An Integrative Approach to Dynamic Processes in Reverse Osmosis Desalination

Akele, Omomayowa (2022) An Integrative Approach to Dynamic Processes in Reverse Osmosis Desalination. PhD thesis, University of Nottingham.

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The reverse osmosis membrane module is an integral element of a desalination system as it determines the overall performance of the desalination plant. The fraction of clean water that can be recovered via this process is often limited by salt precipitation. It has become apparent that precipitation plays a critical role in the sustainability of reverse osmosis desalination. Hence, the main objective that guides this research is unravelling some of the mysteries associated with precipitation, whilst considering it in the context of the other dynamic processes at work.

Overall, in this thesis we focus on three main topics:

• Calcium carbonate (CaCO3) precipitation: In Chapter 2 we conduct batch experiments to investigate the effect of SO2−4 on CaCO3 precipitation. The results from this study informs the model formulation and also provides new insights into the precipitation that occurs in desalination.

• Macroscopic reverse osmosis model: A search of the literature revealed that the fundamental processes in reverse osmosis desalination are often studied in isolation. In this study, the individual mechanisms that are considered to play a critical role in the system behaviour are amalgamated. Our main contribution here is a model framework based on experimental observations and existing literature.

• Nondimensionlisation: We nondimensionalised the governing equations in Chapter 4, allowing us to identify the dimensionless groups which control the solution behaviour. These dimensionless groups served as an important tool for understanding the physics of the various phenomena.

• Analysis: In Chapter 5, we made some physical interpretations of the dimensionless numbers and investigated the influence of different dimensionless groups on four quantities: namely, concentration polarisation, osmotic pressure, recovery and porosity. It was shown that the influence of each dimensionless group changes when we move from a single-solute systems to a multi-component system. The results also provided significant insight on the relative influence of fluid dynamics and solute transport on precipitation and recovery.

Taken collectively, the content of this thesis establishes a framework for analysing and understanding reverse osmosis membrane operations. The study undertaken by the author sheds light on some of the complex interplay between sub processes such as precipitation, fluid flow, mass transport which together influence recovery and in turn process sustainability. It also lays the groundwork for future research into the control of precipitation.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: King, John
Icardi, Matteo
Vandeginste, Veerle
Keywords: Desalination, Reverse Osmosis, Nondimensionalisation, Mathematical Modelling, Precipitation, Calcium Carbonate, CaCO3, NaCl, Sodium Chloride, membrane operations, membrane
Subjects: Q Science > QA Mathematics > QA299 Analysis
Faculties/Schools: UK Campuses > Faculty of Science > School of Mathematical Sciences
Item ID: 68559
Depositing User: Akele, Omomayowa
Date Deposited: 02 Aug 2022 04:40
Last Modified: 02 Aug 2022 04:40

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