Removal of color and COD from dyeing process wastewater using electric arc furnace dust as adsorbent

Abstract

The main objective of this research was to study the removal efficiency of color and COD from dyeing wastewater in the textile industry using Electric Arc Furnace (EAF) dust. A laboratory scale with a continuous model was used to determine the optimum treatment condition by varying contact time, settling time and EAF dust dosages. The contact time was set at 10, 20 and 30 minutes, the settling time at 60, 90 and 120 minutes, and the EAF dust dosages at 200, 250 and 300 g/L. Results indicated that the contact time, settling time and EAF dust dosages were the important operating factors influencing the treatment efficiency of the textile wastewater treatment process. The study showed that when the contact time increased, the color and COD removal efficiencies were significantly increased (P < 0.05), and the concentrations of suspended solids significantly decreased (P < 0.05). However, at 90 minutes settling time, color removal efficiency was significantly greater than at 120 and 60 minutes (P < 0.05). For COD removal efficiency, it was not different at the settling times of 90 and 120 minutes. In addition, it was observed that the concentrations of suspended solids in the effluent decreased as the settling time increased. For the effects of EAF dust, the color and COD removal efficiency significantly increased when EAF dust dosages increased from 200 to 250 g/L, but remained the same at the EAF dust dosage of 300 g/L. The concentrations of suspended solids in the effluent also increased significantly (P < 0.05) when the dosages of EAF dust increased from 250 to 300 g/L. The optimum treatment condition was at the contact time of 20 minutes, 90 minutes settling time and 250 g/L of EAF dust dosages which yielded Color and COD removal efficiencies of 87.35 % and 66.86 %, respectively. Under the optimum condition, the color, COD, SS and Zinc in the effluent all met the required effluent standards stipulated by the Ministry of Industry of Thailand.