What would be the color of biofilm on a rotating biological contactor under normal operating conditions?

The color of the biofilm on a rotating biological contactor under normal operating conditions is typically gray. This coloration is indicative of a healthy biological process occurring within the system. The gray color results from a balanced community of microbial life, predominantly aerobic bacteria that thrive in environments where oxygen is present, as well as the accumulation of organic material that is being biodegraded.

In a properly functioning rotating biological contactor, the biofilm can also exhibit other subtle hues, depending on the specific microbial population and the conditions in the wastewater treatment process. However, gray is the most common and expected color when the system is functioning correctly and efficiently.

A brown biofilm might suggest excessive organic loading or specific types of bacteria that do not thrive as well in the rotating biological contactor setting. A green color is often associated with the presence of algae, which can imply stagnation or inappropriate conditions for bacterial growth in a biological treatment system. A black color could indicate the presence of anaerobic conditions or concerns with the quality of the biofilm and may signal the need for system evaluation.