USING MICROBIAL ECOLOGY IN THE REMOVAL OF METAL CONTAMINANTS BY PASSIVE TREATMENT

Using the hypothesis that the most stable form of metal contaminants is as precipitates of sulfides, carbonates or hydroxides and that these anions are produced as the products of microbial activity, an ecological approach to bioremediation of inorganic contaminants has been developed. Metabolic uptake of the metal is not necessary, bacterial consortia found in typical aquatic environments are used, and special microbes developed in the laboratory are avoided. It is assumed that because these consortia have been operating for eons, they are most efficient at production of desired products and most resistant to contaminants. The best success is in the remediation of waters that contain bicarbonate alkalinity and have toxic concentrations of heavy metals. Using these ideas, passive treatment systems that handle water flows as high as 1200 gpm have been constructed. Recent work has concentrated on finding the slow step in the bacterial process that breaks down natural organic matter for use by sulfate reducing bacteria. It was found that the hydrolysis of cellulose is the rate limiting step in the consortium chain.