Experiments on membrane filtration of effluent at wastewater treatment plants in the Netherlands

In the Netherlands interest in advanced treatment is increasing now that al most all wastewater treatment plants apply full biological treatment and nu trient removal. Membrane filtration of WWTP-effluent appears to be a very p romising method to remove suspended solids and, in addition, bacteria and v iruses. 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 mu m (ultrafiltration) and working in a semi dead-end mode, gave rather promising results. A flux of 90 l/m(2).h was achieved after optimizing the cleaning procedures (TMP 0.6 bar, recovery > 90%). Experiments with microf iltration (transverse flow module) based on the cross-flow principle were s uccessful only at high cross flow velocities (flux 100 l/m(2).h, TMP 0.5 ba r, recovery 80%). The ultrafiltrate showed an excellent quality with the absence of suspended solids and bacteria. Finally, low costs for energy (NLG 0.02/m(3) (1 NLG = 0.5 US$)) and chemicals (NLG 0.01/m(3)) were calculated. Further optimizat ion will facilitate the applicability of membrane filtration in the near fu ture. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved.