The work undertaken during the PhD was aimed at evaluating alternative bioremediation methods, trying to focus on biological and low environmental impact techniques. At first, the main purpose was to create a robust and replicable method, capable to break-down priority pollutants for the environment, using natural microorganisms or their consortia. Was decided to study the degradation of a particular class of priority micro-pollutants, the Polycyclic Aromatic Hydrocarbons (PAHs), and evaluate the bioremediation capabilities of a white-rot fungus, the Pleurotus sajor caju, and a selected bacteria consortium (BULAB 5738). PAHs are organic compounds, composed of multiple aromatic rings, that persist in the environment because they are very stable due to their molecular structure and therefore are difficult to be attacked by microorganisms present in nature. The study of PAHs and their bio-degradation is also motivated by the difficulties encountered in the scientific literature, as appears from the current state of the art. As far as this study is concerned, the use of 'white rot' fungi and selected bacterial consortia is a valid and real opportunity for the degradation of many toxic molecules, including PAHs. Another part of the PhD work was dedicated to the study of microalgae’s degradation capabilities, with particular regard to the potential of these microorganisms to remove nutrients from waste water. The microalgae are often studied for energy purposes and for high added-value molecules production; in this work the focus was on their capabilities on nitrogen and phosphorus removal. These compounds are present on wastewater and on aquacolture processes that can be treated by microalgae. This alternative was considered feasible in the short term, in terms of applicability and practical results. Furthermore, the capacity of Nannochloropsis oculata to use high loads of nitrogen and phosphorus as a source of nourishment, has been explored, in order to remove these pollutants from the wastewater. The Nannochloropsis oculata was chosen for its ability to survive in adverse conditions and for its relatively fast growth velocity, if compared to other photosynthetic microorganisms. Design of Experimental approach was used for all the experimental campaigns, to maximize the obtained information and minimize the number of experiments. Thanks to the statistical analysis it was possible to obtain significant information about single and multiple effect, that influence the studied process. Both experiments with the Pleurotus s.c. and the bacterial consortium showed how they tolerate and break-down the selected PAHs. The main differences lay on the dynamics of growth and on the timing of the two different kind of microorganism, as well as the different pathways of degradation process. In particular, the fungi growth is slower than the one of bacterial consortium, but both are able to degrade the selected pollutants. As far as the selected microalgal species are concerned, the Nannochloropsis o. showed a good removal capacity for nitrogen, evaluated as nitrates and urea, obtaining the complete degradation, even on high loads up to concentrations of 1000 mg/l of nitrogen, as a nitrate.
The work undertaken during the PhD was aimed at evaluating alternative bioremediation methods, trying to focus on biological and low environmental impact techniques. At first, the main purpose was to create a robust and replicable method, capable to break-down priority pollutants for the environment, using natural microorganisms or their consortia. Was decided to study the degradation of a particular class of priority micro-pollutants, the Polycyclic Aromatic Hydrocarbons (PAHs), and evaluate the bioremediation capabilities of a white-rot fungus, the Pleurotus sajor caju, and a selected bacteria consortium (BULAB 5738). PAHs are organic compounds, composed of multiple aromatic rings, that persist in the environment because they are very stable due to their molecular structure and therefore are difficult to be attacked by microorganisms present in nature. The study of PAHs and their bio-degradation is also motivated by the difficulties encountered in the scientific literature, as appears from the current state of the art. As far as this study is concerned, the use of 'white rot' fungi and selected bacterial consortia is a valid and real opportunity for the degradation of many toxic molecules, including PAHs. Another part of the PhD work was dedicated to the study of microalgae’s degradation capabilities, with particular regard to the potential of these microorganisms to remove nutrients from waste water. The microalgae are often studied for energy purposes and for high added-value molecules production; in this work the focus was on their capabilities on nitrogen and phosphorus removal. These compounds are present on wastewater and on aquacolture processes that can be treated by microalgae. This alternative was considered feasible in the short term, in terms of applicability and practical results. Furthermore, the capacity of Nannochloropsis oculata to use high loads of nitrogen and phosphorus as a source of nourishment, has been explored, in order to remove these pollutants from the wastewater. The Nannochloropsis oculata was chosen for its ability to survive in adverse conditions and for its relatively fast growth velocity, if compared to other photosynthetic microorganisms. Design of Experimental approach was used for all the experimental campaigns, to maximize the obtained information and minimize the number of experiments. Thanks to the statistical analysis it was possible to obtain significant information about single and multiple effect, that influence the studied process. Both experiments with the Pleurotus s.c. and the bacterial consortium showed how they tolerate and break-down the selected PAHs. The main differences lay on the dynamics of growth and on the timing of the two different kind of microorganism, as well as the different pathways of degradation process. In particular, the fungi growth is slower than the one of bacterial consortium, but both are able to degrade the selected pollutants. As far as the selected microalgal species are concerned, the Nannochloropsis o. showed a good removal capacity for nitrogen, evaluated as nitrates and urea, obtaining the complete degradation, even on high loads up to concentrations of 1000 mg/l of nitrogen, as a nitrate.
IMPLEMENTAZIONE DI TECNICHE DI BIOREMEDIATION PER L’AMBIENTE
SAIU, GIULIANO
2017-03-10
Abstract
The work undertaken during the PhD was aimed at evaluating alternative bioremediation methods, trying to focus on biological and low environmental impact techniques. At first, the main purpose was to create a robust and replicable method, capable to break-down priority pollutants for the environment, using natural microorganisms or their consortia. Was decided to study the degradation of a particular class of priority micro-pollutants, the Polycyclic Aromatic Hydrocarbons (PAHs), and evaluate the bioremediation capabilities of a white-rot fungus, the Pleurotus sajor caju, and a selected bacteria consortium (BULAB 5738). PAHs are organic compounds, composed of multiple aromatic rings, that persist in the environment because they are very stable due to their molecular structure and therefore are difficult to be attacked by microorganisms present in nature. The study of PAHs and their bio-degradation is also motivated by the difficulties encountered in the scientific literature, as appears from the current state of the art. As far as this study is concerned, the use of 'white rot' fungi and selected bacterial consortia is a valid and real opportunity for the degradation of many toxic molecules, including PAHs. Another part of the PhD work was dedicated to the study of microalgae’s degradation capabilities, with particular regard to the potential of these microorganisms to remove nutrients from waste water. The microalgae are often studied for energy purposes and for high added-value molecules production; in this work the focus was on their capabilities on nitrogen and phosphorus removal. These compounds are present on wastewater and on aquacolture processes that can be treated by microalgae. This alternative was considered feasible in the short term, in terms of applicability and practical results. Furthermore, the capacity of Nannochloropsis oculata to use high loads of nitrogen and phosphorus as a source of nourishment, has been explored, in order to remove these pollutants from the wastewater. The Nannochloropsis oculata was chosen for its ability to survive in adverse conditions and for its relatively fast growth velocity, if compared to other photosynthetic microorganisms. Design of Experimental approach was used for all the experimental campaigns, to maximize the obtained information and minimize the number of experiments. Thanks to the statistical analysis it was possible to obtain significant information about single and multiple effect, that influence the studied process. Both experiments with the Pleurotus s.c. and the bacterial consortium showed how they tolerate and break-down the selected PAHs. The main differences lay on the dynamics of growth and on the timing of the two different kind of microorganism, as well as the different pathways of degradation process. In particular, the fungi growth is slower than the one of bacterial consortium, but both are able to degrade the selected pollutants. As far as the selected microalgal species are concerned, the Nannochloropsis o. showed a good removal capacity for nitrogen, evaluated as nitrates and urea, obtaining the complete degradation, even on high loads up to concentrations of 1000 mg/l of nitrogen, as a nitrate.
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