Freshman filtration systems balance purity, quantity.

Engineering solutions, says Prof. Kristen Jellison, need not always be expensive, high-tech, or even mysterious. Often, a simple, inexpensive material can solve a vexing problem.

Jellison, the P.C. Rossin Assistant Professor of Civil and Environmental Engineering, recently told the 24 students in her Engineering 5 class about villagers in Bangladesh who used sari cloth, a common fabric in South Asia, as an effective medium for filtering impurities out of drinking water.

Then she assigned the students to find materials readily available in their own environments and design their own innovative filters for water-filtration systems.

Dividing into five teams, the students took Jellison's instructions to heart. One team jammed a nerf ball into its water tube and swathed it with layers of cotton. Another used coffee filters and activated carbon. A third pulverized pieces of charcoal, but when the powdery medium caused the filter to clog, the students tried again, combining larger pieces of charcoal with pumice stone.

The fourth group prepared a more traditional medium of activated carbon and sand with a layer of cotton as a pre-filter on top, and the fifth visited a locker room to obtain dry-fit, a fabric used by athletes to soak up sweat. This they combined with small pieces of a cut-up sponge, thick wood shavings, and cork.

Engineering 5: Freshman Design Experience, a new course, is required of all engineering freshmen. It is designed to give students a look at all the engineering disciplines and allow them to do hands-on design projects. Half the freshmen take the course in the fall, half in the spring. Students complete two five-week sections in a semester, thus gaining exposure to two different engineering fields.

At the start of the semester, the students attend presentations by the professors teaching the sections, then indicate their two class preferences on a questionnaire. There is no guarantee they will be assigned either choice.

Twenty-four students were assigned to Jellison's class, which is called "Innovative Water Filtration," and most had little idea what to expect. The major in environmental engineering is a new offering, a one-year-old degree program in the department of civil and environmental engineering within the P.C. Rossin College of Engineering and Applied Science.

The students said they appreciated the chance to learn first-hand about a field that most knew little about.

"For me," said Colin Mistele, who has not yet decided whether to major in mechanical or civil engineering, "this class and the tour we took of the other engineering departments have been very helpful."

"I like the fact that we get a chance to explore different areas of engineering," said Sydney Moe, who plans to major in civil engineering with an emphasis on structures. "I enjoyed the presentations by the professors from each department, and I especially like being able to get my hands on a project and see results. That's exciting."

The students learned quickly that water filtration is a balance between purity and quantity, between a system's success at removing impurities and the rate at which it can do so. A system that removes 100 percent of impurities is worthless if it clogs, while a system that produces abundant amounts of water is useless if the water is undrinkable.

The water entering each filtration system - tap water tainted with fine clay powder - contained about 40 nephelometric turbidity units, or NTUs. The goal was to reduce that as close as possible to the drinkable level of less than 1 NTU, and to do so at a rate that would prevent the water in the filter tube from rising above a white "terminal" line, indicating clogging. Teams were required to check water inflow and outflow levels four times a day, and to collect and dump water and perform other filter maintenance.

Tim Matthews was a member of the team that switched from pulverized charcoal to larger pieces of charcoal with pumice, activated carbon, and gravel when the first medium caused clogging. His team reduced turbidity in its system to 2.3 NTUs.

"That's almost as good as drinking-water quality," said Matthews, who is considering a major in either chemical or civil engineering. "It makes you feel good knowing you can do this."

The teams will give presentations on their filtration systems in Jellison's class on Dec. 3. One team will be selected to give a presentation on its system to all 180 students in Engineering 5 on Dec. 9.

Jellison looks forward to teaching Innovative Water Filtration again.

"I was impressed with the students' level of enthusiasm," she said. "Some of the students were not sure what environmental engineering was, and for many of them, this class was not their first choice in Engineering 5.

"Next semester, I might rule out sand entirely and have the students use only nontraditional media. I might also add a biological component to the feed water, such as bacteria, and see how well the students do with that."