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Mercury Removal from Dental Wastewater By a Microbial Bioadsorbent Derived from Genetically Engineered Bacteria.
M. PAZIRANDEH, Naval Research Laboratory, Code 6900 Washington, DC 20375 and M. E. STONE and E. D. PEDERSON,
The mercury content of dental-operatory wastewater has become an issue in many localities, and its removal is rapidly becoming a matter of concern for dental clinics throughout the United States and Europe. The recent promulgation of method 1631 with a detection limit of 0.5 ng Hg/liter (0.5 ppt) will ultimately decrease Publicly Owned Treatment Works discharge limits and make the discharge of mercury from dental clinics more problematic. The objective of this study was to evaluate the effectiveness of a bioadsorbent (Navsorb), derived from genetically engineered bacterium expressing a metal binding motif, for removing mercury from the dental-unit wastewater stream. Dental wastewater was obtained from the Naval Dental Research Institute. Fifty ml samples were incubated with various amounts of the bioadsorbent and the clarified waste was analyzed for total mercury content using standard method 245.1 (detection limit 0.0020 mg Hg/liter). Our results demonstrated that the bioadsorbent effectively removed a significant amount of the mercury from the dental wastewater. An initial mercury content of 3.1 mg/liter was reduced to levels ranging from 0.19-to-0.51 mg/liter using different quantities of the bioadsorbent. This represents decreases in mercury content of from 83.5-to-93.9 percent. Currently, we are investigating the capacity of the bioadsorbent and it’s potential to be utilized in a column operation. These results suggest using the Navsorb bioadsorbent for the removal of mercury from dental wastewater has great potential. Supported by the Great Lakes National Program Office of the United States EPA and the Office of Naval Research. [Journal of Dental Research 79:228 #673, 2000] |