Award Date

December 2019

Degree Type


Degree Name

Master of Public Health (MPH)


Environmental and Occupational Health

First Committee Member

Shawn Gerstenberger

Second Committee Member

Steven Weber

Third Committee Member

Chris Machado

Fourth Committee Member

Guogen Shan

Fifth Committee Member

Nader Ghafoori

Number of Pages



An increasing number of treatment plants are required to remove nutrients from domestic wastewater to lessen the impact of nutrient loading to water bodies. Enhanced Biological Phosphorus Removal (EBPR) is one of the processes commonly used to remove phosphorus from domestic wastewater. The presence of an adequate quantity of volatile fatty acids (VFA) in the wastewater influent to EBPR is important for process efficiency and stability. The objective of this research was to investigate the production of VFAs through fermentation of sludge in primary clarifiers as it related to improving nutrient removal, primarily targeting phosphorus.

The research tested, in full-scale, the production of VFAs at different solids retention times measured by the depth of sludge blanket in primary clarifiers. Three ranges of sludge blanket depths (< 0.9 m, 0.9 m – 1.5 m, and > 1.5 m) were used to investigate the production of VFAs. Results showed that larger sludge blanket depths led to higher concentrations and greater productions of VFAs. The speciation of VFAs was also measured. As the sludge blanket depth increased from < 0.9 m to > 1.5 m, acetic acid and butanoic acid concentrations and productions increased, while propionic acid concentrations and productions had an inverse relationship with sludge blanket depth.

Overall, the results confirmed that operating primary clarifiers at higher sludge blanket depths can increase the VFA concentration. In addition, the results indicated that higher sludge blankets may reduce the propionic acid fraction of the total VFA matrix. These results as applied to the wastewater treatment plant where this study occurred, demonstrated that larger sludge blanket depths would not provide sufficient benefits to justify the operation at a higher sludge blanket depth due to the marginal increase in VFA/TP ratio and significant reduction in primary clarifier performance.


Enhanced Biological Phosphorus Removal; Nutrients; Sludge Blanket; Speciation


Environmental Engineering | Public Health | Water Resource Management

File Format


File Size

14.6 MB

Degree Grantor

University of Nevada, Las Vegas




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