Efficient sulfur accumulation in biological desulfurisation and denitrification induced by microbial and chemical interactions

Efficient accumulation of sulfur from simultaneous desulfurisation denitrification process can achieve high economic and environmental benefits. This work aims to study the effect of product accumulation on elemental sulfur production and understand its potential mechanism. The addition of the intermediate product thiosulfate and the final product sulfate during the reaction led to an increase in the production of biological elemental sulfur (Sbio0). The effect is mainly reflected in the efficient accumulation effect of Sbio0 at high sulfide loads. When the sulfide feed water load was 300 mg/L, the Sbio0 production reached 65.94 mg/L in 24 h with the addition of 30 mg/L thiosulfate and 20 mg/L sulfate, which was 3.11 times higher than that of the control group. The addition of sulfate increased the content of aromatic protein I and aromatic protein II, and accelerated the propagation of Thiobacillus denitrificans, whose viable bacterial amount was 1.12-2.98 times higher than that of the control group. On the one hand, low-dose sulfate induced Thiobacillus denitrificans to participate in the sulfur-producing reaction (S2-→Sbio0) more quickly by accelerating the propagation of the strains in the pre-reaction stage. On the other hand, the addition of sulfate shifted the overall reaction equilibrium to the left and inhibited the formation of thiosulfate, thus accelerating the accumulation of Sbio0 in the whole reaction stage. This study would provide guidance for artificially promoting efficient sulfur accumulation in desulfurisation denitrification treatments.Highlights The Sbio0 production reached 65.94 mg/L in 24 h at high sulfide load.20 mg/L sulfate induced the rapid propagation of Thiobacillus denitrificans.Thiobacillus denitrificans were involved early in the sulfur-producing reaction.Inhibition of thiosulfate formation indirectly promoted sulfur accumulation.