Four Italian pilot sites have been investigated, to validate the methodologies for collecting data about landfills and extractive waste facilities, and to test protocols and procedures to characterize the sites, thanks to sampling and analysis activities. The investigated pilots are:
- Campello Monti
CDW treatment plant (CAVIT): aggregate production: C&DW represents the first most important sector in terms of waste quantities produced in the EU-27 (32% or 821 million tons), the second one is represented by waste connected to mining industry (29% or 734 million tons) (Eurostat Statistics 2012). Considering the importance of C&D waste stream (production and recycling) at EU level, it was decided to include, in the list of the SMART GROUND pilot sites, a treatment plant which recycles C&DW to produce certificated aggregates: CAVIT spa.
CAVIT spa is sited in La Loggia (Fig. 1), a municipality 15 km far from Torino (Piedmont Region, Italy); its location is strategic as for the logistics connected to C&DW management: easy to reach, not far for Torino, near the Torino-Savona and Torino-Piacenza highways, and next to Torino bypass (La Loggia exit).
Cavit treatment plant was built to enhance the recovery of C&DW. Originally the Society was interested in aggregate exploitation, but during the 80s the Company decided to vote part of the activities to C&DW recovery and recycling. Cavit, which officially started its activity in 1990, is the elder and more important C&DW treatment plant at Piedmont level and one of the most important at Italian level, together with other treatment plants present in Emilia Romagna, Veneto and Lombardy.
Cavit treatment plant is authorized for the collection and treatment of several wastes, mainly represented by C&DW; the total amount of waste yearly treated is nearly 250.000t (Fig. 2, referring to 2016 on average). The 99% of the C&DW feeding the plant are recycled and only the 1% is landfilled or sent to other recycling activities.
The products coming from Cavit treatment plant are (Fig. 3):
- Recycled filler (0-10 mm): fine fraction (potentially used as soil for gardens, rehabilitation, etc…)
- Recycled sand (0-8 mm)
- Recycled aggregates (0-50 mm) aggregate for embankment
- Recycled aggregated (50-100 mm): draining material
Another products, obtained combining the two kinds of “recycled aggregates” is the mix 0-100 mm, uses as landfill covering and stabilized aggregate to build temporary tracks (eg during landfilling activities).
Campello Monti: The Campello Monti mining area is located in Strona Valley (Piedmont, Western Italian Alps), ca. 20 km from the Swiss border (Fig. 4). In the area, the mine waste deposits are related to the homonymous nickel mine, operating intermittently from the second half of the nineteenth century to 1945. In the area were exploited Fe-Ni-Cu-(Co) magmatic sulphide deposits occurring, from the Sesia to the Strona valleys, mostly in ultramafic layers, dykes and pipes of the so called “Mafic Complex”, in the Ivrea Verbano Zone (Fig. 5) (Garuti et al., 1980; Rivalenti et al., 1984; Sinigoi et al., 1994).
These deposits were exploited for nickel (average grade: from 1-2 to 0.5 wt. % Ni in the last years of activity), with an estimated production which probably never exceeded 50 short tons per year (Ferrario et al., 1982). The treatment activities in the area were intensive during the II World War and included a first phase of manual sorting, outside the mine adits, followed by mechanical (grinding, milling) and chemical (flotation) treatment.
The field activities, carried out by the UNITO team in spring – summer 2016, lead to the recognition of two types of “mineral waste” in the area:
- Waste rock which is the most common type of waste material occurring in dumps (Fig. 6), over an area of ca. 30.000 square meters.
Operating residues which occur in two areas: close to the dressing plant (deposit named “area 1”) and on the opposite side of the valley (area 8) (Fig. 7).
Based on the preliminary surveys, 8 waste areas were selected for the project: six rock waste dumps (areas 2 to 7) and two deposits of operating residues (areas 1 and 8). 41 samples of rock waste and 12 of operating residues were collected. The sampling map and the distribution of the studied waste deposits are shown in Fig.
The main geochemical features of all samples are typical of ultramafic rocks affected by processes of exsolution and accumulation of sulfide liquid, as typical of Ni-sulfide magmatic mineralizations worldwide. Concerning the metals content, the samples show a)
variable, but generally high to very high Ni, Co, Cu values; b)
relatively high Cr and Mn; c)
low REE content; d)
strongly localized PGE enrichments.
The SRM potential of waste materials connected with Ni-sulfide mining is represented by metals as Ni, Cu, Co and (possibly) PGE. The geochemical data allow the recognition of four groups of samples:
- “Group I” (area 1): very strong Ni (>10000 ppm), Cu (≥5000 ppm) and Co (>600 ppm) values;
- “Group II” (areas 3, 4, 8): strong Ni (2000-10000 ppm), Cu (600-1500 ppm) and Co (100-300 ppm) values;
“Group III” (areas 2, 6): moderate Ni (700-1600 ppm), Cu (200-600 ppm) and Co (100-200 ppm) values;
- “Group IV” (areas 5, 7): relatively low Ni (100-700 ppm), Cu (50-200 ppm) and Co (50-100 ppm) values.
A good positive correlation is generally observed between Ni, Co and Cu.
Concerning the critical PGE and Au, the geochemical data show that PGE content is highly variable (Pd+Pd: 5.8 to 821 ppb) and the main PGE are represented by Pd and Pt.
Montorfano mining area (Minerali industriali): feldspar production:
The Montorfano and Baveno granite ore bodies (Fig. 1) are located in the Lake District
(VCO – NE Piedmont). They were and are still quarried as dimension stones, with a consequent production of a huge volume of “waste”. Such waste has been exploited from 1995 thanks to the realization of a dedicated treatment plant, Minerali Industriali spa, in Verbania (Fig. 2), which aims to transform “quarry waste” in valuable resources. The dressing plant has got the concession (in 1995) to exploit three granite quarry wastes dumps: Sengio and Ciana Tane-Pilastretto areas, for white granite recovering in Montorfano massif, and Braghini area, for the pink granite exploitation in Monte Camoscio.
The granite quarry waste, transported from the quarry, arrives at the plant to be crushed, milled, sieved, dried and treated to remove the magnetic fraction and to produce, as main product, Quartz-Feldspars Products for ceramic and glass industries, together with other by-products. The main product is commercially known as F60P (quartz feldspar mixture: 60% of feldspar, mostly K-feldspar), whose production is about 80.000 t/year. Different by-products, obtained after the enrichment of produced “waste” (mainly powder granite and fractions enriched in ferromagnetic minerals), have to be added to the F60P production: they are commercially known as SNS-sand (premix for building uses), NGA-coarse black sand (used for industrial sandblasting), SF-wet feldspar (for the ceramic industry), and SF100 and SF200 (used as fillers in cement industries). The total amount of byproducts is about 120.000 t/year.
At the end of the dressing phases all the qw become raw materials. All the products find a place on different product markets, in such a way to contribute to the sustainability of technical-economic activities of the enterprise.
In the past (2009) a study by UNITO (Dino et al. 2012) investigated the volume and the characteristics of the extractive waste present in the yet exploited extractive waste facilities, in order to evaluate the quality of the ore body to mine and to estimate the period to recover and treat the dumped material.
During summer 2016 another sampling campaign, leaded by UNITO, was set; it interested Montorfano pilot site (new extractive waste facilities NE from Ciana-Tane-Pilastretto and Sengio mining areas; Fig. 3 - 4), object of SMART GROUND investigation. In total 8 samples were collected.
During the sampling campaign, other 8 samples from treatment plant (ECOMIN) were collected, in order to characterize the feeding material (from Sengio, Ciana-Tane Pilasteretto and Braghini areas) and the product and byproducts, and appreciate if and where an enrichment in CRM (eg. REE) is present.
The rock wastes present in the Montorfano pilot site seem to be very similar to the ones present in the yet investigated waste facilities (2009). Referring to the results of the past study, the exploited granite waste facilities are composed of > 30 mm material (70 – 75%), < 30 mm (20 %) and metric rocks (5 to10 %) (granitic gravel sand, with a small percentage of silt and the absence of clay). (Dino et al. 2012). The mineralogy of the samples generally reflects the characteristics of the original rock (Montofano white granite, as for the investigated pilot site). All the results connected to the previous study are present in Annex 9 and can be used, such as literature data, to evaluate the SRM potential of the investigated area.
The geochemical analyses connected to the last sampling activity (Summer 2016) reports that:
- Concerning the major elements, the rock waste samples show highly homogeneous geochemical features (Al2O3: 13.38-14.65; Fe2O3: 2.09-2.41, TiO2: 0.21-0.23, CaO: 1.33-2.01, MgO: 0.29-0.45, K2O: 4.49-5.18, Na2O: 3.26-3.51), that fit with the data from the literature
- As far as the minor and trace elements, the key feature is the relatively high REE content, typical of felsic, strongly differentiated magmatic rocks.
As expected, samples from the treatment plan show in part strongly different composition:
- Upgraded material:
This material has been depleted of the mafic minerals by magnetic separation. As a consequence such material is strongly depleted in iron (Fe2O3tot down to 0.13-0.15 wt.% in samples MO_02_05 and MO_02_07) and TiO2 (down to 0.012 wt.%); of course it also shows, compared to the feeding material, a general increase in SiO2.
- Magnetic fraction:
on the contrary, the magnetic fraction is, compared to the feeding material and (of course) to the demagnetized portion, strongly enriched in iron (Fe2O3tot up to 13.34-13.20 wt.% in samples MO_02_02 and MO_02_03), but also in MgO, MnO (and depleted in Na2O).
The Gorno mining District is located in the Seriana, Riso and Brembana valleys (Lombardy, Northern Italy). The District lies in the “Lombard Basin" of the Italian Southern Alps, where a strong subsidence during Permian-Triassic time allowed the accumulation of a thick sedimentary pile, composed of Permian continental deposits overlain by shallow sea Triassic sediment (Assereto et al., 1977). (Fig. 1
The Gorno Zn-Pb (±Ag, fluorite and barite) District belongs to the Alpine Type Zinc-Lead-Silver stratabound ore deposits (sub-type of the Mississippi Valley Type deposits), associated with the middle – upper Triassic carbonatic series. The mineralization mostly occurs within the “Metallifero” (i.e., “ore-bearing”) Formation of upper Ladinic – lower Carnian age. The dominant distribution trend of the orebodies is approximately N-S, as tabular “columns” up to over 2 kilometers long, with a width ranging from 50 to 400 meters and thickness between 3 and 20 meters (Omenetto and Vailati, 1977; Rodeghiero and Vailati, 1977).
The primary mineralization is mainly composed of sphalerite (ZnS) and galena (PbS) (average Zn/Pb ratio= 5:1), ± pyrite (FeS2), marcasite (FeS2), chalcopyrite (CuFeS2) and argentite (Ag2S). A secondary mineralization is composed of oxidation products of sphalerite, i.e., Zn-carbonate and silicate. The dominant gangue minerals are calcite, dolomite and quartz (± ankerite).
After a preliminary survey, the field activity, carried out in the September 2016 by the UNITO team, was focused on two areas:
- Arera mining area (extractive waste facilities) (Fig. 2);
- Gorno mine tailings deposits (Fig.
Rock waste sampling:
The waste sampling activity in Arera
area was focused on 6 extractive waste facilities (rock waste dumps), in an area of approximately 0,5 km (Fig. 4), at the exit of main mine tunnels.
Two main rock types occur in the dumps: grey limestone and beige to brown dolomitic rock (Fig. 5). A preliminary dumps survey showed that in the higher altitude areas (areas 2, 4, 5 and 6) the mineralization, mainly composed of coarse-grained sphalerite, is selectively concentrated in the dolomite, while the grey limestone is barren.
Tailing sampling was focused on one of the tailings deposit in the District, close to the Riso river (Fig. 6). 4 sampling points have been identified within deposit: three (DH1, DH2 and DH3) at a distance of 37 meters each other, the fourth one (DH4) in the easternmost part of the deposit, at a distance of 80 meters from DH3, to check the lateral continuity and the thickness of the top soil.
Sampling was performed by hand drilling (Fig. 7), removing first the top soil covering the tailing pond; samples of the tailing deposit were taken at different depth.
The geochemical characters of all the analysed waste samples are typical of ± dolomitized carbonate rocks.
The SRM potential of waste materials connected with the alpine-type Zn-Pb deposits mining is represented by metals as Zn, Pb, Ag, Cd, Ge, Ga, In and industrial minerals such as fluorite and barite.
The key points of the geochemical screening, regarding the potential SRM, are:
- A strong difference is observed between the rock waste samples (areas 2÷7) and tailings (area 1), especially for some metals. In particular, tailings are strongly depleted of Zn, but also Cd and Ga; they are instead enriched in Pb. Ag appears slightly depleted, but the small difference (coupled with the low concentration) is less significant;
- The waste rock is characterized by:
- Strong to very strong Zn concentration (8.07 to 29.4 wt.% Zn);
- Relatively high Cd content (69.2 - 830 ppm), and low to moderate Ga values (6.0 – 88.6 ppm);
- Very low Ge and In content (mostly <1 ppm);
- Low Pb and Ag content.
- The tailings show instead:
- Much lower Zn (190 – 8950 ppm), Cd 1.1 – 39.1 ppm) and Ga (<0.1 – 7.0 ppm) contents;
- A Pb content much higher than the waste rocks, but rather low as absolute values (38.7 – 2170 ppm).
Considering the industrial minerals fluorite and barite, their relative abundance can be inferred by the F and Ba analyses.
The Zn content is positively correlated with Cd and Ga, which clearly occur as minor elements in sphalerite.