Modelling the dynamic of organic micropollutants during composting process of french organic wastes and chinese polluted soil

Abstract : With the increasing of people's living standards, more and more urban wastes are produced everyday with a huge quantity. The big amount of wastes have not only occupied precious land resource, influenced the industry seriously and agricultural production, but also introduced various pollutants, which will harm human's life and health. Compost processing can help urban wastes to be recycled by transforming the organic matter into fertilizer and be returned to nature. Also it can be used as a bioremediation method for the polluted soil. The mathematical model is an efficient tool for understanding and modifying the composting process, predicting the stability of compost products, and then assuring the harmfulness of pollutants for agriculture. Our objective in this study was to construct a model describing the dynamics of organic micro-pollutants during the composting and parameterize the model under the interface of MATLAB. This model should be used according to users' needs with 3 modules: organic carbon module, organic pollutants module and coupling module. In order to calibrate and validate our model, the datasets from 12 different waste mixtures and 2 different types of pollutants with different initial conditions were applied. On the other hand, for applying the composting technique in the field of bioremediation of contaminated soil, an in-vessel composting experiment was designed in which the organic urban wastes mixed with soil contaminated by PAHs were used as materials. We studied the dynamics of organic matter, organic micro-pollutants and the microbial populations. The conclusion showed that the concentration of PAHs could be decrease by 50-60% with the effects of organic matters and the accelerated microbial activities compared to bare soil. Furthermore, the successive microbial populations have been observed during the composting process. These experimental results could be well simulated by our model which indicates its capacity in the soil-composting system. However, we still came across some questions during my research. The simulations for soluble organic substrates were not accurate enough, due to the limits of the biochemical characterization of organic fractions. In our model, only the function of temperature has been considered as the environmental factor, more limiting factors such as moisture, oxygen, … need to be investigated in the further studies. The microbial diversity of each decomposition phase has been investigated in the experiment but was not added in the model because its impact on PAHs degradation is not clear enough. In order to answer all these questions, further researches needs to be done, although the study in the field of microbial flora has begun to be carried out.
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Yuan Zhang. Modelling the dynamic of organic micropollutants during composting process of french organic wastes and chinese polluted soil. Sociology. AgroParisTech, 2011. English. ⟨NNT : 2011AGPT0069⟩. ⟨pastel-00780958⟩

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