Biopulping and Its Potential to Reduce Effluent Loads from Bleaching of Hardwood Kraft Pulp

Mixed hardwood chips were treated with lignin-degrading fungi to study the effect of fungal pretreatment on bleaching characteristics of kraft pulp. Pretreated wood chips were subjected to reduced active alkali doses in comparison to untreated chips. Comparable results were obtained for pretreated chips with reduced alkali dose as was obtained with higher dose of alkali in case of untreated chips. Fungal treatment made the process more energy-efficient, and 4.8% less chlorine was consumed in comparison to the control process. Pretreatment with Ceriporiopsis subvermispora was responsible for reduction of 4.7% in lignin contents, 14.3% permanganate number, and overall reduction of 15.5 kg/T of Cl2 consumption. The pollution load in terms of COD and BOD at the CD stage was reduced by 32.6% and 41.5% respectively, whereas 12% reduction in AOX compounds was observed in effluent of pretreated pulp.