Rejection characteristics of organic and inorganic pollutants by ultra low-pressure nanofiltration of surface water for drinking water treatment Original Research Article

Rejection characteristics of organic and inorganic pollutants by an ultra low-pressure nanofiltration of surface water for drinking water treatment are demonstrated here. Nanofiltration of surface water from the Tama river, Japan has been studied. Water quality of the river water has been investigated. Long-term operations have been done for investigation of changing of nanofiltration performances caused by membrane fouling. Effects of an application of pretreatment unit are discussed, and its performances are compared with the performances of nanofiltration system without such pretreatment process. Membrane properties such as molecular weight cutoff and surface electric charge have been characterized. Rejection mechanisms of organic and inorganic pollutants by nanofiltration membranes are described regarding size exclusion and electrostatic effect, respectively. Mathematical models, which state transport phenomena of ionic solutes through nanofiltration membranes, are used to estimate effective charge density of nanofiltration membrane. In addition, a comparison of effective charge densities between fresh and fouled nanofiltration membranes is discussed.