Stabilization of biogenic elemental sulfur in simultaneous nitrogen and sulfur removal via early-stage inhibition

This study aims to enhance biogenic elemental sulfur (S0bio) recovery efficiency in Simultaneous Nitrogen and Sulfur Removal (SNSR) processes for dual environmental and economic benefits. The addition of thiosulfate to redirect reaction pathways in a Thiobacillus denitrificans-augmented SNSR system elucidates its regulatory mechanism on S0bio yield and stability. Under low sulfide loading (100 mg/L S2-), 30 mg/L S2O32− amendment achieved peak S0bio yield of 69.85% at 36 h, with sulfur conversion efficiency 3.03-fold higher than the high-loading non-inhibited group (NI). The target pathway (S2−→ S0bio) intensity increased by 0.53–1.05-fold, while the competing pathway (S2−→ S2O32-) was inhibited (0.10–0.28-fold reduction). Thiosulfate enabled the S0bio generation pathway to dominate over S2−→ SO42−during early-stage low-sulfide SNSR, reaching a maximum contribution of 55.32%. Additionally, the fluorescence intensity contribution of soluble microbial products (SMP) reached a peak of 49.81%, while concurrent measurements showed significant increases in viable cell count and viability (averaging 2.17-fold and 3.18-fold higher than those in the non-thiosulfate-amended groups, respectively). Thiosulfate synergistically drives efficient S0bio stabilization through dual mechanisms: (1) enhancing Thiobacillus denitrificans bioactivity to intensify key reaction kinetics; (2) optimizing sulfur speciation transformation to establish target-pathway dominance. This work provides technical insights for resource recovery from sulfur-laden wastewater and stable S0bio reclamation.HighlightsEarly-stage inhibition boosts S0bio yield to 69.85% at low sulfide loading with thiosulfate amendment.3.03× higher sulfur conversion efficiency versus high-loading controls via pathway redirection to S0bio generation.Dual regulation: Synergistically enhances Thiobacillus denitrificans activity (↑1.22× viability) and redirects sulfur flux toward S2-→S0bio (55.32% dominance), suppressing competing pathways.Resource recovery strategy enabling stable S0bio reclamation from sulfur-laden wastewater.