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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.

During this study, a mathematical model simulating piggery wastewater treatment was developed, with the objective of process optimisation. To achieve this, the effect of temperature and free ammonia concentration on the nitrification rate were experimentally studied using respirometry. The maximum growth rates obtained were higher for ammonium-oxidising biomass than for nitrite-oxidising biomass for the temperatures above 20 degrees C; values at 35 degrees C were equal to 1.9 and 1.35 day(-1), respectively. No inhibition of nitrification was observed for free ammonia concentrations up to 50 mgN/L. Using these data with others experimental data obtained from a pilot-scale reactor to treat piggery wastewater, a model based on a modified version of the ASM1 was developed and calibrated. In order to model the nitrite accumulation observed, the ASM1 model was extended with a two-step nitrification and denitrification including nitrite as intermediate. Finally, the produced model called PiWaT1 demonstrated a good fit with the experimental data. In addition to the temperature, oxygen concentration was identified as an important factor influencing the nitrite accumulation during nitrification. Even if some improvements of the model are still necessary, this model can already be used for process improvement.