In-situ evaluation of predictive models for H₂S gas emission and the performance of optimal dosage of suppressing chemicals in a laboratory-scale sewer

This in-situ analysis quantifies hydrogen sulfide gas emission from a simulated sewerage system, with varying slopes between 0.5% and 1.5%, under the dosing of certain mitigating chemicals. A portable H₂S gas detector (OdaLog) was employed to record the gaseous phase concentration of hydrogen sulfide. The investigation was comprised of three interrelated phases. In the first stage, precision of four prediction models for H₂S gas emission from a laboratory-synthesized wastewater was assessed. It was found that the model suggested by Lahav fitted the experimental results accurately. Second phase explorations included jar tests to obtain the optimal dosage of four hydrogen sulfide suppressing chemicals, being Mg(OH)₂, NaOH, Ca(NO₃)₂, and FeCl₂. In the third stage, the optimal dosage of chemicals was introduced into the experimental sewerage system, with the OdaLog continuously monitoring the H₂S gas emission. According to a baseline (experiments with no chemical addition), it was found that NaOH and Mg(OH)₂ performed very good in mitigating the release of H₂S gas, while Ca(NO₃)₂ was not effective most probably due to the absence of biological activity. Furthermore, interpretation of OdaLog data through the optimum emission prediction model revealed that higher sewer slope led to more emission.