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Abstract

The State of Qatar and the Gulf Cooperation Council (GCC) region are located in a hyper-arid area with no rivers, over-abstracted groundwater supply and limited rainfall. Consequently, with the discovery of oil and gas and the associated economic prosperity, the State of Qatar and the GCC region have relied on desalination of seawater from the Arabian Gulf. As of 2013, the GCC region held a 70% share of total global desalination capacity.Multi-Stage Flash (MSF) desalination technology has been the source of water supply in the State of Qatar and the GCC region for the past few decades due to the low cost of energy in these countries and the problems historically faced by Reverse Osmosis (RO) membrane processes in dealing wih the high salinity of the Arabian Gulf. MSF is a thermal process that distills water through stages based on high temperature and changing pressures. The systems suffer from high energy requirements and low recovery rates resulting in significant discharge of brine with elevated temperature to the ambient receiving water. RO on the other hand relies on applying a positive pressure to pass permeate through a fine polymer filter material against the osmotic pressure gradient. RO is widely adopted worldwide due to its lower energy consumption and increased product recovery. With recent developments the technology can cover the high salinity of the Arabian Gulf (40,000 mg/L to 55,000 mg/L total dissolved solids). Nevertheless, RO systems require extensive pretreatment to ensure the integrity of the membrane and to prevent blocking of the fine pores. This makes the process susceptible to surface water quality fluctuations such as during algal blooms and therefore its application in Qatar is still challenging due to the shallow and enclosed nature of the Arabian Gulf.Subsurface intake processes for RO have the potential to reduce the effects of fluctuations in source water quality and reduce the energy intensity of the process, since they provide natural filtration of the source water and simplify the extensive pretreatment requirements necessary to protect the RO membranes. However, significant tradeoffs occur by using subsurface intakes. For instance, intake pumping may be increased to overcome the additional headloss through the intake media while the construction phase also involves increased civil works. This research investigates the environmental impacts associated with the operation phase of RO systems using both open intake and beach well intake systems theoretically located in the State of Qatar, since operational phase impacts typically comprise most of the environmental loads in cradle-to-grave assessments.The study utilizes Life Cycle Assessment (LCA) methodology to assess a wide range of effects from the systems. The ReCiPe lifecycle impact indicator approach is utilized with mid-point impact indicators including climate change, marine eutrophication, terrestial acidification, photochemical oxidant formation, particulate matter formation, marine ecotoxicity, water depletion, mineral resource depletion and fossil fuel depletion. The RO system, its pretreatment and intake will be sized and modelled for a desalinated water output of 100,000 m3/d using a combination of fundamental process equations and commercially available software. The results will show a clear direction from an environmental perspective on which type of intake system Qatar should consider if implementing seawater RO as a preferred desalination technique.

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/content/papers/10.5339/qfarc.2018.EEPD635
2018-03-12
2020-09-27
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http://instance.metastore.ingenta.com/content/papers/10.5339/qfarc.2018.EEPD635
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