Bioremediation of PAHs - Limitations and soultions

Introduction 1.1 Occurrence of polycyclic aromatic hydrocarbons (PAH) in the environment Worldwide industrial and agricultural developments have released a large number of natural and synthetic hazardous compounds into the environment due to careless waste disposal, illegal waste dumping and accidental spills. As a result, there are numerous sites in the world that require cleanup of soils and groundwater. Polycyclic aromatic hydrocarbons (PAHs) are one of the major groups of these contaminants (Da Silva et al., 2003). PAHs constitute a diverse class of organic compounds consisting of two or more aromatic rings with various structural configurations (Prabhu and Phale, 2003). Being a derivative of benzene, PAHs are thermodynamically stable. In addition, these chemicals tend to adhere to particle surfaces, such as soils, because of their low water solubility and strong hydrophobicity, and this results in greater persistence under natural conditions. This persistence coupled with their potential carcinogenicity makes PAHs problematic environmental contaminants (Cerniglia, 1992; Sutherland, 1992). PAHs are widely found in high concentrations at many industrial sites, particularly those associated with petroleum, gas production and wood preserving industries (Wilson and Jones, 1993). 1.2 Remediation technologies Conventional techniques used for the remediation of soil polluted with organic contaminants include excavation of the contaminated soil and disposal to a landfill or capping - containment - of the contaminated areas of a site. These methods have some drawbacks. The first method simply moves the contamination elsewhere and may create significant risks in the excavation, handling and transport of hazardous material. Additionally, it is very difficult and increasingly expensive to find new landfill sites for the final disposal of the material. The cap and containment method is only an interim solution since the contamination remains on site, requiring monitoring and maintenance of the isolation barriers long into the future, with all the associated costs and potential liability. A better approach than these traditional methods is to completely destroy the pollutants, if possible, or transform them into harmless substances. Some technologies that have been used are high-temperature incineration and various types of chemical decomposition (for example, base-catalyzed dechlorination, UV oxidation). However, these methods have significant disadvantages, principally their technological complexity, high cost , and the lack of public acceptance. Bioremediation, on the contrast, is a promising option for the complete removal and destruction of contaminants. 1.3 Bioremediation of PAH contaminated soil & groundwater Bioremediation is the use of living organisms, primarily microorganisms, to degrade or detoxify hazardous wastes into harmless substances such as carbon dioxide, water and cell biomass Most PAHs are biodegradable unter natural conditions (Da Silva et al., 2003; Meysami and Baheri, 2003) and bioremediation for cleanup of PAH wastes has been extensively studied at both laboratory and commercial levels- It has been implemented at a number of contaminated sites, including the cleanup of the Exxon Valdez oil spill in Prince William Sound, Alaska in 1989, the Mega Borg spill off the Texas coast in 1990 and the Burgan Oil Field, Kuwait in 1994 (Purwaningsih, 2002). Different strategies for PAH bioremediation, such as in situ , ex situ or on site bioremediation were developed in recent years. In situ bioremediation is a technique that is applied to soil and groundwater at the site without removing the contaminated soil or groundwater, based on the provision of optimum conditions for microbiological contaminant breakdown.. Ex situ bioremediation of PAHs, on the other hand, is a technique applied to soil and groundwater which has been removed from the site via excavation (soil) or pumping (water). Hazardous contaminants are converted in controlled bioreactors into harmless compounds in an efficient manner. 1.4 Bioavailability of PAH in the subsurface Frequently, PAH contamination in the environment is occurs as contaminants that are sorbed onto soilparticles rather than in phase (NAPL, non aqueous phase liquids). It is known that the biodegradation rate of most PAHs sorbed onto soil is far lower than rates measured in solution cultures of microorganisms with pure solid pollutants (Alexander and Scow, 1989; Hamaker, 1972). It is generally believed that only that fraction of PAHs dissolved in the solution can be metabolized by microorganisms in soil. The amount of contaminant that can be readily taken up and degraded by microorganisms is defined as bioavailability (Bosma et al., 1997; Maier, 2000). Two phenomena have been suggested to cause the low bioavailability of PAHs in soil (Danielsson, 2000). The first one is strong adsorption of the contaminants to the soil constituents which then leads to very slow release rates of contaminants to the aqueous phase. Sorption is often well correlated with soil organic matter content (Means, 1980) and significantly reduces biodegradation (Manilal and Alexander, 1991). The second phenomenon is slow mass transfer of pollutants, such as pore diffusion in the soil aggregates or diffusion in the organic matter in the soil. The complex set of these physical, chemical and biological processes is schematically illustrated in Figure 1. As shown in Figure 1, biodegradation processes are taking place in the soil solution while diffusion processes occur in the narrow pores in and between soil aggregates (Danielsson, 2000). Seemingly contradictory studies can be found in the literature that indicate the rate and final extent of metabolism may be either lower or higher for sorbed PAHs by soil than those for pure PAHs (Van Loosdrecht et al., 1990). These contrasting results demonstrate that the bioavailability of organic contaminants sorbed onto soil is far from being well understood. Besides bioavailability, there are several other factors influencing the rate and extent of biodegradation of PAHs in soil including microbial population characteristics, physical and chemical properties of PAHs and environmental factors (temperature, moisture, pH, degree of contamination). Figure 1: Schematic diagram showing possible rate-limiting processes during bioremediation of hydrophobic organic contaminants in a contaminated soil-water system (not to scale) (Danielsson, 2000). 1.5 Increasing the bioavailability of PAH in soil Attempts to improve the biodegradation of PAHs in soil by increasing their bioavailability include the use of surfactants , solvents or solubility enhancers.. However, introduction of synthetic surfactant may result in the addition of one more pollutant. (Wang and Brusseau, 1993).A study conducted by Mulder et al. showed that the introduction of hydropropyl-ß-cyclodextrin (HPCD), a well-known PAH solubility enhancer, significantly increased the solubilization of PAHs although it did not improve the biodegradation rate of PAHs (Mulder et al., 1998), indicating that further research is required in order to develop a feasible and efficient remediation method. Enhancing the extent of PAHs mass transfer from the soil phase to the liquid might prove an efficient and environmentally low-risk alternative way of addressing the problem of slow PAH biodegradation in soil.

Uno Two Drei: la televisione nella promozione linguistica per i giovani. Un caso italiano nel contesto europeo.

The aim of this work is to assess the effectiveness of a project carried out in the Autonomous Province of Trento to promote language learning among young people. The project consisted in a television quiz show featuring games in Italian, English and German. Eight classes from five high schools took part in the game show, which was aired between November 2014 and January 2015 by the local channel Trentino TV. Since multilingualism has been part of the European Union policy, legislation and practices for many decades, the first chapter of this dissertation offers an overview of the main EU language education policies which seek to promote language learning among all citizens. It then focuses on the commitment of the EU and its member States to find new strategies to show the benefits of language learning outside formal education, also using both old and new media. Some TV and radio shows on multilingualism broadcast in Italy and in other EU countries are also briefly described. The second chapter is devoted to Uno Two Drei, the quiz show created by the Autonomous Province of Trento and Trentino TV to promote the learning of English and German among students while enhancing their personal growth and development. The role of everyone involved in the project is outlined, as well as the concept and planning phases and the realization stage. The third chapter focuses largely on the impacts of the initiative on the target group, namely 17-year-old students. Opinions of the participants were first collected in January, when a final meeting was held between the organizers and the schools. Since the researcher has managed the German part of the project, in the following months a questionnaire was administered to the 48 students who played in the German team and to their teachers as well. From both the meeting and the questionnaires it has emerged that the main goals of the initiative were achieved: generally speaking, students have been motivated to study languages and learn new things, the bonds between them have been strengthened and their sense of solidarity has been enhanced.

Il sottotitolaggio per i film festival: due esperienze pratiche

This dissertation aims to examine the field of film festival subtitling by means of the analysis of two subtitling experiences. These experiences will be approached both on a methodological and on a practical level in order to analyse how subtitlers put theory into practice. This approach will also help underline the existing differences in work methodology as far as different work experiences are concerned. The subtitling experiences examined in this dissertation are part of my internships as a subtitler in two Italian film festivals, namely “Umbria Film Festival” and “900 Fest”. In this dissertation, I chose to focus on the subtitling of two of the audiovisual products I translated. These products are a German documentary titled Befreier und Befreite and a Danish fiction film titled Stille Hjerte. This dissertation is divided into five chapters. Chapter 1 describes audiovisual translation at its most theoretical level, focusing on subtitling criteria and strategies. Chapter 2 examines the concept of film translation, focusing on the distinctive features of documentary translation as a specific genre. This chapter also presents the concept of film festival and provides information concerning the translation policies of festivals. Chapter 3 presents the festivals I worked for and details my internship experiences. Chapter 4 focuses on the German documentary and proposes a number of solutions to its main translation problems. Chapter 5 focuses on the Danish film and offers solutions to its translation problems. At the end of the dissertation, I will provide some comments on my internship experiences as well as on the practice of film festival subtitling.