Date of Award:

5-1-2014

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Advisor/Chair:

David K. Stevens

Abstract

Significant phosphorus transport is occurring in the groundwater surrounding Pineview Reservoir. A set of investigations was completed to identify factors contributing to phosphorus mobility. Water quality monitoring was conducted to understand groundwater characteristics and phosphorus movement. Several water quality parameters were evaluated to specifically determine whether septic systems influence groundwater quality. Results indicate that septic systems pollute at least two locations in the aquifer around the reservoir. Given this information, it may be necessary to implement advanced septic system treatment options to reduce the amount of phosphorus in groundwater. Experiments were conducted on two aquifer sediment types to identify factors important for phosphorus mobility. Coarse-grained sand and fine-grained sediments were evaluated, and results showed that phosphorus in both sediments is associated more with calcium minerals than with iron and aluminum minerals. Results suggest calcium is an important factor for immobilizing phosphorus in groundwater at Pineview Reservoir. Iron and manganese oxide concentrations are important for decreasing phosphorus mobility, and experiments showed higher amounts were observed in fine-grained sediments than for coarse-grained sediments. Results of geochemical modeling exercises suggested that sediments may have limited sorption capacity, although at one site, the formation of calcium minerals may provide a continuous source of additional sorption material. Because of suspected septic system influence, the effect of dissolved organic matter on phosphorus mobility was evaluated through a series of laboratory studies. Dissolved organic matter was collected from Pineview Reservoir and used in experiments. Results showed that the presence of dissolved organic matter affected phosphorus sorption minimally, and does not explain P mobility in the shallow unconfined aquifer at Pineview Reservoir.

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