Étude expérimentale et modélisation de la digestion anaérobie des matières organiques résiduelles dans des conditions hyperthermophiles

Abstract

The effect of temperature on acid formation during fermentation of municipal solid waste MSW is investigated firstly (acidogenic step). The performance of six batch anaerobic reactors is evaluated using three different inoculum sourcs mesophilic anaerobic sludge from a biosolids digester of a municipal wastewater treatment plant (HS); thermophilic anaerobic sludge treating flour residues from an agro-food industry (AD) and an anaerobic hyperthermophilic sludge treating microalgae (HT). The reactors are brought to their temperature of origin and at 70°C. The results show that a one day latent phase is observed at 35°C and 55°C unlike at 70°C where solubilisation begins from day one, Moreover, The hydrolysis of the organic matter reaches an efficiency of 40% at 70°C., in the presence of inoculum. The tracking of the acidogenic phase shows a variation in the composition of the organic acids at each temperature. Acetic acid is found in high concentrations at 35°C (10 000 mg COD /L), butyric acid is produced at 35°C and 55°C (3800 mg COD / L and 5000 mg COD / L respectively). In addition, a large proportion of lactic acid is observed only at 70°C. (7000 mg COD / L) at a pH of 5 followed by the formation of ethanol (4000 mg COD / L) and finally the acid (700 mg COD / L) at a pH of 6. On the other hand, the maximum fermentation rate is three times higher at 70°C than at 55°C (22800 mg COD / LJ compared to 6800 mg COD / LJ). Secondly, a Hyperthermophilic Acidogenesis Model (HAM) is developed to predict the organic compounds of the fermentation of food residues discontinuously at 70°C. The model parameters are estimated using experimental data obtained from the anaerobic batch reactor. The model is validated using data from a discontinuous reactor where the organic loading rate is increased. The model is then tested using data from a batch reactor at 35°C. The experimental results show good agreement with model prediction, indicating that the model can accurately simulate the generation of organic acids at 70°C and 35°C. Finally, the HAM model is coupled to the Anaerobic Digestion Model N1 model (ADM1) to simulate the production of CH4 from hyperthromophilic or mesophilic acidogenesis, the results give a flow rate equal to 1600 Nm3 /J at 70°C and 1850 Nm3 /J at 35°C.

Date	6 Oct 2017
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Robert Hausler (Supervisor)