COMBINATORIAL MEMBRANE-BASED SYSTEMS AND METHODS FOR DEWATERING AND CONCENTRATING APPLICATIONS

Abstract

This invention relates to various membrane-based processes and their combinations, such as Forward Osmosis (FO), Reverse 5 Osmosis (RO), Nanofiltration (NF), Ultrafiltration (UF), Membrane Bioreactor (MBR), Osmotic Distillation (OD) and Membrane Distillation (MD), for various application of dilution, concentration, dewatering, separation, purification, fractionation or extraction applications of different solvents including 10 various sources of water, wastewater, active pharmaceutical ingredients (APIs), food and beverage sources, dairy products etc. It is also applicable to all the industrial and domestic applications that involves recovering or water reclamation from inlet sources.

Claims

1. A Hybrid Membrane-based processes for dewatering, concentration, solvent separation, extraction, purification or filtration applications of different liquid feed sources consists with single or multistage forward osmosis with any combination of single or multistage reverse osmosis (RO), nanofiltration (NF), membrane distillation (MD) in series or parallel configuration for draw solution regeneration and product water recovery; Wherein product of FO is fed to single or multistage high pressure direct pass NF unit; Wherein product of FO is fed to single or multistage high pressure direct pass brine water RO (BWRO) unit; Wherein product of FO is fed to single or multistage high pressure direct pass sea water RO (SWRO) unit; Wherein product of FO is fed to single or multistage NF followed by multistage high pressure BWRO or SWRO combinatorial units; Wherein product of FO is fed to single or multistage high pressure BWRO and SWRO combinatorial unit; Wherein reject or concentrate of single stage FO unit is fed to subsequent single or multistage FO unit with subsequent single or multistage high pressure direct pass NF or BWRO or SWRO units in a combinatorial units; Wherein feed to FO is subjected to prior pre-treatment stages of Membrane Bioreactor (MBR), pressure sand filters (PSF), activated carbon (AC) adsorption, micron cartridge filters, ultrafiltration (UF) units

2. A water treatment method comprising of Source feed liquid which is any of the following: sea water, brackish water, industrial wastewater, impaired water, domestic household wastewater, reverse osmosis brine, membrane filtration concentrates, food & beverage based wastewater, fruits juices, milk whey, any liquid or solvent systems that requires to be dewatered, purified, separated, fextracted, fractionated or concentrated; Wherein single stage or multistage forward osmosis membrane comprising of aromatic polyamide based thin film composite (TFC) or cellulose triacetate (CTA) semi permeable membrane capable enough to dewater or concentrate source liquid; Wherein single stage or multistage forward osmosis membrane of hollow fiber or spiral wound flat sheet configuration Source feed liquid having certain solute and solvent concentration and corresponding osmotic pressure and the second feed solution stream “draw solution” having specific solutes and solute concentration; Wherein passing an inlet feed source of solute-solvent stream through naturally occurring low pressure forward osmosis membrane system while draw solution on permeate side of forward osmosis membrane system as described in claim 1 Wherein passing the product water containing diluted draw solution from FO unit is then passed through multistage pressurized Counter-currently (or Co-currently) fed Sweep Solution assisted Osmotic RO (CSORO) or NF (CSONF) or in their combinatorial arrangement at their feed compartment through high pressure pump system to produce pressurized concentrated draw solution stream at the last stage of CSORO or CSONF or their combinatorial system Wherein low pressure sweep solution containing specific solutes and solute concentration having similar or lower osmotic pressure than the feed, passing counter currently or concurrently through permeate compartment of single stage or multistage CSONF or CSORO or their combinatorial system, to produce low salinity desalinated product water stream at the last stage of CSORO or CSONF or their combinatorial system Wherein the equipment configuration and the methodology for CSORO or CSONF system are adjusted accordingly to exhibit sufficient osmotic pressure differential between feed compartment and permeate compartment so that solvent or water passes from the BWRO or SWRO or NF or their combinatorial membrane system Wherein passing the concentrate from first stage CSONF or CSORO through high pressure booster pump in to the second stage while low pressure osmotic sweep solution passing through permeate side of the membrane resulting even more concentrated reject brine and even more diluted sweep solution in a counter-currently or co-currently fed manner Wherein repeating the methodology of osmotically enhanced CSORO or CSONF or their combinations in a pressurized feed or concentrated compartment through high pressure pump and low pressure sweep solution passing through CSORO or CSONF permeate compartment in a counter current or concurrent mode until desired terminal stage draw solution concentration is achieved Wherein highly concentrated draw solution from terminal stage of CSONF or CSORO or their combinatorial system returns back to Forward Osmosis draw solution feed Wherein diluted sweep solution after recovering product water from draw solution having significantly lower concentration or osmotic pressure from terminal stage of osmotically enhanced CSONF or CSORO or their combinatorial system passes through single or multistage direct pass high pressure NF or BWRO or SWRO membrane systems producing permeate water having product water quality meeting WHO standards of less than 500 ppm TDS Wherein concentrated reject or brine emerging from direct pass single of multistage NF or BWRO or SWRO membrane system returns to first stage of low pressure permeate compartment of CSONF or CSORO Wherein FO and single or multistage CSORO or CSONF or their combinatorial system uses draw solution of inorganic salts and preferably magnesium chloride, calcium chloride, sodium chloride, potassium chloride, ammonium chloride, sodium sulphate, magnesium sulphate etc. Wherein FO and single or multistage CSORO or CSONF or their combinatorial system uses draw solution of organic compounds, preferably sodium salt of EDTA, glucose, sucrose, fructose, fatty acid, glycol, organic salts, fertilizers Wherein FO and single or multistage CSORO or CSONF or their combinatorial system uses draw solution of synthetically made molecules such as sodium polyacrylates dendrimers, polymer hydrogel, ammonia-carbon dioxide, thermosensitive polyelectrolytes, switchable polarity solvents, zwitterions (i.e. glycine, L-proline, glycine betaine) etc.

3. A Membrane Distillation (MD) unit for further concentration of feed to the concentration near saturation levels of salts; (a) In the process of claim 1, wherein further draw solution regeneration from FO product is fed to MD unit; (b) In the process of claim 2, wherein concentrated draw solution from multistage CSONF or CSORO unit of FO system is fed to MD unit (c) In the process of claim 1 and claim 2, wherein concentrated brine or reject stream of single of multistage FO system passes through single or multistage MD unit (d) In the process of claim 1 and claim 2, where concentrated brine or reject from FO system gets further concentrated up to 20-25% wt/wt of salt concentration (e) The concentrated brine from MD system then subjected to thermal evaporation unit of multistage evaporators and crystallization units (f) Wherein MD membrane unit is made of hydrophobic ePTFE, PP or PVDF hollow fiber membrane and operated under either Direct Contact Membrane Distillation (DCMD) or Vacuum assisted Membrane Distillation (VMD) and achieves salt concentration up to 18-25% wt/wt (g) Comprises of arrays of heat exchanger, MD unit, feed pumps, vacuum pump (for VMD) and condenser unit to achieve desired levels of product water quality and quantity, brine concentration and minimization and energy efficiency (h) MD feed heated up to 55-70° C. before being fed to MD unit. (i) Saline feed water stays outside of hydrophobic pore and does not wet the internal structure of the membrane. The water vapor passes though the hydrophobic pores of the membrane and condenses on condenser or chiller part at or after permeate compartment (j) concentrate from MD is recirculated back to FO unit (k) concentrate from draw solution recovery of NF, RO, CSORO or CSONF is fed to MD unit (l) MD unit can be externally mounted in series or parallel and fed through external pump systems and feed solution is fed to shell side of the membrane and product water is recovered from bore or lumen side of the membrane (m) MD unit as a submerged unit placed directly into saline medium and saline medium is constantly circulated through external heat exchanger system

4. The process of claim 1, wherein pressure difference across the FO, NF, RO, CSORO, CSONF membranes adjusted for stable operation and to obtain desired water flux.

5. The process of claim 1, wherein draw solution constituent, concentration and flow are adjusted and optimized to achieve desired water flux

6. The process of claim 1, wherein source feed flow is adjusted and optimized to allow desirable residence time

7. The method of claim 2 wherein the draw solution is fed to osmotically enhanced CSONF or CSORO or their combinatorial system to recover draw solute and separate product water.

8. The process of claim 3, wherein heat exchangers and condensers are arranged in specific combinations for source feed and source heat to achieve maximum heat efficiency at lower capital and operation investment

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] It will be convenient to further describe the present invention with respect to the accompanying drawings that illustrate possible arrangements of the invention. Other arrangements of the invention are possible, and consequently the particularity of the accompanying drawings is not intended to be limiting

[0060] FIG. 1 represents schematic diagram of multi-stage and multi-pass Forward Osmosis (FO) process in combination of Counter-currently operated Sweep solution assisted Osmotic Reverse Osmosis system (CSORO).

[0061] FIG. 2 Schematic of hybrid Forward Osmosis process of RO-FO-NF in series

[0062] FIG. 3: Schematic of hybrid Forward Osmosis process of FO-RO with FO reject fed to NF system

[0063] FIG. 4: Schematic of hybrid Forward Osmosis process of FO-NF-NF

[0064] FIG. 5: Schematic of hybrid Forward Osmosis process of FO-MD

[0065] FIG. 6: Schematic of hybrid Forward Osmosis process of NF-FO-MD

[0066] FIG. 7: Schematic of hybrid Forward Osmosis process of NF-FO-NF

[0067] FIG. 8: Process Instrumentation and Control Diagram (P&ID) of Forward Osmosis-Membrane Distillation Setup as outlined in FIG. 5

[0068] FIG. 9: Process Schematic of FO and heat integrated MD unit under optimized conditions

DETAILED DESCRIPTION OF THE INVENTION

[0069] Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and arrangement of parts illustrated in the accompanying drawings. The invention is capable of other embodiments, as depicted in different figures as described above and of being practiced or carried out hi a variety of ways. It is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.

[0070] FO membrane system will have diluted draw solution mixed with product water and entering into draw solution regeneration units. This patent disclosure reveals novel method of draw solution regeneration using multi-stage and multi-pass Counter-currently (or Co-currently) fed Sweep solution assisted Osmotic of RO (CSORO) or NF (CSONF) system that systematically reduces overall hydraulic pressure required to obtain product water from inlet diluted draw feed. The saline sweep solution (salinity equivalent to feed source) is fed at permeate compartment at a lower pressure than feed compartment pressure. FIG. 1 represents schematic diagram of counter-currently operated osmotic reverse osmosis system (the configuration can also be concurrently fed feed and saline sweep solution).

[0071] The scheme represented in dashed line describes overall operation wherein high saline feed stream 1 that requires to be concentrated is fed to the system of forward osmosis unit 2. Forward osmosis unit is separated by semi-permeable thin film composite (TFC) membrane made up of aromatic polyamide or cellulose triacetate (CTA) based membrane. The FO membrane allows separation of feed stream 1 and draw solution feed 3. Due to the action of naturally occurring osmosis process, feed water passes through FO membrane and dilutes the draw solution and leaves through the system 5. The concentrated feed or brine can be subjected to further concentration in subsequent FO unit or subsequently fed to thermal evaporator and crystallization unit for complete water removal and Zero Liquid Discharge (ZLD). The diluted draw solution stream 5 then passes through multiple array of counter current or con-current operated reverse osmosis system. The high pressure pumps 6, 8, 10 and correspondingly additional pumps according to number of RO stages pushes diluted draw solution to high concentration feed compartment of RO system 7, 9, 11 and correspondingly additional RO/NF stages respectively. For example in FIG. 1, three stage high pressure NF/RO stages are described. The highly concentrated draw solution leaves from final RO unit from stream 12 and contains draw solution concentration equivalent to initial feed concentration of FO unit to merge with stream 3 again. Occasionally some of the draw solution will be added to adjust the flow and concentration of feed draw solution concentration via stream 22.

[0072] The high osmotic pressure sweep solution can be either natural inorganic salt or synthetically made solution is counter currently or con-currently fed 18 with low pressure pump 19 to the permeate side 15 of last stage NF or RO unit. The preferred sweep solution are sodium ion based polyelectrolytes. The concentration of synthetic sweep solution is adjusted such that net osmotic pressure will be relative low corresponding to the concentration of feed side stream entering from previous NF or RO stage 9. This low net osmotic pressure eventually gives significantly lower hydraulic pressure applicable to pump 10. Upon application of hydraulic pressure corresponding to feed and sweep concentration, the net product water flow will be established across NF or RO membrane resulting in dilution of synthetic sweep solution feed and further concentration feed draw solution. The same methodology will be repeated in multiple stages to achieve treatment continuity and process conditions that are optimally operated.

[0073] The first stage will have the sweep solution leaving from the system 5 in a most diluted form. The concentration of sweep solution leaving 5 from the first stage is sufficiently low enough that can be treated by single-stage or multi-stage direct pass brackish water RO or sea water RO system. The permeate water 17 will have product water quality which is meeting WHO standards for drinking water conditions and the concentrate stream 18 is again fed back by low pressure pump 19 to last stage permeate compartment 15 of NF or RO process.

[0074] The entire system description described above from 1 to 22 comprises of one stage FO system that recovers product water 17 from feed stream 1 and further concentrates the feed depending on water recovery giving concentrated brine 4.

[0075] This invention discloses additional features of coupling additional FO systems that further concentrates the brine 4.

[0076] For example, in one specific scenario, the feed concentration from industrial wastewater effluent was subjected to two-stage FO system where feed was concentrated from 5% wt/wt salt to 13% wt/wt concentration.

[0077] After subsequent FO stages as described in FIG. 1, the concentrated brine from final stage 26 leaves FO units for further water recovery in downstream processes. Conventionally this is accomplished in a single or multistage thermal evaporator and crystallization units. However, this invention discloses novel method of incorporating membrane distillation unit for reject brine concentration together with multistage FO and counter current osmotic NF or RO system for draw solution recovery.

TABLE-US-00001 TABLE 1 Test results of single stage FO-CSORO configuration of various industrial wastewaters Feed Product Concentrate Energy Process TDS, COD, TSS, TDS, COD, TDS, Feed, Output, Consumption, Trial Description pH mg/l mg/l mg/l pH mg/l mg/l mg/l Litre/hr Litre/hr Recovery kWh/m3 Trial-I FO + 2 Stage 7.1 23,600 4198  430 6.5 300 163  86055 3000 2200   73% 9.6 CSORO Trial-II FO + 2 Stage 6.9 17,060 3715  854  6.81 315   206.4  55700 3000 2100   70% 9.6 CSORO Trial-III FO + 3 Stage 6.9 42,700 6501 1230 6.8 620 300 114554 3000 1900   63% 11.3  CSORO Trial-IV FO + 3 Stage 6.7 38,000 6200 1150 6.8 350 215 112977 3000 2050 66.66% 11.3  CSORO Trial-V FO + 3 Stage 6.7 41,400 5242 1060 6.8 352 165 111040 3000 1900   63% 11.3  CSORO Trial-VI FO + 2 Stage 6.7 48,000 6252  950 6.8 520 170 119250 3000 1800   60% 11.3  CSORO Trial-VII FO + 3 Stage 6.8 70,560 8348 2240 6.8 350 170 155650 3000 1800   60% 11.3  CSORO Trial-VIII FO + 3 Stage 6.8  54000 7800  780 6.3 200 210 135094 3000 1900   63% 11.3  CSORO

[0078] FIG. 5 represents system where very high salinity levels are in consideration particularly if TDS is higher than 130000 ppm range. Here the brine from multistage FO system 26 (FIG. 1) enters via 4 in subsequent Forward Osmosis-Membrane Distillation (MD) unit through tank 1 and pump 3, where draw solution stream containing product water (5) is being treated with custom-made membrane distillation unit (28). The diluted draw solution stream eventually passes through intermediate heat exchanger or heat pump which increases the temperature of the stream from ambient to 55-70° C. depending on which membrane distillation configuration was selected. More details on membrane distillation can be found elsewhere hi literature [8-10]. The product stream (12) from MD is passed through condenser (25) followed by collection in a product tank (26). The draw solution gets concentrated over time after recovery of substantial amount of product water. After desired increase in draw solution concentration, the draw solution is again fed back to FO system (22).

[0079] This way it is possible to concentrate the feed from 5% wt/wt to 20-25% wt/wt

[0080] Combinatorial Membrane Process

[0081] Although many tertiary treatment processes or zero liquid discharge solutions use Reverse Osmosis (RO) or nanofiltration (NF) to turn wastewater into recycled or reused water. However, higher salinity levels mean high energy requirement to overcome high osmotic pressure and high operating pressure of such pressure in pressure driven RO or NF process practically limit overall water recovery. Apart from limiting aspects from operation point of view, standalone RO and NF process also gives other maintenance issues such as high scaling and fouling propensity, expensive pumps and piping, frequent cleaning schedule and expensive cleaning chemicals usage.

[0082] There are very few ways to improve water recovery without affecting pressure requirement and overall system operation and maintenance costs. Hybrid FO system involves innovative FO membrane exploiting normal osmotic pressure to induce clean water flow from feed stream across the membrane in to the draw solution.

[0083] Depending on water quality, source and product water quality requirements, the draw solution recovery unit can be adjusted accordingly such as individual unit operations of RO (FO-RO), NF

[0084] (FO-NF), ultrafiltration (UF) (FO-UF), membrane distillation (MD) (FO-MD) or combination of these operations in different configurations such as FO-NF-RO, FO-NF-NF, NF-FO-RO, NF-FO-NF, NF-FO-MD, FO-NF-MD, NF-RO-UF etc., in the downstream section separates draw solution from product water. FO membrane is of cellulose acetate based hollow-fiber membrane module with systematic configuration to allow for co-current or counter-current operation mode. In order to maintain structural integrity of hollow fibers it is essential to keep positive pressure of 3 barg between shell-side and lumen-side of the fiber. Apart from that it is also important to maintain robust start-up and shut-down protocol to reduce pressure shock to hollow fiber membranes.

[0085] For RO or NF, commercially available membranes were chosen, which could be Dow Filmtec, Hydronautics, GE Osmonics, Toray or CSM. Depending on the solute concentration, product water requirement and draw solute selection, RO or NF membranes were chosen. In case it is essential to have high draw solute recovery due to cost-considerations, it is necessary to select high salt rejection membrane configuration. However, if it is necessary to recover as much product water, high water flux or high permeability membranes were chosen.

[0086] Table.2 shows schematic representation of hybrid Forward Osmosis system. The system consist of main FO unit combined with other unit process for the draw solution recovery i.e. nanofiltration (NF) and/or reverse osmosis (RO) and/or membrane distillation (MD) system. The recovery section process selection depends on many factors including the application of process, influent feed water quality, feed salinity, draw solute, resource constraint, concentrate disposal criteria etc.

[0087] Depending on salinity levels, different configurations for FO system are considered involving FO in combination with individual operations such as NF, RO or MD were implemented or alternatively for more complex system FO in combination with multiple draw solution recovery section are considered such as FO-NF-NF, FO-NF-RO, NF-FO-MD etc.

TABLE-US-00002 TABLE 2 Various hybrid FO process configuration depending on feed water and application Treatment TDS levels Configurations Application 0-5000 NF-FO-RO, FO-NF, FO-RO, Brackish water, RO-FO-RO ground water, surface water, industrial and domestic wastewater 5000-20000 NF-FO-RO, FO-NF-RO, FO- Brackish water, RO, FO-NF, FO-Multistage seawater, highly Counter Current Osmotic saline wastewater NF or RO 20000-40000 FO-NF-RO, FO-MD, FO-NF- Sea water, highly NF, FO-NF-RO, FO-NF, FO- saline industrial Multistage Counter Current wastewater Osmotic NF or RO >40000 FO-NF-RO-MD, NF-FO-RO- Highly saline MD, FO-NF-MD, FO- industrial waste Multistage Counter Current water Osmotic NF or RO

[0088] This invention describes the process to treat and recycle secondary treatment effluent of industrial wastewater. The pilot plant was bunt to test multiple configurations with “plug-and-play” approach with quick-fix piping, valves and pump system.

[0089] For example one the system which was tested was RO-FO-NF system in FIG. 2—involving hybrid FO (17) and RO (10) to recover water, along with NF (27) process to recover draw solution, is disclosed for treating and recycling industrial waste water for inlet water quality as follows: TDS 35000 ppm, COD 550 ppm, Total Hardness 1720 ppm, TSS 120 ppm.

[0090] The process involves wastewater feed stream (1) entering into feed tank (2) followed by treating it with pretreatment unit operations involving multimedia filters (MMF) and ultrafiltration (6) fed to it by pump (4). After MMF and UF, the stream is fed to RO unit (10) at 40-60 Barg pressure using high pressure pump (8). Pressure pushes water through the membrane towards permeate side and leaves the system via 12 and 29 to product water tank 30. The RO system gives 30-50% water recovery.

[0091] Untreated and 50-70% rejected water from untreated retentate side leaves the RO system via 11 and fed to tank 13. The rejected water will eventually be pumped by 14 and enters forward osmosis unit 17 via 16. Forward osmosis unit is mainly hollow fiber membrane module which operates in a counter-current mode. The concentrated draw solution is fed (19) to bore side (inside part) of the hollow fiber and feed stream (16) stays in shell-side (outside part) of the module. In order to achieve stable operation, it is essential to keep bore side pressure lower than the shell side of the stream.

[0092] Due to the concentration difference between feed and draw solution, water transport through the shell-side to the bore-side of the module and leaves from the end port. FO system concentrates the feed stream and retained constituents with remaining water leaves the FO system (18) for disposal. FO system recovers 50-75% of water from feed stream to draw solution stream.

[0093] Diluted draw solution stream (20) leaves the FO system to tank 21 which subsequently been pumped via 22 to nanofiltration module 27. In nanofiltration module (27), zwitterion containing draw solution is separated from product water and leaves via stream 24 to tank 25. Potable water from the NF permeate side is sent to tank 30 via 28 and 29.

[0094] Zwitterion containing draw solution is again recycle back after providing desired replenishment to FO unit 17 via pump 26 and stream 19.

[0095] Other hybrid FO process configuration were described in the following sections. In FIG. 3, in comparison with system shown in FIG. 2, the concentrate or reject from FO (15) is being fed to NF system (21) where the product water eventually gets collected in product water tank (24) and the reject stream gets discarded (26). This system of FO reject recycle could be interesting for wastewater source where multivalent ion concentration was extremely high. FIG. 4 represents system where extremely high salinity levels are in consideration particularly if TDS is higher than 40000-50000 ppm range. Here FO product stream (or diluted draw solution stream) (5) is being treated with first stage NF system (10). The product stream (16) from 1st stage NF is collected in intermediate tank (16), which eventually is sent to 2nd stage NF system via 18. The product is eventually collected via 24. The reject from the 1st stage (11) is concentrated draw solution which is again fed back to FO system (15). Here for the test cases, 1st stage NF was considered as open, less fight, high permeate flow NF membrane which could be Dow Filmtec NF270 or Hydranautics NANO-SW membranes which in the 2nd stage the membrane could be fight, high salt rejection membrane such as Dow Filmtec NF90.

[0096] FIG. 8 represents detailed instrumentation and control diagram of system described in FIG. 5 wherein very high salinity levels are in consideration particularly if TDS is higher than 50000 ppm range. Here FO product stream (or diluted draw solution stream) (5) is being treated with custom-made membrane distillation unit (28). The diluted draw solution stream eventually passes through intermediate heat exchanger which increases the temperature of the stream from ambient to 55-70° C. depending on which membrane distillation configuration was selected. The membrane distillation (MD) unit is made up of hydrophobic ePTFE or PVDF hollow fiber membrane. The water contact angle of ePTFE membrane is around 125° and PVDF is around 110°.

[0097] The product stream (12) from MD is passed through condenser (25) followed by collection in a product tank (26). The draw solution gets concentrated over time after recovery of substantial amount of product water. After desired increase in draw solution concentration, the draw solution is again fed back to FO system (22). Draw solution recovery with MD system can be combined with array of heat exchangers as showcased in FIG. 9 so that the effective heat integration provides most optimal energy consumption to produce unit volume of product water.

[0098] FIG. 6 is somewhat similar to system shown in FIG. 4 however, if the inlet water stream contains high multivalent components or hardness precursors, it is advisable to initially pass the wastewater stream to primary NF system (6). Few applications have been successfully tested for FIG. 5 configuration including concentration of sodium Sulphate, calcium chloride solution from 3-5 wt % to 25-27 wt %.

[0099] FIG. 7 can be implemented for industrial wastewater or seawater where the first stage NF (6) removes hardness components including undesirable multivalent ions. Remaining system stays similar to what was described in previous schemes where diluted draw solution (12) containing product water is subjected to NF operation (17). Product water is collected in tank 26 and recovered draw solution (18) is sent back to draw solution feed tank (19). Several applications have been tested such as sea water desalination, municipal wastewater treatment and recycle, industrial wastewater recycle and reuse.

[0100] The details of process and operating parameters for respective unit operation, stream and units are expressed in Table 2.

[0101] The feasibility studies have been conducted to identify practical and operational limitations of the plant. The Design of Experiment (DOE) matrix was performed in order to identify the optimized conditions. The three-Factor DOE was tested involving feed TDS, transmembrane pressure and draw solution composition.

[0102] There are number of responses to be observed in above DOE namely water flux, fouling tendency, reverse salt flux, energy consumption etc.

[0103] The DOE is mentioned below:

TABLE-US-00003 Factor Name Letter Setting 1 Setting 2 Feed TDS, ppm A 5000 90000 Feed Flow Rate, B 1 4 m3/hr Draw Solution C 150000 270000 Concentration, ppm

[0104] FIG. 8: Process Instrumentation and Control Diagram (P&ID) of Forward Osmosis-Membrane Distillation Setup as outlined in FIG. 5

[0105] FIG. 9: Process Schematic of FO and heat integrated MD unit under optimized conditions

[0106] The pilot plant of 20,000 m3/day capacity has been successfully tested for continuous 5000 hours combining Forward Osmosis-CSORO-MD system provides valuable results in terms of process performance, water flux, membrane fouling, reverse solute flux, scaling etc.

[0107] This invention has showcased effective combination of conventional processes such as NF, RO, CSONF, CSORO or MD with novel FO process that is suitable to treat high-salinity water. With modular and scalable system, it may even be possible to fine-tune the system based on feed water quality and application. Such approach would reduce the costs related to pretreatment, membrane life, chemical cleaning, reduced piping and overall reduced maintenance. Further, operating costs of wastewater recycling using processes mentioned in this invention work has been reduced up to 50%.

[0108] The process for treating and recycling water source which can be industrial, household, seawater, food & beverage, pharmaceuticals or any source which requires dewatering or concentration of feed and extraction of product water using single or multistage forward osmosis with any combination of single or multistage reverse osmosis, nanofiltration, membrane distillation in series or parallel configuration for draw solution recovery. Such system would be called FO system