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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 NH4 + -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. NOTATION E S Energy consumption (kWh m −3 ) U Average cell voltage (V) I Applied current (A) T Electrolysis time (h)

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A static adsorption experiment of copper ion was performed with D851 ion exchange resin to determine some optimum treatment parameters. The results of the experiment showed that the enthalpy value of the reaction was positive and the optimum reaction time was 60 min, while the optimum pH value and reaction temperature were 5.5 and 35˚C, respectively. The adsorption equilibrium density of 0.1 g ion exchange resin was between 75 and 100 mg/L. With the condition of the hydraulic retention time of 60 min, wastewater containing 10 mg/L Cu(II) (pH ≈ 5.5) was treated by a dynamic ion exchange column, and the treatment effluent can meet the primary standard of the National Integrated Wastewater Discharge Standard (GB8978-1996). Meanwhile a desorption experiment with ion exchange resin was carried out, which determined that the optimum volume fraction of hydrochloric acid solution was 4% in the desorption solution. The figures of the scanning electron microscope showed that the resin saturated with Cu(II) could be regenerated well under the effect of hydrochloric acid solution, which was consistent with the experimental results.

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