Tennessee Wastewater Operator Practice Exam

What is the approximate oxygen content in air?

1. 15%

2. 21%

3. 25%

4. 30%

The correct answer is: 21%

The approximate oxygen content in air is around 21%. This percentage is significant as it reflects the average composition of Earth's atmosphere, crucial for various biological processes, including respiration in living organisms. The consistent presence of oxygen in this range supports aerobic organisms, which rely on it for energy production through cellular respiration. Understanding the composition of air is essential in wastewater treatment processes, where oxygen levels are critical for the survival of aerobic microorganisms used in the breakdown of waste. Maintaining adequate oxygen levels ensures optimal functioning of treatment systems and effective removal of pollutants. While other percentages may represent theoretical or altered states of oxygen concentration in specific environments (like higher altitudes or controlled scenarios), they do not accurately reflect the typical conditions found in Earth's atmosphere, making the 21% figure universally accepted for standard atmospheric oxygen content.