Hydrodynamics of a Laboratory Scale Rotating Biological Contactor and Its Application for Decolorization of Textile Dyes by White Rot Fungus Irpex Lacteus

Abstract

Textile industries produce huge amounts of colored wastewaters contaminated with various textile dyes. These waters represent serious environmental problem as common wastewater treatment procedures are not efficient to degrade the dyes. Therefore, new ways of textile wastewater treatment are looked for in order to tackle this environmental problem. An application of the white rot fungus Irpex lacteus, that is known to degrade many recalcitrant pollutants, seems to be one of possible options for the waste water decolorization. A laboratory scale Rotating Biological Contactor was constructed to perform the decolorization tests. The reactor vas equipped with 12 flat circular discs (o = 0.13 m, ?? = 0.01 m) mounted on a common shaft. The discs were made of the Filtren TM30 reticulated polyether foam. Volume of the liquid in the reactor was 1.5 dm3. Residence time distributions of the liquid phase in the reactor were measured to obtain hydrodynamic characteristics. The measurements were carried out at various liquid volumetric flow rates and at different rotational speeds of the discs uncovered with the biomass. The measured data were used to determine the liquid mean residence time and parameters of the gamma distribution model and of the model of the stirred tanks in series with the back-flow. The residence time distributions were also measured after 36 days of the reactor operation, i.e., with the discs covered with the Irpex lacteus mycelium biofilm. The flow behavior of the reactor without the fungus was close to the ideally stirred reactor behavior. The presence of the biomass in the reactor brought about deviations from the ideal mixing. Continuous decolorization experiments with the textile dye Remazol Brilliant Blue R and with a sample of an industrial textile waste water were performed. In the course of the experiments, activities of the enzymes involved in the dye decolorization, i.e., laccase, manganese-dependent peroxidase and lignin peroxidase were determined in the outlet stream of the reactor. The inlet and outlet concentrations of glucose were also measured. The results of the decolorization experiments will be presented and mutually compared and effects of hydrodynamic parameters on decolorization will be discussed.