Efficient removal of ammoniacal nitrogen from textile printing wastewater by electrooxidation considering the effects of NaCl and NaOCl addition

Abstract

In this study, electrooxidation (EO) process using graphite electrodes as electrode pairs was used for the removal of chemical oxygen demand (COD), ammoniacal nitrogen (NH4+-N), and color from real textile printing wastewater. The effect of solution pH, sodium chloride (NaCl) dosage, sodium hypochlorite (NaOCl), which is the oldest and still most important chlorine-based bleach, dosage, and oxidation time were investigated on the removal efficiencies. Operating conditions of EO reactor were applied to current density 1 mA/cm(2), distance between the electrodes: 2 cm, 150 min operation time, and stirring speed of 500 rpm. At optimum condition; pH 9.5, applied current desitiy 1 mA/cm(2), NaCl dosage of 8 g/L, NaOCl dosage of 44.4 mg/L and 150 min electrooxidation time, the obtained removal efficiencies were 86.5% and 91.1% for COD and ammoniacal nitrogen, respectively. The efficiency was enhanced to 91.1% for ammoniacal nitrogen from 21.7% after applying EO combined with NaOCl addition compared to individual NaOCl addition.