This paper describes the processes, methods, backgrounds, and economic challenges, of Desalination and Water Recycling and provide current examples of both. To create a baseline with which to compare the two methods, I will also delve into the history of California water policy. This complicated past is the reason water importation into Southern California remains the main method of obtaining water. Yet, as the current drought continues and technology advances, the need for imported water will become obsolete as the methods for recycling and desalinating water become less expensive, more convenient and more equitable. In the conclusion, all the methods will be compared and I will give suggestions on potential solutions for solving San Diego’s water dependence.

Desalination technology provides fresh water to the arid regions around the world. Multi-Stage Flash (MSF) distillation process has been used for many years and is now the largest sector in the desalination industry. Top Brine Temperature (TBT) (boiling point temperature of the feed seawater in the first stage of the process) is one of the many important parameters that affect optimal design and operation of MSF processes. For a given pressure, TBT is a function of Boiling Point Temperature (BPT) at zero salinity and Temperature Elevation (TE) due to salinity. Modelling plays an important role in simulation, optimisation and control of MSF processes and within the model, calculation of TE is therefore important for each stages (including the first stage, which determines the TBT). Firstly, in this work, several Neural Network (NN) based correlations for predicting TE are developed. It is found that the NN based correlations can predict the experimental TE very closely. Also predictions of TE by the NN based correlations were found to be good when compared to those obtained using the existing correlations from the literature. Secondly, a hybrid steady state MSF process model is developed using gPROMS modelling tool embedding the NN based correlation. gPROMS provides an easy and flexible platform to build a process flowsheet graphically. Here a Master Model connecting (automatically) the individual unit model (brine heater, stages, etc.) equations is developed which is used repeatedly during simulation and optimisation. The model is validated against published results. Seawater is the main source raw material for MSF processes and is subject to seasonal temperature variation. With fixed design the model is then used to study the effect of a number of parameters (e.g. seawater and steam temperature) on the freshwater production rate. It is observed that, the variation in the parameters affect the rate of production of fresh water. How the design and operation are to be adjusted to maintain a fixed demand of fresh water through out the year (with changing seawater temperature) is also investigated via repetitive simulation. Thirdly, with clear understanding of the interaction of design and operating parameters, simultaneous optimisation of design and operating parameters of MSF process is considered via the application MINLP technique within gPROMS. Two types of optimisation problems are considered: (a) For a fixed fresh water demand throughout the year, the external heat input (a measure of operating cost) to the process is minimised; (b) For different fresh water demand throughout the year and with seasonal variation of seawater temperature, the total annualised cost of desalination is minimised. It is found that seasonal variation in seawater temperature results in significant variation in design and some of the operating parameters but with minimum variation in process temperatures. The results also reveal the possibility of designing stand-alone flash stages which would offer flexible scheduling in terms of the connection of various units (to build up the process) and efficient maintenance of the units throughout the year as the weather condition changes. In addition, operation at low temperatures throughout the year will reduce design and operating costs in terms of low temperature materials of construction and reduced amount of anti-scaling and anti-corrosion agents. Finally, an attempt was made to develop a hybrid dynamic MSF process model incorporating NN based correlation for TE. The model was validated at steady state condition using the data from the literature. Dynamic simulation with step changes in seawater and steam temperature was carried out to match the predictions by the steady state model. Dynamic optimisation problem is then formulated for the MSF process, subjected to seawater temperature change (up and down) over a period of six hours, to maximise a performance ratio by optimising the brine heater steam temperature while maintaining a fixed water demand.

No presente trabalho foram avaliados processos alternativos de dessalinização visando a recuperação e reuso da água contida em salmouras concentradas, sendo o processo de cristalização assistida por destilação por membranas (MDC) investigado com profundidade. Foi desenvolvido um modelo diferencial para o processo de destilação por membranas por contato direto (DCMD), contemplando métodos termodinâmicos rigorosos para sistemas aquosos de eletrólitos fortes, bem como mecanismos de transferência de calor e massa e efeitos de polarização de temperatura e concentração característicos deste processo de separação. Com base em simulações realizadas a partir do modelo matemático assim desenvolvido, foram investigados os principais parâmetros que influenciam o projeto de um módulo de membranas para DCMD. O modelo foi posteriormente estendido com equações de balanço de massa e energia adicionais para incluir a operação de cristalização e desta forma representar o processo de MDC. De posse dos resultados das simulações e do modelo estendido, foi desenvolvido um método hierárquico para o projeto de processos de MDC, com o objetivo de conferir características de rastreabilidade e repetibilidade a esta atividade. Ainda a partir do modelo MDC foram discutidos aspectos importantes em MDC como a possibilidade de nucleação e crescimento de cristais sobre a superfície das membranas, bem como o comportamento do processo com sais com diferentes características de solubilidade e largura da zona metaestável. Verificou-se que para sais cuja solubilidade varia muito pouco com a temperatura e que possuem zona metaestável com pequena largura, caso do NaCl, a operação com resfriamento no cristalizador não é viável pois aumenta excessivamente o consumo energético do processo, sendo nesses casos preferível a operação \"isotérmica\" - sem resfriamento no cristalizador - e o convívio com a possibilidade de nucleação no interior do módulo. No extremo oposto, observou-se que para sais com grande variabilidade da solubilidade com a temperatura, um pequeno resfriamento no cristalizador é suficiente para garantir condições de subsaturação no interior do módulo, sem grande ônus energético para o processo. No caso de sais com pequena variabilidade da solubilidade com a temperatura, mas com largura da zona metaestável elevada, existe certo ônus energético para a operação com resfriamento do cristalizador, porém não tão acentuado como no caso de sais com zona metaestável estreita. Foi proposto um fluxograma alternativo para o processo de MDC, onde foi introduzido um circuito de pré-concentração da alimentação antes do circuito de cristalização, para o caso de alimentação com soluções muito diluídas. Este esquema proporcionou um aumento do fluxo permeado global do processo e consequentemente uma redução na área total de membrana requerida. Verificou-se que através do processo com préconcentração da alimentação de 5% até 10% em massa - no caso de dessalinização de uma solução de NaCl - foi possível reduzir-se a área total da membrana em 27,1% e o consumo energético específico do processo em 10,6%, quando comparado ao processo sem pré-concentração. Foram desenvolvidas ferramentas úteis para o projeto de processos de dessalinização por MDC em escala industrial. / Alternative desalination processes aiming at the recovery and reuse of the water contained in concentrated brines were evaluated, being the membrane distillation crystallization (MDC) process investigated in depth. A differential model for the direct contact membrane distillation (DCMD) process was developed for that matter, comprising rigorous thermodynamic methods for strong electrolytes, heat and mass transfer mechanisms and temperature and concentration polarization effects. Based on simulations from the mathematical model thus developed, the main parameters that influence the design of DCMD membrane modules were investigated. The model was further extended with mass and energy balance equations in order to consider the crystallization unit operation and thus suitably represent the MDC process. Based on the simulations results and the extended model, a hierarchical method was developed for the MDC process design, adding traceability and repeatability characteristics to the design activity. Important aspects of the MDC process such as the possibility of nucleation and crystal growth on the membrane surface, as well as the behavior of the process with salts presenting different solubility characteristics and metastable zone widths were further discussed. It was observed that salts presenting negligible temperature dependence regarding their solubility and small metastable zone widths (i.e. NaCl) do not favor the operation with cooling in the crystallizer due to excessive increase in energy consumption, being the isothermal operation more indicated in such cases even at the risk of nucleation inside the membrane module. On the other hand, it was noticed that for salts whose solubility is highly temperature dependent a slight cooling in the crystallizer is enough to assure subsaturated conditions inside the membrane module with minimal energy consumption increase. In the case of salts with low temperature dependence regarding solubility but with large metastable zone widths, the operating strategy of applying cooling in the crystallizer may increase energy consumption but not as significantly as in the case of salts with small metastable zone widths. An alternative flowsheet for the MDC process was proposed, where a pre-concentration loop was introduced before the crystallization loop, showing good results for dilute feeds since it takes advantage of the higher water activity and consequently higher transmembrane fluxes due to the lower concentration. It was perceived a 27.1% reduction in the required membrane surface and a 10.6% energy consumption reduction for the modified flowsheet with the pre-concentration loop, for a feed comprised of 5% of NaCl. Useful tools aimed for the design of industrial scale processes based on MDC were developed.

Submitted by Eunice Novais (enovais@uepg.br) on 2018-07-31T12:05:01Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tatiane Bovaroti.pdf: 1677408 bytes, checksum: 74791391260b47b48abc127d7af4af68 (MD5) / Made available in DSpace on 2018-07-31T12:05:01Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tatiane Bovaroti.pdf: 1677408 bytes, checksum: 74791391260b47b48abc127d7af4af68 (MD5) Previous issue date: 2018-04-12 / Preocupados com a intrusão de água do mar, escassez e má qualidade das reservas de água doce no mundo, diversos países têm estudado e proposto sistemas de alta tecnologia que sejam viáveis para a dessalinização de água salobra ou salina. Este trabalho teve como objetivo principal avaliar a eficiência de um sistema de ultrafiltração (UF) como pré-tratamento, seguido de abrandamento e osmose reversa (OR) para a dessalinização de água salobra em escala piloto, instalado no balneário de Praia de Leste, litoral do estado do Paraná. Para a obtenção da água salobra foi realizada a mistura da água do rio das Pombas com a água do mar até a concentração de 1500 (± 100) mg. L-1 de sólidos dissolvidos totais (SDT). O sistema foi projetado para a produção de 1 m3.h-1 de água doce (permeado da OR) e operou por aproximadamente 3h por dia durante vinte dias não consecutivos. Analisaram-se amostras de nove pontos de coleta durante a primeira (A), segunda (B) e terceira (C) hora de operação. Para a avaliação da qualidade da água os parâmetros analisados foram: SDT, condutividade elétrica, pH, temperatura, cor aparente, turbidez, alcalinidade total, dureza total, cálcio, cloreto, sulfato, coliformes totais e E.coli. Para avaliação da eficiência do sistema, calculou-se a taxa de recuperação e o fluxo de filtração, bem como a leitura de outros parâmetros operacionais como a pressão osmótica. O sistema de UF apresentou remoção média de 95,1% de turbidez e de 98,6% de cor aparente na água salobra. Constatou-se ausência de coliformes totais e E.coli no permeado. Houve variação quanto à remoção de dureza total e cálcio pelo abrandador devido ao tempo de regeneração do sistema. O sistema de OR obteve remoção média de 99,4% de SDT e a maior taxa de recuperação global (UF e OR) foi de 57,4%. / Concerned about the intrusion of sea water, scarcity and poor quality of freshwater reserves in the world, several countries have studied and proposed high technology systems that are feasible for the desalination of brackish or saline water. The main objective of this work was to evaluate the efficiency of an ultrafiltration (UF) system as a pretreatment, followed by slowing and reverse osmosis (RO) for pilot scale saline water desalination, installed in Praia de Leste – coast of the state of Paraná. To obtain the brackish water, the water of the Pombas River was mixed with sea water up to the concentration of 1500 (± 100) mg. L-1 total dissolved solids (TDS). The system was designed to produce 1 m3.h-1 of freshwater (permeate from the RO) and was operated by approximately 3 hours per day during twenty non-consecutive days. Samples from nine collection points were analyzed during the first (A), second (B) and third (C) hours of operation. In order to evaluate the water quality, the parameters evaluated were: TDS, electric conductivity, pH, temperature, apparent color, turbidity, total alkalinity, total hardness, calcium, chloride, sulfate, total coliforms and E.coli. To evaluate the efficiency of the system, the recovery rate and the filtration flow were calculated, as well as the reading of other operational parameters such as osmotic pressure. It was found absence of total coliforms and E. coli in the permeate. There was variation regarding to the removal of total hardness and calcium by the softener due to the regeneration time of the system. The RO system obtained an average of 99.4% of the TDS removal and the highest overall (UF and RO) recovery rate was 57.4%.

The UN predicts that by 2050 there will water shortages throughout the globe. Current sources for safe, clean drinking water are being over mined and exhausted. Seawater provides an alternative water source, but a high salt content makes it unsuitable for the majority of applications. However, reverse osmosis lowers the salt content producing water that is safe for human consumption. Reverse osmosis uses a semi-permeable membrane to prevent the transport of salt but allows for the transport of water. Currently these membranes are susceptible to fouling and contamination, which reduces their efficiency. Graphene-oxide membranes offer a new material for reserves osmosis membranes. Sheets of graphene-oxide are stacked in a layered structure. The separation between the sheets can be controlled using physical confinement, resulting in limited ion permeation of abundant cations in seawater, like Na+ and K+. This is believed to be due to the separation of 0.76 nm between the graphene sheets, forcing the ions to lose its surrounding water molecules, making it unfavourable for the ion to travel through the membrane. Molecular dynamics simulations can give an atomic level insight into the molecular processes within GO membranes. Recent simulations have shown that charged species are attracted to graphene surfaces due to polarisation of the pi-electron system. This work has managed to incorporate these ion-pi interactions into molecular dynamics simulations. Including ion-pi interactions caused some ions, like Na+ and K+, to prefer to lose water molecules and reside at a graphene surface. This work observed the same phenomena when ions were confined to graphene channel ranging from 1.3 nm - 0.7 nm. This observation could have a large impact on whether dehydration is limiting the permeation of these two ions, or if there are additional processes that limit their molecular transport.

This thesis aims first to investigate whether solar panels on the container can provide the process of desalination with energy at the desired location, as well as to dimension a photovoltaic system and battery storage that can run the facility off-grid. Then investigate whether solar cells can be an effective energy solution for Millennium Desalination Device (MDD). The results of this study show that the most annual solar production from containers is 11 510 kWh in Gobabeb, Namibia with a modular efficiency of 22,8 %, which corresponds to 8,2 % operating time per year and is the longest operating time that can be obtained from the all three scenarios. This means that with existing technology and only solar panels on the container, desalination plant is impossible to drive all year round off-grid. The installed power for driving 100 % operating time for one year is 141 kW in Gobabeb and 270 kW in Visby, the corresponding module surface will be lowest 618 m2 and 1184 m2 with modular efficiency of 22,8 %, but there are no additional spaces for all equipment like MDD, solar cells and battery in the container. If the operating time drops to 50 %, the installed power will be 71 kW in Gobabeb, the corresponding module surface will be lowest 415 m2 and battery storage capacity will be at least 160 kWh. Net volume with all equipment will be less than the volume of the container. The cost will be at least 0.2 Swedish kronor per liter of pure water produced with a life of 25 year for solar modules. Usage fee per liter of pure water is 0.03 Swedish kronor based on Gotland’s water and wastewater agency and it means MDD is not a cost-effective solution for Gotland at nowadays. But costs may fall in the future with the price reduction of solar cells and batteries. For water shortage areas, this can be a valuable way to solve the water crisis, but it also depends mostly on the area’s water price.

Maintaining a constant supply of clean drinking water is among the most pressing global challenges in our time. About one-third of the population is affected by the water scarcity and it can only get worse with climate change, rapid industrialization, and the population growth. Even though nearly 70 percent of the planet is covered by water, the consumable freshwater content is only 2.5 percent of it. Unfortunately, the accessible portion of it is only 1 percent. Even so, most of the freshwater bodies are choked with pollution. Considering the vast availability of saline water on the planet and the increasing wastewater generation, seawater desalination, and wastewater treatment and recycling seem to have the potential to address current water-related issues. Therefore, it is necessary to find efficient techniques for seawater desalination and wastewater treatment. The use of nanostructured materials for these applications is becoming a popular approach due to the unique chemical and physical properties they possess compared to bulk materials Solar energy is the cleanest and most abundant renewable natural resource available. Materials for solar photothermal energy conversion are highly sought after for their cost savings, clean environment, and broad utility in providing water heating and/or steam for many applications including domestic water heating and solar-driven desalination. Extensive research efforts have been made to develop efficient solar absorbers with characteristics such as low weight, low thermal conductivity, broad solar absorption and porosity to be able to float on water to provide more efficient and cost-effective solar steam generation systems. Metal NPs have been proposed to take advantage of the high efficiency of the photothermal energy conversion associated with surface plasmon resonance absorption. Nanostructured carbon-based materials such as graphene oxide, carbon nanotubes, carbonized biomass are also in use due to their excellent photothermal energy conversion ability over the range of the visible and near infra-red region of the electromagnetic spectrum. In this dissertation, five projects based on the utility of nanostructured materials for desalination, photocatalysis and water treatment will be discussed. The first three projects involve the fabrication and design of plasmonic and carbon-based photothermal materials for applications in solar steam generation, water desalination, and wastewater treatment. In the fourth project, a unique shape of ZnO nanostructure was synthesized for photodegradation of organic dyes in industrial wastewater. The final project demonstrates the shape-controlled synthesis of iron carbide nanostructures and composite materials of aminated graphene oxide for the removal of Cr(VI) from wastewater.

The design, construction and testing of a reverse-osmosis (PV-RO) desalination system for fresh water shortage area is presented. The system operates from salt water or brackish water and can be embedded in a renewable energy power supply system, since many fresh shortage areas are remote and isolated. Special attention is given to the energy efficiency of small-scale reverse osmosis desalination systems. Limitations of conventional control strategy using toggle control are presented. Based on this, an objective of creating a small-scale reverse osmosis desalination system was set out. Initially, the background information is presented. This includes the natural resources crisis and main desalination technologies and the viability of the integration with renewable energy source. A reverse osmosis (RO) desalination system was assembled and set up at the Curtin University of Technology, Perth, Western Australia Supervisor Control And Data Acquisition (SCADA) system was built using a Human Machine Interface software and a programmable logic controller (PLC). Instrumentation that included signal conditioners was made in analysis of the system characteristics. Initial testing of the system was conducted after the system design and configuration was accomplished. Testing results were used as a guideline for the development of the whole system. / Modelling and simulation of the system components in MATLABSimulink is presented, together with a discussion of the control systems modelling and design procedure, in which the aim was to improve the efficiency of the reverse osmosis system. Simulations show the designed reverse osmosis system with Proportional Integral and Derivative (PID) controller has better performance than other controllers. This consequently leads to a lower overall cost of the water, as well as reducing full maintenance cost of the electric drives in the reverse osmosis unit. Additionally, the configuration of the remote control system through General Package Radio System (GPRS) network is depicted. After the PID control algorithm was programmed into the Programmable Logic Controller (PLC), system experiments were carried out in short durations and long durations. System performance was monitored and experimental results prove that the new control strategy applied increase the water productivity and is able to improve the system efficiency up to 35%. Based on the data obtained from the simulations and experiments, Mundoo Island was chosen to be the location for a case study. The electric load profile of the island was derived from the Island Development Committee in Mundoo. / A water demand profile was created and modelled in Matlab to be the input of the reverse osmosis system. The electric load of the reverse osmosis system was generated from Matlab simulation. This result was entered in Hybrid Optimisation Model for Electric Renewables (HOMER) simulator. Having the designed RO unit as one of the electric loads, the entire remote area power supply (RAPS) system was tested in simulations which shows the energy cost is AUS$0.174 per kWh, lower than the Island Development Committee budget estimation of AUS$0.25 per kWh. The cost of the water treatment is very promising at AUS$0.77 per m3.

Una de las aplicaciones más importante de los procesos de filtración por membrana es en el área de tratamiento de agua por ultrafiltración, nanofiltración u ósmosis inversa. Entre los problemas más serios encontrados en estos procesos destaca la aparición de los fenómenos de ensuciamiento y envejecimiento de las membranas que limitan la eficacia de la operación tanto en la separación de los solutos, como en el flujo de permeado, afectando también el ciclo de vida de las membranas.Para reducir el coste de la producción y mejorar la robustez y eficacia de estos procesos es imprescindible disponer de modelos capaces de representar y predecir la eficiencia y el comportamiento de las membranas durante la operación. Una alternativa viable a los modelos teóricos, que presentan varias particularidades que dificultan su postulado, la constituyen los modelos basados en el análisis de los datos experimentales, entre cuales destaca el uso de las redes neuronales. Dos metodologías han sido evaluadas e investigadas, una constando en la caracterización de las interacciones entre las membranas y los compuestos orgánicos presentes en el agua de alimentación, y la segunda basada en el modelado de la dinámica de operación de las plantas de desalinización por ósmosis inversa.Relaciones cuantitativas estructura‐propiedad se han derivado usando redes neuronales de tipo back‐propagation, para establecer correlaciones entre los descriptores moleculares de 50 compuestos orgánicos de preocupación para la salud pública y su comportamiento frente a 5 membranas comerciales de ósmosis inversa, en términos de permeación, absorción y rechazo. Para reducir la dimensión del espacio de entrada, y para evitar el uso de la información redundante en el entrenamiento de los modelos, se han usado tres métodos para seleccionar el menor número de los descriptores moleculares relevantes entre un total de 45 que caracterizan cada molécula. Los modelos obtenidos se han validado utilizando un método basado en el balance de materia, aplicado no solo a los 50 compuestos utilizados para el desarrollo de los modelos, sino que también a un conjunto de 143 compuestos orgánicos nuevos. La calidad de los modelos obtenidos es prometedora para la extensión de la presente metodología para disponer de una herramienta comprensiva para entender, determinar y evaluar el comportamiento de los solutos orgánicos en el proceso de ósmosis inversa. Esto serviría también para el diseño de nuevas y más eficaces membranas que se usan en este tipo de procesos.En la segunda parte, se ha desarrollado una metodología para modelar la dinámica de los procesos de ósmosis inversa, usando redes neuronales de tipo backpropagation y Fuzzy ARTMAP y datos experimentales que proceden de una planta de desalinización de agua salobre Los modelos desarrollados son capaces de evaluar los efectos de los parámetros de proceso, la calidad del agua de alimentación y la aparición de los fenómenos de ensuciamiento sobre la dinámica de operación de las plantas de desalinización por osmosis inversa. Se ha demostrado que estos modelos se pueden usar para predecir el funcionamiento del proceso a corto tiempo, permitiendo de esta manera la identificación de posibles problemas de operación debidas a los fenómenos de ensuciamiento y envejecimiento de las membranas. Los resultados obtenidos son prometedores para el desarrollo de estrategias de optimización, monitorización y control de plantas de desalinización de agua salobre. Asimismo, pueden constituir la base del diseño de sistemas de supervisón capaces de predecir y advertir etapas de operación incorrecta del proceso por fallos en el mismo, y actuar en consecuencia para evitar estos inconvenientes. / One of the more serious problems encountered in reverse osmosis (RO) water treatment processes is the occurrence of membrane fouling, which limits both operation efficiency (separation performances, water permeate flux, salt rejection) and membrane life‐time. The development of general deterministic models for studying and predicting the development of fouling in full‐scale reverse osmosis plants is burden due to the complexity and temporal variability of feed composition, diurnal variations, inability to realistically quantify the real‐time variability of feed fouling propensity, lack of understanding of both membrane‐foulants interactions and of the interplay of various fouling mechanisms. A viable alternative to the theoretical approaches is constituted by models developed based on direct analysis of experimental data for predicting process operation performance. In this regard, the use of artificial neural networks (ANN) seems to be a reliable option. Two approaches were considered; one based on characterizing the organic compounds passage through RO membranes, and a second one based on modeling the dynamics of permeate flow and separation performances for a full‐scale RO desalination plant.Organic solute sorption, permeation and rejection by RO membranes from aqueous solutions were studied via artificial neural network based quantitative structure‐property relationships (QSPR) for a set of 50 organic compounds for polyamide and cellulose acetate membranes. The separation performance for the organic molecules was modeled based on available experimental data achieved by radioactivity measurements to determine the solute quantity in feed, permeate and sorbed by the membrane. Solute rejection was determined from a mass balance on the permeated solution volume. ANN based QSPR models were developed for the measured organic sorbed (M) and permeated (P) fractions with the most appropriate set of molecular descriptors and membrane properties selected using three different feature selection methods. Principal component analysis and self‐organizing maps pre‐screening of all 50 organic compounds defined by 45 considered chemical descriptors were used to identify the models applicability domain and chemical similarities between the organic molecules. The ANN‐based QSPRs were validated by means of a mass balance test applied not only to the 50 organic compounds used to develop the models, but also to a set of 143 new compounds. The quality of the QSPR/NN models developed suggests that there is merit in extending the present compound database and extending the present approach to develop a comprehensive tool for assessing organic solute behavior in RO water treatment processes. This would allow also the design and manufacture of new and more performing membranes used in such processes.The dynamics of permeate flow rate and salt passage for a RO brackish water desalination pilot plant were captured by ANN based models. The effects of operating parameters, feed water quality and fouling occurrence over the time evolution of the process performance were successfully modeled by a back‐propagation neural network. In an alternative approach, the prediction of process performance parameters based on previous values was achieved using a Fuzzy ARTMAP analysis. The neural network models built are able to capture changes in RO process performance and can successfully be used for interpolation, as well as for extrapolation prediction, fact that can allow reasonable short time forecasting of the process time evolution. It was shown that using real‐time measurements for various process and feed water quality variables, it is possible to build neural network models that allow better understanding of the onset of fouling. This is very encouraging for further development of optimization and control strategies. The present methodology can be the basis of development of soft sensors able to anticipate process upsets.

In this thesis, experimental and numerical studies have been carried out to investigate the performance of a solar desalination system working on humidification-dehumidification principle under the climatological conditions of Ankara, Turkey. The desalination unit was configured mainly by a double-pass flat plate solar air heater with two glass covers, pad humidifier, storage tank and dehumidifying exchanger. The system used in this work is based on the idea of closed water and open air cycles. A computer simulation program based on the mathematical model was developed by means of MATLAB software to study the effect of different environmental, design, and operational parameters on the desalination system productivity. In this simulation program, the fourth order Runge-Kutta method was used to solve the energy balance equations simultaneously and numerically. In order to compare the obtained theoretical results with experimental ones and validate of the developed mathematical model of the system, an experimental study has been carried out. For that, an experimental set-up was designed, constructed and tested at the solar house of the Mechanical Engineering Department of METU. In addition, the existing solar desalination system was integrated with an evacuated tubular solar water heater unit (closed water circulation) and performance of the system has been studied experimentally.