Gravity Filtration
Precast WW Underdrain
The Roberts’ concrete Precast Wastewater Underdrain is designed to be a structurally sound and robust tertiary filter underdrain system. The Precast Wastewater Underdrain is designed to easily support the deep bed dual and mono-media filter media configurations commonly specified by consulting engineers for tertiary filtration and denitrification applications.
The underdrain provides a very low mal-distribution of wash water with almost no associated headloss. When operated in conjunction with the air distribution system, even the deepest media beds are maintained in their optimum condition. As designed, the air distribution system is located underneath the concrete WW blocks, thereby protecting the air system from damage.
With their generous opening size, flow through the underdrain is maximized while the potential for clogging is almost completely eliminated. Through separate openings integral to the structure of the Precast Wastewater Block, air is uniformly distributed into the gravel support and sand for maximum cleansing and to assure extended run-times during filtration.
Under normal operation, this engineered system is able to remove over 80% of TSS plus provide a degree of phosphorus removal. Additionally, the underdrain system remains extremely stable, even when the filters are subjected to CSO and storm events.
Technical Details:
Material: Class I Concrete, maximum aggregate size = 3/8” (.95cm)
Air Flow Rate: Design Rate = 6 scfm/sq. ft. (109 m³/hr/m²)
Water Flow Rate: Design Rate = 6 gpm/sq. ft. (14.6 m³/hr/m²)