The underground car wash system is used to treat water from manual or portal car washes and self-service tunnels that usually contain sand, sludge, various inert materials, biodegradable detergents, residues of drying and polishing products, hydrocarbons and traces of metals. The influent flow rate must never exceed the plant’s nameplate flow rate. These plants consist of a pre-treatment phase in which the separation, by gravity, of solids and oils takes place, and a biological treatment and filtration phase carried out in a third tank using an artificially aerated biofiltration process. The contribution of biodegradable pollutant load and dissolved oxygen provides the active biomass with the necessary substrate to grow by adhering to the surface of the filling bodies, which, in addition to being a good filter, constitute an optimal surface for the micro-organisms to take root. Once its life cycle is over, a part of the biomass detaches itself from the substrate and, together with any foam or suspended material, is conveyed to the final sedimentation. This prevents any suspended solids from flowing down the drain. MEA Water have the best car wash water treatment plant in UAE.