Rock Box Protects Headworks at Kansas City, Missouri Blue River Wastewater Treatment Plant
Kansas City Missouri Water Services Department operates the 105 mgd Big Blue River Wastewater Treatment Plant (WWTP) serving combined and separate sanitary sewers on both sides of the Missouri River in Kansas City. Heavy grit inundation from the Combined Sewer System (CSS) was impacting the screen house and aerated grit/pre-aeration basins at this facility. Alternatives were considered for removing grit larger than ¼-inch in diameter upstream of the screen house. Alternatives included swirl concentrators, aerated grit removal, vortex grit removal and continuous deflective separators. Another alternative was developed by CTE called a Rock Box which allows the grit slurry traveling along the bottom of the sewer to drop through an opening on the floor of the influent box sewer into a chamber below the sewer. A fillet of concrete allows the falling grit slurry to slide to one side of the sewer where the grit settles in a storage compartment to be removed by clamshell to roll-off containers for transport to a landfill. Removing this CSS grit protects the screen house and grit chambers from inundation with heavy grit loading. Upgrades were also provided to replace the existing aerated grit chambers with vortex grit removal systems to handle the grit remaining after the Rock Box. In one week’s time, the Rock Box removed 16 tons of grit while the vortex grit removal system removed another 10 tons of grit. Now that the screen house is protected from CSS grit loading, the City is in a position to replace the damaged bar screens.