Direct ultrafiltration of municipal wastewater: comparison between filtration of raw sewage and primary clarifier effluent

The increasing water demand encourages the development of non-conventional techniques for wastewater reclamation and reuse. In the treatment of municipal wastewater, direct membrane filtration is attractive because of the potential to produce high-quality water, enriched with valuable nutrients and organics, in one single step. This paper presents basic research into direct membrane filtration of municipal wastewater, focusing on filterability and fouling control. Primary clarifier effluent and raw sewage, pre-filtered on a 0.56 mm sieve, were used in batch ultrafiltration experiments at constant TMP. Differences in filterability of the two feedwaters with TMP and crossflow velocity were explained as depending on the formation of a cake layer with different characteristics. Continuous filtration of both waters seems possible thanks to fouling reversibility with backflush.