Apparatus and method for electrochemical treatment of wastewater

Abstract

The wastewater treatment apparatus of present invention has an electro-coagulation unit for removing contaminants with at least one anode and at least one cathode and an electro-oxidation unit for oxidizing contaminants with at least one anode and at least one cathode wherein oxidants are electrochemically generated. Based on the type of wastewater, the apparatus can have an electro-flotation unit between the electro-coagulation unit and the electro-oxidation unit. The apparatus also has an oxidant removal unit which can have a metal ion-liberating electrode for reacting with and removing residual oxidants. In some cases, portions of effluent from the oxidant removal unit can be recirculated to the electro-coagulation unit for increased efficiency.

1 . An apparatus for treating wastewater comprising:
 an electro-coagulation unit to remove a first portion of contaminants from said wastewater comprising at least one inlet to receive said wastewater and at least one anode and at least one cathode, said anode and said cathode being connected to an electric source;   an electro-oxidation unit to oxidize a second portion of contaminants in said wastewater comprising at least one inlet to receive said wastewater from said electro-coagulation unit, at least one anode and, at least one cathode wherein oxidants are electrochemically generated, at least one outlet to evacuate said wastewater; and   an oxidant removal unit to remove oxidants from said wastewater comprising at least one inlet to receive said wastewater from said electro-oxidation unit, a vessel to contain said wastewater during an oxidant removal process and at least one outlet to discharge treated wastewater from said apparatus.   
     
     
         2 - 3 . (canceled) 
     
     
         4 . The apparatus of  claim 1 , wherein the oxidant removal process further comprises a metal ion-liberating electrode for reacting residual oxidants with said metal ions. 
     
     
         5 . The apparatus of  claim 1 , further comprising a loop between the oxidant removal unit and any other upstream location such that metal oxide from said oxidant removal unit can be delivered to said upstream location. 
     
     
         6 . (canceled) 
     
     
         7 . The apparatus of  claim 1 , further comprising an electro-flotation unit characterized in that at least one anode and at least one cathode are connected to a source of electric current, said electro-flotation unit being downstream from said electro-coagulation unit and upstream from said electro-oxidation unit to insure removal of residual suspended contaminants from the wastewater of said electro-coagulation unit. 
     
     
         8 . (canceled) 
     
     
         9 . The apparatus of  claim 1 , further comprising a boron-doped diamond coated electrode in the electro-oxidation unit. 
     
     
         10 . The apparatus of  claim 1 , further comprising a controller adapted to receive input from one or more sensors for carbon dioxide, oxido-reduction potential, flowrate, pressure, temperature, chlorine, turbidity, pH, conductivity, specific ions and/or surface tension, current and voltage, said controller programmed to control treatment parameters as a function of said input in each unit. 
     
     
         11 - 12 . (canceled) 
     
     
         13 . The apparatus of  claim 1 , wherein said electro-coagulation unit further comprises at least one dividing wall to separate said electro-coagulation unit into at least two independent electro-coagulation compartments that share some peripheral equipment, each said compartment having an inlet and an outlet adapted to deliver partially treated wastewater to any other said unit. 
     
     
         14 - 17 . (canceled) 
     
     
         18 . The apparatus of  claim 10 , wherein said chlorine sensor is configured to be actuated when said oxido-reduction potential sensor reaches a predetermined threshold value. 
     
     
         19 . (canceled) 
     
     
         20 . The apparatus of  claim 1 , further comprising a device for controlling an oxidation reaction as a function of CO2 measurements comprising an oxidation chamber adapted to allow oxidation of wastewater contaminants and a CO2 sensor in fluid communication with said oxidation chamber configured to sends input relative to an amount of CO2 to an oxidation chamber controller for controlling treatment level and/or progression. 
     
     
         21 - 24 . (canceled) 
     
     
         25 . The apparatus of  claim 20 , further comprising an enzymatic or chemical catalyst configured to remove gaseous carbon dioxide evacuated from the oxidation chamber. 
     
     
         26 . A process for treating wastewater comprising:
 electro-coagulating contaminants of said wastewater in an electro-coagulation unit;   electro-oxidizing contaminants of said wastewater in an electro-oxidation unit; and   liberating metal ions from an electrode to react with residual oxidants and produce metal oxides that can be separated from the wastewater in an oxidant removal unit.   
     
     
         27 - 29 . (canceled) 
     
     
         30 . The process of  claim 26 , further comprising passing the wastewater through an electro-flotation unit after the electro-coagulation unit or before the electro-oxidation unit. 
     
     
         31 . The process of  claim 26 , further comprising passing the wastewater through a dissolved flotation unit after the electro-coagulation unit or before the electro-oxidation unit. 
     
     
         32 . The process of  claim 26 , wherein an oily wastewater contains more than 15 ppm of oil content and a treated wastewater complies with the international maritime discharge standard for oil content of less than 15 ppm. 
     
     
         33 . The process of  claim 26 , further comprising providing and influent containing more than 35 ppm Total Suspended Solids (TSS), more than 125 ppm Chemical Oxygen Demand (COD), more than 25 ppm Biological Oxygen Demands (BOD) and more than 100 CFU/100 ml Fecal Coliform (F.C.), treating said influent and discharging an effluent containing TSS lower than 35 ppm, COD lower than 125 ppm, BOD lower than 25 ppm, pH between 6 and 8.5, Chlorine lower than 0.5 ppm and F.C. lower than 100 CFU/100 ml. 
     
     
         34 . (canceled) 
     
     
         35 . The process of  claim 26 , further comprising re-circulating at least part of said metal oxides from said oxidant removal unit to said electro-coagulation unit or any location upstream of oxidant removal unit. 
     
     
         36 . (canceled) 
     
     
         37 . The process of  claim 26 , further comprising generating mixed wastewaters composed of any one or combination of blackwater, graywater and oily water and treating said wastewaters as they are generated on a watercraft. 
     
     
         38 . (canceled) 
     
     
         39 . The process of  claim 26 , further comprising the step of measuring one or more of pH, chlorine content in the liquid and amount of carbon dioxide in the gas evacuated from said oxidation chamber and using the result as a level of decontamination of said wastewater. 
     
     
         40 - 41 . (canceled) 
     
     
         42 . The process of  claim 26 , further comprising adjusting time spent in each unit and allowing progression of wastewater to a subsequent unit. 
     
     
         43 - 47 . (canceled) 
     
     
         48 . The process of  claim 26 , wherein said electro-oxidation further comprises measuring a treatment progress indicator, wherein said indicator is carbon dioxide; and adjusting said oxidation reaction as a function of said indicator. 
     
     
         49 - 56 . (canceled)