Florida Wastewater Practice Test

Which method is generally used to increase the efficiency of anaerobic digestion?

1. Increasing temperature

2. Reducing nutrient levels

3. Decreasing solids concentration

4. Enhancing mixing

The correct answer is: Enhancing mixing

Enhancing mixing is crucial in anaerobic digestion because it ensures that the microbial community remains well-distributed throughout the digester. Effective mixing promotes uniform contact between the microorganisms and the organic matter, which increases the rate of digestion and improves overall biogas production. When the contents are mixed properly, it can also help to maintain optimal conditions for the bacteria involved in the anaerobic process, preventing the formation of scum layers that can inhibit gas release and disrupt the digestion process. Furthermore, mixing helps to distribute heat evenly throughout the digester, which is vital in maintaining the optimal temperature for microbial activity. This method differs significantly from those that involve increasing temperature, reducing nutrient levels, or decreasing solids concentration, which may not address the need for improved microbial activity and substrate availability in the same effective manner.