Page 957 - The Toxicology of Fishes

Case Study: Pulp and Paper Mill Impacts 937

FIGURE 24.3 Photographs of aerated stabilization basins used to treat pulp and paper effluents prior to discharge to aquatic
receiving environments.

Hundreds of compounds have been identified in bleached kraft pulp mill effluents (BKPMEs), and
many remain unidentified due to the complexity of the effluents. Compounds identified to date include
wood-derived carbohydrates, lignin derivatives, organochlorine compounds (chlorinated phenols, cate-
chols, guaiacols, dioxin, furan, and resin and fatty acids), and extractive compounds (resin and fatty
acids, phytosterols, and phenols) (Kringstad and Lindström, 1984; LaFleur and Barton, 2003; Suntio et
al., 1988). BKPMEs are typically treated prior to their release to surface waters. In the 1970s and 1980s,
primary treatment was common and consisted of screening and settling of solids in clarifiers or settling
basins (Folke, 1996; McLeay and Associates, 1987; NCASI; 1989, Smook, 1994). In the 1980s and
1990s, after the implementation of regulations for environmental protection, many mills in Canada and
Scandinavia installed secondary effluent treatment (Folke, 1996; Kovacs et al., 1996, 2003). Secondary
effluent treatment is a biological process in which microorganisms in treatment plants or basins break
down and detoxify biodegradable organics through cellular respiration prior to effluent release (Figure
24.3) (NCASI, 1989; Smook, 1994). This treatment process is controlled to maximize biological activity
by maintaining aerobic conditions and optimal nutrient concentrations in the basins.
Secondary effluent treatment has significantly reduced the environmental impact of PMEs by reducing
the amount of oxygen-consuming biodegradable organics (biochemical oxygen demand [BOD]), the
concentration of chlorinated organic compounds, and acute lethality of the effluent to aquatic organisms
(Kovacs et al., 1996, 2003; LaFleur, 1996; Larsson et al., 2003; McLeay and Associates, 1987; NCASI,
1989). Without question, the most significant changes in the industry have been in bleaching technology
and installation of secondary effluent treatment. It is difficult to determine which of these changes was
more important for improving effluent quality and reducing environmental effects, as these changes
occurred simultaneously at many mills. Suffice to say that both changes were significant, resulted in
immediate improvements in environmental quality, and changed the direction and focus of PME effects
assessment and regulation on an international scale.

History of PME Effects on Fish
A synthesis of field, laboratory, artificial stream, and caging studies examining effects of PMEs is
presented in Table 24.1, Table 24.2, Table 24.3, and Table 24.4. Environmental effects can be summarized
into three historical stages, beginning in the 1950s to present day. From the 1950s to late 1970s, discharge