BIOLOGICAL COLOR REMOVAL OF PULP AND PAPER-MILL WASTEWATERS

The pulp and paper mill effluent is highly coloured. The main contribution to the colour in the effluent comes from the chlorolignin compounds which are discharged from the bleaching step of the manufacturing process. These compounds being non-degradable, by chemical and conventional biological methods, pose problems in the removal of colour. Several methods-physical, chemical and biological-have been attempted for the removal of colour from pulp and paper mill effluents. Physical and chemical methods of colour removal, as per the technology available so far, are quite expensive and less efficient and none is viable practically. Biological colour removal process seems to be attractive since, in addition to colour and chemical oxygen demand, it also reduces biological oxygen demand and low molecular weight chlorolignins. This article reviews the current research on the use of biotechnological methods to remove colour from pulp and paper mill wastewater. The progress made and the further scope are also discussed.