Here in the rural western U.S., almost everyone is on a septic tank-leach field type of sanitary disposal.
Ours empties from the house into a concrete tank (underground) that's about 8 feet long, 5 feet wide and maybe 5 feet deep... it has a set of "dams" inside to help solids to fall to the bottom... the rest of the fluids eventually flows to the far end where it empties into a leach field ... a system of 4 inch perforated PVC pipes that are buried in individual trenches about 6 feet deep. The trench is filled with maybe a goot of gravel/sand, the perforated PVC placed on top of that , 'red rosin' paper on that and filled with gravel and finally a layer of soil.
The tank itself needs to be pumped out about once every two to three years since the sediment in the bottom will eventually build up. The bacteria is supposed to destroy the sludge in the bottom, but and only do that to a certain degree. We have pumping truck service that comes out to us and the neighbors on schedule and charges $125 (US) to each.
Apologies for the extensive description, but wanted to let you have a comparison to your system there...