WO1997018166A2 - Direct osmotic concentration contaminated water - Google Patents
Direct osmotic concentration contaminated water Download PDFInfo
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- WO1997018166A2 WO1997018166A2 PCT/IB1996/001386 IB9601386W WO9718166A2 WO 1997018166 A2 WO1997018166 A2 WO 1997018166A2 IB 9601386 W IB9601386 W IB 9601386W WO 9718166 A2 WO9718166 A2 WO 9718166A2
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- water
- brine solution
- membrane
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/002—Forward osmosis or direct osmosis
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/002—Forward osmosis or direct osmosis
- B01D61/005—Osmotic agents; Draw solutions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/58—Multistep processes
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/025—Reverse osmosis; Hyperfiltration
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/14—Ultrafiltration; Microfiltration
- B01D61/145—Ultrafiltration
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/14—Ultrafiltration; Microfiltration
- B01D61/147—Microfiltration
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
- B01D61/422—Electrodialysis
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/445—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by forward osmosis
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/30—Wastewater or sewage treatment systems using renewable energies
- Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy
Definitions
- the present invention provides a process for direct osmotic concentration and processing for water recovery from highly contaminated streams.
- the process is especially well suited to situations where very high levels of water recovery are desired, and to streams which induce fouling in other processing technologies, such as streams with high salt and suspended solids, such as waste water, brackish water, and landfill leachate.
- High level water recovery allows for incineration ofthe residual sludge.
- Graywater makes a volume reduction difficult to accomplish by conventional means (e.g., reverse osmosis or evaporation).
- Graywater contains high levels of soap which causes rapid fouling in conventional systems, so that keeping systems in operation requires pretreatment ofthe waste and frequent equipment cleanings.
- evaporation is very energy intensive, and reverse osmosis is not capable of high levels of water recovery.
- Graywater has been treated by electrodialysis at sea to obtain a concentrated salt brine.
- the process of electrodialysis is energy intensive and difficult to run at sea. Therefore, there is a need in the art to develop less energy-intensive and more efficient treatment methods for graywater recovery that can be used, for example, at sea or in a space craft (e.g., space shuttle or space orbiter)
- a method for removing water from used OA is needed; water absorbed by the OA in the DOC process must subsequently be removed before the OA can be reused.
- Methods previously used to reconcentrate the OA include, thermal evaporation, solar evaporation, reverse osmosis, and electrodialysis In a thermal evaporator, water is boiled from the OA under vacuum This is the most common method for reconcentrating sugar OAs, however it is less desirable for salt OAs because of corrosion problems associated with heated salt solutions Thermal evaporation is also energy intensive; typically, about 750 BTU is used for every pound of water evaporated Solar evaporation is an attractive option in regions where the climate is favorable In this scheme, diluted salt brine is introduced to an open pond or tank, and incoming solar energy causes the water to evaporate.
- RO groundwater Reverse osmosis
- Electrodialysis is another membrane technology that can be used to reconstitute the salt brine.
- ED Electrodialysis
- a portion ofthe salt brine is totally deionized by electrically pulling all salt from it through ion-selective membranes into the remainder ofthe salt brine.
- ED is capital intensive and requires significant amounts of electricity to run.
- the present invention provides a method for recovering pure water from aqueous contaminated streams containing high levels of salts and suspended solids, comprising (a) contacting the aqueous stream with one side of a semipermeable membrane, the other side of which is in contact with an aqueous brine solution at a higher osmotic pressure, wherein the aqueous stream is provided at a pressure less than 350 kPa (e.g., 50 psi), whereby pure water passes through the membrane from the aqueous stream into the aqueous brine solution, and (b) recovering pure water from the aqueous brine solution by a reclamation procedure selected from the group consisting of (1) a reverse osmosis (RO) process, (2) an electrodialysis process, (3) an evaporation process, and (4) a combination thereof, thereby reconcentrating the aqueous brine solution.
- RO reverse osmosis
- the aqueous stream containing high levels of salts and suspended solids is selected from the group consisting of brackish water, surface water, well water, fish processing waste water, pulp and paper processing waste water, power plant discharge water, humidity condensate, sea water, and combinations thereof.
- the aqueous stream has a fluid velocity across the membrane surface greater than 0.15 m/sec to help sweep away fouling materials before they lodge on the membrane surface.
- the membrane is configured in a corrugated or tortuous flow design to augment turbulence.
- the salts include inorganic salts and organic salts.
- the aqueous brine solution is a concentrated or saturated solution of a chloride salt, such as sodium chloride, potassium chloride or calcium chloride.
- a chloride salt such as sodium chloride, potassium chloride or calcium chloride.
- the aqueous brine solution is recycled and reused.
- the recovering step is performed with RO to reconcentrate the aqueous brine solution.
- the present invention further provides a method for treating graywater or filtered blackwater, comprising (a) contacting the graywater or filtered blackwater with one side of a semipermeable membrane, the other side of which is in contact with an aqueous concentrated salt brine solution at a higher osmotic pressure, wherein the graywater or filtered blackwater is provided at a pressure less than 350 kPa (e.g., 50 psi), whereby pure water passes through the membrane from the graywater or filtered blackwater into the concentrated salt brine solution to dilute the concentrated salt brine and form a sludge of concentrated graywater or filtered blackwater at less than 5% of its original volume, (b) disposing ofthe graywater or filtered blackwater sludge, and (c) discarding the diluted salt brine into the ocean.
- kPa e.g., 50 psi
- the graywater or filtered blackwater treatment process is an energy efficient process utilizing the osmotic potential of a concentrated salt brine solution instead of an energy source, whereby the concentrated brine solution would normally be generated in a ship at sea during its normal desalination processes for obtaining potable water. Moreover, the concentrated salt brine generated during desalination would not be discardable unless diluted with potable water.
- the aqueous stream has a fluid velocity across the membrane surface greater than 0.15 m/sec to help sweep away fouling materials before they lodge on the membrane surface.
- the membrane is configured in a corrugated or tortuous flow design to augment turbulence.
- the present invention further provides a method for treating landfill leachate, comprising (a) contacting the leachate with one side of a semipermeable membrane, the other side of which is in contact with an aqueous brine solution at a higher osmotic pressure, wherein the leachate is provided at a pressure less than 350 kPa (e.g., 50 psi), whereby pure water from the leachate passes through the membrane into the aqueous brine solution, and (b) recovering pure water from the aqueous brine solution by a reclamation procedure selected from the group consisting of (1) a reverse osmosis (RO) process, (2) an electrodialysis process, (3) an evaporation process, and (4) a combination thereof, thereby reconcentrating the aqueous brine solution.
- RO reverse osmosis
- the leachate has a fluid velocity across the membrane surface greater than 0.15 m/sec to help sweep away fouling materials before they lodge on the membrane surface.
- the membrane is configured in a corrugated or tortuous flow design to augment turbulence.
- the landfill leachate is pretreated by a process selected from the group consisting of ultrafiltration, reverse osmosis, and combinations thereof whereby the pretreatment process is able to remove up to 80% of the water in landfill leachate but is not able to remove the much higher concentrations of water as the inventive process.
- the salts include inorganic salts and organic salts.
- the aqueous brine solution is a concentrated or saturated solution of a chloride salt, such as sodium chloride, potassium chloride or calcium chloride.
- the aqueous brine solution is recycled and reused.
- the recovering step is performed with RO to reconcentrate the aqueous brine solution.
- Examples of commercial applications ofthe inventive process are for recycling graywater on ships, recovering and reusing waste water at car washes and laundromats, treatment of boiler feed streams at power plants, and other areas where the supply of clean fresh water is limited Additional applications are to utilize brackish water as a potable water supply in an economical and energy-saving manner
- Figure 2 shows that the flux rates are constant over time indicating the lack of fouling using the inventive method when the highly contaminated aqueous stream used was made from 73% shower water, 22% ersatz humidity condensate and 5% untreated urine
- Figure 3 shows a schematic ofthe inventive DOC process with an RO system to reconstitute the salt brine solution
- Figure 4 shows flux rates over time for graywater treatment using seawater as the O A/slat brine solution
- Figure 5 shows the same experiment as Figure 4 (reported in example 1) only using a more highly concentrated salt brine solution of 7 wt% NaCl OA instead of seawater Again, the flux rates over time indicate a lack of fouling using the inventive process
- Figure 6 illustrates a process flow diagram showing the inventive method
- Figure 7 illustrates a bench top version of a DOC device
- Figure 8 illustrates a schematic of mass balances for water recovery from the ersatz waste model described herein
- Figure 9 illustrates the water removal rate from the ersatz waste water and is representative of water permeation rate at a given fraction of water recovered
- flux rates are plotted as LMH versus an average ofthe fraction of water removed at the beginning and end of a sample interval The flux rate decreased as the amount of water recovered increased This was due to an increase in osmotic pressure ofthe waste solution as the solids became more concentrated
- Figure 10 illustrates the performance of chloride-containing salts
- the upper panel shows the rate of water uptake versus the number molarity ofthe salt
- the number molarity is the moles of ions, assuming complete dissociation ofthe salts, in a kg of water
- the abscissa is the average ofthe beginning and ending samples for the time interval
- the lower panel was the last series of runs, which indicated that there was a decline in membrane flux- performance during the initial screening tests
- Figure 10 shows the kg of salt lost from the brine solution into tap water for each kg of water removed
- the actual salt-loss rate was determined by multiplying by the flux rate of water removed
- the salt-loss tended to be less than 0 1% ofthe water-removal rates
- Figure 11 illustrates the effect ofthe anion of DOC performance
- Figure 11 assumes complete dissociation ofthe salts If sodium citrate and sodium sulfate are assumed to have only one Na + dissociate, then they would lie on the same trend as sodium chloride and sodium acetate Figure 11 shows the kg of salt lost from the brine solution into the waste (tap water) for each kg of water removed. Sodium chloride exhibited the largest salt-loss rate for the sodium series, but it was less than 0.05% ofthe water removal rates.
- Figure 12 illustrates a two-stage DOC system experimental set up. There were no back pressure valves used on the waste side because the waste tank was elevated, which provided a needed 7-14 kPa pressure differential between the waste and the brine solution.
- the feed i.e., waste
- the feed was fed into a first Stage as water diffused through the membrane into the brine solution. Water that diffused through a second stage membrane into the brine solution was automatically replaced by partially concentrated from Stage 1.
- the concentrated waste was manually withdrawn from Stage 2 at various times for analysis.
- the brine solution was set up to flow in a countercurrent to the waste flow.
- FIG. 13 illustrates an electrodialysis (ED) test system.
- Figure 14 illustrates the mass balance for continuous processing of waste water.
- Figure 15 illustrates water removal rates from actual composite waste water. Flux results are plotted in Figure 15. Flux declined by approximately 10% during a run, but this was due to feed strength ofthe brine solution dropping by about 20%.
- the present invention uses osmosis through a semipermeable membrane to provide a method for removing water from contaminated aqueous streams.
- the invention is capable of removing up to 98% ofthe water from highly contaminated feed streams that tend to cause rapid fouling of other membrane evaporation systems (e.g., RO, evaporation, etc.).
- the invention is particularly useful in situations where a high level of water recovery is desired and the feed stream causes rapid fouling of other membrane or evaporation systems, ln addition, the invention has the capability of processing fluids containing high levels of suspended solids with no pretreatment.
- RO reverse osmosis
- direct osmosis is used to extract water from a contaminated stream by introducing the stream to one side of a semipermeable membrane and an "osmotic agent" (a solution with a higher osmotic potential, such as a salt brine solution) to the other side. Because ofthe difference in osmotic potential, water diffuses through the membrane from the feed into the osmotic agent.
- osmotic agent a solution with a higher osmotic potential, such as a salt brine solution
- Osmotic potential is a measure of how strongly a solution draws water through a semipermeable membrane
- Osmotic agents used in the inventive process are preferably salt solutions
- Such salt solutions or brines include but are not limited to solutions containing Na + , K + , Ca 4-1" , Mg “4-1” , Li + , Cl", SO4", or organic anions such as ascorbate, citrates or large polyelectrolytes
- the osmotic agent, or salt brine solution can also be seawater or salt brines from industrial or desalination processes
- Osmotic agent made from non-ionic solutions e.g., sugars
- the flux is slower that the flux for ionic species
- Membranes used in the present invention are preferably highly hydrophilic and highly selective.
- Typical membrane materials are polyvinyl alcohol-derivatives and cellulose-based polymers, such as cellulose acetate, cellulose triacetate, cellulose butyrate, and cellulose propionate. These membranes absorb water from the waste into the polymer matrix while rejecting larger molecules The absorbed water diffuses through the polymer into the osmotic agent or salt brine solution Water transfer rates increase with thinner membranes Direct Osmosis Concentration (DOC) is used to concentrate a waste stream for storage or processing, or it can be used as a "foulant-eliminating" pretreatment step in the desalination of water.
- DOC Direct Osmosis Concentration
- An attractive feature ofthe invention is it can extract a much higher percentage of water from a solution than reverse osmosis
- RO reverse osmosis
- water is forced from a solution through a membrane by exerting high pressures on the fluid (up to 7 MPa, or 1000 psi).
- the inventive process is attractive in four situations
- the first is instances where a waste needs to be concentrated, and an existing source of brine is available
- An example of this is shipboard concentration of graywater
- sea water or brine from the ship's desalination system is be used as the brine solution
- the brine does not need to be reconcentrated after absorbing water, the waste concentration requires less energy consumption than evaporation or reverse osmosis
- the second situation occurs when a waste needs to be concentrated and fouling makes other technologies inappropriate
- An example of this is removal of water from chemical process solutions before incineration In this case, the water absorbed by the brine is often removed by evaporation so the brine is reused
- the present inventive process is most useful for on site treatment of landfill leachate
- the inventive process can remove about 95% or even greater concentrations of potable water from even hazardous leachates, whereas RO systems can effectively remove only about 80% of water reliably from leachates with high suspended solids concentrations
- the inventive process involves a
- the invention is attractive as a pretreatment to remove foulants from a stream before desalination
- DOC is used to produce a stream of higher salinity but lower hardness.
- the low hardness stream is desalinated by electrodialysis, reverse osmosis, or evaporation
- the removal of potable water also reconcentrates the brine for reuse
- An example of this is the recovery of high levels of water from brackish water in arid regions
- the inventive process is distinct from prior art water recovery processes because of high levels of water recovery and a resistance to membrane fouling
- Figure 2 shows the water flux from graywater when the osmotic agent and product concentrations are held constant. This demonstrates that the inventive process is not subject to fouling induced flux declines experienced by other membrane processes when processing graywater.
- the first requirement is low pressure, particularly having the feed pressure be lower than 350 kPa (about 50 psi), preferably lower than 140 kPa (20 psi).
- Other membrane processes, such as RO operate above 400 psi, which induce rapid formation of fouling layers on the membrane.
- a system operating at such low pressures can be made from molded plastics allowing for much less expensive designs and reduced capital costs due to the need for less expensive pumps that only operate at lower pressures.
- the fluid velocity is preferably pumped across the membrane surface at velocities above 0.15 m sec.
- the cell design preferably, has a tortuous or corrugated flow path, such as the design described in U.S. Patent 5,281,430, the disclosure of which is inco ⁇ orated by reference herein.
- Osmotic agents (OA) or aqueous brine solutions used herein preferably are available (e.g., seawater) or continuously reconcentrated.
- Methods for reconcentrating the aqueous brine solution include, for example, RO, evaporation, electrodialysis, and combinations thereof. A preferred scheme is shown in Figure 3.
- the present invention provides a method for recovering pure water from aqueous contaminated streams containing high levels of salts and suspended solids, comprising (a) contacting the aqueous stream with one side of a semipermeable membrane, the other side of which is in contact with an aqueous brine solution at a higher osmotic pressure, wherein the aqueous stream is provided at a pressure less than 350 kPa (e.g., 50 psi), whereby pure water passes through the membrane from the aqueous stream into the aqueous brine solution, and (b) recovering pure water from the aqueous brine solution by a reclamation procedure selected from the group consisting of (1) a reverse osmosis (RO) process, (2) an electrodialysis process, (3) an evaporation process, and (4) a combination thereof, thereby reconcentrating the aqueous brine solution.
- RO reverse osmosis
- the aqueous stream containing high levels of salts and suspended solids is selected from the group consisting of brackish water, surface water, well water, fish processing waste water, pulp and paper processing waste water, power plant discharge water, humidity condensate, sea water, and combinations thereof
- the aqueous stream has a fluid velocity across the membrane surface greater than 0.15 m/sec to help sweep away fouling materials before they lodge on the membrane surface.
- the membrane is configured in a corrugated or tortuous flow design to augment turbulence.
- the salts include inorganic salts and organic salts.
- the aqueous brine solution is a concentrated or saturated solution of a chloride salt, such as sodium chloride, potassium chloride or calcium chloride.
- a chloride salt such as sodium chloride, potassium chloride or calcium chloride.
- the aqueous brine solution is recycled and reused.
- the recovering step is performed with RO to reconcentrate the aqueous brine solution.
- the present invention further provides a method for treating graywater or filtered blackwater, comprising (a) contacting the graywater or filtered blackwater with one side of a semipermeable membrane, the other side of which is in contact with a concentrated aqueous brine solution at a higher osmotic pressure, wherein the graywater or filtered blackwater is provided at a pressure less than 350 kPa (e.g., 50 psi), whereby pure water passes through the membrane from the graywater or filtered blackwater into the concentrated aqueous brine solution to dilute the concentrated aqueous brine and form a sludge of concentrated graywater or filtered blackwater at less than 5% of its original volume, (b) disposing ofthe graywater or filtered blackwater sludge, and (c) discarding the diluted aqueous brine into the ocean.
- kPa e.g., 50 psi
- the graywater or filtered blackwater treatment process is an energy efficient process utilizing the osmotic potential of a concentrated aqueous brine solution instead of an energy source, whereby the concentrated aqueous brine solution would normally be generated in a ship at sea during its normal desalination processes for obtaining potable water. Moreover, the concentrated aqueous brine generated during desalination would not be discardable unless diluted with potable water.
- the aqueous stream has a fluid velocity across the membrane surface greater than 0.15 m/sec to help sweep away fouling materials before they lodge on the membrane surface.
- the membrane is configured in a corrugated or tortuous flow design to augment turbulence.
- Examples of commercial applications ofthe inventive process are for recycling graywater on ships, recovering and reusing waste water at car washes and laundromats, treatment of boiler feed streams at power plants, and other areas where the supply of clean fresh water is limited. Additional applications are to utilize brackish water as a potable water supply in an economical and energy-saving manner.
- the inventive process as applied to graywater on a ship at sea, also avoids the high cost of electrodialysis, providing that RO is used for the recovering step.
- the inventive process recovers over 98% ofthe water from most sources containing high levels of salts (e.g., calcium and magnesium hardness, bicarbonates/alkalinity, barium or strontium sulfate, fluorides, chlorides, silica, iron, and organics, including long chain hydrocarbons).
- salts e.g., calcium and magnesium hardness, bicarbonates/alkalinity, barium or strontium sulfate, fluorides, chlorides, silica, iron, and organics, including long chain hydrocarbons.
- the process is suitable for zero or minimum discharge operations in the treatment of municipal or industrial waste waters.
- the inventive process provides a more economical, or in some cases, an only alternative for treatment of waste waters containing high levels of suspended solids.
- the inventive process is suitable for boiler feed water pretreatment, specifically at those sites where high levels of silica in the raw water could hinder the performance of high pressure boilers in the electric power industry.
- Membranes used in the invention are preferably hydrophilic and have molecular selectivity's similar to those of reverse osmosis membranes. Examples of such membranes are cellulose-based asymmetric membranes and hydrophilic thin-film composite membranes.
- Membrane configurations which may be used for DOC include, but are not limited to, hollow fiber, spiral wound, plate-and-frame and tubular Plate-and-frame and tubular configurations are preferable in many applications as they are more tolerant of high levels of suspended solids.
- Aqueous brine solutions useful in the process include but are not limited to inorganic and organic salt solutions, sugar solutions, and polyelectrolyte solutions.
- aqueous brine solution The selection of the aqueous brine solution is determined by solubility's, osmotic strength of solutions, permeability ofthe osmotic agent through the membrane, and economics.
- an effective osmotic agent (OA) or aqueous brine solution has high diffusivity, high solubility, and low molecular weight ofthe dissolved species.
- High diffusivity is desirable because water being drawn through the membrane tends to sweep the OA salts away from the membrane surface. This reduces the brine strength at the surface, and reduces the water removal rate.
- a high diffusivity quickly replenishes the aqueous brine salts at the surface.
- High solubility and low molecular weight ofthe dissolved salts in the aqueous brine solution are desirable because the osmotic potential ofthe solution is roughly proportional to the number density of dissolved molecules.
- a light, highly soluble salt such as sodium chloride gives the fastest water removal rates.
- sugar and polyelectrolyte solutions may be used as the osmotic agent.
- Salt contamination can occur because DOC membranes are not 100% impermeable to light salts. For example, when a sodium chloride osmotic agent and a cellulose triacetate membrane are used, approximately 0.1 to 1.0 mg of salt crosses from the osmotic agent into the feed for every kilogram of water extracted. DOC membranes completely block larger species such as sugars and polyelectrolytes However osmotic agents using these larger species of OA deliver lower fluxes than those obtained with light salts
- the inventive method was tested with a variety of aqueous streams containing high levels of salts and suspended solids to recover essentially pure water
- the first step ofthe inventive process is a direct osmotic concentration (DOC) ofthe aqueous stream
- DOC direct osmotic concentration
- water is recovered from the contaminated aqueous stream by placing the aqueous stream and a clean, concentrated aqueous brine solution on opposite sides of a membrane
- the membrane is, preferably, a semipermeable membrane, allowing water passage and rejecting the passage of all but the smallest compounds
- the concentrated salt solution is called an aqueous brine solution because it has a higher osmotic potential than the aqueous stream
- a 15 weight percent NaCl solution as an aqueous brine solution has an osmotic potential of 16 MPa (2300 psi)
- the DOC process step is nonfouling (irrespective ofthe level of suspended solids present in the aqueous stream) because there are
- the clean, diluted aqueous brine solution is reconstituted in the second step to yield recovered potable water and concentrated salt solution as reusable aqueous brine solution
- This reconstitution step can be accomplished by evaporation, electrodialysis, RO, and combinations thereof
- electrodialysis was used for the reconstitution step
- a process flow diagram shows the inventive method in Figure 6 Therefore, the aqueous brine solution essentially acts as a carrier for clean, potable water
- the regenerated concentrated aqueous brine solution is recycled to act as the OA or aqueous brine solution
- DOC direct osmotic concentration
- the aqueous brine solution is a concentrated or saturated solution of a chloride salt, such as sodium chloride, potassium chloride or calcium chloride
- a chloride salt such as sodium chloride, potassium chloride or calcium chloride
- the aqueous brine solution is recycled and reused
- Figure 10 shows the performance of chloride-containing salts
- the upper panel shows the rate of water uptake versus the number molarity ofthe salt.
- the number molarity is the moles of ions, assuming complete dissociation ofthe salts, in a kg of water
- the abscissa is the average ofthe beginning and ending samples for the time interval.
- the recovering step is performed with reverse osmosis (RO) as more economical than electrodialysis, or the recovering step is performed with both RO and electrodialysis.
- RO reverse osmosis
- Example 1 This example illustrates the preparation of an ersatz waste stream that was used as a model for testing treatment of gray water.
- the composition of this model gray water approximated the salt levels, TOC (total organic carbon), and major chemical constituents of a combination of urine and shower, hygiene and laundry waste water.
- the components are listed in Table 1.
- Table 1 Composition of Automatic Waste Water
- An actual waste water stream was further composed of 72.8% by volume shower, hygiene and laundry water (obtained from Umpqua Research Company (Myrtle Creek, OR)), 21.7% humidity condensate (made by diluting one part ersatz condensate concentrate (Umpqua) with nine parts of distilled water), and 5.5% untreated urine from a male volunteer.
- the analysis of this waste water stream was 525 mg/l TOC, 184 mg/l Na + , 259 mg/l K + , 7.33 mg/l Ca ++ , and 4.71 mg/l Mg "1""1" .
- the graywater of Table 1 was concentrated as a 30 liter batch in a laboratory-scale cell having a membrane area of 0.07 m ⁇ .
- Sodium chloride brines were used and brine concentrations were maintained by adding salt to the brine tank.
- Figures showing flux versus time and percent recovery are provided in Figures 4 and 5, respectively.
- Membranes used were asymmetric cellulose triacetate membranes cast by immersion precipitation on a net backing. Total membrane thickness was 170 microns. The membranes had selectivities similar to those of reverse osmosis membranes and the biological oxygen demand of water passing through the membrane was measured to be less than 1 ppm in each run.
- Example 2 This example describes an experiment to evaluate several membranes within a bench- top DOC device to determine flux rates and performance criteria for several membranes.
- the DOC device is described in United States Patent 5,281,430, the disclosure of which is inco ⁇ orated by reference herein.
- the bench top version of this device is illustrated in Figure 7.
- the waste water was sandwiched between a pair of membranes which separate the waste from the aqueous brine solution, which flows in the end plates.
- the membranes and plates can be stacked like plate-and-frame heat exchangers, however in this experiment, only one pair of membranes was used.
- the cell dimensions were 0.30 x 0.23 x 0.06 m and each membrane was 0.28 x 0.20 m.
- the effective transfer area was approximately 0.23 x 0.15 m or about 0.07 m ⁇ for the two membranes.
- the cell was plumbed with all necessary valves, gauges and tubing, and leak tested
- the membranes tested included cellulose triacetate (backed and unbacked) (Purification Products), cellulose acetate (Purification Products), Nafion® 112 (DuPont), and SW-30 aromatic polyamide (FilmTec)
- the initial membrane screenings were done with a 13 to 15 weight percent NaCl solution as the brine solution and either tap water or dilute com syrup as the waste Flux rates were determined by measuring the change in volume ofthe tap water
- the amount of salt lost into the waste was determined by measuring conductivity ofthe tap water or diluted com syrup and then accounting for the measured change in the amount ofthe waste Table 2 shows the results from initial screenings with tap water
- the Nafion® membrane was not tested with tap water as the waste, however when com syrup was used, Nafion® performed just as poorly as the SW-30 membrane Flux rates are shown in LMH (liters of water removed per square meter of effective membrane area per hour) Salt-loss ratio estimates are how many kg of salt are transferred from the brine solution into waste for every kg of water diffusing in the opposite direction (i.e., from waste into the brine solution)
- This example reports an experiment to evaluate the merits of various brine solutions for waste water treatment.
- Seven soluble salts were selected for inco ⁇ oration as the brine solution, including NaCl, LiCl, KCl and CaCl 2 for cation effects and Na 2 SO 4 , NaC 2 H 3 O 2 (sodium acetate), and Na 3 C6H 5 O 7 (sodium citrate) for anion effects.
- Tap water, CTA membranes and 15% by weight salts were used for salt comparisons.
- the DOC setup was the same used in example 2 above. Rejection rate of salt by the membrane was determined by measuring conductivity change due to concentrating water so that salt rejection rate ofthe membrane could be calculated.
- FIG 11 shows the kg of salt lost from the brine solution into the waste (tap water) for each kg of water removed.
- Sodium chloride exhibited the largest salt-loss rate for the sodium series, but it was less than 0.05% ofthe water removal rates. Its ratio was the largest because chloride is the smallest solvated anion ofthe series: chloride ⁇ sulfate ⁇ acetate ⁇ citrate.
- sodium chloride is a desirable brine solution because of its solubility, it is strongly rejected by the membrane, suitable for electrodialysis recovery, nontoxic at low levels, and the anion and cation are each soluble with most ofthe contaminants that may get into the brine solution.
- Example 4 This example presents the results of integrated testing of a DOC/ED process.
- CTA membrane and a sodium chloride osmotic agent were used.
- a two-Stage DOC system was set up, as shown in Figure 12. There were no back pressure valves used on the waste side because the waste tank was elevated, which provided a needed 7-14 kPa pressure differential between the waste and the brine solution.
- the feed i.e., waste
- the waste was fed into a first Stage as water diffused through the membrane into the brine solution.
- the waste was fed into a first Stage ( Figure 12) as water diffused through the a first Stage membrane into the brine solution.
- Water that diffused through a second stage membrane into the brine solution was automatically replaced by partially concentrated waste from Stage 1.
- the concentrated waste was manually withdrawn from Stage 2 at various times for analysis.
- the brine solution was set up to flow countercurrent to the waste flow.
- the NaCl concentration in Stage 1 was 4-5 wt% and in Stage 2 was 6-8 wt%.
- This experiment used an Ionics Mark I electrodialysis stack with a setup shown in Figure 13.
- the anode was platinum-coated titanium and the cathode was stainless steel.
- Two different power supplies were used, a Miller XMT-300CC DC Inverter Arc Welder for constant-amp currents above 6 A, and an ACDC Electronics Power Supply (Model OEM24N5.4-9) that delivered approximately 30 W with a maximum voltage of 22 v.
- the following membranes were used in the ED stack: cation-61-AZL-389 (Ionics) a cation- permeable membrane to isolate the electrode-rinse solutions, cation-64-LMP-401 (Ionics), and anion-204-UZL-386 (Ionics).
- the membranes were rated to handle the high concentrations of salts that were produced by regeneration ofthe brine solution.
- Flux results are plotted in Figure 15. Flux declined by approximately 10% during a run, but this was due to osmotic strength ofthe aqueous brine solution dropping by about 20%.
- the final 3 days had concentrations of about 12 wt% NaCl Approximately 20% of the membrane for Stage 2 was covered with a precipitate at the end ofthe 9 days. This precipitate was removed by a simple flush with unconcentrated hygiene water. No precipitate was formed on the Stage 1 membrane.
- TOC concentrations ofthe concentrate produced in ED were the same as deionized water. This means that TOC levels were not due to dissociated organic compounds, because they would have partitioned during ED. Initially we had 525 mg/l TOC, so the rejection of TOC was 70%. Further analysis showed that most ofthe TOC in recovered water was from urea, while the membrane rejected most ofthe other organics.
- Water recovery rates are shown in Figure 17 and the analysis of recovered water is shown in Table 4.
- the water was not deionized to less than 100 ⁇ S/cm because (1) the system was operated in a batch mode with a final salt concentration of 14.5 wt% (the concentrate can only be made to about 15-16 wt% with the bulk ofthe water ending up in the concentrate with diluant running out), and (2) there was sodium aluminosilicate present in the initial salt, which was too large to diffuse through the ED membranes. In a continuous run, these issues can be overcome without undue experimentation, with a better salt source to achieve deionization levels of less than 100 ⁇ S/cm.
- Example 5 This example illustrates a system requirement for an enclosed module (vehicle, space shuttle, etc.) with a four person crew. Larger or smaller modules will have their system designs adjusted proportionately. Assuming 97% recovery of waste water and 31.5 1 per person per day (combination of laundry/shower/hygiene water, humidity condensate, and untreated urine), 18 hr of operation per day, the basic DOC system is two 0.5 m 2 modules in series with continuous dilute feed, 0.3 x 0.23 x 0.15 m per module and four peristaltic pump heads plus a drive with each capable of 12 /pm at 20 kPa.
- the basic ED system is three modules in series with 0.5-, 0.5-, and 0.25 m 2 effective membrane area with a physical dimension of 0.3 x 0.23 x 0.23 m for each 0.5 m 2 stage and 0.3 x 0.23 x 0.18 m for the 0.25 m 2 stage, plus six peristaltic pump heads plus a drive, each capable of 1 /pm at 30 kPa, and one 30 v DC power supply with 400 W output.
- the energy requirements are 24 W for DOC pumping, 3 W for ED pumping and 400 W for ED DC power for a total of 427 W/(6.8 1/hr), which is 63 W/kg water recovered.
- This example illustrates an experiment to determine if potable water can be obtained from a brackish ground water yielding high percent recoveries by using direct osmosis concentration (DOC), and to estimate costs of water production from a specified feed stream using this method.
- DOC direct osmosis concentration
- DOC is not a "stand alone” technology in this application, but is used in conjunction with ion-exchange, and electrodialysis or evaporation.
- the DOC process could also be used as a pretreatment to control the problems presented by the high levels of calcium and magnesium in the water.
- This experiment evaluated the DOC portion ofthe process only.
- the secondary technologies, electrodialysis of sodium chloride and ion exchange are known and their performance and cost can be easily determined.
- High quality potable water was produced from brackish ground water by coupling
- the electrodialysis step can be replaced with a multiple effect evaporator.
- Run #2 A further run was made in a smaller cell with the brackish concentrate from the first run.
- Membrane Area 0.33 ⁇
- Run #3 The small cell was run on the following morning and the water extraction rates were identical to those of Run #2 the previous day.
- This example illustrates laboratory testing for sizing a pilot-scale apparatus performing the inventive DOC process to provide on-site treatment of landfill leachate at a landfill site.
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Abstract
Description
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AU76375/96A AU7637596A (en) | 1995-11-14 | 1996-11-14 | Direct osmotic concentration contaminated water |
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US55785295A | 1995-11-14 | 1995-11-14 | |
US08/557,852 | 1995-11-14 |
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WO1997018166A2 true WO1997018166A2 (en) | 1997-05-22 |
WO1997018166A3 WO1997018166A3 (en) | 1997-07-03 |
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Cited By (16)
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WO2005012185A1 (en) * | 2003-07-30 | 2005-02-10 | University Of Surrey | Solvent removal process |
WO2006047577A1 (en) * | 2004-10-25 | 2006-05-04 | Cascade Designs, Inc. | Forward osmosis utilizing a controllable osmotic agent |
NL1028484C2 (en) * | 2005-03-08 | 2006-09-11 | Kiwa Water Res | Treating a wastewater stream from a bioreactor comprises immersing a membrane filtration unit in the wastewater stream |
US7416666B2 (en) | 2002-10-08 | 2008-08-26 | Water Standard Company | Mobile desalination plants and systems, and methods for producing desalinated water |
NL1035431C2 (en) * | 2007-06-29 | 2009-11-04 | Water En Energiebedrijf Aruba | Hybrid osmosis reverse osmosis process for desalination of seawater, involves passing diluted effluent sodium chloride solution through semi-permeable membrane such that pure water and concentrated seawater are separated |
WO2009037515A3 (en) * | 2007-09-20 | 2010-04-08 | Abdulsalam Al-Mayahi | Process and systems |
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US7749386B2 (en) * | 2001-12-31 | 2010-07-06 | Poseidon Resources Ip Llc | Desalination system |
US20110198208A1 (en) * | 2008-11-07 | 2011-08-18 | Deutsches Zentrum Fur Luft-Und Raumfahrt E.V. | Method for desalinating water containing salt |
WO2011136722A2 (en) * | 2010-04-26 | 2011-11-03 | Airwatergreen Ab | Desalination device |
EP1894612B1 (en) * | 2006-09-01 | 2013-10-02 | Vitens Friesland | Method for purifying water by means of a membrane filtration unit |
US8696908B2 (en) | 2009-05-13 | 2014-04-15 | Poseidon Resources Ip Llc | Desalination system and method of wastewater treatment |
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US7416666B2 (en) | 2002-10-08 | 2008-08-26 | Water Standard Company | Mobile desalination plants and systems, and methods for producing desalinated water |
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WO2005012185A1 (en) * | 2003-07-30 | 2005-02-10 | University Of Surrey | Solvent removal process |
CN103435129A (en) * | 2003-07-30 | 2013-12-11 | 萨里水溶剂科技有限公司 | Solvent removal process |
CN1856447B (en) * | 2003-07-30 | 2013-09-25 | 萨里水溶剂科技有限公司 | Solvent removal process |
US8221629B2 (en) | 2003-07-30 | 2012-07-17 | Surrey Aquatechnology Limited | Solvent removal process |
US7879243B2 (en) | 2003-07-30 | 2011-02-01 | Surrey Aquatechnology Limited | Solvent removal process |
AU2004261474B2 (en) * | 2003-07-30 | 2010-12-16 | Surrey Aquatechnology Limited | Solvent removal process |
WO2006047577A1 (en) * | 2004-10-25 | 2006-05-04 | Cascade Designs, Inc. | Forward osmosis utilizing a controllable osmotic agent |
NL1028484C2 (en) * | 2005-03-08 | 2006-09-11 | Kiwa Water Res | Treating a wastewater stream from a bioreactor comprises immersing a membrane filtration unit in the wastewater stream |
EP1894612B1 (en) * | 2006-09-01 | 2013-10-02 | Vitens Friesland | Method for purifying water by means of a membrane filtration unit |
NL1035431C2 (en) * | 2007-06-29 | 2009-11-04 | Water En Energiebedrijf Aruba | Hybrid osmosis reverse osmosis process for desalination of seawater, involves passing diluted effluent sodium chloride solution through semi-permeable membrane such that pure water and concentrated seawater are separated |
WO2009037515A3 (en) * | 2007-09-20 | 2010-04-08 | Abdulsalam Al-Mayahi | Process and systems |
GB2464956A (en) * | 2008-10-31 | 2010-05-05 | Apaclara Ltd | Water purification method using a field separable osmotic agent |
US20110198208A1 (en) * | 2008-11-07 | 2011-08-18 | Deutsches Zentrum Fur Luft-Und Raumfahrt E.V. | Method for desalinating water containing salt |
WO2010067065A1 (en) * | 2008-12-08 | 2010-06-17 | Surrey Aquatechnology Limited | Improved solvent removal |
AU2009326257B2 (en) * | 2008-12-08 | 2015-06-11 | Surrey Aquatechnology Limited | Improved solvent removal |
US8696908B2 (en) | 2009-05-13 | 2014-04-15 | Poseidon Resources Ip Llc | Desalination system and method of wastewater treatment |
WO2011136722A3 (en) * | 2010-04-26 | 2011-12-15 | Airwatergreen Ab | Desalination device |
WO2011136722A2 (en) * | 2010-04-26 | 2011-11-03 | Airwatergreen Ab | Desalination device |
CN103910397A (en) * | 2014-03-19 | 2014-07-09 | 首钢京唐钢铁联合有限责任公司 | Recondensation apparatus of concentrated seawater |
CN103910397B (en) * | 2014-03-19 | 2016-08-17 | 首钢京唐钢铁联合有限责任公司 | Concentrated seawater reconcentration device |
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Also Published As
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AU7637596A (en) | 1997-06-05 |
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