How long do solids typically remain in an anaerobic digester?

In an anaerobic digester, solids typically remain for about 15 to 20 days. This duration allows for the optimal microbial activity necessary for breaking down organic matter in the absence of oxygen. During this time, anaerobic bacteria work to degrade the solids, producing biogas as a byproduct. The retention time is carefully managed to ensure that the digestion process is efficient and effective, balancing the need for sufficient breakdown of solids with factors such as the capacity of the digester and the overall time efficiency of the treatment process.

Longer retention times could lead to diminishing returns in the digestion efficiency as the organic material is fully broken down, while shorter times might not allow for complete degradation. Therefore, the 15 to 20-day period is considered ideal for maintaining the health of the microbial population and maximizing biogas production.