The combination of the activated sludge process with reverse osmosis has attaint removal efficiencies of 98% for COD and BOD, at 0.15 gCODg−1 TS day−1, aeration intensity 800L h−1 and HRT 12 h; the reverse osmosis operated at 0.1–0.3 MPa with a flux of water of 1.0–2.78×10−6m3m−2 s−1