Bioremediation of Hexavalent Chromium—A Few Significant Site Histories in Italy

In Lombardy (Italy), about 25% of the sites ranked in the Regional Plan of Contaminated Sites are affected by Cr(VI) in groundwater and/or soil. Therefore innovative sustainable remediation techniques are under investigation, with pilot- or full-scale applications. In situ bioremediation has a significant role in the remediation techniques for its general sustainability in terms of environmental impact and costs. However, while organics can be mineralized, inorganics can only change their oxidation state, hopefully reducing their toxicity and mobility in the environment. Various patented products were used at five polluted sites in order to reduce Cr(VI) to Cr(III) via bio-induced reduction, bio-reduction and bioimmobilization. The experience pointed out that Cr(VI) concentration in groundwater can be significantly reduced (up to three order of magnitudes), but the unsaturated zone should be treated as well in order to solve the problem definitely. Soil heterogeneity is a critical issue and mixtures usually have to be injected at different depths. Iron, manganese and sulphate side-contamination can result in groundwater after injections

Five-Year Vapor Monitoring for Risk Management at a Hydrocarbon-Polluted Site

Soil remediation (excavation and off site disposal) was partially carried out in 2005 at a site in Milan (Italy), leaving a residual volume of soil polluted with petroleum-derived hydrocarbons. Indoor air, outdoor air, crawl-space air and soil gas samplings have been carried out since January 2009. In March 2011 the monitoring network was upgraded to its final configuration (18 indoor, 7 outdoor and 4 crawl-space sampling locations, 60 soil gas probes at four different depths from ground surface); after that, one monitoring campaign a season was performed till November 2013, fractionating hydrocarbons according to a modified version of the Massachusetts Department of Environmental Protection approach. In order to permanently keep risk below acceptable levels, a mitigation system of the contaminated source was installed in December 2013 and it is still working. Three monitoring campaigns of ambient air have been performed since then. Although not strictly necessary in terms of time-averaged health risk, the mitigation system allowed to extract significant amounts of mono- and light poly-cyclic aromatic hydrocarbons. This has helped manage worries about future uncontrolled exposure of people working at the site

In Situ Aerobic Biostimulation of Groundwater at a National Priority Site in Italy

Sarroch plant (CA, Italy) is an industrial area listed in the Italian Priority List of polluted sites. Pollution in groundwater has been addressed thanks to the design of a remediation action based on the aerobic biodegradation of petroleum hydrocarbons (predominantly mono-aromatic and short-chain aliphatic hydrocarbons) promoted by the injection of oxygen-releasing compounds. The feasibility of biostimulation at the site was preliminary assessed by means of laboratory tests. The direct push injection of the product has been foreseen at 2800 points, distributed along multiple lines perpendicular to the groundwater flow direction, over a total length of approximately 8 km and a total area of 90 hectares. According to the pollutant concentration measured in the different zones of the site, a different number of injection campaigns and injection frequency has been scheduled (3 to 10 campaigns, every 5 to 12 months). The estimated cost for the bioremediation action is 23 million Euros. Compared to the previous project approved in 2010, including a seafront physical barrier and groundwater circulation wells – in situ well stripping, the in situ injection of the oxygen-releasing compounds is an improvement toward a quicker, more effective and sustainable remediation of groundwater at the site. In view of all this, in 2017 the public authorities approved the variant of the project

Pollutants in Groundwater

Groundwater contamination generically refers to modifications in biological, physical or chemical characteristics (e.g., salinity, temperature, etc.), the presence of undesirable solutes at significant concentrations, or radioactivity. It may be: (i) of natural origin, (ii) the result of human activity; or (iii) a combination of the previous two. Naturally occurring processes, such as decomposition of organic material in soils or leaching of mineral deposits, can result in increased concentrations of several substances such as manganese, sulphate, chloride, organic matter, fluoride, arsenic, nitrate, selenium, uranium, and radon. Sources of groundwater contamination due to human activities are widespread and include diffuse sources as well as point-sources of pollution, such as land application of animal manure containing contaminants (e.g., veterinary pharmaceuticals) and agrochemicals in agriculture, leakages from sewers or sanitation systems, from waste disposal sites, landfills, underground storage tanks and pipelines, and accidental spills in mining, industry, traffic, health care facilities and military sites. The exploitation of petroleum products and the development of the industrial chemistry have given rise to a large number of organic chemicals, many of which are found in the environment. Various studies have shown that anthropogenic chemicals such as pesticides, pharmaceuticals and personal care products, industrial chemicals, and fuel additives occur in groundwater. U.S. Geological Survey (USGS) investigations have assessed the occurrence, distribution, and benchmark exceedance of various contaminants in water from public-supply wells and domestic wells, including pesticides, volatile organic compounds, pesticides and nitrate. Chemical mixtures were frequently detected, often with concentrations of individual contaminants approaching human-health benchmarks. Chemical mixtures that most frequently occurred and had the greatest potential toxicity were composed of arsenic, strontium, uranium, radon, and nitrate. Many organic chemicals are known to have potential human health impacts, and some of these may occur in groundwater at relevant concentrations. The list of those for which guideline values and national quality standards have been developed has been continually extended and revised. Among these: mono-aromatic hydrocarbons (benzene, toluene, ethylbenzene and xylenes - BTEX), volatile chlorinated hydrocarbons (tetrachloroethene - PCE, trichloroethene - TCE), and pesticides. This chapter focuses on chemical substances that have reasonable potential to contaminate groundwater and have human health impacts. It provides information about: i) the major sources of pollution; ii) inorganic contaminants, iii) organic contaminants; and iv) emerging issues

Emerging contaminants in sediments: a review

Emerging Contaminants (ECs) are chemicals for which new concerns have recently raised in terms of occurrence, fate, adverse effects on human health and the environment. ECs include pharmaceuticals, nanomaterials, compounds used in personal care products, plastics, pesticides and flame retardants, and compounds with a large variety of uses (e.g., phenolic and perfluorinated compounds, chlorinated paraffins, etc.). The EU Water Framework Directive 2013/39/EU deals with the status of water bodies and reports an updated list of priority substances. Some of these (e.g., nonylphenols, di(2-ethylhexyl)phthalate DEHP, perfluorooctane sulfonate PFOS, hexabromocyclododecanes, polybrominated diphenyl ethers, etc.) are emerging contaminants with high affinity towards suspended solids and sediments, due to their physicochemical properties (e.g., Koc value, etc.). The review focuses on this group of pollutants, reporting about the occurrence and distribution in sediments and biota, bioaccumulation and ecotoxicity, and the target or limit values that have been set in order to protect the aquatic environment and the human health

Design of permeable reactive barriers and examples of full scale treatments

Permeable reactive barriers (PRBs) are innovative technologies for the in situ remediation of contaminated groundwater. The technology involves the emplacement, into an excavated zone of the aquifer across the flow path of the contaminated groundwater, of a "reactive" filling material permeable to groundwater to intercept and treat the contaminants as the plume flows through under the influence of the natural hydraulic gradient. A wide range of materials are currently available. Some of them remove contaminants through non-destructive mechanisms, such as precipitation, sorption or cation exchange (also promoted by geochemistry modifications in the treatment zone), other through destructive mechanisms, such as abiotic degradation or biological degradation (in biobarriers). The choice among these is primarily based on the contaminant to remove and the abatement required, but the hydrogeological and the biogeochemical conditions of the aquifer may have great influence as well. Sometimes, concurrently mechanisms acts in removing the pollutants. Multilayer barrier systems can be developed in order to treat groundwater affected by different kinds of pollutants

State of the Art on Contaminated Sediments in Italy

Italy has about 7900 km of coastline, which is densely populated and has a strategic role for the national economy. The marine areas facing the coasts have often heavily polluted sediments. No official data are available about the amount dredged annually. Unfortunately, the laws pertaining to the topic are quite numerous and tangle the management of the dredged materials. At some sites, in situ sediments are classified according to the pollutant concentrations, resulting in different requirements, remediation priorities or different management options. At other sites, sediments are also checked from the ecotoxicological point of view. Treatments and/or reuse options (landfarming, phytoremediation, supercritical water extraction, electrokinetics, sandy fraction recovery, extraction of metallurgical silicon, and reuse of sediments for cementitious mixtures) are being investigated in few research projects involving Italian/foreign universities or research centers, national/international private companies and, in most cases, public authorities

Sustainable Remediation: Which Approach Shall I Use?

Sustainability in remediation of contaminated sites is a recent concept that aims at having a holistic approach capable to assess the global impacts of remediation at the environmental, economic and social levels. A common definition and guidelines shared at international level are still lacking and various approaches and tools are used. A "green remediation" approach is usually based on: i) the environmental footprint analysis (EFA), which can be performed with tools such as SEFA, SRT or SiteWise, or ii) a life cycle assessment (LCA), for which SimaPro is the most used tool, though not specific for cleanup purposes. A sustainable remediation process should also consider economic and social issues. As far as costs are concerned, the available tools include RACER and REC. No tools are available to quantify social benefit, which might include commercial, health or education services, increase in local occupation or real estate values

Uso di sottoprodotti dell'industria alimentare per la riduzione in situ di cromo esavalente in acque di falda

Tra le tecnologie innovative di risanamento in situ da Cr(VI) nelle acque di falda, sono in studio processi di riduzione bio-indotta (o " biodegradazione indiretta"), ossia processi ove viene promossa la riduzione del Cr(VI) mediante la generazione di un ambiente fortemente riducente via iniezione di substrati organici che sono prontamente degradati dai microrganismi eterotrofi presenti nell'acquifero. In questo lavoro sono presentate le prove condotte a scala di laboratorio con l'obiettivo di investigare il comportamento di due differenti substrati organici derivanti dall'industria alimentare (permeato di siero di latte, a 5 mg/l, e residui di lavorazione della birra, a 300 mg COD/l), in termini di abbattimento dell'inquinante dalle acque di falda e di cinetica del processo, anche in funzione della concentrazione iniziale di Cr(VI) (5000 e 10000 g/l). Le prove hanno messo in luce che fattori importanti nella rimozione di Cr(VI) in falda con tecniche di biodegradazione indiretta sono la concentrazione di Cr(VI) all'avvio del trattamento e la disponibilità di Fe(II) per la coprecipitazione del Cr(III). Il processo di precipitazione della forma chimica ridotta dell'elemento non è istantanea

Trattamento bioelettochimico di acque di falda contaminate da cromo esavalente

I tradizionali trattamenti di bioremediation in situ, in genere, prevedono l’iniezione di nutrienti e/o accettori/donatori di elettroni per favorire la biodegradazione degli inquinanti. Nei trattamenti bioelettrochimici (BioElectrochemical Systems - BESs), si forniscono accettori/donatori di elettroni solidi (elettrodi) su cui si sviluppano biofilm elettrochimicamente attivi, in grado di catalizzare la trasformazione dei contaminanti, senza l’aggiunta di agenti chimici esterni. Il trasferimento di elettroni tra batteri ed elettrodi, e viceversa, genera un segnale elettrico che permette di monitorare in tempo reale il trattamento, offrendo un ulteriore vantaggio rispetto ai trattamenti tradizionali. Nel presente studio è stata investigata a scala di laboratorio la trattabilità in BES di acque di falda contaminate da cromo esavalente. Allo scopo, si è utilizzato un sistema bioelettrochimico a doppia camera (MEC -0,5V), in cui un biocatodo in grafite ha operato a -0.5 V (vs Ag/AgCl). Parallelamente sono stati allestiti un sistema non inoculato polarizzato (ABI -0,5 V), un sistema con circuito aperto (OC) e un sistema non inoculato con circuito aperto (AbiOC). I risultati hanno dimostrato come il Cr(VI) disciolto sia diminuito del 93% in MEC -0,5 V rispetto al 60% in ABI e OC. La comunità catodica in MEC -0,5 V si è arricchita di Moheibacter, Nitrobacter e Truepera