5.3 O&M Tasks

Please note that Standard Operating Procedure (SOP) will vary based on the digester type and complexity of the system and ideally to be shared and introduced via training by the implementer or sanitation expert. To illustrate the task, an example of an underground fixed dome digester is provided.


Feeding of the digester: If the biodigester is directly connected to the toilets, the human faeces flow into the biodigester. The faeces should be flushed with sufficient water to ensure that pipes remain clear. At the same time, too much water should not be used for flushing to avoid dilution. Furthermore, users should be informed not to flush harsh chemicals into the system.

For the semi-centralized treatment unit, the feeding occurs when sludge is delivered for the treatment.

If organic waste is used as co-feedstocks, these feedstocks are usually introduced through an inlet mixing tank.


Cleaning the screen: Using screens is necessary to keep solid waste out of the digester. It’s crucial to consistently examine these screens and remove any solid waste while properly disposing of it.

Mixing Layers in Expansion Chamber: Regularly mixing the swimming and sinking layers in the expansion chamber of fixed dome plants is advised to maintain a homogenous mixture.

Checking and Emptying Water Traps: Verify and empty water traps to prevent blockages and ensure proper gas flow.


Renewing Desulfurization Agents: Monthly renewal of desulphurisation agents helps to maintain effective gas purification and eliminate harmful hydrogen sulphide.

Check for Gas leaks: Check the joint and ventils with a soap water test for gas leaks and flexible pipes for porosity.

Emptying of Effluent Storage Tank: Empty effluent storage tanks if required.


Removing Swimming Layers: Once a year, remove swimming layers from the digester to enhance gas production and prevent scum accumulation.

Pressure Test for Leak Detection: Conduct a pressure test on the entire plant and digester annually to detect any minor leakages and address them promptly.

Biogas Appliances

To effectively operate and maintain a gas appliance, it is important for the manufacturer to provide an SOP for the devices.

For further information, please click on the Materials tab at the top of the page.

Further Reading:

  • Overview of Trouble Shooting (Link)
  • Trouble Shooting p 99 (Link)