From laboratory to field: performance and mechanisms of enhanced ventilation for hydrogen sulfide control in gravity...

Hydrogen sulfide (H₂S) accumulation in sewers threatens occupational safety, infrastructure integrity, and the urban environment. Although ventilation is operationally attractive, its multi-level mechanisms and the translation of laboratory-derived parameters to engineering conditions remain unclear. This study combined laboratory optimization with long-term field validation to evaluate the performance, mechanisms, sulfur-load characteristics, and end-of-pipe implications of enhanced ventilation in gravity sewers. Laboratory experiments using a simulated gravity-flow sewer reactor showed simultaneous decreases in gas-phase H₂S and dissolved sulfide, accompanied by increases in dissolved oxygen, oxidation-reduction potential, and sulfate, together with decreased sulfate-reducing bacteria and increased sulfur-oxidizing bacteria, indicating that the control mechanism extended beyond gas-phase dilution. An S-equivalent assessment showed that 10 min air renewal time combined a lower gas-phase H₂S-S exhaust rate with greater dissolved sulfide depletion, sulfate-S accumulation, and suppression of sulfide production. Field application in a 300 m sewer reach, with an equivalent air renewal time of 8-9 min, reduced mean H₂S concentrations by 92.74% and 85.05% at two fixed monitoring points, while P90 reductions exceeded 84%. Over nearly 8 months of monitoring, time-above-threshold ratios for high-risk concentrations were markedly compressed, H₂S levels declined progressively along the sewer, and concentrations within the ventilation zone remained systematically lower than outside the zone. The near-exhaust H₂S-S load fell from 9.47 to a low of 0.28 g S/h, remaining below the initial operating-stage level during most of the monitoring period. These findings provide a mechanistic basis and practical parameter reference for engineering applications of enhanced ventilation in sewer H₂S management.