Wastewater Remediation Using Algae Grown on a Substrate for Biomass and Biofuel Production

Abstract

Surging oil, feed and fertilizer costs have impacted farmers particularly hard. Farm-based, local sources of renewable energy could help reduce energy costs for farmers and help develop rural-based processing and manufacturing of biofuel to bolster rural economies. At the same time, nutrient contamination and eutrophication from farming operations have become national problems. Algal-based bioprocessors have the potential to address these problems simultaneously. At Appalachian State University (Appstate) we set out to design, build and test a system that uses algae to capture wastewater nutrients as well as excreted pharmaceuticals, while simultaneously sequestering CO 2 , producing oil for conversion to biodiesel and feed for livestock. There are a number of problems with current algae growth systems. Algae grown in an open pond or raceway system are suspended in the water in the presence of soluble and suspended waste making most of the current harvest techniques problematic and expensive. Appstate designed algae troughs in which the algae are immobilized on a solid substrate. The laboratory-scale prototype was constructed of three-sided square plastic pipe open at the top. Inside the pipe, there was a series of cloth filters supported by rigid flow-through baffles. Preliminary results observed an average percent reduction of nitrate and phosphorous of 40 and 43, respectively, from different initial nutrient concentrations. Near complete removal (~96%) of estrogen was observed in 2-day trial experiments. In addition, effective increases in algal biomass which can serve as both biofuel feedstock and livestock feed were observed.