Researchers in Turkey have investigated the removal of boron from geothermal water by an integrated process, that couples reverse osmosis (RO) with an ion exchange-ultrafiltration hybrid method.
Desalination tests were performed using a mini-pilot scale brackish water reverse osmosis (BWRO) system, which was installed at the Yenikale Geothermal Heating Center in Izmir. Geothermal waters have higher boron concentrations than seawater.
Boron-selective chelating ion-exchange resin Dowex with a particle size of 20 µm was employed for removal of boron from BWRO permeate of geothermal water. A submerged hollow fibre type ultrafiltration membrane module was used for filtration.
The researchers studied the effect of process variables – such as resin concentration in the suspension, flow rates of fresh and saturated ion exchange resins, and flow rate of permeate – on the efficiency of the hybrid process for boron removal from RO permeate of geothermal water.
Adequate removal of boron from geothermal water can be achieved by the secondary treatment of desalinated geothermal water coming from the RO desalination process.
The product water obtained using this integrated method has sufficiently low salinity and an acceptable boron level to allow its use for irrigation. The target level of boron in this hybrid process is acceptable for the citrus trees and grapes grown in the Mediterranean region.
