Estimating and Controlling Odors in Collection Systems/Tunnels With Vortex Drop Shafts

Abstract

The Western Regional Conveyance Tunnel Project (WRTP) is planned for construction in Western Boone County, Kentucky. The collection system upstream of the WRTP is under development, and flows from that system must be conveyed to the new Western Regional Treatment Plant. Northern Kentucky Sanitation District No. 1 (SD 1) is designing the WRTP for the conveyance and wet weather storage of flow to the treatment plant. The tunnel will consist of a 100-foot-long drop shaft (drop shaft no. 1) at the entrance to the tunnel, a 6.8-mile-long, 9.5-foot-diameter storage/conveyance tunnel, a flow control gate structure, followed by a 0.7-mile-long, 8.5-footdiameter storage/conveyance tunnel to the treatment plant. Odor must be controlled to prevent unacceptable levels of odorous emissions generated by and emitted from wastewater in the drop shaft and tunnel that could affect citizens in the surrounding community. Estimates of hydrogen sulfide (H 2 S) generation in the collection system upstream of drop shaft no. 1, emissions from drop shaft no. 1, and generation and emissions in the tunnel were estimated using sampling data, a computer model that predicts the generation, transport, and fate of H 2 S in wastewater collection systems, drop shaft air flow estimates using model developed equations, and a mass transfer spreadsheet model. The emissions estimates were used to optimize the selection and locations of the odor control technologies. KEYWORDSOdor, dropshaft, vortex, tunnel METHODOLOGYThe goal of the tunnel system odor control conceptual design was to estimate the concentration of odors in the tunnel headspace and air exiting the drop shaft. To do this, the following steps were followed:1. Estimate sulfides generated in the collection system upstream of the tunnel. 2. Estimate sulfide emissions from the drop shaft no. 1 (tunnel inlet). 3. Estimate sulfides generated and emitted in the tunnel. 4. Use the results of steps 1 through 3 to select and optimize the location and type of odor control technologies. 4664WEFTEC®.07