Implementation of two-phase modeling of hydrogen sulfide in fresh market's combined sewers in Rat Burana, Bangkok

Abstract

Hydrogen sulfide (H₂S) is one of the sewer gases commonly found in wastewater collection systems. This anaerobic degradation product causes issues, ranging from odor nuisances and health hazards to pipe corrosion. Several studies have provided an understanding of H₂S formation mechanism, including simulations of H₂S emissions in sewers, especially in pressurized systems. However, the present models necessitate a large amount of data due to the complexity of the H₂S processes and common routine-monitoring water quality parameters may not fit the requirements. This study aims to simulate the fate and transport of H₂S in both air and water phases in combined sewers, with a realization of practicableness of the application. The study case is centered around a fresh market in Bangkok, where the sewers are commonly plagued with garbage-related issues. These challenges pose difficulties for site monitoring across various aspects, necessitating the application of unconventional methods. On-site hydrodynamics, wastewater quality, and H₂S gas concentration data were monitored on hourly and daily bases. It was found that the sulfides in the combined sewerage were correlated with sewage quality, e.g., COD, sulfate (SO₄^2-), and pH concentrations in particular. The model results were in an acceptable range of accuracy (R² = 0.63; NSE = 0.52; RMSE = 1.18) after being calibrated with the measured hydrogen sulfide gas concentration. The results lead to the conclusion that the simplified model is practical and remains effective even in sewers with untraditional conditions. This could hold promise as a fundamental tool in shaping effective H₂S mitigation strategies.

Keywords: Combined sewer system; Garbage; Sewer gases; Simplified model; WATS.