| Abstract |
The U.S. Environmental Protection Agency (EPA) has funded a pilot project to assist small- and medium-size manufacturers who want to minimize their generation of hazardous waste but who lack the expertise to do so. Waste Minimization Assessment Centers (WMACs) were established at selected universities and procedures were adapted from the EPA Waste Minimization Opportunity Assessment Manual (EPA/625/7-88/003, July 1988). The WMAC team at Colorado State University inspected a plant blending and mixing raw materials into paints, coatings, stains, and surface-treating products. For water-based paints, water, latex, resins, extenders, and pigments are mixed and blended. For oil-based paints, solvents replace water and latex, and plasticizers, tints, and thinners are also added. These batches are then transferred to let-down tanks where additional ingredients are incorporated. After testing, the paints meeting specifications are filtered, canned, labelled, and packaged for shipping. Hazardous wastes result when the mixing vessels, let-down tanks, and lines are cleaned. For example, cleaning a let-down tank after a water-based paint has been blended requires about 35 gal water; after a 400-gal tank for a solvent-based paint, about 5 gal mineral spirits. Because the spirits are sent off-site for recovery, most of the waste results from cleaning up after mixing water-based paint. This waste is hazardous because it contains mercury used as the bactericide. Although the plant reuses rinse water, recovers solvent, and has adopted other measures to reduce waste, the team report, detailing findings and recommendations, suggested that additional savings could result from installing a pipe cleaning system, using a solvent-recovery system based on distillation, and substituting an organic material for the mercury bactericide. The Research Brief was developed by the principal investigators and EPA's Risk Reduction Engineering Laboratory, Cincinnati, OH, to announce key findings of
an ongoing research project that is fully documented in a separate report of the same title available from the authors. |
