Tennessee Wastewater Operator Practice Exam

What is the purpose of decanting in an anaerobic digester process?

1. To reduce volatile solids loading

2. To increase the SRT in the digester

3. To clean the digester

4. To separate gas from liquid

The correct answer is: To increase the SRT in the digester

The purpose of decanting in an anaerobic digester process is primarily related to the management of solids and liquid phases within the digester, which correlates with the aim of increasing the Solids Retention Time (SRT). When decanting occurs, it involves removing the liquid phase from the digester while leaving a concentrated mass of solids behind. This process allows for the retention of more solids in the digester, promoting the breakdown of organic material and facilitating the establishment of an optimal environment for microbial activity. By increasing the SRT, operators ensure that microorganisms have more time to digest the organic matter effectively, enhancing the overall performance of the digester. This can lead to improved biogas production and better treatment efficiency. Maintaining an appropriate SRT is crucial for a successful anaerobic digestion process because it directly impacts the digestion rates and the stability of the process. The focus on increasing SRT through decanting demonstrates an understanding of how to optimize the anaerobic digestion process for better treatment outcomes and resource recovery.