El comportamiento geomecánico deformacional de los residuos urbanos : aplicación a un caso real

Las características de heterogeneidad de los residuos sólidos urbanos así como la degradación biológica de sus componentes orgánicos influyen en los aspectos geotécnicos de los vertederos. La magnitud y duración de los asientos son factores muy importantes en el estudio del comportamiento de vertederos. La velocidad de asiento disminuye con el tiempo pero se mantiene durante muchos años después de su clausura. Para reducir los asientos del relleno, uno de los métodos de tratamiento que se utiliza es la compactación dinámica de los residuos sólidos. En este trabajo se estudia la mejora, a través de la compactación dinámica por impacto tipo “Menard”, de un vertedero de residuos sólidos en Madrid y los asientos provocados por la aplicación de una sobrecarga. Se analiza el comportamiento de los residuos sólidos con tratamiento de mejora, así como la predicción de asientos a 10 años aplicando los modelos Sowers (1973), Yen & Scanlon (1975), Gandola et al. (1992) y Meruelo (1994). Heterogonous characteristics of solid urban residues as well as biological decomposition of its organic components affect the geotechnical aspects of the landfills. The magnitude and the duration of the landfill settlement are one of the significant factors in studying the behavior of landfills. Although the rate of the settlement decreases as the time passes, however it is still maintained during many years after its closure. One of the methods used to reduce the settlement waste is through the dynamic consolidation methods of the solid residues. In this work, by applying the “Menard” dynamic consolidation method, we are studying the improvement of solid residue landfill in Madrid and the settlements provoked by overloading. The behavior of the solid residues through the improvement treatments as well as 10 years ahead prediction are analyzed by applying the models by Sowers (1973), Yen & Scanlon (1975), Gandola et al. (1992) and Meruelo (1994).

Yield, nutrient utilization and soil properties in a melon crop amended with wine-distillery waste

In Spain, large quantities of wine are produced every year (3,339,700 tonnes in 2011) (FAO, 2011) with the consequent waste generation. During the winemaking process, solid residues like grape stalks are generated, as well as grape marc and wine lees as by-products. According to the Council Regulation (EC) 1493/1999 on the common organization of the wine market, by-products coming from the winery industry must be sent to alcohol-distilleries to generate exhausted grape marc and vinasses. With an adequate composting treatment, these wastes can be applied to soils as a source of nutrients and organic matter. A three-year field experiment (2011, 2012 and 2013) was carried out in Ciudad Real (central Spain) to study the effects of wine-distillery waste compost application in a melon crop (Cucumis melo L.). Melon crop has been traditionally cultivated in this area with high inputs of water and fertilizers, but no antecedents of application of winery wastes are known. In a randomized complete block design, four treatments were compared: three compost doses consisted of 6.7 (D1), 13.3 (D2) and 20 t compost ha-1 (D3), and a control treatment without compost addition (D0). The soil was a shallow sandy-loam (Petrocalcic Palexeralfs) with a depth of 0.60 m and a discontinuous petrocalcic horizon between 0.60 and 0.70 m, slightly basic (pH 8.4), poor in organic matter (0.24%), rich in potassium (410 ppm) and with a medium level of phosphorus (22.1 ppm). During each growing period four harvests were carried out and total and marketable yield (fruits weighting <1 kg or visually rotten were not considered), fruit average weight and fruit number per plant were determined. At the end of the crop cycle, four plants per treatment were sampled and the nutrient content (N, P and K) was determined. Soil samplings (0-30 cm depth) were carried before the application of compost and at the end of each growing season and available N and P, as well as exchangeable K content were analyzed. With this information, an integrated analysis was carried out with the aim to evaluate the suitability of this compost as organic amendment.

Desarrollo de conglomerados con la incorporación de cenizas volantes procedentes de la incineración de residuos sólidos urbanos

Esta tesis presenta los resultados de la investigación realizada sobre la inertización de cenizas volantes procedentes de residuos sólidos urbanos y su posterior encapsulación en distintas matrices de mortero. Durante el proceso de inertización, se ha logrado la inertización de éste residuo tóxico y peligroso (RTP) y también su valorización como subproducto. De esta forma se dispone de nueva “materia prima” a bajo coste y la eliminación de un residuo tóxico y peligroso con la consiguiente conservación de recursos naturales alternativos. La caracterización química de las cenizas analizadas refleja que éstas presentan altas concentraciones de cloruros, Zn y Pb. Durante la investigación se ha desarrollado un proceso de inertización de las cenizas volantes con bicarbonato sódico (NaHCO3) que reduce en un 99% el contenido en cloruros y mantiene el pH en valores óptimos para que la concentración de los metales pesados en el lixiviado sea mínima debido a su estabilización en forma de carbonatos insolubles. Se han elaborado morteros con cuatro tipos distintos de cementos (CEM-I, CEM-II, CAC y CSA) incorporando cenizas volantes inertizadas en una proporción igual a un 10% en peso del árido utilizado. Los morteros ensayados abarcan distintas dosificaciones tanto en la utilización de áridos con distintos diámetros (0/2 y 0/4), como en la relación cemento/árido (1/1 y 1/3). Se han obtenido las propiedades físicas y mecánicas de estos morteros mediante ensayos de Trabajabilidad, Estabilidad Dimensional, Carbonatación, Porosidad y Resistencias Mecánicas. De igual forma, se presentan resultados de ensayos de lixiviación de Zn, Pb, Cu y Cd, sobre probetas monolíticas de los morteros con los mejores comportamientos físico/mecánicos, donde se ha analizado el contenido en iones de dichos metales pesados lixiviados mediante determinación voltamperométrica de redisolución anódica Se concluye que todos los morteros ensayados son técnicamente aceptables, siendo los más favorables los elaborados con Cemento de Sulfoaluminato de Calcio (CSA) y con Cemento de Aluminato de Calcio (CAC). En este último caso, se mejoran las resistencias a compresión de los morteros de referencia en más de un 48%, y las resistencias a flexión en más de un 67%. De igual forma, los ensayos de lixiviado revelan la completa encapsulación de los iones de Zn y la mitigación en el lixiviado de los iones de Pb. Ambos morteros podrían ser perfectamente validos en actuaciones en las que se necesitase un producto de fraguado rápido, altas resistencias iniciales y compensación de las retracciones con una elevada estabilidad dimensional. En base a esto, el material podría ser utilizado como mortero de reparación en viales y pavimentos que requiriesen altas prestaciones, tales como: soleras industriales, pistas de aterrizaje, aparcamientos, etc. O bien, para la confección de elementos prefabricados sin armaduras estructurales, dada su elevada resistencia a flexión. ABSTRACT This dissertation presents the results of a research on inerting fly ash from urban solid waste and its subsequent encapsulation in mortar matrixes. The inerting of this hazardous toxic waste, as well as its valorization as a by-product has been achieved. In this way, a new "raw material" is available through a simple process and the toxic and hazardous waste is eliminated, and consequently, conservation of alternative natural resources is strengthened. Chemical analysis of the ashes analyzed shows high concentrations of soluble chlorides, Zn and Pb. An inerting process of fly ash with sodium bicarbonate (NaHCO3) has been developed which reduces 99% the content of chlorides and maintains pH at optimal values, so that the concentration of heavy metals in the leachate is minimum, due to its stabilization in the form of insoluble carbonates. Mortars with four different types of cements (CEM-I, CEM-II, CAC and CSA) have been developed by the addition of inertized fly ash in the form of carbonates, in the proportion of 10% in weight of the aggregates used. The samples tested include different proportions in the use of aggregates with different sizes (0/2 and 0/4), and in the cement/aggregate ratio (1/1 and 1/3). Physical/mechanical properties of these mortars have been studied through workability, dimensional stability, carbonation, porosity and mechanic strength tests. Leaching tests of Zn, Pb, Cu and Cd ions are also being performed on monolithic samples of the best behavioral mortars. The content in leachated heavy metal ions is being analyzed through stripping voltammetry determination. Conclusions drawn are that the tested CAC and CSA cement mortars present much better behavior than those of CEM-I and CEM-II cement. The results are especially remarkable for the CAC cement mortars, improving reference mortars compression strengths in more than 48%, and also bending strengths in more than 67%. Leaching tests confirm that the encapsulation of Zn and Pb is achieved and leachate of both ions is mitigated within the mortar matrixes. For the above stated reasons, it might be concluded that mortars made with calcium aluminate cements or calcium sulfoaluminate with the incorporation of treated fly ash, may be perfectly valid for uses in which a fast-curing product, with high initial strength and drying shrinkage compensation with a high dimensional stability is required. Based on this, the material could be used as repair mortar for structures, roads and industrial pavements requiring high performance, such as: industrial floorings, landing tracks, parking lots, etc. Alternatively, it could also be used in the manufacture of prefabricated elements without structural reinforcement, given its high bending strength.

Comparison of vibration and rolling noise emission of resilient and solid monobloc railway wheels in underground lines

Flat or worn wheels rolling on rough or corrugated tracks can provoke airborne noise and ground-borne vibration, which can be a serious concern for nearby neighbours of urban rail transit lines. Among the various treatments used to reduce vibration and noise, resilient wheels play an important role. In conventional resilient wheels, a slightly prestressed V­shaped rubber ring is mounted between the steel wheel centre and tyre. The elastic layer enhances rolling noise and vibration suppression, as well as impact reduction on the track. In this paper the effectiveness of resilient wheels in underground lines, in comparison to monobloc ones, is assessed. The analysed resilient wheel is able to carry greater loads than standard resilient wheels used for light vehicles. It also presents a greater radial resiliency and a higher axial stiffness than conventional V­wheels. The finite element method was used in this study. A quarter car model was defined, in which the wheelset was modelled as an elastic body. Several simulations were performed in order to assess the vibrational behaviour of elastic wheels, including modal, harmonic and random vibration analysis, the latter allowing the introduction of realistic vertical track irregularities, as well as the influence of the running speed. Due to numerical problems some simplifications were needed. Parametric variations were also performed, in which the sensitivity of the whole system to variations of rubber prestress and Poisson’s ratio of the elastic material was assessed.Results are presented in the frequency domain, showing a better performance of the resilient wheels for frequencies over 200 Hz. This result reveals the ability of the analyzed design to mitigate rolling noise, but not structural vibrations, which are primarily found in the lower frequency range.

Geochemistry and risk assessment of street dust in Luanda, Angola, a tropical urban environment

A total of 92 samples of street dust were collected in Luanda, Angola, were sieved below 100 μm, and analysed by ICP-MS for 35 elements after an aqua-regia digestion. The concentration and spatial heterogeneity of trace elements in the street dust of Luanda are generally lower than in most industrialized cities in the Northern hemisphere. These observations reveal a predominantly “natural” origin for the street dust in Luanda, which is also manifested in that some geochemical processes that occur in natural soils are preserved in street dust: the separation of uranium from thorium, and the retention of the former by carbonate materials, or the high correlation between arsenic and vanadium due to their common mode of adsorption on solid particles in the form of oxyanions. The only distinct anthropogenic fingerprint in the composition of Luanda's street dust is the association Pb–Cd–Sb–Cu (and to a lesser extent, Ba–Cr–Zn). The use of risk assessment strategies has proved helpful in identifying the routes of exposure to street dust and the trace elements therein of most concern in terms of potential adverse health effects. In Luanda the highest levels of risk seem to be associated (a) with the presence of As and Pb in the street dust and (b) with the route of ingestion of dust particles, for all the elements included in the study except Hg, for which inhalation of vapours presents a slightly higher risk than ingestion. However, given the large uncertainties associated with the estimates of toxicity values and exposure factors, and the absence of site-specific biometric factors, these results should be regarded as preliminary and further research should be undertaken before any definite conclusions regarding potential health effects are drawn.

Air Mines. Urban Space Station

Air Mines The sky over the city's port was the color of a faulty screen, only partly lit up. As the silhouette of nearby buildings became darker, but more clearly visible against the fading blur-filter of a background, the realization came about how persistent a change had been taking place. Slowly, old wooden water reservoirs and rattling HVAC systems stopped being the only inhabitants of roofs. Slightly trembling, milkish jellyfish-translucent air volumes had joined the show in multiples. A few years ago artists and architects seized upon the death of buildings as their life-saving media. Equipped with constructive atlases and instruments they started disemboweling their subjects, poking about their systems, dumping out on the street the battered ugliness of their embarrassing bits and pieces, so rightly hidden by facades and height from everyday view. But, would you believe it? Even ?old ladies?, investment bankers or small children failed to get upset. Of course, old ladies are not what they used to be. It was old ladies themselves that made it happen after years of fights with the town hall, imaginative proposals and factual arguments. An industry with little financial gains but lots of welcome externalities was not, in fact, the ground for investment bankers. But they too had to admit that having otherwise stately buildings make fine particulate pencils with their facades was not the worse that could happen. Yes, making soot pencils had been found an interesting and visible end product of the endeavor, a sort of mining the air for vintage writing tools one can actually touch. The new view from the street did not seem as solid or dignified as that of old, and they hated that the market for Fine Particulates Extraction (FPE, read efpee) had to be applied on a matrix of blocks and streets that prevented undue concentration of the best or worse solutions. It had to be an evenly distributed city policy in order for the city to apply for cleaning casino money. Once the first prototypes had been deployed in buildings siding Garden Avenue or Bulwark Street even fast movers appreciated the sidekick of flower and plant smell dripping down the Urban Space Stations (USS, read use; USSs, read uses) as air and walls cooled off for a few hours after sunset. Enough. It was all nice to remember, but it was now time to go up and start the lightweight afternoon maintenance of their USS. Coop discussions had taken place all through the planning and continued through the construction phase as to how maintenance was going to be organized. Fasters had voted for a pro, pay a small amount and let them use it for rent and produce. In the end some neighbors decided they were slow enough to take care and it was now the turn. Regret came periodically, sometimes a week before, and lasted until work actually started. But lately it had been replaced by anxiety when it needed to be passed over to the next caretaker. It did not look their shift was good enough and couldn?t wait to fix it. Today small preparations needed to be made for a class visit next day from a nearby cook school. They were frequenters. It had not been easy, but it shouldn?t have been that hard. In the end, even the easiest things are hard if they involve a city, buildings and neighbors. On the face of the data, the technicalities and the way final designs had been worked out for adaptation to the different settings, the decision of where to go was self evident, but organization issues and the ever-growing politics of taste in a city of already-gentrified-rodents almost put the project in the frozen orbit of timeless beautiful future possibilities. This is how it was. A series of designs by XClinic and OSS had made it possible to adapt to different building structures, leave in most cases the roof untouched and adapted a new technology of flexing fiberglass tubes that dissipated wind pressure in smooth bending.......

Risk of Leaching in Soils Amended by Compost and digestate from Municipal Solid Waste

New European directives have proposed the direct application of compost and digestate produced from municipal solid wastes as organic matter sources in agricultural soils. Therefore information about phosphorus leaching from these residues when they are applied to the soil is increasingly mportant. Leaching experiments were conducted to determine the P mobility in compost and digestate mixtures, supplying equivalent amounts to 100 kg P ha?1 to three different types of soils. The tests were performed in accordance with CEN/TS 14405:2004 analyzing the maximum dissolved reactive P and the kinetic rate in the leachate. P biowaste fractionation indicated that digestate has a higher level of available P than compost has. In contrast, P losses in leaching experiments with soil-compost mixtureswere higher than in soil-digestate mixtures. For bothwastes, therewas no correlation between disolved reactive P lost and the water soluble P.The interaction between soil and waste, the long experimentation time, and the volume of leachate obtained caused the waste?s wettability to become an influential parameter in P leaching behavior. The overall conclusion is that kinetic data analysis provides valuable information concerning the sorption mechanism that can be used for predicting the large-scale behavior of soil systems.