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Microalgae cultivation has gained considerable interest recently as a potential source for the production of biofuels. Nevertheless, many obstacles still face the industrial application of microalgal biofuels such as the high production costs due to nutrient requirements and the high energy input for cultivating and harvesting the microalgal biomass. In this study, the utilization of the anaerobic digestate as a nutrient medium for the cultivation of two microalgal species was investigated. The anaerobic digestate was initially characterized and several pretreatment methods such as hydrogen peroxide treatment, filtration using polyester filter bags, and supernatant extraction were applied to the digestate. It was found that the supernatant extraction was the simplest and most effective method in decreasing the turbidity and COD of the diluted anaerobic digestate while maintaining sufficient nutrients (particularly nitrogen) for microalgae cultivation. The microalga Neochloris oleoabundans was cultivated using the diluted anaerobic digestate supernatant on a bench-scale. It was found that 100 mg N/L dilution was sufficient to maximize the biomass concentration of this microalga. It was attempted to scale up the cultivation of the microalga N. oleoabundans to 100 L raceway ponds; however, the culture was contaminated with other algal species.The microalga Scenedesmus dimorphus was then cultivated using the anaerobic digestate supernatant on a bench-scale. The highest biomass concentration recorded was 654 mg/L. Furthermore, it was found that 50 – 100 mg N/L dilutions were sufficient to maximize the specific growth rate of this microalga while still producing relatively high biomass concentrations. As a result, the microalgae cultivation was scaled up to 100 L raceway ponds using 100 mg N/L dilution at 454 and 317 µmol/m2/s light intensities and 50 mg N/L dilution at 384 and 234 µmol/m2/s light intensities. The highest biomass concentration achieved was 432 mg/L in the 100 mg N/L – 454 µmol/m2/s culture. Nitrogen removal efficiencies were in the 65 – 72% range with complete ammonia removal. Phosphorus removal efficiencies were in the 63 – 100% range while COD removal efficiencies as a result of the bacteria presence in the unsterilized nutrient media were in the 78 – 82% range.The effect of mixing on the growth of the microalga S. dimorphus was evaluated by cultivating this microalga in a raceway pond at 0.1, 0.2, and 0.3 m/s water surface velocities. It was concluded that the biomass concentration and growth rate increased with an increase in the mixing velocity. However, by balancing the power required to operate the pond at different velocities with the potential energy yield from biodiesel synthesis, it was found that operating the pond at 0.1 m/s surface velocity was the only case with a positive net energy. Finally, two biomass growth models were developed and tested on the growth of the microalga S. dimorphus. It was found that the logistic model, which assumes a maximum bearing capacity of the culture, represented the biomass growth better than the exponential growth model, which assumes that the microalgae grow exponentially at specific growth rates equal to or less than the maximum specific growth rate dependingon the culture conditions.

Highway storm water runoff contributes to the degradation of surface water quality in the United States. The most important pollutant in highway runoff is the total suspended solids (TSS). The United States Environmental Protection Agency (U.S.EPA) requires the runoff to be treated before it is conveyed to surface water. The exfiltration trench is one of the best management practices (BMP's) utilized by the Ohio Department of Transportation (ODOT) to treat highway runoff in-situ and consists of three layers: pervious concrete, type 3 backfill material (aggregate) and type 2 backfill material (sand). In this study, the exfiltration trench located on SR7, OH, is evaluated based on the pollutants' removal efficiency, particularly, TSS. TSS was removed at an efficiency of 41% in the originally constructed trench while the reconstructed trench achieved 69% TSS removal. Other water quality parameters investigated in this study include particle size analysis, turbidity and pH which were performed on both influent (highway runoff) and effluent (treated influent) samples.