ROLE OF SUBSTRATE CONCENTRATION IN PARTICLE-SIZE DISTRIBUTION OF METHANOGENIC ANTIGRANULOCYTES SLUDGE IN UASB REACTORS

The effect of influent substrate concentration on particle size distribution of methanogenic granular sludge was studied in laboratory-scale UASB reactors fed with propionate as sole carbon and energy source. A mean biomass increase of 60.9 mg VSS/d and 0.95 ml sludge/d was measured in five UASB reactors operated in parallel mode, resulting in a mean SVI of 7.8 ml sludge/g dry wt. Particle size distributions were measured by a gravimetric method and by direct image analysis. Median granule diameter increased with increasing influent substrate concentration and decreased with decreasing concentration. Increasing the influent concentration led to an increase of the methanogenic activity of the granules with propionate or acetate as test substrate.