# Dynamic Modeling of the Sulfur Cycle in Urban Sewage Pipelines Under High-Temperature and High-Salinity Conditions

## TL;DR

This study models how sulfur cycles in urban sewers under high heat and salt, showing how these conditions affect microbial corrosion.

## Contribution

A novel multiphase kinetic model is developed to predict sulfur speciation in coastal urban sewers under high salinity and temperature.

## Key findings

- Moderate salinity increases sulfate-reducing bacteria activity but excessive sulfide inhibits it.
- At 35 °C, sulfate reduction rates are higher in lower salinity (3 g/L) than higher salinities (19 g/L and 35 g/L).
- High sulfate concentrations enhance sulfide oxidation in anaerobic conditions within specific ranges.

## Abstract

This study addresses the microbial corrosion of cement-based materials in coastal urban sewer networks, systematically investigating the kinetic mechanisms of sulfur biogeochemical cycling under seawater infiltration conditions. Through dynamic monitoring of sulfide concentrations and environmental parameter variations in anaerobic pipelines, a multiphase coupled kinetic model integrating liquid-phase, gas-phase, and biofilm metabolic processes was developed. The results demonstrate that moderate salinity enhances the activity of sulfate-reducing bacteria (SRB) and accelerates sulfate reduction rates, whereas excessive sulfide accumulation inhibits SRB activity. At 35 °C, the mathematical model coefficient “a” for sulfate reduction in the reactor with 3 g/L salinity was significantly higher than those in reactors with 19 g/L and 35 g/L salinities, with no significant difference observed between the latter two. Overall, high sulfate concentrations do not act as limiting factors for sulfide oxidation under anaerobic conditions; instead, they enhance the reaction within specific concentration ranges. The refined kinetic model enables prediction of sulfur speciation in tropical coastal urban sewer pipelines, providing a scientific basis for corrosion risk assessment.