Paolo S. Calabrò

Heavy metals removal and hydraulic performance in zero-valent iron/pumice permeable reactive barriers

Long-term behaviour is a major issue related to the use of zero-valent iron (ZVI) in permeable reactive barriers for groundwater remediation; in fact, in several published cases the hydraulic conductivity and removal efficiency were progressively reduced during operation, potentially compromising the functionality of the barrier. To solve this problem, the use of granular mixtures of ZVI and natural pumice has recently been proposed. This paper reports the results of column tests using aqueous nickel and copper solutions of various concentrations. Three configurations of reactive material (ZVI only, granular mixture of ZVI and pumice, and pumice and ZVI in series) are discussed. The results clearly demonstrate that iron-pumice granular mixtures perform well both in terms of contaminant removal and in maintaining the long-term hydraulic conductivity. Comparison with previous reports concerning copper removal by ZVI/sand mixtures reveals higher performance in the case of ZVI/pumice.

Greenhouse gases emission from municipal waste management: The role of separate collection

The municipal solid waste management significantly contributes to the emission in the atmosphere of greenhouse gases (e.g. CO(2), CH(4), N(2)O) and therefore the management process from collection to treatment and disposal has to be optimized in order to reduce these emissions. In this paper, starting from the average composition of undifferentiated municipal solid waste in Italy, the effect of separate collection on greenhouse gases emissions from municipal waste management has been assessed. Different combinations of separate collection scenarios and disposal options (i.e. landfilling and incineration) have been considered. The effect of energy recovery from waste both in landfills and incinerators has also been addressed. The results outline how a separate collection approach can have a significant effect on the emission of greenhouse gases and how wise municipal solid waste management, implying the adoption of Best Available Technologies (i.e. biogas recovery and exploitation system in landfills and energy recovery system in Waste to Energy plants), can not only significantly reduce greenhouse gases emissions but, in certain cases, can also make the overall process a carbon sink. Moreover it has been shown that separate collection of plastic is a major issue when dealing with global warming relevant emissions from municipal solid waste management.

Estimate of the optimum weight ratio in zero-valent iron/pumice granular mixtures used in permeable reactive barriers for the remediation of nickel contaminated groundwater.

This paper presents the results of laboratory column tests aimed at defining the optimum weight ratio of zero-valent iron (ZVI)/pumice granular mixtures to be used in permeable reactive barriers (PRBs) for the removal of nickel from contaminated groundwater. The tests were carried out feeding the columns with aqueous solutions of nickel nitrate at concentrations of 5 and 50 mg/l using three ZVI/pumice granular mixtures at various weight ratios (10/90, 30/70 and 50/50), for a total of six column tests; two additional tests were carried out using ZVI alone. The most successful compromise between reactivity (higher ZVI content) and long-term hydraulic performance (higher Pumice content) seems to be given by the ZVI/pumice granular mixture with a 30/70 weight ratio.

Effect of the concentration of essential oil on orange peel waste biomethanization: Preliminary batch results.

The cultivation of orange (Citrus×sinensis) and its transformation is a major industry in many countries in the world, it leads to the production of about 25-30Mt of orange peel waste (OPW) per year. Until now many options have been proposed for the management of OPW but although they are technically feasible, in many cases their economic/environmental sustainability is questionable. This paper analyse at lab scale the possibility of using OPW as a substrate for anaerobic digestion. Specific objectives are testing the possible codigestion with municipal biowaste, verifying the effect on methane production of increasingly high concentration of orange essential oil (EO, that is well known to have antioxidant properties that can slower or either inhibit biomass activity) and obtaining information on the behaviour of d-limonene, the main EO component, during anaerobic digestion. The results indicate that OPW can produce up to about 370LnCH4/kgVS in mesophilic conditions and up to about 300LnCH4/kgVS in thermophilic conditions. The presence of increasingly high concentrations of EO temporary inhibits methanogenesis, but according to the results of batch tests, methane production restarts while d-limonene is partially degraded through a pathway that requires its conversion into p-cymene as the main intermediate.

Modelling of biogas extraction at an Italian landfill accepting mechanically and biologically treated municipal solid waste

This paper presents the results of the modelling of the biogas extraction in a full-scale Italian landfill by the USEPA LandGEM model and the Andreottola–Cossu approach. The landfill chosen for this research (‘Il Fossetto’ plant, Monsummano Terme, Italy) had accepted mixed municipal raw waste for about 15 years. In the year 2003 a mechanical biological treatment (MBT) was implemented and starting from the end of the year 2006, the recirculation in the landfill of the concentrated leachate coming from the internal membrane leachate treatment plant was put into practice. The USEPA LandGEM model and the Andreottola–Cossu approach were chosen since they require only input data routinely acquired during landfill management (waste amount and composition) and allow a simplified calibration, therefore they are potentially useful for practical purposes such as landfill gas management. The results given by the models are compared with measured data and analysed in order to verify the impact of MBT on biogas production; moreover, the possible effects of the recirculation of the concentrated leachate are discussed. The results clearly show how both models can adequately fit measured data even after MBT implementation. Model performance was significantly reduced for the period after the beginning of recirculation of concentrated leachate when the probable inhibition of methane production, due to the competition between methanogens and sulfate-reducing bacteria, significantly influenced the biogas production and composition.

Simultaneous removal of CUII, NIII and ZNII by a granular mixture of zero-valent iron and pumice in column systems

AbstractThe granular mixtures between zero-valent iron (ZVI) and other materials (e.g. sand, pumice) have been recently proposed to overcome the problems (e.g. clogging) related to the use of ZVI alone in treatment systems such as permeable reactive barriers or individual potabilisation systems. This paper presents the results of the research activity, carried out by column tests, aimed at comparing the performance of a granular mixture between ZVI and pumice (weight ratio 30:70) and of pure ZVI for the individual and combined removal of CuII, NiII and ZnII. The specific objective was to verify the occurrence of phenomena of mutual interaction and/or competition among contaminants. In fact, although metal removal by ZVI has been extensively documented in the past, the great majority of studies examined either very simple systems (i.e. single metal solutions) or very complicated ones (e.g. real acid mine drainage). In both cases, and for different reasons, the occurrence of mutual interactions (positive or...

The effect of separate collection of municipal solid waste on the lower calorific value of the residual waste

Nowadays, separate collection plays an irreplaceable role in municipal solid waste management and incineration in a waste-to-energy plant is one of the main disposal options. The objective of this study is to evaluate the effect of separate collection on the characteristics of residual municipal solid waste in terms of lower calorific value and ash production. Starting from the average Italian municipal solid waste composition, several separate collection scenarios have been considered evaluating the main characteristics of the residual waste (e.g. composition, water content, lower calorific value). Moreover, in order to have the opportunity of estimating the lower calorific value of residual waste for waste composition and separate collection scenarios different from those tested, a regression model is proposed, calibrated and partially validated.

Impact of mechanical street cleaning and rainfall events on the quantity and heavy metals load of street sediments.

The paper presents and analyses the results of a street sediments monitoring campaign carried out during dry weather in order to quantify the impact of mechanical street cleaning and rainfall events on the quantity and heavy metals load of street sediments. The study has been carried out in an experimental catchment in a medium traffic street of a residential/commercial area in the city of Reggio Calabria (Italy). Thanks to acquired data, it was possible to assess the amount and the degree of pollution of street sediments, the efficiency of mechanical street cleaning in terms of sediments and pollutants removal, the wash‐off of street sediments during rainfall events and the related potential impact on receiving water bodies. The results obtained confirm that street sweeping is generally scarcely effective as a practice for urban storm run‐off quality control and that run‐off is, on the contrary, quite effective in street sediments removal especially for smaller particles. Moreover, chemical analyses indicate that, although the concentration of heavy metals is higher in sediments particles having a diameter lower than 0.075 mm, the greatest part of the pollutants load is associated to larger particles.

European trends in greenhouse gases emissions from integrated solid waste management

The European Union (EU) has 28 member states, each with very different characteristics (e.g. surface, population density, per capita gross domestic product, per capita municipal solid waste (MSW) production, MSW composition, MSW management options). In this paper several integrated waste management scenarios representative of the European situation have been generated and analysed in order to evaluate possible trends in the net emission of greenhouse gases and in the required landfill volume. The results demonstrate that an integrated system with a high level of separate collection, efficient energy recovery in waste-to-energy plants and very limited landfill disposal is the most effective according to the indices adopted. Moreover, it is evident that a fully integrated system can make MSW management a carbon sink with a potentiality of up to approximately .

Possible interactions between recirculated landfill leachate and the stabilized organic fraction of municipal solid waste

The stabilized organic fraction of municipal solid waste (SOFMSW) is a product of the mechanical/biological treatment (MBT) of mixed municipal solid waste (MMSW). SOFMSW is considered a ‘grey’ compost and the presence of pollutants (particularly heavy metals) and residual glass and plastic normally prevents agricultural use, making landfills the typical final destination for SOFMSW. Recirculation of leachate in landfills can be a cost-effective management option, but the long-term sustainability of such a practice must be verified. Column tests were carried out to examine the effect of SOFMSW on leachate recirculation. The results indicate that organic matter may be biologically degraded and metals (copper and zinc) are effectively entrapped through a combination of physical (adsorption), biological (bacterial sulfate reduction), and chemical (precipitation of metal sulfides) processes, while other chemicals (i.e. ammonia nitrogen and chloride) are essentially unaffected by filtration through SOFMSW.