Koch Membrane Systems, a US-based world leader in membrane technology, has launched an advanced membrane, the Fluid Systems TFC-SS membrane, to reduce boron levels in drinkable water, particularly for seawater.
"Boron levels in seawater, with boron naturally occurring in the world's oceans at a level of 4-5mg/L, are a particular concern," said Tom Stocker, senior process engineer for KMS. "WHO guidelines require that potable water contains less than 0.5 mg/L of boron, which is a major challenge, particularly in parts of the world like the Mediterranean, where there is a heavy reliance on desalinated water produced through reverse osmosis."
"A series of KMS field tests over the past two years, in Cyprus and California, have shown boron rejection in excess of 90 per cent using a single element in wet test conditions," Stocker said.
This data has also been verified by rigorous laboratory testing at KMS' new state-of-the-art development facilities in Wilmington, Massachusetts. "Unlike impurities such as arsenic, reverse osmosis membranes do not easily reject boron," Stocker said. "Variables such as total dissolved solids (TDS), temperature and the water's pH must all be taken into account. With high salinity feeds such as seawater, boron rejections as high as 90 per cent have been demonstrated, but for low salinity or brackish waters, boron rejection is very dependent on the pH level.
"The pH governs the form of the boron in water due to the equilibrium reaction between boric acid and borate ion. At pH levels higher than 9.3, borate ion starts to predominate. For boron removal on low salinity systems, the feed water is typically first softened then the pH is raised to the pH range of 10 to 10.5 before passing through the TFC-HR membrane to achieve an acceptable performance of over 90 per cent rejection," Stocker said.
The only other technology that can remove boron to the levels demonstrated by the KMS membrane is selective ion exchange resin, a far less cost-effective alternative. As WHO's guidelines start to impact, the KMS Fluid Systems membrane offers an increasingly attractive solution.
This latest innovation is one of several new and improved membrane products from KMS. More information is available from the company's website.