Characterization of a Ca-alginate-immobilized Trametes versicolor bioreactor for decolorization and AOX reduction of paper mill effluents

The reduction of color and adsorbable organic halides (AOX) from the kraft bleach plant effluents was investigated using a laboratory-scale fungal bioreactor. The fungal bioreactor, containing calcium-alginate-entrapped white-rot fungus Trametes versicolor, was developed and evaluated for continuous color and AOX reduction. A color reduction percentage of 69% (±6%) and AOX reduction percentage of 58% (±6%) were achieved using caustic stage effluent as bioreactor feed at a residence time of 1 day. Retention time, inlet liquor concentration and fungal bead size were investigated for their effect on biodegradation. Percentage reductions of color and AOX ranging from 61%(±5%) to 72%(±2%) and 54%(±4%) to 49%(±2%), respectively, were observed using combined (caustic and acidic stages) effluent as bioreactor feed. Scanning electron microscopy studies showed that the immobilized mycelia was localized to a limited thickness near the outer surface of the polymer bead.