Pre-treatments to reduce fouling of low pressure micro-filtration (MF) membranes

Despite the fact that natural organic matter (NOM) is significantly smaller than the pore size of microfiltration (MF) membranes, fouling due to organic compounds has emerged as a problematic issue for both potable water and wastewater membrane filtration. Pre-treatment of the feed water can be a useful strategy for reduction or mitigation of these fouling effects. The aim of this investigation was to evaluate various combined pre-treatment methods for reducing NOM fouling of laboratory scale micro-filtration (MF) membranes, including treatment with adsorbents such as MIEX® (MIEX® is a registered trademark of Orica Australia Pty. Ltd.) and powdered activated carbon (PAC) as well as coagulation with alum. High performance size-exclusion chromatography (HPSEC) was applied to determine molecular weight (MW) distribution and proved to be a simple analytical technique, capable of detecting the onset of fouling by observation of the >50,000 Da 'colloidal' peak in the water sources examined. Results obtained showed that treatments that reduce the majority of bulk water dissolved organic carbon (DOC) of all MW ranges, including 'colloidal' (very high MW) material successfully prevented short-term fouling of MF, where treatments that removed most of the DOC but did not remove the colloidal components, were unable to prevent fouling.