1,721,037 research outputs found
Hydrogen production dynamic during cheese whey Dark Fermentation: New insights from modelization
No full textThe modelization of non methanogenic anaerobic environments can be particularly challenging owing to the variability of the metabolic products. In particular, both hydrogen production and consumption take place at the same time due to the simultaneous occurrence of Dark Fermentation (DF) and homoacetogenis. The goal of this study is to investigate the kinetic and thermodynamic aspects of the biochemical pathways involved in the fermentation of ultrafiltered cheese whey; to this aim, a continuous digester was operated under three different Hydraulic Retention Times (6, 9 and 12 h) and fixed pH (5.5). A mathematical model, based on a variable stoichiometry approach, was implemented and calibrated; the proposed model allowed the determination of the parameters governing the most relevant pathways, namely homoacetogenesis and butyric and ethanol-type DF. A special focus was given to the quantification of the hydrogen turnover rate; the model proved to be an effective tool, in addition to widely adopted techniques such as microbial and isotopic analysis, for obtaining a deeper comprehension of the crucial aspects governing the non-methanogenic process
Development of statistical predictive models for estimating the methane yield of Italian municipal sludges from chemical composition: a preliminary study
No full textThe biochemical methane potential (BMP) of primary and biological sludge varies in a wide range, mostly depending on location, sewer characteristics, wastewater treatment plant design and operating conditions. BMP tests are useful to verify the performance of a full scale digester, but they are not yet a common procedure in the operation of most Italian facilities because of cost and test duration. Changes in the composition of sewage sludge can lead to a high variation of biogas production. Aimed at developing BMP predictive models based on low cost and fast analyses, this study investigated the chemical composition of 20 sludge samples by means of principal component and multiple linear regression analyses. Three preliminary predictive models were developed based on soluble organic nitrogen, volatile solids, carbohydrates, proteins, lipids and an operational parameter, the sludge retention time: the explained variance and the standard errors of prediction of BMP are in the range 77-81% and 21-34 NmLCH4·gVS-1, respectively. Models were evaluated on five additional samples: errors ranged 2-15% for four samples and about 54% for one sample, collected from a peculiar facility. Further data and variables describing the operation mode of the waterline would certainly improve the reliability and robustness of the models
Inhibition on anammox bacteria upon exposure to digestates from biogas plants treating the organic fraction of municipal solid waste and the role of conductivity
No full textThe aim of this research was to evaluate the applicability of the anammox process for removing nitrogen from the supernatant originating from the anaerobic digestion of the organic fraction of municipal solid waste (OFMSW). The short term inhibitory potential of this concentrated wastewater was evaluated by means of batch tests in terms of maximum specific anammox activity reduction. A total of 20 real wastewater samples were tested originating from 4 different full scale anaerobic digestion plants treating OFMSW. Activity reduction between 73% and 89% was observed in the presence of undiluted real wastewaters. The specific activity remained stable for 6–7 days after the initial reduction, thus suggesting its treatability even without dilution. The inhibitory effect of both the real and synthetic saline media tested could be modelled as a function of conductivity. IC50 of 6.1 mS/cm was obtained for exposure to the tested liquid fraction of biowaste digestate
Extracellular polymeric substances extraction and recovery from anammox granules: Evaluation of methods and protocol development
No full textSelection of appropriate extraction methods of extracellular polymeric substances (EPSs)is crucial, affecting the yield, composition and the properties of EPSs. However, there is still a lack of standard methods for EPS extraction. In this study, seven methods were compared to extract EPS from anaerobic ammonium oxidation (anammox)granules, and the effectiveness and cell lysis of these methods were evaluated. The heating-Na2CO3 based method obtained a higher EPS yield with limited cell lysis. Proteins (PN)and polysaccharides (PS)were predominant in extractable EPSs. Particularly, PN-related substances were substantially enriched and high PN/PS ratios resulted in most methods. Different methods resulted in EPSs with a different size distribution. By analysis of Attenuated total reflectance-Fourier transform infrared spectra (ATR-FTIR), amide- and polysaccharide-associated bands were dominant. ATR-FTIR and fluorescence density of excitation-emission matrix spectra indicated EPS compositions and structures varied with the extraction methods. Moreover, the extraction/recovery protocol based on the heating-Na2CO3 method was remarkably improved, by varying heating time and using a centrifugal filter device with membrane (CFDM)to replace concentration and purification steps. Eventually, the thermal method with an extraction time of 45 mins was identified to be most effective. The application of CFDM was demonstrated as an alternative approach to concentrate and purify for EPS recovery. To our best knowledge, this is the first original study to systematically evaluate the different EPS extraction methods from anammox granules
Are Membrane Bioreactors Really More Efficient in Removing Pharmaceutical Substances?—Variance Component Analysis Of Micropollutant Removal
Full text linkThis study evaluates the influence of micropollutant chemical characteristics on the removal of pharmaceutical substances through three different treatments: membrane bioreactor, full wastewater treatment with final filtration (WWTP), and secondary treatment through a conventional activated sludges system, operated in parallel at realistic sludge retention time (SRT) over three years and four sampling campaigns. Treated wastewater from the WWTP enters the local canal with a low dilution ratio. Therefore, the monitoring of water contamination is of particular interest for a reliable assessment of environmental risk. A total of 39 pharmaceutical substances were screened. While differences among the three types of treatments were found statistically not significant, data analysis performed through a generalized linear model showed that both the influent concentration and the physicochemical characteristics are strong predictors for the removal of micropollutant. SRT had no significance for the three types of treatment of this study. Finally, pharmaceuticals were divided into three major classes based on their influent concentration and removal. A canonical discriminant analysis was used to predict the removals and showed that the pharmaceuticals removal rates are strongly influenced by their hydrophobicity/hydrophilicity and enabled to predict their removal categories with high accuracy (i.e., 65% of correct predictions)
Where and how acting to reduce the environmental risk due to PFAS from textile wastewater
Full text linkEffect of Paper vs. Bioplastic Bags on Food Waste Collection and Processing
Full text linkPurpose: The most abundant among the separately collected waste materials in Italy is food waste. This research aims to evaluate the influence of the type of collection bag on the food waste management chain. In Italy, the food waste collection is mainly based on bioplastic bags. As an alternative, a new type of recycled paper bag shows potential advantages. Methods: The two types of collection bag were compared evaluating the weight loss of food waste during the household storage, by means of an experimental assessment simulating the domestic dynamic bag filling. Moreover, the biomethane production of bags under anaerobic conditions was measured at the lab-scale level with Biochemical Methane Potential (BMP) tests. Results: During the household storage, the breathable fabric of the paper allows for higher weight losses, ranging on average between + 29 and + 44% compared to bioplastic. BMP tests, carried out under different conditions (temperature, inoculum), showed a 2–14 times higher generation of methane by paper bags compared to bioplastic bags, when referred to 1 kg of inserted food waste. Conclusions: Collecting the food waste inside paper bags shows advantages compared to the use of bioplastic bags. First, the waste collection is benefitted thanks to the lower weight of material to be transported to treatment plants, leading also to the possibility of decreasing the collection frequency. Moreover, paper resulted more compatible than bioplastic with the anaerobic digestion treatment, which is currently rapidly increasing as a food waste management option
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