The toxicity of pulp and paper mill effluents and corresponding measurement procedures

The impact of pulp and paper discharges on receiving waters results from the integrated action of oxygen demand, suspended solids, pH, color, and toxicity. In this presentation, effects due to toxicity only are examined, even though it is frequently impossible in natural situations to segregate effects due to toxicity from those due to other effluent characteristics. Most of the information comes from laboratory studies carried out under controlled conditions, with Iimited data available concerning the impact of toxicity under conditions in natural ecosystems. The toxicity of any complex effluent results from the combined action of a number of chemical constituents in the waste. Because the toxic chemicals in pulp and paper effluents are not completely identified, their effects must be assessed by a biological measurement. The bioassay is thus used as a quantitative measure of the integrated effect of the toxic materials in pulp and paper discharges. An important part of this study has been to define reproducible bioassay procedures to measure this biological response. It is anticipated that the reader will possess background knowledge concerning pulp and paper processing to appreciate the terminology used to describe the various processes and processing stages relating to effluent origins. Where necessary, the reader is advised to consult standard reference texts (Casey, 1961; Macdonald and Franklin, 1965).