
contaminants; (3)
removing the oxidized particles from the aqueous stream; and (4) treating the
aqueous
stream to remove residual oxidants and other processing materials. Processes
in
accordance with these systems and methods can take advantage of the different
solubilities of reduced and oxidized species of contaminants.
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[0056] Oxidants suitable for use in accordance with these systems and methods
include, in
embodiments, common oxidants such as ozone, oxygen, chlorine, chlorite,
hypochlorite,
permanganate, hydrogen peroxide, organic peroxides, persulfate, perborate, N-
halogenated hydantoin, nitric acid, nitrate salts, and the like. In
embodiments, sodium
[0057] The oxidizing agent can be added to the system by different delivery
mechanisms.
For example, aqueous solutions of oxidants can be fed by pumping a feed
solution at
constant volumetric rate or on demand as determined by oxidation-reduction
potential
(ORP) or other detection scheme.
deposit themselves onto the flocs, and after sufficient bubble attachment the
bubbles
make the flocs buoyant and float.
[0059] In certain embodiments, the oxidant can be delivered in the form of a
gas stream or
bubbles, such as ozone, air, chlorine, and the like. The contact of the
oxidant gas with the
25 water stream can be facilitated by a sparger or diffuser, in which case
the oxidant gas can
serve as the oxidant, the anchor particle, or both. Alternatively, the oxidant
can be
delivered in a solid form such as tablets, granules, or a suspension. The
delivery of the
oxidant can be metered by limited solubility of a solid dosage form, or by
controlled/delayed release of an encapsulated form. In other embodiments, the
oxidation
30 can be accomplished by means of an electrochemical method, such as
passing the water
through a reactor equipped with electrodes that deliver an applied voltage.
The electrodes
can be designed such that a sacrificial metal dissolves into the solution upon
application
of a voltage. Such systems are known in the art as electrocoagulation (EC)
systems. In
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embodiments, the electrode material can be aluminum which dissolves upon
application
of voltage to release aluminum ions into solution.
[0060] As described above, for certain oxidized contaminants such as ferric
hydroxide,
filtration based on particle size is not effective. Accordingly, in
embodiments, treatment
media having a specific affinity for ferric hydroxide can be provided. In
certain
embodiments, the treatment media can include media containing the anchor
particles,
tethers and activators as described above. In embodiments, the anchor
particles are used
together with tether polymers to produce modified substrates that can collect
the
precipitate particles. These systems and methods using anchor particles,
tether particles
and optionally activator particles form removable complexes from the
precipitated ferric
hydroxide target particles, facilitating their removal.
B. OIL INDUSTRY APPLICATIONS
[0061] In embodiments, the systems and methods disclosed herein can be
utilized for
removing specific contaminants from oil industry wastewater. In embodiments,
targeted
sorbents can be used that have specific affinity for the contaminant in
question. The
targeted treatment media can be designed by providing a supportive substrate
modified
with one or more combinations of functional components. The substrate can act
as a solid
support, sorbent, reaction template and a coalescer. In embodiments, the
substrate can
comprise finely divided clays or minerals, porous granular minerals, high
surface area
suspensions, or biomass. In other embodiments, the substrate can be introduced
in fluid
form such as an immiscible liquid, an emulsion, or a soluble additive. The
substrate can
be prepared as a solid form, such as granular, powdered, fibrous, membrane,
microparticle, or coating to be contacted with fluid streams bearing oil
industry
wastewater. In embodiments, the substrate can be pre-treated with hydrophilic
or
hydrophobic polymers.
[0062] In embodiments, the substrate can be modified by contacting a solution
of the
modifier with the substrate, either in a flow-through setting or a batch
mixture. The
modifier can be placed onto the substrate by chemical bonding, for example
covalent,
ionic, hydrophobic, or chelation type bonds. In another embodiment, the
modifier can be
placed onto the substrate by coating or saturation of the substrate with the
modifier. One
method of coating or saturating the substrate with modifier is to apply a
liquid solution of
modifier onto the substrate. In either method of modification, after
contacting the
substrate with the solution of modifier, the residual water or other solvent
can be
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evaporated to leave a residue of modifier on the surface of the substrate. In
embodiments,
the substrate can be treated with a solution or suspension of the modifier in
a fluid
medium, where the modifier has an affinity for the substrate causing
deposition onto the
substrate. The residue can be a monolayer, a coating, a partial layer, a
filling, or a
complex.
[0063] In embodiments, the substrate bears modifier compounds that add the
specific
functionality to the targeted sorbent. For example, cationic modifiers can be
used to
remove anionic contaminants by charge attraction, aromatic modifiers can be
used to
remove aromatic contaminants by pi-pi stacking, chelating modifiers can be
used to target
metals, etc. As examples of metal chelants, compounds such as carboxylates,
phosphonates, sulfonates, phenolics, hydroxamates, xanthates,
dithiocarbamates, thiols,
polypeptides, amine carboxylate, thiourea, crown ether, thiacrown ether,
phytic acid, and
cyclodextrin can be used. In embodiments, modifiers can be multifunctional. As
an
example, a cationic aromatic compound used as a modifier can absorb anionic
and
aromatic contaminants at the same time.
[0064] In embodiments, modifiers can be designed having high affinity for
specific
contaminants. As would be understood by those of skill in the art,
combinatorial methods
can be used to identify appropriate modifiers. By using combinatorial ligand
libraries of
metal ion complexes, for example, ligands can be selected for binding specific
metal ions.
In embodiments, ligands for binding metals can be selected whose bonds are
reversible
under certain conditions, such as by adjusting pH. Certain polypeptides, for
example,
demonstrate this behavior. Under these circumstances, metal ion chelation, for
example
as carried out by polypeptides, can be reversed by pH adjustment so that the
metals can
be reclaimed after being removed from the wastewater.
[0065] In embodiments, specifically selected or designed polypeptides and
proteins can be
used as modifiers for forming a targeted sorbent in accordance with these
systems and
methods. For example, metallothioneins (MTs) can be used as modifiers to be
affixed to
a substrate for sequestering metal ions. MTs are a superfamily of low
molecular weight
(MW ¨ 3500 to 14000 daltons) cysteine-rich polypeptides and proteins found in
biological systems (e.g., animals, plants and fungi), where their purpose is
to regulate the
intracellular supply of essential heavy metals like zinc, selenium and copper
ions, and to
protect cells from the deleterious effects of exposure to excessive amounts of
physiological heavy metals or exposure to xenobiotic metals (such as cadmium,
mercury,
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silver, arsenic, lead, platinum) heavy metals. Typically MTs lack the aromatic
amino
acids phenylalanine and tyrosine. MTs bind these metals through the sulfhydryl
groups
of their cysteine (Cys) residues, with certain metal preferences in a given
structure based
on the distribution of these Cys residues. Due to their primary, secondary,
tertiary and
quaternary structures, these proteins have high ion binding selectivity. Metal
ions in MT
molecules can be competitively displaced by other metal ions that have
stronger affinities
to MT. Other peptides such as phytocheletins (PCs) (oligomers of glutathione)
have a
similar metal chelating function. MTs and PCs, or analogues thereof, can be
covalently
attached to hydrophilically modified supportive materials, such as mineral
particles or
lo natural plant fibers. The resulting functionalized materials can be used
to remove specific
selenium and zinc ions from refinery wastewater streams. In embodiments, other
naturally derived or synthetically produced agents having heavy metal binding
capabilities can be used as modifiers to form a targeted sorbent useful for
specific heavy
metals in refinery wastewater streams.
[0066] Other metal scavengers, for example, non-polymeric compounds, can be
used as
modifiers for forming a targeted sorbent in accordance with these systems and
methods.
In embodiments, small molecules can be used to sequester metal ions. As an
example,
taurine (2-aminoethanesulfonic acid), a naturally-occurring sulfonic acid
derived from
cysteine in biological systems, can complex with zinc, and may bind with other
heavy
metals such as lead and cadmium. It has no affinity for calcium or magnesium
ions,
though. A modifier like taurine would permit a targeted sorbent to have
selective metal
ion binding capability.
[0067] In embodiments, the modified substrate can be used as a treatment agent
for
removal of undesirable compounds from petroleum industry wastewaters. In one
embodiment, the treatment agent can be a granular filter media that is
enclosed in a
pressure vessel, for example to allow a certain contact time with the process
fluid such as
wastewater. In another embodiment, the treatment agent can be a finely divided
material
that is contacted with a process stream with the treatment agent (complexed
with
contaminants) being allowed to separate by sedimentation, centrifugation, or
filtration. In
embodiments, the treatment agent can be formed into fibrous or loose fill
material that is
contacted with the process stream. In embodiments, the treatment agent can be
a coating
or membrane that removes contaminants from liquids that pass through or pass
over the
coating or membrane. The contaminants that complex with the treatment agent
can then
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be removed from the process stream and disposed, recycled, incinerated or
otherwise
treated to render the contaminants immobilized or detoxified.
C. FRAC WATER
[0068] In embodiments, the systems and methods for treating wastewater can be
used for
treating water for use in hydraulic fracturing. These systems and methods,
while
applicable to treating any water supply, are particularly advantageous for
treating frac
flowback water. For example, in hydraulic fracturing, dissolved metals in the
frac fluid
can cause formation damage, plugging, lost production and elevated demand for
additive
chemicals. Hence the removal of these dissolved metals from the frac fluid is
desirable.
In addition to the general purification problems for frac water, there is
typically a high
iron concentration that can be as high as 200-300 ppm; this should desirably
be reduced
to a concentration < 5 ppm if the water is to be suitable for use in hydraulic
fracturing.
[0069] As would be understood by those of ordinary skill in the art, different
sets of
treatment systems may be required for treating surface water (which tends to
contain
lower levels of contaminants and fewer kinds of contaminants) than for
treating processed
water. Arrangements of the individual treatment systems is modular, and can be
organized in a circuit containing any number of filtration components to
provide a
sequential filtration pathway.
[0070] In embodiments, the oxidizing agent technologies previously described
can be
advantageously applied to removing undesirable ions from frac water. For
example,
ferrous and ferric ions as found in frac water, have different solubilities in
water. At the
pH of frac flowback water, for example between pH 4.0 and pH 7.0, Fe +++ is
much less
soluble than Fe, forming a colloidal precipitate of Fe(OH)3. This principle
allows the
iron in frac water to be rendered insoluble by oxidization, so that it can be
removed.
However, it is understood that the settling and coagulation of precipitated
Fe(OH)3 are
very slow, especially in a continuous flow through process. The finely
dispersed Fe(OH)3
particles especially in colloidal forms are difficult to remove by filtration
through
conventional media like sand filters, zeolite filters, diatomaceous earth
filters, filter cloth,
filter screens, etc. Hence, systems and methods for removal of ferric
hydroxide and other
oxidized species from fluid streams are desirably incorporated in a process
for treating
fluid streams such as frac water.
[0071] In more detail, the systems and methods as described herein can treat
fluid streams
such as frac water to remove: 1) dissolved metals such as Fe2+; 2) finely
dispersed
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insoluble oxidized metal particles such as Fe3+; and 3) finely dispersed
insoluble oxidized
metal particles that have had their surface contaminated with organic
material.
1. Removal of dissolved metals from frac water
[0072] For the removal of only dissolved metal (e.g. ferrous iron), a suitable
substrate
(e.g. diatomaceous earth) and an oxidizing agent (e.g. hydrogen peroxide) can
be added to
the aqueous stream (e.g. frac flowback water) either simultaneously or in
sequence. In
this system, the oxidizing agent can react with the dissolved metal,
precipitating finely
dispersed insoluble particles of the oxidized metal species from the aqueous
stream. In
embodiments, an adjustment of the pH may be necessary subsequent to the
oxidation
step, to facilitate the precipitation of the insoluble species. Following the
formation of the
precipitate of the oxidized metal in particulate form, a modifier can be added
to the
solution, such as a flocculant (e.g. polyacrylamide ¨ polyacrylic acid
copolymer), that
forms agglomerates of the finely dispersed oxidized metal particles. In an
embodiment,
the flocculated agglomerates coalesce around a substrate such as the
diatomaceous earth
or any other suitable substrate. These flocculated agglomerates can then be
removed by
conventional mechanical separation techniques. This technique can be performed
either
in a batch process or in a continuous flow through process, and it can be
combined with
other treatment methods to remove, for example, remove residual oxidants and
other
processing materials.
2. Removal of dispersed metal oxide particulate matter without
additional inorganic or organic contamination
[0073] When no dissolved metals are present, but only finely dispersed metal
oxide
particles, the oxidation and pH adjustment steps described above are not
necessary. In this
case the substrate and modifier can be added simultaneously or in sequence,
and the
resulting flocculated agglomerates can then be removed by conventional
mechanical
separation techniques. This technique can be performed either in a batch
process or in a
continuous flow through process.
3. Removal of dispersed metal oxide particulate matter with organic or
inorganic contamination
[0074] Without being bound by theory, it is understood that deposits of
hydrocarbon
material, biological material, inorganic material (metal oxides, hydroxides
and sulfides),
or combinations thereof can form in pipes, equipment and formations used in
hydrocarbon recovery, including produced water injection wells. These
deposits, known
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in the art as "schmoo," can nucleate around particulate matter found in
equipment or
wells, for example single particles such as proppants, formation sand, fines
or other
precipitants. The solid nucleating material can become oil-wet from a coating
of surface-
active chemicals like corrosion inhibitors that are used in the equipment or
the wells.
Once the solid material is oil-wet, it can attract a layer of hydrocarbons
that can congeal
into a sticky agglomeration that adheres to surfaces. Large agglomerates can
settle out in
tank bottoms, and smaller agglomerates can be transported through pipes or
into
equipment or into the formation, causing fouling.
[0075] When the surface of finely dispersed oxidized metal particles has been
lo contaminated (e.g. with organic material, schmoo, or the like), adding a
modifier as
described above may not result in effective flocculation of the dispersed
oxidized metal
particles. In this case additional treatment is needed for successful removal
of finely
dispersed insoluble particles. In one embodiment where the aqueous stream
contains
finely dispersed ferric iron particles contaminated with organic material, the
same
procedure is used as was described for the removal of ferric iron particles
without organic
contamination. As an additional step, though, ferrous or ferric iron is also
added to the
fluid stream. This additional treatment step allows for the modifier to
properly
agglomerate the suspended insoluble oxidized metal particles, enabling their
removal
from the aqueous stream. In embodiments, further treatment steps may be taken
as
appropriate, for example adjusting the pH of the fluid stream, or treating the
fluid stream
with a surfactant that interacts with the organic-coated particles, thereby
rendering their
surfaces cationic or anionic so that they interact better with the modifier
and/or substrate.
[0076] It may be envisioned that other types of contamination besides organic
species may
render the modifier-substrate system ineffective for removing finely dispersed
metal
particles from fluid streams. In such situations, additional treatment steps
can be taken to
deal with such contaminants as appropriate, for example treating the fluid
stream with an
acid or base (as appropriate) before the addition of the substrate and the
addition of the
oxidizing agent but before the addition of the modifier.
4. Removal of resistant iron species
[0077] In certain cases, iron in wastewater can be particularly resistant to
removal
treatments. As an example, flowback water from various oil shale wells can
demonstrate
this resistance. Of note, certain fracturing operations for oil shale wells
use
predominately guar-based fluid in each of their fracking stages, up to 100%
guar-based
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fluid. Without being bound by theory, it is possible that residual guar
fragments can
complex with the dissolved iron from the formation waters, making the iron
harder to
remove by chemical means. In support of this, our laboratory tests, set forth
in the
Examples below, indicate that ferrous iron in the presence of broken guar gel
does not
precipitate immediately after oxidization and neutralization.
[0078] In embodiments, compounds having high affinity for iron, such as sodium
phosphate, can cause iron to precipitate when oxidation and neutralization
alone are not
sufficient to effect precipitation. The phosphate can target the iron and form
insoluble
iron phosphate. Phosphoric acid and sodium phosphate, for example, can cause
chelated-
iron precipitation. Other potential candidates include polyphosphates,
silicates, sulfides,
and sulfates. Accordingly, addition of such iron-binding compounds can assist
with
removal of resistant iron species, especially when complexation with guar
fragments is
thought to explain the resistant behavior.
5. Exemplary water treatment system
[0079] The Figure shows an embodiment of a water treatment system 100 using
flotation
to separate contaminants from frac water. As shown in the Figure, untreated
water 102,
such as flowback water or produced water, taken from its source 104 and is
injected at a
chemical injection point 108 with an oxidant formulation 110, comprising, for
example
oxidant and buffer, to precipitate the targeted contaminants in the untreated
water 102.
The oxidant formulation 110 may also comprise anchor particles less dense than
the
ambient fluid stream, or anchor particle precursors that produce anchor
particles less
dense than the ambient fluid stream. Examples of less-dense anchor particles
include oil
droplets or air bubbles; an anchor particle precursor can be an oxygen-
releasing material
like hydrogen peroxide that releases bubbles that then act as anchor
particles. The fluid
then passes to a mixing zone 112, where mixing of the fluid stream can allow
the
contaminants to fully precipitate and potentially to break the bubbles or
droplets into
smaller-sized pieces. Then an activator polymer 114 is added at a second
chemical
injection point 118 gather the contaminants together and to provide a place
for the oil or
air to collect. The fluid stream then passes to a second mixing zone 120,
where the
flocculation of the contaminants develops more fully, and where the
flocculated
contaminants can attach to the anchor particles to form removable complexes.
The fluid
stream then enters a separation zone 122, where the removable complexes float
to the top,
where they can be drawn off as sludge for disposal 124 and the treated water
is drawn off
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the bottom and sent to an appropriate storage or recycling facility 128. The
second
mixing zone 120 should have fairly low shear in order to allow flocs to
develop and
attach to the anchor particles to form removable complexes, while the first
mixing zone
112 can be of higher shear. In a typical process, the mixing in the first
mixing zone 112
need only last between about 1-5 seconds, while the mixing in the second
mixing zone
120 should be at least 20 seconds or more. Flotation promoters such as the
hydrophobic
modifiers disclosed above (for example, fatty acids, fatty acid salts,
paraffin wax, slack
wax, paraffins, 2-ethylhexanol, 2,2,4-Trimethy1-1,3-pentanediol
monoisobutyrate,
Texanol, 1,1,3-triethoxybutane, carbinols, methyl isobutyl carbinol,
alkylamines,
tallowamine, octylamine, octadecylamine, pine oil, tall oil, fuel oil, crude
oil, and the
like) can be added in either chemical injection point.
EQUIVALENTS
[0080] As described herein, embodiments provide an overall understanding of
the
principles, structure, function, manufacture, and/or use of the systems and
methods
disclosed herein, and further disclosed in the examples provided below. Those
skilled in
the art will appreciate that the materials and methods specifically described
herein are
non-limiting embodiments. The features illustrated or described in connection
with one
embodiment may be combined with features of other embodiments. Such
modifications
and variations are intended to be included within the scope of the present
invention. As
well, one skilled in the art will appreciate further features and advantages
of the invention
based on the above-described embodiments. For example, while the embodiments
disclosed herein have been applied to water treatment before use in hydraulic
fracturing
formations, it is understood that certain embodiments can be applied to the
treatment of
water or other fluid streams produced by or used in other processes, e.g.,
drinking water
purification, irrigation water purification, treatment of water from
agricultural runoff,
treatment of water from industrial processes, treatment of effluents from
municipal water
treatment systems, and the like. The systems and methods disclosed herein,
while
advantageous for removing iron from water supplies such as frac water, can
also be used
for removal of other water contaminants, such as manganese, sulfur, hydrogen
sulfide,
mercaptans, and some organic compounds. As an additional benefit, the systems
and
methods disclosed herein can disinfect a water supply, by decreasing the
concentration of
viable bacteria and other pathogens therein. Accordingly, the invention is not
to be
limited by what has been particularly shown and described, but rather is to be
delimited
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by the scope of the claims. All publications and references cited herein are
expressly
incorporated herein by reference in their entirety. The words "a" and "an" are
replaceable
by the phrase "one or more."
EXAMPLES
[0081] Materials
[0082] The following materials were used in the Examples below:
Zeolite (8/40 mesh) was supplied by Bear River Zeolite
Lupasol G20 was supplied by BASF
Styrene maleic anhydride imide (SMAI 1000) was supplied by Sartomer (now
Cray Valley)
Anionic flocculant (Magnafloc LT30) was supplied by Ciba
Potassium permanganate, poly-DADMAC, lignin, phosphoric acid, urea, sand,
sodium hydroxide, and sodium carbonate were supplied by Sigma Aldrich
Aldrich +50/-70 mesh sand, Celite 545 diatomaceous earth, Rice Hull Specialty
products -80 mesh rice hull and -20/+80 mesh rice hull, bagasse fibers, Poly-
fil
bean bag filler
[0083] Example 1: Preparation of PDAC modified Cellulose Acetate anchor
particles
[0084] A 0.1% solution was made by dissolving 20% PDAC in water. Cellulose
acetate
was suspended in 11 solution of 0.1% PDAC for 10 min while stirring the
suspension.
The solution was then drained and the substrate dried at 100C for ¨ 30 min.
[0085] Example 2: Preparation of PDAC modified anchor particles
[0086] A 1% solution was made by dissolving 20% PDAC in water. The anchor
particles
were covered in this solution and the solution was stirred for 10-15 minutes.
The solution
was decanted away.
[0087] Example 3: Iron hydroxide suspension preparation
[0088] A solution of iron (III) chloride with 500 ppm of iron was made in tap
water.
1.168 g of FeC13 were added to tap water such that the total solution mass is
799.98g.
Iron chloride solutions of lower concentration were made by diluting this
stock solution.
Once the desired solution concentration of iron chloride was made, drops of
sodium
hydroxide were added until the pH of the solution was between 6 and 8. At this
time, a
precipitate would be visible, ferric hydroxide.
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[0089] Example 4: Flocculant Solution preparation (0.1% solution)
[0090] 0.0499 g of Magnafloc LT-30 was placed in beaker, and 49.927 g of tap
water was
added. The solution was mixed by hand with a stir rod.
[0091] Example 5: Qualitative capture properties of modified anchors
[0092] A series of experiments were performed investigating the feasibility of
several
modified substrates. Each sample was prepared in a 40 mL sample vial using 30
grams of
100 ppm iron in the form of ferric chloride. The pH of each sample was raised
to neutral
with 1 molar sodium hydroxide (about 4-5 drops). A modified substrate of
Examples 1 or
2 and 0.120 mL of 0.1% Magnafloc LT-30 (Example 4) were added to each sample,
sometimes with the flocculant being added first, sometimes with the substrate
added first.
Mixing was performed by gently inverting the capped sample vial several times
for about
¨ 30 seconds. Results are shown in Table 1 below.
Table 1
Modified Material Mass LT-30 Addition Settling Rate (inches per
(g) minute)
None N/A N/A 0.017
None N/A First 0.063
None N/A First 1.3
Sand .585 First 0.36
Sand .571 Second 0.28
CA .232 Second Fibers do not settle
DE .297 First 0.31
DE .689 Second 0.023
Rice Hull -20/+80 0.593 rate t .070
Rice Hull -80 0.470 Second .24
CA .224 First Fibers do not settle
CA .038 First Fibers do not settle
Polystyrene beads .027 First Poor
Bagasse .8 First Poor
Unmodified Refined 0.738 None 0.32
Hardwood Pulp
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Modified Material Mass LT-30 Addition Settling Rate (inches per
(g) minute)
Unmodified Refined .738 Second Fibers do not settle
Hardwood Pulp
Unmodified Refined .112 Second Fibers do not settle
Hardwood Pulp
1.05% DE .302 First .36
suspension
1.05% DE 1.202 First .86
suspension
1.05% DE 1.223 Second .91
suspension
Unmodified Sand .113 Second 1.62
[0093] Example 6: Varying ferric hydroxide concentration and the effect on
settling
[0094] Five 100 mL beakers were filled with 50 grams of different
concentrations of iron
chloride suspension: 5 ppm of iron, 10 ppm, 30 ppm, 100 ppm and 300 ppm. Each
beaker was then treated with 1 molar sodium hydroxide, which was added
dropwise until
the pH of the solution was between 6 and 8. Precipitates were observed in all
the beakers
except the beaker with 5 ppm of iron, which appeared to be a pale yellow
transparent
solution. The beakers with 100 and 300 ppm iron settled completely, with the
more
concentrated beaker mostly settling within 1.5 minutes after mixing. The 30
ppm iron
beaker did not settle as quickly, and 3 minutes after mixing there are still
many particles
in the bulk solution.
[0095] To each of the beakers, 0.200 mL of 0.1% Magnafloc LT-30 was added and
the
beakers were stirred for 1 minute. No change was observed in the beaker with 5
ppm of
iron. The other beakers showed an increase in average particle size as the
original
particles agglomerated together. Settling rate was observed to increase with
increasing
iron concentration. Results are described in Table 2.
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Table 2
Iron Concentration (ppm) Settling behavior after addition of LT-30
No visible precipitate
Particles appear slightly larger, most particles still in
suspension after 2 minutes of settling
30 Clumping of particles observed, about 50% still in
suspension after 2 minutes of settling
100 Particle size increases upon adding the flocculant.
Most of the floc settles in the first 20 seconds, with
all settled after 90 seconds
300 Same as 100 ppm, excepting that the final clusters
appear larger
[0096] Each beaker then undergoes the following process. It is mixed for 15
seconds, and
then 0.05 g of PDAC modified sand of Example 2 is added and the beaker is
mixed for
5 another 15 seconds. The resulting mixtures all settle more compactly.
Results are
described in Table 3.
Table 3
Iron Concentration (ppm) Settling behavior after addition of PDAC modified
sand
5 Solution still yellow. Sand at bottom is yellow-
orange
10 Most material settles out instantly, few clusters
remain in
bulk
30 Faster settling rate, more compact bed, sand has not
grabbed everything
100 It takes 20-30 seconds for all the material to settle in
more condensed area
300 Precipitate falls more condensed. Some of the larger
flocs seem to have been broken apart.
[0097] Example 7: Ferric hydroxide suspension of 100 mg Fe/L
[0098] A ferric chloride solution of about 500 mg Fe per liter was made using
tap water
10 and 97% reagent
grade ferric chloride from Aldrich. A sample from this stock iron
solution was then diluted with tap water until the iron concentration was
about 100 mg Fe
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per liter (about 4 g of water per 1 g of stock solution). Drops of 1-5 M NaOH
were then
added to the sample until the pH of the solution went above 6. At that point,
a fine
precipitate of reddish-orange particles was observed, ferric hydroxide
particles.
[0099] Example 8: Measurement of iron concentration
[00100] Iron concentration was measured using a Hach DR2700 to perform the
FerroVer method, which uses UV absorbance of 10 mL samples to calculate the
amount
of iron in solution. A sample of the iron solution being measured was diluted
so that its
estimated iron concentration was in range for the DR2700 to accurately measure
(between
0 and 3 mg Fe/L). The solution concentration could then be calculated by
multiplying by
io the dilution ratio.
Example 9: Preparation of a 0.1% Flocculant Solution
[00101] 0.0411 g of Magnafloc LT-30 was placed in beaker, and 39.667 g
of tap
water was added. The solution was mixed with a stir bar on a stir plate for
about two
hours on the lowest settling until all precipitate and bubbles were gone.
[00102] Example 10: Preparation of cellulose slurry
[00103] Hardwood cellulose pulp (either refined or unrefined) at about
4-6% solids
was added to a 250 mL beaker with about 100 g of tap water so that the
cellulose solids
content of the final concentration is about 0.2%. The beaker was then mixed by
hand for
about 30 seconds.
[00104] Example 11: Sequestration of iron by cellulose
[00105] An example of this process is the removal of ferric hydroxide
from water
by using hardwood cellulose pulp and a partially hydrogenated polyacrylamide
Magnafloc LT-30.
[00106] About 400 mL of a 100 mg Fe/L ferric hydroxide suspension of
Example 7
was prepared in a 600 mL beaker. As this beaker was mixed, about 100 mL of an
about
0.2% cellulose slurry of Example 10 was added to the beaker and stirred for
about a
minute (Note that the iron concentration at this point is approximately 80 mg
Fe/L). Then
about 1.5 g of a 0.1% flocculant solution was added to the beaker and the
beaker was
stirred for about a minute. After this time, the beaker was poured through a
70 mesh
(0.212 mm) screen. The filtrate was then sampled and the iron concentration
measured
by Example 8 to find that the iron concentration was between 0.5 and 2 mg
Fe/L.
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[00107] Example 12: Comparison of order of addition of cellulose and
flocculant
on iron sequestration by cellulose
[00108] Two experiments using the methods of Example 11 were performed
using
refined hardwood pulp. In one of these, the order of addition of Magnafloc LT-
30 and the
cellulose slurry was reversed. Table 4 below shows that both removed similar
amounts of
iron. When cellulose was added first, the iron ultimately was evenly
distributed along the
fibers. When cellulose was added second, the iron was clumped in flocs that
were
unevenly distributed among the cellulose fibers.
Table 4
Order of addition Iron concentration Iron concentration of % Iron removal
of Feed (mg Fe/L) Filtrate (mg Fe/L)
Cellulose, LT-30 77 .99 99
LT-30, cellulose 81 .96 99
[00109] Two experiments using the methods of Example 11 were performed. In
one of these experiments, no cellulose was added. In another of these
experiments, no
LT-30 was added. The resulting iron removals indicate that the combination of
cellulose
and LT-30 is necessary to obtain the greatest percentage removal. These
results are
summarized in Table 5.
Table 5
Additives Iron concentration Iron concentration % Iron removal
of Feed (mg Fe/L) of Filtrate (mg Fe/L)
Cellulose, LT-30 77 .99 99
LT-30 80 63 21
Cellulose 100 27 73
[00110] Example 13: Refined versus unrefined hardwood
[00111] Four experiments using the methods of Example 11 were
performed. Two
of these were using refined hardwood and two of these were using unrefined
hardwood
pulp. Of each of the pairs, two different concentrations of pulp slurry were
used. Table 6
shows the results of these experiments. These experiments show that, down to a
ratio of
cellulose to iron of about 1.6 to 1.7, the removal of iron by refined and
unrefined
hardwood pulp is almost identical.
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Table 6
Cellulose Pulp Iron Iron concentration of % Iron
added concentration of Filtrate (mg Fe/L) removal
Feed (mg Fe/L)
451 mg/L, refined 77 .99 99
131 mg/L, refined 79 2.72 97
440 mg/L, unrefined 78 2.48 97
134 mg/L, unrefined 78 1.78 98
[00112] Example 14: Ferrous chloride solution
[00113] A solution of ferrous chloride was made at a concentration of
5Oppm Fe2+
(as Fe2+) by adding 98% pure iron (II) chloride (Sigma-Aldrich) to tap water.
The pH
was adjusted to 7.1 by adding 1M NaOH.
[00114] Example 15: Cellulose slurry
[00115] A slurry of 0.5% refined hardwood pulp was produced by adding
14.2 g of
a 3.5% slurry of Kraft hardwood pulp to a beaker and diluting the mixture to
100 g with
distilled water.
[00116] Example 16: Flocculant solution
[00117] A 0.05% solution of flocculant was produced by adding 0.117 g
of DAF-50
(Polymer Ventures, 50% anionic high molecular weight polyacrylamide) to 234 g
distilled water. The solution was mixed with a magnetic stirrer until uniform.
[00118] Example 17: Treating ferrous chloride solution with oxidizing
agent and
cellulose and flocculant
[00119] 100 ml of the ferrous chloride solution prepared in accordance
with
Example 14 was poured into a 300 ml beaker and stirred with a magnetic stir
bar using a
Cimarec magnetic stir plate at setting 8. To this solution was added 0.010 mL
of a 50%
hydrogen peroxide solution, and 2 mL of the cellulose slurry prepared in
accordance with
Example 15. After 1 minute, 0.400 ml of the flocculant prepared in accordance
with
Example 16 was added. After 1 minute, the resultant mixture was poured over a
70 mesh
(212 micron) screen and the turbidity of the filtrate was measured with a Hach
2100P
Turbidimeter. The measured turbidity was 11 NTU.
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[00120] Example 18: Treating ferrous chloride solution with oxidizing
agent and
cellulose and flocculant
[00121] A ferrous chloride solution prepared in accordance with Example
14 was
stirred as described in Example 17 for two days. The resulting solution was
then treated
with oxidizing agent and cellulose as set forth in Example 17. The measured
turbidity
was 19 NTU.
[00122] Example 19: Treating ferrous chloride solution with cellulose
and
flocculant
[00123] A ferrous chloride solution was prepared and stirred as
described in
Example 18. To this solution was added 2 mL of the cellulose slurry prepared
in
accordance with Example 15. The turbidity was measured as described in Example
17.
The measured turbidity was 3.6 NTU.
[00124] Example 20: Produced water sample properties
[00125] A sample of produced water was found to have the following
properties:
125 ppm total iron, 41 ppm dissolved iron, 9.8% dissolved solids, pH 7.
[00126] Example 21: Treating produced water with oxidizing agent and
cellulose
and flocculant
[00127] The procedure set forth in Example 17 was performed on produced
water,
using 100 ml of produced water as described in Example 20. For the oxidizing
agent,
0.03 ml of a 50% hydrogen peroxide solution was used. 4 ml of cellulose
prepared in
accordance with Example 15 was used, and 0.800 ml of the flocculant prepared
in
accordance with Example 16 was used. The measured turbidity was 46 NTU.
[00128] Example 22: Oxidizing produced water by exposure to room air
[00129] A 400 ml sample of produced water as described in Example 20
was placed
in a beaker, and was exposed to room air that was bubbled through it using an
air stone
and an aquarium pump for about two hours.
[00130] Example 23: Treating produced water with oxidizing agent and
cellulose
and flocculant
[00131] The procedure described in Example 21 was performed on produced
water
treated as set forth in Example 22. The measured turbidity was 210 NTU.
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[00132] Example 24: Treating produced water with cellulose and
flocculant
[00133] The procedure described in Example 23 was performed, but no
hydrogen
peroxide was added. The measured turbidity was 218 NTU.
[00134] Example 25: Making synthetic frac flowback water
[00135] A sample of flowback water was used that contained 75 ppm of iron,
0 ppm
of dissolved iron, and 8.0% dissolved solids, pH 7. The suspended solids were
allowed to
settle. The supernatant was removed and treated by adding add 50 ppm Fe (as
Fe) to it by
adding 98% pure iron (II) chloride (Sigma-Aldrich).
[00136] Example 26: Treating synthetic frac flowback water with
oxidizing agent
and cellulose and flocculant
[00137] The procedure described in Example 17 was performed using the
synthetic
frac flowback water prepared in accordance with Example 25. The measured
turbidity
was 7.4.
[00138] Example 27: Air-oxidizing the synthetic frac flowback water
[00139] 400 ml of synthetic frac flowback water prepared in accordance with
Example 25 was placed in a beaker and exposed to room air that was bubbled
through it
using an air stone and an aquarium pump for about two hours.
[00140] Example 28: Treating synthetic frac flowback water with
oxidizing agent
and cellulose and flocculant
[00141] A 100 ml sample of air-oxidized synthetic frac flowback water
prepared in
accordance with Example 27 was treated as described in Example 17. The
measured
turbidity was 102 NTU.
[00142] Example 29: Treating synthetic frac flowback water with
cellulose and
flocculant
[00143] The experiment performed in Example 18 was carried out without
adding
hydrogen peroxide. The measured turbidity was 95 NTU.
[00144] Example 30: Flowback water sample properties
[00145] A sample of flowback water was found to have the following
properties: 38
ppm total iron, 0 ppm dissolved iron, 2.5% dissolved solids, pH 7, Turbidity
of 212.
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[00146] Example 31: Flocculant solution
[00147] A 0.1% solution of flocculant was produced by adding 0.100 g of
DAF-50
(Polymer Ventures, 50% anionic high molecular weight polyacrylamide) to 100 g
distilled water. The solution was mixed with a magnetic stirrer until uniform.
[00148] Example 32: Treating flowback water with diatomaceous earth
[00149] 200 ml of flowback water described in Example 30 was placed
into a
graduated cylinder, and 0.010 mL of 50% H202 and 0.150 g of pool filter grade
diatomaceous earth (DicaLite) was added. The end of the cylinder was plugged
with a
gloved hand and inverted three times. 0.400 ml of the flocculant solution
described in
Example 31 was added, and the cylinder was inverted another 10 times. The
contents of
the cylinder were allowed to settle for two minutes. The top 150 cc was
decanted from
the cylinder, and its turbidity was measured with the Hach 2100P Turbidimeter.
The
turbidity of the sample was 78 NTU. The iron content of this decanted specimen
was
measured Hach DR2700 using the FerroVer method. The iron concentration was 5.2
mg/L.
[00150] Example 33: Treating flowback water with addition of ferrous
chloride
[00151] To a 200 ml sample of flowback water described in Example 30
was added
Add 0.0079 g of 98% iron (II) chloride. The procedure described in Example 32
was then
performed. The measured turbidity was 26 NTU. The iron concentration was 1.8
mg/L.
[00152] Example 34: Treating flowback water with addition of ferrous
chloride
[00153] The experiment described in Example 33 was performed, with the
addition
of 0.0244 g 98% iron (II) chloride instead of the amount described in Example
33. The
measured turbidity was 26 NTU. The iron concentration was 3.2 mg/L.
[00154] Example 35: Treating flowback water with addition of ferric
chloride
[00155] The experiment described in Example 33 was performed, with the
addition
of 0.0093 g of 97% iron (III) chloride instead of iron (II) chloride described
in Example
33. The measured turbidity was 32 NTU. The iron concentration was 2.2 mg/L.
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[00156] Example 36: Treating flowback water with addition of ferric
chloride
[00157] The experiment described in Example 33 was performed, with the
addition
of 0.0051 g of iron (III) hydroxide (Phos-ban) instead of the iron (II)
chloride. The iron
concentration was 7.2 mg/L.
[00158] Example 37: Treatment of flowback water
[00159] 200 ml of the flowback water described in Example 30 was placed
in a 250
ml graduated cylinder. 0.15 g of diatomaceous earth was added, and the
cylinder was
inverted three times. 0.08 ml of a 50% anionic high molecular weight
polyacrylamide
solution (0.05% SNF Flo-Pam 956 VHM) was added. The cylinder was inverted ten
times and left to settle for two minutes. 190 cc of supernatant was poured
off, leaving 10
ml of fluid in the 250 ml graduated cylinder. 200 ml of the flowback water
from Example
30 was added to the remaining 10 ml in the cylinder. 0.15 g diatomaceous earth
was
added, and the mixture was inverted three times in the cylinder to mix it. An
additional
0.8 ml of 0.05% SNF Flo-Pam 956 VHM was added, with the cylinder being
inverted ten
times to mix. The mixture was allowed to settle for two minutes. 150 ml of the
supernatant was poured off and its iron concentration was measured as
described in
Example 32. Iron concentration was 5.4 mg/L.
[00160] Example 38: Coating diatomaceous earth with iron (III)
hydroxide
[00161] 11.5 g pool-filter grade diatomaceous earth (DE) was dispersed
in 100 ml
of deionized water. Separately, 20 ml of deionized water was boiled, and 0.186
g iron
(III) chloride was added to the boiling water. This iron chloride solution was
added to the
DE slurry. The pH of the slurry was raised to 7, titrating with 1M NaOH. The
DE was
isolated from the slurry by vacuum filtering it in a 7cm diameter Buchner
funnel fitted
with 1 micron filter paper. The filter cake was washed with 50 ml deionized
water. The
filter cake was collected and dried at 115 C for 3 hours or until completely
dry. This
process yielded DE coated with iron (III) hydroxide.
[00162] Example 39: Iron removal using iron-coated DE
[00163] 200 ml of the flowback water described in Example 30 was placed
in a 250
ml graduated cylinder. 0.075 g of the iron-coated DE prepared in Example 38
was added
to the cylinder, and the cylinder was inverted 3 times. 0.08 mL of 0.05% SNF
Flo-Pam
956 VHM (50% anionic high molecular weight polyacrylamide) was added to the
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cylinder, and the cylinder was inverted ten times. The mixture was allowed to
settle for
two minutes. 150 ml of the supernatant was poured off and its iron
concentration was
measured as described in Example 32.
[00164] Example 40: Treating flowback water with added iron
[00165] 0.0046 g of iron (III) oxide 99% pure from Sigma Aldrich was added
to
200 mL of flowback water as described in Example 30. The procedure described
in
Example 32 was performed on this sample. The iron concentration was 11.7 mg/L.
[00166] Example 41: Treating flowback water with added iron and DE
[00167] 200 ml of the flowback water described in Example 30 was placed
in a 250
ml graduated cylinder. 0.0093 g of 97% iron (III) chloride was added. 0.015 g
of DE
was also added. The cylinder was inverted 3 times to mix. 0.08 mL of 0.05% SNF
Flo-
Pam 956 VHM (50% anionic high molecular weight polyacrylamide) was added to
the
cylinder, and the cylinder was inverted ten times. The mixture was allowed to
settle for
two minutes. 150 ml of the supernatant was poured off and its iron
concentration was
measured as described in Example 32. Iron concentration was 11.8 mg/L.
[00168] Example 42: Treating flowback water with added DE and iron-
coated DE
[00169] 200 ml of the flowback water described in Example 30 was placed
in a 250
ml graduated cylinder and 0.0093 g of 97% iron (III) chloride was added. 0.015
g of the
iron-coated DE prepared in Example 38 was added to the cylinder, and the
cylinder was
inverted 3 times. 0.08 mL of 0.05% SNF Flo-Pam 956 VHM (50% anionic high
molecular weight polyacrylamide) was added to the cylinder, and the cylinder
was
inverted ten times. The mixture was allowed to settle for two minutes. 150 ml
of the
supernatant was poured off and its iron concentration was measured as
described in
Example 32. Iron concentration was 6.8 mg/L.
[00170] Example 43: Preparing Iron Salt/DE blend
[00171] In a small Flak-Tech cup, 12.1275g of natural diatomaceous
earth, Eagle
Picher product MN-84, and 0.2475g of ferrous chloride, anhydrous, were
combined.
They were mixed in a speed mixer for 10 seconds at 2500 rpm. The final blend
was 98%
DE and 2% ferrous chloride by weight.
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[00172] Example 44: Treating flowback water with Fe/DE dry blend
[00173] 200 ml of the flowback water described in Example 30 was placed
in a 250
ml graduated cylinder, and 0.157 g of the Fe/DE dry blend prepared in Example
43 was
added. The cylinder was inverted 3 times to mix. 6.6 ,L of 50% H202, 2 mL of
0.1M
NaOH, and 800 1.1,L of 0.05% FloPam AN 956 VHM from SNF were added, and the
cylinder was inverted ten times. The mixture was allowed to settle for two
minutes. 150
ml of the supernatant was poured off and its turbidity and iron concentration
were
measured as described in Example 32. Turbidity was 18.2ntu and iron
concentration was
1.70mg/L.
[00174] Example 45: Preparation of Iron salt/DE blend as slurry
[00175] 2 g of the dry blend described in Example 43 was added to 18 ml
DI water.
This slurry was mixed using a magnetic stir bar and stir plate to keep the
particles
suspended.
[00176] Example 46: Treating flowback water with Fe/DE dry blend
[00177] 100 ml of the flowback water described in Example 30 was placed in
a 170
ml graduated cylinder. 0.75 mL of the 10% solids slurry described in Example
45 was
added. The cylinder was inverted 3 times to mix. 3.3 1.1,L of 50% H202, 1 mL
of 0.1M
NaOH, and 4004, 0.05% Zetag 4145, (50% mol anionic acrylamide co-polymer
supplied
by BASF) were added, and the cylinder was inverted ten times. The mixture was
allowed
to settle for two minutes. 75 ml of the supernatant was poured off and its
turbidity and
iron concentration were measured as described in Example 32. Turbidity is
24.8ntu and
the iron is 0.57 mg/L.
[00178] Example 47: Preparing a synthetic frac water
[00179] 16.7 L tap water was poured into a 5 gallon bucket. lkg of NaC1
and 249g
CaC12=2H20 were added and mixed until dissolved, forming a synthetic brine.
1.83g of
ferrous chloride was added to the synthetic brine, forming a synthetic frac
water.
[00180] Example 48: Continuous processing of frac water
[00181] The synthetic frac water as prepared in Example 47 was treated
12.375 g of
the Fe/DE dry blend described in Example 44. This solution was then oxidized
with 551
1.1,L of 50% H202, and its pH was adjusted to 7 with 5M NaOH. A continuous
system
was set up so that the synthetic frac water was moved by a peristaltic pump
through an in-
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line static mixer, then through a length of tubing, and finally into a
clarifier. Flocculent
was added to the system via a syringe pump directly before the static mixer.
The
peristaltic pump was set to pump the synthetic frac water at 1.4 L/min and the
syringe
pump added flocculent at a rate of 2.8 mL/min. The overflow water collected
from the
clarifier was analyzed for residual iron and turbidity. Over a 4 minute run
time, the
residual iron was measured between 2.48-2.79 mg/L and the turbidity was
measured at
14.0-17.8ntu.
[00182] Example 49: Treating synthetic frac water with Fe salt/DE blend
and
cellulose
[00183] 200 ml of the flowback water described in Example 47 was placed in
a 250
ml graduated cylinder. 0.15 g of the iron salt/DE dry blend prepared in
accordance with
Example 43 was added. The cylinder was inverted 3 times to mix. 2 ml of a
0.75%
unrefined hardwood pulp as added to the sample, with the cylinder inverted
another three
times to mix. 6.6 [IL of 50% H202 and 804, of 5M NaOH were added and the
cylinder
was inverted three times to mix. 400 [IL of 0.1% SNF Flo-Pam 956 VHM was
added,
and the cylinder was inverted ten times. The mixture was allowed to settle for
two
minutes. 150 ml of the supernatant was poured off and its turbidity and iron
concentration were measured as described in Example 32. Turbidity was 23.1ntu
and the
iron concentration was 2.81 mg/L.
[00184] Example 50: Treating flowback water with a Fe/DE blend
[00185] In each of the following experiments, 100 ml of the flowback
water
described in Example 30 was placed in a 250 ml beaker. A magnetic stir bar was
placed
in the beaker and the beaker was placed on a magnetic stir plate. The stir
plate was set to
7. The stirring sample was treated with 0.075 g of the Fe/DE dry blend
prepared in
Example 43, then treated with 3.3 [IL of 50% H202, then treated with 40 [IL 5M
NaOH.
The sample was then allowed to mix for a designated period of time. After
mixing, the
sample was transferred to a 170 mL graduated cylinder. Then 200 [IL of 0.1%
SNF Flo-
Pam AN 956 VHM was added to the sample. The graduated cylinder was then
inverted
10 times to mix. The sample was left to settle for 1 minute, after which 75 mL
of the
supernatant water was poured off Turbidity and iron concentration were
measured as
described in Example 32. The results are set forth in Table 7 below.
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Table 7
Time mixing Turbidity of supernatant Iron content of supernatant
0 151 19.9
0.5 77.6 0.94
2.5 54.9 5.5
3.5 101 7.8
4.5 99.4 7.4
[00186] Example 51: Treating flowback water with a Fe/DE blend
[00187] A slurry was prepared using 1 g of the ferrous chloride/DE
blend described
in Example 43 suspended in 9 g of deionized water. 100 ml of the flowback
water
described in Example 30 was placed in a 170 ml graduated cylinder. 0.75 ml of
the slurry
was added to the cylinder. The cylinder was inverted 3 times to mix. 3.3 [I,L
of 50% H202
and 40 L of 5M NaOH were added and the cylinder was inverted three times to
mix. 400
[I,L of 0.05% SNF Flo-Pam 956 VHM was added, and the cylinder was inverted ten
times.
The mixture was allowed to settle for one minute. 75 ml of the supernatant was
poured
off and its turbidity and iron concentration were measured as described in
Example 32.
Turbidity was 24.8 ntu and the iron concentration was 0.57 mg/L.
[00188] Example 52: Flotation promoter for improved collection of
suspended
solids
[00189] To 200 mL samples of oil field produced water with a total
dissolved solids
(TDS) of 302,000 ppm and 105 ppm Fe, add an anchor particle (98% natural
diatomaceous earth MN-84 from Eagle Pitcher, 2% ferrous chloride from Sigma
Aldrich),
8% hydrogen peroxide in water, and 15% sodium hydroxide in water. Each of
these
samples then had added various amounts of 0.1% lauric acid (LA) in isopropanol
or 0.1%
sodium laurate (NaL) in water added to act as a flotation promoter. Finally, a
solution of
0.1% polyacrylamide polymer (Flopam EM 430) was added and mixed for 1 minute.
Removable complexes were allowed to settle, and then the time it took for
removable
complexes to float was noted. The pH was between 7.5 and 7.8 for all runs.
Removable
complexes initially sunk and then floated. Increasing the flotation promoter
concentration
decreased the flotation time. The results are set forth in Table 8 below.
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Table 8
Trial # Particle H202 NaOH Float Promoter Polymer Time to
(g) (pL) (pL) Promoter (pL) (pL) float (s)
1 0.152 200 800 - 800 90
2 0.149 200 1000 LA 100 800 90
3 0.152 200 800 LA 800 800 40
4 0.151 200 800 NaL 800 800 55
0.149 200 800 NaL 3000 800 30
[00190] Example 53: Preparation of iron-spiked water
[00191] 19.3 kg oil field produced water sample with a TDS of 302,000
ppm and
57.6 ppm Fe2+ was treated with 9.3 g MN-84 diatomaceous earth, 12.5 mL 8%
hydrogen
5 peroxide, and 66.4 mL 25% sodium hydroxide. This material was then pumped
at 1.4
L/min while mixing, and 0.1% Flopam EM 430 was added at 5.6 mL/min in line.
The
fluid then passed through a static mixer and a long length of tube into a 2
gal vessel.
Removable complexes were made of the solids in the system, which settled at
the bottom
of the vessel. Water overflowed the vessel into a bucket. 17.5 kg of the
treated water was
reserved, and then 15.5 g of ferrous sulfate heptahydrate was added. The pH
was 8.5.
[00192] Example 54: Iron removal from water by flotation of sludge
[00193] The 200 mL samples of the iron-spiked water from Example 53
were
treated using the chemicals mentioned in Example 52, except the particle was
diluted to a
3.75% slurry and no hydroxide was added. The flotation promoter used was a
mixture of
1% lauric acid in isopropanol. Chemicals were added in the same order as
Example 52.
The pH of the final water was neutral. Results showed that a lower dose of
peroxide
prevents flotation, and higher doses cause flotation to occur faster. Results
also show that
the removable complexes ("RCs") sink after being disturbed, which suggests
that
agitation removes the bubbles from the removable complexes, causing them to
sink. The
results are set forth in Table 9 below.
Table 9
Trial # Slurry H202 NaOH Promoter Polymer Observation
(mL) (mL) (mL) (mL) (mL)
1 3 1 1 RCs sink, wait 30s and
then all suddenly float.
Disturbing the top
causes some to fall
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Trial # Slurry H202 NaOH Promoter Polymer Observation
(mL) (mL) (mL) (mL) (mL)
2 1 1 RCs stay suspended and
then float. Twisting
beaker makes some sink
3 - 1 - 1 1 RCs flow more quickly
than in Trial 2.
Twisting glass makes
some sink
4 3 .2 - - 1 RCs sink and do not
float overnight. No
dissolved iron remains.
3 .3 - - 1 RCs sink, then float
after 4.5 min
[00194] Example 55
[00195] Phosphate buffer was prepared mixing 17.957 g sodium phosphate
monobasic dihydrate (Aldrich), 35.819 g sodium phosphate dibasic (Aldrich),
and 200.72
5 g distilled water. The pH of the buffer was 6.94.
[00196] Example 56
[00197] 0.2 g of ammonium persulfate (Aldrich) was added to 500 mL of
Cambridge, MA tap water. A guar gel was then formed by injecting 2.8 mL of
Progel 4.5
(International Polymerics) into the water while it was blended in a blender,
and hydrating
for 10 minutes. The pH of the gel was adjusted by adding 1.3 mL of 1 M sodium
hydroxide to about 9.5-10. Approximately 5 mL of a 2% solution of sodium
tetraborate
decahydrate was then added and mixed, causing a gel to form passing the visual
lip test
(commonly used in the oilfield to evaluate guar gels). The gel was then placed
into a
sealed 1-L bomb reactor and placed in the oven at 121 Celsius for 4 hours. The
sample
was removed and cooled, and the measured viscosity on the OFT model 800
viscometer
(R1B1 configuration at 300 RPM) was observed to be 1 cP. The sample was placed
in a
separator funnel to remove the liquid from the floating solids.
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[00198] Example 57
[00199] 450 mL of a broken guar gel formed in accordance with Example
56was
treated with was treated with 0.103 g of ferrous chloride. The total iron of
the solution
was found to be 99 mg/L Fe.
[00200] 100 mL samples were mixed in 250-mL beakers and treated with a
3.75%
diatomaceous earth slurry of Example 45 for 1 minute. A phosphate solution of
Example
55 was sometimes added instead and mixed for 1 minute. Then a 7% hydrogen
peroxide
solution, and a 25% sodium hydroxide solution was added and mixed for one
minute. Finally, a 0.1% polyacrylamide (anionic) solution was added and mixed
for 10
to minutes. Once the contents settled, the supernatant was tested for
residual iron. In Trial
3 in the table below, the mixing time of phosphate and peroxide were increased
to 5
minutes. The results are set forth in Table 10 below.
Table 10
Trial 0 1 2 3
3.75% DE slurry (mL) - 1.5 - -
Phosphate solution (mL) - - 0.5 0.5
7% H202 (mL) - 0.1 0.1 0.1
25% NaOH (mL) - 0.1 - -
0.1% polyacrylamide solution - 0.8 0.8 0.8
(mL)
Remain Iron (ppm) 99 92 9 5
EQUIVALENTS
[00201] While this invention has been particularly shown and described
with
references to preferred embodiments thereof, it will be understood by those
skilled in the
art that various changes in form and details may be made therein without
departing from
the scope of the invention encompassed by the appended claims.
47
