The Advent Water Treatment Process employs two sequential stages of granular media to accomplish flocculation, clarification and filtration. Raw water is dosed with appropriate treatment chemicals, and after mixing, is introduced to the first (upflow) media contactor through a distribution system consisting of an array of closely spaced nozzles. Velocities in the underdrain plenum are limited to facilitate sedimentation of settleable solids, however, a properly designed intake screen required to protect the distribution system from lightweight and floatable materials. The Advent Water Treatment Process is a very high-rate approach to water treatment which has been successfully applied to a wide range of water and wastewater categories. Rational application criteria and chemical treatment recommendations based on the results of both pilot and full-scale operations, are now available for plant designers and owners.