Organic Discharges from the Manufacture of Bleached Kraft Pulp: Molecular Properties and Environmental Impact, 1998 Environmental Conference Proceedings

Biological treatment installed in all Finnish pulp and paper mills by 1993 removed preferentially smaller (< 1000="" g="" mol’)="" and="" more="" hydrophobic="" halogenated="" compounds,="" but="" left="" the="" c:cl="" ratio="" unchanged.="" mesocosm="" studies="" with="" bkme="" mixed="" in="" lake="" water="" revealed="" that="" 48="" %="" of="" organic="" halogens="" (aox)="" became="" removed="" from="" the="" water="" column,="" from="" which="" 8="" %="" accumulated="" into="" the="" sediment="" within="" one="" year.="" the="" sediment="" formed="" de="" novo="" contained="" (per="" m="" 3="" of="" wastewater)="" 10="" g="" of="" toc,="" 0.6="" g="" of="" ntot="" ,="" 0.1="" to="" 0.4="" g="" of="" bound="" halogen="" (as="" cl),="" 0.03="" g="" of="" halogen="" extractable="" into="" tetrahydrofuran="" and="" 1="" mg="" of="" halogen="" extractable="" into="" heptane.="" the="" sediment-biota="" accumulation="" factor="" (bsaf,="" lumbriculus="" variegutus)="" was="" 0.4="" to="" 0.7,="" similar="" to="" that="" of="" wellknown="" environmental="">

Accumulation of organic halogens into the sediment was linked to drastic increase in hydrophobicity and molecular size. Sediment dating showed that elevated concentrations of 2 to 5 g of EOX (kg d.w.) -1 coincided with the period from 1954 to 1991 when elementary chlorine was used for bleaching. As revealed by unchanged values of 0.6 mg of EOX-Cl per ton of discharged AOX and per rn-’ of lake bottom in sediment layers formed in the years from 1950 to 1990, the half life of this material is longer than 50 years. The polluted layers formed 5 to 20 years ago showed depressed microbial potential (esterase, sulfatase, leucine-aminopeptidase, chitinase, phosphatase) compared to contemporary layers of non-recipient sediment. ß-glucosidase, ß-xylosidase and alpha-glucosidase were less affected and tetrachloromethane dechlorinating activity was stimulated in layers of high organic chlorine content.