Effect of Oxygen Supply on Bioleaching Sediments Contaminated by Heavy Metals

摘要

A bioremediation process for sediments contaminated by heavy metals(Me) has been developed and tested on a pilot scale. In the core stage, solid-bedbioleaching of sediment using elemental sulfur (S°) as leaching agent is performed.Controlled S° oxidation is an essential task for optimizing the bioleaching process. Theeffect of oxygen supply on acidification, S° oxidation and Me solubilization and sulfurrelated yield coefficients was studied in a suspension reactor and a lab-scale percolatorsystem. Variation of oxygen supply was realized by controlling the gas flow and oxygenconcentration in the aeration gas. Oxygen consumption rates during suspension leachingwere not affected until the dissolved oxygen concentration was reduced below 0.05 mg/L.The growth of S° oxidizing autotrophic bacteria was stoichiometrically balancedresulting in Y_(O_2/S) of 1.21 g/g. The oxygen supply varied between 150 and 0.5 mol_(O_2)/mol_(S°)over 28 d of solid-bed leaching. Maximum Me solubilization was reached already at anoxygen supply of 7.5 mol_(O_2)/mol_(S°). Lowering to 0.5 mol_(O_2)/mol_(S°)resulted in retardingacidification and Me solubilization. Both the microbial S° oxidation and Me solubilizationwere correlated with the oxygen supply, revealing that control of the aerationregime offers a suitable means for optimizing solid-bed leaching performance.