Chlorination-assisted coagulation processes for water purification

Abstract

Chlorination-assisted coagulation processes and systems are disclosed for removing organic and inorganic contaminants from aqueous compositions and streams such as produced water generated by petroleum production operations. The chlorination-assisted coagulation process includes converting at least a portion of chloride ions in the aqueous composition to hypochlorite ions or hypochlorous acid by passing an electric current through at least a portion of the aqueous composition under anaerobic conditions, the aqueous composition including the chloride ions, iron (II) compounds, and one or more organic compounds. The chlorination-assisted coagulation process further includes reacting at least a portion of the iron (II) compounds of the aqueous composition with the hypochlorite or hypochlorous acid to produce iron (III) ions, and coagulating the one or more organic compounds with the iron (III) ions to produce a plurality of insoluble solid particles in a treated aqueous composition.

What is claimed is: 
     
         1 . A system for treating an aqueous composition, the system comprising:
 an electro-chlorination system that includes a vessel and a plurality of electrodes disposed within the vessel, the electro-chlorination system operable to convert at least a portion of the chloride ions in the aqueous composition into hypochlorite or hypochlorous acid by passing an electric current through the aqueous composition disposed in the vessel with the plurality of electrodes, where the electrodes each comprise non-sacrificial electrodes having an outer surface that includes one or more of zirconium, molybdenum, gold, silver, tantalum, tungsten, chromium, carbon, sulfur, silicon, or oxides of these materials and the plurality of electrodes are operable to pass the electric current with a current potential greater than 1.5 V through the aqueous composition disposed within the vessel; and   a coagulation vessel downstream of the electro-chlorination system.   
     
     
         2 . The system of  claim 1  further comprising at least one property sensor positioned in the electro-chlorination vessel or downstream of the coagulation vessel. 
     
     
         3 . The system of  claim 1  further comprising a bypass line operable to pass at least a portion of the aqueous composition around the electro-chlorination system and directly to the coagulation vessel. 
     
     
         4 . The system of  claim 1  further comprising a control valve disposed in the bypass line, wherein the control valve is operable to control a flow rate of a portion of an aqueous composition into the electro-chlorination vessel in response to a measured property determined by a property sensor position in the electro-chlorination vessel or downstream of the electro-chlorination vessel.