from the English sub-title it appears they are installing a septic tank. This is where sewerage from a household goes into a special holding tank on the property, rather than being connected to the main sewerage line where the waste flows into large treatment plants run by the local council or government authority. The 'cylindrical concrete blocks' are called concrete rings. At least that is what I would call them, I don't know if they have some other official name.

A septic tank is a way of dealing with sewerage (waste from the toilet). It lets the waste break down into a form that is less toxic to humans. Instead of "cylindrical concrete block" I would say "concrete ring". A block would not have a hole in the middle.