Emergence and fate of siloxanes in waste streams: Release mechanisms, partitioning and persistence in three environmental compartments

Siloxanes are widely used in personal care and industrial products due to their low surface tension, thermal stability, antimicrobial and hydrophobic properties, among other characteristics. Volatile methyl siloxanes (VMS) have been detected both in landfill gas and biogas from anaerobic digesters at wastewater treatment plants. As a result, they are released to gas phase during waste decomposition and wastewater treatment. During transformation processes of digester or landfill gas to energy, siloxanes are converted to silicon oxides, leaving abrasive deposits on engine components. These deposits cause increased maintenance costs and in some cases complete engine overhauls become necessary. ^ The objectives of this study were to compare the VMS types and levels present in biogas generated in the anaerobic digesters and landfills and evaluate the energetics of siloxane transformations under anaerobic conditions. Siloxane emissions, resulting from disposal of silicone-based materials, are expected to increase by 29% within the next 10 years. Estimated concentrations and the risk factors of exposure to siloxanes were evaluated based on the initial concentrations, partitioning characteristics and persistence. It was determined that D4 has the highest risk factor associated to bioaccumulation in liquid and solid phase, whereas D5 was highest in gas phase. Additionally, as siloxanes are combusted, the particle size range causes them to be potentially hazardous to human health. When inhaled, they may affix onto the alveoli of the lungs and may lead to development of silicosis. Siloxane-based COD-loading was evaluated and determined to be an insignificant factor concerning COD limits in wastewater. ^ Removal of siloxane compounds is recommended prior to land application of biosolids or combustion of biogas. A comparison of estimated costs was made between maintenance practices for removal of siloxane deposits and installation/operation of fixed-bed carbon absorption systems. In the majority of cases, the installation of fixed-bed adsorption systems would not be a feasible option for the sole purpose of siloxane removal. However they may be utilized to remove additional compounds simultaneously.^

Enea Silvio Piccolomini en España. Con la edición del "Tratado de la miseria de los cortesanos", (Sevilla, Cromberger, 1520)

As it is well known, the Renaissance in Spain cannot be understood without a deep knowledge of the Italian quattrocento: art and thinking have an important debt with a culture that shaped a new society that can be named Modern Era. So, there are many intellectuals that are the main reference to our writers: Leonardo Bruni, Giannozzo Manetti, Bartolomeo Facio, Antonio Beccadelli, Poggio Bracciolini, Francesco Filelfo, Flavio Biondo, Lorenzo Valla, Vespasiano da Bisticci, Pier Candido Decembrio, Guarino da Verona, Pico della Mirandola, Marsilio Ficino, and a big number that includes necessarily the name of Enea Silvio Piccolomini (1405-1464). In effect, the creator that became Pope as Pío II is one outstanding figure of that Humanism that early putted down roots in Spain, a country in construction that produced very important fruits in those years. Under these circumstances, this study has as main objective to analyse the large work of the humanist Pope par excellence, and to establish the relationship between his writings and genres, works and authors in the Iberian peninsula that wrote under his influence. Furthermore, in the following pages can be found a edition of the translation, by Diego López de Cortegana, of one of Picolomini’s works, the Tratado de la miseria de los cortesanos, a work that can be taken as an example of the attention payed to his works by authors like Juan de Lucena, Rodrigo Sánchez de Arévalo, Cristóbal de Castillejo or fray Antonio de Guevara. After a brief introduction that points that the attention to Enea Silvio Piccolomini is not diminishing, that, on the contrary, is clearly alive if we consider modern editions and translations to different languages, I concentrate on the biography of Pío II. With this purpose I take as base the text that this humanist wrote with the aim of building an adequate imago vitae that related the achievements in the religious sphere (with a failed promotion of a last crusade against the Turk) and also his creative labour. I refer to the Commentarii rerum memorabilium quae temporibus suis contingerunt, an extensive autobiography that did not spare the self-praise and conceals some controversial author’s facts, such as the “reconciling” thesis that undermined the Popes authority and power. In addition, in that chapter can be found a study of the writing process of the titles that includes Piccolomini’s bibliography, since we can think that the author’s commentary is extremely relevant to inform about the moment of writing and its purpose...

Design of maintenance structures for rural electrification with solar home systems. The case of the Moroccan program.

n decentralised rural electrification through solar home systems, private companies and promoting institutions are faced with the problem of deploying maintenance structures to operate and guarantee the service of the solar systems for long periods (ten years or more). The problems linked to decentralisation, such as the dispersion of dwellings, difficult access and maintenance needs, makes it an arduous task. This paper proposes an innovative design tool created ad hoc for photovoltaic rural electrification based on a real photovoltaic rural electrification program in Morocco as a special case study. The tool is developed from a mathematical model comprising a set of decision variables (location, transport, etc.) that must meet certain constraints and whose optimisation criterion is the minimum cost of the operation and maintenance activity assuming an established quality of service. The main output of the model is the overall cost of the maintenance structure. The best location for the local maintenance headquarters and warehouses in a given region is established, as are the number of maintenance technicians and vehicles required.