Co-disposal of bottom ash and municipal solid wastes: chemical, microbiological behaviours and stability in anaerobic conditions

The present study deals with the possible pre-treatment of municipal solid wastes (MSW) in anaerobic conditions and their co-disposal with bottom ash. In this objective, the effect of the addition of bottom ash on organic matter degradation was checked using different analyses. The obtained results showed a great reduction of organic matter in the presence of bottom ash (53% of a solid fraction is degraded instead of 18% for the control after 26 days of degradation). Consequently, methane production was more important for the leachate from a bioreactor mixed with the bottom ash, which reached 70.10 L/Kg in comparison with 50L/Kg for leachate from the control. The characterization of leachates by molecular tools revealed that the microorganisms responsible for organic matter degradation in anaerobic conditions belong to the Methanosarscina genera, and the methanogenesis reaction was acetate-dependent methanogenesis. To better understand the role of bottom ash in the acceleration of methanogenesis, molecular tools were used to identify the microorganisms in the bottom ash leachate after a leaching test. The obtained results showed the absence of microorganisms in the bottom ash leachate. The quantification by atomic absorption spectrophotometry (AAS) of dissolved iron, nickel, and cobalt in the bottom ash leachate after the leaching test, showed that the amounts of these metals were 57.30, 0.035, and 0.006mM, respectively. Moreover, the quantification of iron, nickel, and cobalt in leachates from the bioreactor mixed with bottom ash and from the control showed that these amounts reached 94.78mM, 0.49mM, and 0.01mM after 26 days of degradation, and 99.40mM, 0.08mM, and 0.009mM, respectively, after 138 days of degradation. Consequently, it can be suggested that bottom ash must be co-landfilled with municipal solid wastes at 9% as a suitable strategy, which will provide a more rapid chemical and microbiological stabilization of the municipal solid waste in landfills.