Inhibition on acidogenesis of dairy wastewater by zinc and copper

Abstract

Acidogenesis of dairy wastewater produced volatile fatty acids, mainly acetate and propionate, plus hydrogen as byproduct. Zinc (Zn) inhibited acidogenesis at concentrations over 10 mg 1-1; but at 10 mg 1-1, or less, it enhanced acidogenesis slightly. On the other hand, copper (Cu) inhibited acidogenesis at all tested concentrations ranging 5-400 mg 1-1. Production of acetate was inhibited by both metals at all concentrations; but production of propionate and hydrogen was favored at low concentrations of Zn (up to 80 mg 1-1) and Cu (up to 40 mg 1-1). Production of hydrogen corresponded with the degradation of carbohydrate and the production of propionate. Overall, Cu was 1.4-4.3 folds more toxic than Zn, according to the overall production patterns of fatty acids and hydrogen as well as degradation patterns of carbohydrate and protein.