Performance Comparison of Three Photobioreactor Systems Differing in Scale, Geometry, and Operating Conditions for Landfill Leachate Treatment Using Red Algae: Nutrient Removal and Biomass Growth

The algae-based landfill leachate (LL) treatment system has been proved promising for nutrient recycling and biomass production at lab- or small-scale photobioreactors (PBRs). However, many assessment tools such as techno-economic analyses (TEAs) usually utilize parameters from small-scale experiments as input data to predict the potential performance of commercial large-scale or full-scale bioreactors. Reliability of using data from lab-scale for commercial large-scale estimation is still uncertain. This study compared the performance of three photobioreactor systems that differed simultaneously in scale, geometry, light intensity, mixing mode, and aeration: 0.125 L small-scale flask, 1 L medium-scale tubular PBR, and 15 L wall-shaped PBR for real LL treatment. The 1 L medium-scale tubular photobioreactor outperformed the other two systems in biomass growth rate and the rates of nitrogen and phosphorus removal, even though all three systems removed nearly all NH4-N and PO4-P (≈100%) within two weeks. Possible reasons for this better performance include stronger illumination, a bubbling aeration mode, the reactor shape (which improves mixing), and higher surface area to volume ratio × light intensity. According to these results, using relatively small-scale flask experimental data for predictive analysis of industrial-scale algal systems could be inadequate. In this study, volumetric optical radiation (VOR) serves as a promising preliminary descriptive indicator to reflect the overall performance of an algal-based treatment system.