Texas Wastewater Class B Practice Exam

What gases are primarily produced by the controlled anaerobic digestion of wastewater sludge?

1. Hydrogen and Nitrogen

2. Methane and Carbon Dioxide

3. Oxygen and Carbon Monoxide

4. Ammonia and Sulfur Dioxide

The correct answer is: Methane and Carbon Dioxide

The controlled anaerobic digestion of wastewater sludge primarily produces methane and carbon dioxide as the main end products. Anaerobic digestion is a biological process where microorganisms break down organic matter in the absence of oxygen. During this process, complex organic materials are decomposed, leading to the generation of biogas, which consists mostly of methane—an energy-rich fuel—and carbon dioxide, a common gas produced in many biological reactions. Methane is significant because it can be captured and used as a renewable energy source, while carbon dioxide is a natural byproduct of the digestion process. Understanding the fundamentals of anaerobic digestion is crucial for managing wastewater treatment facilities efficiently and for maximizing energy recovery from waste materials. Other gases listed do not primarily result from anaerobic digestion. For example, oxygen and carbon monoxide are not products of this process, and ammonia and sulfur dioxide are typically not generated in significant quantities during controlled anaerobic digestion. Instead, ammonia could be released as a separate presence in other stages of wastewater processing, while sulfur dioxide may come from other forms of biological degradation involving sulfates.