ABSTRACT
Different micronutrients are essential for bacterial fermentative metabolism. In particular, some metallic ions, like iron, are able to affect the biological H2production. In this study, batch tests were carried out in stirred reactors to investigate the effects of Fe²âº concentration on fermentative H2production from two different organic fractions of waste: source-separated organic waste (OW) from a composting plant including organic fraction of municipal solid waste and food waste (FW) from a refectory. Iron supplementation at 1000 mg/L caused twofold increment in the cumulative H2production from OW (922 mL) compared with the control (without iron doping). The highest H2production (1736 mL) from FW occurred when Fe²âº concentration was equal to 50 mg/L. In addition, the process production from OW was modelled through the modified Gompertz equation. For FW, a translated Gompertz equation was used by the authors, because the initial lag-time for H2production from FW was almost negligible.
Subject(s)
Bioreactors , Hydrogen/metabolism , Iron , Anaerobiosis , Carbon Dioxide/metabolism , Fatty Acids, Volatile/metabolism , Fermentation , Methane/metabolism , Solid WasteABSTRACT
Existing models for H2 production are capable of predicting digester failure caused by a specific disturbance. However, they are based on studies using simple sugars, while it is known that H2 production and fermentation kinetics vary with the composition and characteristics of the substrate used. Because the behaviour of biological processes may differ significantly when the digesting material is a complex matrix, such as organic waste, the aim of this study was to develop and calibrate a mathematical model for the prediction of hydrogen production on the basis of the results obtained from a laboratory scale experimental study using source-selected organic waste. The calibration was carried out for the most important kinetic parameters in mesophilic anaerobic digestion processes and also served as a sensitivity analysis for the influence of both the specific growth rate (µmax and the half velocity constant (k(s)), both of which are strongly dependant on the substrate used. High values of µmax led to a shorter lag-time and to an overestimate of the cumulative final H2 production relative to the experimentally measured production. Additionally, high values of ks associated with amino acid and sugar fermentation corresponded to a lower rate of substrate consumption and to a greater lag-time for growth of hydrogen-producing microorganisms. In this case, a lower final H2 production was predicted than that which was experimentally observed. Because the model development and calibration provided useful information concerning the role of the kinetic constants in the analysis of a fermentative H2 production process from organic wastes, they may also represent a good foundation for the analysis of fermentative H2 production from organic waste for pilot and full-scale applications.
Subject(s)
Hydrogen/metabolism , Models, Theoretical , Waste Management/methods , Amino Acids/metabolism , Anaerobiosis , Biofuels , Calibration , Fermentation , Kinetics , Soil , Waste Management/instrumentationABSTRACT
Drugs and their metabolites, once reached and spread over the soil and the aquatic environment, then exert their action on the living organisms belonging to such ecosystems. The present work provides a brief view on the main scientific experiences regarding the problem of the presence of drugs and/or their residues in the environment and of the related effects on the biokenosis and the human community.
