2.5. Analytical methods
pH, VSS and TS were analyzed according to the Standard
methods [39]. HACH programs, 430 COD LR (low range) and 435
COD HR (high range/high plus) was used for COD analysis. A gas
chromatograph (GC 8500 PerkinElmer) equipped with a thermal
conductivity detector and a 2 m stainless-steel SS350A column
packed with a molecular sieve (80/100 mesh) was used to
determined the fraction of H2 in biogas using nitrogen as a carrier
gas at a flow rate of 25 ml/min. The operating temperatures of the
detector, injection port and oven were 150 8C, 100 8C, and 80 8C
respectively. The alcohol and volatile fatty acid (VFA) contents of
filtered samples (0.2 mm) were analyzed on the GC using a flame
ionization detector equipped with a Nukol capillary column. The
dry weight of immobilized cell in immobilized beads was assessed
by measuring the difference in dry weight between the biomassloaded
beads and the beads alone.