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EVALUATING ACQ AS AN ALTERNATIVE WOOD PRESERVATIVE SYSTEM
Citation:
Chen, A. C. EVALUATING ACQ AS AN ALTERNATIVE WOOD PRESERVATIVE SYSTEM. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-94/036 (NTIS 94-159928), 1994.
Impact/Purpose:
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Description:
This evaluation addresses the waste reduction/pollution prevention and economic issues involved in replacing chromated copper arsenate (CCA) with ammoniacal copper/quaternary ammonium (ACQ) as a way to preserve wood. The most obvious pollution prevention benefit gained by using ACQ is eliminating the use of arsenic and chromium, both of which generate hazardous wastes and a risk of contaminating the environment via chemical spills. Because most treatment plants are self-contained in that they reuse all wastewater produced within the plant and on the drip pads, no liquid waste problems were addressed for either the CCA or the ACQ treating process. The ACQ system generates more air pollution than does the CCA system, mainly as ammonia (NH3). For a plant with an annual production of 1 million ft3 (or about 20 million board feet), 90,000 lb of NH3 would be released per year from the ACQ treatment operations and the ACQ-treated wood. In contrast, a CCA plant in Virginia annually producing four times as much treated wood released <0.021 lb of arsenic (as As205) and only trace amounts of chromium (as CrO3) and copper (as Cuo). During air monitoring of CCA treatment, airborne concentrations of inorganic arsenic were above-the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) of 0.01 mg/m3 . Full-shift personnel exposures to ammonia during ACQ treatment were below applicable exposure limits, but exposures to ammonia during unloading of the ACQ treating cylinder were above the short-term personnel exposure limit of 35 ppm. The treated wood, after being transferred from the drip pads to the outside storage yard, could become a major source of contamination.