Regulations Resulting in Cleaner Mill Effluents

Separating the fibres in wood from the non-fibrous materials and turning pulp into paper involves a variety of chemicals—ranging from acids and alkalis to bleaches, dyes, glues, and solvents. Liquid waste produced by these processes contains a mixture of toxic substances and organic matter that can harm aquatic ecosystems if discharged directly into our lakes, rivers, and oceans.

According to a national science assessment conducted by Environment Canada's National Water Research Institute, the addition of secondary wastewater treatment systems at pulp and paper mills across Canada is significantly decreasing the toxicity of mill effluents, although effects are still being seen on fish and their habitat. The assessment is the first to detail the effects of effluent on the receiving environment, based on extensive data collected from across Canada under the Environmental Effects Monitoring (EEM) program.

Both the requirement for secondary treatment and the EEM program were introduced under the Pulp and Paper Effluent Regulations of the Fisheries Act in 1992. The EEM program requires Canada's regulated pulp and paper mills to conduct regular studies to monitor and assess the effects of their effluent on fish, fish habitat, and the use of fisheries resources, using protocols developed by Environment Canada. Every three or four years a cycle is completed, and the mills must provide their results to the Department for further scientific analysis. The results of these analyses are used to determine if regulations are resulting in adequate protection of the environment.

Since the regulations came into effect, discharges of regulated parameters have dropped to a fraction of their pre-control levels and are currently well below limits. Dioxin and furan deposits—which are covered by companion regulations under the Canadian Environmental Protection Act—have declined more than 99 per cent, biochemical oxygen-demand 94 per cent, and total suspended solids 70 per cent. Yet, data show a continuing effect on fish reproduction and signs of mild to moderate nutrient enrichment at most mill sites. Nutrient enrichment occurs when a body of water is overfertilized by the addition of phosphorous and nitrogen.

The EEM program uses a variety of tests to determine the impact of effluents on their receiving environment. Among these are sub-lethal toxicity tests, which measure how organism functions such as growth and reproduction are impacted at various effluent concentrations. Such tests from Cycle-1 (1996) reports indicated that mills without secondary treatment systems had much higher levels of toxicity in their effluent than mills outfitted with such systems. Tests from Cycle 2 (2000) confirmed the trend, showing that after most mills put secondary treatment systems in place, there was a significant decrease in the toxicity of pulp and paper effluent.

Studies of the abundance and diversity of bottom-dwelling invertebrates, such as worms and aquatic insects, are also used as an indicator of the quality of aquatic habitat, because they represent the condition of food available to fish. In both Cycle 1 and Cycle 2, the majority of mills reported significant differences in the structure of the invertebrate community between exposure and reference areas, indicating that most sites receiving effluent had suffered habitat degradation.

In their Cycle-2 reports, the majority of mills reported that the magnitude of these differences had lessened. However, data show that an increase in the number (and, in some cases, diversity) of invertebrates is still commonly observed at mill sites across Canada. These effects are a well-known sign of mild to moderate nutrient enrichment.

Fish population surveys are used to monitor fish in the receiving waters where mills discharge effluent, and to compare them to fish from a reference area not exposed to mill effluent. In both cycles, such comparisons showed statistically significant differences in at least one of three key measurements at the majority of sites, and about half the mills reported differences in all three.

The predominant national trend was a significant decrease in gonad weight and significant increases in liver weight, fish fatness, and "weight at age." The first of these effects relates directly to reproduction, and the other three to growth. The larger, fatter fish response pattern is consistent with the effects of mild to moderate nutrient enrichment on the invertebrate community, indicating an increase in food availability for the fish. The decrease in gonad size is believed to be indicative of some form of metabolic disruption—that is, a disruption in the mechanism the body uses to synthesize and break down complex substances. Such a disruption can cause serious imbalances in the maturation, sexual behaviour, and growth of an organism. Although the mechanisms of such responses and their ecological importance remains unclear, these patterns of effects on a national scale may be related to some form of disruption of endocrine functioning, which is key to growth and reproductive development.

The impact of effluent from pulp and paper mills on fisheries resources is evaluated through tainting tests, which are designed to determine if the taste of the fish is affected, and through the analysis of dioxin and furan levels in edible fish-tissue, to determine if levels exceed Health Canada consumption guidelines. Dioxins and furans are analyzed only at mills that use bleaching chemicals.

Mill effluent is suspected of causing the tainting of fish at both of the mills that conducted tainting tests in Cycle 2. Since dioxin and furan levels were found to be very low at most of the more than 40 mills that reported on these levels in Cycle 1, only 10 mills were required to conduct this analysis in Cycle 2. Six of these mills showed levels of dioxins and furans in fish tissue that exceeded guidelines. However, the source of these pollutants is believed to be the historic contamination of the sediment, not the current effluent.

Further research and continued EEM studies are required to understand these phenomena and to confirm the type, spatial extent, and ecological importance of these observed effects. Environment Canada will continue to work with industry and other stakeholders to better understand their significance. The deadline for the submission of Cycle-3 reports is April 2004.

Results of sub-lethal toxicity tests conducted on sand fleas during cycles 1 and 2 of the EEM, during which the fleas were exposed to concentrations of effluent from pulp and paper mill sites across Canada. The vertical bars indicate the percentage of tests conducted in each cycle in which the sand fleas exhibited a 25 per cent decrease in function at that threshold of concentration. A significant percentage of tests carried out during Cycle 1 showed this effect at concentrations of effluent of less than 0.36 per cent; however, during Cycle 2, approximately 26 per cent of tests did not show this effect until concentrations equal to or greater than 100 per cent effluent.

  Home |  Air |  Atmospheric Science |  Climate Change |  Environmental Action |  Habitat |  Pollution |  Species at Risk |  Technology |  Water |  Weather |  Wildlife