Laboratory-scale Column Reactor Research Articles

Synergism in nitrate and orthophosphate removal in subsurface bioreactors

Fertilizers replenish soil nutrients removed by crops and help in producing high yielding crops, but the overuse of these fertilizers can have a detrimental effect on the receiving waters. There is a need for better management practices and remediation techniques to reduce and potentially eliminate the transport of nutrients from agricultural lands. The objective of this study was to evaluate the removal of orthophosphate using an industrial waste (iron turnings) as well as examine the synergistic effects of using it in conjunction with a woodchip bioreactor known to have a high affinity for nitrate-N removal. A laboratory-scale column reactor was constructed using the iron-based material and woodchips as reactor media. Synergism was displayed as a result of alternating media arrangement with the observation of 25% higher reduction in nitrate-N concentrations, on average, as a result of interaction with woodchips when woodchips were downstream of steel turnings as opposed to upstream. This was also demonstrated in the orthophosphate results, where woodchips reduced orthophosphate concentrations by 8.54% on average when upstream of steel turnings, but yielded a net increase in orthophosphate concentration (23.8% of initial concentration on average) by converting bound phosphate back to orthophosphate when downstream of steel turnings. This led to a final experiment where the steel turnings were placed both upstream and downstream of woodchips. This confirmed earlier findings of enhanced nitrate-N removal by woodchips downstream of iron, while showing that the second iron section downstream of woodchips could once again remove orthophosphate from solution down to non-detectable concentrations.

Kinetics of Chromium(VI) Reduction with Acetate Biodegradation byEscherichia coli33456 in a Fixed Biofilm Reactor

Abstract A kinetic model was developed to describe the Cr(VI) reduction with acetate biodegradation by Escherichia coli 33456 in a fixed film reactor. A laboratory-scale column reactor was used to verify the model system. Batch kinetic tests were independently performed to determine biokinetic parameters used in model simulation. With assumed values of initial biofilm thickness (Lf0), the mathematical model simulated well experimental results for effluent concentrations of Cr(VI) and acetate, suspended E. coli cells, and Cr(III) production. The concentration of suspended E. coli cells reached 11.4 mg cell/L while the thickness of attached E. coli cells was estimated to be 27.8 μm at a steady state condition. At steady state, removal efficiencies of Cr(VI) and acetate were about 92% and 90%, respectively, under influent Cr(VI) loading rate (11.3 g/[m3·day]) and acetate loading rate (664.4 g/[m3·day]) at a hydraulic retention time of 10.7 h, while the effluent concentration of Cr(III) was ∼1.65 mg/L. The ki...

Innovative use of Mucuna monosperma (Wight) callus cultures for continuous production of melanin by using statistically optimized biotransformation medium

Melanins are predominantly indolic polymers which are having extensive applications in cosmetics, agriculture and medicine. In the present study, optimization of nutritional parameters influencing melanin production by Mucuna monosperma callus cultures was attempted using the response surface methodology (RSM). Standardization of four factors was carried out using the Box–Behnken design. The optimized levels of factors predicted by the model include tyrosine 0.978gL−1, pH 5.85, SDS 34.55mgL−1and copper sulphate 21.14mgL−1 tyrosine, which resulted in highest melanin yield of 0.887gL−1. The optimization of medium using RSM resulted in a 3.06-fold increase in the yield of melanin. The ANOVA analysis showed a significant R2-value (0.9995), model F-value (1917.72) and probability (0.0001), with insignificant lack of fit. Optimized medium was used in the laboratory scale column reactor for the continuous production of melanin. Uninterrupted flow column exhibited maximum melanin production rate of 250mgL−1h−1 which is the highest value ever reported using plant as a biotransformation source. Melanin production was confirmed by spectrophotometric and chemical analysis. Thus, this study demonstrates the production of melanin by M. monosperma callus, using a laboratory scale column reactor.

Modeling chromium(VI) reduction by Escherichia coli 33456 using ceramic pearl as a supporting medium

A mathematical model was developed to describe the reduction of Cr(VI) by Escherichia coli (E. coli) 33456 in a fixed biofilm reactor. A laboratory-scale column reactor was conducted to verify the model system. The batch kinetic tests were independently conducted to determine the biokinetic parameters used in the model simulation. With the assumed values of initial biofilm thickness (Lf0), the mathematical model simulated well the experimental results for Cr(VI) effluent concentration, effluent concentration of suspended E. coli cells, and Cr(III) production. The concentration of suspended E. coli cells reached up to 1.2 mg cell/L while the thickness of attached E. coli cells was estimated to be 32.6 μm at a steady-state condition. At the steady state, the removal efficiency of Cr(VI) was about 92 % and the effluent concentration of Cr(III) was approximately 1.6 mg/L. The approaches presented in this study can be employed for the design of a pilot-scale or full-scale fixed biofilm reactor to treat Cr(VI)-containing wastewater.

Statistically optimized biotransformation protocol for continuous production of L-DOPA using Mucuna monosperma callus culture

L-DOPA (3,4-dihydroxyphenyl-L-alanine), a modified amino acid, is an expansively used drug for the Parkinson’s disease treatment. In the present study, optimization of nutritional parameters influencing L-DOPA production was attempted using the response surface methodology (RSM) from Mucuna monosperma callus. Optimization of the four factors was carried out using the Box–Behnken design. The optimized levels of factors predicted by the model include tyrosine 0.894 g l-1, pH 4.99, ascorbic acid 31.62 mg l-1and copper sulphate 23.92 mg l-1, which resulted in highest L-DOPA yield of 0.309 g l-1. The optimization of medium using RSM resulted in a 3.45-fold increase in the yield of L-DOPA. The ANOVA analysis showed a significant R2 value (0.9912), model F-value (112.465) and probability (0.0001), with insignificant lack of fit. Optimized medium was used in the laboratory scale column reactor for continuous production of L-DOPA. Uninterrupted flow column exhibited maximum L-DOPA production rate of 200 mg L-1 h-1 which is one of the highest values ever reported using plant as a biotransformation source. L-DOPA production was confirmed by HPTLC and HPLC analysis. This study demonstrates the synthesis of L- DOPA using Mucuna monosperma callus using a laboratory scale column reactor.

Hydraulic conductivity and removal rate of compacted clays permeated with landfill leachate

Compacted clay soils are widely used as a barrier to protect environment from leachate migration. The suitability of clay soil for liner material, depends on resistibility to increase in hydraulic conductivity and contaminant transport. In this article, the influence of compaction energy and permeated leachate properties on the hydraulic conductivity were investigated. Natural attenuation capacities of clays compacted both standard and modified compaction methods were also evaluated. With this purpose, a series of laboratory tests were conducted with soil and real leachate samples obtained from Şile-Kömürcüoda Organized Landfill Site. DI and real leachate samples were percolated through the laboratory-scale column reactors that were filled with compacted clay samples prepared according to Standard and Modified Proctor method. During percolation, the hydraulic conductivity and natural attenuation capacity of the clay liner were determined by hydraulic conductivity calculation and chemical oxygen demand (COD), suspenden solids (SS), total Kjeldahl nitrogen (TKN), total phosphorus (TP) monitoring, respectively. According to the hydraulic conductivity measurements using leachate, it is shown that hydraulic conductivity decreased in both compacted clay prepared by Standard and Modified Proctor methods, possibly associated with biological and chemical clogging mechanisms. It is thought that clogging formed due to biofilm growth and/or suspended solids accumulation between the particles of the clay soil. When the variations of the COD, SS, TKN, and TP were examined, it was observed that the removal efficiency of the clay compacted by the modified compaction method was greater than the one compacted by the standard compaction method, especially for SS.

Some aspects of the effect of pH and acid stress in heap bioleaching

The chemical and physical conditions in sulphide heaps provide a complex environment for micro-organisms, with differences in redox potential, acidity, temperature, oxygen and solution chemistry conditions being experienced both temporally and spatially. One of the most important parameters for successful microbial colonisation and active microbial metabolism is suitable pH conditions in the heap. Typically heaps reach tens of metres high and the pH of irrigation solution travelling through heap changes significantly. In this study, we investigated the effect of pH and acid stress for moderately thermophilic and thermophilic mixed cultures, operating at 50–60 °C in a heap bioleaching environment. Results collected from laboratory scale column reactors packed with the low grade whole ore and irrigated with different pH solutions during a temperature shift from moderately thermophilic conditions to thermophilic conditions are discussed.

Column Bioleaching of a Low-Grade Silicate Ore of Uranium

The bioleaching of a low-grade Indian uraninite ore (triuranium octoxide, U3O8: 0.024%), containing ferro-silicate and magnetite as the major phases, and hematite and pyrite in minor amounts, has been reported. Experiments were carried out in laboratory scale column reactors inoculated with enriched culture of Acidithiobacillus ferrooxidans isolated from the source mine water. The pH effect on uranium recovery was examined with the same amounts of ores in different columns. With the presence of 10.64% Fe in the ore as ferro-silicate, the higher uranium biorecovery of 58.9% was observed with increase in cell count from 6.4 × 107 to 9.7 × 108 cells/mL at pH 1.7 in 40 days as compared to the uranium recovery of 56.8% at pH 1.9 with a corresponding value of 9.4 × 108 cells/mL for 2.5-kg ore in the column. The dissolution of uranium under chemical leaching conditions, however, recorded a lower value of 47.9% in 40 days at room temperature. Recoveries were similar with 6-kg ore when column leaching was carried out at pH 1.7. The bioleaching of uranium from the low-grade ore of Turamdih may be correlated with the iron(II) and iron(III) concentrations, and redox potential values.

Biodegradation of phenol with chromium(VI) reduction in an anaerobic fixed-biofilm process—Kinetic model and reactor performance

A mathematical model system was derived to describe the simultaneous removal of phenol biodegradation with chromium(VI) reduction in an anaerobic fixed-biofilm reactor. The model system incorporates diffusive mass transport and double Monod kinetics. The model was solved using a combination of the orthogonal collocation method and Gear's method. A laboratory-scale column reactor was employed to validate the kinetic model system. Batch kinetic tests were conducted independently to evaluate the biokinetic parameters used in the model simulation. The removal efficiencies of phenol and chromium(VI) in an anaerobic fixed-biofilm process were approximately 980 mg/g and 910 mg/g, respectively, under a steady-state condition. In the steady state, model-predicted biofilm thickness reached up to 350 μm and suspended cells in the effluent were 85 mg cell/l. The experimental results agree closely with the results of the model simulations.

Kinetics of biodegradation of phenolic wastewater in a biofilm reactor

This work presents a mathematical model to describe the biodegradation of phenolic wastewater in a fixed-biofilm process. The model incorporates diffusive mass transport and Haldane kinetics mechanisms. The model was solved using a combination of the orthogonal collocation method and Gear's method. A laboratory-scale column reactor was employed to verify the model. Batch kinetic tests were conducted independently to determine biokinetic parameters for the model simulation with the initial biofilm thickness assumed. The model simulated the phenol effluent concentration results well. Removal efficiency for phenol was approximately 94-96.5% for different hydraulic retention times at a steady-state condition. Model simulations results are in agreement with experimental results. The approaches of model and experiments presented in this paper could be used to design a pilot-scale or full-scale fixed-biofilm reactor system for the biodegradation of phenolic wastewater from petrochemical and oil refining plants.

Biodegradation of phenolic wastewater in a fixed biofilm reactor

A mathematical model was developed to describe the biodegradation of phenolic wastewater in a fixed biofilm process. The model was solved using a combination of orthogonal collocation method and Gear's method. A laboratory-scale column reactor was conducted to verify the model system. The batch kinetic tests were independently conducted to determine biokinetic parameters used in the model simulation while initial thickness of biofilm was assumed so that the model simulated the phenol effluent concentration curve very well. The removal efficiency for phenol was 94%. At a steady-state condition, the phenol concentration obtained from experimental data was slightly higher than that obtained from the model simulation. The approaches presented in this paper could be employed for the design of a fixed biofilm reactor system for the biodegradation of phenolic wastewater in petrochemical and oil refining industries.

Column Studies on Nitrate Removal from Potable Water

Biological processes can achieve nitrate removal from groundwater. The sulfur/limestone autotrophic denitrification by Thiobacillus denitrificans was evaluated with three laboratory-scale column reactors. The optimum sulfur/limestone ratio was determined to be 2:1 (mass/mass). Different hydraulic retention times were used during the column tests to examine nitrate removal efficiencies. Under an HRTs of 13 h, nitrate concentration of 60 mgNO3--N L-1 was reduced to less than 5 mg NO3--N L-1. On a higher HRT of 26 h the nitrate removal efficiency was close to 100% for all nitrate-nitrogen loading rates. Different initial nitrate-nitrogen concentrations (30, 60, and 90 mg NO3--N L-1) were used in the study. Column tests showed that the nitrate-nitrogen loading rate in this study was between 50 to 100 g NO3--N m-3 d-1 to obtain a removal efficiency of 80–100%. It was found that approximately 6 mg SO42- was produced for 1 mg NO3--N removed. Nitrite-nitrogen in all cases was less than the maximum allowable concentration of 1 mg NO2--N L-1. Effluent pH was stable in the range of 7 to 8; the effluent dissolved oxygen was less than 0.15 mg L-1 and the oxidation-reduction potential in all columns was in the range of –110 to –250 mV.

Degradation of phenol by Rhodococcus erythropolis UPV-1 immobilized on Biolite® in a packed-bed reactor

A strain of Rhodococcus erythropolis has been isolated and identified by 16S rRNA sequencing. Cells acclimated to phenol can be adsorbed on the external surface of beads of the ceramic support Biolite® where they grow forming a network of large filaments. Exponentially-growing cells were adsorbed faster than their stationary-phase counterparts. Immobilization resulted in a remarkable enhancement of the respiratory activity of cells and a shorter lag phase preceding the active phenol degradation. Under optimum operation conditions, the immobilized cells in a laboratory-scale column reactor packed with support beads were able to degrade completely phenol in defined mineral medium at a maximum rate of 18 kg phenol m −3 per day. The performance of the bioreactor in long-term continuous operation was characterized by pumping defined mineral medium which contained different concentrations of phenol at different flow-rates. Once phenol biodegradation in defined mineral medium was well established, an industrial wastewater from a resin manufacturing company, which contained both phenol and formaldehyde, was tested. In this case, after wastewater conditioning (i.e. pH, nitrogen source and micronutrient amendments) the immobilized cells were able to remove completely formaldehyde and to partly biodegrade phenols at a rate of 1 kg phenol m −3 per day.