AP-800 DIR Reverse Osmosis Unit. This professional series reverse osmosis unit the ARO-400G is a complete water treatment system with lacquered metal support frame, ready for installation.Discards from the incoming water all types of contaminants and pollutants (chlorine, organic residues, pesticides, inorganic pollutants, minerals & salts, microorganisms, etc.) Product water is crystal clear water, suitable for use in every workplace, such as restaurants, taverns, cafes, bars, hotels, etc.