The treatment of municipal-type synthetic wastewater was carried out using a three stages net-like rotating biological contactor (NRBC). The results indicated that, compared with conventional rotating biological contactor (RBC), NRBC have several advantages, such as quick start-up, high biomass concentration and can handle high organic loading rates. The COD and total nitrogen removal rates achieved were 78.8-89.7% and 40.2-61.4%, respectively, in aerobic treatment of low COD municipal-type wastewater at hydraulic retention times (HRT) from 5 to 9 h. The COD removal rate achieved 80-95% when organic loading varied between 16 and 40 gCOD/m(2) d. A large amount of nematodes were found in the NRBC system, which made the NRBC system produce relatively low amounts of waste sludge, due to their grazing. (c) 2006 Elsevier Ltd. All rights reserved.