California Wastewater Treatment Operator Practice Exam

Filamentous bacteria is not associated with a trickling filter because trickling filters operate on the principle of fixed film growth, where microorganisms attach to a solid surface (such as plastic or rock media) and treat wastewater as it flows over them. Filamentous bacteria do not form a fixed film and are not commonly found in trickling filters. This type of bacteria is typically associated with activated sludge treatment processes, where they can cause sludge bulking and other operational issues. Therefore, options A, B, and D are all associated with a trickling filter, making C the correct answer.