A new, energy-efficient approach for boron removal from SWRO plants

A different approach for the operation of seawater reverse osmosis desalination plants, in which the boron concentration in the product water should not exceed 0.3 mgB/L, was recently introduced. The new approach is based on strong acid (either H₂SO₄ or HCl) dosage to the feed seawater to attain pH~4.3, followed by almost complete CO₂ stripping and sub-sequently strong base addition to pH 9.0-9.25. At this high pH range, a high B removal efficiency can be attained even by the new generation of ultra-low energy (high-flux) membranes. This paper addresses the energy saving potential stemming from the elimination or size reduction of the 2nd reverse osmosis (RO) pass and from the use of high-flux elements, both made possible by the new approach. Additionally, total dissolved solids removal from the 1st RO pass permeate can be obtained by operating a smaller, more energy efficient, 2nd RO pass.