Abstract A system with the combination of upflow anaerobic sludge blanket (UASB) reactor and constructed wetlands (CWLs) has not yet been applied for cleaning river water polluted by sewage and swine wastewaters. In this study, a pilot system with an UASB reactor (effective working volume 4.0 m3) combined with two CWL reactors (effective working volumes 4.8 and 5.4 m3 for CWL-1 and CWL-2, respectively) was used to test the feasibility for treating wastewater sampled from the Wu-Luo River. The river is located in Ping-Tong County of southern Taiwan and has long been polluted by untreated domestic and partially treated swine wastewaters and is among the most polluted rivers in Taiwan. A control system without the UASB reactor and with the CWL-1 and CWL-2 was also tested in parallel to the test system. In the test system, the UASB reactor was seeded with an anaerobic sludge for sewage treatment and CWL-1 and CWL-2 of both the test and control systems were planted with emergent macrophyte (Typha angustifolia L.) and floating macrophyte (Pistia stratiotes L.), respectively. In general, it requires hydraulic retention times (HRT) of 1-5 days for polluted waters in CWLs to obtain clarified ones. In the present study, HRT of the test water in the system was reduced from around 34 to 11 hours to examine the clarification effect. Results indicated that the influent water has the following average qualities (unit in mg/L): total COD (CODt) 61, BOD 14, suspended solids (SS) 156, total-N 24, ammonia-N 12, nitrate-N 3.9, nitrite-N 0.92, and total-P (TP) 41. Results also indicate with a total HRT of 11.3 hrs, the test system (UASB-CWL1-CML2) could achieve average removals of 62% CODt, 56% BOD, 75% SS, 37% TN, 44% ammonia-N, 54% nitrate-N, 47% nitrite-N, and 61% TP from the influent water. The effluent water has the following average qualities (unit in mg/L):CODt 19, BOD 6.1, SS 15, TN 15, ammonia-N 7.5, nitrate-N 1.8, nitrite-N 0.49, and TP 1.7. The study indicates that the UASB could act as a preliminary device for sedimentation of most of the influent suspended solids and hence preventing the accumulation of sludge in the following CWLs.