Responses of Fathead Minnows (Pimephales Promelas) and Ceriodaphnia Dubia During Life-Cycle Tests with Biologically Treated Kraft Mill Effluents, 1997 Environmental Conference Proceedings

Fathead minnows (Pimephales promelas) were exposed for at least one life cycle to effluent from: 1. a bleached kraft pulp mill with oxygen delignification (OD) and elemental chlorine free (ECF) bleaching, 2. an unbleached kraft pulp mill, 3. a bleached kraft pulp mill with ECF bleaching, and 4. a bleached kraft pulp mill with OD and 70% substitution of ClO2 for Cl2 in the pulp bleaching process, Three or more Ceriodaphnia dubia 7-d tests were completed during each fathead minnow life-cycle test. Effluents were analyzed for components including BOD5 , TOC, AOX, chlorinated phenolic compounds, resin acids and fatty acids. All effluents had effects on reproduction rates of C. dubia and fathead minnows, however IC25s (concentration reducing measured end point by 25%) for egg or young production were always 18% v/v of effluent or greater. Thus the concentrations producing effects in these tests were usually much greater than receiving water concentrations. After normalization for water use the unbleached kraft mill had the least effect on reproduction, however the presence or type of bleaching processes could not be directly correlated to reproduction responses in these tests.