California Wastewater Treatment Operator Practice Exam

What role do microorganisms play in secondary treatment?

1. They increase the temperature of the water

2. They break down organic matter in wastewater

3. They remove heavy metals

4. They coagulate suspended particles

The correct answer is: They break down organic matter in wastewater

Microorganisms are essential in secondary treatment because they are primarily responsible for the biological breakdown of organic matter present in wastewater. During this stage, a variety of bacteria and other microorganisms consume the organic pollutants, converting them into biomass and byproducts that can be more easily removed from the water. This process significantly reduces the amount of biodegradable material in the effluent, resulting in clearer and less polluted water being discharged or treated further. The effectiveness of secondary treatment hinges on maintaining optimal conditions for these microorganisms, including proper aeration, nutrient availability, and retention time. Factors such as oxygen levels are crucial, as many of the microorganisms involved in secondary treatment are aerobic, meaning they require oxygen to thrive and efficiently break down the organic materials. The other options relate to functions that are not the primary roles of microorganisms in secondary treatment. While heavy metals can be addressed through different processes in wastewater treatment, they are typically not removed via biological mechanisms. Similarly, coagulation of suspended particles involves the addition of chemicals and settling processes rather than microbial activity. Lastly, increasing the temperature of the water is not a function of microorganisms within this context; rather, temperature can influence microbial activity but is not a direct role played by them.