Combined electrochemical and biological treatment of industrial wastewater using porous electrodes

Zn²⁺, Ni²⁺ and propylene glycol methyl ether were simultaneously removed from simulated wastewater in a column consisting of an aerated packed bed and an electrochemical cell with a porous aluminium foam cathode and a porous stainless steel anode. After 48 h of sole electrochemical treatment at a liquid rate of 0.00183 m³ m^?2 s^?1, Zn²⁺ and Ni²⁺ were reduced by 95 and 80% respectively. In the turbulent flow regime with liquid rates varied from 0.0137 to 0.0366 m³ m^?2 s^?1, both Zn²⁺ and Ni²⁺ removal decreased by about 15% rather than increased as expected for a mass transfer‐controlled process. This can be attributed to bubble formation at the cathode surface under turbulent flow, which led to a lower active surface area for the electrodeposition of metal ions. Porous electrodes enhanced the metal removal by 17 and 60% for Zn²⁺ and Ni²⁺ respectively as compared with flat plate electrodes. Using combined biological and electrochemical treatment at a water rate of 0.00183 m³ m^?2 s^?1 and an air rate of 0.0518 m³ m^?2 s^?1, 99% of Zn²⁺ and 95% of Ni²⁺ were removed. In addition, the 5 day biological oxygen demand (BOD₅) was reduced by 58% concurrently over 72 h of treatment. Copyright © 2006 Society of Chemical Industry