dissolved air flotation systems used for water treatment in the industrial, municipal, and the pulp and paper fields, consisting primarily of flocculation basins and mixers, flotation basins, mechanical scrapers for surface sludge, dispersion water pumps, pressure tanks, air compressors, dispersion water chambers, pipings and valves between the basins, mixers, pumps, chambers, and tanks, and electrical controllers therefor, sold as a unit