Factors Influencing Formation and Maintenance of Granules in Anaerobic Sludge Blanket Reactors (UASBR)

Four, 20 L UASB reactors were operated under different hydrodynamic regimes continuously for more than 150 days. The influence of superficial liquid upflow velocities over the range 0.2 5 to 1.5 m h⁻¹, on granule activity and characteristics was investigated, maintaining constant temperature (35°C), and volumetric loading rate (6.2 g COD L⁻¹ day⁻¹). Reactor pH, COD removal, VFA concentration, bed height and gas production were continuously monitored and evaluated. It was found that hydrodynamic conditions can influence the size of granules, and their settling characteristics. Low upflow velocities (0.25 and 0.5 m h⁻¹), are favourable for granule growth and accumulation. At high upflow velocities (1.0 and 1.5 m h⁻¹), no sludge accumulation and disintegration of larger granules were observed.