This study aimed to investigate treatability, selection of seed sludge and evaluation of carbon dioxide and methane productions from Carprolactam (C6H11NO, CPL) wastewater by using up-flow anaerobic sludge blanket (UASB) system at ambient temperature. Recycle ratio of the system was 1:1 and pH was maintained at 6.8-7.5. The reactor was operated for 60 days through 2 phases with different COD loading rate and hydraulic retention time (HRT). The results of this study showed that the highest removal efficiency of 93.6% was obtained at an influent COD of 4197 mg/l. The produced gas from UASB mainly contained CH4 and CO2. As the COD varied from 2897 to 11333mg/l, COD removal was in the range of 70.9-93.6%.The methane production rate was 0.18-0.31 liter CH4/g COD removal. The carbon dioxide production rate was 0.06-0.14 liter CO2/g COD removal. This study demonstrated the feasibility of UASB for CPL wastewater treatment
