Effects of wastewater effluent organic materials on fouling in ultrafiltration

The objective was to determine the effects of wastewater effluent organic materials (EfOM) on fouling of ultrafilters (100kDa polyethersulfone (PES)). EfOM constituents were sequentially removed, first by removing particles down to the approximate ultrafilter pore size and then by removing dissolved EfOM based on functionality. Particles and colloids >20nm accounted for 19% of total organic carbon (TOC), including 96% of EfOM >100kDa. Removal of particles and colloids resulted in increased fouling, attributed to increased contact of dissolved EfOM with the membrane. Hydrophobic and hydrophilic (HPO/HPI) acids were 22% of total EfOM, and accounted for nearly all of the fouling. HPO/HPI base/neutrals were 59% of EfOM, but did not cause any significant fouling. Although HPO/HPI base/neutrals did not cause any fouling, they were the dominant EfOM constituent at the surface of fouled and then hydraulically cleaned membranes, as measured by attenuated reflectance infrared spectroscopy. Since the filtration runs were short, the effects of HPO/HPI base/neutrals on long-term fouling should be further investigated, but these results cast doubt on the presumption that organic materials that are identified during membrane autopsies are necessarily a primary cause of fouling. These results also indicate that wastewater EfOM should be treated to remove HPO/HPI acids prior to membrane filtration.