Tennessee Wastewater Operator Practice Exam

How much oxygen is needed to destroy 1kg of volatile solids and convert the released ammonia to nitrate?

1. 1.0kg

2. 1.5kg

3. 2.0kg

4. 2.5kg

The correct answer is: 2.0kg

The correct amount of oxygen needed to destroy 1 kg of volatile solids and convert the released ammonia to nitrate is 2.0 kg. This calculation takes into account both the biochemical oxygen demand (BOD) associated with the decomposition of volatile solids and the additional oxygen required for the nitrification process. When organic matter, such as volatile solids, breaks down, oxygen is consumed. Specifically for converting ammonia to nitrate through nitrification, two groups of bacteria are involved: ammonia-oxidizing bacteria that convert ammonia to nitrite, and nitrite-oxidizing bacteria that further convert nitrite to nitrate. The entire process of nitrification consumes oxygen as ammonia is oxidized. Typically, the conversion of 1 kg of volatile solids requires about 1.42 kg of oxygen, and the nitrification process requires additional oxygen, generally around 0.57 kg, bringing the total requirement to approximately 2.0 kg of oxygen. This is why the choice of 2.0 kg is validated as the correct answer.