Replacing a submerged agitator in a digester can be quite a complex task, but it can be done by following these steps:

1. Turn off the power: It is important to shut down the digester components before replacing the agitator for safety reasons. Make sure all valves are closed and the power is off.

2. Empty the digester: empty the digester to the height necessary to free the agitator and allow intervention.

3. Remove the agitator: Remove the agitator by disconnecting all hoses and electrical connections. It is important to follow the manufacturer's instructions for safe agitator removal.

4. Install the new agitator: Install the new agitator following the manufacturer's instructions. Make sure all connections are properly tightened and all valves are open.

5. Test the agitator: Once the new agitator is installed, turn on and test the agitator to ensure it is operating properly. Direction is critical to avoid product degradation if digestate is pushed towards the motor/outside.

6. Filling the Digester: Once the new agitator is tested and working properly, fill the digester with the appropriate contents.

7. Reactivate the digester: Activate the digester and monitor the agitator operation to ensure it is working as expected.

It is important to follow proper safety procedures when replacing a submerged agitator in a digester. Be sure to wear the correct personal protective equipment and follow the manufacturer's instructions to ensure safe installation and use of the agitator.