CHEMICAL-COMPOSITION AND KINETIC-PROPERTIES OF GRANULAR METHANOGENIC SLUDGE GROWN ON PROPIONATE

The chemical composition and kinetic properties of propionate-grown methanogenic granules were analyzed as a function of the diameter of the granules (range: 0.1-3.0 mm in diameter). No significant variation in the chemical composition of the granules was observed- All granules contained large amounts of ash (between 53 and 59%). Extracellular polymers extracted from the granules were equivalent to 86-99 mg/g mixed-liquor volatile suspended solids (MLVSS), in which proteins, carbohydrates, and nucleic acids were the main constituents. The apparent substrate saturation constant (K(s)) value for propionate utilization was clearly influenced by the diameter of granules, although the maximum rate of propionate utilization was virtually constant, irrespective of the diameter. This indicates that the influence of mass transfer limitation was more pronounced in larger granules, especially at lower propionate concentrations.