The main focus of this Theme is design and implementation of advanced water treatment technology for treatment and reuse of industrial effluents (oil and gas, manufacturing, etc.), and novel water conservation and hybrid treatment techniques in agriculture and aquaculture.
THE SELF-WATERING GREENHOUSE
PI: TorOve Leiknes
Food security and water security are dependent upon each other. Agriculture consumes between 70-80% of all fresh water used in the world. Therefore, any talk about water security must include a consideration of the water used to grow food. For example, the estimated world average amount of water required to produce a hamburger is ~2,400 liters. In contrast, an average 10 minute shower uses ~100 liters of water. A large percentage of the water used in food production is lost to evapotranspiration. In nature, this water vapor eventually condenses and falls back to the Earth as rain, but rarely falls in the same location from where it evaporated. The growing of crops in greenhouses offers a unique opportunity to recapture water vapor. Because a greenhouse is a closed environment, the evapotranspiration of water vapor can be contained. Traditionally, venting has been added to greenhouses to prevent the buildup of heat and/ or humidity. Researchers at the WDRC are evaluating a new solution: recovery of the water vapor for reuse as irrigation water within the greenhouse. This closes the water cycle within the greenhouse and eliminates the need for additional irrigation water.
The specific solution under evaluation by the WDRC is the use of salt-based liquid desiccants to capture water vapor and the subsequent desalination of these solutions to recover the fresh water. Bench-scale efforts in the laboratory have already shown the potential to dehumidify air using liquid desiccants circulated within hollow fiber membranes. Vacuum membrane distillation has also been used successfully to recover both fresh water and re-usable desiccant solution from spent desiccant solutions. Efforts are underway to make the process more efficient and to evaluate scale up for possible pilot-scale implementation. If ultimately successful on a commercial scale, the liquid desiccant water recycling system could reduce the amount of water required to grow 1 kilogram of the tomatoes and lettuce in our salads from a world average of about 200 liters of fresh water to 1 liter.
FERTILIZER DRIVEN FORWARD OSMOSIS
PI: Noreddine Ghaffour
This project is a collaborative work between WDRC/KAUST and University of Technology, Sydney (UTS), funded by the KAUST SEED program. The main aim of the research is to explore a novel hybrid system integrating a biological wastewater treatment process and fertilizer drawn forward osmosis (FO) for a closed hydroponic system through wastewater reclamation to achieve a sustainable solution for the water-food nexus. The system is driven by renewable energy with potential zero liquid discharge. UTS has developed components of the integrated closed loop concept using fertilizer solutions and wastewater and demonstrated the concept using small-scale pilots. WDRC has investigated severe organic and biofouling of the membranes and aims to conduct field studies treating/reclaiming KAUST wastewater and applying brackish water for irrigation. Research on fertilizer driven forward osmosis (FDFO) processes has been focused on the draw solute selection in terms of improvement of water flux and reduction of reverse diffusion, but the impact of draw solute reverse diffusion on membrane fouling, especially biofouling, has been neglected. Therefore in this project, biofouling of FDFO was investigated in an FDFO system driven by two different fertilizers, namely KNO3 and KH2PO4. The performance of FO system treating synthetic wastewater was determined, and the membrane fouling caused by different fertilizer draw solutes was evaluated. FO membrane using KNO3 as draw solute exhibited more severe flux decline than using KH2PO4. Results showed the significant effect of reverse draw solute diffusion on the FO membrane biofouling, and provided helpful information on a better fertilizer draw solute selection. Building on results from this project, there is a potential for commercialization of the fertilizer-drawn forward osmosis technology that will enable sustainable wastewater reclamation and reuse for irrigation.