Use of electrochemical oxidation for treatment of per- and polyfluoroalkyl substances (pfas) in waste generated from sorbent and resin regeneration processes

Abstract

Perfluorinated and polyfluorinated compounds in an effluent stream are destroyed by means of electro-oxidation. Although electro-oxidation can be used to directly treat effluent, a more efficient use is to pre-concentrate applicable pollutants with filters or sorbents. Concentrated perfluorinated and polyfluorinated compounds are removed from the filter or sorbent with a regenerant solution and treated by electro-oxidation. A current density of 0.5 mA/cm 2 or 1 mA/cm 2 effectively reduces the level of perfluorinated contaminants within 1-3 hr. using a titanium electrode. This allows both the regenerant and filter or sorbent to be reused and greatly reduces the amount of material that must be treated as hazardous waste.

1 . (canceled) 
     
     
         2 . A process for destroying perfluoroalkyl and/or polyfluoroalkyl substances in a liquid stream, the process comprising:
 providing a water treatment system including an electro-oxidative (EO) reactor comprising an electrolytic cell with an anode electrode and a cathode electrode, wherein at least one of the anode electrode and the cathode electrode comprises titanium suboxide;   flowing the liquid stream including perfluoroalkyl and/or polyfluoroalkyl substances through the EO reactor; and   contacting the liquid stream including perfluoroalkyl and/or polyfluoroalkyl substances with the anode electrode and the cathode electrode while a current flows between said electrodes, thereby destroying at least some of the perfluoroalkyl and/or polyfluoroalkyl substances by electro-oxidation; and   recirculating liquid treated by the EO reactor within the water treatment system.   
     
     
         3 . The process of  claim 2 , where at least one of the anode electrode and the cathode electrode is selected from the group consisting of titanium suboxide, MnO2, SnO2, PbO2, and Ce—PbO2. 
     
     
         4 . The process of  claim 2 , wherein the liquid stream is selected from the group consisting of waste water, surface water, drinking water and groundwater. 
     
     
         5 . The process of  claim 2 , further comprising emptying the electrolytic cell of liquid and filling the cell with new liquid following destruction of at least some of the perfluoroalkyl and polyfluoroalkyl substances by electro-oxidation. 
     
     
         6 . The process of  claim 2 , wherein the liquid stream flowing through the electrolytic cell is electro-oxidized to destroy concentrated perfluoroalkyl and/or polyfluoroalkyl substances in the liquid stream. 
     
     
         7 . The process of  claim 2 , wherein the liquid stream contains at least 15 parts per million (ppm) of at least one of perfluoroalkyl or polyfluoroalkyl substance before flowing through the EO reactor. 
     
     
         8 . The process of  claim 2 , wherein contacting comprises destroying at least some perfluorooctanoic acid (PFOA) by electro-oxidation. 
     
     
         9 . The process of  claim 2 , further comprising pre-filtering an influent liquid. 
     
     
         10 . The process of  claim 2 , further comprising flowing the liquid treated by the EO through an ion-exchange resin. 
     
     
         11 . The process of  claim 2 , further comprising discharging an excess volume of liquid from the water treatment system. 
     
     
         12 . The process of  claim 2 , wherein the current flowing between the electrodes is between 0.5 mA/cm 2  and 1 mA/cm 2    
     
     
         13 . The process of  claim 2 , wherein flowing the liquid stream including perfluoroalkyl and/or polyfluoroalkyl substances through the EO reactor comprises continuously flowing the liquid stream through the EO reactor. 
     
     
         14 . The process of  claim 2 , wherein flowing the liquid stream including perfluoroalkyl and/or polyfluoroalkyl substances through the EO reactor comprises flowing the liquid stream through the EO reactor in a continuous flow though mode. 
     
     
         15 . The process of  claim 2 , further comprising flowing an influent liquid through a treatment device of the water treatment system before flowing the liquid stream through the EO reactor. 
     
     
         16 . The process of  claim 15 , wherein flowing the influent liquid through the treatment device of the water treatment system comprises flowing the influent liquid through a filter or sorbent. 
     
     
         17 . The process of  claim 16 , wherein recirculating liquid treated by the EO reactor within the water treatment system comprises washing the filter or sorbent. 
     
     
         18 . The process of  claim 16 , wherein the sorbent comprises an ion-exchange resin including a lead contactor and a lag contactor. 
     
     
         19 . The process of  claim 15 , further comprising sampling the liquid stream to test the effectiveness of the treatment device and determining if the effectiveness is decreasing. 
     
     
         20 . A water treatment system for destroying at least one of perfluoroalkyl and polyfluoroalkyl substances (PFAS) in a liquid stream by electro-oxidation, the water treatment system comprising:
 a reactor comprising an electrolytic cell with an anode electrode and a cathode electrode, wherein the anode electrode and the cathode electrode are configured to contact the liquid stream including at least one of perfluoroalkyl and polyfluoroalkyl substances while a current flows between the electrodes, thereby destroying the at least one of the perfluoroalkyl and polyfluoroalkyl substances in the liquid stream by electro-oxidation; and   a fluid circuit in fluid communication with the reactor, the fluid circuit recirculating the liquid treated by the reactor within the water treatment system during operation.   wherein the liquid treated by the reactor is recirculated within the water treatment system.   
     
     
         21 . The water treatment system of  claim 20 , further comprising a treatment device configured to treat influent liquid. 
     
     
         22 . The water treatment system of  claim 21 , wherein the treatment device comprises a filter or sorbent. 
     
     
         23 . The water treatment of  claim 22 , wherein the sorbent comprises an ion-exchange resin including a lead contactor and a lag contactor. 
     
     
         24 . The water treatment system of  claim 22 , further comprising a pump for pumping the liquid treated by the reactor to the treatment device to wash the filter or sorbent. 
     
     
         25 . The water treatment system of  claim 20 , wherein at least one of the anode electrode and the cathode electrode comprises a titanium-based electrode. 
     
     
         26 . The water treatment system of  claim 20 , wherein at least one of the anode electrode and the cathode electrode is selected from the group consisting of titanium suboxide, MnO2, SnO2, PbO2, and Ce—PbO2. 
     
     
         27 . The water treatment system of  claim 20 , wherein a density of the current between the electrodes is between 0.5 mA/cm2 and 1 mA/cm2. 
     
     
         28 . The water treatment system of  claim 20 , wherein the reactor comprises an electro-oxidative (EO) reactor. 
     
     
         29 . The water treatment system of  claim 21 , further comprising a pre-filter configured to filter the influent liquid, the pre-filter positioned upstream of the treatment device. 
     
     
         30 . The water treatment system of  claim 20 , further comprising an ion-exchange resin for treating the liquid treated by the reactor, the ion-exchange resin positioned downstream of the reactor. 
     
     
         31 . The water treatment system of  claim 20 , further comprising a valve configured to discharge an excess volume of liquid stream from the water treatment system. 
     
     
         32 . The water treatment system of  claim 20 , wherein the reactor reduces a concentration of at least one of the perfluoroalkyl and polyfluoroalkyl substances in the liquid stream by at least 77%.