The application of membranes in liquid and gas separation is attractive because of their energy efficiency. Synthesis of membranes with well-defined nanostructure is necessary to achieve highly permeability and selectivity for separation processes. Recently, carbon nanomaterials such as graphene oxide nanoplatelets (GONPs) and carbon nanodots (CNDs) have emerged as an interesting class of nanomaterials due to their unique properties and tailorable functionalities. Incorporation of these nanomaterials in the membranes has been shown to improve membrane selectivity, mechanical robustness, and chemical stability. This dissertation elaborates on developing CNDs or GONPs embedded thin film composite (TFC) membranes using layer-by-layer (LbL) synthesis technique. Regarding the water desalination applications, GONPs were used to enhance the TFC membranes’ selectivity, chlorine resistant properties, and surface hydrophilicity. Incorporation of GONPs in the polyamide layer via LbL method resulted in an increase of surface hydrophilicity and salt rejection properties. Upon exposure to chlorine, GONPs embedded membranes retained salt rejection performance better than the pristine membranes (without GONPs). The LbL assembly was used to synthesize CNDs based TFC membranes for organic solvent nanofiltration (OSN) applications. Using the LbL framework, amineunctionalized CNDs were covalently crosslinked with trimesoyl chloride monomer to obtain nanoscale membranes. The synthesized membranes manifested high selectivity (up to 90%) when tested for dye molecules such as brilliant blue and disperse red in methanol. As the CNDs synthesized here are fluorescent under UV light, the resultant film is also fluorescent. This property can be harnessed for diagnostic purposes, such as tracking mechanical failure and fouling of the membranes. Based on the results, it can be concluded that the incorporation of carbon nanomaterials in the polymeric membranes has enhanced the hydrophilicity, mechanical stability, and chlorine resistant properties of the membranes. Overall, the LbL platform can be considered as a modular method in embedding nanoparticles in TFC membranes.

Partial nitritation combined with the anaerobic ammonium oxidation (Anammox) process offers a way of replacing the conventional nitrogen removal process of nitrification-denitrification, lowering the need for oxygen and chemical input, as well as reducing the production of sludge. However, as a by-product of the biochemical reaction driven by anammox bacteria, it produces nitrate-nitrogen (NO3- - N) (16-26% nitrogen removed), which is problematic. Microbial desalination cells (MDCs) are a promising technology capable of converting biodegradable organics into electricity (by electroactive bacteria), providing for simultaneous desalination, and wastewater treatment. Despite being a promising technology, MDCs have limitations. The first-proof of-concept of MDC was demonstrated using acetate as the organic source, expensive platinum as a catalyst, and ferricyanide as an electron acceptor in the cathode that makes MDC costly, environmentally unfriendly, and unsustainable. This research investigated the integration of the anammox and nitration processes in MDCs as a long-term biocatalyst/biocathode for sustainable and energy-efficient nitrogen removal and electricity generation. A series of experiments were designed and performed to evaluate the performance of the anammox process as a biocatalyst in MDCs. The results concluded that the anammox process can be used as a biocatalyst to accept electrons in MDCs producing 444 mW/m3 of power density and 84% of ammonium nitrogen removal. Furthermore, the concept of using a one-stage nitritation anammox process as a biocathode in MDC was evaluated and produced a maximum power output of 1007 mW/m3. Two configurations of anammox MDCs (anaerobic-anammox cathode MDC (AnAmmoxMDC) and nitritation-anammox cathode MDC (NiAmoxMDC) were compared with an air cathode MDC (CMDC), operated in fed-batch mode. The NiAmoxMDC showed better performance in terms of power production and nitrogen removal. The co-existence of aerobic ammonium oxidizing bacteria (AOB) and anammox bacteria in the same biocathode of single-stage NiAmoxMDC concluded the resource-efficient wastewater treatment. Furthermore, two-stage nitritation anammox as a biocathode in MDC was evaluated and proved to be energy-efficient bioelectrochemical wastewater treatment by producing 1500 mW/m3 (300 mW/m2) of maximum power output. This research provides the first proof of concept that nitritation-anammox biocathode can provide a sustainable and energy-efficient nitrogen removal along with desalination and bioelectricity generation.

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Yes / Multi-Stage Flash (MSF) desalination process has been used for decades for making fresh water from seawater and is the largest sector in desalination industries. In this work, dynamic optimisation of MSF desalination is carried out using powerful and robust dynamic simulation and optimisation software called gPROMS model builder. For a fixed freshwater demand, a number of optimal combinations of the factors such as heat transfer area, brine flow rate, cooling water flow rate, steam flow in brine heater, Top Brine Temperature, the number of stages, etc. are determined with the objective of maximising the performance ratio of the process (defined as the amount of fresh water produced per unit of energy input) considering the seasonal variations. An attempt has been made to develop an operational schedule for a particular day using dynamic optimisation.

Yes / The use of Reverse Osmosis (RO) process in seawater desalination to provide high-quality drinking water is progressively increased compared to thermal technologies. In this paper, multistage spiral wound RO desalination process is considered. Each stage consists of several pressure vessels (PVs) organised in parallel with membrane modules in each PV being organised in series. This allows disconnecting a set of PVs and membrane modules depending on the requirement of cleaning and maintenance. While this flexibility offers the opportunity of generating several RO configurations, we presented only four such configurations of the RO system and analysed them via simulation and optimisation. Production of different grades of water catering different needs of a city is also considered for each of these configurations. The optimisation has resulted in the optimal operating conditions, which maximises the water productivity and minimises the specific energy consumption of the proposed configurations for a given water grade in terms of salinity. For instance, the results indicate that the proposed RO networks can produce drinking water of 500 ppm salinity with a minimum specific energy consumption of 3.755 kWh/m3. The strategy offers the production of different grades of water without plant shutdown while maintaining the membrane modules throughout the year.

Yes / In this work, an artificial neural network (ANN) model based on the experimental data was developed to study the performance of vacuum membrane distillation (VMD) desalination process under different operating parameters such as the feed inlet temperature, the vacuum pressure, the feed flow rate and the feed salt concentration. The proposed model was found to be capable of predicting accurately the unseen data of the VMD desalination process. The correlation coefficient of the overall agreement between the ANN predictions and experimental data was found to be more than 0.994. The calculation value of the coefficient of variation (CV) was 0.02622, and there was coincident overlap between the target and the output data from the 3D generalization diagrams. The optimal operating conditions of the VMD process can be obtained from the performance analysis of the ANN model with a maximum permeate flux and an acceptable CV value based on the experiment.

Yes / Multistage Flash Desalination (MSF) is currently facing an enormous challenge in cutting of the cost: within the last few years, the MSF experienced a gradual decline in investment compared to other techniques of desalting water and thus, a significant improvement is required to remain attractive for capital investors. Improved process control is a cost effective approach to energy conservation and increased process profitability. In this work, a dynamic model is presented using gPROMS model builder to optimize and control MSF process. The Proportional Integral Derivative Controller (PID) and Generic Model Control (GMC) are used successfully to control the Top Brine Temperature (TBT) and the Brine Level (BL) in the last stage at different times of the year. The objectives of this study are: firstly, to obtain optimum TBT and BL profiles for four different seasons throughout the year by minimizing the Total Seasonal Operating Cost (TSOC); secondly, to track the optimum TBT and BL profiles using PID and GMC controllers with and without the presence of constraints; thirdly, to examine how both types of controllers handle the disturbances which occur in the plant. The results are promising and show that GMC controller provides better performance over conventional PID controller to handle a nonlinear system.

Yes / The coupling of thermal (Multi Stage Flash, MSF) and membrane processes (Reverse Osmosis, RO) in desalination systems has been widely presented in the literature to achieve an improvement of performance compared to an individual process. However, very little study has been made to the combined Multi Effect Distillation (MED) and Reverse Osmosis (RO) processes. Therefore, this research investigates several design options of MED with thermal vapor compression (MED_TVC) coupled with RO system. To achieve this aim, detailed mathematical models for the two processes are developed, which are independently validated against the literature. Then, the integrated model is used to investigate the performance of several configurations of the MED_TVC and RO processes in the hybrid system. The performance indicators include the fresh water productivity, energy consumption, fresh water purity, and recovery ratio. Basically, the sensitivity analysis for each configuration is conducted with respect to seawater conditions and steam supply variation. Most importantly, placing the RO membrane process upstream in the hybrid system generates the overall best configuration in terms of the quantity and quality of fresh water produced. This is attributed to acquiring the best recovery ratio and lower energy consumption over a wide range of seawater salinity.

Yes / Despite the fact of being intensive energy consumption, MSF is a mature technology that characterised by a high production capacity of high-quality water. The multistage flash (MSF) desalination process is one of the prominent thermal desalination used in the industry of seawater desalination to produce high quantity and high quality of freshwater. However, this process consumes large amount of energy and faces thermal limitations due to its high degree of exergy destruction at several units of the process. Therefore, the research of MSF is still existed to elevate the performance indicators and to resolve the concern of high energy consumption. To rectify these limitations, it is important to determine the units responsible in dissipating energy. This study aims to model an industrial MSF process validated against real data and then investigate the exergy destruction and thermodynamic limitations of the process. As a case study, Azzour MSF seawater desalination plant, located in Al Khiran in Kuwait is under the focus. A comprehensive model is developed by analysing several published models. Specifically, the calculation of exergy destruction has embedded both physical and chemical exergies that identified as a strong point of the model developed. As expected, the highest exergy destruction (55.5%) occurs within the heat recovery section followed by the brine heater with exergy destruction of 28.26% of the total exergy destruction. This study identifies the sections of the industrial process that cause the highest energy losses.

Yes / The use of solar thermal energy for water desalination processes is increasing rapidly, particularly in areas where these resources are plentiful. However, solar energy plants are highly affected by the intermittency of day -night cycles and by low irradiation seasons. Although biomass fuel can be used as source of energy for thermal desalination processes, these resources are becoming increasingly scarce, expensive and seasonally available. Integration of solar-biomass technologies for water desalination process may provide the solution to these challenges. This work investigates design options of the Humidification-Dehumidification desalination system integration with the solar-biomass energies. The investigation is based on simulation of the process models in gPROMS platform. Results show that the solar-biomass integrated plant with a thermal storage system can save up to 57 % of the daily energy cost compared to conventional biomass plant. The integrated plant also cuts the CO2 emission by 59 %. Moreover, it has higher daily production capacity than conventional solar plants. / The authors wish to thank the Commonwealth Scholarship Commission in the UK (CSC) for financial support under PhD Scholarships Plan for Low and Middle Income Countries.