CWEA Maintenance Technologist Practice Test 2026 – Complete Exam Prep

The purpose of mixing in reactors during biological treatment is to ensure uniform distribution of microorganisms and substrates. In biological processes, particularly in wastewater treatment, it is critical to maintain a well-mixed environment to facilitate contact between microorganisms and organic matter. This enhances the efficiency of the biological processes, allowing microorganisms to consume the substrates effectively and perform their role in breaking down pollutants.

Uniform mixing helps to maintain a consistent concentration of nutrients and microorganisms throughout the reactor. This prevents the formation of zones that could lead to inefficient treatment or dead spots with little to no activity. Good mixing also ensures that the conditions within the reactor, including pH, temperature, and dissolved oxygen levels, remain optimal for microbial activity, further improving the overall performance of the biological treatment process.

While other options like speeding up chemical reactions or reducing odors might occur indirectly due to mixing, they do not directly capture the primary objective of mixing in the context of biological treatment in reactors. Heating the water might be a part of some processes, but it is not a primary function of mixing.