Sequential use of the electrocoagulation-electrooxidation processes for domestic wastewater treatment

Nowadays, the decrease in useable water resources day by day necessitates studies on the protection of resources by treating wastewater. It is also one of the best options for reusing the water to be treated, and electrochemical technologies can be an alternative to existing technologies, because of the easy operation and effectiveness of pollutants treatment. The study evaluated the treatment of domestic wastewater by Electrocoagulation-Electrooxidation successive processes in continuous and batch modes. The effects of the operational parameters on the Electrocoagulation and Electrooxidation processes were determined for removals of chemical oxygen demand, ammonium-nitrogen, nitrate-nitrogen, turbidity, phosphate-phosphorus, nitrite-nitrogen, and Escherichia coli. The experiments revealed that the Electrocoagulation process effectively removed all pollutants but not ammonium-nitrogen. After the Electrocoagulation process was completed, ammonium-nitrogen from domestic wastewater treatment was removed with the Electrooxidation process for further treatment. The optimum operational conditions in the Electrocoagulation process were electrode type iron anode-carbon felt cathode, current density 100 A m⁻², initial pH original, and operation time 20 min. Under these conditions, removal efficiencies of chemical oxygen demand, turbidity, phosphate-phosphorus, nitrate-nitrogen, nitrite-nitrogen, and Escherichia coli were found to be 90.2%, 96%, 88.2%, 73.6%, and 97.9%, respectively. The removal efficiencies for the optimum operating conditions of the Electrooxidation process using Ti/SbO₂ anode and stainless steel cathode were obtained as 95.4% (chemical oxygen demand), 89.4% (ammonium-nitrogen), and 99.99% (Escherichia coli) at 100 A m⁻², 5 mm electrode distance, and 30 min operation time. Finally, the EC process is an effective process for removing chemical oxygen demand, phosphate-phosphorus, turbidity, nitrite-nitrogen, and nitrate-nitrogen. However, the Electrooxidation process is a successful process for the treatment of ammonium-nitrogen and Escherichia coli. This research revealed that the sequential processes effectively removed organic, inorganic, and Escherichia coli from domestic wastewater.