Physical Modeling Leads to Improved Performance of Vortex Grit Basin

The Robert W. Hite Treatment Facility in Denver, Colorado is owned and operated by Metro Wastewater Reclamation District. The facility has a total rate capacity of 832.7 ML/d (220 mgd) based on maximum month flows. Their North Complex was upgraded in 2012 and among other improvements included modifying the existing four (4) vortex grit basins and constructing two (2) additional vortex grit basins. Grit deposition in the primary clarifiers provided evidence that the vortex grit basins were not efficiently capturing grit. As a result, a physical model was developed during pre-design to test various improvements to increase the grit capture efficiency. The physical model provided recommended improvements that were implemented during construction. Grit testing was performed prior to the improvements to provide base line grit capture efficiency of the existing units. Finally, grit testing was performed after construction to document the grit capture efficiencies and determine if the improvements were effective.