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Arrays of chemical sensors, generally used in electronic noses (e.noses), yield a unique pattern for a given mixture of odours. In recent years, there has been an increasing interest in applications of e.noses for the characterization and monitoring of environmental odours. While they have been around over the last three decades, little effort has been devoted to the development of the measurement chamber. Within it, all sensors are placed in contact of the flux of air to characterize in terms of odours. A measurement chamber must ensure standardized conditions in term of temperature, humidity and contact time of inflow air with the sensor surfaces. Aim of this work is to numerically analyse the fluid dynamic performance of measurement chambers with different geometry in order to improve sensor response signals in terms of stability, reproducibility and response time. The Fluid dynamic study was carried out by a Computational Fluid Dynamic (CFD) commercial software. Results show an objective methodological approach that can be used to design measurement chamber for electronic noses.

Both a numerical and an analytical models were developed to simulate temperature profiles in continuous laminar pipe flow during microwave heating. Fully developed velocity and thermally developing conditions were assumed. The numerical solution was obtained by first solving Maxwell equations and then by coupling them with the energy balance for the flowing fluid. On the other hand, the same problem was solved analytically under the simplifying assumption foreseeing uniform heat generation inside the pipe. With the aim of reducing computational efforts, numerical and analytical results were compared in order to investigate conditions for which the two models allowed to recover the same temperature patterns. Thus, it has been shown that suitable conditions can be found for which the simplified analytical model can lead to an easy way to predict the heat transfer through the pipe.

Offensive odours from industrial and sanitary environmental engineering plants can cause problems, such as sleep disorders, migraine and loss of appetite, also considering that they address the quality of life. Odour emission characterization is currently discussed in international literature as to determine its most feasible implementation. A method for continuous odour monitoring is based on the use of electronic noses. Electronic nose is an instrument which comprises an array of electronic chemical sensors with partial specificity and an appropriate pattern recognition system, capable of recognizing simple or complex odours. Aim of this work is to numerically analyze the performance of a sensor chamber in order to improve sensor response signals in terms of stability, reproducibility and response time. Comparative results are based on the location of four different diffusers. The numerical analysis was performed by a computational fluid dynamic (CFD) software in order to guarantee that all sensors are exposed to the same chemical sample under the same experimental conditions for the same time, reducing the presence of stagnant or recirculating regions.

Health problems and respiratory diseases are associated with poor indoor air ventilation. We investigated the air quality inside a classroom-laboratory where no ventilation is provided. The case of study, consisting of an internal enclosure, is located at the Escuela Técnica Superior de Edificación (ETSEM) of Madrid (Spain). The high height favours air stratification which is analysed in terms of temperature and CO 2 spatial distribution. Temperature, air humidity, atmospheric pressure and CO 2 concentration measurements were taken in time at three different height locations. A CFD numerical model was established to analyse air quality. Flow circulation is derived by solving full 3D Navier - Stokes governing equations, coupled with the thermal problem. The diffusion problem of the CO 2 produced by the inner occupants is then derived from the kinematics solution. Three scenarios were taken into account: occupants seated (1), standing (2), half seated, half standing (3). Results clearly show the air stratification as a result of density gradient, which is in turn determined by temperature difference between the occupants and the surrounding air. Temperature prediction maximum relative error is contained to 3.5 %. As expected, CO 2 concentration increases over time, reaching maximum values depending on the configuration considered and height location., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

With the arrival of the SARS-CoV-2 coronavirus, the scientific academia, as well as policymakers, are striving to conceive solutions as an attempt to contain the spreading of contagion. Among the adopted measures, severe lockdown restrictions were issued to avoid the diffusion of the virus in an uncontrolled way through public spaces. It can be deduced from recent literature that the primary route of transmission is via aerosols, produced mainly in poorly ventilated interior areas where infected people spend a lot of time with other people. Concerning contagion rates, accumulated incidence or number of hospitalizations due to COVID-19, Spain, and Italy have reached very high levels. In this framework, a regression analysis to assess the feasibility of the indoor ventilation measures established in Spain and Italy, with respect to the European framework, is here presented. To this aim, ten cases of housing typology were and analyzed. The results show that the measures established in the applicable regulations to prevent and control the risk of contagion by aerosols are not adequate to guarantee a healthy environment indoors. The current Italian guidelines are more restrictive than in Spain, yet the ventilation levels are still insufficient in times of pandemic., Competing Interests: None, (© 2021 Elsevier Ltd. All rights reserved.)

The present work is aimed at analyzing the performance of the commercial filters used for the mechanical filtration of suspended solid particles. In particular, it is intended to evaluate the head losses due to the presence of the filter in the plant and how these losses vary depending on the circulating flow rate, the nominal porosity of the filter, and its clogging degree. Filters with interstices of different sizes, from 1 to 50 μm, were compared for the performance analysis. The polypropylene wire, in facts, wrapped around a windowed cylinder of the same material, allows the creation of meshes with the desired degree of compactness. The experiments were carried out at the Laboratory of Environmental and Maritime Hydraulics (LIDAM) in a hydraulic circuit reproducing a domestic piping system, where different water demand scenarios were analyzed. The clogging of the cartridge was made with the aid of sand particles, attached, with the help of a natural glue, to the external surface of the filter. More than 200 measurements were carried out, which showed a clear increasing trend of the head losses at the filter as the clogging degree and the circulating flow rate increase. In all cases, the trend of the pressure drop at the filter has a more than linear trend. Also, it was observed that head losses did not exhibit a marked dependence on the nominal porosity. Best performances in terms of minor head losses were obtained by the 50-μm filter.

The anaerobic digestion (AD) process is influenced by a variety of operation parameters, such as sludge rheology, mixing, temperature, solid retention time (SRT), hydraulic retention time (HRT) and solids concentration. The optimum in the mixing lies somewhere between no-mixing and continuous mixing, as the lack or excessive mixing can lead to poor AD performance instead. A three-dimensional computational fluid dynamics steady/unsteady model, incorporating the rheological properties of the sludge, was developed and applied to quantify mixing in a full-scale anaerobic digester. Mechanical and gas mixing solutions were taken into account, keeping constant the daily energy consumption. Results, consisting of velocity magnitude and patterns, dead zone formation and turbulence levels were discussed. Compared to the mechanical mixing, gas mixing had lower percentage of dead zones (about 5% against 50%), larger maximum velocity (about 3 m/s against 1 m/s) as well as larger turbulent kinetic energy levels (0.24 m 2 /s 2 against 0.001 m 2 /s 2 ).

The data provided here refers to the experimental laboratory investigation conducted in the Laboratory of Environmental and Maritime Hydraulics (LIDAM) of University of Salerno, Italy, with the aim of developing a new filtering cartridge for water treatment capable of overcoming the main inconveniences shown by usual commercial cartridges. Specifically, the proposed filtering cartridge is an economic, non-toxic, low-resistance and long-life cartridge, currently under a patent pending status, whose main advantage is to permit to significantly reduce, compared with the commercial cartridges, average head losses induced by the cartridge even for high clogging degrees, and to increase, as a consequence, the life cycle of the cartridges. In this article a collection of pictures is provided, showing the different filters progressively tested in the laboratory, also in sand clogging conditions, until finding the optimal solution. Pictures of the laboratory equipment, with adopted materials and instrumentation, are also given. Finally, tables with the values of the local pressure drops at the cartridge in the different test conditions are provided. The data is related to "A new cost effective, long life and low resistance filter cartridge for water treatment" [1].

The fate of indigenous surface-water and wastewater antibiotic resistant bacteria in a mild slope stream simulated through a hydraulic channel was investigated in outdoor experiments. The effect of (i) natural (dark) decay, (ii) sunlight, (iii) cloudy cover, (iv) adsorption to the sediment, (v) hydraulic conditions, (vi) discharge of urban wastewater treatment plant (UWTP) effluent and (vii) bacterial species (presumptive Escherichia coli and enterococci) was evaluated. Half-life time (T 1/2 ) of E. coli under sunlight was in the range 6.48-27.7min (initial bacterial concentration of 10 5 CFU/mL) depending on hydraulic and sunlight conditions. E. coli inactivation was quite similar in sunny and cloudy day experiments in the early 2hr, despite of the light intensity gradient was in the range of 15-59W/m 2 ; but subsequently the inactivation rate decreased in the cloudy day experiment (T 1/2 =23.0min) compared to sunny day (T 1/2 =17.4min). The adsorption of bacterial cells to the sediment (biofilm) increased in the first hour and then was quite stable for the remaining experimental time. Finally, when the discharge of an UWTP effluent in the stream was simulated, the proportion of indigenous antibiotic resistant E. coli and enterococci was found to increase as the exposure time increased, thus showing a higher resistance to solar inactivation compared to the respective total populations., (Copyright © 2017. Published by Elsevier B.V.)