Bypass Pumping and the Sulfide Challenge - Solutions for Remedying the Unique Safety, Odor and Corrosion Challenges Faced in Temporary Bypass Pumping Projects Due to Hydrogen Sulfide

Our linear infrastructure requires regular maintenance, refurbishment, upgrades, and sometimes. replacement, for it to continue to effectively serve our communities. In order to properly care for this aging infrastructure, sewage bypass projects are frequently a critical component of many of these linear infrastructure projects. Temporary bypass systems is the typical solution to transfer water and sewage flow and maintain uninterrupted service during the necessary bypass of the existing infrastructure. The unfortunate side effect of this type of bypass project is frequently an increased release of hydrogen sulfide and other sewer gasses. These gases can cause a nuisance for the surrounding community via increased odor release. Also important, these gases can cause corrosion to concrete, metals and electrical components not intended to be exposed to sewer gases, potentially shortening the useful life of critical infrastructure. Most critically, however, Hydrogen Sulfide and other sewer gases are frequently found at concentrations toxic to human health, frequently reaching fatal concentrations in sewer systems. Open access points in sewer network, plus additional turbulence at the downstream discharge point all contribute to increased exposure to the environment of the gases that would otherwise be contained within the sewer system. Sulfide control at bypass pumping has traditionally involved a fan and undersized activated carbon canister that requires frequent replacement. There are a range of better suited solutions that can be implemented to effectively manage the sewer gas releases challenge. This paper will discuss the challenges of designing and implementing a sewage bypass pumping service and the merits of implementing effective sulfide control measures for any bypass operation including the use of liquid phase chemical treatment and foul air scrubbing technologies. The available technologies will be reviewed, and examples of best practice application will be discussed. There is no single perfect solution for sewer bypass sulfide control, and the appropriate technology combination is often project specific. The vapor phase technologies suitable for bypass pumping most commonly include appropriately sized activated carbon systems and packaged biofiltration technologies. Other vapor phase technologies such as chemical scrubbing may not be suitable due to the complexity of operation and project site requirements but may suit some specific bypass pumping sulfide challenges. In addition, either instead of or supplemental to the vapor phase technologies, a range of liquid phase technologies can be utilized to reduce the release of the sulfides into the gas phase, thereby improving the work environment for those involved in the upgrade project and making the management of sulfide gas release less challenging. These liquid phase technologies include sulfide capture, alternative biological oxygen sources, fast acting oxidants and pH adjustment technologies. The reader will learn that a comprehensive sulfide control strategy allows for the effective mitigation of hazardous, odorous and corrosive sewer gasses, minimizing the impact to our communities during maintenance or capital improvement activities both at the project site and at downstream discharge points.