Date of Award:

5-2012

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biological Engineering

Committee Chair(s)

Ronald C. Sims

Committee

Ronald C. Sims

Committee

Issa Hamud

Committee

Judith Sims

Committee

Hassan Arafat

Abstract

The City of Logan Environmental Department has a goal to remove chemicals from the municipal wastewater that can cause algae growth in Cutler Reservoir that will impair use for recreation. The proposed plan to accomplish the goal is to grow algae within the 460-acre Logan Lagoon wastewater system, and then remove the algae from the treated wastewater that enters Cutler Reservoir. The collected algae may be used to produce biodiesel to fuel the City solid waste vehicles. The City will coordinate the development and implementation of this project with the assistance of the Utah State University Biological Engineering Department. The technology of cross flow filtration was proposed as a chemical-free form of algae harvesting and was evaluated for this project.

Experiments were conducted with laboratory-scale and pilot scale cross flow systems. Filtration membranes constructed of polyester and nylon with pore sizes of 1-micron and 5-micron were used at various engineering operating conditions to determine the optimal conditions for the laboratory system.

Results demonstrated that cross flow filtration was a suitable option for the algal harvesting without adding additional chemicals that may interfere with the production of biodiesel. The polyester membrane collected a larger mass of algae compared with the nylon membrane, and a small pore size of 1-micron retained more algae compared with the 5-micron pore size.

Cross flow filtration was demonstrated to be an effective method for harvesting algae from the Logan Lagoon wastewater, with a cost of approximately $2 million dollars. Although biodiesel fuel was not generated from the harvest algae, the predicted price of the algal biodiesel per gallon ranged from $7.17 to $7.18 in the first year. The benefits of cross flow filtration for algae harvesting are discussed in the thesis, and the results can be used by City of Logan, Utah engineers to compare cross flow filtration with other engineering technologies for the separation and harvesting of algae from treated wastewater.

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This work made publicly available electronically on April 10, 2012.

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