Biological leaching of trace metals from stormwater sediments: Influentialvariables and continuous reactor operation

Research was conducted on a bioremediation process for the treatment of urb an stormwater sediments contaminated with trace metals. Referred to as biol eaching, the process relies on specific strains of naturally occurring, aci d-producing bacteria to reduce the pH of a sediment slurry, thereby solubil izing adsorbed and particulate metals into the liquid phase, for collection and processing. The research was first conducted at the bench-scale to inv estigate the process and the influence of the variables substrate loading, solids loading, temperature, starting pH, benefit of inoculation, mixing, a eration and grade of substrate used. Of these, it was found that temperatur e and substrate availability exerted the greatest influence on the acidific ation process. This information allowed for the design of pilot-scale 100 L continuous bioreactors for treating stormwater sediments. At retention tim es as low as 1.3 days, these reactors achieved almost complete solubilizati on of copper and zinc, while chromium and lead were partially removed. Thes e results indicate that bioleaching is a promising alternative for the reme diation of these contaminated sediments. (C) 1998 Published by Elsevier Sci ence Ltd. All rights reserved.