1,720,989 research outputs found
Potential of compost mixed with tuff and pozzolana in site restoration
No full textThe present research is aimed at evaluating the potential of mixtures made of different percentages of compost (10%, 20% and 30% by volume) and inorganic waste from extraction activities (tuff and pozzolana) for site restorations. The materials alone and the mixtures were characterised from a geotechnical point of view, in order to determine the optimal percentage to be used. In particular, the oedometric test and the direct shear test were performed. Also the environmental quality of the materials was investigated through chemical characterisation and a leaching test. In addition, a lab-scale seeding test was carried out to assess the potential phytotoxicity of the mixture. Finally, at the end of the experimentation the accumulation of heavy metals in the plants was determined and the plants. +. artificial soil system underwent a shear stress test.The presence of compost in the percentages tested did not reduce the mechanical performances of the inorganic residues, guaranteeing good resistance and stability. In fact, the response to oedometric compression, the compression coefficient and the internal friction angle of the mixtures were quite similar to those obtained for tuff and pozzolana alone.The mixtures selected as optimal from a mechanical point of view (30% by volume of compost and 70% by volume of tuff/pozzolana), did not represent a potential hazard for the environment due to the low content and negligible leachability of heavy metals. In addition, such mixtures can provide a good substrate for revegetation thanks to the high content of organic matter and the absence of phytotoxic effects in the conditions tested. © 2015 Elsevier Ltd
Innovazioni tecnologiche nella discarica di rifiuti pretrattati e relativo impatto ambientale
Full text linkA seguito dei recenti sviluppi della normativa italiana ed europea, i sistemi di gestione dei rifiuti saranno organizzati in modo che in discarica siano conferiti rifiuti pretrattati caratterizzati da un basso grado di putrescibilità, al fine di realizzare discariche più facilmente gestibili, controllare le emissioni a lungo termine e ridurre quanto più possibile la durata della fase successiva alla chiusura, in cui è indispensabile operare il monitoraggio ed il controllo delle emissioni.
Sulla base di queste considerazioni la presente ricerca ha posto l’attenzione su differenti tipologie di rifiuti pretrattati
meccanicamente, biologicamente e termicamente e loro miscele destinabili allo smaltimento in discarica; tali rifiuti, Frazione Organica di Rifiuti Solidi Urbani (FORSU) a diverso grado di biostabilizzazione aerobica e scorie da incenerimento di RU sono stati utilizzati per realizzare diversi reattori in scala semi-pilota, gestiti in maniera “tradizionale”, cioè anaerobicamente, ed in condizioni
semiaerobiche, al fine di verificarne il possibile impatto ambientale, in termini di qualità del percolato, condizioni igienico-sanitarie e durata della fase di post mortem per un rapido recupero del sito. Ciascun rifiuto è stato caratterizzato inizialmente da un punto di vista chimico, biologico e geotecnico; per ciascun reattore sono stati inoltre monitorati i cedimenti e le caratteristiche di rifiuti e
percolato.
Prima di realizzare i reattori, si è provveduto inoltre a caratterizzare il comportamento alla lisciviazione dei rifiuti utilizzati e delle loro miscele, anche con l’obiettivo di verificare il rispetto dei vincoli normativi imposti per l’ammissibilità dei rifiuti in discarica. A
questo scopo sono stati utilizzati diversi test di lisciviazione (prEN 12457-1 e prEN 12457-2), sui cui eluati sono state misurate le concentrazioni di metalli pesanti, cloruri, solfati, TDS e sono state valutate le discrepanze tra la normativa italiana ed europea in materia di ammissibilità in discarica. Gli eluati prodotti da FORSU, scorie e dalla loro miscela sono compatibili con i limiti imposti dalla normativa nazionale per lo smaltimento in discarica per rifiuti non pericolosi, ma non con quelli della corrispondente normativa europea, che presenta limiti più restrittivi. Si è inoltre effettuato uno studio delle caratteristiche di rilascio tramite l’applicazione del test NEN 7341, che fornisce indicazioni sul massimo rilascio potenziale di contaminanti, e l’ANC/BNC che, al variare del pH della soluzione lisciviante, consente di valutare la capacità di neutralizzazione acida e basica di un materiale e di costruire le curve di
solubilità dei diversi metalli. Le scorie presentano una elevata ANC, che consente di favorire la rapida estinzione della fase acida, con vantaggi per la solubilizzazione dei metalli, di anticipare la fase metanigena e ridurre la produzione di biogas. Le curve di solubilità mostrano un andamento molto diverso per i vari metalli, a seconda del contenuto in organico del rifiuto analizzato: si riscontrano minimi nella solubilità per pH in campo lievemente alcalino (7-9) per matrici, come le scorie, ad elevato contenuto di inorganico, e per pH neutro per la FORSU, a prevalente carattere organico.
A seguito dello studio dei reattori di discarica, si è mostrato che il cosmaltimento di FORSU e di scorie rappresenta una valida alternativa alle discariche monorifiuto, con vantaggi in termini di qualità del percolato e di un più rapido recupero finale del sito,
grazie ad un più rapido sviluppo dei cedimenti, che peraltro risultano di entità minore; le scorie infatti, ripristinano il materiale strutturale eliminato dal rifiuto durante le fasi del pretrattamento meccanico-biologico, consentendo una riduzione dei cedimenti del cumulo. Inoltre, le scorie, grazie alla loro elevata capacità tampone ed alla diluizione che esercitano sul contenuto iniziale di sostanza organica, consentono, come mostrato dal profilo temporale del pH e del carico organico nel percolato, di raggiungere in tempi ridotti le condizioni metanigene, nelle quali il metabolismo dei microrganismi anaerobici risulta accelerato. In tal modo si raggiungono più
velocemente le condizioni di stabilità biologica e meccanica dei rifiuti, si riduce significativamente la produzione di biogas e la durata della fase di gestione post-operativa.
Nell’ambito del cosmaltimento, la gestione semiaerobica (condizioni aerobiche e anaerobiche alternate), accelera il processo di biodegradazione, con una significativa riduzione di emissioni di COD ed azoto ed un più rapido raggiungimento delle condizioni di stabilità strutturale, rispetto alla tradizionale gestione anaerobica. L’aerazione comporta, tuttavia, alcuni oneri: la necessità di gestire
opportunamente gli apporti idrici e la portata di aria per assicurare le condizioni ottimali per la biomassa, un incremento dei costi di esercizio per la fornitura di aria, problemi associati a intasamento e ostruzione degli impianti di aerazione ed alla distribuzione e circolazione dell’acqua.
Lo studio di due diverse tipologie di discariche monorifiuto, contenenti FORSU rispettivamente parzialmente e totalmente
stabilizzata, ha mostrato che, a parità di intervallo temporale, le emissioni di COD ed azoto in quest’ultimo caso sono ridotte di circa il 70-80% e si ottiene una maggiore stabilità meccanica.
Per tutti i reattori esiste comunque un elevato grado di correlazione tra le caratteristiche del percolato ed i parametri microbiologici, chimici e geotecnica dei rifiuti.
Dal bilancio di massa effettuato tra contenuto iniziale di metalli nei rifiuti ed rilascio nel percolato al termine del monitoraggio, si ottiene che il quantitativo trattenuto all’interno di tutti i reattori è generalmente superiore al 90%, a causa sia dei crescenti valori di
pH, sia della presenza di agenti complessanti organici ed inorganici, che ne riducono la solubilità; si riduce dunque la pericolosità del percolato a breve termine, ma si genera un potenziale fattore di rischio per il lungo termine.
Dal confronto tra i parametri di caratterizzazione del percolato e i cedimenti misurati nel reattore di cosmaltimento anaerobico ed in quello contenente FORSU ad elevato grado di stabilizzazione, si nota un comportamento sovrapponibile, che fa ipotizzare l’equivalenza di un trattamento biologico più spinto e di uno smaltimento congiunto di sostanza organica a basso grado di
biostabilizzazione e scorie da incenerimento; entrambe le configurazioni consentono infatti di raggiungere le condizioni metanigene in tempi più brevi e quindi di conseguire i seguenti vantaggi sia da un punto di vista gestionale, che di minimizzazione di impatto ambientale e di tempi di recupero del sito: miglioramento della qualità del percolato, riduzione della produzione di biogas e miglioramento delle caratteristiche meccaniche dei rifiuti.
Le valutazioni e le considerazioni conclusive sono necessariamente soggette ad un’attenta ed accurata valutazione preliminare degli oneri economici dei processi di pretrattamento al fine di ottimizzare il rapporto costo/beneficio dell’intero sistema “trattamento -smaltimento”.Due to the European and Italian laws in force, the waste management integrated systems will be necessarily organized with the aim of landfilling only pretrated and at least partly stabilized waste; these “new” refuses, having very different characteristics with respect of the raw waste, will allow a significant reduction in terms of biogas production and leachate pollutant load, even if this reduction
will be not enough to result compatible the environment and the long-term behaviour is still to be understood; new disposal
conditions and new management strategies must be defined, aiming at facilitating the development of the biodegradation processes,
the achievement of the stabilization conditions and the shortening of the aftercare phase.
Based on these issues, the present research focused on the behaviour of different pretreated waste and their mixtures once landfilled; in particular, Municipal Solid Waste Organic Fraction (MSWOF) at a different biostabilization degree (15 and 90 days), coming from a selection and composting plant, and bottom ash (BA) from MSW incineration were used to realize several landfill reactor in semipilot
scale; such reactors were managed in different ways (anaerobic and semi-aerobic conditions), in order to evaluate the potential emissions via leachate, the sanitary implications and the length of the post-closure phase.
The wastes were initially and periodically characterized in terms of several chemical, microbiological and geotechnical parameters;
besides leachate characteristics and settlements of the bulk waste were monitored.
Prior to be landfilled, the leaching behaviour of the waste and mixtures used was investigated, thus verifying whether the parameters analyzed in the eluates produced were below the limits fixed by Italian and European laws in force for non-hazardous waste. prEN 12457-1, prEN 12457-2 tests were executed, along with some other characterization tests: Toxicity Characteristic Leaching Procedure (TCLP), NEN 7341, which provided information about the maximum potential emission from the waste (availability) and Acid/Basic Neutralization Capacity (ANC/BNC), which furnishes the acid/base need by the waste to reach a predetermined pH, and pH static test, through which the heavy metals solubility curves as a function of pH can be developed. The eluates obtained in each
test were characterized in terms of heavy metals, chlorides, sulphates, Total Dissolved Solids (TDS). The results obtained were used to compare the Italian and European laws regarding the acceptance of waste in landfill as well as the different behaviour of the waste
studied as pH and liquid to solid ratio (L/S) changes.
BA showed the maximum ANC value, resulting in a higher buffering effect exerted by this material, once landfilled; due to such a behaviour, the solubility of heavy metals in leachate is probably significantly reduced; besides, the length of the acid phase in the anaerobic metabolism can be shortened, allowing both a faster establishment of the methanogenic conditions and a limited production of biogas.
The solubility curves showed different behaviour, depending on the organic content of the waste; in particular, minimum values of the heavy metal solubility corresponded to slightly alkaline pH (7÷9) for wastes with higher inorganic content, such as BA, and for neutral pH for predominantly organic waste, such as MSWOF.
MSWOF, BA and their mixture resulted non-hazardous according to Italian law; with respect to the European Directive MSWOF
resulted hazardous, due to the more restrictive limits.
Arising from the results obtained by the study of the reactors, the anaerobic co-disposal of BA and MSWOF biostabilized at 15 days, in the percentages here used (30-70% by weight), allowed to reach some advantages in terms of both leachate organic load and a more rapid definitive closure of landfill, due to the more rapid settlements exhaustion and stabilization; besides, final settlements results lower. The presence of BA behaved as a rigid skeleton which firstly retarded the start of settling and secondly hindered the
settlement rate, thus leading to a lower value reached at the biological stability occurrence. Despite the space increase made available by the biodegradable fraction consumption, the bulk waste did not settle appreciably because the BA, by aggregating the residual waste particles, made a sort of “cement”. Probably BA supplied aggregating and stabilizing properties to the materials which they are added to and functioned as structural and support material.
The air supply to one of the mixed reactors, allowed to accelerate the biodegradation process, providing a significant reduction in the leachate organic load and a faster mechanical stabilization of the bulk waste; nevertheless, the aeration implies some burdens: proper air and water addition for the biological aerobic metabolism, costs increases due to the air needs, clogging of the air supply pipes, homogeneous water distribution and circulation.
By the study of the monolandfills, containing MSWOF 15 and 90 days biostabilized, the release was significantly reduced (of about
70-80%) in the leachate from the latter and also a higher mechanical stability was reached.
It is noteworthy that for all the reactors, the total amounts of heavy metals released during the experimental activity represented only a very limited fraction (in some case lower than 10%) of the initial content measured in the bulk waste. Consequently, leachate hazardousness resulted lower, on the other hand, significant heavy metals release can occur in case of pH or Eh changes in the
landfill, due for example to oxygen and water entry because of the exhaustion of biogas production and problems at the isolation system.
The data obtained showed that co-disposal of BA with MSWOF, being previously partly biostabilized, can allow to achieve a more
rapidly plateau conditions of both the organic load released in the leachate, and the settlements of the bulk waste, unless for the operating conditions and the waste fraction percentages tested in this study. This implies some clear advantages in terms of the postclosure management. Moreover, leachate organic load and settlements trends were shown to be quite similar in the case of codisposal of BA and partly biostabilized MSWOF, and in the case of completely biostabilized MSWOF landfilling; thus co-disposal seems to represent a valid alternative to a more stressed and expensive pre-treatment phase.
Finally, a strong correlation between the biochemical parameters of leachate and the mechanical behaviour of the bulk waste was
demonstrated to exist. This correlation can be used as a valuable tool in both designing and modelling of landfill plant. It can also help in planning the best management practises as well as the economic implications related to either life or post-closure period of the landfill
The influence of iron concentration on biohydrogen production from organic waste via anaerobic fermentation
No full textDifferent micronutrients are essential for bacterial fermentative metabolism. In particular, some metallic ions, like iron, are able to affect the biological H2 production. In this study, batch tests were carried out in stirred reactors to investigate the effects of Fe2+ concentration on fermentative H2 production 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 H2 production from OW (922 mL) compared with the control (without iron doping). The highest H2 production (1736 mL) from FW occurred when Fe2+ 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 H2 production from FW was almost negligible
Fe(II) and Mn(II) removal from contaminated groundwater by adsorption: a comparison between activated carbon and pine bark
No full textExploring the potentials of applying the circular economy for waste minimization at a regional scale based on Big Data Analysis
No full textAlthough significant achievements have already been made in waste recycling, the quantity of material residues that annually end up in landfills is still regarded as an important environmental pressure at the global level. This paper presents the development of a methodology for studying the potentials of resource recovery for regions and provinces with a case study in the Province of Brescia. The provincial waste management database was used for mapping the wastes' origins and destinations. A Big Data Analysis approach was followed by developing two software packages. The first package is designed in the Powerbi environment to analyse waste management in each waste category, sector, and zone. The second tool was developed using R statistical software for preparing the mass-balance models in combination with spatial analysis. The two packages provide the possibility for planning interventive actions such as the circular economy and industrial symbiosis by identifying the most problematic points and targeting the improvement measures to minimize waste disposal
The experience of the first industrial symbiosis platform in Italy
No full textThis paper reports the activity, promoted by the Italian agency for new technologies, energy and sustainable economic development (ENEA), in the framework of the project for the development and implementation of the first Italian Platform for Industrial Symbiosis implemented in Sicily (2011-2015). The goals of the project were: to provide a methodology and an instrument for industrial symbiosis implementation at regional scale, to implement a IS Platform as a support to SMEs to individuate symbiosis opportunities in the region. The whole approach includes: network activation, platform architecture design and implementation, analysis of the productive sector in Sicily, data collection and companies involvement. In particular the paper focuses on the activities developed for companies’ network creation trough a preliminary analysis of the predominant productive sectors followed by the organization of operative meetings in Sicily for companies’ involvement, analysis of potential synergies and resources sharing, and finally platform population. During the first two meetings more than 80 SME were linked giving rise to almost 400 output resources and almost 180 input resources. More than 690 potential matches were found between the participating enterprises showing interesting opportunities both for substituting resources with waste products in real and virtual cases and for sharing waste management services and infrastructures. The discussion occurred during the meeting has remarked the significance and the consequences of the regulatory and control system on IS application, underlining the necessary participation of local stakeholders and control authorities. It has also emerged the need to identify predominant productive activities in well-defined territorial contexts where to investigate the specific/local tangles taking into account legislative and technical-economic feasibility. Technical dossiers on three main resource streams (wastes from processing stone materials; plastics and agro-industrial wastes), which may generate the more interesting potential synergies, are being processed. These dossiers include European, Italian and regional regulations, guidelines, technical standards, logistic and economical aspects useful for supporting companies in synergies implementation. Results of this activity will also be used to improve the algorithm in the platform to find synergies. © 2015, Gh. Asachi Technical University of Iasi. All rights reserved
Fe(II) and Mn(II) removal from contaminated groundwater by adsorption. A comparison of activated carbon and pine bark
Full text linkThis paper aims to compare the adsorption performance of activated carbon and pine bark for iron and manganese removal from contaminated groundwater. Moreover, their environmental compatibility was checked for their possible use as reactive media in a permeable reactive barrier for in situ remediation. Batch tests were carried out with different iron and manganese concentrations and different particle-size distributions, in order to evaluate the effectiveness of the activated carbon and pine bark on removal depending on both the initial pollutant concentration and the surface area of the adsorbent. High removal efficiencies were reached by both of the reactive media. However, faster removal at higher concentration was observed only for iron adsorption by activated carbon. The particle-size distribution did not significantly influence the process in the experimental conditions tested. The immobilization process on the reactive media can be considered almost irreversible since the quantities of iron and manganese released during the desorption tests were negligible
Going 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
Environmental and economic performance of chemical and biological processes for treating petroleum hydrocarbon-contaminated soil: An experimental study
Full text linkOver the past ten years, researchers have applied various approaches to treat petroleum hydrocarbon-contaminated soil and assess its performance based on removal efficiencies and not on its environmental and economic impacts. In this study, the environmental and economic performances of the operational stages of electro-Fenton and bio-slurry technologies are investigated and compared using a life cycle assessment to assess the environmental and economic performances in treating petroleum hydrocarbon-polluted soil. The data used in this study were collected from primary and secondary sources, and the potential 18 environmental impacts were calculated using the ReCiPe 2016 characterization approach in SimaPro 9.5 software. The electro-Fenton process is the most environmentally friendly method, identifying chemicals and energy as major contributors to the environmental impact. Energy is the main hotspot, accounting for 90 % of the total environmental impact. Energy and biosurfactants are the main environmental hotspots in bioslurry processes, accounting for 60 % of the total. The bioslurry process has the highest environmental impact owing to the use of biosurfactants and electricity consumption. The bioslurry process is the most cost-effective, with a life-cycle cost of 7.13/kg) owing to the use of BDD as the electrode, costing 323$/kg
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