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 electrocoagulation 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.

What is claimed is: 
     
         1 . 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.   
     
     
         2 . The process of  claim 1  wherein the residual oxidant comprises at least one chlorine-based oxidant. 
     
     
         3 . The process of  claim 1  wherein said metal electrode essentially liberates iron ions. 
     
     
         4 . The process of  claim 1  wherein said metal electrode essentially liberates aluminum ions. 
     
     
         5 . The process of  claim 1  further comprising passing the wastewater through an electro-flotation unit after the electro-coagulation unit or before the electro-oxidation unit. 
     
     
         6 . The process of  claim 1  further comprising passing the wastewater through a dissolved flotation unit after the electro-coagulation unit or before the electro-oxidation unit. 
     
     
         7 . The process of  claim 1  wherein an oily wastewater contains more than 15 ppm of oil content and the treated wastewater complies with the international maritime discharge standard for oil content of less than 15 ppm. 
     
     
         8 . The process of  claim 1  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. 
     
     
         9 . The process of  claim 1  further comprising providing and influent combining oily water and sewage and containing more than 15 ppm oil content, more than 35 ppm TSS, more than 25 ppm BOD and more than 100 CFU/100 ml F.C., treating said combined 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 and Oil content lower than 15 ppm. 
     
     
         10 . The process of  claim 1  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. 
     
     
         11 . The process of  claim 1  wherein all treatment agents are generated in-situ, in the wastewater. 
     
     
         12 . The process of  claim 1  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. 
     
     
         13 . The process of  claim 1  further comprising characterizing the physico-chemical properties of said wastewater with various sensors, and, based on said characterization, determining treatment modalities, such as adjusting duration and level of treatment, adjusting the amount of oxidants and bypassing a specific unit. 
     
     
         14 . The process of  claim 1  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. 
     
     
         15 . The process of  claim 1  further comprising adjusting electrochemical parameters such as current and voltage, pulse frequency and duration in each unit based on the level of decontamination of said wastewater in each unit. 
     
     
         16 . The process of  claim 1  further comprising adjusting flow rate of wastewater to and from each unit. 
     
     
         17 . The process of  claim 1  further comprising adjusting time spent in each unit and allowing progression of wastewater to a subsequent unit. 
     
     
         18 . A method for treating a wastewater comprising:
 submitting said wastewater to an oxidation step wherein oxidant level can be controlled; and   submitting oxidized wastewater to an oxidant removal step by passing said wastewater between electrodes connected to an electric source, said electric source causing an at least one sacrificial electrode to release metal ions into said wastewater wherein said metal ions will react with oxidants to generate metal oxides.   
     
     
         19 . The method of  claim 18  further comprising, in said oxidant removal step, decreasing oxidizing molecules by forming metal oxides in said wastewater. 
     
     
         20 . The method of  claim 18  further comprising the step of separating said metal oxide from the treated wastewater.