Environmental and energy assessment of municipal wastewater treatment plants in Italy and Romania: A comparative study

Municipal wastewater treatment plants (MWWTPs) are essential infrastructures in any urban context, but they may be considered as a potential source of greenhouse gas (GHG) emissions and should be coherent with European Union (EU) policy on energy eciency. This study presents a sustainability evaluation of four Italian and Romanian MWWTPs in terms of energy eciency and greenhouse gas emissions using Energy Performance and Carbon Emissions Assessment and Monitoring (ECAM) tool software. The obtained results indicated that biogas recovery improved energy performances, while the largest contributions in terms of GHG emissions were in all cases caused by energy consumption and methane produced during wastewater treatment. The Romanian plants exhibited higher GHG emissions, compared to the Italian plants, mainly because of the dierent values of national conversion factors for grid electricity (0.41 kg CO2/kWh for Italy and 1.07 kg CO2/kWh for Romania). Two scenarios aimed at enhancing the overall sustainability were hypothesized, based on increasing the serviced population or energy eciency, achieving significant improvements. A sustainability assessment of MWWTPs should be adopted as a useful tool to help water utilities to introduce low-energy, low-carbon management practices as well as being useful for policy recommendations

Water footprint assessment in North Eastern region of Romania: A case study for Iasi County, Romania

Many factors affect the water consumption pattern such as growing world population, climate changes, industrial and agricultural practices, etc. The present study provides for the first time a year-to-year analysis of water use for agricultural production, domestic water supply and industrial production from a hydrological, economical and ecological perspective in the NE region of Romania. Such an assessment can provide information to facilitate an efficient allocation of water resources to different economic and environmental demands. This assessment is also considering the general economic and social context of the Iasi county as an important area within north-eastern region of Romania. In the Iasi county, the green component takes the largest share in the total water footprint of crops because of the irrigation underdeveloped infrastructure, which makes the agricultural sector vulnerable to dry periods and floods as well. A monthly comparison between the blue water footprint and blue water availability shows that water scarcity varies greatly within the year, but also between years

Environmental performance evaluation of a drinking water treatment plant: A life cycle assessment perspective

Drinking water treatment aims to avoid or minimize some risks to human health and to provide adequate water quality by removing physical, chemical and biological contaminants. However, treatment processes require increasing efforts in terms of technology, chemicals and energy inputs, which generate increased secondary environmental impacts and added water production costs. The objective of this study is to evaluate the drinking water treatment plant (DWTP) in Iasi City (Romania) by life cycle assessment (LCA) and to identify and characterize its environmental impacts. Iasi DWTP involves the following scheme: pre-oxidation (chlorine dioxide), coagulation/flocculation, sedimentation, pH correction (calcium hydroxide), rapid sand filtration, granular activated carbon filtration and disinfection (chlorine gas). LCA was performed according to the ISO 14040 standard with the support of SimaPro 8.3. software and Eco-invent 3.3 data base. Life cycle impact assessment has been performed with Recipe 1.13. Midpoint method. The life cycle inventory included the construction and operational phases. The novelty of this study was to define two additional functional units related to removing contaminants besides the traditional 1 m3 of treated water. The main contributors to impact in most categories were: the electricity consumption (25 – 95% depending on impact category) and the ferric chloride used in coagulation/flocculation (35 – 100%, depending on impact category). Life cycle impact assessment showed that the lower the pollutant concentration, the higher the specific environmental impacts will be, which prompts for further detailed analysis of water treatment plant environmental performance in at least two directions: removal of emerging contaminants (present in very low concentrations) and a more detailed analysis on the individual performance of each treatment stage

Dislocation core field. II. Screw dislocation in iron

The dislocation core field, which comes in addition to the Volterra elastic field, is studied for the screw dislocation in alpha-iron. This core field, evidenced and characterized using ab initio calculations, corresponds to a biaxial dilatation, which we modeled within the anisotropic linear elasticity. We show that this core field needs to be considered when extracting quantitative information from atomistic simulations, such as dislocation core energies. Finally, we look at how dislocation properties are modified by this core field, by studying the interaction between two dislocations composing a dipole, as well as the interaction of a screw dislocation with a carbon atom

On the incompatibility of strains and its application to mesoscopic studies of plasticity

Structural transitions are invariably affected by lattice distortions. If the body is to remain crack-free, the strain field cannot be arbitrary but has to satisfy the Saint-Venant compatibility constraint. Equivalently, an incompatibility constraint consistent with the actual dislocation network has to be satisfied in media with dislocations. This constraint can be incorporated into strain-based free energy functionals to study the influence of dislocations on phase stability. We provide a systematic analysis of this constraint in three dimensions and show how three incompatibility equations accommodate an arbitrary dislocation density. This approach allows the internal stress field to be calculated for an anisotropic material with spatially inhomogeneous microstructure and distribution of dislocations by minimizing the free energy. This is illustrated by calculating the stress field of an edge dislocation and comparing it with that of an edge dislocation in an infinite isotropic medium. We outline how this procedure can be utilized to study the interaction of plasticity with polarization and magnetization.Comment: 6 pages, 2 figures; will appear in Phys. Rev.

Threshold Phenomena under Photo Excitation of Spin-crossover Materials with Cooperativity due to Elastic Interactions

Photo-induced switching from the low-spin state to the high-spin state is studied in a model of spin-crossover materials, in which long-range interactions are induced by elastic distortions due to different molecular sizes the two spin states. At a threshold value of the light intensity we observe nonequilibrium critical behavior corresponding to a mean-field spinodal point. Finite-size scaling of the divergence of the relaxation time is revealed by analysis of kinetic Monte Carlo simulations.Comment: 4 pages, 7 figure

Visual tool for estimating the fractal dimension of images

This work presents a new Visual Basic 6.0 application for estimating the fractal dimension of images, based on an optimized version of the box-counting algorithm. Following the attempt to separate the real information from noise, we considered also the family of all band-pass filters with the same band-width (specified as parameter). The fractal dimension can be thus represented as a function of the pixel color code. The program was used for the study of paintings cracks, as an additional tool which can help the critic to decide if an artistic work is original or not. In its second version, the application was extended for working also with csv files and three-dimensional images.Comment: A new version was accepted to Computer Physics Communications doi:10.1016/j.cpc.2009.12.00

Realization of the mean-field universality class in spin-crossover materials

In spin-crossover materials, the volume of a molecule changes depending on whether it is in the high-spin (HS) or low-spin (LS) state. This change causes distortion of the lattice. Elastic interactions among these distortions play an important role for the cooperative properties of spin-transition phenomena. We find that the critical behavior caused by this elastic interaction belongs to the mean-field universality class, in which the critical exponents for the spontaneous magnetization and the susceptibility are $\beta = 1/2$ and $\gamma = 1$, respectively. Furthermore, the spin-spin correlation function is a constant at long distances, and it does not show an exponential decay in contrast to short-range models. The value of the correlation function at long distances shows different size-dependences: $O(1/N)$, $O(1/\sqrt{N})$, and constant for temperatures above, at, and below the critical temperature, respectively. The model does not exhibit clusters, even near the critical point. We also found that cluster growth is suppressed in the present model and that there is no critical opalescence in the coexistence region. During the relaxation process from a metastable state at the end of a hysteresis loop, nucleation phenomena are not observed, and spatially uniform configurations are maintained during the change of the fraction of HS and LS. These characteristics of the mean-field model are expected to be found not only in spin-crossover materials, but also generally in systems where elastic distortion mediates the interaction among local states.Comment: 13 pages, 16 figure

Effects of Space Charge, Dopants, and Strain Fields on Surfaces and Grain Boundaries in YBCO Compounds

Statistical thermodynamical and kinetically-limited models are applied to study the origin and evolution of space charges and band-bending effects at low angle [001] tilt grain boundaries in YBa$_2$Cu$_3$O$_7$ and the effects of Ca doping upon them. Atomistic simulations, using shell models of interatomic forces, are used to calculate the energetics of various relevant point defects. The intrinsic space charge profiles at ideal surfaces are calculated for two limits of oxygen contents, i.e. YBa$_2$Cu$_3$O$_6$ and YBa$_2$Cu$_3$O$_7$. At one limit, O$_6$, the system is an insulator, while at O$_7$, a metal. This is analogous to the intrinsic and doping cases of semiconductors. The site selections for doping calcium and creating holes are also investigated by calculating the heat of solution. In a continuum treatment, the volume of formation of doping calcium at Y-sites is computed. It is then applied to study the segregation of calcium ions to grain boundaries in the Y-123 compound. The influences of the segregation of calcium ions on space charge profiles are finally studied to provide one guide for understanding the improvement of transport properties by doping calcium at grain boundaries in Y-123 compound.Comment: 13 pages, 5 figure