Municipal wastewater treatment by biofiltration: comparisons of various treatment layouts. Part 1: assessment of carbon and nitrogen removal

One of the largest wastewater treatment plants in the Paris conurbation (240,000 m(3)/d) has been studied over several years in order to provide technical and economical information about biological treatment by biofiltration. Biofiltration systems are processes in which carbon and nitrogen pollution of wastewater are treated by ascendant flow through immersed fixed cultures. This paper, focused on technical information, aims: (1) to compare performances of the three biological treatment layouts currently used in biofiltration systems: upstream denitrification (UD), downstream denitrification (DD) and combined upstream-downstream denitrification (U-DD) layouts; and (2) to describe in detail each treatment step. Our study has shown that more than 90% of the carbon and ammoniacal pollution is removed during biological treatment, whatever the layout used. Nitrate, produced during nitrification, is then reduced to atmospheric nitrogen. This reduction is more extensive when the denitrification stage occurs downstream from the treatment (DD layout with methanol addition), whereas it is only partial when it is inserted upstream from the treatment (UD layout - use of endogenous carbonaceous substrate). So, the UD layout leads to a nitrate concentration that exceeds the regulatory threshold in the effluent, and the treatment must be supplemented with a post-denitrification step (U-DD layout). Our work has also shown that the optimal ammonium-loading rate is about 1.1-1.2 kg N-NH(4)(+) per m(3) media (polystyrene) and day. For denitrification, the optimal nitrate-loading rate is about 2.5 kg N per m(3) media (expanded clay) and day in the case of DD with methanol, and is about 0.25 kg N-NO(3)(-) per m(3) media and day in the case of UD with exogenous carbonaceous substrate.     

Simplified Equation for Evaluating the Influence of Surface Residual Stresses on the Toughness of Zirconia Ceramics

A simplified theoretical equation was developed to estimate the influence of a thin surface layer with a nonuniform profile of residual compressive stress on indentation cracking. The model was used to evaluate the toughness of tetragonal zirconia polycrystals that had been doped with 3 mol% yttria (3Y-TZP), which contained surface residual stresses due to phase transformation.     

A security-and quality-aware system architecture for Internet of Things

Internet of Things (IoT) is characterized, at the system level, by high diversity with respect to enabling technologies and supported services. IoT also assumes to deal with a huge amount of heterogeneous data generated by devices, transmitted by the underpinning infrastructure and processed to support value-added services. In order to provide users with valuable output, the IoT architecture should guarantee the suitability and trustworthiness of the processed data. This is a major requirement of such systems in order to guarantee robustness and reliability at the service level. In this paper, we introduce a novel IoT architecture able to support security, privacy and data quality guarantees, thereby effectively boosting the diffusion of IoT services.     

DARE: evaluating Data Accuracy using node REputation

Typical wireless sensor networks (WSNs) applications are characterized by a certain number of different requirements such as: data accuracy, localization, reputation, security, and confidentiality. Moreover, being often battery powered, WSNs face the challenge of ensuring privacy and security despite power consumption limitations. When the application scenario allows their use, data aggregation techniques can significantly reduce the amount of data exchanged over the wireless link at the price of an increased computational complexity and the potential exposition to data integrity risks in the presence of malicious nodes. In this paper, we propose DARE, an hybrid architecture combining WSNs with the wireless mesh networking paradigm in order to provide secure data aggregation and node reputation in WSNs. Finally, the use of a secure verifiable multilateration technique allows the network to retain the trustworthiness of aggregated data even in the presence of malicious node. Extensive performance evaluations carried out using simulations as well as a real-world prototype implementation, show that DARE can effectively reduce the amount of data exchanged over the wireless medium delivering up to 50% battery lifetime improvement to the wireless sensors.     

Virtual worlds in competitive contexts: Analyzing eSports consumer needs

More recently, 3D graphical environments on the Internet, that is virtual worlds, have moved to the center of scientific interest. Since virtual worlds are suggested to mold social computing, research has predominately focused on collaborative virtual worlds. Yet, virtual worlds increasingly move to competitive environments leaving operating businesses with the question as to what to offer in order to fulfill customers’ needs. To close this knowledge gap, we examine competitive virtual worlds in terms of eSports services intrinsically tying cooperation and competition; we illuminate competitive and hedonic need gratifications of continuous eSports use. We apply Uses and Gratifications theory reporting on ten in-depth expert interviews as well as survey data collected from 360 eSports players. We reveal that both competitive (competition and challenge) and hedonic need gratifications (escapism) drive continuous eSports use.     

Developing and sustaining new regional industrial paths: investigating the role of ‘outsiders’ and factors shaping long-term trajectories

This article casts light on the development of new regional industrial paths. We explore factors explaining why regional industries with similar early path development trajectories may exhibit diverging outcomes in the longer run and pay particular attention to the role of ‘outsiders’ in the initiation and further development of regional industrial paths. Drawing on a comparative case study of IT industries in Linköping and Karlskrona, two medium-sized Swedish city regions, we find that the inflow of outsiders was an important driver of early path development processes. However, we find that the interplay between regional preconditions and arriving outsiders, and between outsiders and existing actors, substantially shaped the long-term sustainability of the industrial paths in our study. In particular, the role of agency in fostering positive self-reinforcing mechanisms and structure–agency dynamics are highlighted as key factors for understanding how new industrial development paths are unfolding in the longer term.     

Performance of different immobilized‐cell systems to efficiently produce ethanol from whey: fluidized batch,packed‐bed and fluidized continuous bioreactors

BACKGROUND: The bioconversion of whey into ethanol by immobilized Kluyveromyces marxianus in packed‐bed and fluidized bioreactors is described. Both batch and continuous cultures were analyzed using three different strains of K. marxianus and the effect of the operating mode, temperature, and dilution rates (D) were investigated. RESULTS: All immobilized strains of K. marxianus (CBS 6556, CCT 4086, and CCT 2653) produced similar high yields of ethanol (0.44 ± 0.01 g EtOH g^?1 sugar). Significant variations of conversion efficiencies (66.1 to 83.3%) and ethanol productivities (0.78 to 0.96 g L^?1 h^?1) were observed in the experiments with strain K. marxianus CBS 6556 at different temperatures. High yields of ethanol were obtained in fluidized and packed‐bed bioreactors continuous cultures at different D (0.1 to 0.3 h^?1), with the highest productivity (3.5 g L^?1 h^?1) observed for D = 0.3 h^?1 in the fluidized bioreactor (87% of the maximal theoretical conversion), whereas the highest ethanol concentration in the streaming effluent (28 g L^?1) was obtained for D = 0.1 h^?1. Electronic micrographs of the gel beads showed efficient cell immobilization. CONCLUSION: Batch and continuous cultivations of immobilized K. marxianus in fluidized and packed‐bed bioreactors enable high yields and productivities of ethanol from whey. Copyright © 2012 Society of Chemical Industry     

Hypersound Damping in Vitreous Silica Measured by Ultrafast Acoustics

Recently, an alternative way of measuring hypersound attenuation in silica thin films using ultrafast acoustics was proposed. The attenuation of longitudinal acoustic phonons around 250 GHz has been measured in vitreous silica deposited on a silicon substrate. This method is based on the emission of a short-acoustic pulse from a thin-metallic layer on top of the sample. The high frequency content of the pulse is optically detected in the silicon substrate after propagation in silica. By comparing the signal obtained for various film thicknesses, we can precisely extract sound attenuation in silica in the sub-terahertz range. In order to reach higher and higher frequencies, it is needed to improve both acoustic emission and detection. Concerning emission, it is governed by the thin metallic layer deposited on top which converts the ultrashort optical pulse in an acoustic pulse. Usually, Al is preferred due to its efficiency in light-sound conversion. In this work, the high frequency content of the acoustic emission was improved by studying the influence of the chemical nature, the thickness, and the deposition parameters of the transducer on the detection of ultra-high frequencies in the substrate. As a result of this optimization, it is expected that the hypersound attenuation can be measured in silica up to 350 GHz. A second conclusion of this work is an alternative way of emitting the acoustic pulse based on a resonance effect.