Florida Wastewater Practice Test

What is considered normal operation of an anaerobic digester?

1. Continuous agitation

2. Settle and decant as needed

3. Regular addition of chemicals

4. Intermittent feeding

The correct answer is: Settle and decant as needed

The normal operation of an anaerobic digester is characterized by the process of settling and decanting as needed. This method allows the digester to effectively separate the sludge produced during digestion from the supernatant liquid that is generated. In anaerobic digestion, microorganisms break down organic matter in the absence of oxygen, leading to the production of biogas and digestate. After a digestion period, the solids can settle at the bottom, and the clear liquid can be decanted or drawn off, which is essential for maintaining optimal conditions within the digester. This method helps manage the biomass effectively and ensures that the digester operates efficiently by allowing for the removal of treated effluent, which can be further processed or utilized. Moreover, regular settling and decanting prevent overloading the system, which could lead to operational issues. While continuous agitation might seem beneficial for mixing, it is not a necessary part of normal operation, as excessive agitation can hinder the settling process. Similarly, while chemicals can be used in some anaerobic digestion systems, their regular addition is not characteristic of standard operation. Intermittent feeding can be practical in certain scenarios but does not capture the primary operational principle of an anaerobic digester, which is geared towards effective solids handling through