Sulfur-mediated bacteria outperform glycogen-accumulating organisms in carbon-deficient wastewater: Key role of influent C/S0 ratios

Le résumé fourni par la source

Biological nutrient (including nitrogen and phosphorus) removal is often hindered by the lack of organic carbon (C) sources, which can result in the excessive growth of glycogen-accumulating organisms (GAOs), even in sulfate-containing wastewater. Elemental sulfur (S0) has been considered as an economical and energy-efficient electron donor to achieve biological nutrient removal from wastewater. In this study, the long-term effects of C/S0 ratios on the competition between sulfur-mediated bacteria (SMB) and GAOs was investigated to explore the feasibility of using S0 to partially replace carbon and suppress the proliferation of GAOs in biological treatment systems. Four parallel bioreactors were continuously operated for approximately 100 days and fed a substrate consisting of 400, 200, 100, and 0 mg acetate-COD/L, in addition to 0.53 g S0/cycle (equal to 400 mg COD/L); the acetate-COD concentrations corresponded to C/S0 ratios of 0.28 (R1), 0.14 (R2), 0.07 (R3), and 0 (R4), respectively. The results showed that a relatively high C/S0 ratio of 0.28 (in R1) and low C/S0 ratios of 0.07 (in R3) and 0 (in R4) enhanced 1) S metabolism, especially anaerobic S0 reduction to form S2−, which was mediated by sulfate/sulfur-reducing bacteria (SRB/S0RB, e.g., Desulfobacter and Desulfuromonas), or 2) S0 oxidation to form sulfate, which was mediated by sulfur-oxidizing bacteria (SOB, e.g., Thiobacillus) to promote their growth over GAOs (e.g., Candidatus_Competibacter). However, when the C/S0 ratio was 0.14 in R2, this reactor displayed a GAO phenotype rather than a SMB phenotype since GAO communities have a higher acetate uptake rate than SMB. Thus, an appropriate amount of S0 addition supported the competitiveness of SMB over GAOs. Finally, the potential mechanism about competition between the two communities (SMB and GAOs) was revealed. This study provides a new mechanistic strategy to promote the proliferation of SMB over GAOs in carbon-deficient wastewater.

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