Wastewater New York State Practice Exam

Which method is commonly used for the biological removal of nitrogen from wastewater?

1. Trickling Filter

2. Activated Sludge

3. Rotating Biological Contactors

4. Sequencing Batch Reactor

The correct answer is: Activated Sludge

The biological removal of nitrogen from wastewater is commonly accomplished through the activated sludge process. This method utilizes a population of microorganisms that thrive in an aerated environment to break down organic matter and convert nitrogen compounds, primarily ammonia, into nitrogen gas, which is then released into the atmosphere. In the activated sludge process, aeration tanks allow for the mixing of wastewater and microorganisms, promoting their growth and activity. During this process, ammonia is oxidized to nitrite and then to nitrate through nitrification, while denitrification occurs in a separate or anoxic stage where nitrate is converted to nitrogen gas. This dual-step process is effective in reducing nitrogen levels in the effluent. While other methods such as trickling filters and rotating biological contactors are used for biological treatment, they are not as efficient as activated sludge for nitrogen removal. Sequencing batch reactors also have the capability to treat nitrogen but are typically less common than the activated sludge process for large-scale operations. Consequently, the activated sludge method stands out as the most widely used technique for biological nitrogen removal in wastewater treatment facilities.