The present disclosure describes a flow-electrode capacitive deionization (FCDI) desalination system and method of use. The system employs clusters of tubular membranes oriented parallel to each other, each membrane having an internal flow path capable of receiving an electrolyte slurry (carbon slurry) therethrough. Each tubular membrane further comprises an electrode coaxially extending through the entire length of the electrode. Preferably, adjacent electrodes within the cluster receive a positive or negative charge, respectively. The cluster of tubular membranes is nested within a flow chamber capable of receiving saline or brackish water to be flowed along the outside surfaces of the tubular membranes to cause selected ions, e.g., Na+, Cl— to pass through the membranes and into the carbon slurry circuit. The desalinated water then passes out of the flow chamber. The outer diameter of the electrodes can be optimized based on the inner diameter of the tubular membrane.