High recovery electrodialysis method

A system for treating brackish water, the system comprising:

• a first electrochemical separation stage having a dilution compartment inlet fluidly connectable to a source of brackish water, a concentration compartment, a diluate outlet, and a concentrate outlet;
• and
• a second electrochemical separation stage positioned downstream of the first electrochemical separation stage and having a dilution compartment inlet fluidly connectable to the diluate outlet of the first electrochemical separation stage, a concentration compartment, a product water outlet, and a concentrate outlet, the concentrate outlet of the second electrochemical separation stage fluidly connectable to the concentration compartment of the first electrochemical separation stage, the diluate outlet of the first electrochemical separation stage being directly fluidly connected to a first conduit in a recycle loop including a direct fluid connection from the concentrate outlet of the second electrochemical separation stage to a pump and directly from the pump to the concentration compartment of the second electrochemical separation stage, and a second conduit, the second conduit having a direct fluid communication connection with the first conduit, the direct fluid connection of the second conduit with the first conduit being between the concentrate outlet of the second electrochemical separation stage and the direct fluid connection of the diluate outlet of the first electrochemical separation stage to the first conduit, the second conduit providing for the concentrate outlet of the second electrochemical separation stage to be fluidly connectable to the concentration compartment of the first electrochemical separation stage.