American Water College Practice Test 2026 - Free Practice Questions and Comprehensive Study Guide

Excess filamentous bacteria growth on a rotating biological contactor (RBC) is indicated by the presence of white or gray slime. This coloration is often associated with the accumulation of biofilm, which includes filamentous microorganisms. When filamentous bacteria proliferate excessively, they can lead to operational issues within the wastewater treatment process, such as poor settling characteristics and increased demands on the system.

In the context of wastewater treatment, white or gray slime suggests that the microbial community is dominated by filamentous organisms, which can form a dense and sticky layer on the media. This can impact the efficiency of treatment processes, making it crucial for operators to monitor the color and consistency of this biofilm to ensure optimal system performance. Recognizing this coloration can help in taking corrective actions to restore balance in the system, such as adjusting nutrient levels or providing appropriate aeration.

The other color options such as pink, yellow, or clear do not typically signify excess filamentous growth; rather, they may represent different conditions or types of microbial populations within the system. Identifying and responding to the appropriate indicators, like the white or gray slime, is vital in maintaining effective wastewater treatment practices.