Elemental sulphur production from thiosulphate under haloalkaline conditions in a Thioalkalivibrio versutus amended fluidized bed bioreactor

Potential of biological sulphur recovery from thiosulphate by haloalkaliphilic Thioalkalivibrio denitrificans

The aim of this study was to investigate the potential for elemental sulphur recovery from sulphurous solutions under aerobic and anoxic conditions by haloalkalophilic Thioalkalivibrio denitrificans at 0.8-19.6 g S₂O₃^2--S L^-1 and 0.2-0.58 g NO₂ L^-1, respectively. The experiments were conducted as batch assays with haloalkaline (pH 10 and ≥ 14 g Na⁺ L^-1) thiosulphate solution. Aerobically, the highest biotransformation rate of thiosulphate obtained was 0.03 h^-1 at 8.5 g L S₂O₃^2--S. Based on Monod model, the maximum substrate utilisation rate (q_m) was 0.024 h^-1 with half saturation constant (K_s) 0.42 g S₂O₃^2--S L^-1 at initial [S₂O₃^2--S] of 14 g L^-1. S⁰ accumulated at [S₂O₃^2--S] ≥ 1.5 g L^-1 (10% yield at initial 9.5 g S₂O₃^2--S L^-1) and the highest S⁰ yield estimated with the model was 61% with initial [S₂O₃^2--S] of 16.5 g L^-1. Anoxically, the maximum nitrite removal rate based on Monod modelling was 0.011 h^-1 with K_s= 0.84 g NO₂^- L^-1. Aerobically and anoxically the maximum specific growth rates (µ_m) were 0.046 and 0.022 h^-1, respectively. In summary, high-rate aerobic biotransformation kinetics of thiosulphate were demonstrated, whereas the rates were slower and no S⁰ accumulated under anoxic conditions. Thus, future developments of biotechnical applications for the recovery of S⁰ from haloalkaline streams from the process industry should focus on aerobic treatment.HighlightsHaloalkaline S₂O₃^2- biotransformations kinetics by Thioalkalivibrio denitrificansAerobic thiosulphate-S bioconversion up to 0.024 h^-1 with K_s = 0.42 g S₂O₃^2--S L^-110% S⁰ yield with initial 9.5 g S₂O₃^2--S L^-1 in aerobic conditionAnoxic NO₂ removal up to 0.01 h^-1 with K_s = 0.84 g NO₂^- L^-1.

Enhanced Biodesulfurization with a Microbubble Strategy in an Airlift Bioreactor with Haloalkaliphilic Bacterium Thioalkalivibrio versutus D306

Biodesulfurization under haloalkaline conditions requires limiting oxygen and additional energy in the system to deliver high mixing quality control. This study considers biodesulfurization in an airlift bioreactor with uniform microbubbles generated by a fluidic oscillation aeration system to enhance the biological desulfurization process and its hydrodynamics. Fluidic oscillation aeration in an airlift bioreactor requires minimal energy input for microbubble generation. This aeration system produced 81.87% smaller average microbubble size than the direct aeration system in a bubble column bioreactor. The biodesulfurization phase achieved a yield of 94.94% biological sulfur, 84.91% biological sulfur selectivity, and 5.06% sulfur oxidation performance in the airlift bioreactor with the microbubble strategy. The biodesulfurization conditions of thiosulfate via Thioalkalivibrio versutus D306 are revealed in this study. The biodesulfurization conditions in the airlift bioreactor with the fluidic oscillation aeration system resulted in the complete conversion of thiosulfate with 27.64% less sulfate production and 10.34% more biological sulfur production than in the bubble column bioreactor. Therefore, pleasant hydrodynamics via an airlift bioreactor mechanism with microbubbles is favored for biodesulfurization under haloalkaline conditions.