Engineering students grow edible plants, fish, in aquaponics system

People who live in developing countries sometimes don’t grow their food the old fashioned way.  Instead, their food comes donated in a great big fish tank–an aquaponics system where the fish feed the plants, and the humans harvest fruit, veggies, and fish.

A group of UTC engineering students in a senior interdisciplinary design class successfully built a small scale freshwater automated aquaponics system with an innovative automated water changing system;  instrumentation installed to measure nitrates, nitrites, ammonia, and pH balance; a pumping system; a swirl and sand filter to remove solid waste from the tank; and several different methods of growing plants.  Mechanical, industrial, and electrical engineering students were all part of this team.

“I love everything about this project!” exclaimed Christy Rigsby, mechanical engineering major who will graduate in May and the student project manager for the group.  “This method takes one-eighth of the water normal farming does to be successful.”

The system features three aquaponic raft vegetation racks.  A sump pump delivers nutrients into the vegetation bed feed line.  Plants in a basket are partially submerged while the upper part of the basket rests above the water line.  Duckweed, a secondary food source for the fish, is grown in a bin fed with waste water after it’s been run through a filter.   A media bed uses an ebb and flow technique–water is pumped from the sump tank, until a bell siphon is activated.  Then the bed drains rapidly back into the sump tank.

While the swirl and sand filter separates solids, the breakdown of the solids helps nourish the plants.  As the project continues, the hope is when the solids are captured, they can be dried in a small field and later sold for fertilizer.

Ultimately, the goal of this ongoing project is to feed planted vegetation solely with the fish waste products. Tilapia, chosen because it could be densely packed in the 125-gallon tank, have grown from a quarter of an inch in September to six inches.  The rapidly growing plants have yielded bell peppers, Jalapenos, Swiss chard, lettuce, and tomatoes for students to taste.  This smaller tank offers some intriguing possibilities for growing edible plants in a home or office setting.

Rigsby has enjoyed working on the system so much she changed her focus in mechanical engineering from energy to machine, because she enjoys studying flow rates.  She has been an intern with Tuftco and plans to pursue a master’s degree.  As project manager in her UTC design class, Rigsby organized and delegated. Students Andrew Boring, Dennis Doyle, Anthony Escandon, Jackson McKissick, and Michael Jambon also worked with Rigsby.

“I like to be in charge,” she said with confidence.

She says she’s learned a lot in engineering classes she described as “just the right size” with professors who are approachable.

“We learn a lot more at UTC because we aren’t afraid to ask questions,” she explained.  “We really are a big, happy family.”  Rigsby recently married her husband Garrett, a UTC computer science major.  Rigsby is also the daughter of two UTC computer science alumni, dad James Coleman ’84 and mom Rebecca Coleman, ’89.

Anthony Escandon, who served as the student lead mechanical engineer for this project, was responsible for fluid flow analysis, sizing of plumbing and valves, writing code for virtual instrumentation, and data collection.  The class was taught by Dr. Trevor Elliott and Dr. Ed McMahon.  Elliot said Escandon’s interest in the project was obvious–he basically lived in the lab.

“Our professors at UTC gave us a broad idea of what we could do for our project.  They let us take the initiative, so they let us take the project where we wanted it to go.  If we had not had that freedom, it wouldn’t have been as fun or turned out as well,” Escandon explained.

Escandon graduated from UTC in December.  He will begin work in spring 2015 at Florida Institute of Technology engineering master’s program, where he has earned a partial scholarship.

He’s has come a long way from his days in high school, when his family moved several times.  He dropped out of school in 11^th grade, got his GED, and then returned to his California roots.  It took him several years to find his way to his family’s Tennessee construction company, where he worked for several years. In 2009, he enrolled at Chattanooga State where he spent three years, and then transferred to UTC to study mechanical engineering.

“The classes were harder than they were at Chattanooga State,” Escandon explained.  “I decided I would also go to school during the summer, and over time, I gained more and more confidence.  The professors here are great,” he said.

Now 30 years old, Escandon looks forward to studying in Florida.  His research interests focus on offshore renewable energy, specifically ocean thermal energy conversion.  The temperature differential between surface and deep water can be used to generate electricity, a new field of technology.

“It’s always been in the back of my mind to delve into ocean engineering,” Escandon said. “When I was younger and lived I California, my family had a drive to get to the beach.  It’s always been someplace special to me.”