Commonly, the main contributors to the environmental impacts of desalination are energy consumptions and chemical usage. In this work, two alternatives for pretreatment of seawater feed to Fujairah-1 seawater reverse osmosis (SWRO) plant in United Arab Emirates, were compared: sedimentation-based and ultrafiltration (UF) membrane-based pretreatment. Life cycle analysis (LCA) methodology was applied in this case study research, based on real data from the Fujairah-1 plant for the sedimentation-based system and full design data for the alternative UF system, provided by X-Flow (R). By use of the LCA, a comprehensive environmental modeling of the considered options was conducted. The pretreatment systems, including their components (e.g., equipment) and material and energy flows throughout their lifetime, were modeled. Environmental impacts of these systems, using alternative energy mixes, were also modeled. Our findings indicate that a membrane-based pretreatment has a lower environmental impact, throughout the system's life cycle, than the existing sedimentation-based pretreatment in the Fujairah-1 desalination plant. This result holds under all alternative energy mix assumptions; including renewable, natural gas, oil, and nuclear energy. Our findings also show that the most significant contributor to the overall environmental impacts of both pretreatment systems is energy consumption. (C) 2013 Elsevier B.V. All rights reserved.