Compact water filtration device

A water treatment device comprising, on a pipe for water to be treated, an upstream membrane barometric clarification stage and a downstream advanced barometric purification stage, said downstream stage comprising an overpressure means upstream of a filtration means of the downstream stage, said filtration means of the downstream stage comprising a retentate outlet, the water treatment device also comprising a washing circuit for using water clarified by the water treatment device and accumulated in a tank to perform washing of said upstream membrane stage periodically, and the water treatment device being wherein it also comprises a command for controlling switching between an operating mode for producing filtered water comprising applying suction created by said overpressure means to a permeate outlet of the upstream stage and applying circulation to said retentate outlet in a pipe having a reinjection point on said pipe for water to be treated, on the one hand, and a periodic maintenance mode comprising circulating water toward the upstream stage from said tank that is placed downstream of a permeate outlet of said filtration means of the downstream stage, by said washing circuit, said washing circuit having an injection point on said pipe for water to be treated, said injection point of the washing circuit interfacing with the upstream of the overpressure means, and the reinjection point interfacing with the downstream of the overpressure means, on the other hand.