The Des Moines Wastewater Reclamation Association might be the only organization in town not looking for attention.

For the past few years, the WRA has been working on a roughly $6 million project to reduce odor emissions around the Des Moines Regional Wastewater Reclamation Facility, which handles 97 million gallons a day and serves most of Greater Des Moines. Its goal is to reduce emissions by about 90 percent, lowering the offsite area affected by odors from approximately 944 acres to 10.

“We want to be as environmentally transparent as possible,” said William Stowe, director of the WRA and Des Moines’ Public Works, “or as economically feasible. … We know the Southeast Side is a continually improving area of the city and we don’t want to be an objectionable neighbor.”

The effort was in large part inspired by several projects planned for the area, including the 1,100-acre Agrimergent Technology Park, the extension of Martin Luther King Jr. Parkway into a southeast connector to downtown and the extension of the Des Moines River Trail system past the plant.

Although the project is not required, Stowe said it should help make the Southeast Side a more attractive place for future development and will increase land values of development already nearby.

The WRA hired HDR Inc., an Omaha-based architectural and engineering consulting company, to conduct the study of odor emissions, which was completed in early 2005. Construction on the project began last year. The first phase will be completed by the end of this summer and is expected to achieve most, if not all, of WRA’s goals to reduce odor emissions.

The study took air samples from potentially odorous sources and used air dispersion modeling to quantify emissions from the sources and predict the impact of those odors outside the facilities boundaries. This information was then used to determine which areas needed the most attention.

The study won this year’s Grand Conceptor award, the overall first-place award, from the Iowa chapter of the American Council of Engineering Companies. It also won the grand place award in the special projects category.

Although the study might not be new for the United States, Brian Bakke, project manager at HDR’s Des Moines office, said it is progressive in the Midwest.

“Not only did we evaluate where we thought the odors were coming from, but by doing modeling and sampling, we were able to assign a value to each odor source and were able to prioritize the list of improvements needed,” he said. “So we were not using any sort of educated guess.”

Bakke said that odor control is something a lot of U.S. wastewater treatment plants are looking into, especially existing plants in high-density population areas. Around Des Moines, Stowe said, several suburbs have been concerned about building a facility on the outskirts of the community and then having the community grow up to it, as happened in Des Moines.

But Stowe added that it is more common for wastewater treatment plants to address odor emissions by building a dome over their facility, rather than using biofilters, the method WRA chose, because biofilters posed less of a risk for employees and the facility could expand more easily.

“Ultimately it’s probably a more expensive solution, but provides us the greatest flexibility to expand it,” he said.

After the study, WRA has worked with HDR to implement its suggestions in four phases, which Stowe said will primarily reduce emission of hydrogen sulfide, which produces a “rotten egg” smell.

The first phase is focused on controlling odor emissions from hauled waste, the belt filter press and preliminary treatment sources. Two sets of organic media biofilters are being constructed, which will route odors through a large fiberglass duct and force them through organic media of woodchips and compost. The bacteria in the media will oxidize and treat the odorous compounds, Bakke said.

The first phase is about 70 percent of the entire plan and is estimated to cost around $3 to 4 million to construct and $66,000 to operate and maintain per year.

The second phase, expected to begin in 2008, will control emissions related to the digester roof and pressure relief valves, which is part of a previously planned and budgeted digester mixing and gas holdings improvement project.

The third phase will control emissions from residuals processing, grit conveying, pump discharge and solids processing sources. At this stage, the two biofilter sets constructed in the first phase will be converted from organic to inorganic media, which is more expensive, but can handle a greater capacity. This phase will cost around $3.6 million to construct and $78,000 per year to operate and maintain.

Phase four will address any need to further control offsite odor levels and will further reduce onsite odor levels by controlling emission from the primary clarifiers. The two sets of seven total biofilters constructed in the first phase will be expanded to 10 biofilters. The cost would be around $10 million to construct and $98,000 per year to operate and maintain.

Stowe said the WRF will seasonally monitor odor emissions, but he is confident that the first phase will handle most of the objectionable smells. Phases two, three and four will only be implemented as needed, which will likely depend on future development in the area.