The autonomous sanitation regime concerns housing located out of building areas to the plans of the sector, or in a few of these areas for which the sanitation plans per river sub-basin (PASH) decided it was better to purify the wastewater on an individual basis, that is, on the plot where the wastewater is produced, rather than collectively via a community treatment plant.
Nearly 12% of the population, which is to say nearly 160,000 dwellings, is located in autonomous sanitation. Among them, 2/3 lives in building areas to the plans of the sector.
Housing (and thereby the population who lives in it) located out of building areas to the plans of the sector, is de facto in autonomous sanitation. It means a little more than 4% of the population of the Walloon Region.