Water Quality
We continually work to improve water quality, in particular by reducing biodegradable organic materials in wastewater. When left untreated, biodegradable organic materials can contribute to low dissolved oxygen levels in receiving waters, which may harm some aquatic organisms. High levels of untreated solids, measured as total suspended solids, can reduce river clarity, inhibit photosynthesis, and damage fish and aquatic insect sediment habitat.
We also work to protect water quality in areas where we grow and manage timber. We grade and maintain roads so runoff is channeled to the forest floor, keeping silt away from streams. We build culverts and bridges to allow fish passage, and we seed exposed road banks with grasses to prevent erosion.
Discharge of Adsorbable Organic Halides
Because we no longer use elemental chlorine for pulp and paper bleaching, our discharges of adsorbable organic halides have decreased by more than 92 percent between 1990 and 2006.
- Base year is 1990.
- In March 2007, Weyerhaeuser's fine paper business and related assets were combined with Domtar Inc. to create a new fine paper company, Domtar Corporation. For more information, see our 2006 Annual Report and Form 10-K posted at investor.weyerhaeuser.com.
Wastewater Dioxins
Weyerhaeuser eliminated the use of elemental chlorine to bleach and whiten pulp at all of our mills in the late 1990s. As a result, the concentration of dioxins—-a byproduct of elemental chlorine—has dropped to nondetectable levels in treated mill wastewater across company operations.
In 2006, 93 percent of our bleached pulp was produced using advanced technologies such as extended delignification (removing lignin, a chemical that binds wood fibers together) that further reduce the amount of bleaching chemical used in the production process. These improvements have virtually eliminated dioxins from our wastewater while continuing to meet customer expectations for brightness in our paper products.
Pollution-control systems
Minute amounts of dioxin are released through permitted air emissions, such as from biomass-fired boilers, which burn wood residuals such as bark. Just as campfires release dioxin, so do our mills when we burn biomass fuel. We're addressing the environmental impact through techniques that improve combustion efficiency and temperature controls.
Dioxin is also found in some of the residuals, such as boiler ash, from our mill operations and in some solids that are removed during restoration work on our wastewater-treatment systems. These solids are handled according to federal, state and provincial regulations.
