Date of Award

Summer 8-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Civil & Environmental Engineering

Program/Concentration

Environmental Engineering

Committee Director

Gary Scharfran

Committee Member

Charles Bott

Committee Member

Mujde Erten-Unal

Abstract

Conventional operation of wastewater treatment plants (WWTPs) is to maintain a dissolved oxygen (DO) concentration at or above 2.0 mg/L in the aeration process for biological nutrient removal (BNR). However, the adoption of operating at low DO in WWTP aeration systems has led to the improvement of process efficiency and reduced aeration energy requirements, making the transition to low DO favorable. Furthermore, as systems transition to oxygen-limiting conditions, the accuracy in DO measurements becomes increasingly important. Many plants use DO sensors to regularly control aeration processes, but their precision and accuracy at (ultra) low DO concentrations are less established. If a system lacks certainty in a DO measurement, both process optimization and BNR performance can become hindered.

The research in this study evaluated various methods to validate low and ultra-low DO measurements for a BNR system. Pilot-scale and full-scale studies were conducted to assess phosphorus and nitrogen removal performance under these limiting DO conditions. Additionally, pilot-scale tests were conducted to evaluate DO sensor performance, compare sensor measurement methods, and determine practical approaches to verify DO concentrations under controlled conditions. Multiple methods were examined and applied over a range of operation conditions representative of wastewater treatment processes.

The results from this work demonstrated that effective phosphorus removal can be achieved at DO concentrations significantly below conventional operating targets. PAO Ko values were observed at DO concentrations below 0.13 mg/L in batch tests. Additionally, significant differences in DO sensor performance were observed among measurement technologies, specifically within the ultra-low DO range (< 0.2 mg/L). Optical sensors generally displayed improved accuracy, precision, and stability compared to electrochemical sensors, with the PyroScience TROXROB10 optical sensor providing the most reliable measurements.

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DOI

10.25777/dfg9-ed63

ISBN

9798193214670

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