The liquid waste refining station of the International Market of ARKEZE, which has three lagoon basins with microphytes, faces important development problems. Those problems include the low production of liquid waste, the plugging of the main water pipe - which usually results in olfactory nuisances, the frequent breaking of the pipes that drain the liquid waste to the station, the lack of maintenance of the station - which causes a high rate of mud in the anaerobic basin. This investigation aims at studding the hydraulic functioning and assessing the different basins. To that purpose, quality indication measures have been carried out for ten weeks on samples, some of which have been taken daily and others weekly. The liquid waste