The granulation process was examined during carbon tetrachloride (CT) biodegradation in a laboratory scale upflow anaerobic sludge blanket (UASB) reactor operated at 35 degreesC for 220 days. Anaerobic, unacclimated sludge and glucose were used as seed and primary substrate, respectively. CT degrading granules developed after 48 days of start-up. They grew at an accelerated pace for 6.5 months and had a maximum diameter of 2.2 mm following the pre-granulation and maturation period. Maximum specific methanogenic activity (SMA) was 1.63 g chemical oxygen demand (COD) per g total suspended solid (TSS) per day while, maximum specific organic loading rate to achieve 96% of COD removal efficiency was determined to be 12.5 g COD per 1 per day. About 95% CT removal efficiencies were achieved when the reactor was operating at loading rates as high as 17.5 mg CT per 1 per day after 220 days of continuous operation. The methane content in the total biogas collected was between 50 and 68% depending to shock organic loadings. About 96% of the total COD removed, was converted to methane, 0.024 a of TSS was yielded for each gram of COD removed at the end of 230 days of operation period. Kinetic coefficients of k (maximum specific substrate utilization rate), K, (half velocity coefficient), were determined to be 2.4 x 10(-3) mg CT per mg TSS per day and 1.37 mg CT per 1, respectively, for CT biotransformation during granulation. Methanothrix (Methanosaeta) sp., Methanosarcina mazei, Methanobacterium sp., Methanobrevibacter sp., Syntrophobacter sp., Methanolobus vulcani and Acetobacter woodii were identified in UASB. (C) 2002 Elsevier Science Ltd. All rights reserved.