3D-printed custom substratum to accentuate fast functional responses from microbial colonization

Abstract

Recent studies have shown the feasibility of growing benthic organisms on customized substratum by using Additive Manufacturing (AM). Their proven capabilities to fabricate objects at high speed and with complex geometries according to a pre-defined digital design makes the scope of AM to include environmental applications, such as the design of surface topographies for phototrophic biofilm production (Kardel et al., 2015). This dissertation is part of a cross-disciplinary research effort to investigate the interaction between customized surfaces, algal communities and microbial biofilms in general. The first goal is to investigate the effect of different interstitial surface area distribution on the early colonization of benthic algal biomass in a laboratory-based Algal Turf Scrubber (ATS). 3D printed plates with 4 different surface types were elaborated with extruded Polylactic Acid using Fused Deposition Modelling (FDM) and a Makerbot printer with 0.1 mm layer thickness. Plates with randomized sections were deployed inside an Algal Turf Scrubber under laboratory conditions for 7 days. Treatments having 3 different interstitial surface distributions called pockets were compared to a flat surface and tested for their biomass density by freeze-dried weight. Results determined that interstitial pockets provided larger initial algal densities than substratum lacking them, and suggested that an optimal value of pocket distribution exists for maximum colonization. Moving Bed Biofilm Reactors (MBBR) can have a high performance by having suspended carriers that are free to move in the wastewater to be treated while providing a surface for attachment of active micro-organisms. The second goal of this work assessed the design, fabrication and functional testing of 3-D biofilter media carriers for use in Moving Bed Biofilm Reactor (MBBR) technology for wastewater treatment. Specific surface area and topology of the biofilter media carrier are among the most important parameters that determine the performance and efficiency of the system. Mathematical models and 3D printing were used to design and fabricate media with three different levels of complexity that provided large specific surface area and refugia to protect biofilm from sloughing. Results not only confirmed the capability to 3D-print gyroid shaped biocarriers with a large surface area, but also demonstrated their functionality for removing ammonia from the prepared synthetic wastewater at rates that were directly related to the specific surface area of the carrier. The results suggest new approaches for design of carriers with high surface area that can increase performance in reactor technologies for wastewater treatment.