Ever rising costs of water supply due to tax-rules, more stringent quality requirements and the concern of the continuing depletion of ground water sources give strong impetus for new innovative technologies. These technologies must be reliable and economically attractive. Recently, the membrane manufacturer X-Flow, a full subsidiary of the Norit Group, has developed a novel X-inch dead-end ultrafiltration technology. This technology has proven to be a viable alternative for the economical production of water in a number of applications e.g. reuse of back-wash water of mediafiltration and filtration of surface water (lakes, rivers, canals). A number of full size plants has been realized or is under construction at this moment. Norit Membrane Technology has started experiments in 1997 in which dead-end ultrafiltration, using the E-inch technology, was used in the reuse of Waste Water Treatment Plant (WWTP) effluent. Experiments have been carried out with and without pretreatment. Pilot scale installations (1-6 m(3)h(-1)) were used for the experiments. Preliminary results show a very good permeate quality with an MFI of 0.5 to 0.6, making this technology especially suitable as reverse osmosis pre-treatment. Permeate fluxes of up to 80 1m(-2)h(-1) for longer periods of time were measured and cleaning of the membranes posed no significant problems. Pretreated effluent (mechanical as well as chemical) showed better results than untreated effluent on some locations, but whether pretreatment is attractive is still subject to discussion. In the paper qualitative and quantitative results of experiments on several locations will be presented. An indication of operational costs will be given.