Correlations and data for the thermophysical properties of seawater are reviewed.Properties examined include density, specific heat capacity, thermal conductivity, dynamic viscosity, surface tension, vapor pressure, boiling point elevation, latent heat of vaporization, specific enthalpy, specific entropy, and osmotic coefficient. These properties include those needed for design of thermal and membrane desalination processes. Results are presented in terms of regression equations as functions of temperature and salinity. The available correlations for each property are summarized with their range of validity and accuracy. Best-fitted new correlations are obtained from available data for density, dynamic viscosity, surface tension, boiling point elevation, specific enthalpy, specific entropy and osmotic coefficient after appropriate conversion of temperature and salinity scales to the most recent standards. In addition, a model for latent heat of vaporization is suggested. Comparisons are carried out among these correlations, and recommendations are provided for each property, particularly over the ranges of temperature and salinity common in thermal and/or reverse osmosis seawater desalination applications.

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Membrane distillation (MD) is a rapidly emerging water treatment technology; however, membrane pore wetting is a primary barrier to widespread industrial use of MD. The primary causes of membrane wetting are exceedance of liquid entry pressure and membrane fouling. Developments in membrane design and the use of pretreatment have provided significant advancement toward wetting prevention in membrane distillation, but further progress is needed. In this study, a broad review is carried out on wetting incidence in membrane distillation processes. Based on this perspective, the study describes the wetting mechanisms, wetting causes, and wetting detection methods, as well as hydrophobicity measurements of MD membranes. This review discusses current understanding and areas for future investigation on the influence of operating conditions, MD configuration, and membrane non-wettability characteristics on wetting phenomena. Additionally, the review highlights mathematical wetting models and several approaches to wetting control, such as membrane fabrication and modification, as well as techniques for membrane restoration in MD. The literature shows that inorganic scaling and organic fouling are the main causes of membrane wetting. The regeneration of wetting MD membranes is found to be challenging and the obtained results are usually not favorable. Several pretreatment processes are found to inhibit membrane wetting by removing the wetting agents from the feed solution. Various advanced membrane designs are considered to bring membrane surface non-wettability to the states of superhydrophobicity and superomniphobicity; however, these methods commonly demand complex fabrication processes or high-specialized equipment. Recharging air in the feed to maintain protective air layers on the membrane surface has proven to be very effective to prevent wetting, but such techniques are immature and in need of significant research on design, optimization, and pilot-scale studies.

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Conventional water resources in many regions are insufficient to meet the water needs of growing populations, thus reuse is gaining acceptance as a method of water supply augmentation. Recent advancements in membrane technology have allowed for the reclamation of municipal wastewater for the production of drinking water, i.e., potable reuse. Although public perception can be a challenge, potable reuse is often the least energy-intensive method of providing additional drinking water to water stressed regions. A variety of membranes have been developed that can remove water contaminants ranging from particles and pathogens to dissolved organic compounds and salts. Typically, potable reuse treatment plants use polymeric membranes for microfiltration or ultrafiltration in conjunction with reverse osmosis and, in some cases, nanofiltration. Membrane properties, including pore size, wettability, surface charge, roughness, thermal resistance, chemical stability, permeability, thickness and mechanical strength, vary between membranes and applications. Advancements in membrane technology including new membrane materials, coatings, and manufacturing methods, as well as emerging membrane processes such as membrane bioreactors, electrodialysis, and forward osmosis have been developed to improve selectivity, energy consumption, fouling resistance, and/or capital cost. The purpose of this review is to provide a comprehensive summary of the role of polymeric membranes in the treatment of wastewater to potable water quality and highlight recent advancements in separation processes. Beyond membranes themselves, this review covers the background and history of potable reuse, and commonly used potable reuse process chains, pretreatment steps, and advanced oxidation processes. Key trends in membrane technology include novel configurations, materials and fouling prevention techniques. Challenges still facing membrane-based potable reuse applications, including chemical and biological contaminant removal, membrane fouling, and public perception, are highlighted as areas in need of further research and development.

Increasing global demand for fresh water is driving the development and implementation of a wide variety of seawater desalination technologies. Entropy generation analysis, and specifically, Second Law efficiency, is an important tool for illustrating the influence of irreversibilities within a system on the required energy input. When defining Second Law efficiency, the useful exergy output of the system must be properly defined. For desalination systems, this is the minimum least work of separation required to extract a unit of water from a feed stream of a given salinity. In order to evaluate the Second Law efficiency, entropy generation mechanisms present in a wide range of desalination processes are analyzed. In particular, entropy generated in the run down to equilibrium of discharge streams must be considered. Physical models are applied to estimate the magnitude of entropy generation by component and individual processes. These formulations are applied to calculate the total entropy generation in several desalination systems including multiple effect distillation, multistage flash, membrane distillation, mechanical vapor compression, reverse osmosis, and humidification-dehumidification. Within each technology, the relative importance of each source of entropy generation is discussed in order to determine which should be the target of entropy generation minimization. As given here, the correct application of Second Law efficiency shows which systems operate closest to the reversible limit and helps to indicate which systems have the greatest potential for improvement.

Microbial-electrode electron transfer is a mechanism by which microbes make their living coupling to electronic circuits, even across long distances. From a chemistry perspective, it represents a model platform that integrates biological metabolism with artificial electronics, and will facilitate the fundamental understanding of charge transport properties within these distinct chemical systems and particularly at their interfaces. From a broad standpoint, this understanding will also open up new possibilities in a wide range of high impact applications in bioelectrochemical system based technologies, which have shown promise in electricity, biochemical, chemical feedstock production but still require many orders of magnitude improvement to lead to viable technologies. Here we review opportunities to understand microbial-electrode electron transfer to improve electrocatalysis (bioelectricity) and electrosynthesis (biochemical and chemical production). We discuss challenges and the ample interdisciplinary research opportunities and suggest paths to take to improve production of fuels and chemicals at high yield and efficiency and the new applications that may result from increased understanding of the microbial-electrode electron transfer mechanism.Bio-electrochemical system (BES) can be expressed as the bidirectional electron transports between biotic and abiotic components, where the redoxactive microorganisms or bio-macromolecules act as the catalysts that facilitate the exchange process 1 . A glossary of important terms is provided in box 1. A model system of BES that has been widely studies is the Microbial Fuel Cell (MFCs). Similar to the conventional fuel cell, the microorganisms can transport electrons to the anodes of MFC after oxidizing the electron donors, thus generating the electrical flow toward the cathode 2 . Meanwhile, certain microorganisms are also known for their capability to reduce the electron acceptors such as nitrate, perchlorate or metals in the cathodes 3 . Other BESs such as Microbial electrolysis cells (MEC), Microbial electrosynthesis (MES),Microbial solar cells (MSCs), and Plant microbial fuel cells (PMFCs) also share similar electron transport strategy. These direct electron transport processes created a novel and promising possibility to bridge the fundamental researches in microbiology, electrochemistry, environmental engineering, material science and the applications in waste remediation & resource recovery, sustainable energy production, and bio-inspired material development. The basic working principles and the applications of these different BESs have been comprehensively reviewed by many different groups [4][5][6][7] . Bioelectrochemcial systemsEnzymatic electron transport process is one of the earliest BES models which received extensive attention due to the interests in development of amperometric biosensors and enzymatic fuel cell in late 20 th century [8][9][10][11][12] . In this system, the electrons generated from specific enzymatic reactions can be either...

In a previous paper, the authors have given correlations for seawater thermophysical properties as functions of temperature and salinity, but only for near atmospheric pressures. Seawater reverse osmosis (SWRO) systems operate routinely at pressures of 6 MPa or more; however, experimental data for seawater properties at elevated pressures (P = 0.1-12 MPa) are limited to a salinity of 56 g/kg. To accurately model and design SWRO and thermal desalination systems, a reliable method of estimating the effect of pressure on seawater properties is required. In this work, we present this method and new correlations for seawater thermophysical properties that are valid within the range: t = 0-120 °C, S = 0-120 g/kg, and P = 0-12 MPa. Seawater isothermal compressibility data, available until a salinity of 56 g/kg, were used to develop a correlation for compressibility that is extrapolated to 160 g/kg. Thermodynamic identities were then used to develop accurate pressure dependent correlations for seawater: density, isobaric expansivity, specific heat capacity, enthalpy, entropy and Gibbs energy. New correlations were proposed for 2 surface tension and osmotic coefficient were reviewed. Uncertainty bounds were calculated for each correlation.