Removal of pesticides and other micropollutants by nanofiltration

Abstract

Mainly in the US nanofiltration (NF) is used for water softening and removal of natural organic matter regarding disinfection by-products. Because it is possible to substitute several conventional treatment steps, NF can also be economically competitive. A relatively high content of organic substances as well as pesticides are present in Elbe River water. Furthermore, the bank filtrate is mixed with hard groundwater which contains a high amount of sulphate. NF was tested to treat the bank filtrate, mainly to investigate the rejection of trace organics like pesticides using NF. It was found that the rejection of uncharged trace organics is mainly influenced by steric hindrances while the high rejection of polar trace organics can be explained by electrostatic interactions with the charged membrane surface. Because the dissociation of polar organics and the surface charge of the membrane depend on pH value, the rejection increases with increased pH. At neutral pH values which are normal in the drinking water treatment, a nearly complete rejection of polar organics was observed.