Tennessee Wastewater Operator Practice Exam

Fixed film processes typically do not remove which substance beyond assimilative uptake?

1. Nitrogen

2. Phosphorous

3. Biochemical oxygen demand

4. Suspended solids

The correct answer is: Phosphorous

Fixed film processes, such as trickling filters or rotating biological contactors, rely on the growth of microorganisms on a solid medium to treat wastewater. These processes are generally effective in reducing biochemical oxygen demand (BOD), suspended solids, and nitrogen levels through both biological uptake by the microorganisms and subsequent breakdown of organic matter. However, when it comes to phosphorus, fixed film processes typically do not manage its removal effectively beyond what can be taken up by the microorganisms. Phosphorus removal is often reliant on the use of additional processes or methods, such as enhanced biological phosphorus removal (EBPR) or chemical precipitation. Since fixed film systems are not specifically designed to remove phosphorus through mechanisms beyond biological uptake, their efficiency in this area is limited compared to other substances. In summary, while fixed film processes excel at reducing BOD, nitrogen, and suspended solids, their capacity to significantly lower phosphorus levels is constrained, making phosphorus the substance that is typically not removed beyond the assimilative uptake in these systems.