83 research outputs found
A multi evaporator desalination system operated with thermocline energy for future sustainability
All existing commercial seawater desalination processes, i.e. thermally-driven and membrane-based reverse osmosis (RO), are operated with universal performance ratios (UPR) varying up to 105, whilst the UPR for an ideal or thermodynamic limit (TL) of desalination is at 828. Despite slightly better UPRs for the RO plants, all practical desalination plants available, hitherto, operate at only less than 12% of the TL, rendering them highly energy intensive and unsustainable for future sustainability. More innovative desalination methods must be sought to meet the needs of future sustainable desalination and these methods should attain an upper UPR bound of about 25 to 30% of the TL. In this paper, we examined the efficacy of a multi-effect distillation (MED) system operated with thermocline energy from the sea; a proven desalination technology that can exploit the narrow temperature gradient of 20 °C all year round created between the warm surface seawater and the cold-seawater at depths of about 300â600 m. Such a seawater thermocline (ST)-driven MED system, simply called the ST-MED process, has the potential to achieve up to 2 folds improvement in desalination efficiency over the existing methods, attaining about 18.8% of the ideal limit. With the major energy input emanated from the renewable solar, the ST-MED is truly a âgreen desalinationâ method of low global warming potential, best suited for tropical coastal shores having bathymetry depths of 300 m or more
Assessment of Wastewater Quality of Paharang Drain and its Impact on the Ground Water Quality of Adjacent Areas
This study was conducted to assess the effect of wastewater quality of Paharang drain Faisalabad on ground water quality of adjacent areas. Ground water samples and drain water samples were collected and analyzed by using standard methods. Parameters of wastewater samples were compared with Pakistan National Environmental Quality Standards (NEQS). Results indicated that physico-chemical parameters including pH, total dissolved solids (TDS), chloride, fluoride and total hardness were found exceeding the permissible limits in wastewater samples. Similarly, few physicochemical parameters in groundwater were found within the permissible limit while electrical conductivity (EC), TDS, chlorides (Cl), fluoride (F), and total hardness in most of samples were found above the Pak EPA and WHO standard limits. Heavy metals like nickel (Ni), chromium (Cr), iron (Fe), lead (Pb), and arsenic (As) were found within the prescribed concentrations in drain and ground water samples. Statistical analysis showed significant effect of some drain wastewater parameters like conductivity, TDS, salt, temperature, and Cl on the corresponding ground water quality. A strong positive correlation between pH, EC, TDS, Salt, and Cl in drain wastewater and strong positive correlation between EC, TDS and Salt in ground water samples was observed. For improving the ground water quality in the adjacent areas textile wastewater treatment all factories is required, and a combined effluent treatment plant (CETP) at the Paharang drain is also recommended
Desalination by Membrane Distillation
At present, around 25% of water desalination processes are based on distillation. Similar to classical distillation, membrane distillation is a phased-change process in which a hydrophobic membrane separates two phases. Membrane distillation is considered an emerging player in the desalination, food processing and water treatment market. Due to its high salt rejection, less fouling propensity, operating at moderate temperature and pressure, membrane distillation is considered as a future sustainable desalination technology. The distillation process is quite well known in desalination. However, membrane distillation emerged a few decades ago, and a thorough understanding is needed to adapt this technique in the near future. This review chapter introduces the classical distillation and membrane distillation as an emerging technology in the desalination arena. Heat and mass transfer and thermodynamics in membrane distillation, characteristics of the performance metrics of membrane distillation are also described. Finally, the performance evaluation of MD is presented. The possibility of using low-grade heat in membrane distillation allows it to integrate directly to solar energy and industrial waste heat
Understanding the organic micropollutants transport mechanisms in the fertilizer-drawn forward osmosis process
© 2019 Elsevier Ltd We systematically investigated the transport mechanisms of organic micropollutants (OMPs) in a fertilizer-drawn forward osmosis (FDFO) membrane process. Four representative OMPs, i.e., atenolol, atrazine, primidone, and caffeine, were chosen for their different molecular weights and structural characteristics. All the FDFO experiments were conducted with the membrane active layer on the feed solution (FS) side using three different fertilizer draw solutions (DS): potassium chloride (KCl), monoammonium phosphate (MAP), and diammonium phosphate (DAP) due to their different properties (i.e., osmotic pressure, diffusivity, viscosity and solution pH). Using KCl as the DS resulted in both the highest water flux and the highest reverse solute flux (RSF), while MAP and DAP resulted in similar water fluxes with varying RSF. The pH of the FS increased with DAP as the DS due to the reverse diffusion of NH4+ ions from the DS toward the FS, while for MAP and DAP DS, the pH of the FS was not impacted. The OMPs transport behavior (OMPs flux) was evaluated and compared with a simulated OMPs flux obtained via the pore-hindrance transport model to identify the effects of the OMPs structural properties. When MAP was used as DS, the OMPs flux was dominantly influenced by the physicochemical properties (i.e., hydrophobicity and surface charge). Those OMPs with positive charge and more hydrophobic, exhibited higher forward OMP fluxes. With DAP as the DS, the more hydrated FO membrane (caused by increased pH) as well as the enhanced RSF hindered OMPs transport through the FO membrane. With KCl as DS, the structural properties of the OMPs were dominant factors in the OMPs flux, however the higher RSF of the KCl draw solute may likely hamper the OMPs transport through the membrane especially those with higher MW (e.g., atenolol). The pore-hindrance model can be instrumental in understanding the effects of the hydrodynamic properties and the surface properties on the OMPs transport behaviors
Catalytic degradation of Oâcresol using H2O2 onto Algerian ClayâNa
Clay material is used as a catalyst to degrade an organic pollutant,. This study focused on the Oâcresol oxidative degradation in aqueous solution by adding H2O2 and MontâNa. The catalytic tests showed a high catalytic activity of MontâNa, which made it possible to achieve more than 84.6% conversion after 90 minutes of reaction time at 55 °C in 23.2 mM H2O2. The pH value was found to be negatively correlated with the degradation rate of Oâcresol. UVâVis spectrophotometry revealed that the increase of degradation rate at low pH is related to the formation of 2âMethylbenzoquinone as intermediate product. In addition, the content of iron in MontâNa decreased after the catalytic test, bringing further evidence about the Oâcresol catalytic oxidation. The mineralization of Oâcresol is also confirmed by the different methods of characterization of MontâNa after the catalytic oxidation test. The effect of the Oâcresol oxidation catalyzed by natural clay is significant.Financial support for this work by the Algerian Directorate General of Scientific Research and Technological Development (DGRSDT) and the Ministry for Higher Education and Scientific Research is gratefully appreciated
Solar, wind and geothermal energy applications in agriculture: back to the future?
The agri-food chain consumes about one third of the worldâs energy production with about 12% for crop production and nearly 80% for processing, distribution, retail, preparation and cooking (Fig. 1.1) (FAO, 2011b). The agri-food chain also accounts for 80â90% of total global freshwater use (Hoff, 2011) where 70% is for irrigation alone. Additionally, on a global scale, freshwater
production consumes nearly 15% of the entire energy production (IEA, 2012). It can therefore be argued that making agriculture and the agri-food supply chain independent from fossil fuel use has huge potential to contribute to global food security and climate protection not only for the next decades, but also for the coming century. Provision of secure, accessible and environmentally
sustainable supplies of water, energy and food must thus be a priority.
One of the major objectives of theworldâs scientists, farmers, decision-makers and industrialists is to overcome the present dependence on fossil fuels in the agri-food sector. This dependency increases the volatility of food prices and affects economic access to sustenance. For example, Figure 1.2 shows the close interrelationship between the crude oil price index and the cereals
price index. An increasing energy demand for cultivation is particularly important in regions with expanding irrigated agriculture using pumped water. This translates to a food-related risk to energy security.
The development and commercialization of renewable energy sources such as solar, wind and geothermal provides great potential to reduce costs in the agri-food sector. For instance, in addition to power generation, the main uses of geothermal waters are for space heating, district
heating, spas balneology, aquaculture and greenhouse heating (Lund and Boyd, 2015). However, much work remains to be done to make better use of renewable energy in the agri-food sector.
The aim of this introductory chapter is to critically review recent developments in solar, wind and geothermal energy applications in agriculture and the agri-food sector such as processing, distribution, retail, preparation and cooking
Water Desalination Using Geothermal Energy
The paper provides a critical overview of water desalination using geothermal resources. Specific case studies are presented, as well as an assessment of environmental risks and market potential and barriers to growth. The availability and suitability of low and high temperature geothermal energy in comparison to other renewable energy resources for desalination is also discussed. Analysis will show, for example, that the use of geothermal energy for thermal desalination can be justified only in the presence of cheap geothermal reservoirs or in decentralized applications focusing on small-scale water supplies in coastal regions, provided that society is able and willing to pay for desalting
Capacity building strategies and policy for desalination using renewable energies in Algeria
The integration of renewable resources in desalination and water purification is becoming increasingly attractive. This is justified by the fact that areas of fresh water shortages have plenty of solar energy and these technologies have low operating and maintenance costs. In this paper, an overview of capacity building strategy and policy for desalination in Algeria is presented. Importance of training and education on renewable energies is also outlined. The contribution of the Middle East Desalination Research Center in capacity building and research and development in desalination in Algeria is also presented.Capacity building Renewable energy Desalination Education Research
State-of-the-art of renewable energy sources used in water desalination: Present and future prospects
The last decade has seen a worldwide increase in the use of alternative energy sources, especially renewable energy (RE), including its application in desalination. In the past many experimental and pilot investigations were presented which allowed the costs and effectiveness of such integrated solutions to be estimated. The present review describes experience related to the use of solar thermal technologies (solar collector and concentrated solar power technologies), solar electricity (photovoltaic and concentrator photovoltaics), wind, hydroelectric (hydropower, tidal, wave and ocean thermal energy), biomass and geothermal energy (power and thermal) as well as hybrid systems. The costs relating to energy and desalinated water production are investigated in the case of various technological processes used in desalination. The main directions for development of the RE systems investigated are discussed and their advantages and disadvantages are assessed. Such a comprehensive review showed that the expansion of the effective use of RE sources is still hampered by several techno-economic aspects. The paper focuses on the main concerns of the need to optimise energy processes, especially by creating more energy-efficient and economically effective solutions, energy storage, energy recovery and the expansion of off-grid systems. As a result of the analysis it was concluded that, despite some disadvantages, the combining of RE with desalination processes requires further intensive research and demonstration units for longer term performance. Regulations to develop less energy-intensive desalination technologies are also still needed
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