How winds and river discharge affect circulation in a mesotidal estuary, San Francisco Bay, USA

Previous studies suggest importance of wind forcing on salt intrusion length and salt flux in river-dominated microtidal estuaries (with tidal range < 2 m). In this study, we investigate the role of wind forcing on salt intrusion in a mesotidal estuary, San Francisco Bay (SFB), with tidal ranges between 2 m and 4 m, through an open-source model of high transferability, the Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM). Meanwhile, we investigate circulation and salinity variation of San Francisco Bay. The model’s performance in hydrodynamics at tidal, spring/neap and seasonal time scales is validated through model-observation comparisons. Through realistically forced and process-oriented experiments, we demonstrate that spring/neap tides can cause fortnightly variations in salinity and currents by modulating vertical mixing and stratification; and seasonal variability of circulation in North Bay is determined by change of river discharge and modified by winds, while in South Bay it is dominated by wind-driven flows. Furthermore, we revealed the role of wind on X2 (the distance from the Golden Gate Bridge to the 2-PSU isohaline at the bottom). The model results show that X2 is primarily influenced by river flow and proportional to river flow to the ¼ power. Meanwhile, wind plays a secondary role in modifying X2 by increasing X2 from 0 to 5 km during low discharge period, while spring/neap tide modulation on X2 is negligible but important for salt balance in sub-regions downstream of X2.

Layering and vertical transport in sheared double-diffusive convection in the diffusive regime

A sequence of two- and three-dimensional simulations are conducted for the double-diffusive convection (DDC) flows in the diffusive regime subjected to an imposed shear. For a wide range of control parameters, and for sufficiently strong perturbation of the conductive initial state, staircase-like structures spontaneously develop, with relatively well-mixed layers separated by sharp interfaces of enhanced scalar gradient. Such staircases appear to be robust even in the presence of strong shear over very long times, with early-time coarsening of the observed layers. For the same set of control parameters, different asymptotic layered states, with markedly different vertical scalar fluxes, can arise for different initial perturbation structures. The imposed shear significantly spatio-temporally modifies the vertical transport of the various scalars. The flux ratio $\gamma ^*$ (i.e. the ratio between the density fluxes due to the total salt flux and the total heat flux) is found, at steady state, to be essentially equal to the square root of the ratio of the salt diffusivity to the thermal diffusivity, consistent with the physical model proposed by Linden & Shirtcliffe (J. Fluid Mech., vol. 87, 1978, pp. 417–432) and the variational arguments presented by Stern (J. Fluid Mech., vol. 114, 1982, pp. 105–121) for unsheared double-diffusive convection.

Low-Cost High Performance Polyamide Thin Film Composite (Cellulose Triacetate/Graphene Oxide) Membranes for Forward Osmosis Desalination from Palm Fronds

Novel low-cost cellulose triacetate-based membranes extracted from palm fronds have been fabricated through the phase–inversion procedure. The cellulose tri-acetate (CTA) membrane was modified by incorporation of graphene oxide (GO) prepared from palm fronds according to the modified Hummer method as well as the preparation of polyamide thin film composite CTA membranes to improve forward osmosis performance for seawater desalination. The surface characteristics and morphology of the prepared CTA, GO, and the fabricated membranes were investigated. The modified TFC prepared membrane had superior mechanical characteristics as well as permeation of water. The performance of the prepared membranes was tested using synthetic 2 M Sodium chloride (NaCl) feed solution. The water flux (Jw) of the thin-film composite (TFC) (CTA/0.3% GO) was 35 L/m2h, which is much higher than those of pure CTA and CTA/0.3% GO. Meanwhile, the salt reverse flux TFC (CTA/0.3% GO) was 1.1 g/m2h), which is much lower than those of pure CTA and CTA/0.3%. GO (Specific salt flux of TFC (CTA/0.3% GO) substrate membrane was 0.03 g/L indicating good water permeation and low reverse salt flux of the TFC membrane compared to CTA. A real saline water sample collected from Hurgada, Egypt, with totally dissolved solids of 42,643 mg/L with NaCl as the draw solution (DS) at 25 °C and flow rate 1.55 L/min, was used to demonstrate the high performance of the prepared TFC membrane. The chemical analysis of desalted permeated water sample revealed the high performance of the prepared TFC membrane. Consequently, the prepared low-cost forward osmosis (FO) thin-film composite CTA membranes can be introduced in the desalination industry to overcome the high cost of reverse osmosis membrane usage in water desalination.

Fault Planes Materials Fill Characteristics, UAE

Abu Dhabi subsurface fault populations triggered basin system in diverse directions, because of their significant role as fluid pathways. Studying fault infill materials, fault geometries, zone architecture and sealing properties from outcrops as analogues to the subsurface of Abu Dhabi, and combining these with well data and cores are the main objectives of this paper. The fault core around the fault plane and in areas of overlap between fault segments and around the fault tip include slip surfaces and deformed rocks such as fault gouge, breccia, and lenses of host rock, shale smear, salt flux and diagenetic features. Structural geometry of the fault zone architecture and fault plane infill is mainly based on the competency contrast of the materials, that are behaving in ductile or in a brittle manner, which are distributed in the subsurface of Abu Dhabi sedimentary sequences with variable thicknesses. Brittleness is producing lenses, breccia and gouge, while, ductile intervals (principally shales and salt), evolved in smear and flux. The fault and fractures are behaving in a sealy or leaky ways is mainly dependent on the percentage of these materials in the fault deformation zone. The reservoir sections distancing from shale and salt layers are affected by diagenetic impact of the carbonates filling fault zones by recrystallized calcite and dolomite. Musandam area, Ras Al Khaima (RAK), and Jabal Hafit (JH) on the northeast- and eastern-side of the UAE represents good surface analogues for studying fault materials infill characteristics. To approach this, several samples, picked from fault planes, were analysed. NW-trending faults system show more dominant calcite, dolomite, anhydrites and those closer to salt and shale intervals are showing smearing of the ductile infill. The other linked segments and transfer faults of other directions are represented by a lesser percentage of infill. In areas of gravitational tectonics, the decollement ductile interval is intruded in differently oriented open fractures. The studied outcrops of the offshore salt islands and onshore Jabal Al Dhanna (JD) showing salt flux in the surrounding layers that intruded by the salt. The fractures and faults of the surrounding layers and the embedment insoluble layers are highly deformed and showing nearly total seal. As the salt behaving in an isotropic manner, the deformation can be measured clearly by its impact on the surrounding and embedment's insoluble rocks. The faults/fractures behaviour is vicious in migrating hydrocarbons, production enhancement and hydraulic fracturing propagation.

Experimental Investigations on Salt Gradient Solar Pond with Additional Non-Convective Zone for Improved Thermal Performance and Stability

Salt gradient solar ponds are to be designed for thermal efficiency and salinity profile stability. As the salt flux moves upward in the pond, the gradient gets destabilized. This is counteracted by intrusion of salt at different levels as and when required. The density of salt is highest at the bottom and minimum at the top. Hence the destabilization effect is more at top that is at the interface of upper convective zone and non-convective zone (NCZ). In order to keep the interface stable, it is desirable to provide a higher slope of salt gradient near it. However, throughout the non-convective zone, it is not feasible to provide higher slope due to solubility limitations. Hence Husain et al (2012) to divide the NCZ into two parts. The top few centimeters may be given a higher slope and the rest of the zone may be given mild slope as usual. Husain et al (2012) have given analysis for the same and found it to be feasible. However, the experimental feasibility of the same needs to be verified. The present work has done an attempt for the same. In this study, an insulated solar pond with a surface area of 1.40 m2and a depth of 1.14 m is built at the SSBT’s College of Engineering and Technology, Jalgaon in the Maharashtra State (India). The three salty water zones (upper convective, non-convective and heat storage) were formed by filling the pond with salty water of various densities. 6 Thermocouples (type Pt100A) (C+0.2%) were used to measure the temperature profile within the pond. A maximum temperature of 47°C was recorded in the heat storage zone in time span considered for study. The results obtained from experimentation is verified with the concept suggested by Hussain et al (2012) it has been found that they are in a good agreement. The influence of varying the thicknesses of the zones present in a salinity gradient solar pond on the temperatures of the upper convective zone (UCZ) and the lower convective zone (LCZ) is investigated. Also, it is found that by adding the additional non convective zone of 50 mm thickness above the UCZ the heat collection capacity of the LCZ is increased noticeably. The study finds that thickness variation of the zones within the pond is a practical feasibility. The system worked for the entire experimental duration effectively without failure.

Interaction-based ion selectivity exhibited by self-assembled, cross-linked zwitterionic copolymer membranes

Water filtration membranes with advanced ion selectivity are urgently needed for resource recovery and the production of clean drinking water. This work investigates the separation capabilities of cross-linked zwitterionic copolymer membranes, a self-assembled membrane system featuring subnanometer zwitterionic nanochannels. We demonstrate that selective zwitterion–anion interactions simultaneously control salt partitioning and diffusivity, with the permeabilities of NaClO4, NaI, NaBr, NaCl, NaF, and Na2SO4 spanning roughly three orders of magnitude over a wide range of feed concentrations. We model salt flux using a one-dimensional transport model based on the Maxwell–Stefan equations and show that diffusion is the dominant mode of transport for 1:1 sodium salts. Differences in zwitterion–Cl− and zwitterion–F− interactions granted these membranes with the ultrahigh Cl−/F− permselectivity (PCl-/PF- = 24), enabling high fluoride retention and high chloride passage even from saline mixtures of NaCl and NaF.

Activated carbon incorporation on forward osmosis membrane surface for enhanced performance

Cellulose triacetate (CTA) is the first-generation forward osmosis (FO) membrane used for desalination. There have been few chemical modifications of the CTA membrane surface. It has improved membrane hydrophilicity, water flux, and salt rejections compared to unmodified CTA membranes. Chitosan containing porous materials as composites resulted in increased pore characteristics. It has motivated to modify the surface of the commercial CTA forward osmosis (FO) membrane by surface coating with chitosan (CS) – powdered activated carbon (AC) mix. The membrane morphology was characterized by SEM, FTIR-ATR, contact angle measurement and AFM. Operation conditions for FO such as the orientation of the membrane active layer, feed and draw solution flow rates, type and concentration of draw salt were optimized with the original CTA membrane. The modified membrane exhibited around two-fold increase in the water flux and reduced reverse salt flux compared to the original CTA membrane. The improved water flux was attributed to the CS-AC coating enhancing water wettability of the membrane surface and the porous AC generating additional water flow channels. Overall, the water flux of the CTA-CS-AC membrane developed in this work was superior to that of CTA and cellulose acetate (CA) membranes reported in the literature.

Aluminate-Based Nanostructured Luminescent Materials: Design of Processing and Functional Properties

Interest in luminescent materials has been continuously growing for several decades, looking for the development of new systems with optimized optical properties. Nowadays, research has been focused on the development of materials that satisfy specific market requirements in optoelectronics, radioelectronics, aerospace, bio-sensing, pigment applications, etc. Despite the fact that several efforts have made in the synthesis of organic luminescent materials, their poor stability under light exposure limits their use. Hence, luminescent materials based on inorganic phosphors are considered a mature topic. Within this subject, glass, glass-ceramics and ceramics have had great technological relevance, depending on the final applications. Supposing that luminescent materials are able to withstand high temperatures, have a high strength and, simultaneously, possess high stability, ceramics may be considered promising candidates to demonstrate required performance. In an ongoing effort to find a suitable synthesis method for their processing, some routes to develop nanostructured luminescent materials are addressed in this review paper. Several ceramic families that show luminescence have been intensively studied in the last few decades. Here, we demonstrate the synthesis of particles based on aluminate using the methods of sol-gel or molten salts and the production of thin films using screen printing assisted by a molten salt flux. The goal of this review is to identify potential methods to tailor the micro-nanostructure and to tune both the emission and excitation properties, focusing on emerging strategies that can be easily transferred to an industrial scale. Major challenges, opportunities, and directions of future research are specified.

Evaluating Fertilizer-Drawn Forward Osmosis Performance in Treating Anaerobic Palm Oil Mill Effluent

Fertilizer-drawn forward osmosis (FDFO) is a potential alternative to recover and reuse water and nutrients from agricultural wastewater, such as palm oil mill effluent that consists of 95% water and is rich in nutrients. This study investigated the potential of commercial fertilizers as draw solution (DS) in FDFO to treat anaerobic palm oil mill effluent (An-POME). The process parameters affecting FO were studied and optimized, which were then applied to fertilizer selection based on FO performance and fouling propensity. Six commonly used fertilizers were screened and assessed in terms of pure water flux (Jw) and reverse salt flux (JS). Ammonium sulfate ((NH4)2SO4), mono-ammonium phosphate (MAP), and potassium chloride (KCl) were further evaluated with An-POME. MAP showed the best performance against An-POME, with a high average water flux, low flux decline, the highest performance ratio (PR), and highest water recovery of 5.9% for a 4-h operation. In a 24-h fouling run, the average flux decline and water recovered were 84% and 15%, respectively. Both hydraulic flushing and osmotic backwashing cleaning were able to effectively restore the water flux. The results demonstrated that FDFO using commercial fertilizers has the potential for the treatment of An-POME for water recovery. Nevertheless, further investigation is needed to address challenges such as JS and the dilution factor of DS for direct use of fertigation.