Investigation of treatment of slaughterhouse wastewaters by electrochemical oxidation process

In this thesis, the treatment of slaughterhouse wastewater by electrochemical oxidation process was investigated. The electrode type (graphite, steel and boron doped diamond), chemical pre-treatment (coagulation-flocculation with aluminium sulphate and aluminium chloride hydroxide), initial pH value (in the range of 3-9), and current applied to the electrodes (5- 15 V range) effects were investigated for the removal of chemical oxygen need (COD) from wastewater by electrochemical oxidation process. In addition, the changes in the specific energy consumption of the system in COD removal by these variables were also examined. The highest COD and colour removal were obtained as 91% and 97.8%, respectively, when steel was used as the anode and cathode electrodes. Chemical pre-treatment improved COD and colour removal efficiencies in reactors using boron doped diamond (BDD) electrodes at the anode. For steel (anode)–steel (cathode) electrodes, the highest COD removal was obtained at the original pH value of 7.16, as 91%, and the COD removal efficiency decreased in more acidic and basic conditions. The lowest specific energy consumption was determined as 3.71-5.93 W.h/g COD for the steel (anode)–steel (cathode) electrode pair, depending on time; reducing the current applied to the electrodes from 10 V to 5 V resulted in a specific energy consumption in the range of 0.65-1.63 W.h/g COD. Keywords: Slaughterhouse wastewater, electrochemical oxidation, steel electrode, graphite electrode, BDD electrode, specific energy consumption