Summary
This report has documented several LBP-removal and management technologies funded entirely or in part through the multiagency Strategic Environmental Research and Development Program (SERDP). The following technologies were developed and demonstrated to reduce the cost of control and abatement of LBP on DoD steel and wooden structures:
Thermal Spray Vitrification. The removal of lead-based primers and paints from steel surfaces as been achieved through a thermal spray vitrification process that uses a glass compound designed for high lead solubility and resistance to chemical leaching. Oxyacetylene flame spray technology was used to apply the glass compound to steel samples containing a commonly used red lead primer. The resulting glass waste was collected and analyzed for lead content using the Toxicity Characteristic Leaching Procedure (TCLP). The results showed that the lead absorbed into the glass was partially vitrified during thermal spray processing, and vitrification was completed by remelting the deposit in a portable onsite furnace. During laboratory testing, lead emissions were determined to fall below the EPA National Ambient Air Quality Standard Limit as well as the OSHA Action Limit for personal exposure. The advantages of the thermal spray vitrification over conventional abrasive blast LBP removal are cost savings that result from the elimination of tight containment, worker health protection measures, and environmental monitoring. Waste disposal costs are also reduced because the vitrified residue from the process is nonhazardous.
Painter-L. This computer-based lead hazard management system provides for the collection and analysis of LBP risk-assessment data, the development of installation lead hazard management plans, and identification of interim and long-term lead hazard control strategies. It also facilitates the tracking of hazards found and remedial actions taken. Painter-L can print the mandatory Disclosure of Information document as new tenants move in, disclosing the extent of any known lead hazard problems and what actions were taken to alleviate the problems. It also enables the collection of ancillary data for worker protection issues.
Evaluation of Emerging Technologies. CERL evaluated emerging environmentally acceptable technologies for LBP removal from nonsteel DoD buildings and structures. During field testing, it was determined that sponge blasting caused unacceptable damage to historical wooden structures.
Blasting technologies based on granulated and pelletized CO2 abrasives proved to be unacceptable for removing LBP from interior wooden components because they caused severe damage to the substrate. However, a wet abrasive blasting technology using an engineered abrasive that incorporates a chemical stabilizer efficiently removed LBP from exterior architectural wood components to bare substrate with no apparent damage, and yielded a surface suitable for repainting without further treatment. Also, encapsulant paint remover technology proved effective in removing LBP from interior wood components down to bare substrate. Six environmentally acceptable (EA) chemical strippers, containing ingredients such as citric acid and the noncaustic, toxicologically benign compound N-methyl pyrrolidone (NMP), were also evaluated, but only the NMP-based strippers performed comparably to traditional solvent-based and caustic strippers.
Microwave-Assisted Paint Removal. This process offers a technically viable solution to problems associated with lead-based paint removal and provides an alternative to currently used technologies that rely either on hazardous chemicals or produce airborne lead-bearing particulates. An extensive series of laboratory experiments was performed in order to investigate the parameters related to proper heating of the paint for easy removal. In particular, the parameters investigated included susceptor type, dwell time, scan rate, equipment safety factors, and the effectiveness of chemical stabilizers. Graphite and polyaniline susceptor materials, applied over the painted surface, were used successfully to absorb microwave energy and heat the paint. The heat softens the paint, which is easily scraped from the substrate. Two prototypes of the microwave paint stripping system have been developed: a high-power system that applies energy to a 2.54 cm square area, and a low-power system that applies energy over a 15 cm square area. Microwave-assisted LBP removal procedures were optimized in the laboratory and successfully demonstrated in the field. The lead levels on the stripped areas of the test substrates were dramatically reduced. When applied according to the optimized procedures and conditions documented here, the microwave-assisted LBP removal process is safe and effective in removing paint in large quantities without burning, discoloring, or otherwise damaging the substrate. It has also been demonstrated that select chemical stabilizers applied in conjunction with the susceptors can render the waste nonhazardous as verified by TCLP testing.
