Factors affecting arsenic and uranium removal with zero-valent iron: laboratory tests with Kanchan-type iron nail filter columns with different groundwaters

2014 ◽  
Vol 11 (5) ◽  
pp. 547 ◽  
Author(s):  
Christine B. Wenk ◽  
Ralf Kaegi ◽  
Stephan J. Hug
Keyword(s):  
Arsenic Removal ◽  
Filter Design ◽  
Operating Conditions ◽  
Zero Valent Iron ◽  
Design Parameters ◽  
Factors Affecting ◽  
Surface Areas ◽  
Water Composition ◽  
Removal Of Arsenic ◽  
Commercial Iron

Environmental context Tens of millions of people worldwide depend on groundwater with naturally high arsenic concentrations for drinking and cooking. We studied simple filters built with locally available and inexpensive iron nails, which can oxidise and bind arsenic in forming iron oxides and rust layers. Filters containing iron are being successfully applied in several regions, but efficiencies depend on the type of groundwater, and sufficiently large iron surfaces and contact times with water are needed for good arsenic removal. Abstract Zero-valent iron (ZVI)-based filters are able to remove arsenic and other pollutants from drinking water, but their performance depends on the form of ZVI, filter design, water composition and operating conditions. Kanchan filters use an upper bucket with ZVI in the form of commercial iron nails, followed by a sand filter, to remove arsenic and pathogens. We evaluated factors that influence the removal of arsenic and uranium with laboratory columns containing iron nails with six different synthetic groundwaters with 500μgL–1AsIII, 50μgL–1 U, 2mgL–1 B, and with 0 and 2mgL–1 P (added as o-phosphate), 0.25 and 2.5mM Ca, 3.2 and 8.3mM HCO3–, at pH 7.0 and 8.4 over 30 days. During the first 10 days, As removal was 65–95% and strongly depended on the water composition. As removal at pH 7.0 was better than at pH 8.4 and high P combined with low Ca decreased As removal. From 10–30 days, As removal decreased to 45–60% with all columns. Phosphate, in combination with low Ca concentrations lowered As removal, but had a slightly positive effect in combination with high Ca concentrations. U removal was only 10–70%, but showed similar trends. The drop in performance over time can be explained by decreasing release of iron to solution due to formation of layers of FeIII phases and calcite covering the iron surface. Mobile corrosion products contained ferrihydrite, Si-containing hydrous ferric oxides, and amorphous Fe–Si–P phases. Comparisons with another type of ZVI filter (SONO-filter) were used to evaluate filter design parameters. Higher ZVI surface areas and longer contact times should lead to satisfactory As removal with Kanchan-type filters.

A Parametric Examination of the Factors Affecting the Performance of a Diffusion Absorption Refrigeration System

2021 ◽  
pp. 1-38
Author(s):  
Noman Yousuf ◽  
Timothy Anderson ◽  
Roy Nates
Keyword(s):  
Waste Heat ◽  
Operating Conditions ◽  
Design Parameters ◽  
Working Fluid ◽  
Low Grade ◽  
Absorption Refrigeration ◽  
Factors Affecting ◽  
Thermally Driven ◽  
Mass Flowrate ◽  
Diffusion Absorption

Abstract Despite being identified nearly a century ago, the diffusion absorption refrigeration (DAR) cycle has received relatively little attention. One of the strongest attractions of the DAR cycle lies in the fact that it is thermally driven and does not require high value work. This makes it a prime candidate for harnessing low grade heat from solar collectors, or the waste heat from stationary generators, to produce cooling. However, to realize the benefits of the DAR cycle, there is a need to develop an improved understanding of how design parameters influence its performance. In this vein, this work developed a new parametric model that can be used to examine the performance of the DAR cycle for a range of operating conditions. The results showed that the cycle's performance was particularly sensitive to several factors: the rate of heat added and the temperature of the generator, the effectiveness of the gas and solution heat exchangers, the mass flowrate of the refrigerant and the type of the working fluid. It was shown that can deliver good performance at low generator temperatures if the refrigerant mass fraction in the strong solution is made as high as possible. Moreover, it was shown that a H2O-LiBr working pair could be useful for achieving cooling at low generator temperatures.

Effect of operating conditions on iron corrosion rates in zero-valent iron systems for arsenic removal

2009 ◽  
Vol 150 (2-3) ◽  
pp. 431-439 ◽  
Author(s):  
Juan M. Triszcz ◽  
Andrés Porta ◽  
Fernando S. García Einschlag
Keyword(s):  
Arsenic Removal ◽  
Operating Conditions ◽  
Zero Valent Iron ◽  
Iron Corrosion ◽  
Corrosion Rates

scholarly journals OPTIMAL CONTROL OF THE TRACTOR MOVEMENT

2020 ◽  
Author(s):  
E. Kalinin ◽  
◽  
M. Myasushka
Keyword(s):  
Optimal Control ◽  
Travel Speed ◽  
Gear Ratio ◽  
Operating Conditions ◽  
Design Parameters ◽  
Logic Device ◽  
Factors Affecting ◽  
Operating Modes ◽  
Methods Analytical ◽  
The Right

Goal of the study. Assessment of the possibility of optimizing tractor control by methods of automatic search for the optimum point. To achieve this goal, you must complete the following tasks: – to analyze the operating conditions of the tractor unit with the determination of the force factors affecting its operating conditions; – to develop a scheme and algorithm for the operation of the extreme regulator and analyze its functioning. Research methods. Analytical studies are based on methods of optimization of power factors acting on a tractor. The results of the study. An automatic regulator is considered, which provides an optimal ratio of the engine speed and the transmission gear ratio for each speed. The logic device generates a signal to change the power train ratio. The required travel speed of the tractor unit is set by the operator using the speed regulator. Changing the gear ratio changes the speed of the tractor. The signal of the deviation of the speed of movement, after amplification, provides an effect on the fuel supply and, by changing the revolutions of the crankshaft of the engine, brings the actual speed of the tractor to the set one. In the control system, the measurement of the amount of fuel consumed by the engine is carried out by a flow meter, and the measurement is carried out at certain intervals, and the current value is compared with the previous one. Reducing fuel consumption means that the influence on the change in gear ratio has been chosen in the right direction. Conclusions. The paper proposes a self-adjusting system. In a theoretical study of the possibility of optimal control of the tractor movement, equations are determined that are easily solved by the graphical analytical method. The graphical plotting determines the time the system reaches the optimal mode. The considered example of regulation of the power drive and the tractor engine does not exhaust the scope of application of self-adjusting systems. The operating modes of a number of units, as well as some interrelationships of design parameters, have static characteristics that ensure widespread use of these systems.

Removal of As from groundwater by in situ bioprecipitation and zero-valent iron

2013 ◽  
Vol 68 (9) ◽  
pp. 2055-2060
Author(s):  
A. Tkaczynska
Keyword(s):  
Particle Size ◽  
Iron Powder ◽  
Carbon Concentration ◽  
Zero Valent Iron ◽  
Batch Experiments ◽  
Synthetic Groundwater ◽  
Set Up ◽  
Removal Of Arsenic ◽  
Commercial Iron

The aim of this study was to evaluate the in situ bioprecipitation (ISBP) and zero-valent iron (ZVI) for removal of arsenic from groundwater. Batch experiments were set up to test the metal/oxyanion removal efficiency using the processes induced by ZVI, by ISBP and by combining both technologies. For the construction of microcosms in anaerobic condition, aquifer material was mixed with synthetic groundwater in serum bottles. Solutions that contained commercial iron (powder, filings), iron from foundry (chips) and lactate with the carbon concentration of 0.02% (w/v) were amended. After 57 days the pH increased to 7.9 in the microcosm with lactate + iron chips. In the microcosms amended with lactate + commercial iron (powder and filings), pH was between 6.9 and 7.5 The highest decrease in sulfate concentrations was observed in the microcosm supplied with lactate (from 1,976 to 630 mg/L), and with lactate + iron filings (from 1,985 to 1,280 mg/L). The results showed that ISBP and ZVI can be efficient in the removal of As from groundwater; however, it strongly depends on the type and particle size of ZVI. The most effective was commercial ZVI. The highest decrease in As concentration was observed in the microcosm supplied with ethanol and iron powder (from 4,832 to 131 μg/L).

scholarly journals Removal of Arsenic from Wet Scrubbing Wastewater

2016 ◽  
Vol 5 (2) ◽  
pp. 255
Author(s):  
Francesco Ferella ◽  
Ida De Michelis ◽  
Francesco Veglio
Keyword(s):  
Arsenic Removal ◽  
Operating Conditions ◽  
Iron Chloride ◽  
Optimum Operating ◽  
Optimum Process ◽  
Process Conditions ◽  
Calcium Arsenate ◽  
Wet Scrubbing ◽  
Negative Effect ◽  
Removal Of Arsenic

<p class="emsd-body"><span lang="EN-GB">Arsenic removal is hindered by its valence state. Addition of lime into wastewater containing arsenic gives benefits through the formation of low-soluble calcium arsenate, but the mechanism involved in the reduction of arsenic dissolution is not well known yet. Hence, in the present work different Ca/As ratios from 0 to 70% w/w were tested with the aim of finding the best conditions for removal of As from water (neutral tests) or solution (acid tests) containing sulphate ions. These solutions simulated aqueous streams coming from a wet scrubber for treatment of flue gas. Moreover, 5 g L<sup>-1</sup> of iron chloride were tested as additive in the acid tests. </span></p><p class="emsd-body"><span lang="EN-GB">In the optimum operating conditions, nearly 99% precipitation yield was obtained for both As(III) and As(V) in less than 1 h; the optimum process conditions were 10 g L<sup>-1</sup> of CaO without FeCl<sub>3</sub> for As(III) and 9 g L<sup>-1</sup> of CaO and 5 g <sup>-1</sup> FeCl<sub>3</sub> for As(V) in acid solutions. As regards neutral solutions, 1 g L<sup>-1</sup> of CaO is enough to precipitate around 99% of As(III) whereas the same result for As(V) is achieved by a higher CaO concentration (40 g L<sup>-1</sup>). Iron chloride had a negative effect on As(III) precipitation.</span></p>

scholarly journals First step concerning improvement of arsenic removal by adapted Kanchan filters in the lowlands of Nepal

2020 ◽  
pp. 01-09 ◽  
Author(s):  
Barbara Mueller
Keyword(s):  
Drinking Water ◽  
Ground Water ◽  
Removal Efficiency ◽  
Arsenic Removal ◽  
Arsenic Concentration ◽  
Operating Conditions ◽  
World Health ◽  
Water Composition ◽  
Keywords Arsenic ◽  
Health Organization

In the Terai region of Nepal (the southern lowlands of the country) the arsenic concentration of extracted ground water used as drinking water frequently exceeds the actual World Health Organization (WHO) drinking water guideline concentration of 10 μg/L. Single household filters (so called Kanchan filters) are employed to eliminate as from the well water. Being assembled to remove as utilizing zero-valent (ZVI) media, their efficiency was observed to vary to a high degree depending on design, ground water composition and the current operating conditions. Based on these concerns three field campaigns were organized in order to test ground water composition and filter handling on spot. This report depicts for the first time the results of this screening regarding removal efficiencies and clearly disclose future adaptation of the design and enhancement of the Kanchan filters uniquely used in Nepal. Removal efficiency varied between 5.81 % to 97.1 % depending on material, usage and mode of operation. The measurements of improvement include the replacement of nails and sand regularly; increasing the contact time between ground water and nails; preventing the nails from drying in order to maintain oxidizing settings; proper and regularly repeated instructions of the users. Keywords: Arsenic; Kanchan filters; Removal efficiency

Arsenic removal by MF membrane with chemical sludge adsorption and NF membrane equipped with vibratory shear enhanced process

2003 ◽  
Vol 3 (5-6) ◽  
pp. 303-310 ◽  
Author(s):  
S.-H. Yi ◽  
S. Ahmed ◽  
Y. Watanabe ◽  
K. Watari
Keyword(s):  
Arsenic Removal ◽  
Membrane Surface ◽  
Membrane Process ◽  
Low Concentrations ◽  
Strong Shear ◽  
Low Levels ◽  
Removal Processes ◽  
Removal Of Arsenic ◽  
Concentration Polarization Layer ◽  
Chemical Sludge

Conventional arsenic removal processes have difficulty removing low concentrations of arsenic ion from water. Therefore, it is very hard to comply with stringent low levels of arsenic, such as below 10 μg/L. So, we have developed two arsenic removal processes which are able to comply with more stringent arsenic regulations. They are the MF membrane process combined with chemical sludge adsorption and NF membrane process equipped with the vibratory shear enhanced process (VSEP). In this paper, we examine the performance of these new processes for the removal of arsenic ion of a low concentration from water. We found that chemical sludge produced in the conventional rapid sand filtration plants can effectively remove As (V) ions of H2AsO4- and HAsO42- through anion exchange reaction. The removal efficiency of MF membrane process combined with chemical sludge adsorption increased to about 36%, compared to MF membrane alone. The strong shear force on the NF membrane surface produced by vibration on the VSEP causes the concentration polarization layer to thin through increased back transport velocity of particles. So, it can remove even dissolved constituents effectively. Therefore, As (V) ions such as H2AsO4- and HAsO42- can be removed. The concentration of As (V) ions decreased from 50 μg/L to below 10 μg/L and condensation factor in recirculating water increased up to 7 times by using NF membrane equipped with VSEP.

scholarly journals Application of nanoscale zero-valent iron in hexavalent chromium-contaminated soil: A review

2020 ◽  
Vol 9 (1) ◽  
pp. 736-750
Author(s):  
Xilu Chen ◽  
Xiaomin Li ◽  
Dandan Xu ◽  
Weichun Yang ◽  
Shaoyuan Bai
Keyword(s):  
Heavy Metal ◽  
Hexavalent Chromium ◽  
Contaminated Soil ◽  
Zero Valent Iron ◽  
Toxic Heavy Metal ◽  
Factors Affecting ◽  
Metal Pollutants ◽  
Nanoscale Zero Valent Iron ◽  
Low Toxicity ◽  
Heavy Metal Pollutants

AbstractChromium (Cr) is a common toxic heavy metal that is widely used in all kinds of industries, causing a series of environmental problems. Nanoscale zero- valent iron (nZVI) is considered to be an ideal remediation material for contaminated soil, especially for heavy metal pollutants. As a material of low toxicity and good activity, nZVI has been widely applied in the in situ remediation of soil hexavalent chromium (Cr(vi)) with mobility and toxicity in recent years. In this paper, some current technologies for the preparation of nZVI are summarized and the remediation mechanism of Cr(vi)-contaminated soil is proposed. Five classified modified nZVI materials are introduced and their remediation processes in Cr(vi)-contaminated soil are summarized. Key factors affecting the remediation of Cr(vi)-contaminated soil by nZVI are studied. Interaction mechanisms between nZVI-based materials and Cr(vi) are explored. This study provides a comprehensive review of the nZVI materials for the remediation of Cr(vi)-contaminated soil, which is conducive to reducing soil pollution.

Impact of climatic conditions on the parameters of failure flow of military vehicles

2021 ◽  
pp. 095440702110202
Author(s):  
Nikolaj Dobrzinskij ◽  
Algimantas Fedaravicius ◽  
Kestutis Pilkauskas ◽  
Egidijus Slizys
Keyword(s):  
Climatic Factors ◽  
Armed Forces ◽  
Climatic Conditions ◽  
Operating Conditions ◽  
Technical Equipment ◽  
Factors Affecting ◽  
Military Vehicles ◽  
Equipment Reliability ◽  
Number Of Factors ◽  
The Impact

Relevance of the article is based on participation of armed forces in various operations and exercises, where reliability of machinery is one of the most important factors. Transportation of soldiers as well as completion of variety of tasks is ensured by properly functioning technical equipment. Reliability of military vehicles – armoured SISU E13TP Finnish built and HMMWV M1025 USA built were selected as the object of the article. Impact of climatic conditions on reliability of the vehicles exploited in southwestern part of the Atlantic continental forest area is researched by a case study of the vehicles exploitation under conditions of the climate of Lithuania. Reliability of military vehicles depends on a number of factors such as properties of the vehicles and external conditions of their operation. Their systems and mechanisms are influenced by a number of factors that cause different failures. Climatic conditions represent one of the factors of operating load which is directly dependent on the climate zone. Therefore, assessment of the reliability is started with the analysis of climatic factors affecting operating conditions of the vehicles. Relationship between the impact of climatic factors and failure flow of the vehicles is presented and discussed.

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