Anaerobic biodegradation of an organic by-products leachate by interaction with different mine tailings
Markewitz, Karine; Lefebvre, Guy; Cabral, Alexandre; Panarotto, Cláudia Teixeira
Abstract: Deinking by-products from paper recycling has been used as cover material on acid-producing tailings. Due to remaining cellulose, anaerobic degradation leads to the production of an organic-rich leachate, which may percolate through the tailings. This study aims at describing the influence of the tailings’ characteristics on the attenuation of organic matter in leachate and at discussing the degradation mechanisms. To this end, leachate was mixed with different types of tailings, includ ing three unoxidized tailings with varying acid generation potentials and one tailing in three states of oxidation. Regularly, selected biochemical parameters were analyzed to access the evolution of organic components. The results show that when deinking by-products leachate was placed in contact with tailings, phase and acid-base balance reactions took place in the beginning. Subsequently, oxidationreduction reactions dominated the chemistry of the system. The type, the constituents and the state of oxid ation of the mine tailings condition the mechanisms of biodegradation of organic components. Methanogenesis was predominant in the control sample (pure organic leachate) but was absent in all leachate-tailings mixes. No biodegradation was observed in the liquid phase for oxidized tailings and the organic concentration remained constant for unoxidized tailings, independently of the acid-generation potential. The biodegradation efficiency was optimal when the leachate was in contact with a mixture of oxidized and unoxidized tailings due to sulfate-reduction.
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