Anaerobic degradation of formaldehyde containing wastewater was studied in an upflow anaerobic fixed film (UAFB) reactor. The reactor was operated at 0.18-3.61 kg COD m(-3) d(-1) corresponding to formaldehyde concentration of 65-92 mg L-1. COD and formaldehyde removal were found to be 92-24% and 99-41%, respectively. The efficiency of the reactor was investigated at different hydraulic retention time of 10-24 h. Kinetic models were applied to the data obtained from the studies in the anaerobic reactor. Second order and Stover-Kincannon models were best fitted to the data on UAFB reactor. The second order substrate removal rate (K-2(s)) was found to be 3.2 h(-1), U-max and K-B value constants for Stover-Kincannon models were found to be 3.4 gd(-1) and 4.6 gd(-1), respectively. (C) 2008 Published by Elsevier B.V.