BIOLOGICAL OXIDATION OF THIOSULFATE IN MIXED HETEROTROPHIC AUTOTROPHIC CULTURES/

The biological oxidation of thiosulfate was examined using aerobic, co ntinuous-flow reactors containing both heterotrophic and autotrophic m icrobial populations. Complete oxidation of thiosulfate at influent co ncentrations up to 600 mg/l as S took place with production of equival ent concentrations of sulfate. Removal of influent chemical oxygen dem and and ammonia as well as nitrification were not adversely impacted b y the presence of thiosulfate. Observed microbial yields were obtained based on experimental data and theoretical yields were calculated bas ed on bioenergetics. Batch kinetic experiments were performed using mi xed liquors from both a thiosulfate-deprived and a thiosulfate-amended continuous-flow reactor. The ability of the thiosulfate-deprived reac tor to oxidize thiosulfate declined with increasing reactor operation time. Thiosulfate oxidation followed Monod kinetics. The following bio kinetic parameter values for the biological oxidation of thiosulfate w ere determined: maximum specific substrate utilization rate (k) 19.8 m g thiosulfate-S/mg VSS-d and half-velocity coefficient(K-s) 14 mg thio sulfate-S/l. (C) 1998 Elsevier Science Ltd. All rights reserved.