California Wastewater Treatment Operator Practice Exam

Which of the following is true about the activated sludge process?

1. It requires a large footprint for installation

2. It does not use biological organisms in the treatment process

3. It is a purely physical treatment process

4. It relies on microorganisms for treatment

The correct answer is: It relies on microorganisms for treatment

The activated sludge process is fundamentally reliant on microorganisms to break down organic matter in wastewater. In this biological treatment method, aeration tanks are used to cultivate a mixed culture of aerobic bacteria and other microorganisms. These organisms consume organic pollutants and convert them into biomass, which is then separated from the treated water in secondary clarifiers. This biological action is essential for effectively reducing the concentration of pollutants, making the role of microorganisms paramount in the process. In contrast, the other options incorrectly characterize the activated sludge process. It does not strictly require a large footprint, as advancements in technology and designs like sequencing batch reactors can optimize space. Additionally, biological organisms play a crucial role in treatment, so the claim about not using them is incorrect. Lastly, the activated sludge process is not purely physical; it incorporates both biological and physical methods for effective wastewater treatment.