Azo dye mineralization by Phanerochaete chysosporium in a sequencing bath reactor

Abstract

The mineralization of the azo dye congo red by the fungi Phanerochaete chrysosporium was studied in two sequential batch bioreactors (R1 and R2), operated in cycles of 48 h (step I) and 24 h (step II). In step I, glucose concentration was 1 g.L-1 in both reactors and in step II, 1 g.L-1 of glucose was maintained in R1, but R2 received no addition of glucose. In step I, the average dye removal efficiencies were 76 ± 29 % (R1) and 53 ± 15% (R2), while in step II the averages recorded for dye removal for R1 and R2 were 84 ± 15 and 70 ± 28%, respectively. The rates of dye removal were 0.04 h-1 in R1 and 0.03 h-1 in R2 in step I. Higher rates were obtained in step II, 0,07 h-1 and 0,02 h-1 for R1 and R2, respectively. The highest dye removal occurred in R1 and, in R2, the residual dye was further removed. Laccase was the oxidised at higher amount, in step I was 54 mol.min-1 for R1 and 38 molmin-1 for R2. The proposed treatment system was very effective in removing the azo dye, however the mineralization may not be complete and some by-products may have been formed, according to spectrofotometric analysis, were the peak corresponding to benzene, 220 nm, persisted.