As part of operating and maintaining the City's wastewater system, Public Works catalogs and responds to foul odor complaints from the public. When a foul odor complaint is determined to be coming from the wastewater system, staff respond with standard maintenance practices such as adding passive air filters to sewer vents and sealing manhole lids. Over time, Public Works has identified three common areas of odor complaints in the City’s wastewater system and is proposing to conduct an odor study to identify any discernable causes and potential active solutions to these odors. Typically, wastewater odor is caused by the development of hydrogen sulfide (H2S) concentrations in wastewater pipes and manholes. This gas has an irritating sulfur-like odor, is corrosive to the City’s infrastructure, and poses a potential safety hazard for Public Works staff when entering wastewater manholes.
Public Works staff propose to retain Hazen and Sawyer, P.C. in the amount of $162,910 to conduct a wastewater system odor study. Hazen and Sawyer was deemed most qualified based on their Statement of Qualifications submission for RFQ No. 2023-0525-XR. The City’s wastewater system works in close operation with the North Texas Municipal Water District (NTMWD) wastewater system. NTMWD has previously retained Hazen and Sawyer, P.C. to conduct similar work in their system, which will allow the consultant opportunity for synergy, familiarity, and the ability to coordinate well between organizations.
The scope of this study includes establishing target areas, conducting field sampling, data analysis, identification of solutions, and a technical memorandum. Causes for odor may include chemical composition of wastewater effluent, wastewater age, turbulence in the flow, and/or undersized infrastructure. Solutions may include mechanical improvements (piping), chemical dosing, and/or specialized vent equipment.
If this project is not awarded, the areas of the City with wastewater odors will not be thoroughly studied for new solutions. City staff will continue investigating odor complaints and making field adjustments to reduce the amount of wastewater odor leaving the system and affecting residents.