Publication Date

2016

Document Type

Dissertation/Thesis

First Advisor

Holbrook, Gabriel P.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences

LCSH

Microalgae; Waste products as fuel; Renewable energy sources

Abstract

The purpose of this thesis was to investigate the growth of the green microalga Monoraphidium sp. Dek19 in the context of phycoremediation under conditions representative of wastewater media of a Midwest wastewater treatment facility. Microalgae were grown in effluent collected from four different wastewater streams at the DeKalb Sanitary District (DSD), DeKalb, Illinois, USA in volumes from 1 L to 380 L. It was determined through preliminary modeling of public data that Monoraphidium sp. Dek19 will likely outcompete local heterospecifics in final effluent wastewaters at the DSD 51.8% of the year. It was also determined that neither nitrogen nor phosphorus should become a limiting nutrient throughout the year. Study of the response of Monoraphidium sp. Dek19 to salinity stress was also completed. Salt stress caused a significant increase in lipid accumulation in salt stressed cultures compared to control cultures (37.0-50.5% increase) with a reduction in biomass productivity. Increases in photosynthetic pigments per cell were seen under salt stress, though the ratio of chlorophyll a and b remained constant. Finally, nitrate uptake was not greatly affected by salinity stress except when biomass accumulation became a corollary for uptake (nitrogen saturation). Luxury uptake of phosphate was significantly affected by wastewater salinity (p<0.001). High sodium potentially interrupts phosphate stress response proteins, slowing internalization of phosphate. Phosphate removal was still possible as some protein binding proteins appear to operate independent of sodium. The effect of indole-3-acetic acid on regulation of cell division in Monoraphidium sp. Dek19 was evaluated at a range of concentrations and no significant differences were observed. A comparison of Monoraphidium sp. Dek19 growth in activated sludge, post-primary filtration, and two final wastewater streams revealed a minimum effect of biotic stressors. The microalgae also grew readily in all wastewaters, though initial population density demands are likely different for each effluent type. Monoraphidium sp. Dek19 grown at large scale revealed light availability as more important than other factors even when compared to large temperature changes (10-25°C). Low-light growth tanks (380 L) showed significantly reduced specific growth rate though microalgae population tripled after three weeks. Dried algal tissue from 380 L tanks was extracted and used to determine neutral lipid accumulation at 6.64+/-0.08%. Fatty acid content was analyzed by GC-FID and found high amounts of unsaturated 18 carbon chains (18:2-18:4), more than previously shown. A comparison of oil from cells growing in 380 L and 1 L cultures showed culturing condition affected fatty acid profile. It was concluded from these data that Monoraphidium sp. Dek19 could be a useful phycoremediation tool of municipal wastewater in the upper Midwest.

Comments

Advisors: Gabriel P. Holbrook.||Committee members: Neil Blackstone; W. Scott Grayburn.||Includes bibliographical references.||Includes illustrations.

Extent

ix, 125 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

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Text

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