What’s That Smell? Investigating Wastewater Odors
If you are reading this article, chances are you’re experiencing odor issues within a municipal wastewater collection system and/or treatment plant. Investigating these offensive odors ensures that you are being a good neighbor, providing a safe work environment, and protecting critical infrastructure from corrosion caused by hydrogen sulfide. The sooner odor issues are addressed, the more cost-effective and impactful the solutions can be.
A comprehensive odor control strategy begins with an odor investigation to characterize the odor and identify the source. This article provides a high-level overview of a typical odor investigation approach. Key components include:
Odor Complaint Logging
Odor Characterization and Source Identification
Odor Control Objectives
Odor Complaint Logging
Wastewater system operators routinely log operational and maintenance data daily to improve operational efficiencies and/or to identify areas within the system that require maintenance improvements. Typically, this data is recorded within the system’s GIS database; however, some agencies still maintain hard-copy daily logs. Either way, a key data point that should always be documented is customer odor complaints. While offensive odors are a nuisance to the public, they also may be an indicator that a more serious issue is happening beneath the surface, e.g., an occupational health and safety work hazard and/or accelerated corrosion of critical infrastructure.
Odor complaint logs provide the first piece of the puzzle that assists odor control specialists in identifying the source(s), implementing appropriate data collection activity, and ultimately determining an appropriate control strategy. At a minimum, odor complaint logs should compile the following information: location of the complaint, time of day odor detected, weather conditions, frequency and duration of occurrence, and description and intensity of smell.
Odor Characterization and Source Identification
Odor characterization involves collecting field data and, in some cases, wastewater and foul air samples for laboratory analysis to pinpoint the offensive odor source. Evaluation methods include:
Liquid Sampling: Wastewater dissolved sulfide, pH, ORP, temperature, BOD
Continuous Air Monitoring: Hydrogen sulfide, differential pressure
Field Olfactometry (Odor Sampling)
Computer Modeling: Sulfide generation, sewer ventilation, air dispersion
The graphic on the left depicts continuous monitoring data for differential pressure at various locations within a wastewater collection system, while the graphic on the right depicts continuous monitoring data for hydrogen sulfide concentration at the same locations. Recording continuous monitoring data during an odor investigation helps to identify the appropriate odor control strategy.
You can read more about odor characterization, specifically how odor is defined and measured here. A core principle amongst engineers and scientists – if you can measure it, you can manage it, which certainly applies to odor and odor control in wastewater collection systems.
Odor Control Objectives
A comprehensive odor control strategy includes establishing control points and treatment objectives. Odors are inherently part of wastewater collection and treatment; however, proactive action is imperative if odor investigations indicate a frequently occurring issue and/or evidence of infrastructure corrosion. Identifying odor control points and clear treatment objectives will drive cost-effective decisions for odor control strategies and manage stakeholder expectations. Typical objectives for an odor control strategy include any or a combination of the following: odor complaint mitigation vs. hydrogen sulfide induced corrosion mitigation, minimal customer complaints, safe work environments, and long-term wastewater asset service life.
Stay tuned for an upcoming blog article that outlines proven and implementable odor control solutions.
And as always, if you have any questions regarding odor characterization studies or odor control solutions, please reach out to one of our technical specialists. Our team of experts can provide guidance on investigating foul odors, analyzing the issue, and developing control solutions.
Click here for more about our Odor Control Services.