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Electrolytic wastewater treatment apparatus

Extracts from this document...

Introduction

Electrolytic wastewater treatment apparatus Abstract A method and apparatus for purifying aqueous effluent streams to reduce chemical oxygen demand thereof, where the method comprises direct oxidation of water-soluble organic material in an electrochemical cell that incorporates stainless steel electrodes, whose stability and lifetime are enhanced by inclusion of circulating metal chips. Claims What is claimed is: 1. An electrolytic oxidation process for purifying wastewater by oxidation of organic and oxidizable inorganic substances contained therein, said process comprising: flowing the wastewater into an electrolytic oxidation cell, where the cell comprises a stainless steel anode and cathode and contains iron chips, said chips being in electrical contact with the anode and prevented from making electrical contact with the cathode by a non-electrically-conductive, liquid-permeable barrier; applying a voltage across the electrodes to energize the electrolytic oxidation cell and effect electrolytic oxidation of organic and oxidizable inorganic substances in the wastewater; and discharging from the electrolytic oxidation cell a treated wastewater having a reduced COD content. 2. The process of claim 1, wherein the voltage applied across the electrodes of the electrolytic cell produce a current of from about 2 to about 20 amperes in the electrolytic cell. 3. The process of claim 1, wherein the wastewater is characterized by a conductivity of from about 200 to about 2000 micro Siemens per centimeter. 4. The process of claim 1, wherein the wastewater is characterized by COD of from about 200 to about 2000 ppm. 5. The process of claim 1, wherein the electrolytic oxidation cell is filled to between 80% and 95% of its volumetric capacity with iron chips. 6. The process of claim 1, wherein the non-electrically-conductive, liquid-permeable barrier comprises a plastic netting. 7. The process of claim 1, wherein the wastewater stream is recirculated through the electrolytic oxidation cell. 8. The process of claim 1, further comprising flowing the wastewater through one or more additional electrolytic oxidation cells in sequence to discharge from a final one of said additional electrolytic oxidation cells a further reduced COD content treated wasterwater. ...read more.

Middle

BRIEF DESCRIPTION OF THE DRAWINGS [0038] FIG. 1 shows a schematic top view of an electrolytic oxidation cell according to the invention. [0039] FIG. 2 is a schematic representation of an electrolytic oxidation wastewater treatment apparatus according to one embodiment of the invention. [0040] FIG. 3 is a schematic representation of an electrolytic oxidation wastewater treatment apparatus according to another embodiment of the invention, employing two electrolytic oxidation cells in series. DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS THEREOF [0041] The present invention relates to an electrolytic purification apparatus and method for treatment of wastewaters to reduce chemical oxygen demand, by oxidation of water-soluble organic and other oxidizable materials in one or more electrochemical cells. The desired electro-oxidation is conducted in one or more electrolytic oxidation cells that employ stainless steel electrodes and contain metal chips. The metal chips are mobile and circulate freely as liquid flows through the cell, so that the metal chips form many, ever-changing electrical contacts with the anode, but are prevented from making electrical contact with the cathode by a non-electrically-conductive but liquid-permeable barrier. [0042] The metal chips thus provide a dynamic and fluid electrode surface that is efficient and resistant to performance degradation. The wastewater may be recirculated through the electrolytic oxidation cell(s) for additional purification. The apparatus may optionally include monitoring devices such as oxygen, pH, and/or conductivity meters, or means to sample the wastewater stream for parameters such as COD. [0043] The electrolytic oxidation cells can be of any suitable shape and volume, as may be readily determined based on the specific wastewater-generating process and/or wastewater stream characteristics involved in a particular end use application of the invention. The cell is fabricated of any suitable material, as is readily determinable by those of ordinary skill in the art without undue experimentation, preferably a material that is strongly resistant to degradation and rupture under the conditions of use. ...read more.

Conclusion

EXAMPLE 2 Treatment of Wastewater from Printed Circuit Board Manufacture [0076] Wastewater from printed circuit board manufacture with a COD reading of 200 ppm was treated in an electrolytic oxidation apparatus of a type as depicted in FIG. 3, employing two cells in a series arrangement. The initial pH of the wastewater was 9.8 and its initial conductance was 1300 .mu.S/cm. The solution was pumped through the cell at a rate of about 1 liter/minute. In the first cell, the voltage was held at 6-8 V and current was 9-12 A. In the second cell, the voltage was 10-12 V and the current was 9-12 A. After passing through the two cells, the outlet stream was tested for COD with a result of 20-50 ppm, corresponding to a COD reduction level of 75% to 90% in the effluent discharge stream, relative to the influent stream COD level. EXAMPLE 3 Treatment of Wastewater from Landfill Seepage [0077] Wastewater which had seeped from a garbage dump landfill site with a COD reading of 250 ppm was treated in an electrolytic oxidation apparatus of the type as depicted in FIG. 2. The initial pH of the wastewater was 9.0 and its initial conductance was 1580 .mu.S/cm. The solution was pumped through the cell at a rate of 1.2-4.0 liters/minute. The voltage was held at 9-9.5 V and current was 4.0-5.0 A. After 5 minutes, the outlet stream was tested for COD with a result of 20-50 ppm, which corresponds to a COD reduction of 80% to 92%. [0078] While the invention has been described herein with reference to various illustrative features, aspects and embodiments, it will be appreciated that the invention is susceptible of variations, modifications and other embodiments, other than those specifically shown and described. The invention is therefore to be broadly interpreted and construed as including all such alternative variations, modifications and other embodiments within its spirit and scope as hereinafter claimed. ...read more.

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