Continuous-Flow Magnetic Separation with Permanent Magnets for Water Treatment

More efficient water treatment technologies would decrease the water bodies’ pollution and the actual intake of water resource. The aim of this thesis is an in-depth analysis of the magnetic separation of pollutants from water by means of a continuous-flow magnetic filter subjected to a field gradient produced by permanent magnets. This technique has the potential to improve times and efficiencies of both urban wastewater treatment plants and drinking water treatment plants. It might also substitute industrial wastewater treatments. This technique combines a physico-chemical phase of adsorption and a magnetic phase of filtration, having the potential to bond magnetite with any conventional adsorbent powder. The removal of both Magnetic Activated Carbons (MACs) and zeolite-magnetite mix with the addition of a coagulant was investigated. Adsorption tests of different pollutants (surfactants, endocrine disruptors, Fe(III), Mn(II), Ca(II)) on these adsorbents were also performed achieving good results. The numerical results concerning the adsorbent removals well reproduced the experimental ones obtained from two different experimental setups. In real situations the treatable flow rates are up to 90 m3/h (2000 m3/d).

Aerobic biodegradation of chlorinated solvents and plastics in batch and continuous-flow bioreactors: process development, and identification of suitable chemical pre-Treatments

The purpose of the first part of the research activity was to develop an aerobic cometabolic process in packed bed reactors (PBR) to treat real groundwater contaminated by trichloroethylene (TCE) and 1,1,2,2-tetrachloroethane (TeCA). In an initial screening conducted in batch bioreactors, different groundwater samples from 5 wells of the contaminated site were fed with 5 growth substrates. The work led to the selection of butane as the best growth substrate, and to the development and characterization from the site’s indigenous biomass of a suspended-cell consortium capable to degrade TCE with a 90 % mineralization of the organic chlorine. A kinetic study conducted in batch and continuous flow PBRs and led to the identification of the best carrier. A kinetic study of butane and TCE biodegradation indicated that the attached-cell consortium is characterized by a lower TCE specific degredation rates and by a lower level of mutual butane-TCE inhibition. A 31 L bioreactor was designed and set up for upscaling the experiment. The second part of the research focused on the biodegradation of 4 polymers, with and with-out chemical pre-treatments: linear low density polyethylene (LLDPE), polyethylene (PP), polystyrene (PS) and polyvinyl chloride (PVC). Initially, the 4 polymers were subjected to different chemical pre-treatments: ozonation and UV/ozonation, in gaseous and aqueous phase. It was found that, for LLDPE and PP, the coupling UV and ozone in gas phase is the most effective way to oxidize the polymers and to generate carbonyl groups on the polymer surface. In further tests, the effect of chemical pretreatment on polyner biodegrability was studied. Gas-phase ozonated and virgin polymers were incubated aerobically with: (a) a pure strain, (b) a mixed culture of bacteria; and (c) a fungal culture, together with saccharose as a co-substrate.

Continuos Flow Single Cell Separation into Open Microwell Arrays

A novel design based on electric field-free open microwell arrays for the automated continuous-flow sorting of single or small clusters of cells is presented. The main feature of the proposed device is the parallel analysis of cell-cell and cell-particle interactions in each microwell of the array. High throughput sample recovery with a fast and separate transfer from the microsites to standard microtiter plates is also possible thanks to the flexible printed circuit board technology which permits to produce cost effective large area arrays featuring geometries compatible with laboratory equipment. The particle isolation is performed via negative dielectrophoretic forces which convey the particles’ into the microwells. Particles such as cells and beads flow in electrically active microchannels on whose substrate the electrodes are patterned. The introduction of particles within the microwells is automatically performed by generating the required feedback signal by a microscope-based optical counting and detection routine. In order to isolate a controlled number of particles we created two particular configurations of the electric field within the structure. The first one permits their isolation whereas the second one creates a net force which repels the particles from the microwell entrance. To increase the parallelism at which the cell-isolation function is implemented, a new technique based on coplanar electrodes to detect particle presence was implemented. A lock-in amplifying scheme was used to monitor the impedance of the channel perturbed by flowing particles in high-conductivity suspension mediums. The impedance measurement module was also combined with the dielectrophoretic focusing stage situated upstream of the measurement stage, to limit the measured signal amplitude dispersion due to the particles position variation within the microchannel. In conclusion, the designed system complies with the initial specifications making it suitable for cellomics and biotechnology applications.

Modeling hydrothermal system: deriving observables and hydrothermal instability in volcanic and non-volcanic setting

Hydrothermal fluids are a fundamental resource for understanding and monitoring volcanic and non-volcanic systems. This thesis is focused on the study of hydrothermal system through numerical modeling with the geothermal simulator TOUGH2. Several simulations are presented, and geophysical and geochemical observables, arising from fluids circulation, are analyzed in detail throughout the thesis. In a volcanic setting, fluids feeding fumaroles and hot spring may play a key role in the hazard evaluation. The evolution of the fluids circulation is caused by a strong interaction between magmatic and hydrothermal systems. A simultaneous analysis of different geophysical and geochemical observables is a sound approach for interpreting monitored data and to infer a consistent conceptual model. Analyzed observables are ground displacement, gravity changes, electrical conductivity, amount, composition and temperature of the emitted gases at surface, and extent of degassing area. Results highlight the different temporal response of the considered observables, as well as the different radial pattern of variation. However, magnitude, temporal response and radial pattern of these signals depend not only on the evolution of fluid circulation, but a main role is played by the considered rock properties. Numerical simulations highlight differences that arise from the assumption of different permeabilities, for both homogeneous and heterogeneous systems. Rock properties affect hydrothermal fluid circulation, controlling both the range of variation and the temporal evolution of the observable signals. Low temperature fumaroles and low discharge rate may be affected by atmospheric conditions. Detailed parametric simulations were performed, aimed to understand the effects of system properties, such as permeability and gas reservoir overpressure, on diffuse degassing when air temperature and barometric pressure changes are applied to the ground surface. Hydrothermal circulation, however, is not only a characteristic of volcanic system. Hot fluids may be involved in several mankind problems, such as studies on geothermal engineering, nuclear waste propagation in porous medium, and Geological Carbon Sequestration (GCS). The current concept for large-scale GCS is the direct injection of supercritical carbon dioxide into deep geological formations which typically contain brine. Upward displacement of such brine from deep reservoirs driven by pressure increases resulting from carbon dioxide injection may occur through abandoned wells, permeable faults or permeable channels. Brine intrusion into aquifers may degrade groundwater resources. Numerical results show that pressure rise drives dense water up to the conduits, and does not necessarily result in continuous flow. Rather, overpressure leads to new hydrostatic equilibrium if fluids are initially density stratified. If warm and salty fluid does not cool passing through the conduit, an oscillatory solution is then possible. Parameter studies delineate steady-state (static) and oscillatory solutions.

Biodegradazione aerobica cometabolica di cloroformio: studio di fattibilità in reattori a biomassa adesa

Chlorinated Aliphatic Hydrocarbons (CAHs) are widespread wastewater and groundwater contaminants and represent a real danger for human health and environment. This research is related to the biodegradation technologies to treat chlorinated hydrocarbons. In particular the study of this thesis is focused on chloroform cometabolism by a butane-grown aerobic pure culture (Rhodococcus aetherovorans BCP1) in continuous-flow biofilm reactors, which are used for in-situ and on-site treatments. The work was divided in two parts: in the first one an experimental study has been conducted in two packed-bed reactors (PBRs) for a period of 370 days; in the second one a fluid dynamics and kinetic model has been developed in order to simulate the experimental data concerning a previous study made in a 2-m continuous-flow sand-filled reactor. The goals of the first study were to obtain preliminary information on the feasibility of chloroform biodegradation by BCP1 under attached-cell conditions and to evaluate the applicability of the pulsed injection of growth substrate and oxygen to biofilm reactors. The pulsed feeding represents a tool to control the clogging and to ensure a long bioreactive zone. The operational conditions implemented in the PBRs allowed the attainment of a 4-fold increase of the ratio of chloroform degraded to substrate consumed, in comparison with the phase of continuous substrate supply. The second study was aimed at identifying guidelines for optimizing the oxygen/substrate supply schedule, developing a reliable model of chloroform cometabolism in porous media. The tested model led to a suitable interpretation of the experimental data as long as the ratio of CF degraded to butane consumed was ≤ 0.27 mgchloroform /mgbutane. A long-term simulation of the best-performing schedule of pulsed oxygen/substrate supply indicated the attainment of a steady state condition characterized by unsatisfactory bioremediation performances, evidencing the need for a further optimization of the pulsed injection technique.

Speleogenesis and secondary cave minerals in quartz-sandstone and quartzite environment

The main objective of this research is to improve the comprehension of the processes controlling the formation of caves and karst-like morphologies in quartz-rich lithologies (more than 90% quartz), like quartz-sandstones and metamorphic quartzites. In the scientific community the processes actually most retained to be responsible of these formations are explained in the “Arenisation Theory”. This implies a slow but pervasive dissolution of the quartz grain/mineral boundaries increasing the general porosity until the rock becomes incohesive and can be easily eroded by running waters. The loose sands produced by the weathering processes are then evacuated to the surface through processes of piping due to the infiltration of waters from the fracture network or the bedding planes. To deal with these problems we adopted a multidisciplinary approach through the exploration and the study of several cave systems in different tepuis. The first step was to build a theoretical model of the arenisation process, considering the most recent knowledge about the dissolution kinetics of quartz, the intergranular/grain boundaries diffusion processes, the primary diffusion porosity, in the simplified conditions of an open fracture crossed by a continuous flow of undersatured water. The results of the model were then compared with the world’s widest dataset (more than 150 analyses) of water geochemistry collected till now on the tepui, in superficial and cave settings. All these studies allowed verifying the importance and the effectiveness of the arenisation process that is confirmed to be the main process responsible of the primary formation of these caves and of the karst-like superficial morphologies. The numerical modelling and the field observations allowed evaluating a possible age of the cave systems around 20-30 million of years.

The medical management after surgery for advanced heart failure

The aim of the Research of this Ph D Project is to improve the medical management after surgery for advanced heart failure, both after left ventricular assist devices (LVAD) implantation, and after heart transplantation in the long-term. Regarding heart transplantation (HTx), the Research Project is focused on diagnostics, classification, prevention and treatment of cardiac allograft vasculopathy (CAV), and on treatment of post-HTx cancers; the results are presented in the first part of this Thesis. In particular, the main aspect investigated are the prognostic role of information derived from coronary angiography, coronary tomography and intravascular ultrasound, and the different sensitivity of these techniques in predicting outcomes and in diagnosing CAV. Moreover, the role of mTOR inhibitors on CAV prevention or treatment is investigated, both alone and in combination with different anti-CMV prevention strategies, as well as the impact of mTOR inhibitors on clinical outcomes in the long term. Regarding LVAD, the main focus is on the role of transthoracic echocardiography in the management of patients with a continuous-flow, centrifugal, intrapericardial pump (HVAD, Heartware); this section is reported in the second part of this Thesis. The main aspects investigated are the use of echocardiography in patients with HVAD device and its interaction with the information derived from pump curves' analysis in predicting aortic valve opening status, a surrogate of the condition of support provided by the LVAD.