Date of Defense
27-11-2025 2:00 PM
Location
F1-1117
Document Type
Dissertation Defense
Degree Name
Doctor of Philosophy in Civil Engineering
College
COE
Department
Civil and Environmental Engineering
First Advisor
Prof. Mohamed Mostafa Mohamed
Keywords
Micronanobubbles, aeration, activated sludge, dissolved oxygen, pollutant removal kinetics
Abstract
Aeration is considered one of the most reliable and efficient processes in wastewater treatment. However, conventional aeration systems show low performance with respect to the gas transfer during the treatment process. This poses a challenge in maintaining sufficient dissolved oxygen (DO) concentrations essential for the treatment. The use of micronanobubbles (MNBs) in the aeration process has been proposed as effective tool in water and wastewater treatment owing to their stability and longevity. MNBs’ stability is a distinctive property resulting from several mechanisms, including the repulsion force due to charged surfaces that helps bubbles to resist coalescence/bursting. MNBs’ longevity is represented by their lifespan in water before disappearing. This study focused on the potential use of MNBs in the aeration system of the activated sludge process during wastewater treatment. First, the fundamental properties of the underexplored submicrobubbles (SMBs), as a subset of MNBs, are identified. Then, the effects of SMBs generation conditions such as temperature, aeration time, and water volume on their properties are recognized. After that, this study examined the impact of different generation methods and conditions on oxygen transfer dynamics and the formation of bubbles in both clean water and activated sludge system. After that, the employment of intermittent aeration using different-sized MNBs in an activated sludge system was studied and compared to the use of continuous conventional aeration system under different experimental conditions. Results indicated that (1) submicrobubbles (SMBs), with a median diameter of 2 μm, showed high longevity and stability in water. (2) MNBs with sizes ranging between 100 nm and 2 μm exhibited a higher efficiency in oxygen transfer rates up to two-fold compared to bubbles with sizes bigger than 10 μm. Applying a low air flow rate using MNB generator provided sufficiently small-sized bubbles and higher DO concentration compared to larger bubbles obtained at a higher flow rate using ultrafine diffuser systems. (3) Using intermittent hybrid aeration system, of different-sized MNBs, in activated sludge systems showed better wastewater treatment efficiency compared to continuous aeration used in conventional systems. More specifically, higher removal of COD and TKN from real wastewater was observed under different MLSS values. (4) The removal kinetics of COD and TKN were examined in a batch activated sludge system using zero, first, second, and Grau-second order kinetics. COD removal for both systems, under all examined MLSS values, was best described by Grau-second order kinetics. On the other hand, TKN removal did not follow a specific kinetic model.
Included in
ENHANCEMENT OF AERATION AND ACTIVATED SLUDGE PROCESSES USING MICRONANOBUBBLES FOR EFFICIENT WASTEWATER TREATMENT
F1-1117
Aeration is considered one of the most reliable and efficient processes in wastewater treatment. However, conventional aeration systems show low performance with respect to the gas transfer during the treatment process. This poses a challenge in maintaining sufficient dissolved oxygen (DO) concentrations essential for the treatment. The use of micronanobubbles (MNBs) in the aeration process has been proposed as effective tool in water and wastewater treatment owing to their stability and longevity. MNBs’ stability is a distinctive property resulting from several mechanisms, including the repulsion force due to charged surfaces that helps bubbles to resist coalescence/bursting. MNBs’ longevity is represented by their lifespan in water before disappearing. This study focused on the potential use of MNBs in the aeration system of the activated sludge process during wastewater treatment. First, the fundamental properties of the underexplored submicrobubbles (SMBs), as a subset of MNBs, are identified. Then, the effects of SMBs generation conditions such as temperature, aeration time, and water volume on their properties are recognized. After that, this study examined the impact of different generation methods and conditions on oxygen transfer dynamics and the formation of bubbles in both clean water and activated sludge system. After that, the employment of intermittent aeration using different-sized MNBs in an activated sludge system was studied and compared to the use of continuous conventional aeration system under different experimental conditions. Results indicated that (1) submicrobubbles (SMBs), with a median diameter of 2 μm, showed high longevity and stability in water. (2) MNBs with sizes ranging between 100 nm and 2 μm exhibited a higher efficiency in oxygen transfer rates up to two-fold compared to bubbles with sizes bigger than 10 μm. Applying a low air flow rate using MNB generator provided sufficiently small-sized bubbles and higher DO concentration compared to larger bubbles obtained at a higher flow rate using ultrafine diffuser systems. (3) Using intermittent hybrid aeration system, of different-sized MNBs, in activated sludge systems showed better wastewater treatment efficiency compared to continuous aeration used in conventional systems. More specifically, higher removal of COD and TKN from real wastewater was observed under different MLSS values. (4) The removal kinetics of COD and TKN were examined in a batch activated sludge system using zero, first, second, and Grau-second order kinetics. COD removal for both systems, under all examined MLSS values, was best described by Grau-second order kinetics. On the other hand, TKN removal did not follow a specific kinetic model.