Texas Class C Wastewater Treatment License Practice Exam - Questions and Study Guide

The physical attributes of biological growth on a rotating biological contactor (RBC) can significantly indicate the health and functionality of the biological treatment process. A gray to brown color is generally associated with healthy biofilm growth on the media surface of the RBC. This coloration is typically a result of the presence of diverse microbial populations, including bacteria and protozoa, that thrive in the optimal conditions provided by the RBC system.

Healthy biofilms are crucial for effective wastewater treatment, as they play a key role in breaking down organic matter and pollutants. The gray to brown color typically indicates well-established microbial communities that are efficiently processing wastewater. This growth signifies a balanced environment where microbes are actively metabolizing the nutrients available in the wastewater.

In contrast, other colorations, such as bright yellow and thick biofilm, may suggest potential issues like the presence of unwanted algae or other conditions that are not conducive to optimal wastewater treatment. Similarly, green and transparent or white and fluffy growth patterns might indicate less effective biofilm formations that could lead to inefficiencies in the treatment process or even system failures. Therefore, observing a gray to brown color on the growth surface of an RBC is a strong indicator of a healthy and effective treatment operation.