Plant for the treatment of car wash waters composed of a primary grit removal  moonoblock unit in  rotomoulded linear high density PE, oil removal unit in  rotomoulded linear high density PE equipped with coalescence separator of non-emulsified oils and hydrocarbons , biofiltration unit in  rotomoulded linear high density PE equipped with membrane diffusers and a filter bed of plastic material, a lifting water well in rotomoulded  linear high density PE, a sand/antracit and activated carbon filters, a a fiscal water well in rotomoulded linear high density PE. All units are equipped with inspection threaded manhole  and  IN / OUT PVC connections suitably sized and variable diameter complete with NBR gaskets.