Electrodesalination System and Method

Abstract

Systems and methods for the desalination of seawater or brackish water for the purpose of obtaining potable water. Systems may include a combination of electrodialysis and electrodeionization modules. The system configuration and process controls may achieve low energy consumption and stable operation.

What is claimed is: 
     
         1 . A desalination system, comprising:
 an electrodialysis (ED) device;   an electrodeionization (EDI) device fluidly connected downstream of the ED device; and   a controller configured to determine an optimum transition point between the ED and EDI devices with respect to power consumption and salt removal, and further configured to bring the EDI device online when a product stream of the ED device achieves the optimum transition point.   
     
     
         2 . The system of  claim 1 , wherein the optimum transition point is based on voltage drop. 
     
     
         3 . The system of  claim 1 , wherein the optimum transition point is based on cell thickness. 
     
     
         4 . The system of  claim 1 , wherein the optimum transition point is based on conductivity. 
     
     
         5 . The system of  claim 1 , wherein the optimum transition point is between about 2500 ppm and about 3000 ppm. 
     
     
         6 . The system of  claim 5 , wherein the optimum transition point is about 2800 ppm. 
     
     
         7 . The system of  claim 1 , wherein the controller is further configured to adjust a pH level of an electrolyte in at least one of the ED and EDI devices. 
     
     
         8 . The system of  claim 1 , further comprising a pretreatment unit fluidly connected upstream of the ED device. 
     
     
         9 . The system of  claim 1 , wherein the controller is further configured to perform a disinfecting or cleaning-in-place operation on at least one of the ED and EDI devices. 
     
     
         10 . A method of providing potable water, comprising:
 fluidly connecting a seawater feed stream to an inlet of an electrical purification system, the system comprising at least a first stage and a second stage downstream of the first stage;   recovering water from the first stage at a first rate;   recovering water from the second stage at a second rate that is less than the first rate; and   fluidly connecting an outlet of the electrical purification system to a potable point of use.   
     
     
         11 . The method of  claim 10 , further comprising maintaining a target concentration gradient between concentrate and dilute compartments in each of the first and second stages. 
     
     
         12 . The method of  claim 11 , further comprising performing multiple dumps of a concentrate stream associated with at least one stage of the electrical purification system. 
     
     
         13 . The method of  claim 10 , further comprising adjusting a pH level of an electrolyte in the electrical purification system. 
     
     
         14 . The method of  claim 10 , further comprising performing a disinfecting or cleaning-in-place operation on the electrical purification system. 
     
     
         15 . The method of  claim 10 , wherein the electrical purification system comprises a capacitive deionization device. 
     
     
         16 . A method of providing potable water, comprising:
 fluidly connecting a seawater feed stream to an inlet of an electrical purification system, the system comprising at least a first electrodialysis (ED) stage and a second ED stage downstream of the first ED stage;   inhibiting concentration polarization by passing a process stream through a dilute compartment in the second ED stage at an increased velocity relative to the first ED stage; and   delivering potable water to a point of use downstream of the electrical purification system.   
     
     
         17 . The method of  claim 16 , wherein the first ED stage includes at least a first pass and a second pass, and wherein the first pass has a different number of cell pairs than the second pass. 
     
     
         18 . The method of  claim 16 , wherein the second ED stage includes at least one blocking spacer. 
     
     
         19 . A desalination system, comprising:
 an electrical purification system comprising at least a first electrodialysis (ED) stage and a second ED stage fluidly connected downstream of the first ED stage;   at least one conductivity sensor associated with the electrical purification system; and   a controller configured to apply a first voltage to the first ED stage and to apply a second voltage, lower than the first voltage, to the second ED stage based on input from the conductivity sensor to inhibit concentration polarization.   
     
     
         20 . The system of  claim 19 , wherein the controller is further configured to adjust the voltage applied to the first ED stage to achieve a target conductivity at an outlet of the first ED stage.