Temperature and pH on microbial desulfurization of sulfide wastewater: From removal performance to gene regulation mechanism

Abstract

Sulfides are widely present in industrial wastewater cause environmental problems like malodorous, corrosive, and toxic. Microbial desulfurization technology has the advantages of ambient conditions, low energy consumption, and enables the recovery of sulfur (S0). These advantages make it the technology of choice for treating middle and low loads of sulfide wastewater. Temperature and pH are two important factors that affect the product selectivity of microbial desulfurization, but the mechanism of these two factors regulating the genes and metabolic pathways of functional microorganisms remains unclear. In this study, a sequencing batch reactor (SBR) treated sulfide-containing wastewater, achieving complete degradation of 400 mg/L influent sulfide at 30 °C and pH 7.5 and showed the best S0 formation efficiency (91.1 ± 2.1 %). The Halothiobacillus genus dominated the microbial community, with the highest abundance (73.0 %) at 30 °C and pH 7.5. Metagenomic analysis showed that at 30 °C and pH 7.5 compared with 20 °C or pH 6.5, the abundance of sulfide oxidation genes (sqr, fccAB) were significantly increased (49.9 % and 43.0 %, 1303.3 % and 139.4 %). Under unfavorable temperature and pH, fccAB gene abundance decreased significantly (92.9 %, 58.2 %), sqr decreased less (33.3 %, 30.1 %), and sox increased significantly (241.0 %, 122.1 %). The dominate sulfide oxidation pathway from flavocytochrome c (FCC) shifted to the sulfide: quinone oxidoreductase (SQR) and sulfur oxidizing system (SOX) pathways. This work highlights the ability of modulating temperature and pH to optimize the biological treatment of sulfide-containing wastewater processes and obtaining more S0, and elucidates their effects on metabolic pathways associated with sulfide oxidation.