|
(18-05) Fate of wood extractives in wastewater treatment plants of ECF and TCF kraft pulp mills and of a mechanical pulp mill. Kostamo, Auli*,1, Holmbom, Bjarne2, Kukkonen, Jussi1, 1 University of Joensuu, Department of Biology, Joensuu, -, Finland2 ABSTRACT- Extensive environmental effects of the forest industry lead to implementation of activated sludge treatment of wastewaters in the 1980's. Although excistence of chlorinated compounds in the effluents have reduced, a discussion on possible environmental effects of ECF and TCF bleached pulp mill effluents has risen and chronic effects on aquatic organisms have still been found. Recently, studies have mainly focused on wood extractives and their role in the effects of effluents. Resin acids and unsaturated fatty acids are found toxic, and plant sterols are reported to have adverse endocrine effects on water organisms already at low concentrations. In this study, we focused on the question how does wastewater treatment plants and especially the activated sludge treatments remove wood extractives. Thus, Finnish wastewater treatment plants of an ECF kraft pulp mill, a paper mill, and an integrated paper mill were sampled. In 2000, the ECF kraft pulp mill produced pulp 608 588 t/a and the integrated TCF kraft pulp mill produced pulp 526 052 t/a. The paper mills produced LWC and SC papers 549 728 t/a and 1 051 955 t/a (the integrate). Concentrations of extractives in discharged wastewaters varied between 0.4 and 11 g/t kraft or mechanical pulp, and the concentrations reduced over 95% during the treatment processes. Of wood extractives, 1.1-64% were adsorbed to biosludge and 35-99% were degraded or transformed to other forms during the activated sludge treatment. Major part of those compounds were discharged in particles (74-99%). Operation stability of biotreatment was not disturbed during a disorder. Key words: activated sludge treatment, wood extractives, pulp mill, paper mill |
bo Akademi University, Process Chemistry Group, Turku, -