Plant for treating a polluted water, comprising: - a sealed filtration reactor, in which the polluted water to be treated circulates, said reactor being equipped, in use: o with membranes intended to be passed through by the polluted water in order to selectively separate the particles contained in the water to be treated, said membranes being detachably mounted in a support attached to the inside of the reactor, o with means (2, 20) for injecting gaseous ozone into the reactor, - an inlet pump arranged upstream of said reactor in order to transport the polluted water from an inlet circuit into said reactor, - an outlet pump arranged downstream of said reactor in order to discharge the purified water from the outlet of said membranes towards a discharge circuit, being characterized in that: - several cylindrical ceramic membranes suitable for operating at pressure are grouped together in first modules that are similar to caissons, - several flat ceramic membranes suitable for operating under vacuum are grouped together in second modules that are similar to caissons, - the first modules and the second modules are of identical shape, - the reactor alternately receives either the first modules, or the second modules depending on the initial characteristics of the water to be treated, - the support comprises housings suitable for alternately receiving, depending on the type of membranes used, and temporarily, either the first modules or the second modules, the same housings being used to receive and keep in place the first modules and the second modules, the inlet pump and outlet pump are connected to a control device suitable for varying their pumping rate so that the membranes (10a, 10b) operate at negative pressure or at positive pressure depending on the type of membranes used. - a sealed filtration reactor, in which the polluted water to be treated circulates, said reactor being equipped, in use: o with membranes intended to be passed through by the polluted water in order to selectively separate the particles contained in the water to be treated, said membranes being detachably mounted in a support attached to the inside of the reactor, o with means (2, 20) for injecting gaseous ozone into the reactor, o with membranes intended to be passed through by the polluted water in order to selectively separate the particles contained in the water to be treated, said membranes being detachably mounted in a support attached to the inside of the reactor, o with means (2, 20) for injecting gaseous ozone into the reactor, - an inlet pump arranged upstream of said reactor in order to transport the polluted water from an inlet circuit into said reactor, - an outlet pump arranged downstream of said reactor in order to discharge the purified water from the outlet of said membranes towards a discharge circuit, being characterized in that: - several cylindrical ceramic membranes suitable for operating at pressure are grouped together in first modules that are similar to caissons, - several flat ceramic membranes suitable for operating under vacuum are grouped together in second modules that are similar to caissons, - the first modules and the second modules are of identical shape, - the reactor alternately receives either the first modules, or the second modules depending on the initial characteristics of the water to be treated, - the support comprises housings suitable for alternately receiving, depending on the type of membranes used, and temporarily, either the first modules or the second modules, the same housings being used to receive and keep in place the first modules and the second modules, the inlet pump and outlet pump are connected to a control device suitable for varying their pumping rate so that the membranes (10a, 10b) operate at negative pressure or at positive pressure depending on the type of membranes used.