Ion-exchange as a method of water pretreatment prior to low-pressure membrane filtration

Incising demand for high quality drinking water results in seeking new, effective processes of water treatment. Those requirements fulfil membrane processes. The two major issues of membrane water treatment processes are the quality of the produced water, which is related to the rejection of targeted solutes, and the membrane fouling leading to permeate flux decline and consequent reduction in the efficiency of the filtration process. Natural organic matter is considered to be a major cause of ultrafiltration membranes fouling during filtration of natural waters. The most common method to prevent from fouling and to increase final water quality is pretreating the influent to the membrane process with the application of conventional unit processes. One of those processes is ion exchange with the use of MIEX (R) resin. The objective of the study was to evaluate the influence of membrane properties (cut-off and polymer material) and MIEX (R) dose on the effectiveness of NOM removal from model solution and natural water in integrated (MIEXDOC)-D-(R)/ultrafiltration process. Integrated process composed of (MIEXDOC)-D-(R) process and ultrafiltration was found to be very effective in removal of natural organic matter from the examined waters. The efficiency of the integrated (MIEXDOC)-D-(R)/ultrafiltration process was found to be only slightly influenced by resin dose and membrane cut-off Even for very small resin doses and UF membranes of high MWCO, the retention of NOM particles was high. The obtained results indicate that combination of two mechanisms of NOM removal: ion exchange with size exclusion, allow to separate wide spectrum of organic substances. Moreover, application of ultrafiltration after (MIEXDOC)-D-(R) process keep to a minimum the secondary pollution water caused by resin carried away from the system.