Thermal impact evaluation of an open loop heat pump system: integrated approach with project data, numerical modeling and groundwater monitoring

Open loop, geotermal system, low enthalpy, numerical simulation, FEFLOW-DHI

Future regulation for the reduction of PFAS pollution in aquifers and for the improvement of drinking water quality

This Technical Note, inspired by some recent international scientific contributions, focuses attention on the relationships existing between the diffusion of per- and polyfluoroalkyl substances and the drinking water environmental sector. Firstly, the analysis takes into consideration published data to highlight the ubiquity of PFAS in the aquifers of various nations. There are also some health implications resulting from the exposure of individuals to PFAS following the ingestion of contaminated water. The technical background is then compared with the current state of the regulatory framework, indicating the reasons, collateral initiatives and precautionary criteria that must guide an urgent and effective remodeling of the law

Hexavalent Chromium: Analysis of the Mechanism of Groundwater Contamination in a Former Industrial Site in the Province of Vicenza (Northern Italy)

The study consisted in the analysis of the mobilization mechanisms of hexavalent chromium (Cr(VI)) into groundwater from a decommissioned contaminated factory. The site is located in the Province of Vicenza and formerly was a chrome-plating plant. The subsoil consists predominantly of gravelly deposits with a thickness of at least one hundred meters. An unconfined aquifer is present with water table at about 23 m depth bgl. During the seven years of monitoring (2008-2014), the fluctuation of groundwater level was more than 6 m; hydraulic conductivity is about 1.0E-03 m/s and groundwater seepage velocity about 12 m/day. At the area of the source of contamination, the unsaturated soil is contaminated by hexavalent chromium throughout the thickness: concentrations range from 200 to 500 mg/kg. At the bottom of zone of groundwater level fluctuation, the hexavalent chromium concentration decreases to below the detection limit. The available data (e.g. hexavalent chromium concentrations in groundwater, groundwater level, local rainfall) give the opportunity to assess the effects, on the magnitude of groundwater contamination, of the effective infiltration versus the fluctuation of groundwater level. The main analysis was performed on a statistical basis, in order to find out which of the two factors was most likely related to the periodic peaks of hexavalent chromium concentration in groundwater. Statistical analysis results were verified by a mass balance. Data show that at the site both the effective infiltration through the unsaturated zone and the leaching of soil contaminated by groundwater, when it exceeds a certain piezometric level, lead to peak concentrations of hexavalent chromium, even if with characteristics and effects different

The effects of low enthalpy geothermal system on groundwater of the Cesine wetland

Cesine Wetland, Salento, low-enthalpy geothermal power plant, heat transport numerical model

Applying the Principal Component Analysis for a deeper understanding of the groundwater system: case study of the Bacchiglione Basin (Veneto, Italy)

In hydrogeology, it is often difficult to fully understand the hydraulic factors affecting the recharge of groundwater systems. Particularly, at a regional scale, the groundwater system can have different drivers depending on the considered area, i.e., soil permeability, paleochannels, and precipitation. Chemicalphysical (i.e. temperature) or hydrogeochemical data can help such understanding. However, this type of information is usually sparse at the regional scale, whereas extended groundwater piezometric head monitoring is more common. This study aims at exploiting these longitudinal observations of the hydraulic head to validate (and possibly bring more insights into) the geological structural model of aquifer systems. Clustering control points based on the piezometric head average annual variations can help the system conceptualization in two ways: (i) clusters can geographically identify areas with similar hydrogeological behavior; and (ii) the typical cluster annual variation with its ups and downs can bring insights on the recharge component of an aquifer system. Nevertheless, visual clustering can be a long and subjective procedure, thus this study suggests the use of the Principal Component Analysis to cluster the control points with a similar average annual variation of their recorded time series. This study supports the proposed analysis by applying it to the monitoring data of the Bacchiglione basin resulting in (i) clusters identified based on the number, moment, and lengths of groundwater level peaks and minima, (ii) wellgathered clusters in space, underpinning the groundwater hydrograph dependence on local driving factors. Furthermore, the investigation of clustering anomalies highlighted the relevance of the presence of time series with different recording periods pinpointing, however, the method's capacity to spot a change in the hydrogeological cycle over the years

The Compatibility of Geothermal Power Plants with Groundwater Dependent Ecosystems: The Case of the Cesine Wetland (Southern Italy)

The Cesine Wetland, located along the Adriatic coast, was recognized as a Wetland of International Interest and a National Natural Park. Managed by the "World Wide Fund for nature" (WWF), it is considered a groundwater dependent ecosystem which is affected by seawater intrusion. The site was selected to test the environmental compatibility of a low-enthalpy geothermal power plant (closed loop) operating in the aquifer saturated portion with purpose to improving the visitor centre. For this purpose, the long-lasting thermal impact on groundwater was assessed using a multi-methodological approach. The complex aquifer system was carefully studied with geological, hydrogeological and geochemical surveys, including chemical and isotopic laboratory analyses of surface water, groundwater and seawater. The isotopes δ18O, δD, δ11B, and 3H were useful to clarify the recharge contribution, the water mixing and the water age. All information was used to improve the conceptualization of the water system, including aquifers and the boundary conditions for a density driven numerical groundwater model. The purpose was to forecast anthropogenic thermal groundwater variations up to 10 years of plant working before the plant realization and to validate the solution after some working years. All results show the environmental compatibility notwithstanding the peculiar ecological environment

Hydrogeological Features and Sustainable Use of Geothermal Resources: Selected Case Studies in Italy

Within the framework of the activities aimed at studying current and future exploitation and the related sustainability of geothermal resources, and considering the key role hydrogeology plays in the study of geothermal systems and design of installations, in October 2012 the Working Group IDROGEOTER was set-up within the IAH (International Association of Hydrogeologists) Italian Chapter. The first activity of IDROGEOTER‘s workplan is the analysis of state of the art in current use of low-to high enthalpy geothermal resources in Italy and of the hydrogeological settings resulting from features (e.g.: hydrostratigraphy, hydraulic and hydrodynamic conditions, hydrogeochemistry, …) influencing the availability of the resource and the potential of the systems. Detailed studies supporting the possible optimization of the use of geothermal resources, carried out in different areas (see figure) and under different hydrogeological conditions in Italy, are described in the paper. In the Piedmont Region (NW Italy) several experimental sites have been investigated in order to assess the potential subsurface effects of open-loop Groundwater Heat Pumps (GW-HPs) plants for the cooling and heating of buildings. A comparison between field measures and numerical modelling results reveals that the most important aquifer parameters affecting the developing of the Thermal Affected Zone (TAZ) around the injection wells are those related to advective heat transfer. The Lombardy Region (N Italy) is currently the most populated and industrialized region in Italy and therefore the area where the highest number of GWHP plants (open and closed loop) are installed, from which a representative sample will be selected with the objective of identifying the critical hydrogeological factors contributing both to the geothermal potential and to a sustainable use of the resource. In the Veneto Region (NE Italy), the Euganean Geothermal Field is the most important thermal field in northern Italy (about 250 active wells) and the thermal waters (65-86 °C) are mainly used for spas; recently, a new conceptual model of the Euganean Geothermal System has been proposed and tested in a numerical model; with regard to low enthalpy, studies on sites potentially suitable for closed-loop and open-loop systems, together with data from automated monitoring of several wells, could be used for advanced analysis of different hydrogeothermal systems. Research activities in the Lazio Region (Central Italy) focus also on low enthalpy and are specifically aimed at the mapping of the geothermal potential of aquifers, and at pilot studies of sites characterized by gravel aquifers, alluvial Holocene deposits of the Tevere River and alluvial pre-volcanic Pleistocene deposits. In the Campania Region (S Italy - Mondragone plain), in the framework of the geothermal exploration programme “VIGOR” (Evaluation of Geothermal Potential in Convergence Region), a groundwater balance, verifying the recharge area of thermal springs (temperature 33-54 °C) connected to a large carbonate aquifer, has permitted the identification of the most suitable area in which to drill a geothermal well. In the Apulia Region (SE Italy) the thermal field trends consequent to groundwater advection and the influence of seawater intrusion have been reconstructed for two karstic coastal aquifers (Murgia and Salento) at various elevation between -5 and -100 m amsl. These reconstructions are intended to provide required base knowledge for correctly implementing low enthalpy HP plants in the saturated zones. Further studies and inventory of data and applications will be part of the activities of IDROGEOTER, which will also include the preparation of a proposal of guidelines for hydro-geothermal studies

Groundwater conservation and monitoring activities in the middle Brenta River plain (Veneto Region, Northern Italy): preliminary results about aquifer recharge

In the middle Brenta River plain there is a unconfined aquifer that represents an important groundwater resource in Veneto region. In this area the main groundwater recharge factor is related to the stream seepage: the water dispersion from the Brenta river is active with variable intensity from the foothill to the alignment Nove di Bassano - Cartigliano (Province of Vicenza). In order to mitigate the expected groundwater effects, due to future important waterworks withdrawals provided by the regional water resources management plans, an experimental project of Managed Aquifer Recharge has started, by means of the realization of some river transversal ramps. The construction of pilot works, partially completed, were preceded by a specific hydrogeological monitoring program, aimed to the evaluation of the effectiveness of the MAR actions in terms of comparison between pre-and post-operam conditions. Thanks to the development of a site-specific methodology, aimed to the quantification of the artificial infiltration rate, and after some years of monitoring controls of the hydrological and hydrogeological regimes, it is now possible to evaluate the extent and the rate of the recharge effects in groundwater due to ramps realization. The monitoring plan will be continued in the medium-long term. Some innovative approaches, based for example on the use of groundwater temperature measurements as recharge tracer, will help to validate the preliminary results