PRETREATMENT OF KRAFT PULP BLEACH PLANT EFFLUENT BY SELECTED ULTRAFILTRATION MEMBRANES

Three ultrafiltration membranes in series with molar mass cutoffs of 1 30,000, 15,000, and 5,000 Da, respectively were used to pretreat Kraft pulp bleach plant effluent prior to biological treatment. The TOC (to tal organic carbon), COD (chemical oxygen demand) and AOX (adsorbable organic halogen) reductions for the permeate were 65, 70 and 85%, resp ectively with no significant change of toxicity. Treatment of the ultr afiltration permeate using tighter ultrafiltration (UF) and nanofiltra tion (NF) membranes with molar mass cutoffs less than 1,500 Da, yielde d TOC and AOX reductions of 90 and 99%, respectively with a permeate M icrotox EC(50) level of 100%.