Custom Design of Substratum Topography Increases Biomass Yield in Algal Turf Scrubbers
Algal turf scrubbers (ATSs) have been used for water remediation in many applications, generating benefits such as water quality improvements and biomass production. Their economical operation is hampered, however, by uncontrolled mixed microbial communities, typical of open cultivation systems that result in lower biomass quality. Design of substratum topography is one approach to control the algal community composition by constraining colonization dynamics. This study seeks to elucidate the role of substratum topography on biomass productivity of benthic algae in an ATS environment. A set of tiles with custom-designed textures of repeated hemispheres across a range of diameters were 3D printed and cast on ceramic clay. An algal turf community dominated by Mougeotia taxa was cultivated on the tiles in a laboratory-scale ATS and harvested for biomass measurements after 21 days. Results show higher biomass on the topographies formed of 500 and 2,000 μm diameter hemispheres, with 74.3% more attached biomass than the 1,000 μm hemisphere and smooth topographies. With the surface area, material roughness at the microscale, and surface chemistry discarded as factors by experimental design, surface topography, especially interstitial space distribution, at the millimeter scale is shown to be a factor in the kinetics of algal cell colonization and growth on surfaces. This study is among the first that specifically focuses on the application of substratum design using additive manufacturing to improving the ATS process. These results can have a significant impact on design of next-generation high-productivity attached growth algae systems.