Document Type

Thesis - University Access Only

Award Date

2011

Degree Name

Master of Science (MS)

Department / School

Civil and Environmental Engineering

Abstract

The purpose of this study was to evaluate strategies and technologies for the City of Sioux Falls Wastewater Reclamation Facility (SFWRF) to achieve denitrification in the existing wastewater treatment plant. A lab-scale reactor along with BioWin® modeling was used to evaluate the feasibility of operating on-off aeration in the existing activated sludge system to achieve denitrification. The lab-scale reactor was evaluated by data collected from six complete test runs over a duration of 11 months. A model created in BioWin®3.0 was used to evaluate on-off aeration at the full-scale plant. Detailed waste characterization was performed using existing data as well as laboratory measurements to calibrate and validate the model. The most effective time scenario tested in the lab-scale reactor was 2 hours on aeration and 2 hours off. The addition of a carbon source was necessary to drive the denitrification and an MLSS concentration of 1,500 mg/L or greater was found to be most effective. The concentration of ammonia plus nitrogen reached a low of 8.5 mg/L as N during the test with conditions of 2 hours on, 2 hours off with the addition of acetic acid. The overall reduction in the ammonia plus nitrate concentration during this test was 61 percent. The alkalinity decreased during the on cycles and increased during the off cycles for all the lab-scale test runs. The increase in alkalinity during denitrification and consumption of alkalinity during nitrification was a buffer in the system causing the pH to remain near neutral. The mixing of primary clarifier effluent with activated sludge influent resulted in an overall ammonia plus nitrate reduction of 59 percent. The Bio Win® model results predicted that complete denitrification would not be achieved in the full-scale system without the addition of organic substrate. Two hours on aeration and two hours off proved to be the most effective time scenario at achieving nitrification and denitrification at 20Q C in the BioWin® model. Cold temperature simulations were run at 1OQ C. The most effective cold temperature simulation run that achieved nitrogen removal was when all process trains were operated at 3 hours on and 1 hour off. The results of the Bio Win® simulations indicated that the operation of on off aeration would likely have to be adjusted through the year with changing wastewater temperatures. Both the laboratory scale reactor results and the BioWin® results proved that on-off aeration could effectively remove nitrogen in the Sioux Falls Water Reclamation Facility. The most effective time scenario during warm weather conditions was found to be two hours on aeration and two hours off in both the reactor and the computer model. The Bio Win® model found that more aeration was required to achieve nitrification during cold temperatures. The time scenario of 3 hours on, I hour off was found to be most effective in cold temperatures with the BioWin® model. The lab-scale reactor and the Bio Win® model found that additional organic substrate would be necessary to successfully denitrify the wastewater in both warm and cold temperature conditions.

Library of Congress Subject Headings

Sewage disposal plants -- South Dakota -- Sioux Falls -- Management

Sewage -- Purification -- Nitrogen removal

Sewage -- Purification -- Activated sludge process

Sewage -- Purification -- Aeration

Denitrification

Format

application/pdf

Number of Pages

137

Publisher

South Dakota State University

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