Recycling of Reverse Osmosis (RO) Reject Streams in Brackish Water Desalination Plants Using Fixed Bed Column Softener

In this study, simulated reverse osmosis (RO) concentrate (limestone seeds) was fed to a continuous Fixed Bed Column Softener. The product was evaluated in terms of its suitability as feed to secondary RO process. The results indicate that this process has the potential to reduce calcium ion concentration from initial value of 361 to 39.03 mg/L and bicarbonate concentration from 1199 to 651 mg/L. The Stiff-Davis saturation index was reduced from 1.62 to 0.103 and the Langelier Saturation Index of the concentrate from 1.6 (High scale forming) to 0.07 (low scale forming), thus treated water has properties of low fouling potential that facilitate its recycling in secondary RO plants.