Ecological risk assessment for contaminated sites in Italy: Guidelines and path forward

Ecological risk assessment (ERA) is defined as an iterative process that evaluates the likelihood of adverse ecological effects resulting from exposure to one or more stressors. Although ERA is recognized as a valuable procedure to better address efforts and strategies for site remediation, in Europe a common framework for the implementation of ERA in the management of contaminated sites is lacking. In Italy, there are no legally binding provisions regulating the direct assessment of potential likelihood of ecological risks. In this context, the main objective of this article was to develop a guideline to facilitate ERA application in support of an effective and sustainable management of contaminated sites in Italy and to facilitate a multistakeholder dialogue. The work was based on a critical review of existing ERA guidelines in the international context, as well as other regulatory documents and technical approaches dealing with the evaluation of ecological effects of chemical contaminants in different environmental compartments. Approaches and tools available in these documents were then used to prepare a proposed guideline for the Italian context; the proposed ERA guideline is meant to represent a flexible but robust approach that can be useful in evaluating existing data (e.g., from past investigations) as well as in the planning of site-specific investigations. To facilitate the direct application of the ERA procedure, the guideline was prepared including several templates of summary tables, checklists, and examples. The proposed ERA guideline could facilitate the decision-making process for contaminated sites with ecological values, although its application would necessarily require, at least in the initial phase, testing of its suitability to the Italian context and setting-up of a close dialogue and collaboration with local authorities and other stakeholders. Integr Environ Assess Manag 2022;00:1-7. (c) 2022 SETA

The role of physical pretreatments on the hydraulic conductivity of natural sodium bentonites

The role played by physical pretreatments applied to sodium bentonites, such as pre-hydration, pre-consolidation and pore water salt removal, has been analyzed in this technical note looking at the results of a series of hydraulic conductivity tests that have been carried out using both deionized water (DW) and a calcium chloride solution (CCS) as permeants. Moreover, the effect of the presence of needling across the bentonite layer has also been investigated. The DW and CCS have been used in order to simulate respectively the short and long-term conditions performances of bentonite based barriers (e.g. geosynthetic clay liners) for pollutant control. Given an initial pre-hydration for all the tested samples, the experimental results have pointed out that physical pretreatments, such as pre-consolidation and salt removal, can significantly influence the response of bentonite to the cation exchange phenomenon and, in turn, to its swelling behavior and hydrated fabric or microstructure of the solid skeleton. When a geosynthetic clay liner sample (GCL) and two simple basic specimens, prepared in the laboratory with the same bentonite type, are preliminarily permeated with DW and, thereafter, with CCS in order to simulate long-term conditions in the field, the hydraulic conductivity (K) tests have shown that the presence of needling in GCL sample can strongly deteriorates its performances (i.e. from K=2·10^(-11) m/s to K=7·10^(-10) m/s) whereas, the other two basic bentonite specimens, without needling, present a much less degradation (i.e. from K=2·10^(-11) m/s to K=1.2 - 1.6·10^(-10) m/s), all the other test conditions being the same. On the other hand, laboratory test results also show that the pre-consolidation process is able to greatly improves the long-term behaviour of the basic bentonite specimens (K=1.8·10^(-11) m/s referring to the CCS permeation) with negligible hydraulic conductivity variations referring to the short-term permeation phase with DW. Moreover, a specimen, further pre-treated by pore water salt removal with a cyclic squeezing process, showed in absolute the best hydraulic performances of the test series in both short and long-term conditions reaching a value of K=8·10^(-12) m/s with DW and a K=6·10^(-12) m/s in the long-term with CCS as permeant

Hybrid Forward Osmosis–Nanofiltration for Wastewater Reuse: System Design

The design of a hybrid forward osmosis−nanofiltration (FO−NF) system for the extraction of high-quality water from wastewater is presented here. Simulations were performed based on experimental results obtained in a previous study using real wastewater as the feed solution. A sensitivity analysis, conducted to evaluate the influence of different process parameters, showed that an optimum configuration can be designed with (i) an influent draw solution osmotic pressure equal to 15 bar and (ii) a ratio of influent draw solution to feed solution flow rate equal to 1.5:1. With this configuration, the simulations suggested that the overall FO−NF system can achieve up to 85% water recovery using Na2SO4 or MgCl2 as the draw solute. The modular configuration and the size of the NF stage, accommodating approximately 7000 m2 of active membrane area, was a function of the properties of the membranes selected to separate the draw solutes and water, while detailed simulations indicated that the size of the FO unit might be reduced by adopting a counter-current configuration. Experimental tests with samples of the relevant wastewater showed that Cl−- and Mg2+-based draw solutes would be associated with larger membrane fouling, possibly due to their interaction with the other substances present in the feed solution. However, the results suggest that fouling would not significantly decrease the performance of the designed system. This study contributes to the further evaluation and potential implementation of FO in water reuse systems

1,2-DCA Natural Attenuation Evaluation in Groundwater: Insight by Dual Isotope 13C/37Cl and Molecular Analysis Approach

Natural attenuation (NA) processes represent a valuable option in groundwater remediation. At a heavily 1,2-dichloroethane (1,2-DCA) contaminated site, Compound-Specific Isotope Analysis (CSIA) in combination with Biological Molecular Tools (BMTs) were implemented as a rigorous characterization approach to evaluate the occurrence of Natural Attenuation in the proximity of the source area. By the use of microcosm experiments, the potential for natural and enhanced biodegradation under anaerobic conditions was documented, following the dichloroelimination pathway. Enrichment factors of −9.1‰ and −11.3‰ were obtained for 13C while Geobacter spp. and reductive dehalogenase genes (rdhs) were identified as main site-specific biomarkers. At pilot scale, enrichments of 13.5‰ and 6.3‰ for δ13C and δ37Cl, respectively, high levels of reductive dehalogenase (rdh group VI) along with the dominance of Geobacter spp. indicated the occurrence of significant dichloroelimination processes in groundwater under anaerobic conditions. By using the site-specific enrichment factors, degradation extents over approximately 70–80% were estimated, highlighting the relevant potential of NA in 1,2-DCA degradation in the vicinity of the source area at the site. The proposed fine-tuned protocol, including CSIA and BMTs, is proven to be effective as a groundwater remediation strategy, properly assessing and monitoring NA at site scale

1,2-DCA Natural Attenuation Evaluation in Groundwater: Insight by Dual Isotope ¹³C/³⁷Cl and Molecular Analysis Approach

Natural attenuation (NA) processes represent a valuable option in groundwater remediation. At a heavily 1,2-dichloroethane (1,2-DCA) contaminated site, Compound-Specific Isotope Analysis (CSIA) in combination with Biological Molecular Tools (BMTs) were implemented as a rigorous characterization approach to evaluate the occurrence of Natural Attenuation in the proximity of the source area. By the use of microcosm experiments, the potential for natural and enhanced biodegradation under anaerobic conditions was documented, following the dichloroelimination pathway. Enrichment factors of −9.1‰ and −11.3‰ were obtained for 13C while Geobacter spp. and reductive dehalogenase genes (rdhs) were identified as main site-specific biomarkers. At pilot scale, enrichments of 13.5‰ and 6.3‰ for δ13C and δ37Cl, respectively, high levels of reductive dehalogenase (rdh group VI) along with the dominance of Geobacter spp. indicated the occurrence of significant dichloroelimination processes in groundwater under anaerobic conditions. By using the site-specific enrichment factors, degradation extents over approximately 70–80% were estimated, highlighting the relevant potential of NA in 1,2-DCA degradation in the vicinity of the source area at the site. The proposed fine-tuned protocol, including CSIA and BMTs, is proven to be effective as a groundwater remediation strategy, properly assessing and monitoring NA at site scale