Activity
A specific activity test is used to determine the performance of different specific physiological groups involved in anaerobic digestion.36J44 The specific metabolic activity of granular sludge is measured on defined substrates in batch tests. Specific activity is directly proportional to the relative amount of viable bacteria biomass of the trophic group corresponding to the defined substrate used in the batch activity test.36 High methanogenic activity is one of the characteristics of granular sludge and the specific methanogenic activity (SMA) of granules is typically between 0.5 and 2 g COD (chemical oxygen demand) CH4/g VSS (volatile suspended solid)/day (10-42 mmol CH4/g VVS/day (Table 11). However,the SMA of thermophilic granules has been observed up to 7.1 g COD/g VSS/day (148 mmol CH4/g VSS/day) (Table 11). The specific methanogenic activity of the biomass depends on the energy and carbon source which the granules were grown on. The maximum values are obtained when the test substrate is identical to the