Combining Electrochemical Nitrate Reduction and Anammox for Treatment of Wastewater With Low C/N Ratio Nitrate

Abstract

The treatment of high concentration and low C/N ratio of nitrate wastewater is a promising and challenging research topic. Combining electrochemical reduction and anammox is a technology with great development potential for nitrogen removal from wastewater. In this work, Cu─Ag─Co cathode materials were prepared by two-step electrodeposition method. The effect of current density and initial pH value on nitrate reduction efficiency was investigated in a single chamber electrolytic cell equipped with Cu─Ag─Co cathode and Ti/RuO₂─IrO₂ anode. The results showed that under the conditions of initial NO₃⁻─N concentration of 500 mg L⁻¹, Na₂SO₄ concentration of 0.125 mol L⁻¹, current density of 10 mA cm⁻², initial pH value of 7, and treatment time of 5 h, NO₃⁻─N removal ratio was 84.5%, the concentration of NO₂⁻─N and NH₄⁺─N was 180.2 mg L⁻¹ and 173.2 mg L⁻¹. Wastewater with a concentration ratio of NO₂⁻─N and NH₄⁺─N of 1.04:1 meets the influent requirements for anaerobic ammonia oxidation. Through the combination process, the final NO₃⁻─N removal ratio was 82.6%, the NO₂⁻─N concentration was 3.2 mg L⁻¹, and the NH₄⁺─N concentration was 26.4 mg L⁻¹. It provided a reference for the treatment of wastewater with low C/N ratio nitrate by combining electrochemical reduction and anammox.