Removal of sulfate and heavy metals from acid mine water by anaerobic treatment with cattle waste: Effects of heavy metals on sulfate reduction

Abstract

Acid mine water supplemented with digester slurry of cattle waste was anaerobically incubated, and substrates for and toxicity of heavy metals to sulfate reduction were investigated. Hydrogen and propionate markedly enhanced both sulfate reduction and methanogenesis, while H₂ did not enhance methanogenesis when sulfate reduction proceeded. Degradation of propionate to acetate and enhancement of methanogenesis by propionate occurred only when sulfate reduction proceeded. Acetate markedly enhanced only methanogenesis.

In anaerobic digestion of diluted digester slurry supplemented with propionate or H₂, addition of 1 mM NiCl₂, CuCl₂, ZnCl₂, HgCl₂ or CdCl₂, but not MnCl₂, strongly inhibited sulfate reduction. Concentrations of the heavy metals recovered in a liquid phase of the digestion mixture amended with 1 mM heavy metals were only at the order of 10–100 μ?.

During the anaerobic incubation with propionate, the density of the sulfate reducing bacteria, which was at the level of 10 colony forming units (CFU)/mL or less at the onset of incubation, increased to the level of 10⁶ CFU/mL in the digestion mixture supplemented with 10 mM sulfate, but only to the level of 10²‐10⁴ CFU/mL without sulfate addition. In the digestion mixture amended with 1 mM HgCl₂, the density of sulfate reducing bacteria was suppressed at the level of 10³ CFU/mL despite the addition of sulfate and propionate.