Gina Riggio, a doctoral student in the cell and molecular biology program at the University of Arkansas, won first place in the student poster competition during a national water conference earlier this month.

Riggio studies hydroponic leafy green production and microbial food safety, with the guidance of her adviser Kristen Gibson, associate professor in the Department of Food Science. Her poster was titled "Treating One Waste Stream with Another: Spent Grow Mats as a Carbon Source for Denitrification of Hydroponic Wastewater."

Hydroponic producers often grow crops on mats, basically fibrous organic substrate from corn or other materials. Once the crop is harvested, the grow mat is typically thrown away. However, Riggio is looking at how producers could use those grow mats to improve nitrogen removal from the wastewater stream in the operation.

The water must be treated to remove nutrients before flushing it down the drain, otherwise it will put a big stress on the centralized wastewater treatment plants. Bacteria are great at removing nitrogen by the denitrification process, but they need a carbon source, which can be expensive. Riggio's work is showing that spent grow mats can provide a valuable carbon source so the bacteria can remove most of the nitrogen in the wastewater.

This project was funded through the Arkansas Water Resources Center 104B grant program. "It would be difficult to get funding for this project otherwise," Riggio said about the importance of this grant, adding that this seed grant will allow her to generate data to get more funding in the future.

"I did a lot of networking," Riggio said about the value of the UCOWR/NIWR annual water conference. "People were excited about this research, and I met a few potential collaborators for future projects," she added.

Riggio will use her graduate research knowledge directly in her future career, where she and three others own a microgreen and hydroponic lettuce indoor farm in Huntingdon, Pennsylvania, called GreenSpace.