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Trace organic contaminants (TOCs) correspond to a broad range of molecules generated either directly or indirectly by human activity. Even though TOCs are found at low concentrations in the environment, they often accumulate by biomagnification and bioaccumulation into biological organisms and cause irreversible damages in biological systems through direct or indirect toxic effects such as endocrine disruption and tumour initiation. This manuscript presents the main findings of over fifteen years of research focusing on biological removal of various TOCs found in sewage sludge from urban treatment plants. A special focus of the research was made on microbial processes in complex anaerobic ecosystems. Four families of compounds mostly retrieved in urban plants were studied: the polycyclic aromatic hydrocarbons (PAHs), the polychlorobiphenyls (PCBs), the phthalic acid esters (PAEs), and the nonylphenol ethoxylates (NPEs). It was observed that the microbial capability for removing low amounts of TOCs required a long adaptation time and was often limited by the bioavailability of these compounds. In fact, the overall biodegradation resulted from the numerous interactions existing between the matrix (organic matter) and the microbial ecosystems according to the physico-chemical sorption properties of these compounds. Mechanistic aspects were also tackled in depth and specific models were developed for better understanding the network of interactions between TOCs, microorganisms, and organic matter. These findings could be extrapolated to other ecosystems such as soils and sediments. Finally, it was shown that microbial cometabolism was essential for TOC removal, and the concept of bioavailability was not only dependent on the nature, the level, and the sorption properties of TOCs but was also strongly dependent on the nature and the concentration of the sludge organic matter. Specific parameters were proposed for better evaluating the fate of TOCs in microbial anaerobic processes and technological solutions for efficient removal of these compounds were also proposed. removal of trace organic contaminants in sewage sludge: 15 years of experience. Pedosphere. 22(4): 508-517.

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Coffee is a highly productive agricultural product in the department of Tolima. The wet fermentation process of coffee generates about 80% of the waste, which is highly contaminated with organic matter that pollutes water sources, so anaerobic co-digestion techniques are implemented in coffee wastewater using Taiwan type biodigesters. According to the study of three biodigesters fed with coffee waste and animal manure, the aim is to show their potential application in coffee farms. These biodigesters generated a biogas production with CH4 concentrations between 49.1% ± 4.6 and 58.1% ± 2.4 in volume, in addition to the benefit of the biol used as fertilizer in the crops. The biogas produced can be used for cooking and can save around USD 40.17 in natural gas. Therefore, the biodigester is a potential tool to mitigate the harmful effects of coffee cultivation on the surrounding ecosystem and can project coffee production in a sustainable direction.