Award Date

December 2023

Degree Type

Thesis

Degree Name

Master of Science in Engineering (MSE)

Department

Civil and Environmental Engineering and Construction

First Committee Member

Jacimaria Batista

Second Committee Member

Erica Marti

Third Committee Member

David James

Fourth Committee Member

Spencer Steinberg

Number of Pages

212

Abstract

The Environmental Protection Agency recognizes urban runoff as a major contributor of surface water pollution with nutrients as the second largest cause of surface water impairment in the United States. While a water quality standard of 100 lbs/day total phosphorus load allocation for all nonpoint sources is permitted for the Las Vegas Valley (LVV) under the National Pollutant Discharge Elimination System, currently there is not a counterpart standard for nitrogen. With the continued development of the LVV and the depletion of the quantity of water in Lake Mead due to the ongoing drought, the concentrations of phosphorus and nitrogen species within Lake Mead are expected to increase. As such, future revisions to regulations may call for the treatment of stormwater and urban runoff in order to reduce nitrogen and phosphorus pollutant loads. Therefore, there exists a need to explore treatment technologies for the removal of theses nutrients from LVV urban runoff. Furthermore, as urban runoff volumes can be quite large, it is important to explore technologies that are passive and do not require pumping or mixing. The objective of this research was to investigate the removal of nitrate (NO3), ammonia (NH3), and phosphate (PO4) from a synthetic stormwater solution using zero-valent iron (ZVI) and zeolite. The effectiveness of nitrate reduction and phosphate precipitation by ZVI, and the removal of ammonia by zeolite via ion-exchange was evaluated in this study. Continuous flow, laboratory-scale column experiments were the selected methodology with four different column designs featuring layered or mixed media configurations. The removal of NO3 was influenced less by the amount of ZVI used in the columns and more by the hydraulic retention time (HRT), with NO3 removal of 54-97% observed for an average HRT of at least 7 hours. The removal of NH3 depended less on HRT and more on the amount of zeolite used in the columns with >80% ammonia removal observed when the amount of zeolite used was increased by 6-7 times. High phosphate removals ranging between 80-100% were consistently observed regardless of HRT or amount of ZVI used. Overall, layered media configurations within the columns achieved higher percent ranges in nutrient removal, with ZVI layered above zeolite ensuring that the ammonia produced by the reduction of nitrate by ZVI in the top layer was then captured in the zeolite bottom layer for removal by ion exchange. All in all, a dual media zeolite and ZVI passive treatment system for the removal of nutrients from urban runoff is feasible and partial removal of ammonia and nitrate with near complete removal of phosphate is expected.

Keywords

nutrients; passive treatment; urban runoff; zeolite; zero-valent iron

Disciplines

Civil Engineering | Environmental Engineering | Water Resource Management

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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