Nicola Moraci

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.

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.

A new test apparatus for the study of geotextiles behaviour as filters in unsteady flow conditions: relevance and use

Abstract In many applications, geotextiles are subjected to cyclic hydraulic loads, for example, when used as revetment filters. A new test apparatus has been developed to investigate the influence of a cyclic component in the hydraulic gradient and the effect of boundary conditions. The boundary conditions to be considered in such applications of geotextiles are mainly the normal effective stress and the type of contact, which can be more or less continuous. The test apparatus presented in the paper is capable of reproducing these conditions while imposing a cyclic gradient. A set of tests have been performed using the apparatus in cyclic flow conditions perpendicular to the filtering interface: typical test results are also presented in the paper.

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...

Pullout Behaviour of Different Geosynthetics Embedded in Granular Soils

The paper deals with the results of a large experimental program aimed at the study of the behaviour of different geosynthetics in static pullout conditions. The pullout tests were carried out using a large test apparatus composed by a pullout box, a vertical load application system, a horizontal force application device, a special clamp, and all the required instrumentation. The displacements of the specimen have been measured and recorded through inextensible steel wires connected to the specimen in at least six different points and to RVDTs fixed to the external back side of the box. Tests have been performed on a uniform medium sand compacted at 95% Proctor. Two different types of geosynthetics have been tested. More than 10 pullout tests have been performed, varying the applied vertical pressures (10, 25, 50 kN/m2). The horizontal speed has been equal to 1.0 mm/min for all tests. The discussion of the test results allows to evaluate the influence of applied vertical pressures on pullout behaviour.

Numerical Modelling to Calibrate the Geotechnical Model of a Deep-Seated Landslide in Weathered Crystalline Rocks: Acri (Calabria, Italy)

Crystalline rocks are often subjected to several types of mass movements, depending on their weathering grade. These rocks are present in the European area along the Italian and French Alps, in the North-East area of Portugal, in the Sierra Nevada Massif (Spain) and in Greece. In particular, crystalline rocks are also widespread in Calabria and a high percentage of these rocks is present in the Sila, Serre and Aspromonte Massifs. Fresh or weathered crystalline rocks, highly fractured, may be affected by deep-seated landslides due to the presence of tectonic structures, which may predispose and control the landslide mechanisms. The Serra di Buda landslide, near the town of Acri (Cosenza), can be included among the deep-seated landslides which affect weathered crystalline rocks. Starting from the geological model, the analysis of the geotechnical data (digital terrain model, borehole logs, piezometer levels, superficial and deep displacements, geomaterial characteristics, etc.) allows to detect the uncertainties inherent the elements that concur to define the geotechnical model. To reduce some of these uncertainties a calibration by means of numerical modelling is carried out, and the results obtained show the usefulness of this approach.

Analyses and design procedure of a new physical model for debris flows: Results of numerical simulations by means of laboratory tests

(*) Mediterranea University of Reggio Calabria Dep. DICEAM via Graziella Loc. Feo di Vito 89060 Reggio Calabria, Italy. nicola.moraci@unirc.it (**)ETS de Ingenieros de Caminos Universidad Politécnica de Madrid Ciudad Universitaria, s/n 28040 Madrid, Spain (***)University of Padua Dep. ICEA via Ognissanti, 39 35129 Padova, Italy ANALYSES AND DESIGN PROCEDURE OF A NEW PHYSICAL MODEL FOR DEBRIS FLOWS: RESULTS OF NUMERICAL SIMULATIONS BY MEANS OF LABORATORY TESTS

Assessment of Internal Stability of Granular Soils by Means of Theoretical and Laboratory Methods

The assessment of the internal stability of a base soil is a fundamental aspect in the design of the filtering transitions. It can be evaluated by means of semi-empirical, theoretical and experimental methods; the assessment of internal stability of a soil using the available semi-empirical criteria can provide different results. In the paper, in order to verify and validate two methods recently proposed by the authors (Moraci et al. 2012a, b; Moraci et al. 2015), the internal stability of granular soils using different methods is evaluated. The internal stability of test soils has been firstly obtained by Kezdi, Sherard and Kenney and Lau criteria (semi-empirical methods), then it has been assessed theoretically by the method “SimulFiltr” and finally it has been verified by long term filtration tests performed in a rigid wall permeameter. The obtained results allowed us to better define the zones that constitute the new graphical method “Butterfly Wings Chart”, recently proposed by the authors.

Selective removal of heavy metals from landfill leachate by reactive granular filters

The pre-treatment of landfill leachate prior to its co-treatment in the municipal plants of waste water processing could represent an appropriate and cost-effective solution for its management. Pre-treatment is necessary especially to remove heavy metals, which may be transferred to the excess sludge preventing its valorisation. In the present paper, we propose a chemical-physical pre-treatment of leachate using four different granular reactive media able to selectively remove the contaminants present in the leachate. The efficiency of these materials was investigated using synthetic leachate through batch tests and a column test. In the latter case the four materials were placed in two columns connected in series and fed an under constant upward flow (0.5 mL/min). The first column was filled half (50 cm) with a granular mixture of zero valent iron (ZVI) and pumice and half (50 cm) with a granular mixture of ZVI and granular activated carbon (GAC). The second column, which was fed with the effluent of the first column, was filled half with zeolite (chabazite) and half with GAC. Heavy metals were mainly removed by the ZVI/pumice and ZVI/GAC steps with a removal efficiency that was higher than 98, 94 and 90% for copper, nickel and zinc, respectively, after 70 days of operation. Ammonium was removed by zeolite with a removal efficiency of 99% up to 23 days. The average reduction of the chemical oxygen demand (COD) was of 40% for 85 days, whereas chloride and sulphate removal was negligible.

Removal of heavy metals from landfill leachate using zero valent iron and granular activated carbon

ABSTRACT The possibility of a landfill leachate pre-treatment, aiming at heavy metals removal, by means of either zero valent iron (ZVI), or granular activated carbon (GAC) or by a mixture of the two materials, was investigated in this paper through batch and column tests. For this purpose, a synthetic landfill leachate containing heavy metals (i.e. Cu, Ni, Zn), chloride, sulphates, ammonium and organic matter was prepared. Batch tests results demonstrated the efficiency of ZVI, GAC and ZVI/GAC mixture in heavy metals removal (efficiency > 90%) and their negligible effect on the other contaminants. Column tests showed as pure ZVI is by far more efficient than pure GAC in the long term. The influence of humic acids (HA) on the reactive and hydraulic behaviour of ZVI was also studied through column tests. The presence of HA in the leachate caused a reduction of ZVI removal efficiency and a considerable decrease in its hydraulic conductivity. Results of a column test carried out using the ZVI/GAC granular mixture showed as the removal efficiency over time ranges from 100% to 89% for Cu, from 93% to 80% for Ni and from 98% to 95% for Zn. The use of a filter filled with the ZVI/GAC mixture could find application for leachate pre-treatment having the objective of removing heavy metals prior the final co-treatment with municipal wastewater minimizing adverse side effect on the process (e.g. transfer of heavy metals in the excess sludge to be used in agriculture). GRAPHICAL ABSTRACT