OXIDATION OF BIOLOGICALLY-PRODUCED SULFUR IN A CONTINUOUS MIXED-SUSPENSION REACTOR

Microbial oxidation of biologically produced elemental sulphur was stu died in a continuous bubble-column reactor. This sulphur was supplied from a sulphide oxidizing bioreactor as a suspension or as a suspended sulphur powder. The work focused on two aspects:(1) investigation of the bio-chemical stability of a biologically-produced sulphur suspensi on when exposed to aeration at pH 8 in a bioreactor, and (2) sulphuric acid production resulting from oxidation of biologically produced sul phur by acidophilic thiobacilli. At pH 8, biomass growth showed an app arent Monod kinetics: At dilution rates of 0.1 up to 0.35 h(-1) 35-40% of easily available sulphur was oxidized. At D <0.1 h(-1), the sulphu r conversion al pH = 8 steeply increased, reaching ultimately values o f 80-90%. In acidophillic conditions in the bioreactor, the maximum su lfuric acid production rate was-searched for. The lowest pH value reac hed in the bioreactor was 1.7, whilst a maximum sulphuric acid product ion rate of 1 mmol H2SO4 . L-1 h(-1) was found. The possible applicati on of the acidification process for bioleaching is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.