Abstract
In this study, an electro-oxidation (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 effects 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 for the EO reactor were applied to current density 1 mA/cm2, distance between the electrodes: 2 cm, 150 min operation time, and stirring speed of 500 rpm. At optimum conditions: pH 9.5, applied current density 1 mA/cm2, NaCl dosage of 8 g/L, NaOCl dosage of 44.4 mg/L and 150 min electro-oxidation time, the obtained removal efficiencies were 86.5% and 91.1% for chemical oxygen demand (COD) and ammoniacal nitrogen, respectively. Efficiency was increased to 91.1% for ammoniacal nitrogen from 21.7% after applying EO combined with NaOCl addition compared to individual NaOCl addition.
Highlights
Water resources in the world are decreasing rapidly day by day
The electrochemical reactor was operated under different NaCl amounts (0, 1, 8, and 15 g/L) to investigate salt effect on removal efficiency of chemical oxygen demand (COD), ammoniacal nitrogen, and color
The results showed that COD removal efficiency decreased by increasing the amount of NaCl
Summary
Water resources in the world are decreasing rapidly day by day. Wastewater discharge to receiving environments without any treatment causes pollution of water resources, the amount of which is decreasing day by day. For this reason, wastewater should be treated to preserve existing water resources and to use water resources more efficiently (Muthukumaran et al 2011). Colored textile wastewater accumulation in water bodies damages the aesthetic appearance of the water and reduces the penetration of light into the water. The reduction of light penetration and dissolved oxygen concentration causes extinction of aquatic life and limits the use of water resources. Textile wastewater threatens the environment when it is discharged without any treatment (Pattnaik et al 2018)
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