METHOD FOR LIQUID FILTRATION

Description

FIELD OF THE DISCLOSURE

[0001] The present disclosure relates to a filtration method that reduces membrane fouling in accordance with the appended claims.BACKGROUND OF THE DISCLOSURE

[0002] Since almost all forms of life need water to survive, the improvement of water quality in decontamination systems has typically been a subject of significant interest. As a result, treatment systems and techniques for removing contaminants from contaminated fluids have been developed in the past. Prior approaches have included water treatment by applying various microorganisms, enzymes and nutrients for the microorganisms in water. Other approaches involve placing chemicals, such as chlorine, in the contaminated fluids in an effort to decontaminate supplies. Some such systems have proved to be somewhat successful; however, severe deficiencies in each approach may still be prominent. In some prior systems, solid reactants are used that have to be dissolved or dispersed prior to use, or were cumbersome and not particularly suited for prolonged water treatment, or could not be used in a wide variety of different types of applications. In particular, the handling of the solid reactants often posed problems with respect to different dissolution rates, concentrations and growth rates. In addition, in systems employing chemical additives, the resulting "decontaminated" fluid may actually now be contaminated by these chemicals, in spite of having removed the original biological or other contaminants from the media. Even in systems employing micro filtration, problems with the system may not be from any sort of additive, but instead may simply be the clogging of the filter elements or membranes with foulants accumulated from the decontamination process. Time-consuming filter cleaning processes combined with system downtime can become costly and inefficient for purification companies.

[0003] One approach to treating surface waters and other contaminated fluids is to coagulate water-borne contaminants with suitable coagulants such as ferric chloride, polyaluminum chloride, alum, or other coagulants known in the art. Chemical coagulants change the surface charge of contaminants, which reduces the repelling force between the contaminants. As such, the coagulants allow the contaminants to collide and coagulate together into larger flocs. Larger particles can still be formed by adding suitable polymers into the contaminated fluid. The polymers form bridges between the flocs to form large agglomerates. The large agglomerates settle with gravity and may be removed by a clarifier or a filter.

[0004] Some treatment processes may include modifying the pH of the contaminated fluid prior to adding the coagulants because some coagulants operate best within a specific pH range. For example, some ferric-based coagulants may operate best at reduced pH levels, which may require adding acids to the contaminated fluid. Other coagulants may operate best at specific alkalinities, which may require adding bicarbonate or acids depending on whether the alkalinity is too low or high. In some cases, the addition of the coagulant itself may affect the pH, and neutralization may be required.

[0005] Another approach to treating contaminated fluid uses ion exchange to exchange benign molecules with contaminants of concern. An example is the removal of hexavalent chromium. Once the exchange sites of the ion exchange media is spent, the regeneration of the exchange media creates a large volume of brine containing the contaminants of concern.

[0006] As used herein, "contaminated fluid" is a fluid that contains undesirable organic, inorganic products, metals, and possibly microbial cells or other microorganisms. Although contaminants are undesirable in the sense that they are usually toxic when ingested or contacted by humans, the term "undesirable" should not be understood to be restricted to such toxic substances.

[0007] EP1903008A1 describes a method for treating a hardly-decomposable-substance-containing water which including: (B) adding an adsorbent to water containing a hardly decomposable substance to cause the hardly decomposable substance to be adsorbed on the adsorbent (adsorption treatment step); (C) separating a permeated liquid through a filter membrane to concentrate the adsorbent which has adsorbed the hardly decomposable substance (membrane filtering treatment step); (D) decomposing the hardly decomposable substance which has been adsorbed on the concentrated adsorbent (hardly decomposable substance decomposition step); and (E) returning the adsorbent after the decomposition of the hardly decomposable substance to the adsorption treatment step (B) (adsorbent returning step); and an apparatus for the treatment .

[0008] US5462674A describes a method and system for purifying a contaminated fluid in a continuous manner is herein disclosed. The method and system provide for the irradiation of a slurry between a defined surface(s) such that substantially all of the contaminants are removed from the slurry, and a turbulent flow of the slurry is achieved. The method and system further provide for the separation of decontaminated effluent from the slurry by employing ceramic membrane filters. Air is applied to the ceramic membrane filters at relatively high pressures to remove any photoreactive catalyst particles that have collected in the ceramic membranes.SUMMARY

[0009] Accordingly, a need has arisen for improved apparatus, systems, and methods for reduction and / or removal of one or more undesirable materials from a feed composition.

[0010] In accordance with the present invention there is provided a method for separating an intake fluid comprising a contaminant into a contaminant solid fraction and a discharge fluid fraction substantially free of the contaminant in accordance with the appended claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Some embodiments of the disclosure may be understood by referring, in part, to the present disclosure and the accompanying drawings, wherein: FIGURE 1A illustrates a perspective view of a filtration membrane; FIGURE 1B illustrates a section view of the filtration membrane shown in FIGURE 1A; FIGURE 2 illustrates a filtration system having a defouling mechanism; FIGURE 3 illustrates an energy profile of a filtration system having a defouling mechanism; FIGURE 4 illustrates a detailed energy profile of a filtration system having a defouling mechanism; FIGURE 5 illustrates a block diagram demonstrating a defouling method; FIGURE 6A illustrates a filtration system having a defouling mechanism; FIGURE 6B illustrates a filtration system having a defouling mechanism; FIGURE 7A illustrates a perspective view of a silicon carbide filtration membrane; FIGURE 7B illustrates a section view of the filtration membrane shown in FIGURE 7A; FIGURE 8 illustrates a block diagram demonstrating a decontamination system; FIGURE 9 illustrates an example of a filter unit; FIGURE 10 illustrates an example of an adsorbent recovery unit; FIGURE 11 illustrates an example of a decontamination system having a photocatalytic reactor; FIGURE 12 illustrates an example of a decontamination system having a non-photocatalytic reactor; FIGURE 13 illustrates a cross-sectional view of a filtration unit; FIGURE 14 is an example relationship of efficiency versus time in a semi-batch process; FIGURE 15 illustrates an example of a block diagram of a decontamination system of an example embodiment according to the present invention. FIGURE 16 shows the results of a pilot test of a decontamination systems operated in a batch mode; FIGURE 17 illustrates an example of a trap in which contaminant-adsorbent material has collected after dead end filtration; and FIGURE 18 illustrates an example of low pH contaminant water after neutralization with base to a pH greater than neutral, including contaminant precipitate. DETAILED DESCRIPTION

[0012] The present disclosure describes apparatus, systems, and methods for reduction and / or removal of one or more heavy metals (e.g., heavy metals, chromium, phosphorous, phosphorous compounds, nitrogen, nitrogen compounds) from a feed composition (e.g., a fluid).

[0013] The present disclosure describes efficient defouling mechanisms for removing foulants in a filtration membrane and filtration membranes optimized for use with the disclosed defouling mechanisms.

[0014] However, it is to be understood that the apparatus and systems described are not part of the claimed invention but are included to aid the understanding of the claimed invention, which is set out in the appended claims.

[0015] FIGURE 1A is a schematic diagram illustrating a filtration membrane 10, and FIGURE 1B is a schematic cross-sectional view of the filtration membrane 10 shown in Figure 1A. The illustrated filtration membrane 10 includes a porous substrate 12 having a plurality of longitudinal channels 14 defined therein. In the illustrated filtration membrane, membrane films 16 are disposed on the surface of the channels 14. Contaminated media may be fed into filtration membrane 10 at a first end 18. The membrane films 16 may be operable to separate contaminated media into a permeate fluid that was able to pass through the membrane film 16 and a retentate fluid that exits at a second end 11 of the filtration membrane 10. The permeate fluid may pass through the pores (not shown) of the substrate 12 and exit the filtration membrane 10 through at least one outlet 13. Both the permeate and retentate fluids may undergo further treatment such as additional filtration or decantation. As used herein, "contaminated media" is a fluid that contains undesirable organic, inorganic products, metals, and possibly microbial cells or other microorganisms. Although contaminants are undesirable in the sense that they are usually toxic when ingested or contacted by humans, the term "undesirable" should not be understood to be restricted to such toxic substances.

[0016] In a process of using the filtration membrane 10 to decontaminate contaminated media, the performance of the filtration membrane 10 may decline due to organic, inorganic and biological fouling mechanisms in the process. For example, excessive fouling of the substrate 12 and / or the membrane films 16 may decrease flux, increase cross flow and trans-membrane pressure, and increase energy consumption.

[0017] FIGURE 2 illustrates a schematic diagram of a filtration system 20 having a defouling mechanism. The filtration system 20 includes the filtration membrane 10 shown in Figures 1A and 1B, and a piston 22 and a valve 24 connected to the permeate outlet 13 of the filtration membrane 10. In operation, the valve 24 may remain open until the filtration process needs to be paused for defouling of the substrate 12 and the membrane films 16. A back-pulse or back-wash of the permeate fluid may be applied by closing the valve 24 and using the piston 22 to push the permeate fluid back through the substrate 12 and across the membrane films 16. The shearing force of the permeate fluid caused by the movement of the displaced volume of permeate fluid may release some of the foulants to be released from the substrate 12 and / or the membrane films 16. Such a back-pulse or back-wash created by the piston 22 may have inefficiencies. First, since the back-pulse or back-wash causes the permeate fluid to return to the concentrate side of the membrane film 16, the filtration of the amount of returned fluid is wasted, and the filtration time is extended. Also with these defouling mechanisms, channeling of the back-pulse or back-wash fluid may result in uneven cleaning of the substrate 12 and / or the membrane films 16. The back-pulse or back-wash fluid tends to flow back through the cleaner elements, not the fouled elements, due to reduced pressure drop. As such, the worst fouled elements received less cleaning and will continue to degrade over time.

[0018] FIGURE 3 is a schematic diagram showing the energy profiles of a back-pulse and a back-wash over time. Period 42 in Figure 3 reflects the duration of the backward flow of the permeate fluid in a back-pulse. Period 44 reflects the duration of the backward flow of the permeate fluid in a back-wash. Due to the time required for the physical movement of fluid across the substrate 12 and the membrane films 16, the period 42 for a back-pulse ranges in the seconds while the period 44 for a back-wash ranges in the minutes.

[0019] Also shown in FIGURE 4 is an exemplary energy profile of a dynamic shock that may be used to clean the membrane 10. Compared to a back-pulse or a back wash, the illustrated dynamic shock introduces an amount of energy that is sufficiently high and in such a short duration so as to create cavitation in the fluid proximate to the substrate 12 and membrane films 16. The cavitation of the dynamic shock is operable to form and substantially immediately implode cavities in the fluid located throughout the membrane 10, thereby rupturing biological matters and releasing organic and inorganic matter from the substrate 12 and membrane films 16. An exemplary approach for creating cavitation is to subject the fluid in the membrane 10 to rapid changes of pressure to cause the formation of cavities where the pressure is relatively low.

[0020] FIGURE 4 a schematic diagram showing a focused view of an exemplary energy profile of the illustrated dynamic shock. FIGURE 5 is a flow chart illustrating an exemplary method for producing the dynamic shock illustrated in Figures 3 and 4. The illustrated dynamic shock may include three sub-second phases 52, 54, and 56. In step 62, the first phase 52 may include a rapid accumulation of energy to create a first shockwave throughout the fluid and foulants in the membrane 10. The energy transfer to the fluid and foulants in the membrane 10 may be affected with a rapid pressure increase. In such a case, no physical movement of the fluid in the membrane 10 is required, and as such, the energy transfer in the first phase 52 may be achieved in less than a second. In step 64, the second phase 54 may or may not include holding the energy transferred to the fluid and foulants in membrane 10 for less than one second. However, in the second phase 54, there may be a limit as to how quickly the valves may be opened and closed. In step 66, the third phase 56 may include a rapid release of the energy stored creating an exploding reverse shock wave throughout the fluid and foulants in the membrane 10, thereby either destroying the foulants or lifting them off the substrate 12 or membrane films 16. Again, no physical movement of the fluid in the membrane 10 is required in the third phase 56, and as such, the energy transfer in the third phase 56 may be achieved in less than a second. The first shock wave produced in the first phase 52 and the second reverse shock wave produced in the third phase 56 both may create cavitations at the substrate 12 and the membrane films 16.

[0021] It is to be appreciated that a dynamic shock is distinct from a back-pulse or a back-wash, and offers performance improvements in at least several aspects. The phases of a dynamic shock may be carried out in less than one second, and substantially little or no permeate is lost back to the concentrate side of the membrane films 16. Consequently, a dynamic shock can be repeated as frequently as desired to prevent matter from fouling the membrane 10. For example, dynamic shocks may be applied to the membrane 10 about once per minute to prevent the lodging of foulants before they become fixed on the membrane 10 and accumulate. The dynamic pulses may be applied from about once per second to about once per 5 seconds, to about once per 15 seconds, to about once per 30 seconds, to about once per 45 seconds, to about once per 60 seconds, to about once per 75 seconds, to about once per 90 seconds, to about once per 2 minutes, to about once per 5 minutes, or longer. Bursts of multiple pulses (e.g., about 2 to about 5 pulses all applied within about 1-10 seconds) may be applied at the same frequencies as single pulses (e.g., one burst repeated about every minute).

[0022] By relying on cavitation instead of physical shearing force to clean the membrane 10, the effect of water channeling becomes irrelevant, and the cleaning of the membrane 10 may be performed consistently throughout the membrane 10. It is to be further appreciated that the ability for more efficient and consistent cleaning throughout the membrane 10 allows for packing more membrane films 12 and channels 14 into one membrane 10.

[0023] The dynamic shock may be generated with any mechanism for a rapid release of energy to the membrane surface, such as the Hammer effect, shot peaning to remove paint, and sonification. FIGURE 6A is a schematic diagram of an exemplary filtration system 70 operable to generate a dynamic shock for defouling the membrane 10. The system 70 may include the filtration membrane 10 discussed in the present disclosure. To provide dynamic shock for defouling the membrane 10, the system 70 may include a valve 72 in the permeate line for controlling the flow of the permeate out of the membrane 10. The permeate line may be connected to a compressed air or steam supply 76, and a valve 74 may be disposed in parallel to the valve 72 for controlling the flow of compressed air or steam into the permeate line. The valves 72 and 74 may be controlled by a controller 78, which may be configured to be operable to manipulate the valves 72 and 74 to provide a dynamic shock. The controller 78 may close the valve 72 to hydraulically isolate or close the permeate line, which creates a brief water hammer (low energy). The controller 78 may then open the valve 74 immediately thereafter, which would inject compressed air or steam into the permeate line and rapidly release high pressure into the permeate. The pressure in the compressed air or steam line is 100 to 200 psi greater than the pressure in the permeate line. As such, when the valve 74 is opened, the pressure in the permeate line can rapid increase by 100 to 200 psi, which would create a dynamic shock wave into the permeate fluid of the membrane 10, and throughout the rest of the membrane 10. A suitable degas technology may be used to remove the air that was injected to effect the shock wave. The degas technology may prevent loss of feed pump pressure.

[0024] The valve 74 may be opened and closed as quickly as physically possible to complete the first subsecond phase 52 of a dynamic shock. For example, the valve 74 may be opened and closed in less than .50 second; in an optimized example, the valve 74 may be opened and closed in less than 0.25 second. In an example, after less than a second of holding the elevated pressure, the second subsecond phase 54 may be completed. In the third subsecond section, the rapid high pressure in the permeate fluid may be released by opening valve 72 in the permeate line, which creates a rapid de-pressurization in the membrane 10 and causes a second reverse dynamic shock wave. This may be considered a double acting effect. Again, the valve 72 may be opened as quickly as possible. In some instances, opening valve 72 may take less than .50 second or less than .25 second. The above described process of operating the system 70 to provide the dynamic shock may be substantially prevent the fouling of the membrane 10, thereby allowing a continuous filtration process. It is to be appreciated that other suitable methods could be used to provide a dynamic shock. For example, a diaphragm (not shown) or ram (not shown) may transfer the energy required rapidly without moving or displacing the permeate fluid in the membrane 10.

[0025] FIGURE 6B is a schematic diagram showing an orientation of the exemplary filtration system 70 configured to reduce damping of energy transfer in the membrane 10. A design consideration is a substantial elimination of inertia or elasticity in all parts of the membrane 10 in order to reduce damping of the dynamic shock, which would reduce its effectiveness on cavitating or lifting foulants. An example of reducing or eliminating inertial in system 70 may include substantially eliminating air gaps, which may absorb the energy of the dynamic shock like a spring or damper. In another example, membrane 10 may be disposed horizontally relative to the ground 75 to reduce or eliminate air trapped in the membrane 10 and its housing 75. Similarly, the membrane 10 may be constructed of a material that is rigid. For example, for the purpose of reducing damping, stainless steel may be preferred over PVC. The dynamic shock may be more effective if membrane 10 is made of silicon carbide (SiC) over other membrane materials and designs because there is less dampening by the membrane films 16 and substrate 12 in a SiC membrane. Moreover, the compressed air or steam may be applied directly to the module to reduce or eliminate dampening effects. The use of compressed air may be preferred as the use of steam can collapse and dampen the impact of a dynamic shock.

[0026] FIGURE 7A illustrates a membrane 80 made of SiC. FIGURE 7B is a cross-sectional view of the SiC membrane 80. The SiC membrane 80 may be configured similarly to the membrane 10 and is suitable for use in any instances of filtration membranes or filtration systems disclosed herein. Due to its hydrophilic nature, the SiC membrane 80 may be used for filtration of a variety of foulants, including oil-based foulants, organic and inorganic substances, and biological foulants.

[0027] The SiC membrane 80 may allow for reduced trans-membrane pressure (TMP) because of the strength of SiC substrate 82 over Alpha Alumina. This allows for the economical use of a smaller pore size. Additionally, the SiC membrane 80 has smaller particles which allows for thinner wall and a thinner membrane. The illustrated dimensions, including the hexagonal cross-sectional shape of the SiC membrane 80, the separations between channels 84, the width of the SiC membrane 80, and the distance of the channels 84 from the edge of the SiC membrane 80, have been substantially optimized for flux, TMP, and cross flow pressure drop. The separations between the channels 84 (from center to center) may preferably range between 0.2 to 0.25 inches. The width of the SiC membrane 80 may preferably range between 1.25 to 1.75 inches. The distance between the center of the outside channels 84 to the edge of the SiC membrane 80 may preferably range between 0.14 to 0.18 inches. It is to be appreciated that the above discussed dimensions may be varied according to the needs of particular application.

[0028] It is to be appreciated that the filtration membranes and filtration systems of the present disclosure may be integrated with a variety of decontamination technology, such as photocatalytic technology. The integration may be accomplished without break tanks, loss of excessive line pressure, and / or booster pumps.

[0029] FIGURE 8 is a high-level schematic diagram illustrating an example decontamination system 100. System 100 receives a feed stream 110, which provides incoming contaminated fluid in need of filtration. The feed stream 110 may include a variety of contaminants, including various organic and inorganic compounds, such as metals, dissolved solids, and color compounds. An example list of metal contaminates includes phosphorus, lead, iron, manganese, technetium, arsenic, silver, gold, platinum, mercury, and chromium. Feed stream 110 may be mixed with suitable adsorbents provided from a reservoir 115 via a stream 120, resulting in a slurry stream 130. It is to be appreciated that suitable adsorbents may be any particle or mixture of particles that have good adsorptive capacity for the contaminants in feed stream 110 but may be stripped of the contaminants using a desorption process. Any insoluble particles described herein may be a suitable adsorbent. For example, where phosphorus compounds are present in feed stream 110, titanium dioxide, TiO 2 , may be a suitable adsorbent. Also shown in FIGURE 8 is a filter unit 140 that receives slurry stream 130 and separates the contaminants and adsorbents from the fluid in slurry stream 130. Filter unit 140 may output a decontaminated stream 150. In one instance, the separated contaminants and adsorbents may be removed from system 100 as waste. In another instance, system 100 may include a desorption unit 160 that receives a mixture 170 separated in filter unit 140 and comprising the contaminants and adsorbents. Desorption unit 160 may be operable to strip the contaminants from the adsorbents and recycle the recovered adsorbents back to filter unit 140 and / or stream 120 for reuse. Contaminants 180 may be removed from desorption unit 160 and disposed as waste and / or recovered. In an example, contaminants 180 recovered from desorption unit 160 may be subjected to an additional recovery process to recover the contaminants for reuse. For example, when contaminants, such as hexavalent chromium, are mixed with adsorbents, such as TiO 2 , and passed through filter unit 140 and desorption unit 160, the resultant contaminants separated from the adsorbents may be subjected to a boiling salt bath so as to recover the chromium.

[0030] FIGURE 9 is a schematic diagram illustrating an example filter unit 140. As illustrated, filter unit 140 may include an optional mixer 142 that allows the contaminants to interact with the adsorbent to form coagulated complexes of the contaminants and adsorbents. The mixer 142 may include an active mixing mechanism for dispersing the adsorbents in the contaminated fluid. Alternatively, the optional mixer 142 may be a simple holding tank, container, or any other structures that stores the mixture of the contaminated fluid and the adsorbents. The adsorbents may be introduced into filter unit 140 and / or added to the contaminated fluid stream 110 prior to entering filter unit 140.

[0031] Filter unit 140 may further include a suitable filter 144 for separating the macromolecules comprising the adsorbents and the adsorbed contaminants. Filter 144 may be a membrane that includes a wall (not shown) separating the interior of filter 144 from its exterior and pores (not shown) defined in the wall of filter 144. As slurry stream 130 passes through the interior of filter 144, the pores of filter 144 allow the movement of decontaminated fluid from the interior to the exterior of filter 144. Filter 144 may have an average pore size that is larger than the anticipated size of the macromolecules formed by the contaminants being adsorbed on the adsorbents. In an instance, the pore size of filter 144 is sufficiently large so as to induce micro-filtration of the treated slurry while only permitting negligible amounts of the contaminant-adsorbent macromolecules to permeate through the pores of filter 144. The pore size of filter 144 may be sized for ultra-filtration.

[0032] It is to be appreciated that during the operation of system 100, the flow rate of the slurry 130 and the pressure across the membrane of filter 144 may be maintained to allow for either dead-end filtration or cross-flow filtration. In dead-end filtration, the contaminant-adsorbent macromolecules are directed towards and collect on the wall of filter 144. In cross-flow filtration, two directional components are employed. First, a substantial linear velocity is maintained through the filter, i.e., parallel to the wall of filter 144. Second, a substantial pressure differential, also referred to as a transmembrane pressure, is applied across filter 144. The transmembrane pressure drives the decontaminated fluid through the wall of filter 144 while the high linear velocity continually removes most of the contaminant-adsorbent macromolecules away from the wall of the filter 140. This prevents the buildup of the contaminant-adsorbent macromolecules on the wall of the filter 140.

[0033] As shown in FIGURE 9, the decontaminated stream may exit filter unit 140 from filter 144. The contaminant-adsorbent macromolecules can be periodically removed from filter 144 in various ways. For example, high pressure air can be used to create a "shock wave" on the interior of filter 144. This is more fully disclosed in U.S. patent application Ser. No. 08 / 205,699, entitled "Method and System for Photocatalytic Decontamination," filed Mar. 3, 1994. Alternatively, back flushing and back pulsing techniques, as are readily known to one of ordinary skill in the art, can also be employed to remove the contaminant-adsorbent macromolecules.

[0034] The contaminant-adsorbent macromolecules may be provided to desorption unit 160 to strip the contaminants from the adsorbents. Desorption unit 160 may be configured according to a variety of desorption processes known in the art. The desorption unit may include a heating unit to raise the temperature and thereby promote the natural desorption of the contaminants from the adsorbents. In the example shown in FIGURE 10, desorption unit 160 includes stripping tank 162 where the contaminant-adsorbent macromolecules in the mixture 170 is introduced to an acid bath to separate and / or dissolve the contaminants from the adsorbents. It is to be understood that the bath may be an acid bath, base bath, or any other type of bath known in the art suitable to separate and / or dissolve the contaminants from the adsorbents. The acid solution including the separated and / or dissolved contaminants and the adsorbents may be provided to a separation device 164 for recovering the adsorbents 270 from the acid solution. The separation device 164 may be a suitable filter known in the art, such as a ceramic filter. It is to be appreciated that using adsorbents instead of coagulants in the feed stream 130 allows for the eventual separation of the adsorbents and the contaminants. This, in turn, allows for reusing of the recovered adsorbents in stream 120 and the optional recovery of contaminants, such as phosphorus and chromium compounds.

[0035] In some instances, contaminates such as phosphorus and chromium would readily be adsorbed onto a suitable adsorbent, such as TiO 2 . In other instances, it may be desirable to irradiate the contaminants with UV light to promote the adsorption of the contaminants onto the adsorbent. The UV irradiation may allow for photocatalytic oxidation and / or reduction of the contaminants to improve adsorption. Such UV irradiation may be applied to feed stream 110 and / or slurry stream 130, and such may be performed either before entering filter unit 140 or within filter unit 140. For example, lead contaminants may be oxidized to lead oxide, which may be adsorbed to TiO 2 more readily. Iron, manganese, technetium, and / or arsenic may also be oxidized in a similar fashion to promote more efficient adsorption. In another example, hexavalent chromium may be reduced to trivalent chromium, which may be adsorbed with TiO 2 more readily. Silver, gold, platinum, and mercury may also be reduced in a similar fashion to promote more efficient adsorption. In some instances, such as the treatment of color lignands, UV irradiation may improve adsorption even without a reduction or oxidation reaction. The UV irradiation is preferably applied to feed stream 110 prior to combining with the adsorbent stream 120 so as to ensure a maximum exposure of surface of the contaminants to the UV irradiation. To further promote adsorption of the contaminants, UV irradiation may be additionally applied to slurry stream 130 and / or within filter unit 140.

[0036] UV irradiation may be implemented in the decontamination system 100 in a variety of configurations. In an example, filter unit 140 may include a light source (not shown) configured to irradiate feed stream 110, slurry stream 130, and / or the contents of filter unit 140, such as the contents of mixer 142, with UV light to allow for a photocatalytic oxidation or reduction reaction. While filter unit 140 may include the UV light source, the decontamination system 100 may include one or more separate UV reactors 102 upstream of filter unit 140 as shown in FIGURE 11. One or more UV reactors 102 may be configured to receive feed stream 110 and / or slurry stream 130 to allow for a photocatalytic reaction to change the composition of the contaminants in slurry stream 130 prior to being fed into filter unit 140.

[0037] In another example, a non-photocatalytic oxidation or reduction of the contaminants in the contaminant fluid 110 may be affected in addition to or in replacement of the above-described UV irradiation by adding a suitable oxidizing chemical, such as chlorine, or a reducing agent, such as sodium metabisulphite, into the contaminated fluid 110 and / or into slurry stream 130. Referring to FIGURE 12, the decontamination system 100 may include one or more non-photocatalytic reactors 104 which receive the suitable oxidizing or reducing agent and allows them to react with the contaminants in the contaminated fluid 110 and / or slurry stream 130. In respect to the former, the output of reactor 104 may then mix with the adsorbent to provide a slurry stream 130. In an example, the suitable oxidizing or reducing agent may be added to filter unit 140, such as in mixer 142, in addition to or in replacement of the embodiment shown in FIGURE 12. In an example, slurry stream 130 in FIGURE 12 may also be irradiated by UV light according to the principles described herein to further promote the adsorption of the contaminants to the adsorption. For example, contaminated stream 110 may be passed through a UV reactor 102 and a non-photocatalytic reactor 104 prior to being combined with the adsorbents. It is to be understood herein that the adsorbents may be combined with contaminated stream 110 before being passed through filter unit 140 and / or within filter unit 140, such as in mixer 142.

[0038] The following passage relates to a filtration unit that is synergistically employed with insoluble particles. An example of such a filtration unit 200 is shown in FIGURE 13, which represents a cross sectional view of a membrane 202. While membrane 202 may be configured to have a variety of shapes and sizes, the illustrated example is a cylindrical membrane 202 having a sidewall 204 extending in a longitudinal direction. The sidewall 204 includes a plurality of pores 206 defined therein. As configured, membrane 202 is operable to allow the contaminated fluid comprising contaminants (not shown), adsorbents (not shown), and insoluble particles 208 to flow in a longitudinal direction along the interior of membrane 202, and pores 206 allow decontaminated fluid to pass radially to the exterior side of membrane 202.

[0039] The synergistic effects of employing insoluble particles 208 about membrane 202 may be achieved by maintaining the flow rate of the contaminated fluid and the transmembrane pressure such that filtration unit 200 is operating in cross-flow conditions. One resultant synergistic effect when the cross-flow condition is maintained is that insoluble particles 208 form a temporary membrane along the sidewall 204 of the membrane. The temporary membrane formed by insoluble particles 208, in turn, allows for increased flux across the membrane. For example, in an arrangement having a microfiltration membrane 202, the addition of a temporary membrane allows for ultra-filtration performance while maintaining the flux of a micro-filtration system. For example, the temporary membrane allows filtering of particles of about 1 micrometer to 1 nanometer in diameter. Typical ultra-filtration flux achieved in the industry are in the 50-100 GFD range, but a temporary membrane created by insoluble particles in a micro-filtration system can achieve flux in the 2000 GFD range.

[0040] While insoluble particles 208 may include any adsorbents disclosed in the present disclosure, insoluble particles 208 may also include substantially non-adsorptive particles. In a synergistic arrangement, insoluble particles 208 may be adsorptive and non-photocatalytic. Using adsorptive, insoluble particles 208, additional benefits may be realized in addition to the increase in flux. In an example in which insoluble, adsorptive particles are used in decontamination system 100 and a cross flow is maintained in filter 144, the resultant temporary membrane would allow for a synergistic combination of benefits, including high flux, elimination or reduction in the need for polymer addition, and recovery and reuse of adsorbent. Further advantages may be realized by using non-photocatalytic particles 208. Some of the biggest costs in a photocatalytic process include the energy cost for providing the UV light and the maintenance cost of the UV source. By running the treatment process in a non-photocatalytic system eliminates these costs and allows for significant cost savings.

[0041] Referring back to FIGURE 11, an example application of the above example arrangements will now be described for a contaminant stream comprising hexavalent chromium. In a first step, an appropriate amount of citric acid is added to the contaminant stream 110 so as to increase the rate at which hexavalent chromium is reduced to trivalent chromium, once contaminant stream 130 is sent to a photocatalytic process 102. In a second step, TiO 2 adsorbents are added to the contaminant stream prior to and after entering filtration unit 140. In the filtration unit 140, the TiO 2 adsorbs with the trivalent chromium and the resultant TiO 2 - trivalent chromium macromolecules 170 are filtered to desorption unit 160. In a third step, the TiO 2 - trivalent chromium macromolecules are subjected to an acid bath tank 162 of desorption unit 160 and heating at about 65 °C so as to separate the TiO 2 and the trivalent chromium. The recovered TiO 2 adsorbent 270 is then recovered and recycled for use in the next batch.

[0042] In another example application, the above process was slightly modified so as to provide for a semi-batch or continuous process. In this regard, as the contaminant stream 110 is continuously added in the first step, appropriate amounts of citric acid is also continuously added to the contaminant stream prior to subjecting contaminant stream 130 to a photocatalytic process 102. In the second step, the TiO 2 adsorbents are also continuously added to the contaminant stream in the form of a slip stream of TiO 2 prior to and after entering the filtration unit 140 so as to ensure the continuous feeding of contaminant stream 130 into the filtration unit 140 will meet with sufficient quantities of the TiO 2 adsorbent. In the third step, a dewatering step using a ceramic membrane is performed both prior to and after entering the acid bath. In this step, the recovered TiO 2 adsorbent is also continuously removed from desorption unit 160 and continuously recycled back for reuse. In performing a semi-batch or continuous process, the overall decontamination process will achieve consistently excellent efficiency throughout and not suffer from drops in efficiency during each batch, as encountered in a batch process. FIGURE 14 illustrates an example drop in efficiency for two separate batches. As shown in the figure, the efficiency of the decontamination process is excellent when the TiO 2 adsorbents are added (A). Thereafter, as the adsorbents combine with the chromium, the efficiency of the batch becomes reduced (B) due to the reduction of surface area and eventually reaches a level where the efficiency becomes very poor (C).

[0043] FIGURE 15 is a schematic diagram illustrating an example embodiment of a decontamination system 800 according to the present invention. System 800 receives a feed stream 820, which provides incoming contaminated fluid in need of filtration. In an embodiment, feed stream 820 may include chromium. Feed stream 820 may be mixed with suitable adsorbents provided from a reservoir 821 via a stream 801, resulting in a slurry stream 130. It is to be appreciated that suitable adsorbents may be any particle or mixture of particles that have good adsorptive capacity for the contaminants in feed stream 820 but may be stripped of the contaminants using a desorption process. Any insoluble particles described in the present disclosure may be a suitable adsorbent. Chromium or hexavalent chromium are present in feed stream 820, titanium dioxide, TiO 2 , is comprised in the adsorbent. In some embodiments, stream 801 may be metered (e.g., continuously metered) into feed stream 820 to generate a desired concentration of adsorbent comprising TiO 2 in stream 820. According to some embodiments, turbidity may be used as a surrogate measure of adsorbent concentration. Concentrations of TiO 2 may be about 350 mg / L and the turbidity of 350 mg / L may be measured and used as a set-point to determine how much TiO 2 to add. Turbidity (or another metric) may be assessed once or at any desired interval including continuously, periodically, haphazardly, and / or randomly.

[0044] In some embodiments, acid stream 802 (e.g., citric acid) may be dosed into stream 820 from tank 822. Citric acid plugs the photogenerated hole of the activated TiO2, providing conduction band electrons for enhanced photocatalytic reduction rates as described, for example, in U.S. Patent No. 5,554,300. Testing has demonstrated substantial power reductions with the use of citric acid.

[0045] Also shown in FIGURE 15 is photocatalyst reactor 825 that receives slurry stream 130 and reduces contaminants. For example, hexavalent chromium (Cr 6< ) may be reduced to trivalent chromium (Cr 3< ) in reactor 825. Conditions in reactor 825 may be configured to permit and / or promote adsorption of a reduced contaminant onto an adsorbent. For example, trivalent chromium (Cr 3< ) may adsorb onto the surface of TiO 2 . Testing has demonstrated reactor 825 may reduce 450 ppb of hexavalent chromium (Cr 6< ) to below 1ppb with just ~1.5 kWh / m 3< of treatment.

[0046] In some embodiments, photocatalytic reactor 825 and catalyst recovery unit 835 may operate like a photocatalytic system used for organic destruction. After the photocatalytic reaction, the Cr 3< -TiO 2 slurry discharges from the photocatalytic racks and enters an atmospheric accumulator tank 830. A ceramic membrane (catalyst recovery unit or CRU) operates in a standard cross flow manner to remove the Cr 3< -TiO 2 slurry (804), and the treated water 860 (e.g., < 1ppb Cr 6< ) is discharged. The CRU may concentrate the TiO 2 10 - 20 times in the CRU loop.

[0047] A slip stream of the contaminant / adsorbent concentrate in CRU loop is discharged (e.g., continuously discharged) to a contaminant removal and recovery process. For example, a slip stream of TiO 2 concentrate in loop 805 may be discharged to a Cr 3< removal and recovery process. This step may not be included in a photocatalytic process for organic destruction.

[0048] According to some embodiments, the flow rate of slurry 805 to the Cr 3< removal process may be minimized, for system optimization. Similarly, some of the TiO 2 slurry from the CRU loop 803 may be recycled back to the inlet of photocatalytic reactor 825. This may reduce the mass of clean adsorbent comprising TiO 2 required from reservoir 821. The amount of the TiO 2 slurry to be recycled back to reactor 825 and the amount of slurry 805 may be configured (e.g., optimized), according to some embodiments, to reduce the mass (e.g., kg / hr) of TiO 2 sent to the Cr 3< removal process while still maintaining discharge water 860 at or below a specified threshold (e.g., < 1ppb Cr 6< ).

[0049] Under some circumstances, the efficiency of the photocatalytic reduction of the Cr 6< to Cr 3< may decrease as the amount of Cr 3< adsorbing onto the TiO 2 increases due to reduction of available TiO 2 surface area. For example, batching a fixed mass of TiO 2 in a standard photocatalytic system may result in a continual loss of efficiency (e.g., where efficiency decreases as the surface of TiO 2 decreases), until the rate of chromium reduction in the photocatalytic reactor decreases to a point at which the Cr 6< in the effluent water would increase over the desired threshold (e.g., 1ppb Cr 6< ). At this point, all of the TiO 2 in the system would need to be removed and replaced with cleaned TiO 2 . This type of batch processing is difficult to operate and ensure that the Cr 6< discharge is maintaining its desired discharge specification at all times. FIGURE 16 shows the results of a batch TiO 2 pilot test that illustrates this trend. Chromium was detected with a portable device with a detection limit of 0.03ppm. Without limiting the disclosure to any particular mechanism of action, a fixed mass of TiO 2 in a Photo-Cat may decline in efficiency due to reduced surface area of the TiO 2 . Since this may be regarded as undesirable, system 800 may be operated, in some embodiments, in a manner that avoids this efficiency decay. For example, the flow rates of slurry reflux 803 and of slurry 805 to Cr 3< removal process may be maintained constant, thus the process will achieve 'steady state operation.' Steady state operation may provide consistent removal of the Cr 6< (i.e., chromium mass in = chromium mass out) and constant Cr 6< concentration in effluent 860.

[0050] As shown in FIGURE 15, slip stream 805 is sent to dewatering module 840 to further concentrate the adsorbent and contaminant. Stream 805 enters a dead-ended ceramic membrane oriented in a vertical position to concentrate the TiO 2 and Cr 3< slurry by another order of magnitude.

[0051] As the TiO 2 -Cr 3< slurry gets pumped into the dead end membrane, the TiO 2 -Cr 3< is filtered, and the filtered water is sent to discharge 806. Inside the membrane housing, the combination of gravity and air shock waves make the TiO 2 -Cr 3< solids drop down into a collection weir located immediately below the membrane. This process concentrates the TiO 2 -Cr 3< , and it also keeps the TiO 2 -Cr 3< from filling or plugging inside the ceramic membrane channels, keeping them free. The free channels provide consistent flux in the membrane(s), unlike most dead-end filters which accumulate the solids inside the filter itself (and thus flux continuously reduces). FIGURE 17 illustrates a weir in which the TiO 2 has dropped out after dead end filtration.

[0052] Once the weir is nearly full of TiO 2 -Cr 3< , a valve is opened and the mixture 807 passes into dewater / mixer tank 845, which is configured to perform one or more functions. The dewater / mixer tank 845 is configured to further dewater mixture 807. It may include dewatering membranes in some embodiments. Compressed air 817 from tank 836 may be used to push the TiO 2 -Cr 3< slurry into the dewatering membranes. The pressure pushes the water through the membranes and the treated water is sent to the discharge 810, while the dewatered TiO 2 -Cr 3< slurry is retained for further processing.

[0053] Dewater / mixer tank 845 is configured to add acid 808 from acid storage tank 850 to desorb contaminant (e.g., Cr 3< ) from adsorbent comprising TiO 2 . For example, a volume of heated (e.g., ~40 to ~60°C) sulfuric acid (e.g., ~1 wt.% - ~5 wt.%), may be added to dewater / mixer tank 845 where it may mix with dewatered Cr 3< -TiO 2 . In some embodiments, it may be desirable to avoid using a pump to move heated acid into dewater / mixer tank 845. Instead, it may be desirable to use compressed air 817 to push acid 808 into dewater / mixer tank 845. Once the acid is added, compressed air 817 is sent up through the bottom of dewater / mixer tank 845. The internal design of dewater / mixer tank 845 may be arranged to create small bubbles of air which flow up through the acid TiO 2 -Cr 3< mixture, providing significant mixing required to strip off the Cr 3< from the TiO 2 . The heated acid and agitation transfers the Cr 3< from the TiO 2 into the acid mixture. Tests show that this process may take about 20 to about 30 minutes. In some embodiments, it may be desirable to maintain the contents of acid storage tank 850 at constant free acid concentration (i.e., pH). In such cases, make-up acid 814 from make-up tank 849 may be added to tank 850.

[0054] Fluid mixture 809 may pass from dewater / mixer tank 845 into acid storage tank 850. Fluid mixture 809 may comprise or consist of acid (e.g., sulfuric acid) and contaminant (e.g., dissolved trivalent chromium). Compressed air 817 from tank 836 may be used to push fluid mixture 809 into acid storage tank 850.

[0055] The remaining TiO 2 in dewater / mixer tank 845 may be expected to have some acid with dissolved Cr 3< in it. The acid and dissolved Cr 3< must be flushed out of the TiO 2 before the TiO 2 can be sent to reservoir 821. The concentration of Cr 3< entrained in the TiO 2 mixture will be too high if this flush is not performed. Eventually the mass of contaminant (e.g., Cr 3< ) going back to reservoir 821 (and eventually back to photocatalytic reactor 825) will cause the total contaminant (e.g., chromium) concentration to exceed the desired threshold concentration (e.g., <20ppb chromium). (During pilot experiments, dissolved Cr 3< in the feed water was not observed to adsorb onto the TiO 2 . Instead, it only seemed to adsorb after Cr 6< reduction). A volume of treated water 810 is sent into dewater / mixer tank 845 and it is then pushed through the membrane (e.g., like stream 807 above) and placed in rinse water tank 855 via stream 812. Stream 812 may have a low pH (e.g., ~0.5 to ~3.0) and comprise dissolved Cr 3< .

[0056] Base 815 (e.g., NaOH) is then added to the rinse water tank 855 (from tank 854) to neutralize the water and precipitate the Cr 3< into Cr(OH) 3 . FIGURE 18 illustrates the low pH Cr 3< water after neutralization with NaOH to a pH of 8.5 (showing the Cr(OH) 3 precipitate). Testing showed that the total chromium can be precipitated from 26.8ppm down to 0.032ppm. Thus, the small volume of supernatant from rinse water tank 855 can be metered into discharge 813 without exceeding the desired threshold (e.g., <20ppb total chromium).

[0057] Precipitate 865 may be recovered by, for example, (a) gravity thickening and / or using ceramic membrane filtration and / or (b) using the dewatering approach used above. Chromium solid 816 is the recovered chromium, which can either be hauled away, or re-used in some other manufacturing process. If it is re-used, this remediation process could also be called a 'mining' process. In some embodiments, a decontamination process may have zero contaminated liquid discharge.

[0058] Once the TiO 2 has been flushed and dewatered, it is deemed 'clean', and treated water 810 is sent back to dewater / mixer tank 845 where the TiO 2 is slurried (required to transport it) and then sent back to the Clean TiO 2 Storage Tank for reuse via stream 811 using compressed air 817.

[0059] Persons skilled in the art may make various changes in the shape, size, number, and / or arrangement of parts within the scope of the claims. For example, the position and number of inlets, valves, fluid connections, tanks, reactors, and discharges may be varied. nlets, valves, fluid connections, tanks, reactors, and discharges may be interchangeable with like or different structures. Interchangeability may allow volume, flow rate, processing time, and yield to be custom adjusted. In addition, the size of a device and / or system may be scaled up (e.g., to be used for industrial embodiments) or down (e.g., to be used for portable embodiments) to suit the needs and / or desires of a practitioner.

[0060] Also, where ranges have been provided, the disclosed endpoints may be treated as exact and / or approximations as desired or demanded by the particular embodiment. Where the endpoints are approximate, the degree of flexibility may vary in proportion to the order of magnitude of the range. For example, on one hand, a range endpoint of about 50 in the context of a range of about 5 to about 50 may include 50.5, but not 52.5 or 55 and, on the other hand, a range endpoint of about 50 in the context of a range of about 0.5 to about 50 may include 55, but not 60 or 75. In addition, it may be desirable, in some embodiments, to mix and match range endpoints. Also, in some embodiments, each figure disclosed (e.g., in one or more of the examples, tables, and / or drawings) may form the basis of a range (e.g., depicted value + / - about 10%, depicted value + / - about 50%, depicted value + / - about 100%) and / or a range endpoint. With respect to the former, a value of 50 depicted in an example, table, and / or drawing may form the basis of a range of, for example, about 45 to about 55, about 25 to about 100, and / or about 0 to about 100.

Claims

1. A method for separating an intake fluid comprising a contaminant into a contaminant solid fraction and a discharge fluid fraction substantially free of the contaminant, the method comprising: (a) reducing the contaminant in a fluid reactor to form a reduced contaminant or oxidizing the contaminant to form an oxidized contaminant; (b) adsorbing the reduced contaminant or the oxidized contaminant to an adsorbent comprising TiO2 to form a contaminant-adsorbent material; (c) forming a fluid reactor output stream comprising the contaminant-adsorbent material; (d) fractionating up to all of the fluid reactor output stream in a catalyst recovery unit, CRU, (835) comprising a CRU porous membrane into a CRU retentate comprising the contaminant-adsorbent material and a CRU permeate substantially free of the contaminant, wherein the CRU permeate forms a first discharge stream; (e) fractionating the CRU retentate in a contaminant-concentrating module, DeWRS, (840) comprising a DeWRS porous membrane oriented in a vertical position, into a DeWRS retentate comprising the contaminant-adsorbent material and a DeWRS permeate substantially free of the contaminant, wherein the DeWRS permeate forms a second discharge stream; (f) gathering the contaminant-adsorbent material in the DeWRS retentate into a contaminant trap; (g) fractionating the gathered contaminant-adsorbent material in a contaminant-concentrating mixer tank (845) comprising a contaminant-concentrating mixer tank porous membrane into a contaminant-concentrating mixer tank retentate comprising the contaminant-adsorbent material and a contaminant-concentrating mixer tank permeate substantially free of the contaminant, wherein the contaminant-concentrating mixer tank permeate forms a third discharge stream; (h) adding, to the contaminant-concentrating mixer tank, acid from an acid storage tank (850) to the contaminant-concentrating mixer tank retentate comprising the contaminant-adsorbent material to form an acidified contaminant-concentrating mixer tank retentate; (i) mixing the acidified contaminant-concentrating mixer tank retentate in the contaminant-concentrating mixer tank to desorb the contaminant from the adsorbent and form a desorbed contaminant stream and a desorbed adsorbent stream; (j) optionally combining up to the entire desorbed stream into an intake stream; and (k) combining in a rinse tank (855) the desorbed contaminant stream with sufficient base to form a contaminant precipitate and a rinse water tank supernatant, wherein the rinse water tank supernatant forms a fourth discharge stream; wherein the contaminant precipitate forms the contaminant solid fraction and together each of the first discharge stream, the second discharge stream, the third discharge stream, and the fourth discharge stream form the discharge fluid fraction, and wherein the contaminant comprises at least one of chromium and hexavalent chromium.

2. The method according to claim 1, wherein reducing the contaminant in the fluid reactor to form the reduced contaminant further comprises photo reducing the contaminant.

3. The method according to claim 1, further comprising conveying make-up acid from a make-up acid storage tank (849) to the acid storage tank.

4. The method according to claim 1, wherein the base comprises sodium hydroxide.

5. The method according to claim 2, further comprising combining a portion of the fluid reactor output stream into the intake stream, wherein the portion of the fluid reactor output stream combined into the intake stream and a portion of the fluid reactor output stream fractionated in the catalyst recovery unit is maintained constant.

6. The method according to claim 1, wherein the concentration of the contaminant in the contaminant-adsorbent material in the CRU retentate is from 10 times to 20 times higher than the concentration of the contaminant in the contaminant-adsorbent material in the fluid reactor output stream.

7. The method according to claim 1, wherein the concentration of contaminant in the contaminant-adsorbent material in the DeWRS retentate is from 10 times to 20 times higher than the concentration of the contaminant in the contaminant-adsorbent material in the CRU retentate.

8. The method according to claim 1, further comprising conveying the DeWRS retentate in the contaminant-concentrating mixer tank retentate portion to the contaminant-concentrating mixer tank under pressure.

9. The method according to claim 1, wherein mixing the acidified contaminant-concentrating mixer tank retentate further comprises bubbling a gas through the contents of the contaminant-concentrating mixer tank retentate.

10. The method according to claim 1, wherein the acid is received by the contaminant-concentrating mixer tank at a temperature of 40oC to 60oC, at a concentration of up to 5 wt.%, and at a pH of less than 1.

11. The method according to claim 1, wherein the acid comprises sulfuric acid.

12. The method according to claim 1, wherein mixing the acidified contaminant-concentrating mixer tank retentate is done by bubbling a gas through the contents of the contaminant-concentrating mixer tank (845).