Date of Defense
7-4-2026 5:00 PM
Location
Online - Microsoft Teams
Document Type
Thesis Defense
Degree Name
Master of Science in Civil Engineering (MSCE)
College
College of Engineering
Department
Civil and Environmental Engineering
First Advisor
Mohamed Hamouda
Keywords
Wastewater Treatment, Greenhouse gas emissions, Partial Nitritation, Anammox, Carbon footprint, SUMO
Abstract
Municipal wastewater treatment plants are significant contributors to energy consumption and greenhouse gas emissions, particularly during secondary treatment processes. The high carbon footprint of wastewater treatment plants can be primarily attributed to two factors: direct greenhouse gas emissions (Scope 1) and energy consumption (Scope 2). Nitrous oxide released during secondary treatment has a global warming potential 273 times greater than that of carbon dioxide. Moreover, conventional nitrification/denitrification wastewater treatment plants are energy-intensive and associated with greenhouse gas emissions, yet widely implemented for their ease of operation and maintenance. This highlights the need to evaluate alternative treatment configurations that reduce energy use and greenhouse gas emissions without compromising nitrogen removal performance. In line with this, this study investigates the impact of integrating a two-stage partial nitritation/anammox system as a side-stream process in a wastewater treatment plant to evaluate its potential to reduce its carbon footprint. Simulation enables the evaluation of strategies to optimize the operating conditions of the partial nitritation reactor and to determine the maximum feed required to support the growth of anammox bacteria in the anammox reactor. The partial nitritation reactor setup is a critical component of this research, as its development affects the success or failure of implementing the benefits of anammox bacteria, both in terms of greenhouse gas emission and energy consumption. While previous studies have investigated optimal operating conditions for partial nitritation reactors, they have generally not accounted for the associated carbon footprint. This study therefore focuses on determining the optimal operational conditions for the partial nitritation reactor while explicitly considering greenhouse gas emissions and ensuring the most suitable conditions for de-ammonification by the anammox reactor. The conventional nitrification/denitrification model and the conventional nitrification/denitrification with added partial nitritation /anammox side-stream were simulated on Dynamita’s simulation software SUMO22 (SUMO4N model) following the Water Environmental Research Foundation protocol for model development, model calibration, and model validation. SUMO22’s in-built carbon footprint tool was used to analyze carbon footprints (Scope 1 and Scope 2). Initial steady-state models (namely, the conventional nitrification/denitrification model and the partial nitritation/anammox model) were set up, and their mainstreams were optimized for dissolved oxygen in aerobic reactors based on the ammonium-nitrogen (NHx-N) load. Furthermore, the partial nitritation /anammox model’s side-stream was optimized for scenarios of partial nitritation reactor dissolved oxygen ranging from 0.25 mg/L to 3 mg/L. The intermittent aeration technique alternated between anoxic and aerobic zones within the partial nitritation reactor. The best-fit scenario was determined based on maximum gains in partial nitritation/anammox reactor dynamics and overall carbon footprint reduction, while maintaining nitrogen removal efficiency. The results revealed that dissolved oxygen optimization in mainstream aerobic reactors resulted in a 51.24% reduction in total carbon footprint compared to the pre-optimization conditions. In the case of partial nitritation/anammox model’s side-stream optimization, the scenario selected based on optimal system performance was a partial nitritation reactor with a dissolved oxygen concentration of 2 mg/l. This scenario achieved the target 1.32 nitrite-to-ammonium ratio required to maintain a healthy anammox population in the anammox reactor. Moreover, it achieved a 99.9% reduction in NH4-N load in an anammox reactor, a 30% reduction in Scope 1 (greenhouse emissions), and a 65% reduction in Scope 2 (energy consumption) compared to the conventional nitrification/denitrification model. Coupled with the intermittent aeration technique, the greatest carbon footprint reduction, among the evaluated scenarios, was achieved with the most efficient partial nitritation /anammox system behavior. This study demonstrates that integrating a partial nitritation and anaerobic ammonium oxidation side-stream into conventional nitrification/denitrification wastewater treatment plants can substantially reduce energy consumption and greenhouse gas emissions without compromising overall nitrogen removal efficiency. Further research is required to incorporate anammox microbial dynamics into mainstream systems, with the main challenge being operational and maintenance costs. Another major challenge in implementing anammox in the mainstream is managing the population requirements of anammox biomass at lower temperatures than in side-stream systems.
Included in
A Simulation-Based Comparison of Energy Consumption and Carbon Footprint in Municipal Wastewater Treatment Using Conventional Nitrification–Denitrification and Partial Nitritation with Anammox
Online - Microsoft Teams
Municipal wastewater treatment plants are significant contributors to energy consumption and greenhouse gas emissions, particularly during secondary treatment processes. The high carbon footprint of wastewater treatment plants can be primarily attributed to two factors: direct greenhouse gas emissions (Scope 1) and energy consumption (Scope 2). Nitrous oxide released during secondary treatment has a global warming potential 273 times greater than that of carbon dioxide. Moreover, conventional nitrification/denitrification wastewater treatment plants are energy-intensive and associated with greenhouse gas emissions, yet widely implemented for their ease of operation and maintenance. This highlights the need to evaluate alternative treatment configurations that reduce energy use and greenhouse gas emissions without compromising nitrogen removal performance. In line with this, this study investigates the impact of integrating a two-stage partial nitritation/anammox system as a side-stream process in a wastewater treatment plant to evaluate its potential to reduce its carbon footprint. Simulation enables the evaluation of strategies to optimize the operating conditions of the partial nitritation reactor and to determine the maximum feed required to support the growth of anammox bacteria in the anammox reactor. The partial nitritation reactor setup is a critical component of this research, as its development affects the success or failure of implementing the benefits of anammox bacteria, both in terms of greenhouse gas emission and energy consumption. While previous studies have investigated optimal operating conditions for partial nitritation reactors, they have generally not accounted for the associated carbon footprint. This study therefore focuses on determining the optimal operational conditions for the partial nitritation reactor while explicitly considering greenhouse gas emissions and ensuring the most suitable conditions for de-ammonification by the anammox reactor. The conventional nitrification/denitrification model and the conventional nitrification/denitrification with added partial nitritation /anammox side-stream were simulated on Dynamita’s simulation software SUMO22 (SUMO4N model) following the Water Environmental Research Foundation protocol for model development, model calibration, and model validation. SUMO22’s in-built carbon footprint tool was used to analyze carbon footprints (Scope 1 and Scope 2). Initial steady-state models (namely, the conventional nitrification/denitrification model and the partial nitritation/anammox model) were set up, and their mainstreams were optimized for dissolved oxygen in aerobic reactors based on the ammonium-nitrogen (NHx-N) load. Furthermore, the partial nitritation /anammox model’s side-stream was optimized for scenarios of partial nitritation reactor dissolved oxygen ranging from 0.25 mg/L to 3 mg/L. The intermittent aeration technique alternated between anoxic and aerobic zones within the partial nitritation reactor. The best-fit scenario was determined based on maximum gains in partial nitritation/anammox reactor dynamics and overall carbon footprint reduction, while maintaining nitrogen removal efficiency. The results revealed that dissolved oxygen optimization in mainstream aerobic reactors resulted in a 51.24% reduction in total carbon footprint compared to the pre-optimization conditions. In the case of partial nitritation/anammox model’s side-stream optimization, the scenario selected based on optimal system performance was a partial nitritation reactor with a dissolved oxygen concentration of 2 mg/l. This scenario achieved the target 1.32 nitrite-to-ammonium ratio required to maintain a healthy anammox population in the anammox reactor. Moreover, it achieved a 99.9% reduction in NH4-N load in an anammox reactor, a 30% reduction in Scope 1 (greenhouse emissions), and a 65% reduction in Scope 2 (energy consumption) compared to the conventional nitrification/denitrification model. Coupled with the intermittent aeration technique, the greatest carbon footprint reduction, among the evaluated scenarios, was achieved with the most efficient partial nitritation /anammox system behavior. This study demonstrates that integrating a partial nitritation and anaerobic ammonium oxidation side-stream into conventional nitrification/denitrification wastewater treatment plants can substantially reduce energy consumption and greenhouse gas emissions without compromising overall nitrogen removal efficiency. Further research is required to incorporate anammox microbial dynamics into mainstream systems, with the main challenge being operational and maintenance costs. Another major challenge in implementing anammox in the mainstream is managing the population requirements of anammox biomass at lower temperatures than in side-stream systems.