A comparative study for the removal of boron and silica from geothermal water by cross-flow flat sheet reverse osmosis method

This study focused on the application of laboratory scale cross-flow flat sheet reverse osmosis (RO) method for boron, salt and silica removal from geothermal water. Most important operating parameters of RO process such as membrane type, operating pressure and feed flow rate (thus the cross-flow velocity) that govern permeate flux, boron, silica and salt removals were investigated. Four different RO membranes, AD-SWRO (GE Osmonics), AG-BWRO (GE Osmonics), BW-30-BWRO (FILMTEC) and AK-BWRO (GE Osmonics) were used to compare their performances. In order to examine the effects of pressure and cross-flow velocity, system was operated at pressures ranging from 15 to 30 bar and cross-flow velocities of 0.16 and 0.33 m/s. Obtained permeate boron concentrations were evaluated according to drinking and irrigation water standards. ► Boron rejection and permeate flux depend on membrane type and operating pressure. ► Pressure increase affected both permeate quality and quality positively. ► Salt and silica were rejected effectively from geothermal water by all membranes. ► SWRO (AD) membrane provided higher boron rejections. ► Increase in flow rate did not affect permeate flux, salt, boron and silica rejections significantly.