Laboratory-scale Continuous-flow Reactor Research Articles

Continuous-Flow Aerobic Granular Sludge Treatment of Dairy Wastewater

The authors conducted a study on treating synthetic dairy wastewater using aerobic granular sludge (AGS) in a laboratory-scale continuous flow reactor (CFR) system. The system consisted of an anaerobic reactor, an aerobic reactor, and a settling sedimentation tank, with different hydraulic retention times tested over a 90-day period. The study monitored sludge characteristics and effluent treatment performance and found that the system achieved excellent removal rates for chemical oxygen demand and total carbon, exceeding 90%. As a result, the effluent met Portuguese laws for direct release into the water environment. Moreover, the study found that the AGS system improved the sludge sedimentation capacity from 272 to 80 mL/g, demonstrating its effectiveness as a viable treatment alternative for this type of effluent.

Conversion of guaiacol in supercritical water gasification: Detailed effect of feedstock concentration

The effect of feedstock concentration on the gasification characteristics of guaiacol, a model compound for lignin, in supercritical water was investigated using a laboratory-scale continuous-flow reactor. The reaction temperature, pressure, and residence time used were 600 °C, 25 MPa, and 94 s, respectively. A reaction model was developed and kinetic parameters were determined so that experimental results could be reproduced. The carbon gasification efficiency (CGE) and TOC yield were not affected by the initial concentration of guaiacol. Solid yields increased with feedstock concentration, reflecting an order of reaction greater than one for solid production. A reaction model was developed and the reaction rate constants were determined successfully to reproduce experimental results. The decomposition rate constant was determined as 0.0718 ± 0.0403 /s and was found to be in good agreement with the previous study. The reaction order for the solid production was determined to be 1.25.

Library synthesis of cardiomyogenesis inducing compounds using an efficient two-step-one-flow process

Within this work we telescoped a batch laboratory scale synthesis towards a two-step-one-flow process to synthesize cardiomyogenesis inducing compounds (4,6-diaminopyrimidines) in continuous manner. Special attention was put on a quick and robust screening protocol and subsequent UHPLC analysis. Finally, the robustness of the method was proven by the multi-gram synthesis of VUT-MK142 using a laboratory scale continuous flow reactor, enabling to deliver enough material for extensive biological testing.

Mass Transfer Characteristics of Floating Media in MBBR and IFAS Fixed-Film Systems

The goals of this project were to establish a standard protocol for measuring mass transfer rates in biofilm media, and to use the resulting data to develop and calibrate an empirical model. Two laboratory-scale continuous flow reactors were loaded with MBBR media donated from two manufacturers, and fed a synthetic wastewater free of organic carbon, but rich in ammonia. The reactors were aerated using coarse-bubble aeration, and operated at two different temperatures for one year. The continuous system was periodically halted to allow for batch testing of the media within each reactor. A total of 200 batch tests were conducted, at varying mixing rates, temperatures, bulk phase dissolved oxygen and ammonia concentrations. Data from the batch tests were used to develop an empirical model of ammonia mass transfer. The model includes half-order terms for bulk phase dissolved oxygen (DO) concentration and the mixing rate (expressed in terms of the velocity gradient), and an Arrhenius-type temperature dependence. A reasonable fit was obtained through non-linear regression, with an average root-mean-squared-error of less than 10% between model and observed ammonia flux rates. The protocol and resulting model were successfully used to compare the two media, and to project mass transfer within a nitrifying system. This title belongs to WERF Research Report Series ISBN: 9781780407050 (eBook)

Nitrate reduction in a simulated free-water surface wetland system

The feasibility of using a constructed wetland for treatment of nitrate-contaminated groundwater resulting from the land application of biosolids was investigated for a site in the southeastern United States. Biosolids degradation led to the release of ammonia, which upon oxidation resulted in nitrate concentrations in the upper aquifer in the range of 65–400 mg N/L. A laboratory-scale system was constructed in support of a pilot-scale project to investigate the effect of temperature, hydraulic retention time (HRT) and nitrate and carbon loading on denitrification using soil and groundwater from the biosolids application site. The maximum specific reduction rates (MSRR), measured in batch assays conducted with an open to the atmosphere reactor at four initial nitrate concentrations from 70 to 400 mg N/L, showed that the nitrate reduction rate was not affected by the initial nitrate concentration. The MSRR values at 22 °C for nitrate and nitrite were 1.2 ± 0.2 and 0.7 ± 0.1 mg N/mg VSS COD-day, respectively. MSRR values were also measured at 5, 10, 15 and 22 °C and the temperature coefficient for nitrate reduction was estimated at 1.13. Based on the performance of laboratory-scale continuous-flow reactors and model simulations, wetland performance can be maintained at high nitrogen removal efficiency (>90%) with an HRT of 3 days or higher and at temperature values as low as 5 °C, as long as there is sufficient biodegradable carbon available to achieve complete denitrification. The results of this study show that based on the climate in the southeastern United States, a constructed wetland can be used for the treatment of nitrate-contaminated groundwater to low, acceptable nitrate levels.

Polymer-supported titanate as catalyst for the transesterification of acrylic monomers

Transesterification of (meth)acrylic esters catalysed by alkyl titanates is an important industrial reaction. The current processes are homogeneous but heterogeneous alternatives are attractive for cost and environmental reasons. We have developed a straightforward and cost-effective synthesis of a polymer-supported titanium alkoxide catalyst involving cheap, readily available and relatively non-toxic chemicals, solvents and workup procedures. Efficiency and stability of the catalyst were tested in a laboratory-scale continuous flow reactor under equilibrium conditions for the preparation of N,N-dimethylaminoethylacrylate, a chemical of industrial interest. The results obtained indicate a good stability of the system to metal leaching on the long term.

Time‐Resolved In Situ Synchrotron X‐ray Study and Large‐Scale Production of Magnetite Nanoparticles in Supercritical Water

A general solution: In situ synchrotron X-ray scattering in a high-pressure pulsed injection reactor (see picture) shows that magnetite nucleation and growth are temporally separated. Gram-scale crystalline, pure phase, superparamagnetic magnetite nanoparticles were synthesized without surfactants in supercritical water in less than one hour using a laboratory-scale continuous-flow reactor.

An efficient, practical and cost-effective polymer-supported catalyst for the transesterification of methyl methacrylate by 1-butanol

A straightforward and cost-effective synthesis of a polymer-supported titanium alkoxide catalyst is reported. The described synthesis involves cheap, readily available and relatively non toxic chemicals, solvents and workup procedures. Efficiency and stability of the catalyst were tested in a laboratory-scale continuous flow reactor under equilibrium conditions over a month period. The average daily titanium leaching was estimated to less than 1% of the total amount of titanium engaged. To our knowledge, this result is the best obtained, to date, concerning the use of heterogeneous titanate for the catalysis of transesterification reactions.

MINERAL TRAPPING OF CO2VIA OIL SHALE ASH AQUEOUS CARBONATION: CONTROLLING MECHANISM OF PROCESS RATE AND DEVELOPMENT OF CONTINUOUS-FLOW REACTOR SYSTEM

-containing gas. As even minute amounts of extraneous substances present in water influence the extent and rate of lime solubility in water, the behavior of lime as the key component of ash in various conditions was studied and the mechanism of process deceleration was proposed. As the next step, a laboratory-scale continuous-flow reactor system for aqueous carbonation of oil shale ash and main considerations for industrial pilot-scale plant design were developed.

Effects of ammonium and nitrite on communities and populations of ammonia-oxidizing bacteria in laboratory-scale continuous-flow reactors

This study investigated the effects of ammonium and nitrite on ammonia-oxidizing bacteria (AOB) from an activated sludge process in laboratory-scale continuous-flow reactors. AOB communities were analyzed using specific PCR followed by denaturing gel gradient electrophoresis, cloning and sequencing of the 16S rRNA gene, and AOB populations were quantified using real-time PCR. To study the effect of ammonium, activated sludge from a sewage treatment system was enriched in four reactors receiving inorganic medium containing four different ammonium concentrations (2, 5, 10 and 30 mM NH(4) (+)-N). One of several sequence types of the Nitrosomonas oligotropha cluster predominated in the reactors with lower ammonium loads (2, 5 and 10 mM NH(4) (+)-N), whereas Nitrosomonas europaea was the dominant AOB in the reactor with the highest ammonium load (30 mM NH(4) (+)-N). The effect of nitrite was studied by enriching the enriched culture possessing both N. oligotropha and N. europaea in four reactors receiving 10-mM-ammonium inorganic medium containing four different nitrite concentrations (0, 2, 12 and 22 mM NO(2) (-)-N). Nitrosomonas oligotropha comprised the majority of AOB populations in the reactors without nitrite accumulation (0 and 2 mM NO(2) (-)-N), whereas N. europaea was in the majority in the 12- and 22-mM NO(2) (-)-N reactors, in which nitrite concentrations were 2.1-5.7 mM (30-80 mg N L(-1)).

Production of diethyl carbonate from ethanol and carbon monoxide over a heterogeneous catalytic flow reactor

Diethyl carbonate (DEC) is a candidate for use as an oxygen-containing additive in gasoline and diesel fuel to diminish pollutant emissions. The synthesis of DEC by the oxidative carbonylation of ethanol in the gas phase over heterogeneous CuCl 2/PdCl 2 catalysts supported on activated carbon (AC) has been investigated using a laboratory-scale continuous flow reactor with online GC/MS. Influences of various reaction conditions and catalyst pretreatment on the DEC yield and selectivity have been tested. Yield of DEC at 150 °C reached a maximum of 12.5 wt.% and was found to increase with an increase of residence time, reaction temperature, and reaction pressure as expected. The relationship between CO flow rate and production of DEC showed three distinct regions of DEC production. A by-product, diethoxymethane (DEM), was formed when ethanol was introduced in stoichiometric excess. Catalyst pretreated with KOH presented the best catalytic performance, and all metal hydroxides tested enhanced the yield of and selectivity for DEC simultaneously. However, the CuCl 2/PdCl 2/AC–KOH catalyst with a higher OH/Cu mole ratio than 2.0 showed an even lower DEC yield than that found using a CuCl 2/PdCl 2/AC catalyst without KOH.

Biotransformation of tetrachloroethylene by anaerobic attached-films at low temperatures

This study was conducted to examine the feasibility of using an anaerobic attached-film expanded-bed (AAFEB) process for the treatment of tetrachloroethylene (PCE) at 15°C. A laboratory-scale continuous-flow reactor, with an expanded-bed volume of 900 ml, was operated at hydraulic retention times of 1.8-4 h and influent PCE concentrations of 8–12 mg/l. Small samples (50 ml) of attached film media were used for batch testing 3–7 mg/l of PCE in a separate 300 ml AAFEB reactor. The attached films were a mixed anaerobic consortium grown on diatomaceous earth support particles under methanogenic conditions. Sucrose was used as an external electron donor and growth substrate. Reductive dechlorination of PCE to trichloroethylene (TCE), cis-1,2-dichloroethylene (DCE), vinyl chloride (VC) and ethylene (ETH) was observed. The conversion efficiency of PCE and TCE to lesser chlorinated compounds and ETH was above 98% during continuous-flow testing. VC accumulated as the major dechlorination product and ETH was produced at very low rates. The maximum PCE dechlorination rate, q max, was 5.33 mg PCE/g volatile solids-day (32.1 μmol/g VS-d) and the one-half velocity coefficient, K s, was 0.009 mg PCE/l (0.054 μM) under continuous-flow conditions. Since the AAFEB carried more than 20 g volatile solids per liter of bed, low temperature conversion rates would be expected to exceed 60 mg PCE/l bed-day. This indicates removal efficiencies greater than 99% could be obtained at hydraulic retention times of less than 1 h at ambient groundwater temperatures with this process.