Characteristics of T-N Removal from Pig Liquid Manure Using a Monopolar Electrochemical Treatment

In this study, the effects of applied voltage, electrode distance, anode material, electrolyte type, and electrolyte concentration on the total nitrogen (T-N) removal efficiency from pig liquid manure were investigated using a monopolar electrochemical treatment system. A batch-type electrochemical reactor with a working volume of 1,000 mL was operated under various experimental conditions, including applied voltage (5-10 V), electrode distance (10-40 mm), anode material (Al, SUS, and Fe), electrolyte type (NaCl, KCl, Na₂SO₄, and NaNO₃ at 5 mM), and electrolyte concentration (5-10 mM). Aluminum electrodes were used as the cathode for all experiments. The experimental results showed that T-N removal efficiency increased with increasing applied voltage, reaching a maximum removal efficiency of 58.77% at 10 V after 60 min of treatment. As the electrode distance increased from 10 to 40 mm, T-N removal efficiency decreased, and the highest removal efficiency was obtained at an electrode spacing of 10 mm due to reduced electrical resistance and enhanced current density. With respect to anode material, the aluminum anode exhibited superior T-N removal performance compared to Fe and SUS anodes, achieving a removal efficiency of 58.77% after 60 min under identical operating conditions. This enhanced performance was attributed to the formation of amorphous Al(OH)₃ flocs with strong coagulation and adsorption capabilities. Electrolyte addition significantly enhanced T-N removal efficiency by improving solution conductivity and promoting electrochemical reactions. Among the tested electrolytes, NaCl showed the highest T-N removal performance, owing to the formation of active chlorine species that facilitated indirect oxidation. The maximum T-N removal efficiency of 86.12% was achieved with 10 mM NaCl after 30 min of treatment, demonstrating that electrolyte type and concentration were critical parameters for optimizing electrochemical treatment of pig liquid manure.