An electrochemical cell includes a housing having an inlet, an outlet, and a central axis and an anode-cathode pair disposed concentrically within the housing about the central axis and defining an active area between an anode and a cathode of the anode-cathode pair. An active surface area of at least one of the anode and the cathode has a surface area greater than a surface area of an internal surface of the housing. The anode-cathode pair is configured and arranged to direct all fluid passing through the electrochemical cell axially through the active area.