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Carleton University (2007)

Effect of salinity on biodegradation of MSW in bioreactor landfills

Al-Kaabi, Salem

Titre : Effect of salinity on biodegradation of MSW in bioreactor landfills

Auteur : Al-Kaabi, Salem

Université de soutenance : Carleton University

Grade : Doctor of Philosophy (Ph.D.) 2007.

Bioreactor landfills require sufficient moisture to optimize the biodegradation processes and methane generation. In arid regions, this is problematic given the lack of fresh water supplies. Saline water can be used but may inhibit the biodegradation of the municipal solid waste (MSW) in landfills. Sludge may be used to enhance the biodegradation of MSW under saline conditions. For this research, two groups of laboratory scale bioreactor cells were used to study the impact of saline water and sludge addition on the biodegradation of MSW in bioreactor landfills. The first group (R1-R4) operated without sludge addition. The second group (R5-R8) operated with addition of sludge. The salt concentrations in the two groups were 0%, 0.5%, 1%, and 3% (w/v) respectively. All bioreactors were operated at neutral pH levels with leachate recycle. The methane yield was 70.6, 61.7 and 47.5 L/kg dry waste for bioreactors R1, R2 and R4, respectively ; and 84.7, 78.7, 72.6 and 59.0 L/kg dry waste for bioreactors R5, R6, R7 and R8, respectively. The high salt content (3%) inhibited the MSW biodegradation as evidenced by the methane yield, the percentage peak reduction in leachate concentration and the settlement that occurred during the study. Sludge addition was able to improve the methane yield at all salt contents. A mathematical model was developed to simulate the biodegradation of the MSW in bioreactor landfills operating under saline conditions and to predict the leachate strength (aqueous organic acid and volatile fatty acid (VFA)), and the volume of landfill gas (CH4 and CO2) produced. Sensitivity analysis indicated that the hydrolysis rate constant, methanogenic parameters ([mu]M, kdM, KSM), and initial concentration of methanogenic biomass had a significant impact on peaks of the VFA and daily methane produced, as well as the time required to reach them. The model has been calibrated by comparing the simulation results to the experimental 1D bioreactor measurements. The results of methane production showed good agreement between the model and experimental data. Both the model parameters and the salt inhibition constants (KI and m) were determined from these simulations

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