Performance analysis of pretreatment technologies for seawater desalination

Abstract

The increasing global demand for freshwater, driven by climate change and population growth, has led to a significant deficit in water resources. Seawater desalination has emerged as a viable solution to mitigate water stress, particularly in arid and coastal regions. Among the various desalination methods, seawater reverse osmosis (SWRO) has gained prominence over the past four decades due to advancements in membrane technology and reduced operational costs. This thesis examines two seawater desalination plant configurations: configuration 1, which employs dissolved air flotation (DAF) and ultrafiltration (UF), and configuration 2, which uses DAF and multimedia filtration (MMF). Both configurations aim to produce 1 440 m3/h of drinking water, with performance assessed through process simulations based on seasonal seawater quality parameters from Khafji, Saudi Arabia.

The simulation results reveal that both configurations perform similarly in terms of SWRO efficiency, thanks to effective pretreatment processes. However, operational differences arise under varying temperature conditions, with higher pressure requirements at lower temperatures to meet drinking water standards. Both configurations achieve water recovery rates close to 50%, but configuration 2 demonstrates lower energy and chemical consumption, resulting in reduced operational costs. Configuration 1 has a specific energy consumption of 2.25 kWh/m3, while configuration 2 consumes 2.06 kWh/m3. The operational cost differences, ranging from 0.89 to 0.98 USD/m3 for configuration 1 and 0.69 to 0.86 USD/m3 for configuration 2, are primarily due to UF membrane replacement costs and electrical consumption.