Date of Award:

12-2011

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biological Engineering

Committee Chair(s)

Ronald Sims

Committee

Ronald Sims

Committee

Byard Wood

Committee

Issa Hamud

Abstract

Research being completed at the Logan, UT wastewater treatment plant could provide a locally-sourced gasoline replacement by collecting algae that grows naturally. This process would also provide the City of Logan with a method to meet certain standards set by the state of Utah.

Problem and proposed solution:

The water leaving Logan’s wastewater treatment plant has high levels of phosphorus and nitrogen, two elements that are found in all wastewater treatment plants. These two substances need to be controlled, because they kill fish and cause pond scum to grow in recreational reservoirs downstream. A unique method has been found to remove these elements.

The wastewater treatment plant is a lagoons design, consisting of a series of large, open-air ponds. Algae naturally grow in these ponds, and consume the phosphorus and nitrogen found inside. If the algae can be harvested from the ponds, the phosphorus and nitrogen can be removed as well. As an added benefit, the algae can be used to create a gasoline replacement, known as biodiesel.

Current research:

One research project completed at the Logan wastewater treatment plant was the optimization of a method to harvest this algae. Andrew Elder worked with a device called a Dissolved Air Flotation, or DAF, unit. This machine uses microscopic bubbles to lift the algae to the surface of the water, where it can be easily removed. (Removing the algae removes much of the phosphorus). The phosphorus not in the algae cells is removed by the small amount of chemical additives required for the DAF process to work.

The goal of this research project was to determine the optimum amount of chemicals required for proper algae harvesting. Additionally, there is a possibility that chemicals naturally secreted by the algae could help eliminate some additional chemical addition.

Two different methods were used to determine the proper chemical addition. First, a large DAF unit was used to determine the proper chemical dose. Next, a miniature DAF unit was used to study different chemical doses at different times of day. There is evidence that different amounts of sunlight could increase the quantity of these natural chemicals being produced.

Results:

The optimum amount of chemicals needed was determined to be 30 mg of aluminum sulfate per liter. The naturally-produced chemicals were found to have no significant effect on algae harvesting, at any time of day.

Conclusion:

This project demonstrated the ability for a DAF system to successfully harvest algae from the Logan wastewater treatment plant, with only minimal chemical addition. Along with meeting state of Utah requirements, this process could allow the Logan wastewater treatment plant to collect enough algae to create a significant amount of a locally-based, sustainable automobile fuel. Enough algae could be grown to fuel all of the City trucks with biodiesel. This process would save the City money and be beneficial to the environment at the same time.

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Comments

This work made publicly available electronically on November 22, 2011.

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