California Wastewater Treatment Operator Practice Exam

What type of microorganisms are primarily involved in decomposition during biological treatment?

1. Bacteria

2. Viruses

3. Protozoa

4. Fungi

The correct answer is: Bacteria

Bacteria play a central role in the decomposition process during biological treatment of wastewater. These microorganisms are capable of breaking down organic matter through various metabolic processes, including aerobic respiration in the presence of oxygen and anaerobic digestion in its absence. Bacteria can rapidly multiply and degrade a wide range of organic materials, making them essential in treating wastewater. In biological treatment systems, such as activated sludge processes and trickling filters, bacteria form flocs or biofilms that capture and decompose organic pollutants. This breakdown results in the conversion of these compounds into simpler substances such as carbon dioxide, water, and biomass. While viruses can infect bacteria and play a role in controlling their populations, they do not directly participate in the decomposition of organic matter. Protozoa and fungi also contribute to the decomposition process; however, their impact is mainly complementary to that of bacteria. Protozoa primarily feed on bacteria and help regulate their populations, while fungi are more involved in breaking down complex organic materials, particularly in solid waste composting scenarios rather than in typical biological wastewater treatment. This makes bacteria the dominant microorganisms in biological treatment processes.