Desalination for irrigation use: chemical pre-treatment study of Reverse osmosis plant

Desalinated brackish water is becoming an important water source for agricultural irrigation. In Brackish water desalination, pretreatment of reverse osmosis is the key step in designing the plants to avoid membrane fouling and scaling. It is enormously important to carry out a study designed at ensuring the optimization of the pretreatment system for brackish desalination plant in order to optimize the quality of the water fed through the reverse osmosis membranes, to guarantee the highest performance and to minimize the number of shutdowns for chemical cleaning. In this paper, performance evaluation carried out for a brackish water reverse osmosis plant for agricultural application, located in Dokkala Region in Morocco.

Adsorption of textile dyes on raw and decanted Moroccan clays: Kinetics, equilibrium and thermodynamics

AbstractInexpensive and easily available Moroccan natural clays were investigated for the removal availability of textile dyes from aqueous solution. For this purpose, the adsorption of methylene blue (MB) as reference molecule, malachite green (MG) representative of cationic dyes and methyl orange (MO) representative of anionic dyes, was studied in batch mode under various parameters. The clays were characterized by means of XRD, cationic exchange capacity and BET surface area analysis. The experimental results show that, the adsorption was pH dependent with a high adsorption capacity of MB and MG in basic range and high adsorption of MO in acidic range. The pseudo-second-order kinetic model provided the best fit to the experimental data for the adsorption of MB and MG by the clays. However, the adsorption of MO was more suitable to be controlled by an intra-particle diffusion mechanism. The equilibrium adsorption data were analyzed by Langmuir, Freundlich and Dubinin–Radushkevich isotherm models. The adsorption process was found to be exothermic in nature in the case of MB and MO. However, the adsorption of MG was endothermic

PERFORMANCES OF REVERSE OSMOSIS AND NANOFILTRATION IN DESALINATION OF RIVER BRACKISH WATER

As many countries in the world, Morocco is facing problems in the supply of water due to an increasing demand and decrease of conventional resources. To face the problems, Morocco proceeded since a long time to use other non conventional water resources such as wastewater reuse or desalinating water. The desalination option which was limited to south and coasts extends more and more towards the central regions. Mrirt is among the north cities where a construction of desalination plant is expected soon. The city is far from the coast and the water to be treated is slightly brackish. The city already has a standard treatment plant of drinking water. The National Office of Electricity and Drinking Water and Ibn Tofail University decided to conduct this study to compare the performances of Reverse Osmosis and Nano filtration technologies. The experiments are conducted using pilot plants and various commercial membranes such as BW30LE4040, NF90 and NF270. Several parameters were examined in order to optimize the system performance, including operating pressure, flux, system recovery, salt rejection and specific energy consumption (SEC). The obtained results showed that the experiment results appear to be compatible with those obtained by the software prediction. The experiment results  at 10 bars of feed pressure, for BW30 the values of recovery rate is 28% and 0.95 kwh/m3of energy consumption. For NF90, the recovery rate is 30% and  0.75 kwh/m3 of energy. But in the predict results, and under the same of the operating conditions pilot plant, the values of energy consumption are 0.91 of BW30 and 0.70 of NF90. Thus, the prediction software results shows that the maximum recovery rate can be achieved to 85% at 20 l/h/m2 of average flux, andthe operating pressure needed to run the RO membrane is significantly higher (14, 6 bar as compared to 9, 90 bar) than the NF membrane

Subaqueous foraging among carnivorous dinosaurs

Secondary aquatic adaptations evolved independently more than 30 times from terrestrial vertebrate ancestors1,2. For decades, non-avian dinosaurs were believed to be an exception to this pattern. Only a few species have been hypothesized to be partly or predominantly aquatic3,4,5,6,7,8,9,10,11. However, these hypotheses remain controversial12,13, largely owing to the difficulty of identifying unambiguous anatomical adaptations for aquatic habits in extinct animals. Here we demonstrate that the relationship between bone density and aquatic ecologies across extant amniotes provides a reliable inference of aquatic habits in extinct species. We use this approach to evaluate the distribution of aquatic adaptations among non-avian dinosaurs. We find strong support for aquatic habits in spinosaurids, associated with a marked increase in bone density, which precedes the evolution of more conspicuous anatomical modifications, a pattern also observed in other aquatic reptiles and mammals14,15,16. Spinosaurids are revealed to be aquatic specialists with surprising ecological disparity, including subaqueous foraging behaviour in Spinosaurus and Baryonyx, and non-diving habits in Suchomimus. Adaptation to aquatic environments appeared in spinosaurids during the Early Cretaceous, following their divergence from other tetanuran theropods during the Early Jurassic17