Symbiotic reverse osmosis for maximizing desalinated water recovery from saline waters and brines

Abstract

The present application comprises symbiotic reverse osmosis train system for maximizing desalinated water recovery, meanwhile yielding high salinity brine suitable for osmotic power generation or commercial salt production; trains comprise series of number of cells operating in interrelated sequential pattern within a salinity field. Each cell forms a closed hydraulic brine loop having pumping means, power recovery means and shared semipermeable membranes between adjacent cells, defining the boundaries of flow path within a given cell, using applicant's technology for semipermeable Flat Sheet Membranes [FSM] or Hollow Fiber Membranes [HFM] intended for new and novel development in Hypersalinity processes and applications in desalination and osmotic power generation of brackish, seawater and brines of 15% salinity or more. Charging each cell in the train of plurality of cells with a formulated brine having a specified ionizable inorganic salt concentration and type, without permitting mixing of the given brines among the adjacent cells in the plurality of cells, allowing the train of multiple cells to achieve water recovery exceeding 85% with concentrated rejected brine of 28-30% salt content that is recoverable by evaporation/crystallization for commercial use. Highlighting, the first of its kind, a large scale Seashore Tower of flat Sheet membrane [FSM] for Induced Osmotic Desalination Plant of a capacity 28-56 million cubic meter per year (15 billion gallons per year) at a recovery rate of 85%, and rejected brine salinity of 28-30%, either used for sodium chloride salt recovery of 1-2 million metric tons per year, or to generate Induced Osmotic Power of 25-50 MW.

What is claimed is: 
     
         1 . A method for a symbiotic reverse osmosis system, comprising:
 providing a reverse osmosis train having a plurality of cells including an initial end cell of conventional reverse osmosis type, one or more intermediate cells, and an opposed end cell of symbiotic reverse osmosis type, each cell in the plurality of cells forming a hydraulic loop configured of specified volumetric capacity and flow rate for a specified permeate flux, each cell in the plurality of cells also having a pumping system and a hydro-power generation turbine system or pressure exchanging means for optimizing power consumption as well as flow and salinity measurements & control, pressure and temperature measurements means, and automated backflush;   wherein adjacent cells in the plurality of cells share an enclosed panel of one or more semipermeable membranes, where said membranes are of the hollow fiber or flat sheet membrane configuration, simultaneously functioning in a symbiotic pattern; and   wherein the Symbiotic Reverse Osmosis process overcomes the limitations of conventional, single cell, polymeric membrane technologies for seawater desalination (3.5% salinity), when such conventional membranes are subjected to high operating pressure generally exceeding 1,100 psi (75.8 bar) by operating said membrane against rejected brine of a salinity exceeding 7%, consequently causing its pre-mature failure, just for recovering about 50% desalinated water.   
     
     
         2 . The method of  claim 1 , wherein the proposed Symbiotic Reverse Osmosis process employs a train of more than one cell, forming a cascade of membrane cells comprising the same conventional polymeric membranes, where each membrane cell is operated within a maximum concentration differential of less than 7% and preferably with concentration differential of 4%-5%, allowing the train of multiple cells to achieve water recovery exceeding 85% with concentrated rejected brine of 28-30% salt content that is recoverable by evaporation/crystallization for commercial use. 
     
     
         3 . The method of  claim 1 , wherein the membrane panels are of hollow fiber [HFM] configuration. 
     
     
         4 . The method of  claim 1 , further comprising:
 charging each cell in the train of plurality of cells with a formulated brine having a specified ionizable inorganic salt concentration and type, without permitting mixing of the given brines among the adjacent cells in the plurality of cells, creating a gradient of salt concentration and resulting in osmotic potential that progressively decreases stepwise from the train's initial end cell, then across the train of the intermediate cells, to the opposed end cell.   
     
     
         5 . The method of  claim 4 , wherein the brine in the inaccessible intermediate cells, and the opposed end cell of desalination train is generally formulated from sodium chloride, without any trace of insoluble material such as at least one of calcium carbonate, and barium sulfate salts. 
     
     
         6 . The method of  claim 1 , further comprising:
 feeding the initial end cell membrane of a desalination train with brackish, seawater or brine comprising relatively high salt concentration water, generating a concentration field across the plurality of cells comprising a progressively decreasing concentration and osmotic pressure ratio throughout the train, bounded by saline water of high salt concentration at the initial end cell and by a low or no salt concentration at the opposed end cell, thereby producing a reverse osmosis train cycle;   wherein the cycle includes a controlled concentration-pressure loop, the concentration field comprising:   (a) Osmotically generates a continuous and constant flow rate of substantially salt-free permeate flux throughout each cell of the desalination train;   (b) Maintains a salt concentration difference across the semipermeable membrane shared by the adjacent cells in the plurality of cells;   (c) Defines a salt concentration ratio, preferably of equal ratios, within each cell that ensures a net positive reverse osmotic flow; and   (d) Discharges the desalinated water at the opposing end cell; and operating the symbiotic reverse osmosis train under conditions effective to recover a continuous and essentially salt free flow of desalinated water.   
     
     
         7 . The method of  claim 1 , further comprising:
 charging each cell in the symbiotic reverse osmosis train with given brine of a specified salt concentration for sustaining efficient recovery of desalinated water at the tail end of the train. Therefore, average salt concentration differential across each membranes panel and concentration differential at the inlet and outlet termination points of each membranes panel, must be specified and uniformly selected for all membrane panels in the train,   
     
     
         8 . The method of  claim 7 , wherein the salinity reverse osmosis application has an average salt concentration differential of 2%-4%, for brackish and seawater and 4%-6% for higher salinity brine feed, as a gradual salinity change, of the same value, between any membrane cell and its preceding cell in the train, throughout the desalination membrane panels train. 
     
     
         9 . The method of  claim 7 , further comprising:
 allowing the permeated flow across the adjacent cell, either in the case of symbiotic reverse osmosis, or in the case of induced symbiotic osmosis for power generation be constant throughout all the train cells and therefor referred to as a Tie Line, where the tie line is determined by the volumetric difference between the saline water flow entering, the initial end cell and the concentrated saline water rejected from the said cell.   
     
     
         10 . The method of  claim 7 , wherein the concentration differential at a membrane panel high salinity end is configured to be 4% for seawater and 6% for higher salinity brines. 
     
     
         11 . The method of  claim 7 , wherein the concentration differential at a membrane panel low salinity end is configured to be 1% for seawater and 1-2% for higher salinity brines. 
     
     
         12 . The method of  claim 7 , wherein the concentration ratio of membrane panel end points is configured to be 4% for seawater and brines, and more than 10% for brackish waters. 
     
     
         13 . The method of  claim 7 , wherein the sequence of membrane arrangement is configured to produce a uniform profile of concentration differential between the sequential cells throughout the train. 
     
     
         14 . The method of  claim 7 , further comprising:
 calculating the water differential salinity by adopting use of a log mean concentration difference.   
     
     
         14 . The method of  claim 10 , further comprising:
 allowing the permeated flow across the adjacent cell, either in the case of symbiotic reverse osmosis, or in the case of induced symbiotic osmosis for power generation be constant throughout all the train cells and therefor referred to as a Tie Line, where the tie line is determined by the volumetric difference between the saline water flow entering, the initial end cell and the concentrated saline water rejected from the said cell.   
     
     
         16 . The method of  claim 1 , further comprising:
 sizing the train in accordance with the cell concentration differentials when optimizing a desalination plant design.   
     
     
         17 . The method of  claim 1 , wherein the desalinate water recovery from seawater in the Symbiotic Reverse Osmosis process is configured to exceed 85%, without exceeding the allowable operating pressure of the membranes, while, maintaining the rejected brine, below its salinity saturation point; as an example in the range of 28-30% to avoid salt accumulation on the membrane particularly in the cold weather. 
     
     
         18 . The method of  claim 1 , wherein the Symbiotic Reverse Osmosis process allows for desalination of saline feed of up to 15% salt content to recover about 50% of desalinated water and rejected brine of about 28-30%. 
     
     
         19 . The method of  claim 18 , wherein this high rejected salinity brine of 28-30% is an optimum saline concentration that can be used to either generate power by exchanging it with seawater in accordance to an Induced Symbiotic Osmotic Power Generation Technology, or recover salt by evaporation/crystallization for commercial use. 
     
     
         20 . The method according to  claim 1 , wherein each cell in the plurality of cells is a fluidic continuous loop filled with saline solution of specific concentration and osmotic pressure, having dedicated fluid pumping system and dedicated power recovery system comprising a hydro-power generation turbine system or fluid pressure exchanger, where the fluid pumping system and the power recovery system are placed on the opposite side of the loop; and
 wherein both devices are continually circulating the saline fluid within their cell perimeters, where the loop section from power recovery system to the fluid pumping system is handling relatively concentrated high salinity brine at relatively low pressure to facilitate inducement of substantially salt-free permeate water from the preceding cell while the loop section from the fluid pumping system and back to power recovery system is handling relatively diluted low concentration brine at relatively high pressure to facilitate forcing desalinated water through the adjacent following cell.   
     
     
         21 . The method of  claim 20 , wherein the process is continuous and simultaneously engaging the membranes in the pre and post membrane panels in the train, where the cell receives desalinated water forcedly by the pumping system in the pre cell, and forcedly and continually deliver desalinated water at the same rate it was received, by means of said cell pumping system, to the post membrane panels, where same flow cycle is repeated in the post cycles throughout the train. 
     
     
         22 . The method of  claim 20 , further comprising:
 evaluating membrane capacity and the required surface area to accommodate a tie line flow throughout the membrane panels train.   
     
     
         23 . The method according of  claim 20 , wherein the salt type and quantity of membrane panels between the initial end cell and the intermediate cells are different, where the initial end cell is essentially a conventional reverse osmosis cell that relies on natural waters as a feed, while the intermediate cells are enclosed cells of formulated salt content of specific chemical composition, with specific operation and maintenance procedures. 
     
     
         24 . The method according to  claim 1 , wherein the given brine comprises a hydrate inhibitor, a biological growth control and a scale formation control. 
     
     
         25 . The method according to  claim 1 , wherein the specified ionizable inorganic salt type is selected from the group of food grade, nonhazardous, low molecular weight comprising of sodium chloride, sodium iodide, lithium chloride, potassium iodide and others. 
     
     
         26 . The method according to  claim 1 , wherein the brine of the initial end cell has no direct contact with the formulated brine of the opposed end cell, only salt-free water is configured to be defused from one membrane stage to the next membrane stage at a continuous constant rate, recognized here as a Tie Line. 
     
     
         27 . The method according to  claim 1 , wherein the plurality of cells cycle continuously in the same pattern maintaining countercurrent flow across each semi-permeable membrane and wherein an interruption of a segment of the power train halts the flow of the substantially salt-free permeate flux. 
     
     
         28 . The method according to  claim 1 , wherein the proposed new multi-membrane technology comprising symbiotic cascading flat sheet or a hollow fiber membrane train and potentially both configurations would be also incorporated for water pretreatment, comprising macro, micro and ultra-filtration treatment ahead of the desalination train. 
     
     
         29 . The method according to  claim 1 , further comprising:
 capturing of salt within the process thereby resulting in reduced energy demand for evaporation and crystallization for human consumption and other commercial applications.   
     
     
         30 . The method according to  claim 1 , further comprising:
 compensating for salt depletion in each loop based on salinity measurements in each cell by introducing an automated brine insertion device into the hydraulic loop.   
     
     
         31 . The method of  claim 1 , wherein membrane train cells is configured to accept a progressively increasing or decreasing concentration of brine and osmotic pressure ratio. 
     
     
         32 . The method of  claim 1 , wherein the fluid between flat sheet membrane panels or hollow fiber arrays are spaced and maintained at a prescribed Reynolds number between 3,000 and 3,500. 
     
     
         33 . The method of  claim 32 , wherein the membrane panel is configured to insure a uniform flow pattern and pressure drop between membrane modules, the membrane module being a semipermeable flat sheet membranes or semipermeable hollow fiber membrane, with automated back flush. 
     
     
         34 . The method of  claim 1 , wherein the membrane panel is configured to insure a uniform flow pattern and pressure drop between membrane modules, the membrane module being a semipermeable flat sheet membranes or semipermeable hollow fiber membrane, with automated back flush. 
     
     
         35 . The method of  claim 1 , wherein the fluid in the system is configured to backflush the initial end cell (first membrane panel) that is potentially subjected to atmospheric conditions and raw water fouling, by isolating the train in question for several minutes, then exposing initial end cell to high salinity brine, meanwhile introducing salt free water on the opposite side of in the initial end cell through the adjacent intermediate cell to promote a symbiotic osmosis water flow movement from said cell across through the membrane of initial end cell to dislodge particles that foul this membrane. 
     
     
         36 . The method of  claim 1 , wherein the train of cells is configured in the form of self-supported vertical vessels or towers of vertically staked membrane panels. 
     
     
         37 . The method of  claim 1 , wherein the train comprises relatively large pressure vessels of one meter in diameter or more, that can be insulated to withstand atmospheric conditions indoor or outdoor. 
     
     
         38 . The method of  claim 1 , further allowing, as a side benefit, the recovery of the high salinity brine (28-30%), the byproduct of the desalination process, for producing, high quality salt for human consumption and other commercial applications at reduced cost and rather continuously.