To control odor from hydrogen sulfide, wastewater containing sulfides should be maintained at what pH level?

Maintaining wastewater containing sulfides at a pH level of about 9 is effective in controlling odors related to hydrogen sulfide. At this higher pH level, the solubility of hydrogen sulfide is reduced, and much of the hydrogen sulfide that would otherwise be present in its gaseous form is instead rendered as non-volatile sulfide ions. This diminishes the potential for odor, making it less likely for hydrogen sulfide to escape into the atmosphere.

In contrast, lower pH levels would result in increased solubility and volatility of hydrogen sulfide, leading to stronger odors. A neutral pH (around 7) may also not be sufficient to reduce hydrogen sulfide emissions effectively. Therefore, maintaining the pH around 9 promotes better control over these odorous compounds in wastewater management.