Aerobic biological wastewater treatment reactor in which the bacterial purifying biomass is placed on an inert support, forming a biofilm (fixed bed). Wastewater is uniformly distributed on the surface and flow downwards with the gravity, through the pores of the filter. Thus, bacteria can degrade the carbon pollution and a part of the nitrogen one. The natural air ventilation carries to the bacteria, all the oxygen they need to eliminate the pollution.
Natural purification process, which consists in passing the water through basins, slowly enough to let submersed plants achieving their purification role, before releasing the water in the nature. Indeed, the aquatic vegetation hosts some bacterial communities able to remove pollutants such as nitrates, phosphates...