Also combined processes (anaerobic–aerobic) such asan UAF operating at 24 h of HRT and at 11 kg COD m−3day−1of OLR with a sequencing batch reactor (SBR) with 9 h foraeration time, can reach COD removal efficiencies around95% (Borja, 1995; López-López et al., 2010). The combina-tion of the activated sludge process with reverse osmosishas attaint removal efficiencies of 98% for COD and BOD, at0.15 g COD g−1TS day−1, aeration intensity 800 L h−1and HRT12 h; the reverse osmosis operated at 0.1–0.3 MPa with a fluxof water of 1.0–2.78 × 10−6m3m−2s−1(Bohdziewicz and Sroka,2006).