Jet Loop Bioreactor Research Articles

Dead-end filtration of jet loop bioreactor and activated sludge suspensions

Fouling is the main disadvantage of membrane processes which causes decrease in flux with time. Although there are various mathematical models representing fouling with time, a simplified approach is still needed for predicting flux decline behavior over the course of filtration. Furthermore, a comparative study to determine the effects of floc size and extracellular polymeric substance (EPS)/soluble microbial product (SMP) content for different biological suspension is important in understanding of membrane fouling. The objective of this study was to analyze filtration of two different biological suspensions and to use a simplified model to identify the effects of SMP, EPS, and floc size on fouling. The experimental data were successfully represented by a simplified model with a single fitting parameter. The fouling was independent from membrane material and pore size; however, it depended on either floc size or the EPSp content depending on the properties of biological suspension. When the floc size of the biological suspension was small (e.g. jet loop membrane bioreactor), neither EPS nor SMP contributed fouling significantly. The fouling was mainly dominated by the small floc size. However, for biological suspension with larger floc sizes (e.g. activated sludge system), the fouling was independent from floc size. For such sludge samples, the fouling was well correlated with EPSp.

Biological NOx removal by denitrification process in a jet-loop bioreactor: system performance and model development

Nitrogen monoxide (NO) and nitrogen dioxide referred as NOx are one of the most important air pollutants in the atmosphere. Biological NOx removal technologies have been developing to reach a cost-effective control method for upcoming stringent NOx emission standards. The BioDeNOx system was seen as a promising biological NOx control technology which is composed of two reactors, one for absorbing of NO in an aqueous Fe(II)EDTA2− solution and the other for subsequent reduction to N2 gas in a biological reactor by the denitrification process. In this study, instead of two discrete reactors, only one jet-loop bioreactor (JLBR) was utilized as both absorption and denitrification unit and no chelate-forming chemicals were added. In other words, the advantage of better mass transfer conditions of jet bioreactor was used instead of Fe(II)EDTA2−. The process was named as Jet-BioDeNOx. The JLBR was operated for the removal of NOx from air streams containing 500–3000 ppm NOx and the results showed that the removal efficiency was between 81% and 94%. The air to liquid flow ratio (QG/QRAS) varied in the range of 0.07–0.12. Mathematical modelling of the system demonstrated that the removal efficiency strongly depends on this ratio. The high mass transfer conditions prevailed in the reactor provided a competitive advantage on removing NO gas without any requirement of chelating chemicals.

Operating and hydrodynamic characteristics of a reversed flow jet loop bioreactor (RFJLB) with ejector

The hydrodynamic characteristics of RFJLB was studied with superficial liquid velocity (Ul), nozzle diameter (Dn) and nozzle height (Hn) in the range of 0.0293–0.094m/s, 17.4–22.0mm and 50–400mm, respectively. For Dn=17.4mm, Hn=50 and 200mm, with ejector mode and regular operating procedure i.e. simultaneous entry of gas with increasing liquid velocity, had limitation of not establishing the circulation loop. To overcome this limitation a modified operating procedure i.e. entry of gas after established liquid circulation loop is proposed. Also the comparison of gas holdups with ejector and injector mode proves the effectiveness of ejector mode and can eliminate the supply of compressed gas. Thus proper choice of Dn, Hn and also the operating procedure becomes necessary.

Influence of membrane fouling reducers (MFRs) on filterability of disperse mixed liquor of Jet Loop Bioreactors

The effects of membrane fouling reducers (MFRs) (the cationic polyelectrolyte (CPE) and FeCI 3) on membrane fouling were studied in a lab-scale jet loop submerged membrane bioreactor (JL-SMBR) system. The optimum dosages of MFRs (CPE dosage = 20 mg g −1MLSS, FeCI 3 dosage = 14 mg g −1MLSS) were continuously fed to JL-SMBR system. The soluble and bound EPS concentrations as well as MLSS concentration in the mixed liquor of JL-SMBR were not changed substantially by the addition of MFRs. However, significant differences were observed in particle size and relative hydrophobicity. Filtration tests were performed by using different membrane types (polycarbonate (PC) and nitrocellulose mixed ester (ME)) and various pore sizes (0.45–0.22–0.1 μm). The steady state fluxes ( J ss ) of membranes increased at all membranes after MFRs addition to JL-SMBR. The filtration results showed that MFRs addition was an effective approach in terms of improvement in filtration performance for both membrane types.

Fouling characteristics of microfiltration membranes during the filtration of jet loop membrane bioreactor (JLMBR) activated sludge

The main objective of this study was to characterize the activated sludge of jet loop membrane bioreactor (JLMBR) in order to determine its effects on the membrane biofouling. The sludge characteristics were evaluated in terms of MLSS (mixed liquor suspended solid), EPS (extracellular polymeric substance), SMP (soluble microbial product), relative hydrophicity (RH) and viscosity. The membrane filtration tests were performed at a cross-flow microfiltration system by using cellulose acetate (CA) and cellulose nitrate (CN) filters with 0.2 and 0.45 μm of pore sizes. The jet loop bioreactor was operated at a batch mode for 36 d with an organic load of 3 kg COD m-3d -1. The COD treatment efficiency was achieved at 95%. It was found that the sludge properties changed with MLSS concentration. The viscosity of sludge increased and the RH of sludge decreased with increase in MLSS concentration. The EPS concentration of the sludge was much higher than SMP concentration. The carbohydrate contents of EPS and SMP were higher than the protein contents. The flux decline models and the resistance analysis were used to investigate the biofouling mechanism. In the resistance analysis, it was found that the pore blocking resistance (R p ) of CA membrane with pore size of 0.45 μm (CA045) was higher than the cake layer resistance (R c ), (3.56 and 1.02 × 1012 m-1). R c was more higher than R p for the other membranes. R p of membranes were found to be 33.6%, 77.1%, 23.4% and 21.9% of the total resistances (R t ) for CA02, CA045, CN02 and CN045, respectively. It was concluded that the high EPS content in JLMBR was the main fouling parameter for membranes. It was also found that the affinity of membrane types against EPS varied.

Flow regimes in a two phase reversed flow jet loop bioreactor

Reversed flow jet loop bioreactors (RFJLB) have been used extensively for 2 or 3 phase biochemical reactions. From visual observations and gas holdup data, 3 distinct flow regimes are identified in RFJLB, namely: (1) Bubble free regime (BFR), where bubbles are observed in the draft tube only; (2) Transition regime (TR), where bubbles are observed in both the draft tube and the annulus, but without circulation; and (3) Complete bubble circulation regime (CBCR), where bubbles circulate in both the draft tube and annulus. CBCR is the most desirable regime, since the reactor operation in this regime gives a higher gas holdup and mass transfer rate than in the other two regimes. In the present study, the hydrodynamic behavior of RFJLB was investigated under various operational and geometrical conditions, such as gas and liquid velocity and nozzle configuration. Factors affecting the critical liquid circulation velocity (CLCV) above which the CBCR is established were identified and evaluated quantitatively.

Phenol biodegradation in a batch jet loop bioreactor (JLB): Kinetics study and pH variation

Phenol biodegradation in a batch jet loop bioreactor (JLB) using activated sludge was investigated. The biodegradation experiments were conducted at different phenol concentrations ( S 0) from 50 to 1000 mg/l. The results of the biodegradation of phenol by JLB show that a good phenol removal of 100%. The biodegradation capacity of the JLB was higher than that of the stirred tank reactor reported in literatures. The Haldane equation was adopted in order to describe the relation between the specific growth rates ( μ) and S 0. Kinetic constants of Haldane equation were μ m = 0.119 1/h, K s = 11.13 mg/l and K i = 250.88 mg/l. Model equations were simulated using the MATHCAD 7.0 software’s ordinary differential equation solver. Simulations were performed at each experiment with different initial phenol concentrations.

Respirometric kinetic parameter calculations of a batch jet loop bioreactor treating leachate and oxygen uptake rate estimation by DTM

A novel circulating jet loop bioreactor adapted for organic matter oxidation has been designed and constructed. In this study, the input was leachate samples collected from Kemerburgaz Odayeri waste landfill site located on the European side of Istanbul. Controlling the jet loop bioreactor to realize high rates of purification depends on maintaining the appropriate loadings and operating conditions. This requires collecting various system data to estimate the dynamics of the system satisfactorily with the aim of keeping certain parameters within the specified range. The differential transform method (DTM) based solution of the state equations reveals the current state of the process so that any deviation in the system parameters can be immediately detected and regulated accordingly. The respirometric method for kinetic parameter calculations for biodegradation has been used for some time. In many studies, the respirometer was designed separately, usually in bench-scale. However, when a separate respirometer is used, the scale effect and parameters that affect the hydrodynamic structure of the system should be taken into consideration. In this study, therefore, the jet loop reactor itself was used as a respirometer. Thus, the kinetic parameters found reflecting the characteristics of microorganisms used for biodegradation would be more realistic. If the main reactor, here the jet loop reactor, would be used as the respirometer, the kinetic parameter changes can easily be monitored in the long run. Using the bioreactor as a respirometer, the most important kinetic parameters, K s, k d and μ max were found to be 11,000 mg L −1, 0.019 day −1, and 0.21 day −1, respectively. The stoichiometric coefficient, Y, was found to be 0.28 gr gr −1 for the present system.

Influence of draft tube cross-sectional geometry on KLa and ɛ in jet loop bioreactors (JLB)

Due to their compactness, and high flexibility in operation, the new processes like jet loop bioreactors (JLB) show a large potential for high removal efficiency and significant cost reduction in particular for the biological treatment of highly polluted wastewater. The rate of oxygen delivery determines the efficiency of aerobic processes. A modified JLB with square cross-sectional draft tube was developed in this study. Experiments were performed to investigate the effects of cross-sectional geometry, liquid flow rate and gas flow rate on gas hold-up and KLa. The comparison of these parameters as well as KLa was carried out for two cross-sectional draft tubes geometry. The results indicated that KLa values were better by 11–13% in square draft tube. In this study, the mass transfer characteristics with the square draft tube configuration have also been studied and a model was developed for this configuration.

Simultaneous removal of C, N, P from cheese whey by jet loop membrane bioreactor (JLMBR)

The membrane bioreactor (MBR) used in this study consisted of a jet loop bioreactor (aerobic high rate system) and a membrane separation unit (microfiltration). Jet loop membrane bioreactor (JLMBR) system is a high performance treatment system. High organic loading rates can be achieved with a very small footprint. The JLMBR is a compact biological treatment system which requires much smaller tank volumes than conventional activated sludge system. Solid–liquid separation is performed with a membrane. The JLMBR system, of 35 L capacity, was operated continuously for 3 months with a sludge age of 1.1–2.8 days and chemical oxygen demand (COD) loads of 3.5–33.5 kg COD m −3 day −1. The mean concentration values of COD, total nitrogen (TN) and PO 4 3− in cheese whey (CW) were found as 78,680 mg L −1, 1125 mg L −1 and 378 mg L −1, respectively. Ninety-seven percent COD removal rate was obtained at the sludge age ( Θ c) of 1.6 days and volumetric loads of 22.2 kg COD m −3 day −1. TN removal was obtained as 99% at the loading rates of 17–436 g TN m −3 day −1. PO 4 3− removals were between 65 and 88% for the loading of 30–134 g PO 4 3− m −3 day −1. The system could simultaneously remove the COD, TN and PO 4 3− at high efficiencies. The sludge flocks were highly motile, dispersed and had poor settling properties.

Sludge characteristics and effect of crossflow membrane filtration on membrane fouling in a jet loop membrane bioreactor (JLMBR)

An aerobic jet loop membrane bioreactor (JLMBR) activated sludge process of 35 L working volume was used to investigate its applicability in industrial wastewaters, specifically cheese whey wastewater. A loading rate of 22.2 kg COD/(m 3 day) and 1.6 days of sludge age was achieved with 97% COD removal efficiency. During the study, the activated sludge was found non-settable and slimy characteristic and non-flocculating motile bacteria structure. Therefore, it was been conducted that the membrane separation was indispensable to obtain high performance from jet loop bioreactor (JLB). From the investigation of crossflow microfiltration characteristic of the system, it was found that the fluxes decreased and MFI increased with increasing MLSS concentration. The increasing crossflow velocity greatly reduced the cake formation on the membrane surface and increased the steady state permeate fluxes, decreasing specific cake resistance ( α) values. The cake layer was in a highly compressible form. The compressibility coefficient was calculated as 0.98. In addition to this, the pseudo gel concentration ( C G) on the membrane surface was calculated to be 73,130 mg/L. For the investigation of the membrane filtration mechanism, it was found that the fouling mechanism showed high compatibility with complete pore blocking model and particularly cake filtration model ( R 2 = 0.99).

Gas holdup, foaming and oxygen transfer in a jet loop bioreactor with artificial foaming media and yeast culture

A concentric draft tube jet loop bioreactor (10.5 m 3) was used to study the influence of aerated liquid height (above the draft tube) on the amount of surfactant addition allowable without foaming. Sodium lauryl sulfate (SLS) and defatted soybean flour in tap water were used as model artificial media. The amount of surfactant required to develop foaming and the maximum gas holdup achieved prior to foaming were notably influenced by aerated liquid height. Decreasing the aerated liquid height from 1.50 to 0.05 m increased the amount of SLS allowed without foaming from 2.2 to 12.1 g, the gas holdup in the riser from 0.18 to 0.31 and the gas holdup in the downcomer from 0.12 to 0.25. Similar behavior was observed for soybean flour. Decreasing the aerated liquid height from 1.45 to 0.05 m increased the amount of soybean flour allowed without foaming from 822 to 3200 g, the gas holdup in the riser from 0.17 to 0.26 and the gas holdup in the downcomer from 0.10 to 0.19. Data from a representative continuous yeast culture are reported to show that operation at low aerated liquid heights (0.5 m) can also be used to produce a culture broth with large gas holdup and oxygen transfer but without foaming.

Application of down flow jet loop bioreactors in implementation and kinetic determination of solid–liquid enzyme reactions

Glucose isomerization to fructose by immobilized glucose isomerase as an example of solid–liquid enzyme reaction has been studied in a down flow jet loop reactor (DJR). Conversion of glucose to fructose has been measured and compared with that formed in a batch reactor. The performance capability of the DJR was observed to be higher than that of the conventional reactors. The optimum operating conditions of the reaction system have been also determined using the Taguchi experimental design method. The effects of enzyme loading, draft tube diameter, position of nozzle inside the draft tube, and gas and liquid flow rates on glucose conversion have been considered. Analysis of the results revealed that the draft tube diameter has the highest and the ratio of liquid circulation rate to the gas flow rate has the least effects on the conversion of glucose. It was found that the experimental data could be correlated favoarably with a modified structure of the Michalis–Menten model consisting of two transition complexes.

High strength wastewater treatment in a jet loop membrane bioreactor: kinetics and performance evaluation

Treatment of wastewater containing high organic matter was investigated by means of a jet loop bioreactor combined with a membrane process. Volume of jet loop bioreactor and area of membrane filtration unit were 23 l and 155 cm 2 respectively. It was found that jet loop reactor had high mass transfer coefficient ( K L a ) varying from 58.8 to 486 h - 1 depending on the water flow rate (i.e. power input) and air flow rate. Oxygen transfer efficiency and oxygenation capacity of the reactor varied from 12 to 22.5% and from 0.2 to 1.8 kg O 2 kW - 1 , respectively. The efficiency of jet loop membrane bioreactor was found to be approximately 97% for a volumetric organic load of 2– 97 kg COD / m 3 day over a period of 10 weeks. The reactor was not disturbed from the organic loads up to 68 kg COD / m 3 day , but the treatment efficiency decreased to about 60% at higher organic loads. This decrease was due to insufficient oxygen transfer rate. The relationship between the effluent substrate concentration and the specific oxygen uptake rate (SOUR) values was determined. Applied food/microorganism ( F/M) ratio was varied between 2.5 and 17 day - 1 . Critical sludge age of the system ( Θ c m ) was evaluated to be 7.2 h. Sludge with unsatisfactory settling characteristics formed at high F/M values under turbulent conditions. Therefore, membrane process was used for solid–liquid separation and effluent solid concentration was approximately zero. Specific cake resistances ( α ) changed with F/M ratio. It was found that permeate fluxes were significantly effected with F/M ratio much more than mixed liquor suspended solids (MLSS). Average flux was 2.50 m 3 / m 2 day for 0.2 μ m pore sized cellulose acetate membrane. It was concluded that the jet loop membrane bioreactor has distinctive advantages such as the ability to treat high strength wastewater, low area requirements and easy operation.

Microbial characterisation of activated sludge in jet-loop bioreactors treating winery wastewaters.

Jet-loop reactors (JLR) used as biological waste treatment processes introduce an additional selective pressure on the natural microbial flora of the incoming effluent. Several high-performing microbial inocula were tested for winery wastewater treatment and the microbial composition was analysed. A microbial consortium was enriched and selected for use with a new type of aerobic JLR. The reactor was operated continuously for more than 1 year using winery wastewaters collected in different seasons. Chemical oxygen demand (COD) removal efficiency was on average greater than 80%, with retention times of 0.8-1 day. Microbial populations were sampled for characterisation after 6 months and at the end of the study. Isolates were identified at genus and/or species level. Almost all isolates belonged to the genera Pseudomonas and Bacillus. Saccharomyces cerevisiae was also found but no filamentous fungi. These results show that a highly adapted population develops in JLRs treating winery effluents as compared to other bioreactors. Aerobic JLRs impose a stringent selective criterion on the composition of the microbial biomass.

Hydrodynamic and mass transfer characterization of a down flow jet loop bioreactor

The effects of certain pertinent parameters such as gas and liquid flow rates and nozzle position on the behavior of a down flow jet loop bioreactor (DJB) have been studied. The mean residence times of gas and liquid phases and the gas hold-up within the bioreactor have been measured. A correlation has been presented for the gas hold-up. In addition, the overall volumetric mass transfer coefficient, and the influence of the gas flow rate and the position of the nozzle inside the draft tube on the latter has been determined and a correlation has been derived. The liquid residence time distribution (RTD) within the bioreactor has been studied by tracer analysis and the mixing time was calculated using the RTD results.

Local overall volumetric gas–liquid mass transfer coefficients in gas–liquid–solid reversed flow jet loop bioreactor with a non-Newtonian fluid

The local overall volumetric gas–liquid mass transfer coefficients at the specified point in a gas–liquid–solid three-phase reversed flow jet loop bioreactor (JLB) with a non-Newtonian fluid was experimentally investigated by a transient gassing-in method. The effects of liquid jet flow rate, gas jet flow rate, particle density, particle diameter, solids loading, nozzle diameter and CMC concentration on the local overall volumetric gas–liquid mass transfer coefficient ( K L a) profiles were discussed. It was observed that local overall K L a profiles in the three-phase reversed flow JLB with non-Newtonian fluid increased with the increase of gas jet flow rate, liquid jet flow rate, particle density and particle diameter, but decreased with the increase of the nozzle diameter and CMC concentration. The presence of solids at a low concentration increased the local overall K L a profiles, and the optimum of solids loading for a maximum profile of the local overall K L a was found to be 0.18×10 −3 m 3 corresponding to a solids volume fraction, ε S=2.8%.

Influence of operating variables on liquid circulation in a 10.5‐m3 jet loop bioreactor

A 10.5-m(3) concentric tube jet loop reactor was used to study the influence of the working liquid volume, mean superficial air velocity, operating pressure, downcomer aeration, liquid jet velocity, and two ratios of draft tube/reactor diameter (D(t)/D) on liquid circulation time (T(c)). The experiments were carried out in a water-air system with the use of the acid pulse method. Results showed that circulation time was independent of the working liquid volume over a certain minimum liquid level, whereas downcomer aeration and D(t)/D ratio appeared as amenable parameters to achieve a high degree of control over liquid circulation and mixing efficiency, and to optimize the overall reactor performance. Increasing the operating pressure caused a reduction of the liquid circulation rate. However, ionger residence times of the air bubbles and the higher mass transfer driving force that result at higher pressures improve oxygen utilization. The relationship between T(c) and air load was independent of the operating pressure, provided the correlation is given as a function of the mean superficial air velocity. Neither liquid circulation nor gas holdup were significantly affected by liquid jet velocity. (c) 1995 John Wiley & Sons, Inc.

Overall volumetric mass transfer coefficient in a modified reversed flow jet loop bioreactor with low density particles

Experiments were conducted using glass beads and low-density particles such as polyurethane and polystyrene which are comparable to bioparticles found in biological applications to evaluate the overall volumetric mass transfer coefficient (KLa) in a modified reversed flow jet loop bioreactor having the liquid outlet at the top section of the reactor. The influence of the gas and liquid flow rates, draft tube to reactor diameter ratio, solids loading and physical properties of solids onKLa were studied. TheKLa was found to increase with the increased gas and liquid flow rates. TheKLa values were found to be higher in the bubbly flow region i.e., at the lower range of energy dissipation rates. The optimum draft tube to reactor diameter ratio and solids loading with respect to maximumKLa were found to be 0.4 and 0.9×10−3 m3 (ɛs=0.025) respectively. Dimensionless correlations were presented to predict the experimental values in terms of operational and geometrical variables.

Mixing time in a down-flow jet loop bioreactor

Mixing time was determined in a down-flow jet loop bioreactor with Newtonian and non-Newtonian fluids. It was observed that the mixing time decreased with an increase in linear liquid velocity, superficial gas velocity, draft tube to column diameter ratio, nozzle diameter and shear thinning of media. The optimum draft tube to column diameter ratio was found to be about 0.44. Correlations were presented for prediction of mixing time.