To experimentally develop and mathematically model a biological process for removing mercury from contaminated waste. This process will be based upon the microbiological reduction and volatilization of mercury. Specific objectives are 1) to establish, experimentally, the process parameters for the continuous removal of mercury in a bioreactor, and 2) to develop a mathematical model based upon the experimental variables and paramters, for integrated process control and for facilitating the eventual scale-up of the process.

Toxic and potentiallly hazardous heavy metals are found in wastewater from industrial sources around Lake Erie. Among these compounds mercury is one of the most toxic and best understood examples of heavy metal pollution. The proposed method of biological detoxification has distinct advantages over other methods currently applied to the mercury problem and this study will lay the groundwork for further biotechnological studies to remove and/or detoxify other toxic metals found in wastewater and sludges.

Determine the effect of nutrient limitation and environmental factors upon the mercury removal characteristics of mixed cultures of bacteria. Optimize the efficiency and kinetics of microbial removal of Hg₂⁺ from contaminated water or sludge under a variety of conditions. Develop a continuous model which can predict the rate and efficiency of the biological reduction Hg₂⁺.

Accomplishments:
1986. Mercury resistant bacteria, which are able to reduce mercuric ion to metallic mercury were examined for their ability to remove mercury from sewage aerobically. A continuous culture of the resistant organism was maintained on raw sewage for two weeks during which time relatively high concentration of mercury (70 mg/1) was removed from the sewage at a rate of 2.5 mg/1 hour and at efficiencies exceeding 98%. We have also applied the biological process to treat industrial sludge from a chlor-akal plant near Lake Erie.

Benefits:
1986. The proposed biological process offers the potential of economically removing and recycling mercury from industrial wastewater and sludges. This research will also have a significant effect on the application of biotechnology to hazardous waste management. The proposed project will lay the groundwork for bio-technological studies to remove and/or detoxify other toxic metals found in wastewater and sludges.

Results:
1986. Detoxifying mercury contaminated waste from an actual industrial sample indicates the feasibility of the biological approach to the control of industrial mercury pollution.