CFD Study on the Ventilation Effectiveness in a Public Toilet under Three Ventilation Methods

The indoor air quality (IAQ) of severely polluted toilets is associated with the transmission of diseases. Computational fluid dynamics (CFD) methods and experimental measurements were used to analyze the diffusion characteristics of pollutants. This study investigated the diffusion characteristics and normalized concentration of ammonia and hydrogen sulfide pollutants under three ventilation systems—mixing ventilation (MV), personalized ventilation (PV), and impinging jet ventilation (IJV)—in a public toilet. The mean age of air (MAA) and air exchange efficiency (AEE) were also analyzed in our study. The results show that the MV scheme has a poor removal effect on pollutants compared with PV and IJV. IJV has advantages in reducing the normalized concentration of pollutants and improving the IAQ. Increasing the number of air changes per hour (ACH) may lead to a longer MAA and reduced air exchange efficiency. Choosing an appropriate number of air changes is very important to improve the IAQ in the toilet.

Effects of Silicic Acid on Leaching Behavior of Arsenic from Spent Calcium-Based Adsorbents with Arsenite

The spent adsorbents that remain after being used to purify As-contaminated water constitute waste containing a large amount of As. These spent adsorbents, after being disposed, are likely to come into contact with silicic acid leached from the soil or cementitious solidification materials. Thus, it is crucial the evaluate the effects of silicic acid on spent adsorbents. In this study, the effects of silicic acid on spent Ca-based (CaO and Ca(OH)2) adsorbents with arsenite were investigated. The As leaching ratio for the spent adsorbents decreased with an increase in the initial concentration of silicic acid in the liquid. Under the tested conditions, the As leaching ratio decreased from 8–9% to less than 0.7% in the presence of silicic acid at an initial Si-normalized concentration of 100 mg/L. The primary mechanism behind the inhibition of As leaching by silicic acid was determined to be re-immobilization via the incorporation of arsenite during the formation of calcium silicates. In the presence of silicic acid, spent Ca-based adsorbents with arsenite had a lower As leaching ratio than those with arsenate. Therefore, spent Ca-based adsorbents with arsenite were found to have a higher environmental stability than those with arsenate.

Revisiting adiabatic fraction estimations in cumulus clouds: high-resolution simulations with a passive tracer

The process of mixing in warm convective clouds and its effects on microphysics are crucial for an accurate description of cloud fields, weather, and climate. Still, they remain open questions in the field of cloud physics. Adiabatic regions in the cloud could be considered non-mixed areas and therefore serve as an important reference to mixing. For this reason, the adiabatic fraction (AF) is an important parameter that estimates the mixing level in the cloud in a simple way. Here, we test different methods of AF calculations using high-resolution (10 m) simulations of isolated warm cumulus clouds. The calculated AFs are compared with a normalized concentration of a passive tracer, which is a measure of dilution by mixing. This comparison enables the examination of how well the AF parameter can determine mixing effects and the estimation of the accuracy of different approaches used to calculate it. Comparison of three different methods to derive AF, with the passive tracer, shows that one method is much more robust than the others. Moreover, this method's equation structure also allows for the isolation of different assumptions that are often practiced when calculating AF such as vertical profiles, cloud-base height, and the linearity of AF with height. The use of a detailed spectral bin microphysics scheme allows an accurate description of the supersaturation field and demonstrates that the accuracy of the saturation adjustment assumption depends on aerosol concentration, leading to an underestimation of AF in pristine environments.

What is Adiabatic Fraction in Cumulus Clouds: High-Resolution Simulations with Passive Tracer

The process of mixing in warm convective clouds and its effects on microphysics, is crucial for an accurate description of cloud fields, weather, and climate. Still, it remains an open question in the field of cloud physics. Adiabatic regions in the cloud could be considered as non-mixed areas and therefore serve as an important reference to mixing. Therefore, the adiabatic fraction (AF) is an important parameter that estimates the mixing level in the cloud in a simple way. Here, we test different methods of AF calculations using high-resolution (10 m) simulations of isolated warm Cumulus clouds. The calculated AFs are compared with a normalized concentration of a passive tracer, which is a measure of dilution by mixing. This comparison enables us to examine how well the AF parameter can determine mixing effects, and to estimate the accuracy of different approaches used to calculate it. The sensitivity of the calculated AF to the choice of different equations, vertical profiles, cloud base height, and its linearity with height are all tested. Moreover, the use of a detailed spectral bin microphysics scheme demonstrates that the accuracy of the saturation adjustment assumption depends on aerosol concentration, and leads to an underestimation of AF in pristine environments.

Characterization of the indoor near-field and far-field aerosol transmission in a model commercial office building

To simulate the exposure potential of infectious aerosol such as SARS-CoV-2 in an office building setting, experimental studies for airborne particle transmission have been conducted in a model commercial office building at the Oak Ridge National Laboratory. The synthetic test aerosol particles had diameters similar to that of viral particles, in the nanometer size range of genetic fragments. Thus, the test aerosol provided a realistic representation of SARS-CoV-2 viral particle transmission. The study results, which are still being analyzed carefully at the present, suggest that in a door-closed single room setting, the heating, ventilating, and air-conditioning (HVAC) system can facilitate aerosol transmission, and 10 measuring points in a single room report the normalized concentration ranged from 0.45 – 0.66. Additionally, at a measuring point 6 feet away from the source, the aerosol concentration can reach a plateau normalized concentration of about 0.6 within 30 minutes. When interior doors were closed, aerosol particle transmission into adjacent rooms occurred through the building HVAC system, at a lower rate compared to the open-door scenario. If the interior doors were open, however, then the transmission into adjacent rooms depends on building indoor air movement and distance from the source. The building HVAC system provided an approximately less than 10% aerosol transmission rate, while transmission through a door opening can add up to 40% of transmission into adjacent rooms from the source location.FootnoteThis manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

Socioeconomic inequality in short birth interval in Ethiopia: a decomposition analysis

Background Short birth interval, defined as a birth-to-birth interval less than 33 months, is associated with adverse maternal and child outcomes. Evidence regarding the association of maternal socioeconomic status and short birth interval is inconclusive. Factors contributing to the socioeconomic inequality of short birth interval have also not been investigated. The current study assessed socioeconomic inequality in short birth interval and its contributing factors in Ethiopia. Methods Data from 8448 women collected in the 2016 Ethiopia Demographic and Health survey were included in the study. Socioeconomic inequality in short birth interval was the outcome variable. Erreygers normalized concentration index (ECI) and concentration curves were used to measure and illustrate socioeconomic-related inequality in short birth interval, respectively. Decomposition analysis was performed to identify factors explaining the socioeconomic-related inequality in short birth interval. Results The Erreygers normalized concentration index for short birth interval was − 0.0478 (SE = 0.0062) and differed significantly from zero (P < 0.0001); indicating that short birth interval was more concentrated among the poor. Decomposition analysis indicated that wealth quintiles (74.2%), administrative regions (26.4%), and not listening to the radio (5.6%) were the major contributors to the pro-poor socioeconomic inequalities in short birth interval. Conclusion There was a pro-poor inequality of short birth interval in Ethiopia. Strengthening the implementation of poverty alleviation programs may improve the population’s socioeconomic status and reduce the associated inequality in short birth interval.

Frother critical coalescence concentration and dose in flotation of copper-bearing carbonaceous shale

The paper presents the yield of carbon-and-cooper-bearing shale from the Legnica and Glogow Copper Basin flotation also called Kupferschiefer in the presence of ethylene, diethylene and trithylene glycol butyl ethers (C4E1, C4E2, C4E3) frothers characterized by frother normalized concentration that is ratio of the frother concentration, and its critical coalescence concentration expressed in different units. It was found that the oucome of flotation is identical provided that the frother concentration is expressed in milimoles per Mg.

Visual Binary Testing Of Hydrogen Sulfide Dissolved In Return Underground Local-Water Of Oil And Gas Condensate Fields

In order to screen samples of return underground local-water of oil and gas condensate fields for the presence of dissolved hydrogen sulfide, it was proposed to use single comparison sample for visual binary testing of H2S. Two indicator reactions occurring in solutions were selected — the formation of a stabilized suspension of MnS and CdS. Suspensions prepared in the presence of borate buffer (pH 9.18) and gelatin (stabilizer) are stable during the twenty four hours; a difference in the turbidity of suspensions can be observed near the normalized concentration of hydrogen sulfide (сlim = 15 mg L-1). When establishing the concentration of H2S in the comparison samples, a statistical approach was applied; the estimated values of the threshold concentration of H2S (ccomp.) are less than the normalized level on the value which providing the risk of a false-negative test result not more than 5% - 11.6 mg L-1 for MnS and 13.4 mg L-1 for CdS. Preference was given to a test system based on a stabilized suspension of CdS, because for this reaction, a narrower interval of unreliability and the value of ccomp. is nearer to the value of the сlim. The correctness of the visual binary testing of H2S in the samples of the analyzed water was confirmed by spectrophotometric method with p-phenylenediamine.

Influence of jet discharge velocity profile on CFD simulation of pump-around jet mixing tank

The present paper shows the effect of jet discharge velocity profile (or jet nozzle configuration) on CFD simulation of an open 45° inclined side entry pump-around jet mixing tank. The CFD model was carefully developed by using appropriate grid arrangement, boundary conditions, and numerical methods. The two different jet discharge velocity profiles, including top hat and fully developed profiles, were simulated by using the inlet mass flow rate of about 0.22 kg·s-1. The overall mixing times and normalized concentration profiles predicted by two different jet discharge velocity profiles were compared with the previous reliable experimental data. The results revealed that the different jet discharge velocity profiles resulted in different jet flow and mixing patterns inside the vessels.