Removal of refractory organic compounds in liquid swine manure obtained from a biofiltration process using an electrochemical treatment

Swine wastewaters contain varied and high amounts of organic matter (proteins, antibiotic compounds, organic acids) which are difficult to oxidize biologically or chemically. The discharge of such effluents is undesirable and can cause excessive oxygen demand in the receiving water. In order to produce an effluent suitable for stream discharge, electrochemical techniques have been explored at the laboratory pilot scale, for refractory residual organic compound removal in liquid swine manure (LSM) following a biofiltration process. Two types of electrolytic cells (monopolar and bipolar electrode cells) using aluminum and mild steel electrodes were studied. Effectiveness was measured in terms of chemical oxygen demand (COD) and biological oxygen demand (BOD) reduction. The amount of residue sludge produced and energy consumed have been also considered. Results showed that the best performances of COD and BOD removal from LSM were obtained using either aluminum bipolar (Al-BP) electrodes or mild steel monopolar (Fe-MP) electrodes operated at current intensities of 0.5 and 2.0 A, respectively, through 30 min of treatment. The COD removal yields varied from 65 to 68%, whereas BOD removal reached 87%. The optimal conditions determined for organic compound removal, including energy consumption and metallic sludge disposal, involved a total cost of only $0.24 and $0.29 United States/m3 of treated LSM. The treatment using the Fe-MP system was found to be more economical and practical than the chemical treatment using FeCl3 as a coagulating agent.