An optimized pretreatment approach for seawater reverse osmosis processing

Abstract

Increase in water consumption intensified water shortages all over the globe; therefore water is rapidly being perceived as a limited resource of high economic value. Seawater Desalination advancements in both thermal and membrane technologies rendered desalination as an important source of drinking water. The application of RO for seawater desalination has intensified rapidly throughout the globe with the construction of large RO plants. Seawater Reverse Osmosis (SWRO) is a highly effective desalination process; however the main drawback that has been facing this process is fouling of RO membranes including: inorganic, organic, colloidal, and biological fouling. The present study aims at reporting an investigation conducted on a SWRO conventional pretreatment process that optimizes the multi-process pretreatment that is practiced at present. Based on the principle of softening the process includes (coagulationflocculation) using Mg(OH)₂ and CaCO₃, thus inducing simultaneous and quasi-complete control of the pollutants responsible for membrane fouling, as well as partial but appreciable removal of boron. The results of the study showed that the sequences of conducting jar test experiments using optimal concentrations of NaOH and Na₂CO₃ as alkalizing agents and Mg(OH)₂ and CaCO₃ as coagulants at optimal temperatures recorded removal efficiencies as high as: 100 percent for Ca, 99.6percent for Mg, 100percent for Si, 82percent for B, 99percent for Fe, 93percent for VSS, and 58.4percent for TOC, in addition to complete inactivation of total and fecal coliforms. Furthermore, sludge produced from the treatment process was studied and the sludge mass produced as a result of the process is about 7.9 kg-m³.