Advanced treatment of biologically pretreated coking wastewater by electrochemical oxidation using Ti/ RuO 2 –IrO 2 electrodes

Background Electrochemical oxidation has attracted wide attention in wastewater treatment because of its strong oxidation performance and ease of control. This work investigated the feasibility of electrochemical treatment using a Ti/ RuO 2 –IrO 2 anode as an advanced treatment of coking wastewater. The influential operating factors including current density (9.6–108.2  mA  cm −2 ) and electrode gap (0.5–2.5 cm) were evaluated . Results The current density and electrodes gap had significant effects on COD and NH 4 + ‐N removal and the energy consumption. The degradation of COD and NH 4 + ‐N followed pseudo‐first‐order kinetics. In most experiments, high levels of NH 4 + ‐N removal ( NH 4 + ‐N removal ratio > 95%) was achieved along with moderate mineralization ( COD removal ratio: 60–80%). COD (178.0–285.0 mg L ‐1 ) and NH 4 + ‐N (55.0–76.0 mg L ‐1 ) were degraded by 62% and 96%, respectively, at the optimum conditions (electrode gap: 0.5 cm, current density: 15.6  mA  cm −2 ) after 60 min treatment. Under this optimal condition, the corresponding energy consumption was 8.60 kWh m ‐3 for effluent meeting the discharge standards. Furthermore, gas chromatography–mass spectrometry ( GC‐MS ) analysis indicated that this technique could be employed to eliminate bio‐refractory and toxic compounds such as phenanthrene, indole, quinoline and pyrimidine in coking wastewater . Conclusion Ti/ RuO 2 –IrO 2 anode systems were confirmed to be effective in advanced treatment of biologically pretreated coking wastewater. © 2012 Society of Chemical Industry