Energy Footprint analysis of brackish groundwater desalination with zero liquid discharge in inland areas of the Arabian Peninsula

Semi-arid regions throughout the world face water scarcity and the need for more efficient and alternative sources of drinking water supply. Inland regions in the Arabian Peninsula have the alternate option of coastal seawater desalination and long-distance conveyance, often with lift to substantial elevation. In several aquifers of this region, naturally occurring radium in groundwater is above acceptable standards and must be reduced. We analyzed the energy footprint of a modular process employing a combination of pellet reactor for radium and hardness minimization, reverse osmosis with intermediate precipitation, and concentrated brine crystallization to achieve high recovery with zero liquid discharge (ZLD). Pilot tests demonstrate technical viability of the selected processes to achieve high recovery, radium and hardness reduction, and over 95% salinity reduction with zero liquid discharge. The results indicate that the energy usage per unit volume of water produced from groundwater is consistently lower than coastal seawater desalination, regardless of the conveyance distance. The substantial reduction of energy, higher recovery and minimized residual discharge of this process are also beneficial to the environment when compared to conventional processes currently being used. The results may be applicable and beneficial to other regions with similar conditions. © 2012 Elsevier B.V. All rights reserved.

The analyses for high-recovery groundwater treatment and zero liquid discharge indicate that processes selected with a modular approach are beneficially applicable and adaptable. High-recovery (>95%) with the zero liquid discharge during groundwater treatment conserves water supply that otherwise would be lost and pose potential adverse environment impacts. The conventional approach to desalinate groundwater in regions of extreme aridity and considerable distance from the sea, such as the Arabian Peninsula, using processes more energy intensive or commonly designed and implemented in higher rainfall regions is being called to question. The recovery limits set in the specifications for semi-arid regions where groundwater resources are non-replenished may not be applicable to regions where groundwater resources are replenished. The reject water in conventional recovery processes should be considered as a resource in regions of scarce groundwater resources rather than a disposal problem. The processes selected and analyzed here have lower energy footprint, operating costs, and energy wastage in comparison to the alternatives of coastal seawater desalination. The attractive energy footprint and savings of high recovery zero liquid discharge processes are considerable compared to seawater desalination alternatives. The alternative desalination of seawater should be considered together with the conveyance and lift to elevated inland areas, when compared to groundwater extraction, treatment and delivery to points of use. Advances in research and implementation of intermediate chemical precipitation allow the fast precipitation and crystallization of dissolved solids in installations with contained physical footprint. Desalination of brackish groundwater using high recovery and zero liquid discharge should therefore be considered in process portfolios during planning efforts. Notation BWRO eFP ICD PR P-RO SBCC S-BWRO S-RO S-SWRO SWRO TDS ZLD brackish water reverse osmosis energy footprint intermediate chemical demineralization pellet reactor primary reverse osmosis with brackish water membrane salt brine capillary crystallization secondary reverse osmosis with brackish water membrane secondary reverse osmosis secondary reverse osmosis with seawater membrane seawater reverse osmosis total dissolved solid zero liquid discharge Acknowledgments The authors thank Dr. Ali Al-Tokhais of the Kingdom of Saudi Arabia for his help in reviewing this manuscript. This is contribution No. 73 of the UCI Urban Water Research Center.