Environmental Trends 2002

Toxic Contaminants

Are Measures to Reduce Pulp and Paper Effluent Effective?

Absorbable Organic Halide (AOX) Discharge in Pulp and Paper Effluent

SOURCE: British Columbia Ministry of Water, Land and Air Protection, 2001. Pollution Prevention and Remediation Branch. NOTES: The report, "A Review of Scientific Basis AOX Effluent Standard in British Columbia", can be found on the internet at www.AOXpanel.ca

Are measures to reduce pulp and paper effluent effective?

• AOX (adsorbable organic halide) is a surrogate measure of the amount of chlorinated organic compounds in pulp and paper effluent discharge.

• In 1992, British Columbia established a legally binding requirement to eliminate AOX from the pulp and paper bleaching process by the end of 2002.

• From 1991 to 1999, average pulp mill AOX discharges were reduced by 83%, from 36.6 to 6.2 tonnes per day.

• A recent scientific review found that there was no evidence to suggest that current reduced levels of AOX discharge present a measurable risk to the aquatic ambient environment.

How are pulp and paper mills in British Columbia mitigating their environmental impacts?

• There are presently 25 pulp and paper mills in British Columbia. Nine of these mills discharge into coastal waters, 13 into inland water bodies, two into municipal sewage systems and one mill evaporates effluent.

• Effluent from mills that do not treat or have minimal treatment, contains high levels of AOX, making it acutely toxic. Acute toxicity kills fish and other species when they come in contact with the effluent.

• Since the early 1990s pulp and paper mills in British Columbia have been adopting new technology that uses chlorine dioxide instead of elemental chlorine to bleach pulp. Mills that are elemental chlorine free (ECF) produce about one tenth the amount of AOX as they had when elemental chlorine was used.

• Mills that use ECF technology and mills that are totally chlorine free still release organic compounds (i.e., black liquor). Black liquor contains the natural chemicals found in wood that has been separated from the wood fibre during the pulp process. When these chemicals are concentrated and released in large quantities to receiving water bodies they can cause chronic toxicity to the aquatic organisms. Chronic or sub-lethal effects may affect an organism's size, growth rate, sexual maturation or ability to reproduce.

For detailed information, including graph data, see In-Depth report [pdf].