Seven comprehensive sampling campaigns were carried out after the 35-day operation of both the A2O processes to investigate the removal of water contaminants via collecting feed waters and their ef-fluents (volume of each sample = 50 mL): (i) feed, (ii) A2O-C effluent,(iii) A2O-B effluent. All the collected water samples were filtered using 0.45 μm mixed cellulose filter (Advantec, Tokyo, Japan) and kept in a refrigerator at 4 °C until further analyses. Two different approaches were applied to collect the activated sludge samples (volume of each sample 100 mL): (i) the activated sludge for measurements of the concentrations of mixed liquor suspended solids (MLSS) and mixed liquorvolatile suspended solids (MLVSS) daily obtained from the reactors, and (ii) the activated sludge for microbial community analyses collected from the anaerobic, anoxic, and aeration reactors after the removal efficiencies of nutrients remained completely stable (85–95%).