Iron Oxidation and Jarosite Precipitation in a Continuous Two-Stage 70°C Archaeal Bioreactor

2015 ◽  
Vol 1130 ◽  
pp. 230-233
Author(s):  
Anna H. Kaksonen ◽  
Christina Morris ◽  
Jason Wylie ◽  
Jian Li ◽  
Kayley Usher ◽  
...  
Keyword(s):  
Iron Oxidation ◽  
Volume Index ◽  
Redox Potentials ◽  
Continuous Stirred Tank Reactor ◽  
Two Stage ◽  
Dominant Form ◽  
Stage Design ◽  
Hydrometallurgical Processing ◽  
Co Precipitation ◽  
Cstr System

This study is the first demonstration of a continuous culture bio-catalysed iron oxidation and jarosite precipitation reactor using thermophilic archea, for use in hydrometallurgical process flow sheets. A two-stage continuous stirred tank reactor (CSTR) system comprised of two CSTRs, each with its own settler, was operated for biological iron oxidation and precipitation at 70°C. The two-stage design was to allow the growth of microorganisms that prefer various redox regimes. The bioreactors were inoculated with a mixed culture of extreme thermophilic iron oxidisers from genera Acidianus, Metallosphaera and Sulfolobus. The influent (pH 1.5) contained (g L-1) 15 Fe2+, 1.5 Cu, 1.5 Ni (all as sulfates), nutrients and trace elements. At a hydraulic retention time (HRT) of 6-7 h in each CSTR, the overall iron oxidation rate was 1.0±0.1 g L-1 h-1 and percent 97±2%. The pH values were 1.38±0.16 and 1.57±0.05, and redox potentials (Ag/AgCl reference) were474±47 mV and 575±1 mV, in CSTR1 and CSTR2, respectively. The percentages of influent Fe, Cu and Ni removed as precipitates from settlers were 52%, 0.46% and 0.03%, respectively. The precipitates were comprised of jarosite (100%), potassium jarosite being the dominant form (38-51%), followed by hydronium (30-35%), ammonium (13-18%) and sodium jarosites (6-9%). The precipitates had a sludge volume index of 5.8-19 mL g-1, indicating good settling properties facilitating easy removal through settling. The simultaneous and instantaneous addition of contaminants (g L-1: 2.0 Al, 0.05 As, 0.05 F, 0.2 Co, 5.0 Mg and 0.4 Mn), potentially contained in hydrometallurgical processing streams, into the influent decreased the iron oxidation (50% overall oxidation with HRT of 26-29 h in each CSTR) and jarosite content in precipitates (85-87%). In conclusion, the two-stage high-temperature CSTR system allowed iron oxidation and precipitation of the oxidised iron in the form of well settling jarosite with only minor loss of Cu and Ni via co-precipitation. However, the bioreactor performance was hampered by the introduction of other transition metals, fluoride and arsenic.

Two-Stage Airlift Bioreactor System for Efficient Iron Oxidation and Jarosite Precipitation

2013 ◽  
Vol 825 ◽  
pp. 242-245
Author(s):  
Anna H. Kaksonen ◽  
Christina Morris ◽  
Felipe Hilario ◽  
Suzy Rea ◽  
Jian Li ◽  
...  
Keyword(s):  
Large Scale ◽  
Iron Oxidation ◽  
High Rate ◽  
Airlift Bioreactor ◽  
Two Stage ◽  
Dominant Form ◽  
Unit Process ◽  
Reactor Kinetics ◽  
Stage System ◽  
Co Precipitation

Continuous high-rate iron oxidation and removal of jarosite precipitates from solution at low pH and ambient temperature and pressure was successfully demonstrated. The bio-catalysed iron oxidation and jarosite precipitation is promising as a unit process for a variety of hydrometallurgical process flow sheets, where it allows for iron removal from ferrous solutions without the requirement for chemical addition and with negligible base metal co-precipitation losses. The process demonstrated performance that could be used in a large scale industry unit. A two-stage airlift bioreactor (ALBR) system comprised of two ALBRs, each with its own settler, was operated for iron oxidation and precipitation at room temperature with a mixed culture of mesophilic iron oxidisers. The two-stage reactor design allowed for optimization of overall reactor kinetics by facilitating the growth of low (430 mV vs Ag/AgCl) and high (517 mV) redox potential iron oxidizers in the respective reactors. The influent (pH 1.5) contained (g L-1) 15 Fe2+, 1.5 Cu, 1.5 Ni, nutrients and trace elements. The hydraulic retention time (HRT) was decreased stepwise to evaluate process performance. With the lowest HRTs (8 h in ALBR1 and 10 h in ALBR2), the overall iron oxidation and precipitation rates of the two-stage system were 0.75 ± 0.02 g L-1 h-1 and 0.15 ± 0.01 g L-1 h-1, respectively and overall iron oxidation and precipitation efficiencies of 94 ± 3% and 18 ± 1 %, respectively. The percent of influent Fe, S, Cu and Ni removed as precipitates from settlers were 30.9%, 16.7%, 1.1% and 0.2%, respectively. The precipitates were predominately comprised of (>95%) jarosite with potassium jarosite being the dominant form, followed by hydronium, ammonium and sodium jarosites. In conclusion, the two-stage ALBR system allowed efficient iron oxidation and precipitation of the oxidised iron as well settling jarosite with only minor loss of Cu and Ni via co-precipitation.

scholarly journals Quadratic Model-Based Dynamically Updated PID Control of CSTR System with Varying Parameters

Algorithms ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 31
Author(s):  
Dushko Stavrov ◽  
Gorjan Nadzinski ◽  
Stojche Deskovski ◽  
Mile Stankovski
Keyword(s):  
Pid Control ◽  
Pid Controller ◽  
Absolute Error ◽  
Error Model ◽  
Quadratic Model ◽  
Control Performance ◽  
Continuous Stirred Tank Reactor ◽  
Quadratic Error ◽  
Varying Parameters ◽  
Cstr System

In this paper, we discuss an improved version of the conventional PID (Proportional–Integral–Derivative) controller, the Dynamically Updated PID (DUPID) controller. The DUPID is a control solution which preserves the advantages of the PID controller and tends to improve them by introducing a quadratic error model in the PID control structure. The quadratic error model is constructed over a window of past error points. The objective is to use the model to give the conventional PID controller the awareness needed to battle the effects caused by the variation of the parameters. The quality of the predictions that the model is able to deliver depends on the appropriate selection of data used for its construction. In this regard, the paper discusses two algorithms, named 1D (one dimensional) and 2D (two dimensional) DUPID. Appropriate to their names, the former selects data based on one coordinate, whereas the latter selects the data based on two coordinates. Both these versions of the DUPID controller are compared to the conventional PID controller with respect to their capabilities of controlling a Continuous Stirred Tank Reactor (CSTR) system with varying parameters in three different scenarios. As a quantifying measure of the control performance, the integral of absolute error (IAE) metric is used. The results from the performed simulations indicated that the two versions of the DUPID controller improved the control performance of the conventional PID controller in all scenarios.

Tubular electrostatic precipitators of two-stage design

1981 ◽  
Vol 6 (1-6) ◽  
pp. 239-244 ◽  
Author(s):  
Harish S. Surati ◽  
Michael R. Beltran ◽  
Isaac Raigorodsky
Keyword(s):  
Two Stage ◽  
Stage Design ◽  
Electrostatic Precipitators ◽  
Two Stage Design

scholarly journals Two-Stage Single-Arm Trials Are Rarely Analyzed Effectively or Reported Adequately

2021 ◽  
pp. 1813-1820
Author(s):  
Michael J. Grayling ◽  
Adrian P. Mander
Keyword(s):  
Final Stage ◽  
Interim Analysis ◽  
Primary Outcome ◽  
Point Estimate ◽  
Two Stage ◽  
Stage Design ◽  
Patient Subgroup ◽  
Future Studies ◽  
Point Estimates ◽  
Outcome Trial

PURPOSE Two-stage single-arm designs have historically been the most common design used in phase II oncology. They remain a mainstay today, particularly for trials in rare subgroups. Consequently, it is imperative such studies be designed, analyzed, and reported effectively. We comprehensively review such trials to examine whether this is the case. METHODS Oncology trials that used Simon's two-stage design over a 5-year period were identified and reviewed. They were evaluated for whether they reported sufficient design (eg, required sample size) and analysis (eg, CI) details. Articles that did not adjust their inference for the incorporation of an interim analysis were also reanalyzed. RESULTS Four-hundred twenty-five articles were included. Of these, just 47.5% provided the five components that ensure design reproducibility. Only 1.2% and 2.1% reported an adjusted point estimate or CI, respectively. Just 55.3% provided the final stage rejection bound, indicating many trials did not test a hypothesis for their primary outcome. Trial reanalyses suggested reported point estimates underestimated treatment effects and reported CIs were too narrow. CONCLUSION Key design details of two-stage single-arm trials are often unreported. Their inference is rarely performed such as to remove bias introduced by the interim analysis. These findings are particular alarming when considered against the growing trend in which nonrandomized trials make up a large proportion of all evidence on a treatment's effectiveness in a rare biomarker-defined patient subgroup. Future studies must improve the way they are analyzed and reported.

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