Evaluación de procesos de desalinización y su desarrollo en México

Existen diversos procesos de desalinización y se diferencian por costos, impacto ambiental, calidad del producto y energía consumida. Mediante comparación entre procesos térmicos y de membranas se encontraron las diferentes tecnologías existentes para desalar agua de mar, número de plantas instaladas, tecnología utilizada, fuentes de abastecimiento y uso del agua desalinizada. La factibilidad técnica y principal objetivo del trabajo consistió en la comparación de los sistemas de desalinización térmicos y de membranas respecto a costos de producción en USD/m3 y consumo energético en kWh/m3. Los procesos de desalinización se realizan desde 1970, siendo por membrana: ósmosis inversa (OI), electrodiálisis(ED), nanofiltración (NF); por sistemas térmicos: destilación múltiple etapa(MED), destilación flash múltiple etapa (MSF) y destilación solar (DS). De las 13000 plantas instaladas, el 50% es de OI, 33% NF, 1% MED y 4% MSF. Las fuentes de abastecimiento más utilizadas son agua de mar (60%) y agua salobre (22%). Los sectores beneficiados con agua desalinizada son el municipal (66%) e industrial(23%). El tipo de tecnología que requiere menor consumo energético es OI, de 2 a 2.8 kWh/m3 y costo de 0.6 USD/m3; las tecnologías MED y MSF consumen de 3.4 a 4 kWh/m3 y de 5 a 8 kWh/m3, respectivamente, con un costo de producción de 1.5 USD/m3 y 1.10 USD/m3. La comparación entre tecnologías permite determinar que el consumo energético y costo de producción de OI es menor y con mayor producción de agua desalinizada; además presenta ventajas significativas sobre el resto debido a que no requiere cambios de estado, como en MED y MSF. La OI es el proceso más viable en producción, energía consumida y costo

Using Desalination to Improve Agricultural Yields: Success Cases in Mexico

Water scarcity is a global problem, motivating growth and development of new technologies for water treatment, reuse and desalination. For many arid regions in Mexico, especially in the northwest, agriculture is an important economic activity. The Yaqui Valley in Sonora, Mexico, faces problems related to aquifer overexploitation and saline intrusion, which have increased salt concentration in well water to 2000–9000 mg/L total dissolved solids (TDS) and led to soil salinization and low crop yields. This work evaluates the effect of TDS in irrigation water on crop yield. A 150 m3/d desalination plant was used, consisting of 12 SWC4B-MAX membrane modules, with 98% rejection and 75% recovery. Two crops were irrigated with control (4000 mg/L) and desalinated water (200 mg/L). Sorghum (Sorghum) had yields of 7.9 and 8.8 ton/ha, whereas tomatillo (Physalis philadelphica) had yields of 30.82 and 35.88 ton/ha, respectively. Evidently, the desalination process influences agricultural yields

Desalación por ósmosis inversa y su aprovechamiento en agricultura en el valle del Yaqui, Sonora, México

Sonora, situado al noroeste de México, ocupa el segundo lugar en cultivos de riego en el país. Los problemas de disponibilidad de los recursos hídricos, principalmente para agricultura en ese estado, se deben a la alta concentración de sales en los pozos, que van desde 2 000 hasta 5000 mg/l de sólidos disueltos totales (SDT). Estos altos valores de SDT son atribuidos a efectos de intrusión salina (Dévora, Gonzalez, & Saldivar, 2009), al tener una excesiva explotación del manto acuífero (Conagua, 2011). Sin embargo, el uso de tecnologías de desalación y modelos de predicción del proceso permiten aprovechar el recurso de manera óptima tanto en agua producto como en el rechazo. Es por esto que el objetivo es definir un modelo matemático de simulación para la predicción de la operación de una planta desaladora de ósmosis inversa alimentada por agua salobre, validando que el agua producto cumpla con los límites permisibles para su uso en agricultura. Con motivo de validar el modelo, el experimento consistió en habilitar una planta desaladora por ósmosis inversa (OI), con capacidad nominal de 100 m3/d, compuesta por ocho membranas SWC4 de 8”X40”, para ser utilizada en el riego del cultivo de sorgo (Sorghum), el cual presenta un rendimiento de 100%, a una concentración máxima de 2 000 mg/l de SDT en el agua de riego (4 mS/cm), en un área de 0.25 ha, con la finalidad de evaluar rendimiento en kg/m2 (ton/ha). Se regó la mitad del terreno con agua desalinizada (promedio de 64.8 mg/l de SDT) y la otra mitad con agua salobre de pozos subterráneos (promedio de 6 610 mg/l de SDT). Con el apoyo de un equipo de medición multiparamétrico modelo YSI 556 se determinó en el agua de alimentación, rechazo y permeado, la conductividad eléctrica (ìS/cm), sólidos disueltos totales (mg/l), pH y temperatura (°C). Con los datos obtenidos de la planta piloto se diseñó un modelo de simulación en la plataforma de MATLAB R2009a, usando Simulink, que cumple con la función de predecir el comportamiento de la planta desaladora, obteniendo concentraciones de agua producto y rechazo en diferentes arreglos con iteraciones de control, que incluye recirculación de salmuera en diferentes volúmenes. De forma subsecuente, este modelo fue utilizado para simular el aprovechamiento de caudal en el agua de rechazo, con la finalidad de incrementar la sustentabilidad del proceso. Los resultados del estudio muestran que al alimentar un agua de 6 610 mg/l de SDT, las corrientes de producto y rechazo son de 64.8 y 21 300 mg/l de SDT, respectivamente. La evaluación del proceso muestra que el costo de producción de agua es de 6.05 MX$/m3, muy similar a lo reportado por la International Desalination Association, que es de 6.70 MX$/m3. Con el uso de esta agua desalinizada se logró un incremento de producción de 1 ton/ha de sorgo, comparado al riego con agua salada. Estos datos se usaron para validar y calibrar el modelo. Los resultados de la modelación de recirculación muestran que conforme sea menor el porcentaje de recirculación de salmuera se pueden realizar hasta cinco iteraciones, sin incrementar la concentración del agua de alimentación por arriba de 42 000 mg/l, que es lo máximo permitido por la membrana utilizada en la planta. Se incrementó la productividad agrícola, por lo cual las inversiones públicas y privadas en el sector rural se consideran viables en el corto plazo. Se encontró que es posible, para las condiciones de la planta de 100 m3/d, recircular total o parcialmente la corriente de salmuera. Se pueden hacer varias iteraciones con esta corriente sin afectar de modo significativo el agua producto ni llevar al máximo la capacidad de la planta. Entre mayor sea el porcentaje de salmuera recirculada, menos iteraciones podrán realizarse, pero serán reducidas en mayor medida las descargas al medio ambiente

Chemical Composition of Selected Brands of Bottled Water Commercilaized in Tripoli, Libya

Bottled water is one of the sources of drinking water in many developed and developing countries, including Libya. One of the greatest concerns is the health effects of low mineral content or lack of essential minerals in bottled water. The aim of this study was to evaluate the chemical quality of selected brands of bottled water in Tripoli. Water quality parameters such as physical (color, turbidity, total dissolved solids (TDS)), chemical (pH, total hardness (T.H), sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), chloride (Cl−), bicarbonate (HCO3−), carbonate (CO32−), sulphate (SO42−), and nitrite (NO2−), were determined using standard procedures. The results showed a widespread in the characteristics of investigated bottled waters, yet the majority met the various national and international bottled water standards for physic-chemical parameters except for pH (5 brands (<6.5))

State of the Art of Desalination in Mexico

This research paper presents a review of the state of the art of desalination in Mexico, with the aim of clarifying the main challenges and opportunity areas for desalination as the main solution to overcome water stress. First, the current situation and forecasts on the availability of water resources in Mexico are described, followed by the main economic, social, and legislative issues of desalination. Mexico’s installed capacity for the different desalination technologies and their evolution in recent years was investigated, followed by a comparison with global trends. The current state of research and development in desalination technologies carried out by Mexican institutions was also studied. The results show that membrane technology plants account for 88.85%, while thermal technology plants account for the remaining 11.15%. Although Mexico presented a 240% increase in its desalination capacity in the last 10 years, it has not been enough to overcome water stress, so it is concluded that in the future, it is necessary to increase its capacity in greater proportion, specifically in the areas with greater scarcity, which can be achieved with the joint participation of academy–industry–government through the creation of autonomous organizations, social programs, and/or public policies that promote it

Effect of Temperature on Energy Consumption and Polarization in Reverse Osmosis Desalination Using a Spray-Cooled Photovoltaic System

Reverse osmosis (RO) desalination is considered a viable alternative to reduce water scarcity; however, its energy consumption is high. Photovoltaic (PV) energy in desalination processes has gained popularity in recent years. The temperature is identified as a variable that directly affects the behavior of different parameters of the RO process and energy production in PV panels. The objective of this study was to evaluate the effect of temperature on energy consumption and polarization factor in desalination processes at 20, 23, 26 and 30 °C. Tests were conducted on a RO desalination plant driven by a fixed 24-module PV system that received spray cooling in the winter, spring and summer seasons. The specific energy consumption was lower with increasing process feed temperature, being 4.4, 4.3, 3.9 and 3.5 kWh m−3 for temperatures of 20, 23, 26 and 30 °C, respectively. The water temperature affected the polarization factor, being lower as the temperature increased. The values obtained were within the limits established as optimal to prevent the formation of scaling on the membrane surface. The spray cooling system was able to decrease the temperature of the solar cells by about 6.2, 13.3 and 11.5 °C for the winter, spring and summer seasons, respectively. The increase in energy production efficiency was 7.96–14.25%, demonstrating that solar cell temperature control is a viable alternative to improve power generation in solar panel systems

Effect of Temperature on Diluate Water in Batch Electrodialysis Reversal

A high percentage of the agricultural wells in the state of Sonora are overexploited, thus generating a significant degree of saline intrusion and abandonment by nearby communities. In this paper, the effect of temperature on the final concentration of diluted water was evaluated with variations in voltage and input concentration in a batch electrodialysis reversal (EDR) process in order to find the optimal operating conditions, with an emphasis on reducing the energy consumption and cost of desalinated water. Thirty-six samples were prepared: eighteen samples of 2000 mg/L total dissolved solids (TDS) and eighteen samples of 5000 mg/L TDS; brackish well water of 639 mg/L TDS and synthetic salt were mixed to obtain these concentrations. Three different temperatures (25, 30, and 35 °C) and two different voltages (10 and 20 V) were tested for each sample after evaluating the limiting current density. The best salt removal occurred in the 20 V sets, with 18.34% higher removal for the 2000 mg/L TDS experiments and 25.05% for the 5000 mg/L experiments (average between the 25 to 35 °C tests). The temperature positively affected the EDR, especially in the experiments at 10 V, where increasing by 10 °C increased the efficiency by 10.83% and 24.69% for 2000 and 5000 mg/L TDS, respectively. The energy consumption was lower with increasing temperature (35 °C), as it decreased by 1.405% and 1.613% for the 2000 and 5000 mg/L TDS concentrations, respectively (average between the 10 and 20 V tests), thus decreasing the cost per m3 of water

Effect of Temperature on Energy Consumption and Polarization in Reverse Osmosis Desalination Using a Spray-Cooled Photovoltaic System

Reverse osmosis (RO) desalination is considered a viable alternative to reduce water scarcity; however, its energy consumption is high. Photovoltaic (PV) energy in desalination processes has gained popularity in recent years. The temperature is identified as a variable that directly affects the behavior of different parameters of the RO process and energy production in PV panels. The objective of this study was to evaluate the effect of temperature on energy consumption and polarization factor in desalination processes at 20, 23, 26 and 30 °C. Tests were conducted on a RO desalination plant driven by a fixed 24-module PV system that received spray cooling in the winter, spring and summer seasons. The specific energy consumption was lower with increasing process feed temperature, being 4.4, 4.3, 3.9 and 3.5 kWh m−3 for temperatures of 20, 23, 26 and 30 °C, respectively. The water temperature affected the polarization factor, being lower as the temperature increased. The values obtained were within the limits established as optimal to prevent the formation of scaling on the membrane surface. The spray cooling system was able to decrease the temperature of the solar cells by about 6.2, 13.3 and 11.5 °C for the winter, spring and summer seasons, respectively. The increase in energy production efficiency was 7.96–14.25%, demonstrating that solar cell temperature control is a viable alternative to improve power generation in solar panel systems

Evaluation of Concentration Polarization Due to the Effect of Feed Water Temperature Change on Reverse Osmosis Membranes

Water is a necessary resource for life development. Its excessive consumption has a negative impact, generating scarcity problems worldwide. Desalination is an alternative to solve these problems; its objective is to reduce the concentration of total dissolved solids to levels suitable for consumption. The most widely used desalination technology is reverse osmosis, which works by means of semipermeable membranes; however, lack of knowledge or wrong operation cause phenomena such as concentration polarization, which reduces the effective area for mass transfer in the membrane, increasing the energy consumption of the process. The objective of the present study is to evaluate the concentration polarization (β) of the concentration in reverse osmosis membranes by varying the temperature in the feed water (23, 25.5, 28, and 35 °C) for different concentrations (5000 and 10,000 mg L−1) in order to reduce its impact on energy consumption (kWh m−3). The results show that as the temperature increases, the specific energy consumption decreases for both concentrations. In the 5000 mg L−1 tests, the specific energy consumption decreased by 0.590 kWh m−3, representing 12.5%. For 10,000 mg L−1 tests, the specific energy consumption shows a reduction of 0.72 kWh m−3, which represents a percentage decrease of 14.54%