At what pH level does hydrogen sulfide cause the most serious problems?

Hydrogen sulfide (H₂S) is a toxic gas that can cause significant issues in wastewater treatment processes, particularly at lower pH levels. When the pH is below 5, the solubility of hydrogen sulfide increases, leading to higher concentrations in the water. This condition can cause serious problems, such as corrosion of pipes and equipment, as well as toxic effects on both microbial populations and workers handling the wastewater. Additionally, acidic conditions can affect the overall treatment efficiency because many biological processes thrive at neutral pH levels.

In contrast, higher pH levels can lead to reduced solubility of hydrogen sulfide, mitigating some of the related issues. Therefore, managing pH levels to remain above 5 is preferred to minimize the impact of hydrogen sulfide in wastewater treatment systems.