Doctor of Philosophy (PhD)
Civil and Environmental Engineering
The research objective was the optimization of light dynamics in a Hydraulically Integrated Serial Turbidostat Algal Reactor (HISTAR). A deterministic model of HISTAR productivity that was responsive to manipulations of photosynthetic photon flux fluence rate (PPFFR) was developed, calibrated, and applied. A series of experiments was conducted to define the mathematical equations that best describe three relationships. The first relationship was between the elevation (E) of the light source and the culture surface PPFFR (Io). The second relationship was between the biomass concentration (X) in the experimental unit and the average PPFFR in the reactor (Ia). The final relationship was between average PPFFR and the net specific growth rate (U). Parameters for these three relationships varied for light sources having different spectra. The light source specific parameters investigated were the light attenuation coefficient (kaw), maximum specific growth rate (μmax) and optimum average PPFFR (Iopt). These parameters were estimated experimentally (using Selenastrum capricornutum as the surrogate microalgal species) for metal halide, high-pressure-sodium (HPS), fluorescent, and Son Agro® lights. Using the experimentally estimated parameters for metal halide and the three experimentally defined relationships, a HISTAR productivity model was developed using the Stella® modeling platform and calibrated using actual HISTAR data. Biorhythms were discovered in the residuals during a calibration attempt. These harmonics were modeled and incorporated into the productivity model before completing calibration. The HISTAR productivity model was then used to simulate the effects of light source type, system dilution rate (Ds), number of CFSTRs, wattage, lamp elevations, and culture depth on daily productivity in HISTAR. It was concluded from simulation studies that using HPS lamps, a Ds of 0.641 d-1, changing lamp elevations to 25.4 cm, and changing culture depth in the last four CFSTRs of HISTAR would be cost beneficial. The production lighting cost (LC, based on $0.10 killowatthour-1) may be reduced from $48 (kg dry wt)-1 to $36 (kg dry wt)-1. Decreasing the number of CFSTRs in HISTAR or increasing lamp wattage was not predicted to be cost effective. The outcome of this type of research for other species adapted to different habitats would probably differ.
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Benson, Barbara Christine, "Optimization of the light dynamics in the Hydraulically Integrated Serial Turbidostat Algal Reactor (HISTAR)" (2003). LSU Doctoral Dissertations. 3708.
Kelly A. Rusch