What accurately describes the operation mode of an oxidation ditch?

The operation mode of an oxidation ditch is accurately described as usually being operated in extended aeration mode for small flows. This operational mode is characteristic of oxidation ditches, which are a type of biological treatment system designed for the treatment of wastewater. In extended aeration, the process allows for the biological treatment of wastewater over a longer duration, which encourages complete degradation of organic material and enhances the removal of solids.

In oxidation ditches, the design allows for a continuous flow of wastewater with aeration provided through mechanical or diffused aeration. This setup promotes the growth of microorganisms that feed on organic pollutants, making it particularly effective for smaller flows where a longer retention time enhances treatment efficiency. The extended aeration process is beneficial for achieving a high level of treatment in terms of biochemical oxygen demand (BOD) and solids removal.

Other operational modes or functions, such as those described in the incorrect options, do not align with the primary use of oxidation ditches. While primary treatment refers to the initial phase of wastewater treatment, oxidation ditches are not designed for this purpose. Operating in batch mode is more typical of certain other treatment processes rather than continuous systems like oxidation ditches. Lastly, while sludge thickening is a part of wastewater treatment processes, it is