In the Netherlands interest in advanced treatment is increasing now that almost all wastewater treatment plants apply full biological treatment and nutrient removal. Membrane filtration of WWTP-effluent appears to be a very promising method to remove suspended solids and, in addition, bacteria and viruses. Experiments with a pilot unit consisting of a dual media prefilter and a membrane filter, containing capillary membranes with a pore size of 0.01 μm (ultrafiltration) and working in a semi dead-end mode, gave rather promising results. A flux of 90 l/m2.h was achieved after optimizing the cleaning procedures (TMP 0.6 bar, recovery > 90%). Experiments with microfiltration (transverse flow module) based on the cross-flow principle were successful only at high cross flow velocities (flux 100 l/m2.h, TMP 0.5 bar, recovery 80%).

The ultrafiltrate showed an excellent quality with the absence of suspended solids and bacteria. Finally, low costs for energy (NLG 0.02/m3 (1 NLG = 0.5 US$)) and chemicals (NLG 0.01/m3) were calculated. Further optimization will facilitate the applicability of membrane filtration in the near future.