Loop Airlift Bioreactor Research Articles

Treatment of the refinery wastewater in a gas–liquid–solid three‐phase flow airlift loop bioreactor

AbstractAerobic treatment of refinery wastewater was carried out in a 200 dm3 gas–liquid–solid three‐phase flow airlift loop bioreactor, in which a biological membrane replaced the activated sludge. The influences of temperature, pH, gas–liquid ratio and hydraulic residence time on the reductions in chemical oxygen demand (COD) and NH4‐N were investigated and discussed. The optimum operation conditions were obtained as temperature of 25–35 °C, pH value of 7.0–8.0, gas–liquid ratio of 50 and hydraulic residence time of 4 h. The radial and axial positions had little influence on the local profiles of COD and NH4‐N. Under the optimum operating conditions, the effluent COD and NH4‐N were less than 100 mg dm−3 and 15 mg dm−3 respectively for more than 40 days, satisfying the national primary discharge standard of China (GB 8978‐1996). Copyright © 2005 Society of Chemical Industry

Characteristics of three-phase internal loop airlift bioreactors with complete gas recirculation for non-Newtonian fluids

Hydrodynamic and gas-liquid mass transfer characteristics, such as liquid velocity, gas holdup, solid holdup and gas-liquid volumetric mass transfer coefficient, in the riser and downcomer of the gas-liquid-solid three-phase internal loop airlift bioreactors with complete gas recirculation for non-Newtonian fluids, were investigated. A mathematical model for the description of flow behavior and gas-liquid mass transfer of these bioreactors was developed. The predicted results of this model agreed well with the experimental data.

Removal of ethyl acetate in air streams using a gas–liquid–solid three-phase flow airlift loop bioreactor

The biological removal of ethyl acetate in air streams was carried out in gas–liquid–solid three-phase flow airlift loop bioreactor, in which biological membrane replaced the activated sludge. The influences of temperature, pH and waste gas influx on the removal efficiency (RE) and the outlet concentration of ethyl acetate were investigated and discussed. The optimum operation conditions were obtained as the temperature of 20–30 °C, pH 6.5–7.5 and waste gas influx of 0.05 m 3/h. Under the optimum operation conditions, the average removal efficiency of ethyl acetate is higher than 98%, corresponding to the outlet concentration of ethyl acetate lower than 150 mg/m 3. The maximum elimination capacity (EC) of ethyl acetate in gas–liquid–solid three-phase flow airlift loop bioreactor was higher than that in the biofilters reported in the literature.

Improved production of phenylethanoid glycosides by Cistanche deserticola cells cultured in an internal loop airlift bioreactor with sifter riser

An internal loop airlift bioreactor with sifter riser (ILABSR) was composed of a bubble column and a draught-tube rolled with 40-mesh sifter that placed 5 cm above the bottom at the center of the column. A 2 L ILABSR was used for the suspension cultivation of Cistanche deserticola cells and its performance was compared with shake flask culture and a bubble column. Under the optimum culture conditions with the air flowrate of 0.075 m 3/h and the inoculation size of 4.7%, about one-fifth cells were attached to the sifter draught-tube. PeG content in these cells was 16.3%, which was 104% higher than that of suspension cells. The production of phenylethanoid glycosides reached 0.85 g/L, which was 102 and 4% higher than those cultured in a 2 L bubble column and shake flasks respectively under their optimal culture conditions.

Simultaneous removal of ethyl acetate and ethanol in air streams using a gas–liquid–solid three-phase flow airlift loop bioreactor

Abstract A gas–liquid–solid three-phase flow airlift loop bioreactor was applied to treat air streams containing a mixture of ethyl acetate and ethanol. The activated sludge was replaced by biological membrane in the experiment. The influences of pH and jet waste gas influx on the removal efficiency and outlet ethyl acetate and ethanol mixture concentration were investigated. The optimum pH and jet waste gas influx were 6.0 and 4.4 m/s, respectively. Under the optimum operation conditions, the average removal efficiencies of ethyl acetate and ethanol in the mixture were higher than 98%, and accordingly, the outlet concentrations of ethyl acetate and ethanol were lower than 150 mg/m3. The elimination capacities of ethyl acetate (504 g/m3/h) or ethanol (685 g/m3/h) in the mixture as two mixture pollutants, which were higher than those in biofilters (ethyl acetate 400 g/m3/h and ethanol 195 g/m3/h) reported in the literatures [Y.H. Liu, X. Quan, Y.M. Sun, J.W. Chen, D.M. Xue, J.S. Chung, Simultaneous removal of ethyl acetate and toluene in air stream using compost-bases biofilters, J. Hazard. Mater. B 95 (2002) 199–213; D. Arulneyam, T. Swaminathan, Biodegradation of ethanol vapour in a biofilter, Bioprocess Eng. 22 (2000) 63–67], were also higher than those of pure ethyl acetate (480 g/m3/h) or ethanol (671 g/m3/h) as single pollutant in gas–liquid–solid three-phase flow airlift loop bioreactor.

Enhanced Oxygen Mass Transfer in an External Loop Airlift Bioreactor Using a Packed Bed

A small quantity of nylon mesh packing inserted in the riser section of an external loop airlift bioreactor (ELAB) was found to increase the overall volumetric oxygen mass transfer coefficient by a factor of 3.73 compared to an unpacked riser. The packing increased gas holdup, decreased bubble size, and decreased liquid circulation rates in the bioreactor, all of which contributed to the dramatic improvement in oxygen mass transfer. A dynamic, spatial model was developed to predict the mass transfer behavior between air bubbles and the continuous liquid phase in the ELAB with and without a packed bed. The model demonstrated superior accuracy compared to simulating the ELAB as a well-mixed vessel and also correctly predicted the cyclical behavior in liquid oxygen concentrations. The oxygen mass transfer coefficient was determined as a best fitting parameter of the model and was found to increase to 4.2 × 10-3 s-1 using a small amount of packing (96.3% porosity) compared to the unpacked ELAB. This is similar to values measured in well-mixed bioreactors operating at the same aeration rates. The ELAB containing a packed bed is a novel bioreactor with much higher mass transfer and increased surface area for cell immobilization, and therefore it has potential to greatly enhance gas−liquid fermentations and other gas−liquid biochemical operations.

Modeling and scale up of airlift bioreactor

A previously presented mathematical model based on a tanks-in-series model with back flow for an airlift bioreactor is extended by considering the variations of the oxygen in the gas phase and the hydrostatic pressure along the bioreactor. The kinetic model used considers the effect of two substrates (glucose and dissolved oxygen) on the growth rate. A set of first order differential equations for the material balances of the micro-organism, glucose, product, dissolved oxygen, and oxygen in the gas phase around the hypothetical well mixed stages in the riser and the downcomer were solved simultaneously using Athena software package. The model has been validated with experimental data of gluconic acid fermentation in two different scales of internal loop airlift bioreactor, 10.5 dm 3 and 35 dm 3. The scale up effects on the performance, kinetic parameters and model predictions of gluconic acid fermentation in airlift bioreactors were studied. The model is simple enough to be used in design and scale up studies and it can be adapted to other airlift system configurations and fermentation systems other than gluconic acid fermentation.

Deactivation kinetics of immobilized glucose oxidase for production of calcium gluconate in an external loop airlift bioreactor

In our previous works, the immobilized glucose oxidase (GO) plus manganese dioxide (MnO 2) were prepared and efficiently used at 30 °C for production of calcium gluconate (CaG) in an external loop airlift. In the gel beads occurred the three reactions: (1) the GO-catalyzed air oxidation of glucose to produce gluconic acid (GA) and hydrogen peroxide (P) which inactivated GO, (2) the MnO 2-catalyzed decomposition of P and (3) the neutralization of GA with calcium hydroxide added continuously resulting in accumulation of CaG at a constant pH. In this work, the stabilities of the immobilized GO and MnO 2 activities to various operating conditions are observed and analyzed to develop an efficient prolonged use of GO plus MnO 2 entrapped. The well-known first-order kinetics is assumed to analyze the deactivation of either GO or MnO 2 since its stability is affected by a complicated interaction among the operating variables. The first-order deactivation rate constant for GO, k d,E is determined from the progressive decrease in the apparent effectiveness factor for GO, α app based on the initial GO concentration C E,0 in the gel beads. This is because the decrease in the GO concentration, C E is too difficult to measure but approximately directly proportional to α app. The k d,E value under any set of operating conditions is determined from the two values of α app at the start and end of the 24 h reaction. To obtain the k d,E values for the prolonged times, the repeated 24 h reactions are carried out with the same gel beads. Examining the data on k d,E obtained under the various operating conditions gives an empirical correlation of k d,E with the pH value and the P concentration C P which is the time-averaged P concentration during every 24 h reaction. The other variables such as the glucose and gel beads concentrations and the superficial air velocity are found to exert almost no influence on the k d,E value. On the other hand, the deactivation rate constant for MnO 2, k d,M is determined from the two values of the intrinsic P decomposition rate constant, k P in the same 24 h reaction as above since the k P value, which is proportional to the MnO 2 concentration C M, can be calculated from its apparent value based on the effectiveness factor theory. The k d,M values are empirically correlated with the pH value only. The above two deactivation kinetic models are combined with our previous reaction and mass transfer model for the gel beads in the airlift to simulate the CaG production process in a prolonged batch bioreactor operation. A fair agreement obtained between the observed and calculated time courses of the process suggests the validity of the deactivation models developed. An application of the simulation model also predicts an optimal ratio of the amounts of GO and MnO 2 immobilized in the gel beads.

Modeling and simulation of airlift bioreactors

A tanks-in-series model was applied for mathematical modeling of the unsteady state performance of a semi batch operation in a 10.5 dm 3 internal loop airlift bioreactor for the production of gluconic acid by fermentation. A set of first order differential equations for the material balances of micro-organism, substrate, product, and dissolved oxygen around the hypothetical well mixed stages in the riser and the downcomer was solved simultaneously using the Athena software package. The kinetic model used considers the effect of two substrates (glucose and dissolved oxygen) on the growth rate. Both the effect of airflow rate and the height of the airlift bioreactor on the gluconic acid production were investigated. The model has been validated with experimental data. The model is simple enough to be used in design studies and it can be adapted to airlift system configurations and fermentation systems other than gluconic acid fermentation.

Analysis of the hydrodynamic parameters of external loop air lift bioreactors

In this study we analyzed the effects of the hydrodynamic conditions and properties of the working fluid on the operation of external loop air lift bioreactors. In particular, the effects of design and operating parameters (e.g. reactor geometry, design of the gas sparger, superficial gas velocity, flow regime) as well as the fluid properties (liquid viscosity and addition of surfactants) on the liquid superficial velocity and gas hold-up were defined. Several correlations found in the literature based on theoretical models of fluid flow, as well as several semi-empirical and empirical correlations were tested and the applicability of all the proposed correlations was verified on the available experimental data. The most accurate correlations for the prediction of the gas hold up, liquid circulation velocity and slip velocity in each bioreactor operating regime were identified.

Nitrifying Treatment of Wastewater from Fertilizer Production in a Three‐Phase Flow Airlift Loop Bioreactor

AbstractA 12‐L gas‐liquid‐solid three‐phase flow airlift loop bioreactor, in which biological membranes replace the activated sludge, was used in the nitrifying treatment of a real effluent in a Nanjing chemical fertilizer plant. The influences of temperature, pH, air flow rate and HRT on ammonia nitrogen reduction were investigated and discussed. The optimum operating conditions, such as temperature of 30–35 °C, pH value of 7–8, air influx of 0.3 m3/h, and hydraulic residence time (HRT) of 8 hours, were found. Under optimum operating conditions, the average removal efficiencies of COD and NH4‐N are higher than 95 % and 99 %, corresponding to the effluent COD < 50 mg/L and NH4‐N < 5 mg/L, which is far below the primary discharge standard for the chemical fertilizer industry of P.R. China – COD < 150 mg/L and NH4‐N < 60 mg/L (GWPB4–1999). In addition, the radial and axial positions have little influence on the local profiles of COD and NH4‐N.

Nitrifying Treatment of Wastewater from Fertilizer Production in a Three‐Phase Flow Airlift Loop Bioreactor

A 12-L gas-liquid-solid three-phase flow airlift loop bioreactor, in which biological membranes replace the activated sludge, was used in the nitrifying treatment of a real effluent in a Nanjing chemical fertilizer plant. The influences of temperature, pH, air flow rate and HRTon ammonia nitrogen reduction were investigated and discussed. The optimum operating conditions, such as temperature of 30-35 °C, pH value of 7-8, air influx of 0.3 m 3 /h, and hydraulic residence time (HRT) of 8 hours, were found. Under optimum operating conditions, the average removal efficiencies of COD and NH 4 -N are higher than 95 % and 99 %, corresponding to the effluent COD < 50 mg/L and NH 4 -N < 5 mg/L, which is far below the primary discharge standard for the chemical fertilizer industry of P.R. China - COD < 150 mg/L and NH 4 -N < 60 mg/L (GWPB4-1999). In addition, the radial and axial positions have little influence on the local profiles of COD and NH 4 -N.

Bioremediation of toluene‐contaminated air using an external loop airlift bioreactor

AbstractAn external loop airlift bioreactor (ELAB) has been used to capture and degrade toluene from a contaminated air stream. Using a spinning sparger, the toluene could be transferred from small, uniform bubbles into the aqueous culture media with an overall mass transfer coefficient as high as 1.1 h−1. Due to the very volatile nature of toluene, Pseudomonas putida (ATCC 23973) was cultured and maintained on benzyl alcohol, the first intermediate compound in the metabolic degradation pathway for toluene. Consequently, before successful continuous operation of the ELAB with toluene‐contaminated air, Pseudomonas putida was acclimatized to toluene by using 30 min intermittent sparging of contaminated air into the bioreactor. Continuous sparging of toluene‐contaminated air could then be successfully carried out with 100% capture and biodegradation efficiency at a contaminated air concentration of 15 mg dm−3 and a loading rate of 35 mg dm−3 h−1. Higher concentrations and loading rates were only partially degraded. Although this capture matches only the low rates reported earlier using biofilters to remediate toluene, the ELAB operates using submerged culture and requires no packing which can plug during biofilter operation. In this study, Pseudomonas putida grew on toluene at a maximum specific growth rate of only 0.05 h−1.© 2003 Society of Chemical Industry

The denitrification of nitrate contained wastewater in a gas–liquid–solid three-phase flow airlift loop bioreactor

Denitrification of nitrified effluent with high concentration of nitrate, low COD in fertilizer plant was carried out in a 12-l gas–liquid–solid three-phase flow airlift loop bioreactor, in which biological membrane replace the activated sludge. The influences of pH, temperature, C/N ratio, gas–liquid ratio and HRT on the removal of nitrate-nitrogen were investigated and discussed. The optimum operation conditions were obtained as pH value of 6.5–7.5, temperature of 20–35 °C, C/N ratio of 0.95–1, gas–liquid ratio of 62.5 and HRT of 2.5 h. Under optimum operation conditions, the average removal efficiencies of COD and NO x –N are higher than 93 and 96%, corresponding to the effluent concentrate of nitrate <20 mg/l and COD <40 mg/l. The radial and axial positions have little influence on the local profiles of COD and NO x –N.

Biological treatment of printing ink wastewater

Printing ink wastewater is usually very difficult to treat biologically and its chemical oxygen demand (COD) far exceeds standards of discharge. The COD in wastewater is usually 3,000 to 8,000 mg/L after flocculation and sedimentation. Herein, a strain of bacterium was isolated from the sludge and identified as Bacillus sp. and utilized to treat printing ink wastewater. The application of bacteria to degrade printing ink in wastewater is discussed in this paper. The influence of N and P sources on COD removal, and COD removal in combination with glucose was also discussed. More than 85 per cent of the COD could be removed using the proposed biological process. A novel internal airlift loop bioreactor with bacteria immobilized onto ceramic honeycomb support was used for the wastewater treatment.

Hydrodynamic Characteristics in an External Loop Airlift Bioreactor Containing a Spinning Sparger and a Packed Bed

An external loop airlift bioreactor (ELAB) and the packed bed bioreactor (PB) design strategies have been combined into one vessel. The hydrodynamic behavior of the combined system has been investi...

Modified volume expansion method for measuring gas holdup

AbstractA simple, modified volume expansion method, or inclined tube method, is compared to the pressure difference method for determining gas holdup in an airlift bioreactor. The modified volume expansion method could be used for all pneumatic bioreactors where fluid fluctuation is vigorous and visual observation of the continuous phase rise is difficult. The overall gas holdup data measured using the inclined tube method are shown to be very close to overall gas holdup determined using a gamma ray density monitor system. However, the overall gas holdup measured by the pressure difference method is found to be significantly different. This difference is due to energy dissipation in the External Loop Airlift Bioreactor (ELAB) used in this study, which causes the pressure difference method to be incorrect.

An internal airlift loop bioreactor with Burkholderia pickttii immobilized onto ceramic honeycomb support for degradation of quinoline

A novel kind of bioreactor with a ceramic honeycomb support installed in a draught tube was developed and the ceramic honeycomb support could be used for immobilization of microbial cells. A strain of bacterium was isolated from activated sludge and identified as Burkholderia pickttii for degradation of quinoline and could grow on quinoline which served as a sole source of carbon, nitrogen and energy. Quinoline was degraded by the bioreactor in both batch and continuous flow operations when they were immobilized onto the ceramic honeycomb support. Experimental results indicated that quinoline could be degraded effectively by B. pickttii immobilized onto the ceramic support. Immobilized B. pickttii exhibited better stability in its metabolism and proliferation and degradation of quinoline in continuous flow operation conditions. More than 95% of quinoline could be removed for 4 h of hydraulic retention time (HRT). Quinoline was degraded through 2-hydroxy quinoline according to the analysis of gas chromatography–mass spectrum (GC–MS).

Bio-oxidation of minerals in air-lift loop bioreactors

The high rate bio-oxidation of minerals in tanks has received a great deal of interest over the last decades. So far, aerated stirred tank reactors, which are common in the mining industry, have been used for these processes. However, as we are dealing with a biological system, it makes sense to apply reactor types that are especially designed for biotechnological applications. PAQUES has extensive experience with high rate biotechnology in reactors. The Circox® air-lift loop reactor was especially designed for biological processes and is characterised by high mass transfer rates and good mixing. At present, a full-scale sulphate-reducing reactor is running in which metals precipitation results in 20% solids concentration in the gas-lift reactor. From in-house desk studies and experimental work carried out on pilot plant scale and full scale, it is concluded that the Circox® air-lift loop reactor is a viable alternative to stirred tank reactors for the bio-oxidation of minerals. The main advantages of the air-lift loop reactor over the conventional stirred tank reactor are lower capital and operational expenditures and the ease of scale-up.

Scale-up aspects of photobioreactors : effects of mixing-induced light/dark cycles

The green micro-algae Chlamydomonas reinhardtiiand Dunaliella tertiolecta were cultivated undermedium-duration square-wave light/dark cycles with acycle time of 15 s. These cycles were used to simulatethe light regime experienced by micro-algae inexternally-illuminated (sunlight) air-lift loopbioreactors with internal draft tube. Biomass yieldin relation to light energy was determined as gprotein per mol of photons (400–700 nm). Between 600and 1200 μmol m-2 s-1 the yield at a10/5 s light/dark cycle was equal to the yield atcontinuous illumination. Consequently, provided thatthe liquid circulation time is 15 s, a considerabledark zone seems to be allowed in the interior ofair-lift loop photobioreactors (33% v/v) without lossof light utilization efficiency. However, at a 5/10 slight/dark cycle, corresponding to a 67% v/v darkzone, biomass yield decreased. Furthermore, bothalgae, C. reinhardtii and D. tertiolecta,responded similarly to these cycles with respect tobiomass yield. This was interesting because they werereported to exhibit a different photoacclimationstrategy. Finally, it was demonstrated that D.tertiolecta was much more efficient at low (average)photon flux densities (57–370 μmol m-2s-1) than at high PFDs (> 600 μmol m-2s-1) and it was shown that D. tertiolectawas cultivated at a sub-optimal temperature (20 °C).