Interests and limitations of nano-filtration for the removal of volatile organic compounds in drinking water production

Most of volatile organohalide compounds (HOVs) present in surface waters an d ground waters are carcinogenic. In drinking water, they represent a dange r for human health and are present in water resources. The objective of thi s study was to characterize the performances of nanofiltration as a refinin g step for removing these compounds at trace level in water. Three HOV comp ounds which are toxic and highly present in natural waters were selected: t richloroethylene, tetrachloroethylene and chloroform. Performances of diffe rent nanofiltration organic membranes to remove these compounds are present ed. High rejection ratios were obtained. Influence of pressure on selectivi ty is low. Rejection mechanisms are discussed. Separation seems partially g overned by steric effects, but another phenomenon was noticed and character ized: HOVs absorb, diffuse and then desorb from organic membranes. This phe nomenon was especially observed for chloroform. As a consequence of desorpt ion in the filtrate, the regulation limits for drinking water were not alwa ys reached. Moreover, some modifications of membrane properties were observ ed by chemical ageing tests.