1,721,069 research outputs found
Studio sperimentale di un aspetto idrodinamico di correnti supercritiche in canali con macroscabrezze (parte 2.)
No full textRegionalisation of rainfall data through the use of cluster and factor analysis techniques
No full textConstructed wetland for the treatment of anaerobic digester effluent: experimental design
No full textConstructed wetlands have been studied by many research groups during over 40 years, but few aspects remain to be better understood as numerous information must be deeper verified. In the last years, aside the related research activity, also the efficiency aspects of this subject is becoming more and more important. For this reasons the authors decided to build inside our academic department courtyard an hybrid constructed wetland system (CW), using the most recent guidelines available at design time (Brix, 2005). The overall aim of this research was to investigate the CW system to the treatment of anaerobic digester outlet, modifying it to produce effluents that conform to Italian regulations for wastewater reuse. The tests also aim to verify the removal efficiency under increasing organic and hydraulic loading rate. The constructed plant consists in two parallel cells of subsurface vertical flow (V-SF), and one of horizontal subsurface flow (H-SF) of 1 m3 each. The constant inflow, needed to feed the H-SSF pool, has been realized by gravity using a modified Mariotte bottle. In the V-SSF the water flow is vertical and intermittent and it is been allowed using electric pumps managed by pre-programmed timers. The system can work with a direct and inverse mode flow, with three different streams, one of 50 l/day (related with the initial physical model), one of 594 l/day (related with the second physical model) and a last one of 200 l/day that seems to be the most efficient
AlgaeNRG: Anaerobic digestion tests using microalgae as substrate
No full textMicroalgae cultivated with low cost techniques could be used as valid feed, or feed integrator, for anaerobic digestion process. In the last few years AD technique proved to be an affordable and sustainable treatment method for several agro-zootechnical types of biomass. It has been studied that a microalgae oil content lower than 40% of w/w, brings to a not economically affordable use of this biomass as biofuel source. A valid alternative is represented by the anaerobic digestion process where, with this kind of substrate, the methane quality inside the biogas could reach very high percentages (65-75%). Using the most promising microalgae strain, obtained from parallel experiments and conducted inside the AlgaeNRG research project, several tests under different feeding conditions were performed. In the experiments a self-made 25 L AD pilot plant created specifically for this kind of tests has been used. With this instrument the biogas and methane yield under batch, fed-batch and continuous regime can be correctly estimated. The tests were conducted starting from the simulation of a real anaerobic reactor working phase. The start-up stage was conducted loading half working volume of digestate and half working volume of microalgae biomass. When acceptable steady state condition was reached inside the reactor (methane quality exceeds 50% of the produced biogas), the second stage of the experience was performed. The biomass initially loaded has been gradually substituted with a new one made only of microalgae. COD behaviour, methane and biogas yields, pH, temperatures (inside the reactor and the gasometer), and pressure (relative and absolute) trends were analysed. Analytic evaluation and possible scale up use will be presente
Valutazione della pericolosità connessa con gli eventi di piena nel bacino del torrente Prebech (Val di Susa)
No full textRainwater harvesting techniques as an adaptation strategy for flood mitigation
Full text linkThe development of adaptation and mitigation strategies to tackle anthropic and climate changes impacts is
becoming a priority in drought-prone areas. This study examines the capabilities of indigenous rainwater
harvesting techniques (RWHT) to be used as a viable solution for flood mitigation. The study analyses the
hydraulic performance of the most used micro-catchment RWHT in sub-Saharan regions, in terms of flow peak
reduction (FPR) and volume reduction (VR) at the field and basin scale. Parametrized hyetographs were built to
replicate the extreme precipitations that strike Sahelian countries during rainy seasons. 2D hydrodynamic
simulations showed that half-moons placed with a staggered configuration (S-HM) have the best performances
in reducing runoff. At the field scale, S-HM showed a remarkable FPR of 77% and a VR of 70% in case of
extreme rainfall. Instead at the basin scale, in which only 5% of the surface was treated, 13% and 8%
respectively for FPR and VR were obtained. In addition, the reduction of the runoff coefficient (Rc) between the
different configuration was analyzed. The study critically evaluates hydraulic performances of the different
techniques and shows how pitting practices cannot guarantee high performance in case of extreme
precipitations. These results will enrich the knowledge of the hydraulic behavior of RWHT; aspect marginally
investigated in the scientific literature. Moreover, this study presents the first scientific application of HEC-RAS
as a rainfall-runoff model. Despite some limitations, this model has the effective feature of using very high-resolution
topography as input for hydraulic simulations. The results presented in this study should encourage
stakeholders to upscale the use of RWHT in order to lessen the flood hazard and land degradation that
oppresses arid and semi-arid areas
Investigation of increasing organic loading rate in the co-digestion of energy crops and cow manure mix
No full textThe increase of organic loading rate from 4.45 to 7.78 g-VS/l-d in a one stage, pilot biogas plant was investigated. The experimental was conducted using a co-digestion of cow manure and crop silage mix. The test was dived in three subsequent phases with different feeding ratios. The benefits of optimizing the proportion of crops and loading rate in co-digestion were shown by the fact that during feeding with 79% VS of crop in the feedstock, up to 109% higher specific methane yield was obtained than during the start up phase. It was also found that further increasing the proportion of crop silage up (to 80%) led to a process breakdown with a decrease of methane proportion down to 48%...... The result of this study show, that most agricultural biogas plant have a great potential for a significant capacity increase and technology improvement
Past and Future Precipitation Trend Analysis for the City of Niamey (Niger): An Overview
Full text linkDespite the interest in detecting the extremes of climate in the West African Sahel, few studies have been specifically conducted on the Republic of Niger. This research focuses on past, present, and future precipitation trends for the city of Niamey through the combined assessment of WMO precipitation indices using RClimDex and the Standardized Precipitation Index. Past daily precipitation data were derived from a 60-year reconstructed meteorological dataset for the Niamey airport station for the period of 1950–2009 and validated through comparison with an observed time series at Niamey airport (1980–2012). Precipitation analysis confirms the literature’s findings, in particular, a decreasing trend in total precipitation over the period of 1950–2009, and a positive trend for data that spans over the period of 1980–2009, suggesting a precipitation recovery after the dry epoch (1968–1985), even if the deficit with the wettest years in the period of 1950–1968 has not been made up. Furthermore, WATCH-Forcing-Data-ERA-Interim projections, elaborated under RCP 4.5 and RCP 8.5 socio-economic conditions, show that precipitation will increase in the future. Therefore, the Nigerien population will benefit from increased rainfall, but will also have to cope with the exacerbation of both flood and drought risks due to a great interannual variability that can positively or negatively influence water availability
Small catchments environmental flows assessment at regional scale: the case study of Piedmont Region (NW Italy)
No full text- …
