The NCSD collection system has high levels of hydrogen sulfide and odors in areas near large force main discharges and larger pump station locations. The sulfide levels can be hazardous, and the resulting odors are a nuisance for adjacent property owners. This requires an effective plan to reasonably manage. The District currently utilizes a combination of chemical injections into the wastewater stream, carbon filters, or biological filter technologies at five (5) pump station locations. This combination of solutions is currently provided through two (2) different vendors. Chemical injections (calcium nitrate) began in 2007 followed by filters in the later years at certain urban pump stations. NCSD would like to confirm best practices and seek recommendations for the most cost-effective solutions at the desired locations. The last odor study was conducted in 2006 and is attached for review. Please note only a few locations were analyzed in the last study and was focused on reducing corrosion on downstream infrastructure. This study shall consider corrosion along with employee and public safety.The selected engineer will be required to evaluate the existing pump station configurations, measure odor levels, research odor and corrosion mitigation methods, and recommend the most cost-effective odor control technologies for the system. It is expected that multiple technologies may be recommended as a comprehensive approach. Detailed site-specific design is not required as a part of this study. NCSD does not anticipate constructing inground biological filter solutions as space and staffing requirements are both limited. It is not the intent to have the selected engineer perform a detailed corrosion analysis on existing equipment at each pump station site but rather to provide system recommendations for maintaining odor and H2S levels within acceptable limits at each location. The selected engineer will be required to meet with Engineering, Operations, and Maintenance staff to discuss operational considerations, staff requirements, system preferences, prioritization of the project scope, and to coordinate the engineering study and recommendation requirements. It is expected that the engineer will coordinate with third party solution vendors to evaluate existing technologies to be able to provide the most appropriate solutions.
