Decolorization of Congo red dye in a continuously operated rotating biological contactor reactor

Abstract

A continuous study in a rotating biological contactor (RBC) reactor was carried out using polyurethane foam (PU) surface-immobilized with live fungal biomass of Neurospora crassa with wheat bran adsorbent/substrate for the removal of color from synthetic Congo red (CR) dye wastewater. The experiments were conducted at 303 K, pH 6, to study the effect of various operational parameters on the CR dye decolorization process. Experimental data confirmed that the amount of biomass produced and % color removal of CR increased with the increase in the number of discs, disc rotation speed, % disc submergence in the liquid medium, wheat bran dosage, and air flow rate. The maximum color removal of 90.15% was obtained using 50 mg L–1 inlet dyestuff concentration, 20 discs, 16 rpm, 40% disc submergence, 1.5 L min–1 air flow rate, 1 mL min–1 dye solution flow rate and 12.5 g L–1 wheat bran dosage. The activities of various extracellular enzymes of the fungus were measured during the decolorization of synthetic dye wastewater. The results reveal that the cellulase enzyme has a significant role in the decolorization process with its maximum activity and chemical oxygen demand removal being 1,284 U L–1 and 93.34%, respectively at the end of 240 h