Polishing of ceramic ultrafiltration membrane permeates by ion exchange

摘要

The growing demand for freshwater and the increasingly stringent regulations concerning drinking water quality are essentially driving the application of membrane processes in the water treatment sector. The removal of natural organic matter (NOM) from the water being treated has become imperative as these pollutants promote the formation of disinfection byproducts. To remove NOM from water intended for human consumption, use is frequently made of a low-pressure membrane process, i.e. ultrafiltration (UF). An inherent limitation to the use of UF membranes for NOM removal is the poor retention of low-molecular-weight substances. It seemed therefore advisable to examine the potential of another polishing process, namely that of ion exchange, for enhancing the final quality of the water being treated. The aim of this work was to assess the efficiency of the ion exchange process as a method for upgrading the quality of the ceramic membrane permeate, with emphasis placed on NOM removal. The process was conducted using two UF ceramic membranes (molecular weight cutoff of 50 and 300 kDa) and four ion-exchange resins (A200, A400, SBW and MIEX~®). The study has produced the following findings: the UF membranes provided a sufficiently high extent of NOM removal, and the ion exchange process performed after the process of ultrafiltration significantly improved the quality of the water being treated. Of the ion-exchange resins tested, MIEX~® was found to be the most effective.