Boron removal in RO seawater desalination

In the seawater desalination field, the WHO requires that boron concentration in drinking water be below 0.5 mg/l, and this requirement has affected SWRO process design because of the difficulty in achieving such a low boron concentration. In order to overcome this problem, a new SWRO membrane element with higher boron-rejecting performance was developed. This new SWRO membrane element exhibits excellent boron rejection performance of 94–96% with high TDS rejection and high water productivity. This new membrane element could reduce posttreatment loading, and it might lower drinking water production costs. In order to evaluate the economic impact of the new membrane, the production cost of various SWRO systems with post-treatment processes, the BWRO at high pH conditions and boron-adsorbent resin were estimated. As a result, the cost reduction of the new SWRO membrane was estimated to be up to 20% compared to conventional SWRO membranes. The three-stage system, which consists of SWRO followed by BWRO at high pH and the boron-adsorbent resin for the BWRO concentrate, was the most cost effective.

Fig. 6. Correlation between water production cost and boron concentration requirement for Middle East seawater using the TM820H-370 membrane. System (1) = thick solid line; System (2) = broken line; System (3) = thin solid line; System (4) = double line; System (5) = dashed line. Fig. 7. Correlation between water production cost and boron concentration requirement for Middle East seawater using the TM820A-370 membrane. System (1) = thick solid line; System (2) = broken line; System (3) = thin solid line; System (4) = double line; System (5) = dashed line.