Sludge is remove by using T-shape spanner, so it would have no harmful effect of the person removing the sludge.
SF-50S
Structure
These are designes with plow blade(②) is installed inside the bowl(①), and has dualshafts ① and ② are rotated at once during common operation.
If hte sludge were accumulated too much on the wall, the plow blade can be used to scrap the sludge that will be collected by a waste cart at the bottom.