Effects of operational parameters on the performance of unialgal Oedogonium sp. filamentous algae nutrient scrubbers under controlled environmental conditions

Filamentous algae nutrient scrubber (FANS) operating parameters can strongly influence algal biomass pro-ductivity and nutrient removal. However, few studies to date have investigated the effects of FANS operating parameters such as initial standing crop, harvesting frequency and influent flow rate on biomass productivity and nutrient removal performance, especially for FANS that cultivate a single species of algae. Therefore, the overall aim of this study was to investigate how operating parameters affect the biomass productivity and nutrient removal performance of Oedogonium sp. -a promising species for unialgal FANS. The initial standing crop had a significant effect on biomass productivity, with productivities being highest (8.6 +/- 0.5 g DW biomass m- 2day- 1) when the initial standing crop was 60-70 g DW m- 2. However, the daily nutrient removal rate was highest (0.47 +/- 0.06 g N m- 2 day-1and 1.24 +/- 0.13 g P m- 2 day- 1) at the highest initial standing crop (100-110 DW m- 2). Biomass productivity was highest with a three-day growth period, regardless of size of the initial standing crop. Therefore, a four-day harvesting interval was selected as the optimal harvesting regime to promote exponential growth and high biomass production. Influent flow rate had a significant effect on biomass productivity, which was highest (9.3 +/- 1.7 g DW m- 2 day- 1) for the 1 L min-1 flow rate. This flow rate also gave the highest instantaneous nutrient removal rate (0.05 +/- 0.02 g N m- 3 and 0.14 +/- 0.05 g P m- 3). Current results suggest that an optimum initial standing crop of 70-80 g DW m- 2, harvesting frequency of four days and influent flow rate of 1 L min-1 (16.7 L min-1 m- 1 width) were optimal for Oedogonium sp. cultivated on FANS to maximize their biomass production and nutrient removal under controlled laboratory conditions. These results contribute to understanding the impacts of operating parameters on optimizing unialgal Oedogonium sp. FANS biomass pro-duction and nutrient removal performance.