REMOVAL OF SULFATE AND HEAVY-METALS FROM ACID-MINE WATER BY ANAEROBIC TREATMENT WITH CATTLE WASTE - EFFECTS OF HEAVY-METALS ON SULFATE REDUCTION

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 H-2 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 H-2, 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-mu-M. 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 10(6) CFU/mL in the digestion mixture supplemented with 10 mM sulfate, but only to the level of 10(2)-10(4) 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 10(3) CFU/mL despite the addition of sulfate and propionate.