242 research outputs found
Seawater, drinking water of the future?
While natural fresh water sources are being depleted and contaminated, the seas and oceans are a virtually unlimited source of water. There is one big catch though; to remove the salt, high amounts of energy are needed. The research of Dr. Vanoppen looks into more economical and sustainable ways to desalinate seawater and aims to generate fresh water from the sea available to water scarce regions all over the world
Influence of osmotic energy recovery/osmotic dilution on seawater desalination energy demand
Supplying fresh, potable water to an ever increasing world population is becoming a major challenge. One possibility is to produce fresh water from seawater by Reverse Osmosis (RO), a process that is very energy intensive. To reduce the energy demand of this process, osmotic dilution (OD)/osmotic energy recovery (OER) systems can be used as pre-treatment. Both Reverse Electrodialysis (RED) and Pressure Retarded Osmosis (PRO) and their non energy-producing counterparts short-circuited RED/ Forward Osmosis (scRED/FO) and assisted RED/FO (ARED/AFO) were modelled as OD/OER devices for RO, in a thermodynamic way. Different mixing ratios of impaired versus salt water (0.5, 1 and 2) were compared at a realistic RO recovery of 50%. A realistic approach for the RED/PRO-RO hybrid process was also modelled incorporating some major losses, to gain a more realistic insight into its possibilities. The thermodynamic modelling revealed that a significant reduction of the SEC is possible with all hybrid processes. The reduction in SEC is less for the non energy-producing systems, but these have the added advantage of requiring a lower membrane area to achieve a similar extent of seawater dilution. From preliminary results of the more realistic modelling, it seems that RED-RO scores better when losses are incorporated. Further thermodynamic and realistic modelling will focus on different RO recoveries, capital cost calculations based on membrane requirements and sensitivity analysis of the different parameters implemented
Assisted reverse electrodialysis : a novel technique to decrease reverse osmosis energy demand
Assisted reverse electrodialysis (ARED) was introduced as a pre-desalination technique for seawater reverse osmosis (RO) for drinking water production. ARED is comparable to an additional applied pressure along the osmotic pressure in pressure assisted osmosis; a small voltage is applied in the same direction as the open cell voltage to increase the desalination speed compared to reverse electrodialysis (RED). This decreases the required membrane area. The concentration of the dilute compartment increases significantly during ARED operation due to the increased speed of desalination. This results in an overall decrease in total cell resistance. Although the energy demand for ARED is higher than for RED, the ARED-RO process still achieves a decrease in overall energy requirements at higher RO recoveries when compared to stand-alone RO. However, ion-exchange membrane prices will have to come down to 1-10 €/m² for the ARED-RO hybrid to become economically viable at current energy prices
Properties governing the transport of organic pollutants through ion-exchange membranes using desalination of complex waste streams in ED
Key physicochemical characteristics governing organic micropollutant adsorption and transport in ion-exchange membranes during reverse electrodialysis
The co-generation of electricity and electrodialysis of seawater in a hybrid system is a promising approach to overcome water scarcity. Reverse electrodialysis harvests energy from the salinity gradient, where seawater is used as a high salinity stream while secondary treated wastewater can be used as a sustainable low salinity stream. Treated wastewater contains organic micropollutants, which can be transported to the seawater stream. The current research establishes a connection between adsorption and transport of organic micropollutants in ion exchange membranes, using a cross-flow stack in adsorption and zero-current experiments. To mimic the composition of treated wastewater, a mixture of nineteen organic micropollutants of varied physicochemical characteristics (e.g. size, charge, polarity, hydrogen donor/acceptor count, hydrophobicity) at environmentally relevant concentrations was used. Depending on the charge, micropollutants develop different types of mechanisms responsible for short-distance interactions with ion-exchange membranes, which has a direct influence in their transport behavior. This study provides a rational basis for the optimization/design of next-generation ion-exchange membranes, in which the permeability toward organic micropollutants should be also included. This investigation highly contributes to understanding the potential hazard posed by organic micropollutants in reverse electrodialysis in seawater desalination systems, where treated wastewater is used as a low salinity stream
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