To optimise the intermittent aeration process for piggery wastewater, the Activated Sludge Model No. 1 needs to be calibrated and adapted to this specific effluent. By combining aerobic and anoxic respirometric tests, biodegradation kinetics of organic fractions in piggery wastewater could be studied. Modeling of the respirometric curves proved that the simplified hydrolysis model was sufficient for piggery wastewater treatment simulation. The hydrolysis constant (K(H)) and heterotrophic sludge yield (Y(H)) were determined at temperature and pH in the ranges 10-40 degrees C and 7-9, respectively. The constants were slightly influenced by the temperature but not significantly affected by the pH, with average values of 3 d(-1) for K(H) and 0.60 for Y(H). The anoxic respirometric tests revealed that the experimental ASM1 anoxic correction factor (eta(g)) was higher than one. This could be explained by the fact that the anoxic and the aerobic heterotrophic sludge yields were probably different. By fixing a value of 0.8 for eta(g), the anoxic sludge yield (Y(HD)) could be calculated at 0.53. A modified version of ASM1 for substrate biodegradation in piggery wastewater intermittent aeration process was proposed, including the separation between the anoxic and the aerobic sludge yields and a simplified hydrolysis kinetic.