Sequential anaerobic-aerobic decolourization of a real textile wastewater in a two-phase partitioning bioreactor

This work describes the application of a solid-liquid two-phase partitioning bioreactor (TPPB) for the removal of colour froma real textile wastewater containing reactive azo-dyes. Four polymers were tested over the pH range of 4-9 to select the most effective absorbant to be used as the partitioning phase in the TPPB. The best results were obtained with Hytrel 8206 at pH 4 achieving ~70% colour removal, based on the dominant wavelength, in the first 5 h of contact time, and 84% after 24 h. Wastewater treatment was undertaken in a solid-liquid TPPB operated with Hytrel 8206 in sequential anaerobic-aerobic configuration. The reaction time of 23 h was equally distributed between the anaerobic and aerobic phases and, to favour colour uptake, the pH was controlled at 4.5 in the first 4 h of the anaerobic phase, and then increased to 7.5. Colour removal (for the dominant wavelength, 536 nm) increased from 70 to 85% by modifying the bioreactor operation fromsingle-phase to TPPB mode. Based on COD measurements nearly complete biodegradation of the intermediates produced in the anaerobic phase was obtained, both in the single-phase and two-phasemode, with better performance of the TPPB system reaching 75% CODDye removal.