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Abstract-Nitrate contamination is a great concern all over the world. However, the conventional biological processes like the modified Ludzack-Ettinger process are time-consuming. Accordingly, a rapid process for nitrate removal is desired. We conceived an electrochemical process for rapid removal of nitrate, which contained electrochemical reduction of nitrate to ammonia and electrochemical break-point chlorination of ammonia. In this research, we investigated effects of operational parameters such as volumetric electric charge, flow rate and chloride ion concentration on electrochemical nitrate removal. A hand-made divided flow cell with a copper mesh cathode, a platinum-coated titanium anode and a cation exchange membrane as a separator was developed as well as applied to the treatment of synthetic water containing 1.42 mM of nitrate at various volumetric electric charges, flow rates and chloride ion concentrations. As a result, it was observed that the flow cell operated at a flow rate of 20 mL/min, chloride ion concentration of 800 mg/L, volumetric electric charge of 5,100 C/L and at pH 7 successfully removed nitrate from 1.42 mM to 0.43 mM without ammonia and nitrite accumulation within 1 minute contact time. Consequently, the electrochemical technique was thought to be feasible for the rapid removal of nitrate from water streams.Index Terms-Break-point chlorination, biological process, electrochemical process, nitrate contamination.

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Depth filtration is a conventional concept for the solid-liquid separation process through granular media, and this technique is very useful in removal of large-sized particle. However, in the case of microparticles smaller than the pore space it does not function well. Accordingly, an effective small particle removal technique is desired. In this research, a carbon fiber felt was introduced as filter media and ± 1.0 V terminal voltage was applied for activating the media to enhance in adsorbing as well as desorbing the fine particles in the filtration and back-washing. Kaolin particles in the range of 0.1-4.0 µm were used as a model of microparticles. The complete kaolin particle removal was observed in pure water, and it decreased to around 50% in the anionic surfactant-contaminated wastewater at the hydraulic loading of 283 L/m 2 /min. On the contrary, at the back-washing hydraulic loading of 1274 L/m 2 /min, the kaolin particle washout removal efficiency was found to be around 73% in pure water and it dramatically decreased and found within the range of 5-50% when the kaolin was in contact with anionic surfactant and wastewater. Although the kaolin particle washout removal rate was observed very low in wastewater, this technique would be very useful in enhancing the refreshment of the filter media for extending the production time of the filter.

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