Study on Ammonia-Nitrogen Removal in Wastewater Using Electrochemical Method

In order to evaluate the electrolytic decomposition process of ammonia, the effects of current density and chloride ion were investigated. The Ti/RuO₂- Pt electrode was used as the anode, and Ti electrode as the cathode. The current densities, of 5mA/cm², 10mA/cm², and 15mA/cm², were applied during electrolysis. It was indicated that the ammonia-nitrogen removal efficiency increased with the current density and concentration of the chloride ion in the solution. However, the increment rate became much less when the current density was high enough. In consideration of power consumption and ammonia-nitrogen removal efficiency, the current density of 10mA/cm² and the NaCl addition of 0.3g/L was chosen as the optimum experimental condition, reaching the ammonia removal efficiency of 90.7% after 60 min electrolysis. The concentration of ammonia-nitrogen in the effluent decreased from 49.71 mg/L to 4.62 mg/L. Nitrate and nitrite were also detected during electrolysis and reached peaks at 30 min simultaneously. It was demonstrated that ammonia was decomposed to nitrite firstly and then to nitrate. At the last period of electrolysis (30 min-60 min), both nitrate and nitrite reduced probably for the effects of denitrification.