WATER RECOVERY FROM BLEACHED PULP EFFLUENTS

Nanofiltration processing the alkaline bleaching stream in a kraft pul p mill removed organo and organochlorinated compounds of low molecular weight using three types of membranes especially developed for this w ork. Pilot scale tests with organic membranes gave total removal of co lor and 80-90% rejection of organo and organochlorinated compounds. Fu rther development of ceramic membranes is necessary for the same resul ts. Partial demineralization using nanofiltration requires the process ing of nanofiltration permeates by electrodialysis. This combination b rings the NaCl content to 60 ppm and makes possible the production of process water for recycling to the mill.