RAPID CITY, S.D. - Research conducted by a trio of School of Mines students may help the city save more than $151,000 at its Water Reclamation Facility.
In their novel approach to figuring out how to combat elevated concentrations of nitrogen compounds, Mines seniors Marshall Davis, Kyle Doerr and John Ostheimer discovered the city's wastewater is being over aerated and that the practice could be significantly reduced, potentially saving up to 61 percent of that operating cost, as well as fossil fuel emissions, and still be within environmental guidelines.
A certain amount of aeration is necessary to remove high levels of nitrogen compounds because they present serious problems and challenges to ecosystems, including low dissolved oxygen, fish kills, murky water and depletion of desirable flora and fauna.
But aeration is an expensive and energy-consuming process with an environmental impact. While Bob Druckrey, environmental process supervisor for the city, said the exact amount of savings potential is "dependent upon additional study," students cited $151,513 over a five-year period in their final report.
The students' approach provides the opportunity to control aeration in the nitrification cell upon reaching a predetermined ammonia concentration.
Druckrey, a School of Mines alumnus, described the students' method as novel. "Usually when you control an aeration process you measure the dissolved oxygen concentration. The thing the students did was measure the amount of ammonia in the water as an indication of where we could reduce the oxygen feed." When ammonia has been completely converted to nitrate the need for additional aeration is greatly reduced.
"I heard about this approach at the annual Water Environment Federation Technical Exhibition and Conference in New Orleans last fall and put it on my list of interesting things to look at," Druckrey said.
The environmental engineering majors designed a procedure in which they sampled and measured the amount of nitrogen ammonia every 10 feet of the activated sludge aeration basin. They traveled to the Rapid City Water Reclamation Facility weekly to take samples and measurements.
Student findings showed aeration occurring at levels "well over the need for ammonia removal. They're over aerating at the moment so they can reduce," Lew Christopher, Ph.D., civil and environmental engineering department associate professor, faculty advisor and instructor of the undergraduate laboratory research course, ENVE 498.
"Currently the blowers are operating at full operation capacity throughout the entire basin. However, the information gathered from this study proves this practice unnecessary and suggests that the aeration rate be reduced to provide only mixing past the nitrification stage," according to the report.
While reducing aeration may seemingly require a simple turn of the valve, Druckrey points out "you need to know which valves to turn down, when to turn them down, and at what parts of the process. The next step will be to purchase process instrumentation to give us a better handle on the data the students collected and then go from there."
Druckrey said he suspected aeration levels were higher than they needed to be "but we didn't have anything in hand to indicate it. When they came back with their results I was surprised and then some."
Christopher approached city officials looking for "real-life" experience for his students, and this study was among several Druckrey and his colleagues suggested. "I called them and proposed that we work together on something practical for our hands-on lab. This was a very beneficial exercise. They were very happy and we were very happy with the results," Christopher said.
Because this course appears beneficial to both SDSM&T and the Water Reclamation Facility the collaboration will continue in the spring 2014 semester.
Students delivered a poster presentation on their work at the 2013 Undergraduate Research Symposium and orally presented their findings to Druckrey and his colleagues.