# US 9,433,902 B2 · Low energy system and method of desalinating seawater > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,433,902 B2 - Document ID: US9433902B2 - Status: Granted - Kind: B2 - Application number: 14/539,691 - Filed: 2014-11-12 - Published: 2015-04-23 - Granted: 2016-09-06 - Earliest claimed: 2007-09-21 - Assignees: Evoqua Water Technologies LLC - Applicants: Evoqua Water Technologies LLC - Inventors: Gary C. Ganzi; Li-Shiang Liang; Frederick C. Wilkins - Web page: https://patentgrep.com/patent/US9433902B2 ## CPC - C02F 1/4604: {for desalination of seawater or brackish water} - B01D 61/58: Multistep processes - C02F 1/4674: {with halogen or compound of halogens, e.g. chlorine, bromine} - C02F 1/4693: {electrodialysis} - C02F 1/4695: {electrodeionisation} - B01D 61/44: Ion-selective electrodialysis - B01D 61/48: having one or more compartments filled with ion-exchange material {, e.g. electrodeionisation} - B01D 2311/06: Specific process operations in the permeate stream - B01D 2313/28: Specific concentration chambers - B01D 2313/30: Specific dilution or de-ionizing chambers - C02F 1/001: {Processes for the treatment of water whereby the filtration technique is of importance (C02F1/44 takes precedence; construction of filters in general B01D24/00 - B01D41/00)} - C02F 1/444: {by ultrafiltration or microfiltration} - C02F 2001/422: {using anionic exchangers} - C02F 2103/08: Seawater, e.g. for desalination - C02F 2209/005: Processes using a programmable logic controller [PLC] - Y02A 20/124: Water desalination - Y02A 20/131: Reverse-osmosis - C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes) - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE ## Abstract A low energy water treatment system and method is provided. The system has at least one electrodialysis device that produces partially treated water and a brine byproduct, a softener, and at least one electrodeionization device. The partially treated water stream can be softened by the softener to reduce the likelihood of scale formation and to reduce energy consumption in the electrodeionization device, which produces water having target properties. At least a portion of the energy used by the electrodeionization device can be generated by concentration differences between the brine and seawater streams introduced into compartments thereof. The brine stream can also be used to regenerate the softener. ## Claims ### Claim 1 A method of desalinating seawater comprising: reducing a concentration of monovalent species in the seawater in a first desalting stage to produce partially desalted water; producing a brine solution from the seawater, the brine solution having a total dissolved solids concentration that is greater than the concentration of total dissolved solids in the seawater; introducing the partially desalted water into a first depleting compartment of an electrically-driven separation device; and introducing the brine solution into a second depleting compartment of the electrically-driven separation device, the second depleting compartment included in a concentration cell pair along with a half-cell concentration compartment, wherein introducing the brine solution into the second depleting compartment induces transportation of at least a portion of a dissolved species from the partially desalted water in the first depleting compartment into the half-cell concentration compartment of the concentration cell pair under the influence of a concentration-induced electrical potential developed in the concentration cell pair. ### Claim 2 (depends on 1) The method of claim 1, further comprising replacing at least a portion of dissolved non-monovalent species in the partially desalted water with dissolved monovalent species. ### Claim 3 (depends on 1) The method of claim 1, wherein reducing the concentration of the monovalent species of seawater comprises selectively reducing the concentration of dissolved monovalent species in an electrodialysis device. ### Claim 4 (depends on 1) The method of claim 1, wherein producing the brine solution comprises promoting transport of at least a portion of dissolved species from the seawater into a second seawater stream flowing in a concentration compartment of an electrodialysis device. ### Claim 5 (depends on 1) The method of claim 1, further comprising: electrolytically generating at least one of chlorine and a hypochlorite species in an anode compartment of at least one of an electrolytic device, an electrodialysis device and the electrically-driven separation device, and electrolytically generating a caustic stream in one or more compartments of at least one of the electrolytic device, the electrodialysis device, and the electrically driven separation device. ### Claim 6 (depends on 5) The method of claim 5, further comprising at least partially disinfecting at least a portion of the seawater with the generated chlorine or hypochlorite species. ### Claim 7 (depends on 1) The method of claim 1, further comprising passing at least a portion of the seawater through a nanofiltration system before reducing the concentration of monovalent species of seawater in the first desalting stage. ### Claim 8 (depends on 1) The method of claim 1, further comprising: combining the partially desalted water with a second partially treated water stream to produce a combined partially treated stream; and treating the combined partially treated stream in an ion exchange system. ### Claim 9 (depends on 1) The method of claim 1, wherein transporting the at least a portion of the dissolved species from the partially desalted water in the first depleting compartment into the half-cell concentration compartment of the concentration cell pair produces a concentrate stream and an at least partially treated water. ### Claim 10 (depends on 9) The method of claim 9, wherein introducing the partially desalted water into the first depleting compartment of the electrically-driven separation device comprises introducing the partially desalted water into a first depleting compartment of an electrically-driven separation device having at least one of a monovalent anion selective membrane and a monovalent cation selective membrane. ### Claim 11 (depends on 9) The method of claim 9, wherein producing the concentration stream comprises producing a concentration stream having a salinity content of at least about 10 wt. %. ### Claim 12 (depends on 9) The method of claim 9, further comprising transporting at least a portion of the at least partially treated water to an ion exchange system. ### Claim 13 (depends on 12) The method of claim 12, further comprising treating the at least partially treated water in the ion exchange system to exchange non-monovalent species in the at least partially treated water for monovalent species. ### Claim 14 (depends on 1) The method of claim 1, further comprising positioning ion exchange resin in at least one of the first depleting compartment and the half-cell concentration compartment. ### Claim 15 (depends on 14) The method of claim 14, wherein the ion exchange resin comprises a mixed bed. ### Claim 16 (depends on 9) The method of claim 9, further comprising introducing the at least partially treated water to a third depleting compartment. ### Claim 17 (depends on 1) The method of claim 1, further comprising introducing the brine solution to a second half-cell concentration compartment. ### Claim 18 (depends on 1) The method of claim 1, wherein introducing the partially desalted water into the first depleting compartment of the electrically-driven separation device comprises introducing the partially desalted water into a first depleting compartment of an electrically-driven separation device having a sufficient number of concentration cell pairs to provide a concentration-induced electrical potential sufficient to desalinate the at least partially treated water to a desired level. ### Claim 19 (depends on 1) The method of claim 1, wherein introducing the partially desalted water into the first depleting compartment of the electrically-driven separation device comprises introducing the partially desalted water into a first depleting compartment of a Donnan-enhanced electrodeionization device. ### Claim 20 (depends on 1) The method of claim 1, wherein introducing the partially desalted water into the first depleting compartment of the electrically-driven separation device comprises introducing the partially desalted water into a first depleting compartment of an electrically-driven separation device comprising a circular cylindrical shell. ### Claim 21 (depends on 1) The method of claim 1, further comprising introducing a feed stream into the half-cell concentration compartment. ### Claim 22 (depends on 20) The method of claim 20, further comprising introducing the feed stream counter-currently relative to the direction of the brine solution into the first depleting compartment. ### Claim 23 (depends on 1) The method of claim 1, wherein the brine solution has a total dissolved solids concentration that is at least twice the concentration of total dissolved solids in the seawater.