Surveys conducted by municipal wastewater treatment plants across the country have concluded that 10 percent to over 70 percent of the mercury reaching the plants comes from dental offices. These findings, combined with increasingly stringent regulations on mercury discharges, have placed pressure on the dental profession to reduce their discharges of mercury-bearing amalgam. The objective of this project is to enhance the performance of sedimentation-type amalgam separators by controlling the water chemistry within the separator. Dental wastewater contains mercury in three general forms: large particles of amalgam, fine particles of amalgam, and dissolved mercury. Simple sedimentation traps can capture the large particles and many of the fine particles. However, colloidal particles and dissolved mercury can still exceed discharge limits. At present, expensive and maintenance-intensive adsorbents are needed to achieve discharge concentrations in the low-ppb range. During Phase I ADA Technologies showed that safe, inexpensive additives could be used within a sedimentation device to minimize the release of dissolved mercury. In Phase II, we intend to document the effective use of optimized versions of these additives at several dental clinics, demonstrating ppb-level mercury concentrations at costs significantly below those for adsorbent-based processes.
US dentists use some 45 tons of mercury per year for new amalgam fillings. European, Canadian, and some US municipalities limit dental office discharges of mercury. New regulations are pending across North America. Successful completion of this project would yield a low-cost, field-proven amalgam trap, capable of reducing mercury in dental wastewater to the low parts-per-billion range. ADA Technologies will utilize its network of partners and experience in dental waste treatment and equipment manufacturing to bring this enhanced trap rapidly to the marketplace.
