Method and system of electrolytic treatment

Abstract

Electrocatalytic generation of halogenated biocides are disclosed by electrolyzing low salinity water with an applied current. The direction of the applied current is reversed periodically, for a shorter duration, and at a lower current density. Mixed types of electrodes are utilized without a significant reduction in reliability and performance.

1 . A method of providing a biocide, comprising:
 introducing water having a chloride concentration of less than about 6,000 ppm into an electrolyzer;   electrolyzing at least a portion the chloride with a first electric current applied through the electrolyzer in a first direction to produce the biocide; and   passing a second electric current through the electrolyzer in an opposite direction relative to the first direction,   wherein a magnitude of the second electric current is less than a magnitude of the first electric current.   
     
     
         2 . The method of  claim 1 , wherein electrolyzing is a performed for a first duration and passing the second electric current is performed for a second duration less than the first duration. 
     
     
         3 . The method of  claim 2 , wherein the magnitude of the first electric current in the first operating mode is at least twice the magnitude of the second electric current in the second operating mode. 
     
     
         4 . The method of  claim 3 , wherein the electrolyzer comprises at least one primary electrode having an electrocatalytic coating comprising ruthenium oxide, iridium oxide, and titanium oxide disposed on a conductive substrate. 
     
     
         5 . The method of  claim 4 , wherein the electrolyzer comprises at least one secondary electrode having an electrocatalytic coating comprising ruthenium oxide and titanium oxide disposed on a conductive substrate. 
     
     
         6 . A method of modifying a treatment system having an electrolyzer, comprising:
 connecting a controller to the electrolyzer, the controller configured to regulate electric current to the electrolyzer in a first operating mode and in a second operating mode, the first operating mode having primary electric current regulated to a first current level, the second operating mode having an asymmetric electric current at an opposite polarity relative to the primary electric current and at a second current level that is less than the first current level; and   replacing at least one electrode of the electrolyzer with at least one of a carbon-filled polymeric electrode, an electrode comprising an electrocatalytic coating comprising ruthenium oxide, iridium oxide, and titanium oxide, and an electrode comprising electrocatalytic coating comprising ruthenium oxide and titanium oxide.   
     
     
         7 . The method of  claim 6 , further comprising replacing an electrode of the electrolyzer with an electrode comprising an electrocatalytic coating consisting essentially of ruthenium oxide and titanium oxide. 
     
     
         8 . The method of  claim 6 , further comprising replacing an electrode of the electrolyzer with an electrode comprising an electrocatalytic coating consisting essentially of ruthenium oxide, iridium oxide, and titanium oxide. 
     
     
         9 . The method of  claim 6 , further comprising replacing at least one electrode of the electrolyzer with at least one carbon-filled polymeric electrode. 
     
     
         10 . The method of  claim 6 , wherein the controller is configured to regulate the primary electric current to the electrolyzer for a first duration and the controller is configured to regulate the asymmetric electric current for a second duration that is less than the first duration. 
     
     
         11 . An electrolytic water treatment system, comprising:
 an electrolyzer fluidly connectable to a source of water having a salinity of less than about 2.5%, the electrolyzer comprising at least one primary electrode and at least one secondary electrode;   a power supply configured to deliver electrical current to the at least one primary electrode and the at least one secondary electrode; and   a controller configured to regulate the power supply to deliver a first electrical current at a first current level and to deliver a second electrical current at a second current level, wherein the second current level differs from the first current level.   
     
     
         12 . The treatment system of  claim 11 , wherein the controller is configured to regulate the power supply to deliver the first electrical current for a first predetermined duration and to regulate the power supply to deliver the second electrical current for a second predetermined duration that differs from the first predetermined duration. 
     
     
         13 . The treatment system of  claim 12 , wherein the first predetermined duration is at least twice the second predetermined duration. 
     
     
         14 . The treatment system of  claim 13 , wherein the at least one primary electrode comprises a first substrate having a first electrocatalytic coating comprising ruthenium oxide, iridium oxide, and titanium oxide. 
     
     
         15 . The treatment system of  claim 14 , wherein the at least one secondary electrode comprises a second substrate having a second electrocatalytic coating comprising ruthenium oxide and titanium oxide. 
     
     
         16 . The treatment system of  claim 15 , wherein the first electrocatalytic coating consists essentially of ruthenium oxide, iridium oxide, and titanium oxide. 
     
     
         17 . The treatment system of  claim 16 , wherein the second electrocatalytic coating consists essentially of ruthenium oxide and titanium oxide 
     
     
         18 . The treatment system of  claim 11 , wherein the magnitude of the first current level is at least 25% greater than the magnitude of the second current level. 
     
     
         19 . The treatment system of  claim 11 , wherein a polarity of the second electrical current is opposite a polarity of the first electrical current. 
     
     
         20 . The treatment system of  claim 19 , wherein all wetted surfaces of the at least one primary electrode are coated with an electrocatalytic coating comprising ruthenium oxide, iridium oxide, and titanium oxide. 
     
     
         21 . The treatment system of  claim 19 , wherein all wetted surfaces of the at least one secondary electrode are coated with an electrocatalytic coating comprising ruthenium oxide and titanium oxide. 
     
     
         22 . The treatment system of  claim 19 , wherein the at least one primary electrode has a leading edge coated with an electrocatalytic coating comprising ruthenium oxide, iridium oxide, and titanium oxide. 
     
     
         23 . The treatment system of  claim 19 , wherein the at least one secondary electrode has a leading edge coated with an electrocatalytic coating comprising ruthenium oxide and titanium oxide. 
     
     
         24 . The treatment system of  claim 19 , wherein one of the at least one primary electrode and the at least one secondary electrode comprises a carbon-filled polymeric electrode. 
     
     
         25 . The treatment system of  claim 11 , wherein the electrolyzer is fluidly connected to a source of water having a salinity of less than about 0.5%. 
     
     
         26 . An electrolytic system comprising:
 an electrolyzer having a primary electrode and a secondary electrode, at least one of the primary and secondary electrodes having an electrocatalytic coating comprising ruthenium oxide, iridium oxide, and titanium oxide; and   a power supply configured to energize the primary and secondary electrodes in a first mode at a first polarity with a first potential level and a first current level, and to energize the primary and secondary electrodes in an asymmetric mode at a reverse polarity relative to the first polarity, wherein a magnitude of the second potential level differs from a magnitude of the first potential level.   
     
     
         27 . The electrolytic system of  claim 26 , wherein the power supply is configured to energize electrodes in the first mode for a first duration and to energize the electrodes in the asymmetric mode for a second duration that is less than the duration of the first duration. 
     
     
         28 . The electrolytic system of  claim 26 , wherein the primary electrode has an electrocatalytic coating comprising ruthenium oxide, iridium oxide, and titanium oxide. 
     
     
         29 . The electrolytic system of  claim 26 , wherein the secondary electrode has an electrocatalytic coating comprising ruthenium oxide and titanium oxide. 
     
     
         30 . The electrolytic system of  claim 26 , wherein at least one of the one primary electrode and the secondary electrode comprises a carbon-filled polymeric electrode. 
     
     
         31 . A computer-readable including computer-readable signals stored thereon defining instructions that, as a result of being executed by at least one processor, instruct the processor to perform a method of controlling an electrolytic system comprising an electrolyzer fluidly connected to a source of non-thalassic water, the method comprising:
 generating a first control signal that regulates a power supply to provide a primary electrolytic current for a first duration to the electrolyzer; and   generating a second control signal that regulates the power supply to provide an asymmetric current to the electrolyzer for a second duration that is less than the first duration.   
     
     
         32 . The computer-readable medium of  claim 31 , wherein a polarity of the asymmetric current is opposite a polarity of the primary electrolytic current. 
     
     
         33 . The computer-readable medium of  claim 32 , wherein a magnitude of the primary electrolytic current is greater than a magnitude of the asymmetric current. 
     
     
         34 . The computer-readable medium of  claim 33 , wherein the method further comprises controlling a rate of flow of non-thalassic water from the source.