Modelling Sewage Sludge Composting in WWTP: Influence of Meteorological Conditions

This work presents the 2D modelling of a fermenting step during composting of a sewage sludge/bark mixture at the Aureilhan (France) WWTP. For this study the temporal evolution of the temperature has been studied because it is the composting key parameter, especially for achieving the compost sanitization. Thus, the modelling results have been compared with experimental results. Fermenting windrows are being subject to weather conditions, we took into account the temperature and humidity of the outside air in the model as boundary conditions. Results indicated that the model is consistent with windrow A but differed from the experimental results for windrow B. The weather conditions had a strong impact on the temperature profile during fermentation, especially the maximum temperature. Indeed, the maximum temperatures did not exceed 35°C for windrow A (winter) while they were around 50°C for windrow B (summer). On the other hand, the temperature rise in the windrows was faster for the experimental measurements than for the modelled results. Finally, the experimental and modelling results showed that the warmest temperatures were towards the center of the windrow. This trend is consistent with the suction aeration system.