What is it about?
The sequence of microbiological processes occurring during the decomposition of fresh and old organic wastes from landfills is analyzed using the developed dynamic models, which are verified on the basis of experimental data previously obtained in anaerobic and aerobic laboratory reactors. The models are based on the material balances of the heavy and light isotopes of carbon and hydrogen during the biodegradation of cellulosic waste as a relatively poorly degradable substrate. According to the models, under anaerobic conditions, dissolved carbon dioxide is a substrate for hydrogenotrophic methanogenesis, which leads to an increase in the isotope signature of carbon in carbon dioxide and its subsequent stabilization. After the introduction of aeration, methane production ceases, and from that time on, carbon dioxide remains only a product of cellulose and acetate oxidation, which causes a significant decrease in the isotopic signature of carbon in carbon dioxide. The dynamics of the deuterium content in the leachate water is described as a consequence of the rate of its entry into and exit from the two (upper and lower) compartments of the vertical reactors, as well as the rates of its consumption and formation during microbiological reactions. According to the models, in the anaerobic case, the water is first enriched with deuterium due to acidogenesis and syntrophic acetate oxidation and then diluted with deuterium depleted water, which is continuously fed to the top of the reactors. In the aerobic case, a similar dynamic is simulated.
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Why is it important?
Biodegradation of organic waste in a landfill may last for decades. In general, the quantitative description of complex, multi-stage and long-term processes of municipal solid waste (MSW) biodegradation in landfills represents a great challenge. The biodegradation process in the laboratory reactors with simulated wastes occurs on a much shorter timescale and in a controlled environment, which simplifies the mathematical description of the ongoing processes. For the development of a dynamic model of these processes, the isotopic data can be useful.
Perspectives
It is not always possible to monitor the dynamics of individual microorganisms in a complex system of interacting groups and types of microorganisms. Measurement of the dynamics of stable isotopes in chemicals involved in the biodegradation of the original organic pollutants entering the landfill, to a certain extent, provides such an opportunity. Using the dynamic models, we are able to describe the sequence of events that occur during the anaerobic and aerobic decomposition of samples taken from young and old landfills.
Lyudmila Lokshina
Water Problems Institute, Russian Academy of Sciences
Read the Original
This page is a summary of: Carbon and hydrogen dynamic isotope equations are used to describe the dominant processes of waste biodegradation: Effect of aeration in methanogenic phase of the landfill, Waste Management, July 2023, Elsevier,
DOI: 10.1016/j.wasman.2023.04.027.
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