Lessons Learned from Using Vortex Flow Insert for H₂S Sewer Corrosion and Odour Prevention

Release of unpleasant odor to the environment is an easily identified consequence of H₂S production in sewer systems; therefore, air-locking the entrance to municipal wastewater collection networks (e.g., manholes) should reduce the emissions of H₂S gas into the air. However, this will increase the H₂S gas resident time, which unfortunately results in aggravating sewer corrosion. Controlling or eliminating H₂S generation within existing sewage collection systems is the best approach. Two ways to achieve this are by altering the sewer ambient environment and modifying the system’s hydraulic design parameters (e.g., by reducing turbulence). These two options are said to be possible with the Vortex Flow Insert (VFI) system. VFI works by using the drop flow energy of the wastewater to create a vortex that then reduces turbulence potential, typical with plunge drops. The spiral flow is claimed to help create a downdraft into the unit, trapping airborne gases and forcing air into the sewage flow to oxidize odorous gases. After a series of consultation iterations, a large water utility company in western Canada installed VFI in one of its major drop manholes. The 8 m deep drop manhole in question is part of a 1950 trunk sewer system connected to a 600 mm connecting sewer that transfers the 2.6 m drop flow into the drop manhole. Being the first ever VFI in utility’s system, a post-installation experimental study was completed to evaluate the effectiveness of the VFI in reducing odor and corrosion potential in the system. This presentation describes the H₂S generation mechanism, the science behind VFI, design details of the VFI, VFI installation considerations, on-site performance data collection program, data analysis and interpretation of findings, and lessons learned and recommendations for future implementations.