Xiao-Feng Dai, Yanru Bai, Shu-Juan Lian*, Xue-Jiao Qi, Kai Feng, Shan-Fei Fu* and Rong-Bo Guo,
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引用次数: 0
Abstract
Ammonia inhibition often occurs during anaerobic digestion (AD) of the protein-rich substrate. Iron-containing substances were proved to be efficient in alleviating the ammonia stress. However, the mechanisms behind, especially the distinct impacts of different forms of iron materials, are not fully revealed. Here, the alleviating performances of FeCl3 and Fe3O4 on AD systems under ammonia stress were investigated. Moreover, the mechanisms behind these were revealed and compared at the transcriptional level. Results showed that FeCl3 and Fe3O4 additions with an equal amount of iron element content (1.29 mM) led to the increased cumulative biogas and methane yields under an ammonia concentration of 3 g/L. Furthermore, the addition of iron-containing substances alleviated the accumulation of volatile fatty acids (VFAs) and extracellular polymeric substances (soluble carbohydrates and protein) caused by ammonia stress, which also had an obvious positive effect on the electron transfer capability. Microbial analysis demonstrated that the microbes (e.g., orders Methanosarcinales, Clostridiales, and Syntrophobacterales) associated with direct interspecies electron transfer (DIET), syntrophic acetate oxidization, and degradation of organic compounds were enriched. Metatranscriptomic analysis showed that ammonia inhibited the AD process by disrupting cellular redox homeostasis, infecting the ATPase activity, affecting cellular energy supply, inhibiting methane-producing enzyme activity, and suppressing the expression of cell conductive structure genes. Meanwhile, the addition of FeCl3 and Fe3O4 enhanced the cellular basal metabolism and energy supply, as well as microbial electron transfer and enzymic activities on methanogenesis. Metatranscriptomic analysis indicated that the addition of free iron species (FeCl3) can relieve the ammonia stress on syntrophic propionate and acetate oxidizing bacteria, enhance DIET by stimulating the synthesis of c-type cytochrome, and thus promote methane production. Meanwhile, Fe3O4 may promote methane production by stimulating the expression of related genes and facilitating electron transfer in the AD system as a capacitor. Overall, the results demonstrated that ferric chloride and magnetite can alleviate the ammonia inhibition in the AD process of high-nitrogen waste through different mechanisms.
期刊介绍:
ACS ES&T Engineering publishes impactful research and review articles across all realms of environmental technology and engineering, employing a rigorous peer-review process. As a specialized journal, it aims to provide an international platform for research and innovation, inviting contributions on materials technologies, processes, data analytics, and engineering systems that can effectively manage, protect, and remediate air, water, and soil quality, as well as treat wastes and recover resources.
The journal encourages research that supports informed decision-making within complex engineered systems and is grounded in mechanistic science and analytics, describing intricate environmental engineering systems. It considers papers presenting novel advancements, spanning from laboratory discovery to field-based application. However, case or demonstration studies lacking significant scientific advancements and technological innovations are not within its scope.
Contributions containing experimental and/or theoretical methods, rooted in engineering principles and integrated with knowledge from other disciplines, are welcomed.