Last year, the Minnesota Technical Assistance program helped companies realize more than $3 million in energy savings

Laura Fletcher: Efficient Waste

by judy woodward

Both her MnTAP mentor, Karl DeWahl, and her supervisor at Wastewater Board Services, Brad Gehring, agree that Laura Fletcher was academically prepared for the tricky job of calculating the optimal air flow for the giant blowers that provide oxygen for the decomposition process at St. Paul’s Metro Wastewater Treatment Plant.

The plant treats 185 million gallons of wastewater daily and the aeration process accounts for more than half of the plant’s daily electricity usage—a cost of approximately $450,000 per month. If Fletcher were able to calculate the most efficient way to utilize the giant blowers, the cost savings could be substantial.

DeWahl, who describes his support role as steering a middle course “between letting interns learn, yet keeping them from falling into the abyss,” characterized Fletcher as “fairly advanced,” even considering her status as a recent Institute of Technology graduate. As such, she neatly fit the bill in terms of what he looks for in intern applicants. “We look at school record, ability to perform independently and some evidence—even a hobby—that shows an interest in how things work, as well as an ability to go beyond theory,” DeWahl said.

Fletcher was adept at bringing a theoretical understanding to her project, but she may have been even more pleased by some of the practical knowledge she acquired during the course of the summer.

“The project was so different from class work,” she said, explaining that lab exercises—however well-designed—invariably have a predetermined, ‘right’ answer. “When you intern, you know that no one has tackled this project before.”


As a summer intern through the MnTAP program, Laura Fletcher (ChemE ’08) worked on optimizing the energy use of this blower for St. Paul’s Metro Wastewater Treatment Plant. The blowers provide oxygen for the decomposition process.

Not that she denies the value of her academic coursework in tackling her particular project. “I had taken a chemical engineering senior lab that helped me look at data and figure things out without always knowing what I was doing at the start,” she said. By luck, one of her laboratory problems gave her precisely the right preparation for her project. “I had a lab on blowers and air flow meters,” Fletcher said. “It was a small scale version of what I did as an intern.”

Fletcher also gives credit to DeWahl. “He’s another resource. He’s had years of experience; he had ideas when I wasn’t able to see what to do next,” she said. Thanks to her mastery of the relevant calculations, Fletcher was ultimately able to suggest reconfigurations of the blowers that would save the plant upwards of $60,000 in annual electricity costs.

“Laura is very bright and fresh out of school, so she was comfortable with the theoretical framework of the project. The blower efficiency equation is very complex, and some of our own staff had steered clear of it, but she dug right in,” Gehring said.