What should be the color of an oxidation ditch that is working properly?

An oxidation ditch that is functioning properly should exhibit a medium brown to dark brown color. This coloration results from the presence of activated sludge, which consists of microorganisms that are actively breaking down organic matter in the wastewater. The browning occurs due to the growth of microbial biomass along with the presence of particulate matter and other dissolved organic materials.

As these microorganisms metabolize the pollutants in the wastewater, they form flocs, which aggregate and contribute to the overall coloration. This medium to dark brown color is an indicator of a healthy biological population, as it suggests an effective biological treatment process that is efficiently removing organic material from the water.

Other colors could indicate issues with the system. For example, pale yellow might suggest a lower concentration of organic matter or underperformance in bacterial action, while bright green could signal the presence of excessive algae growth, which can be problematic in an oxidation ditch. A clear ditch may suggest a lack of sufficient biomass or ineffective treatment, indicating that the process may not be achieving its intended goals.