To what pH value should wastewater be raised to halt sulfide production?

To effectively halt sulfide production in wastewater, the pH must be raised above 9.0. This is important because under acidic conditions, specifically at lower pH levels, sulfur compounds can undergo anaerobic microbial processes that lead to the production of hydrogen sulfide, which is a highly odorous and toxic gas.

When the pH is raised above 9.0, it creates an environment that is unfavorable for the bacteria responsible for sulfide generation. At this pH, the solubility of hydrogen sulfide decreases, and it exists more in its ionic form as bisulfide or sulfide ions, both of which do not contribute to the same level of odors or toxicity.

In contrast, raising the pH to levels below 7.0 or even around 8.0 does not provide sufficient alkali conditions to stop sulfide production effectively. The option suggesting a pH above 10.0 may also be considered excessive for most wastewater treatment scenarios and can lead to other complications, such as equipment corrosion or the inhibition of beneficial microbial activity. Thus, targeting a pH above 9.0 strikes a balance that effectively reduces sulfide generation while maintaining overall system health.