Inverse Fluidized Bed Reactor Research Articles

Modelling selenite and chemical oxygen demand removal in an inverse fluidized bed bioreactor using genetic algorithm optimized artificial neural network

AbstractBACKGROUNDA genetic algorithm (GA) optimized artificial neural network (ANN) model was developed to simulate selenite removal efficiency (SRe) and chemical oxygen demand (COD) removal efficiency (CRe) in a single‐stage inverse fluidized bed reactor (IFBR) operated under different hydraulic retention time (HRT) (12–48 h), and inlet selenite concentration (12.7–635 mg L−1). Multi‐objective optimization for SRe and CRe with the ANN model was adopted to estimate the pareto optimal solutions in the bioreactor system.RESULTSGA optimized ANN topology suggested five neurons in the hidden layer, and the optimal data partitioning between training, test, and validation subsets (in 70:15:15 ratio) using cross‐validation. The average fitness for SRe and CRe of the resulting ANN model over training (R2 = 0.885), test (R2 = 0.967) and validation (R2 = 0.972) subsets were reasonably good. Sensitivity analysis suggested an increase in SRe and CRe with HRT, while an increase in inlet selenite concentration had a negative effect on SRe. Local interpretable model‐agnostic explanations and SHapley Additive exPlanations for the developed model suggested a positive coefficient of the predictors on CRe. Pareto optimal solution for SRe (92.87%–95.26%), and CRe (91.33%–99.35%) were suggested for HRT and inlet selenite concentration varying between 35.67 h and 36 h, and 0.1 g L−1 and 0.884 g L−1, respectively.CONCLUSIONSThe GA optimized ANN model could be exploited for the prediction of contaminant removal efficiencies in the bioreactor system with a fair degree of complexity (i.e., IFBR). Multiple objective pareto optimal solutions can identify the best operating conditions relevant for wastewater treatment. © 2023 Society of Chemical Industry (SCI).

A critical review of inverse fluidized bed reactors-start-up optimization strategies and wastewater treatment.

A critical evaluation of strategies used for reducing start-up time and biological wastewater treatment using an inverse fluidized bed reactor (IFBR) was done. The start-up of an IFBR is one of the most important, time-consuming, and limiting steps in wastewater treatment using biofilm reactors. Evaluation of different strategies used by various researchers is helpful in future research works with this reactor. Different types of treated wastewater, the effect of wastewater characteristics, carriers used, and reactor hydrodynamics on the reactor performance were reviewed in detail in the first part. The second part of this review covers the use of an IFBR in the biological treatment of different wastewaters through multiple biochemical pathways and how it helped improve performance compared to other reactors. This will enable the researchers to understand the novelty of an IFBR for wastewater treatment and allow them to use it as a potential reactor.

Condition-Based Maintenance of an Anaerobic Reactor Using Artificial Intelligence

This paper proposes a condition-based maintenance system based on artificial intelligence for an online monitoring system of the support bed expansion in a 30-liter pilot-scale inverse fluidized bed reactor (IFBR). The main scope is to achieve a condition-based maintenance strategy using a single-level sensor for a biofilm inverse fluidizing bed as source for virtual sensors. The implementation of an artificial neural network was performed on an embedded electronic system (Raspberry Pi 4), both working together in real time. The signals estimated by the neural network are compared against the signals measured by the hardware sensors and, in case of detecting a failure in the physical measurement system, the artificial intelligence-based system then uses the signal estimated by the artificial neural network to maintain the correct operation of the IFBR. This system uses an artificial neural network to estimate the COD concentration of the effluent and the biogas production flow of a bioreactor, from the measurement of pH, the COD concentration of the influent, the inflow to the bioreactor and the signal coming from each of the conductivity sensors installed inside the reactor, which provide information about support media expansion in a pilot-scale inverse fluidized bed reactor. In addition, a fuzzy PI controller is presented, which was implemented in a Raspberry Pi electronic card, to regulate the COD concentration in the effluent of the bioreactor used as a case study.

Hydrodynamics of a bubble-induced inverse fluidized bed reactor with a nanobubble tray

This paper reports on the hydrodynamics of a bubble-induced inverse fluidized bed reactor, using a nanobubble tray gas distributor, where solid particles are fluidized only by an upward gas flow. Increasing the gas velocity, the fixed layer of particles initially packed at the top of the liquid starts to move downwards, due to the rise of bubbles in this system, and then gradually expands downwards until fully suspended. The axial local pressure drops and standard deviation were examined to delineate the flow regime comprehensively under different superficial gas velocities. Four flow regimes (fixed bed regime, initial fluidization regime, expanded regime, and post-homogeneous regime) were observed and three transitional gas velocities (the initial fluidization velocity, minimum fluidization velocity, and homogeneous fluidization velocity) were identified to demarcate the flow regime. Three correlations were developed for the three transitional velocities. As the fine bubbles generated from the nanobubble tray gas distributor are well distributed in the entire column, the bed expansion process of the particles is relatively steady.

Studies on the feasibility of bisphenol-A removal and its kinetics using Pseudomonas aeruginosa in both flask and an inverse fluidized bed reactor

A rapid increase in global industrialization has resulted in the extensive use of bisphenol-A (BPA). The presence of BPA in the environment resulting from the discharge of industrial effluents affects the quality of surrounding land and water bodies. Continuous exposure of BPA into the environment affects human health because BPA is an endocrine-disrupting chemical. Therefore, the removal of BPA has become considerably crucial to protect the environment and human health. This study examined the effect of the most important parameters, namely pH, temperature, inoculum size, and substrate concentration, on BPA removal. Pseudomonas aeruginosa was used in this study, under free (non-immobilized) and immobilized conditions. Batch experiments using an Erlenmeyer flask were conducted to optimize conditions for the maximum removal of BPA. A BPA concentration of 0.2 mg/mL, inoculum size of 0.8 mL, a temperature of 35 °C, and a pH of 7 were the optimum conditions for the maximum BPA removal. Under these conditions, the maximum BPA removal was observed in immobilized P. aeruginosa compared with non-immobilized cells (free cells of P. aeruginosa). Furthermore, the feasibility of BPA removal on a large scale was determined using an inverse fluidized bed reactor (IFBR) with a working volume of 4 L and polypropylene as the carrier material operating under a batch mode. Hydrodynamic and mass transfer experiments were performed, and operating parameters, namely superficial gas velocity, percentage of bed expansion, and holdups, were optimized. The rate constants were calculated as 0.011 and 0.0946 h−1 in IFBR and Erlenmeyer flask experiments, respectively.

Investigation of hydrodynamics of inverse fluidized bed reactor (IFBR) for struvite (NH4MgPO4·6H2O) recovery from urban wastewater

Investigation of hydrodynamics of inverse fluidized bed reactor (IFBR) for struvite (NH4MgPO4·6H2O) recovery from urban wastewater

Assessment of inverse fluidized bed reactor on the treatment efficiency of distillery spent wash water

Assessment of inverse fluidized bed reactor on the treatment efficiency of distillery spent wash water

Struvite recovery from human urine in inverse fluidized bed reactor and evaluation of its fertilizing potential on the growth of Arachis hypogaea

Nutrients, nitrogen and phosphorus, present in wastewater need to be removed to protect water bodies from the consequences of eutrophication. Among the many possibilities, recovering the nutrients as struvite has become attractive, particularly from the isolated sources of urine stream considering its potential use as a fertilizer akin to Diammonium phosphate (DAP). The present paper deals with studies on the production of struvite from synthetic human urine using an inverse fluidized bed reactor (IFBR) based on the batch process results. Unlike the 85% recovery of struvite for the optimized molar ratios of magnesium, ammonium and phosphate at pH 9.5, the IFBR experiments yielded approximately 95% recovery at optimal operating parameters with respect to condition, size of low density polypropylene particles (6 mm) with density (963 kg/m3) and bed height (45 cm). The purity and microstructure were examined using XRD, SEM / EDS, and Raman spectroscopy. The fertilization efficiency was assessed with struvite application and integrated with nitrogen-fixing Azospirullum rhizobium and phosphate-solubilizing Bacillus megaterium on the growth of Arachis hypogaea plants in the field. Studies conducted along with commonly used DAP on sandy topsoil indicated efficient absorption of struvite by microbes and providing the most encouraging number of seed/pod (capsule) and straw yields (g/plant) comparable to conventional superphosphate DAP. The nutrient availability in the soil was confirmed based on the soil properties before and after harvest. Extensive tests of the plant properties proved the positive agronomic results of struvite fertilization.

CFD study of the hydrodynamics and biofilm growth effect of an anaerobic inverse fluidized bed reactor operating in the laminar regime

The unsteady laminar flow of an inverse fluidized bed reactor was addressed in this study using computational fluid dynamics (CFD). Three-dimensional (3D) and two-dimensional (2D) simulations were carried out using the Eulerian-Eulerian approach with the Syamlal O'Brien and Gidaspow models for modeling the drag between the solid and liquid phases. Reported data of solids expansion and bed porosity were used to validate the simulations. Results show that 2D simulations can satisfactorily reproduce experimental data of fluidized bed reactors, which are essentially equal to those obtained on 3D simulations. The model of Syamlal O'Brien was found to be in better agreement with experiments than that of Gidaspow. It is shown that commonly used correlations for predicting bed porosity fail to provide a reasonable overall description of the evaluated operating conditions. The flow patterns for both phases in the bed section exhibit chaotic recirculation zones with high values of shear stress, and after this, the flow quickly becomes fully developed. The effect of biofilm thickness increase on bed porosity, under similar apparent densities of colonized particles reported for this system, is analyzed. Biofilm growth generates a decrease in the Archimedes number (i.e., decreases the buoyancy of particles) and an increase in the particle Reynolds numbers (Rep), affecting significantly the final porosity of the bed. However, this effect vanishes for Rep < 0.25. Results from this work can be used to develop scale‐up criteria and to establish safe operating conditions (e.g., maximum liquid velocity and biofilm thickness) to avoid loss of support particles.

Continuous removal and recovery of metals from wastewater using inverse fluidized bed sulfidogenic bioreactor

Acid mine drainage (AMD) is a serious environmental hazard in many countries with historic or ongoing mining industries. Biological sulfide precipitation is an emerging technique for both removal and recovery of heavy metals from such wastewater. This study demonstrated heavy metal removal and recovery from synthetic wastewater containing Cd2+, Cu2+, Fe3+, Ni2+, Pb2+ and Zn2+ using two continuously operated sulfidogenic anaerobic inverse fluidized bed reactors (referred as R1 and R2) supplied with an influent of pH 7.0 and 3.0, respectively. In case of R1, more than 95% metal removal efficiency was achieved for all the metals except for Fe3+ (90%) and Ni2+ (85%), and in case of R2 the removal was more than 90% for all the metals except with Fe3+ (88%) and Ni2+ (82%). The metals were subsequently recovered in the form of metal nanopowder from the reactor bottom and equalizer, and the metal recovery was in the order: Cu > Pb > Cd > Zn > Ni > Fe. However R1 yielded a good recovery percentage (50–65%) of the metals in comparison with the reactor supplied with influent of pH 3.0 (46–55%). The presence of immobilized sulfate reducing bacteria onto the support material in the bioreactors were identified using field emission scanning electron microscopy. The size and shape of the biometal nanoparticles were confirmed using field emission transmission electron microscopy, which revealed their excellent potential for industrial application. This study demonstrates successful recovery of metal sulfides in the form of nanoparticles using IFBR.

Effect of nickel on the comparative performance of inverse fluidized bed and continuously stirred tank reactors for biogenic sulphur-driven autotrophic denitrification

The comparative performance of an inverse fluidized bed reactor (IFBR) having high density polyethylene beads as carrier materials for biofilm formation and a continuous stirred tank reactor (CSTR), both maintaining autotrophic denitrification using biogenic sulphur (ADBIOS) in the absence and presence of nickel (Ni2+), was studied. The reactors were compared in terms of NO3−-N and NO2−-N removal and SO42--S production throughout the study. A simulated wastewater with an inlet NO3−-N concentration of 225 mg/L and a decreasing concentration of biogenic sulphur (bio-S) from 1.5 to 0.375 g/L was used. Both reactors were operated at a hydraulic retention time (HRT) of 48 h for 140 days and at an HRT of 42 h for the following 68 days. A more efficient ADBIOS was observed in the CSTR than IFBR throughout the study due to a better mixing of the feed wastewater in the bulk liquid and a higher availability of bio-S to the suspended cells. The NO3−-N removal efficiency in the IFBR decreased by approximately 41% when the feed bio-S was reduced to 0.375 g/L, while it remained unaffected in the CSTR. Conversely, the presence of Ni2+ did not significantly affect NO3−-N removal in both reactors even at a feed Ni2+ concentration of 120 mg/L. The highest NO3−-N removal rates achieved were 86 and 108 mg NO3−-N/(L·day) in the IFBR and CSTR, respectively, in the presence of 120 mg/L of feed Ni2+ at an HRT of 42 h. Batch studies conducted with acclimatized biomass showed that the continuous-flow operation mode in both reactors played a major role in helping the autotrophic denitrifiers to tolerate Ni2+ toxicity.

Electrical Conductivity for Monitoring the Expansion of the Support Material in an Anaerobic Biofilm Reactor

This article describes the use of the electrical conductivity for measuring bed expansion in a continuous anaerobic biofilm reactor in order to prevent the exit of support material from the reactor with the consequent loss of biomass. The substrate used for the tests is obtained from a two-stage anaerobic digestion (AD) process at the pilot scale that treats the liquid fraction of fruit and vegetable waste (FVW). Tests were performed with the raw substrate before anaerobic treatment (S1), the effluent from the hydrolysis reactor (S2), and the effluent from the methanogenic reactor (S3) to evaluate its effect on the electrical conductivity values and its interaction with colonized support material. The tests were carried out in a 32 L anaerobic inverse fluidized bed reactor (IFBR), which was inoculated with colonized support material and using two industrial electrodes at different column positions. The results with the previously digested samples (S2 and S3) were satisfactory to detect the presence of support material at the points where the electrodes were placed since the electrical conductivity values showed significant changes of up to 0.5 V, while with substrate S1 no significant voltage differences were appreciated. These results demonstrate that electrical conductivity can be used as an economic and simple mean for monitoring the support material expansion in order to avoid over expansion in the IFBR. It was also demonstrated that the conditions of the substrate in the methanogenic stage (pH and presence of volatile fatty acids) do not affect the operation of the electrical conductivity detection system.

Comparative studies on modelling and optimization of hydrodynamic parameters on inverse fluidized bed reactor using ANN-GA and RSM

Optimization of hydrodynamic parameters in counter flow inverse fluidized bed reactor (IFBR) is studied in this paper. Comparative analysis was made between artificial neural network (ANN) and response surface methodology (RSM) to evaluate the parameters. The effects of operating variables such as bed volume (300–1200 cm3), superficial liquid velocity (0.37–1.84 cm/s) and superficial gas velocity (0.07–0.59 cm/s) on percentage bed expansion, liquid holdup, gas holdup, solid holdup and average pressure drop were evaluated using three-factorial Box-Behnken design (BBD). The same was utilized to train a feed forward multilayer perceptron (MLP), ANN with back-propagation algorithm. The predicted values of the both the methodologies were compared with error functions such as root mean square error (RMSE), mean square error (MSE), mean absolute error (MAE), model predictive error % (MPE), chi-square (χ2) and correlation coefficient (R2). Optimization of operating conditions was obtained through Derringer’s desirability function (RSM) and genetic algorithm (GA), and the results were compared. It is ascertained that well trained ANN-GA has provide a high sensitive results.

A Mini Review of the Techno-environmental Sustainability of Biological Processes for the Treatment of High Organic Content Industrial Wastewater Streams

Industrial wastewater contains complex and slowly biodegradable compounds often ineffectively treated by conventional activated sludge (CAS) systems. Alternatively, advanced anaerobic technologies are implemented. The current study reviews different potential anaerobic schemes, factors influencing their final performance and optimum combinations of operational/design parameters. Anaerobic membrane bioreactors, upflow anaerobic sludge blanket reactors, expanded granular sludge beds, anaerobic hybrid reactors and inverse fluidized bed reactors are discussed. Their major advantages include: low energy requirements, energy recovery through biogas generation and high organic load removal. pH = 7, operation in a mesophilic environment and a hydraulic retention time long enough to enable anaerobic digestion in economically accepted reactor volumes are conditions that optimize the performance of anaerobic configurations. The evaluation additionally considers environmental aspects. The life cycle assessment of anaerobic industrial wastewater treatment reveals its positive environmental effect in terms of greenhouse gases emissions. Methane (a greenhouse gas) primarily contained in the biogas, despite being produced during anaerobic digestion, is utilized for energy production (heating, electricity) instead of being emitted to the atmosphere. Finally, anaerobic wastewater treatment is analyzed as part of the European Commission Innovation Deal that aims at converting conventional wastewater treatment plants to water resource recovery facilities able to combine sustainable wastewater treatment and water reuse.

A proposal of a hydrodynamic model to low Reynolds numbers in a liquid-solid inverse fluidized bed reactor

Campos-Diaz, K. E., & Alvarez-Cruz, J. L. (May-June, 2017). A proposal of a hydrodynamic model to low Reynolds numbers in a liquid-solid inverse fluidized bed reactor. Water Technology and Sciences (in Spanish), 8(3), 143-150. This paper examines the fundamental characteristics of an inverse liquid- solid inverse fluidized bed reactor. In this reactor, many experiments were performed using three sizes of polypropylene spherical solids, lighter than water, with different diameters (4.00, 4.16 and 4.18 mm) and of densities ranging from 808 to 867 kg/m3 , these were fluidized by continuous liquid phase flow. Various bed heights were obtained at different flowrates from 0.95 to 9.5 (L min-1). A predictive model is developed for the hydrodynamic behavior, such as height and solid holdups (bed porosity), this model was derived from the balance of forces acting on a single particle and the set of particles found in the fluidized bed; uses process parameters, such as reactor dimensions, particle properties, and liquid flowrates as input variables, this model also includes the inertial drag coefficient which allow extended a non-spherical particles. This model has several advantages when compared with previously reported. Among them, advantages such as standard deviation values ≤0.9% between experimental and calculated bed porosity, the bed porosity can be expressed in terms of the Reynolds and Archimedes numbers and this model estimate bed porosity in a range of Reynolds number from 5.5 to 200 which has not been studied in an inverse fluidized bed reactors.

Forecasting the effect of feast and famine conditions on biological sulphate reduction in an anaerobic inverse fluidized bed reactor using artificial neural networks

Abstract The longevity and robustness of bioreactors used for wastewater treatment is determined by the activity of the microorganisms under steady and transient loading conditions. Two identical continuously operated inverse fluidized bed bioreactors (IFB), IFB R1 and IFB R2, were tested for sulphate removal under the same operating conditions for 140 d (Periods I–IV). Later, IFB R1 was used as the control reactor (Period V), while IFB R2 was operated under feast (Period V-A) and famine (Period V-B) feeding conditions for 66 d. The sulphate removal efficiency was comparable in both IFB,

Effect of pH on the Performance of Sulfate and Thiosulfate-Fed Sulfate Reducing Inverse Fluidized Bed Reactors

AbstractSulfate-reducing bacteria (SRB)–based technologies have gained a lot of attention in the field of wastewater treatment, especially to treat metal-contaminated wastewaters. An inverse fluidized bed (IFB) bioreactor is a versatile bioreactor configuration that uses SRB technology for metal removal and recovery from wastewater. Apart from sulfate, which is commonly used as an electron acceptor, thiosulfate is another potential candidate for this process. In this study, the performance of two IFB bioreactors that were operated at pH 7.0 (R1) and 5.0 (R2) using sulfate and thiosulfate as the electron acceptors were evaluated. The electron donor used in this study was ethanol and the chemical oxygen demand (COD) to electron acceptor ratio (SO42− or S2O32−) was kept constant at 1.0. By using sulfate as the electron acceptor, the average COD removal efficiency was 75.0 and 58.0% at pH 7.0 and 5.0, respectively, while the sulfate removal efficiency was 74.4 and 50.4%, respectively. The average sulfide prod...

Effect of process variables on the sulfate reduction process in bioreactors treating metal-containing wastewaters: factorial design and response surface analyses.

The individual and combined effect of the pH, chemical oxygen demand (COD) and SO4 (2-) concentration, metal to sulfide (M/S(2-)) ratio and hydraulic retention time (HRT) on the biological sulfate reduction (SR) process was evaluated in an inverse fluidized bed reactor by factorial design analysis (FDA) and response surface analysis (RSA). The regression-based model of the FDA described the experimental results well and revealed that the most significant variable affecting the process was the pH. The combined effect of the pH and HRT was barely observable, while the pH and COD concentration positive effect (up to 7 and 3gCOD/L, respectively) enhanced the SR process. Contrary, the individual COD concentration effect only enhanced the COD removal efficiency, suggesting changes in the microbial pathway. The RSA showed that the M/S(2-) ratio determined whether the inhibition mechanism to the SR process was due to the presence of free metals or precipitated metal sulfides.

Effect of hydraulic retention time on metal precipitation in sulfate reducing inverse fluidized bed reactors

BACKGROUND Metal sulfide recovery in sulfate reducing bioreactors is a challenge due to the formation of small precipitates with poor settling properties. The size of the metal sulfide precipitates with the change in operational parameters such as pH, sulfide concentration and reactor configuration has been previously studied. The effect of the hydraulic retention time (HRT) on the metal precipitate characteristics such as particle size for settling has not yet been addressed. RESULTS The change in size of the metal (Cu, Zn, Pb and Cd) sulfide precipitates as a function of the HRT was studied in two sulfate reducing inversed fluidized bed (IFB) reactors operating at different chemical oxygen demand concentrations to produce high and low sulfide concentrations. The decrease of the HRT from 24 to 9 h in both IFB reactors affected the contact time of the precipitates formed, thus making differences in aggregation and particle growth regardless of the differences in sulfide concentration. Further HRT decrease to 4.5 h affected the sulfate reducing activity for sulfide production and hence, the supersaturation level and solid phase speciation. Metal sulfide precipitates affected the sulfate reducing activity and community in the biofilm, probably because of the stronger local supersaturation causing metal sulfides accumulation in the biofilm. CONCLUSIONS This study shows that the HRT is an important factor determining the size and thus the settling rate of the metal sulfides formed in bioreactors. © 2013 Society of Chemical Industry

Biological sulfate removal from construction and demolition debris leachate: Effect of bioreactor configuration

Due to the contamination of construction and demolition debris (CDD) by gypsum drywall, especially, its sand fraction (CDD sand, CDDS), the sulfate content in CDDS exceeds the posed limit of the maximum amount of sulfate present in building sand (1.73g sulfate per kg of sand for the Netherlands). Therefore, the CDDS cannot be reused for construction. The CDDS has to be washed in order to remove most of the impurities and to obtain the right sulfate content, thus generating a leachate, containing high sulfate and calcium concentrations. This study aimed at developing a biological sulfate reduction system for CDDS leachate treatment and compared three different reactor configurations for the sulfate reduction step: the upflow anaerobic sludge blanket (UASB) reactor, inverse fluidized bed (IFB) reactor and gas lift anaerobic membrane bioreactor (GL-AnMBR). This investigation demonstrated that all three systems can be applied for the treatment of CDDS leachate. The highest sulfate removal efficiency of 75–85% was achieved at a hydraulic retention time (HRT) of 15.5h. A high calcium concentration up to 1000mgL−1 did not give any adverse effect on the sulfate removal efficiency of the IFB and GL-AnMBR systems.