Term of Award

Summer 2022

Degree Name

Master of Science, Civil Engineering

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Civil Engineering and Construction

Committee Chair

Francisco Cubas

Committee Member 1

George Fu

Committee Member 2

Asli Aslan

Abstract

The artificial nitrate addition by the Upper Occoquan Service Authority (UOSA)’s Water Reclamation Facility (WRF) to the Occoquan Reservoir during the warmer months has been proven to be an efficient way of maintaining the water quality of the reservoir. During the warmer months, the water body became thermally stratified, resulting in hypolimnetic anoxia and the subsequent release of undesired matters from the reduced sediments. At the end of the warmer months, the temperature began to decrease, and by the beginning of winter, oxygen became ubiquitous in water because of fall turnover. This condition remained stable until the following thermal stratification; hence it was assumed that the system was devoid of denitrification and lost the efficiency of nitrate depletion during that period. That is why the UOSA kept the WRF’s operation stopped during that longer period of the year. This research assumed that nitrate depletion occurred at a lower rate before the onset of thermal stratification and between thermal stratification and fall turnover. Those periods have been termed ‘Shoulder Months.’ This study aimed to justify the possibility of extending nitrate addition activities in the shoulder months. The rationale of this research was that the low rate of nitrate depletion in the Occoquan Reservoir in the presence of oxygen during shoulder months was due to the insufficient supply of nitrates into the sediments as nitrate had to transport deeper into the sediments to reach the anoxic layer. Lab results showed that oxygen depleted (DO12ºC, oxygen concentrations ranged between 0.2-6 mg/L, indicating high oxygen and nitrate demand before thermal stratification. Besides, higher nitrate depletion was associated with a higher DO depletion rate by a correlation factor of 0.81.

OCLC Number

1360434381

Research Data and Supplementary Material

No

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