Date of Graduation

5-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Environmental Dynamics (PhD)

Degree Level

Graduate

Department

Graduate School

Advisor

Wen Zhang

Committee Member

Stephen Boss

Second Committee Member

Thad Scott

Third Committee Member

Thomas Costello

Keywords

Applied sciences; Earth sciences; Algae; Biofuels; Lipids; Microbiology; Wastewater; Water treatment

Abstract

In order to move towards a more sustainable future, human civilization will need to decrease its impacts on air and water quality and minimize consumption of fossil fuels. Using algae for wastewater treatment and biofuel production offers one approach to progress towards these goals simultaneously. Algae are capable of removing nutrients from wastewater and carbon dioxide from the air, and the biomass formed in that process can be used to generate a wide-range of products including fertilizer or fuels that could power combustion engines, power plants, or zero-emission fuel cell vehicles. Using wastewater for biofuel production has the potential to lower biofuel costs and environmental impacts as it provides an existing, free source of nutrients and water. Growing algae during the wastewater treatment process further improves the effluent quality, thus helping prevent eutrophication and costly dead zones in downstream ecosystems.

Maximizing the benefits of algal wastewater treatment and biofuel production will require optimizing total nutrient removal, biomass production, and lipid content of the biomass; a complicated problem given that many algal species known for high nutrient removal and lipid production are easily suspended single-celled microalgae that are difficult to harvest efficiently by gravity. In wastewater treatment, growing pure cultures of single-species algae is not practical, so positive and negative impacts of growing algae in the presence of endogenous microbial communities should be evaluated.

This dissertation seeks to move algal wastewater treatment forward by improving our understanding of the roles of species composition and nutrient availability on nutrient removal, lipid and biomass production, and settling; and by assessing alternative methods used to quantify algal productivity in order to improve future research. In comparison with traditional quantification methods, alternative methods investigated provided reliable results for a range of algal species and concentrations, with significantly less sample volume, reagents and processing time. For the nutrient and species experiments, Chlorella vulgaris was grown in real and synthetic wastewater and in combination with other algal species and endogenous wastewater microbial communities. Multiple synergistic effects were observed from mixing species with implications that could improve both secondary and tertiary treatment of wastewater while providing biofuel feedstocks.

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