A novel approach for SWRO desalination plants operation, comprising single pass boron removal and reuse of CO 2 in the post treatment step Academic Article uri icon

abstract

  • A different approach is presented for the operation of seawater RO desalination plants in which the boron concentration in the product water should not exceed 0.3 mgB/l. The approach is based on strong acid (either H 2 SO 4 or HCl) dosage to the feed water to attain pH ∼ 4.3, followed by CO 2 stripping and subsequently strong base addition to pH 9.00–9.25. At this high pH range, a high B removal efficiency is attained, and since the water is practically devoid of carbonate species, no CaCO 3(s) scaling takes place, and pH elevation is limited by Mg(OH) 2(s) precipitation, expected only at pH > 9.45. The approach enables operation in the absence of antiscalants. Furthermore, CO 2 stripping is effected in stripping towers in two steps: the high CO 2(aq) concentration is first stripped by vacuum-operated stripping towers and the CO 2 -rich air is used for dissolution of calcite in the post treatment stage. The remaining CO 2 mass is stripped to the atmosphere using blower-assisted stripping towers. This paper aims at introducing the new concept and providing “proof of concept”. The paper addresses experimental and theoretical aspects of the proposed process, as well as engineering and economic evaluation. The proposed approach is shown to be both technically feasible and cost effective, as compared with conventional boron removal alternatives.

publication date

  • January 1, 2012