Emulsion liquid membrane (ELM) enhanced by nanoparticles and ionic liquid for extracting vanadium ions from wastewater.

Emulsion liquid membrane (ELM) stands out as an extraction process that has drawn much attention due to its promising prospects in industrial wastewater treatment technology. Nevertheless, the pivotal challenge is to reach high membrane stability to overcome the obstacle of applying ELM at the industrial scale. In this study, ELM was boosted by using nanoparticles (superparamagnetic iron oxide (Fe2O3)) in the stripping phase (W1) and ionic liquid (1-methyl-3-octyl-imidazolium-hexafluorophosphate [OMIM][PF6) in the oil phase (O) for recovering/extracting vanadium from synthetic wastewater to near completion and at the same time enhancing emulsion stability to be appropriate for industrial application. The vanadium recovery/extraction percentage has been raised significantly in 3 min to 99.6% when adding 0.01% (w/w) Fe2O3 NPs (20 to 50 nm in size) in the internal phase (W1) and 5% (v/v) [OMIM]PF6 ionic liquid in the oil phase (O). Also, the emulsion stability was considerably improved, and the leakage percentage was reduced to 16% after 3 days. The results of this study could be used in the future to remove additional heavy metal ions from industrial effluents.

GEANT4 Simulation for Radioactive Particle Tracking (RPT) Technique.

In the past two decades, the radioactive particle tracking (RPT) measurement technique has been proven to visualize flow fields of most multiphase flow systems of industrial interest. The accuracy of RPT, and hence the data obtained, depend largely on the calibration process, which stands here as a basis for two subsequent processes: tracking and reconstruction. However, limitations in the RPT calibration process can be found in different experimental constrains and in assumptions made in the classical Monte Carlo approach used to simulate number of counts received by the detectors. Therefore, in this work, we applied a GEANT4-based Monte Carlo code to simulate the RPT calibration process for an investigated multiphase flow system (i.e., gas-liquid bubble column). The GEANT4 code was performed to simulate the number of counts received by 28 scintillation detectors for 931 known tracer positions while capturing all the types of photon interaction and overcoming solids' angle limitations in classical approaches. The results of the simulation were validated against experimental data obtained using an automated RPT calibration device. The results showed a good agreement between the simulated and experimental counts, where the maximum absolute average relative deviation detected was about 5%. The GEANT4 model typically predicted the number of counts received by all the detectors; however, it over-estimated the counts when the number of primary events applied in the model was not the optimal.

X-ray digital industrial radiography (DIR) for local liquid velocity (V(LL)) measurement in trickle bed reactors (TBRs): validation of the technique.

Local liquid velocity measurements in Trickle Bed Reactors (TBRs) are one of the essential components in its hydrodynamic studies. These measurements are used to effectively determine a reactor's operating condition. This study was conducted to validate a newly developed technique that combines Digital Industrial Radiography (DIR) with Particle Tracking Velocimetry (PTV) to measure the Local Liquid Velocity (V(LL)) inside TBRs. Three millimeter-sized Expanded Polystyrene (EPS) beads were used as packing material. Three validation procedures were designed to test the newly developed technique. All procedures and statistical approaches provided strong evidence that the technique can be used to measure the V(LL) within TBRs.

Airlift column photobioreactors for Porphyridium sp. culturing: part I. effects of hydrodynamics and reactor geometry.

Photosynthetic microorganisms have been attracting world attention for their great potential as renewable energy sources in recent years. Cost effective production in large scale, however, remains a major challenge to overcome. It is known to the field that turbulence could help improving the performance of photobioreactors due to the so-called flashing light effects. Better understanding of the multiphase fluid dynamics and the irradiance distribution inside the reactor that cause the flashing light effects, as well as quantifying their impacts on the reactor performance, thus, are crucial for successful design and scale-up of photobioreactors. In this study, a species of red marine microalgae, Porphyridium sp., was grown in three airlift column photobioreactors (i.e., draft tube column, bubble column, and split column). The physical properties of the culture medium, the local fluid dynamics and the photobioreactor performances were investigated and are reported in this part of the manuscript. Results indicate that the presence of microalgae considerably affected the local multiphase flow dynamics in the studied draft tube column. Results also show that the split column reactor works slightly better than the draft tube and the bubble columns due to the spiral flow pattern inside the reactor.

Airlift column photobioreactors for Porphyridium sp. culturing: Part II. verification of dynamic growth rate model for reactor performance evaluation.

Dynamic growth rate model has been developed to quantify the impact of hydrodynamics on the growth of photosynthetic microorganisms and to predict the photobioreactor performance. Rigorous verification of such reactor models, however, is rare in the literature. In this part of work, verification of a dynamic growth rate model developed in Luo and Al-Dahhan (2004) [Biotech Bioeng 85(4): 382-393] was attempted using the experimental results reported in Part I of this work and results from literature. The irradiance distribution inside the studied reactor was also measured at different optical densities and successfully correlated by the Lambert-Beer Law. When reliable hydrodynamic data were used, the dynamic growth rate model successfully predicted the algae's growth rate obtained in the experiments in both low and high irradiance regime indicating the robustness of this model. The simulation results also indicate the hydrodynamics is significantly different between the real algae culturing system and an air-water system that signifies the importance in using reliable data input for the growth rate model.

Effect of shear on performance and microbial ecology of continuously stirred anaerobic digesters treating animal manure.

We determined the effect of different mixing intensities on the performance, methanogenic population dynamics, and juxtaposition of syntrophic microbes in anaerobic digesters treating cow manure from a dairy farm. Computer automated radioactive particle tracking in conjunction with computational fluid dynamics was performed to quantify the shear levels locally. Four continuously stirred anaerobic digesters were operated at different mixing intensities of 1,500, 500, 250, and 50 revolutions per min (RPM) over a 260-day period at a temperature of 34 +/- 1 degrees C. Animal manure at a volatile solids (VS) concentration of 50 g/L was fed into the digesters daily at five different organic loading rates between 0.6 and 3.5 g VS/L day. The different mixing intensities had no effect on the biogas production rates and yields at steady-state conditions. A methane yield of 0.241 +/- 0.007 L CH(4)/g VS fed was obtained by pooling the data of all four digesters during steady-state periods. However, digester performance was affected negatively by mixing intensity during startup of the digesters, with lower biogas production rates and higher volatile fatty acids concentrations observed for the 1,500-RPM digester. Despite similar methane production yields and rates, the acetoclastic methanogenic populations were different for the high- and low-intensity mixed digesters with Methanosarcina spp. and Methanosaeta concilii as the predominant methanogens, respectively. For all four digesters, epifluorescence microscopy revealed decreasing microbial floc sizes beginning at week 4 and continuing through week 26 after which no microbial flocs remained. This decrease in size, and subsequent loss of microbial flocs did not, however, produce any long-term upsets in digester performance.

Mesophilic digestion kinetics of manure slurry.

Anaerobic digestion kinetics study of cow manure was performed at 35 degrees C in bench-scale gas-lift digesters (3.78 l working volume) at eight different volatile solids (VS) loading rates in the range of 1.11-5.87 g l-1 day-1. The digesters produced methane at the rates of 0.44-1.18 l l-1 day-1, and the methane content of the biogas was found to increase with longer hydraulic retention time (HRT). Based on the experimental observations, the ultimate methane yield and the specific methane productivity were estimated to be 0.42 l CH4 (g VS loaded)-1 and 0.45 l CH4 (g VS consumed)-1, respectively. Total and dissolved chemical oxygen demand (COD) consumptions were calculated to be 59-17% and 78-43% at 24.4-4.6 days HRTs, respectively. Maximum concentration of volatile fatty acids in the effluent was observed as 0.7 g l-1 at 4.6 days HRT, while it was below detection limit at HRTs longer than 11 days. The observed methane production rate did not compare well with the predictions of Chen and Hashimoto's [1] and Hill's [2] models using their recommended kinetic parameters. However, under the studied experimental conditions, the predictions of Chen and Hashimoto's [1] model compared better to the observed data than that of Hill's [2] model. The nonlinear regression analysis of the experimental data was performed using a derived methane production rate model, for a completely mixed anaerobic digester, involving Contois kinetics [3] with endogenous decay. The best fit values for the maximum specific growth rate (micro m) and dimensionless kinetic parameter (K) were estimated as 0.43 day-1 and 0.89, respectively. The experimental data were found to be within 95% confidence interval of the prediction of the derived methane production rate model with the sum of residual squared error as 0.02.

Gas-lift digester configuration effects on mixing effectiveness.

Computational fluid dynamics simulations were used to study the effect of bottom configuration and a hanging baffle on the mixing inside a gas-lift digester filled with non-Newtonian sludge. The Navier-Stokes and continuity equations were solved numerically using commercially available finite element method-based solver. The results from this simulation were found to be in good agreement with previously reported experimental findings. At a gas recirculation rate of 84.96l/h, the poorly mixed zones inside a flat bottom digester were about 33.6% of the digester volume, while in the case of digesters with 25 degrees and 45 degrees conical bottoms poorly mixed zones were about 31.9% and 29.6%, respectively. The power law viscosity index, n, did not have a significant effect on the mixing pattern under the conditions studied. Introduction of a hanging baffle in combination with a 45 degrees hopper bottom resulted in reduction of the poorly mixed zone by a factor of three compared to a flat bottom without baffle configuration. Although the introduction of a hanging baffle was able to significantly reduce the size of the poorly mixed zones inside a gas-lift digester, further optimization of the digester geometry may lead to additional improvements.

Methane production in a 100-L upflow bioreactor by anaerobic digestion of farm waste.

Manure waste from dairy farms has been used for methane production for decades, however, problems such as digester failure are routine. The problem has been investigated in small scale (1-2 L) digesters in the laboratory; however, very little scale-up to intermediate scales are available. We report production of methane in a 100-L digester and the results of an investigation into the effect of partial mixing induced by gas upflow/recirculation in the digester. The digester was operated for a period of about 70 d (with 16-d hydraulic retention time) with and without the mixing induced by gas recirculation through an internal draft tube. The results show a clear effect of mixing on digester operation. Without any mixing, the digester performance deteriorated within 30-50 d, whereas with mixing continuous production of methane was observed. This study demonstrates the importance of mixing and its critical role in design of large scale anaerobic digesters.

Methane production in a 100-L upflow bioreactor by anaerobic digestion of farm waste.

Manure waste from dairy farms has been used for methane production for decades, however, problems such as digester failure are routine. The problem has been investigated in small scale (1-2 L) digesters in the laboratory; however, very little scale-up to intermediate scales are available. We report production of methane in a 100-L digester and the results of an investigation into the effect of partial mixing induced by gas upflow/recirculation in the digester. The digester was operated for a period of about 70 d (with 16-d hydraulic retention time) with and without the mixing induced by gas recirculation through an internal draft tube. The results show a clear effect of mixing on digester operation. Without any mixing, the digester performance deteriorated within 30-50 d, whereas with mixing continuous production of methane was observed. This study demonstrates the importance of mixing and its critical role in design of large scale anaerobic digesters.

Production of bioenergy and biochemicals from industrial and agricultural wastewater.

The building of a sustainable society will require reduction of dependency on fossil fuels and lowering of the amount of pollution that is generated. Wastewater treatment is an area in which these two goals can be addressed simultaneously. As a result, there has been a paradigm shift recently, from disposing of waste to using it. There are several biological processing strategies that produce bioenergy or biochemicals while treating industrial and agricultural wastewater, including methanogenic anaerobic digestion, biological hydrogen production, microbial fuel cells and fermentation for production of valuable products. However, there are also scientific and technical barriers to the implementation of these strategies.

Analyzing and modeling of photobioreactors by combining first principles of physiology and hydrodynamics.

Mixing in photobioreactors is known to enhance biomass productivity considerably, and flow dynamics play a significant role in the reactor's performance, as they determine the mixing and the cells' movement. In this work we focus on analyzing the effects of mixing and flow dynamics on the photobioreactor performance. Based on hydrodynamic findings from the CARPT(Computer Automated Radioactive Particle Tracking) technique, a possible mechanism for the interaction between the mixing and the physiology of photosynthesis is presented, and the effects of flow dynamics on light availability and light intensity fluctuation are discussed and quantitatively characterized. Furthermore, a dynamic modeling approach is developed for photobioreactor performance evaluation, which integrates first principles of photosynthesis, hydrodynamics, and irradiance distribution within the reactor. The results demonstrate the reliability and the possible applicability of this approach to commercially interesting microalgae/cyanobacteria culture systems.