What chemical can cause a decrease in ORP values in wastewater?

A decrease in oxidation-reduction potential (ORP) values in wastewater is often associated with the presence of ammonia. Ammonia is a reduced form of nitrogen that can consume oxygen and reduce the overall oxidative environment of the wastewater. When ammonia is present, it can lead to lower ORP readings because it contributes to a more reducing environment in the water.

In biological treatment processes, ammonia can serve as a substrate for certain microorganisms, leading to a decrease in ORP as these organisms metabolize the ammonia under anoxic or anaerobic conditions. This is essential to understand, as monitoring ORP can help operators assess the effectiveness of the treatment processes and the stability of the microbial community involved in wastewater treatment.

Chlorine generally increases ORP due to its strong oxidative properties. Nitrogen as a broader category includes various forms such as nitrate, which usually increases ORP, while oxygen itself is an oxidizing agent and would typically raise ORP levels rather than lower them.