Greywater is an excellent resource for service water in intra-urban reuse. By substituting fresh water with appropriately treated greywater, it is possible to save 30–50% of fresh water. In this paper, an up-flow pilot biological aerated filter (BAF) is tested for the treatment of synthetic greywater and the design parameters are determined. An organic load of 8 kg COD/(m3 d) allows to achieving a good effluent quality with regard to COD, suspended solids, and anionic surfactants. By reducing the organic load to 5 kg COD/(m3 d) full nitrification is achieved as well. A process set-up for a full-scale BAF greywater treatment plant is proposed and dimensioned using the parameters from the pilot plant tests. Here, the required specific volume is approx. 3 L/C for the reactor and 16 L/C for the storage tanks. This feature make the BAF a compact process which can be successfully integrated in intra-urban water reuse schemes.