MWRD Odor Control Strategy

The Metropolitan Water Reclamation District of Greater Chicago (District) was created in 1889 as the Sanitary District of Chicago by state statue to protect the drinking water of Chicago. While the overall goal has remained intact, the agency has grown to serve 125 additional municipalities encompassing 91% of Cook County, with an effective population of 10.35 million people, and an annual budget of $1.2 billion dollars. The District owns and operates 7 wastewater treatment plants, 22 pumping stations, and 560 miles of intercepting sewers.The primary responsibility of the District is transforming the regions wastewater into a resource, and odor is an unfortunate bi-product of this process. Over the years the District has taken a distributed approach to addressing odors through monitoring, improving standard operating procedures, and implementing capital improvements. A distributed approach to odor control can lead to gaps in coverage and addressing unpleasant odors becomes increasingly difficult to manage. To improve this aspect of our operation, the District has made addressing odor a high priority and changed its approach from the top down. In 2015, the District’s Board of Commissioners released its updated Strategic Business Plan where developing targeted odor control strategies is explicitly identified, and the Executive Director centralized the coordination of Odor Mitigation Strategy in the Monitoring and Research Department.Once top down direction was provided, the District was able to develop an overall odor control strategy framework around that direction to systematically address odors at its wastewater treatment plants, solids processing facilities, and collection system. Highly odorous areas, or “hot spots” were quickly cataloged and prioritized by odor intensity, effect on surrounding communities and plant personnel, and cost and ease of odor control implementation.The current process to address Hots Spots are through an evaluation project team coordinated thought the M&R Planning Section. The project team includes relevant personnel from the Maintenance and Operations (M&O) and Monitoring and Research (M&R) Departments. Larger projects that require significant design will also include team members from the Engineering Department. The evaluation process includes developing a long list of options, refining it to a short list, and then performing a modified triple bottom line matrix comparison to assist with selecting the best path forward. Options considered include vapor and liquid phase treatment, operational adjustments, and optimizing any existing odor control equipment. This long list is refined to a short list of about three or four options with preliminary review and initial calculations. To avoid biases, the final evaluation matrix is developed after the establishment of the long list and prior to the creations of a short list. The final evaluation matrix is used for the modified triple bottom line that includes major categories of economic, technological, and social/environmental categories, with each category given equal weight. These major categories are broken down into subcategories with weighting that are project specific. The matrix serves as the primary tool for identifying the path forward to address the odor. Smaller project are vetted by an interdepartmental panel and larger project are presented to the Executive team. This final step in the process guarantees that all odor control projects are in line with the goals of the District.After significant odor generators are identified and addressed, the program will evolve from an immediate need “triage” model that is effective in addressing point sources, to a more comprehensive program that will utilize more advanced tools to address the area sources. A real-time odor monitoring system is currently being installed at the District’s Calumet Water Reclamation Plant with plans for its expansion to other treatment plants, solids processing facilities, and collection system based on its performance. Currently we anticipate to have a plan for the point sources developed within the next three years and a comprehensive understanding of the area sources by 2022.