As is common here we have a fosse septic. Loo works as normal the fosse contains lots of little digesting bacteria, eventually the poo is broken down to a nice layer of sediment, the clean water (filtered by a reed bed and sand) returns to the stream. Until recently once in forever, a local farmer would pump out the sediment for shoving on his fields. Now though it has to be pumpled out every 4 years regardless of how little is in the tank, and the sediment treated before being shoved on the fields. Still have to use clean drinkable water to flush the loo though.