1,721,017 research outputs found
Effects of separate collection efficiency on the costs of the MSW management system. A case study
No full textIntermittent aeration of landfill simulation bioreactors: Effects on emissions and microbial community
Full text linkLandfill simulation experiments were run at lab-scale to compare the effects of intermittent and continuous aeration on the evolution of leachate composition and biogas production. The experiments were carried out using six reactors; two of them under continuous aeration, two under intermitted aeration and two anaerobic as a control. Different aeration regimes produced different effects on reactors. As expected, carbon discharge via biogas was higher in reactors under continuous aeration than under intermittent aeration. The evolution of leachate quality was affected by the aeration regimes; however, at test end very similar concentration were ascertained for relevant leachate parameters in all aerated reactors. A comprehensive description of the aerobic and anaerobic landfill microbiome is provided, using a metagenomic approach focused on the microbial genome reconstruction. A time course investigation evidenced the modification of the microbiome and revealed taxa and specific microbes more strictly connected to the environmental parameters of the reactors. Methanoculleus, Syntrophomonas and Parabacteroides were identified as the genera more strictly connected to biogas production, while numerous species belonging to Thiomonas, Nitrosomonas, Xanthomonadaceae, Myxococcales and Alcaligenaceae were found to be connected with NH4+ oxidation
Environmental Performance of Semi-Aerobic Landfill by Means of Life Cycle Assessment Modeling
Full text linkThe potential impacts and the environmental performance of the semi-aerobic landfill technology were assessed through the Life Cycle Assessment (LCA) methodology. Project data that referred to a hypothetical Italian plant design were used and ISO 14040/14044 standards were applied. All the life cycle phases were considered, from landfill construction to filling, aftercare, closure and conversion for future use. All the landfill processes and the inflow of materials, energy and rainwater, and the outflow of biogas and leachate, were included in the system boundaries. The results show that the overall environmental impacts associated to semi-aerobic landfill are primarily due to the filling and aftercare phases, but the impacts related to construction and closure phases are not negligible. The contribution analysis underlines the processes with major responsibility within the environmental profile, while the normalization of results demonstrates what are the environmental categories on which the landfill impacts fall most. Important lessons emerging from this research can support practitioners and scientists in optimizing semi-aerobic landfill design and management
ENVIRONMENTAL PROFILE OF ANAEROBIC AND SEMI-AEROBIC LANDFILLS WITHIN SUSTAINABLE WASTE MANAGEMENT: AN OVERVIEW
No full textThe new perspective of circular economy accelerates the efforts to increase reuse and recycling of products and reduce the need of resources. Although the quantity of waste reaching the end-of-life has decreased, landfills can't be eliminated from the waste management systems (WMS) since the current treatment processes still produce unrecyclable materials. Anaerobic landfills have great environmental impacts due to the long-term emissions, therefore, to reach a more sustainable waste management less impacting alternatives are being implemented. Semi aerobic landfills can reduce the environmental burdens by enhancing waste stabilization with natural air flow inside the landfill body through the leachate collection pipes. The presence of aerobic areas implies biogas with less methane and leachate with lower pollutant concentrations. The research goal is to deepen the evidence that the semi-aerobic landfills are environmentally preferable to traditional anaerobic landfills, by considering the scientific information published in international peer-reviewed journals from 2000 to 2022. To obtain comprehensive answers to the research question, papers using the life cycle assessment (LCA) methodology are included in the review, with the aim of understanding what the environmental profiles of traditional and semi-aerobic landfill are when all life cycle phases are considered. The results clarify what the main contributions to environmental impacts of these two types of landfills are. The review only partially demonstrates the environmental convenience of semi-aerobic landfill. Instead, it reveals a lack of papers analyzing the comparison between different landfill technologies, suggesting new research perspectives to optimize the sustainability of final treatment solutions in WMS
Denitrification of low C/N landfill leachate in lab-scale landfill simulation bioreactors
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Forensic assessment of HP14 classification of waste: evaluation of two standards for preparing water extracts from solid waste to be tested in aquatic bioassays
No full textMisclassification of waste hazardousness could lead waste operators to be charged of illegal trafficking. Among different aspects characterizing waste hazardousness, Ecotoxicity is acknowledged as the most frequent Hazard Property classifying wastes as hazardous. In this context, a conventional, scientifically based and agreed-upon procedure for ecotoxicity assessment can help forensic activities to verify the conditions of possibly occurred illegal trafficking of waste. Currently, European Regulation declares a waste ecotoxic according to a calculation method based on its chemical composition. Whether outcomes from calculation method would result in an unrealistic assessment, results from ecotoxicity testing can be used for waste hazardousness classification. However, each Member State is allowed to establish a specific experimental procedure, thus resulting in a fragmented legal framework regulating ecotoxicological testing. This study gives a description of the two main approaches followed by European Member States in regulating ecotoxicity assessment of wastes. This work reports how both investigated approaches address three main methodological issues: which sample preparation standard must be carried out, which test battery should be performed and which concentration limits will trigger hazard classification. Further, a comparison is presented between two different standardized protocols (GHS Annex X and EN 14735) for leaching tests of solid wastes, performed on Automotive Shredder Residues (ASR) samples to obtain water extracts to be further tested in aquatic bioassays. EN 14735 resulted more conventional for routine waste classification efforts, both in terms of achieved sample representativeness and time needed to derive test portions. Then, results from chemical physical analyses on derived water extracts suggested that the lower Liquid-to-Solid ratio required by EN 14735 could have played a key role in determining the resulting higher contaminant concentrations. For this reason, it could also be considered as the most conservative approach for further testing on aquatic organisms. However, this assumption must be further validated by further research on different waste streams, speciation mechanisms of dissolved contaminants, the role of pH adjustment of the test portion and the influence of specific dilution media
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