Digester covers can be which of the following?

• A. Floating
• B. Stationary
• C. Rotating
• D. Floating or stationary

Answer: (D)

Digester covers come in two common configurations: floating and stationary. A floating cover sits on the slurry surface and rises as gas is produced, helping maintain a gas-tight seal and allowing gas collection to adapt to changing gas volumes. A stationary cover is fixed to the tank, forming a constant gas space above the digesting contents, with gas collected through fittings on the cover. Depending on the digester design, space, and maintenance needs, either type may be used, so the correct understanding is that covers can be floating or stationary. Rotating covers are not a typical option for standard digesters.