Two-phase Partitioning Bioreactor Research Articles

Polymer extraction and ex situ biodegradation of xenobiotic contaminated soil: Modelling of the process concept

An integrated model of a two-step process for the ex situ bioremediation of xenobiotic contaminated soil has been formulated. The process is characterized by an initial extraction step of the organic contaminants from the polluted soil by contact with inexpensive and commercially-available polymer beads, followed by release and biodegradation of the xenobiotics, with parallel polymer bioregeneration, in a Two-Phase Partitioning Bioreactor (TPPB). The regenerated polymer is cyclically reused in the extraction step, so reflecting the robust and otherwise-inert properties of such polymers. The model was calibrated and validated for a soil contaminated with 4-nitrophenol (4NP) and treated with the DuPont polymer Hytrel 8206. In the model calibration, the partition coefficient polymer-soil, Pps, and the mass transfer coefficient, K, were evaluated, as 105.3 and 0.24 h−1 respectively. A diffusion coefficient within the polymer of 6.3 10−8 cm2 s−1 was determined from the fitting of sorption/desorption data. The model was then tested for two alternative process configurations consisting of either one or two soil extraction units, followed by the biodegradation/bioregeneration step. The latter configuration resulted in more effective polymer utilization and is suitable if each extraction step requires a shorter time than the regeneration step. The model predicted that an extraction time of 12 h was sufficient to reach removal efficiencies ≥90% while the biodegradation/bioregeneration step required 24 h to reach efficiencies ≥93%, with a good agreement with experimental data (R2 > 0.98 for both cases). The simulation of the process operated with two extraction units showed a better performance with a final concentration ∼0.2 g4NP kgds−1 vs. 1.69 g4NP kgds−1 obtained with single extraction unit, for a soil contaminated with 10 g4NP kgds−1. Corresponding extraction efficiencies were 96 and 83%, respectively.

Characterization and selection of waste oils for the absorption and biodegradation of VOC of different hydrophobicities

The purpose of this study was to test different kinds of industrial waste oils to be implemented as Non-Aqueous-Phase for Volatile Organic Compounds absorption and degradation in a process coupling a packed column and a Two-Phase Partitioning Bioreactor. Engine, hydraulic, transformer and vegetable oils were tested. The VOC targeted were: n-heptane, ethyl acetate, isopropanol, methylisobutylketone, toluene, m-xylene and 1,3,5-trimethylbenzene. Several parameters were determined: volatility, viscosity, VOC partition coefficients and toxicity. Results allowed to conclude that hydraulic, transformer and vegetable oils are technically appropriate for the process. According to availability and cost data of waste oils, hydraulic oil was selected.

Removal of gaseous dichloromethane using a solid–liquid partitioning bioreactor under gradual and stepped load increase

Silicone rubber was used as the solid non-aqueous phase of two-phase partitioning bioreactor (TPPB) for dichloromethane (DCM) removal. When the load gradually increased from 150 g m−3 h−1–485 g m−3 h−1 by increasing the gaseous DCM concentration, a steady elimination capacity (EC) of approximately 130 g m−3 h−1 was achieved in one-liquid-phase completely mixed stirred tank bioreactor (CSTB), whereas the EC of TPPB was enhanced from 155 g m−3 h−1–366 g m−3 h−1. This result indicated that DCM removal was controlled by the biological process in CSTB and by mass transfer in TPPB. Meanwhile, the biomass decreased from 534 mg l−1 to 381 mg l−1 in CSTB compared with that maintained at around 580 mg l−1 in TPPB due to the different resistance capabilities to DCM toxicity. Dehalogenase activity was maintained at a relatively high level under high DCM stress with the addition of silicon rubber. TPPB was shown to be more dependable in the overload from 120 g m−3 h−1–450 g m−3 h−1. This paper is the first to report that the crucial step in high-load pollutant removal can be converted from the biological process to mass transfer by adding solid non-aqueous phase.

Biological treatment of hypersaline wastewater in a continuous two-phase partitioning bioreactor: Analysis of the response to step, ramp and impulse loadings and applicability evaluation

Abstract The response of a continuous two-phase partitioning bioreactor (C-TPPB) operated with polymeric tubing treating hypersaline wastewater was investigated under dynamic load conditions of step, ramp and impulse inputs of the influent flow rate. Tests were performed with synthetic wastewater consisting of NaCl (100 g L−1) and 2,4-dimethylphenol (DMP) (∼1200 mg L−1) to simulate the organic fraction. A biomass specifically acclimatized to the compound was utilized in the tests. The experimental system provides separation of the toxic wastewater flowing inside the polymeric tubing (coiled in the bioreactor) from the microbial culture present in the bulk bioreactor phase with the polymer providing permeability to the organic molecules as well as a barrier to salt transport. These features allowed achieving high performance even in the most severe loading conditions. Removal efficiencies >96% were obtained for DMP under all investigated load conditions (i.e. for influent salt and organic loads up to six times the base case load). A DMP mass balance at the end of the dynamic tests showed that 88% of the removed DMP was biodegraded and only 8% was retained into the polymer tubing itself. No significant variation of the DMP concentration in the bioreactor was observed in all cases thus demonstrating the complete removal of the transferred substrate and the effective performance of the biomass, which was not affected by the applied dynamic loads. A comparative analysis of C-TPPB results with the performance data of the classical technologies commonly applied for saline wastewater treatment has been performed to evaluate the system applicability.

Hydrophobic mixed culture for 1,2-dichloroethane biodegradation: Batch-mode biodegradability and application performance in two-phase partitioning airlift bioreactors

Abstract Recent studies highlighted that hydrophobic microorganisms played key roles in VOC removal performance of two-phase partitioning bioreactors (TPPBs). The objective of this study was to evaluate the performance of a hydrophobic mixed culture for 1,2-dichloroethane (1,2-DCA) biodegradation in both batch and TPPB tests. The hydrophobic mixed culture with cell surface hydrophobicity of 79% was acclimated from an activated sludge able to efficiently degrade 1,2-DCA as sole carbon and energy source. It was primarily composed of Xanthobacter genus (62%). Nearly complete degradation with coefficients of 0.80 mgCO2 mg1,2-DCA−1 and 0.66 mgCl− mg1,2-DCA−1 was achieved for a wide range of 1,2-DCA concentrations (114.1–1141.5 mg L−1) in the presence of silicone oil. The maximum specific growth rate was 0.247 h−1 which was approximately two times the values of previous pure strains. The two-phase partitioning airlift bioreactors inoculated with the hydrophobic mixed culture was robust against step changes of gas flow rates and spike changes of inlet 1,2-DCA concentrations. All data proved the potential of the hydrophobic mixed culture for toxic-VOC removal in the TPPBs.

Biotrickling filter modeling for styrene abatement. Part 2: Simulating a two-phase partitioning bioreactor

A dynamic model describing styrene abatement was developed for a two-phase partitioning bioreactor operated as a biotrickling filter (TPPB-BTF). The model was built as a coupled set of two different systems of partial differential equations depending on whether an irrigation or a non-irrigation period was simulated. The maximum growth rate was previously calibrated from a conventional BTF treating styrene (Part 1). The model was extended to simulate the TPPB-BTF based on the hypothesis that the main change associated with the non-aqueous phase is the modification of the pollutant properties in the liquid phase. The three phases considered were gas, a water–silicone liquid mixture, and biofilm. The selected calibration parameters were related to the physical properties of styrene: Henry's law constant, diffusivity, and the gas–liquid mass transfer coefficient. A sensitivity analysis revealed that Henry's law constant was the most sensitive parameter. The model was successfully calibrated with a goodness of fit of 0.94. It satisfactorily simulated the performance of the TPPB-BTF at styrene loads ranging from 13 to 77 g C m−3 h−1 and empty bed residence times of 30–15 s with the mass transfer enhanced by a factor of 1.6. The model was validated with data obtained in a TPPB-BTF removing styrene continuously. The experimental outlet emissions associated to oscillating inlet concentrations were satisfactorily predicted by using the calibrated parameters. Model simulations demonstrated the potential improvement of the mass-transfer performance of a conventional BTF degrading styrene by adding silicone oil.

Impact of activated sludge acclimation on the biodegradation of toluene absorbed in a hydrophobic ionic liquid

Classical hydrophobic ionic liquids such as 3-butyl-1-methylimidazolium bis(trifluoroethylsulfonyl)imide or 3-butyl-1-methylimidazolium hexafluorophosphate application, as a non-aqueous liquid phase in a two-partitioning bioreactor to biodegrade hydrophobic volatile organic compounds by activated sludge, have been already reported in the literature, especially when the activated sludge was beforehand acclimated to the targeted volatile organic compound. In this study, four hydrophobic ionic liquids were used as non-aqueous liquid phase in a two-phase partitioning bioreactor to biodegrade toluene using non-acclimated activated sludge. The preliminarily results allowed to select two ionic liquids, 1-octylisoquinolinium bis(trifluoromethylsulfonyl)imide and allyl-diethylsulfonium bis(trifluoromethylsulfonyl)imide. The activated sludge was acclimated to both toluene and the considered ionic liquid. The results were compared to those obtained with non-acclimated activated sludge. The use of non-acclimated activated sludge for toluene biodegradation led to long lag times and low biodegradation rates. Thus, the acclimation to toluene improved the biodegradation rates; however, acclimation to both toluene and ionic liquid did not result in a significant improvement in the biodegradation rate compared to an acclimation to toluene alone. The activated sludge acclimation had a positive impact on toluene biodegradation and allowed to totally overcome the inhibitory effect of the presence of ionic liquid. The most relevant acclimation strategy seems to be a prior acclimation to toluene, whereas acclimation to the non-aqueous liquid phase can be achieved during the culture, namely by performing successive batches for instance, or a continuous operation.

Removal of polycyclic aromatic hydrocarbons from contaminated soil in a two-phase partitioning bioreactor

A two-phase partitioning bioreactor was employed to remediate soil contaminated by a mixture of polycyclic aromatic hydrocarbons consisting of phenanthrene, anthracene, and pyrene. In this study, the transfer of three PAHs into the water-immiscible liquid phase (silicone oil or paraffine oil) from the soil was investigated during the first 24 h. And then, phenanthrene and anthracene were degraded by approximately 90% and 80%, respectively, compared with initial concentration in soil, but pyrene was not degraded during seven days of operation period. In addition, the feasibility of a soil slurry sequencing batch reactor system in terms of continuously operating a two-phase partitioning bioreactor was investigated. Phenanthrene and anthracene were degraded semi-continuously and repeatedly during two operating cycles. Pyrene was still not degraded and was just transferred into the water-immiscible liquid phase considering its solubility.

Ionic liquids toxicity on fresh water microalgae, Scenedesmus quadricauda, Chlorella vulgaris &Botryococcus braunii; selection criterion for use in a two-phase partitioning bioreactor (TPPBR)

A promising method of Carbon dioxide (CO2) valorization is to use green microalgae photosynthesis to process biofuel. Two Phase Partitioning Bioreactors (TPPBR) offer the possibility to use non-aqueous phase liquids (NAPL) to enhance CO2 solubility; thus making CO2 available to maximize algae growth. This requires relatively less toxic hydrophobic Ionic Liquids (ILs) that comprise a new class of ionic compounds with remarkable physicochemical properties and thus qualifies them as NAPL candidates. This paper concerns the synthesis of ILs with octyl and butyl chains as well as different cations containing aromatic (imidazolium, pyridinium) and non-aromatic (piperidinum, pyrrolidinium) rings for CO2 absorption studies. The authors measured their respective toxicity levels on microalgae species, specifically, Scenedesmus quadricauda, Chlorella vulgaris and Botryococcus braunii.Results revealed that octyl-based ILs were more toxic than butyl-based analogues. Such was the case for bmim-PF6 at double saturation with an absorbance of 0.11, compared to Omim-PF6 at 0.17, bmim-NTf2 at 0.02, and Omim-NTf2 at 0.14, respectively. CO2 uptake results for ILs bearing octyl-based chains compared to the butyl analog were 54% (nCO2/nIL) (i.e., moles of CO2 moles of IL) and 38% (nCO2/nIL), respectively.Conclusively, 1-butyl-1-methylpiperidinium absorbed 13% (nCO2/nIL) and appeared the least toxic, having an absorbance of 0.25 at 688 nm (double saturation at 7 d) compared to 1-butyl-3-methylimidazolium, which showed the highest toxicity with zero absorbance. Accordingly, these findings suggest that 1-butyl-1-methylpiperidinium is capable of transporting CO2 to a system containing green microalgae without causing significant harm; thus allowing its use in TPPBR technology.

Treatment of synthetic tannery wastewater in a continuous two-phase partitioning bioreactor: Biodegradation of the organic fraction and chromium separation

A continuous two-phase partitioning bioreactor has been tested for treating a synthetic leather tannery wastewater with the objective of achieving effective removal of the organic load and complete chromium separation. The bioreactor was operated with 5.5 m of Hytrel 8206 polymeric tubing fed with a synthetic tannery wastewater consisting of 4-chlorophenol (concentration in the range of 1000–2500 mg L−1) and potassium dichromate (100 mg L−1 as Cr (VI)), and immersed in a 4 L bioreactor containing the microbial culture acclimatized to the compound. This configuration prevents the direct contact between the toxic wastewater and the microorganisms themselves, and provides the gradual organic substrate delivery through the tubing walls. Abiotic partition and mass transfer tests were performed to investigate the transport of dichromate and 4-chlorophenol across the tubing into the bulk phase of the bioreactor. No appreciable mass transfer of dichromate was detected. During biotic testing, the influent organic load in tubing has been varied in the range of 19–94 mg h−1 and the hydraulic retention time from 3 to 6 h. Achieved biological removal efficiencies were in the range of 89–95% for the highest applied loads. Process kinetics (which included consideration of both mass transfer and biological rates) were evaluated, and it was found that the increased load did not result in any decrease in 4-chlorophenol removal rate. This work has shown that the continuous two-phase partitioning bioreactor has significant potential in enhancing the biological treatment of tannery wastewater, which is a typical representative of industrial “hostile” wastewater.

O-Xylene removal using one- and two-phase partitioning biotrickling filters: steady/transient-state performance and microbial community

ABSTRACTIn this study, one- and two-phase partitioning biotrickling filters (1P-BTF and 2P-BTF, respectively) inoculated with a pre-acclimated mixed culture were examined for the removal of hydrophobic and refractory o-xylene. A small fraction of silicone oil (5% v/v) was added as a non-aqueous phase. Due to the presence of silicone oil, the 2P-BTF exhibited superior performance and stability for o-xylene biodegradation at steady and transient operations. Higher macro-kinetic constants for o-xylene removal by the Michaelis–Menten model were obtained for the 2P-BTF with a saturation constant of 0.396 g m−3 and a maximum elimination capacity of 105.7 g m−3 h−1. The enhancement of removal performance for the 2P-BTF was supported by dominant specialized microorganisms with o-xylene biodegradability. The diversity of microbial community was influenced by the presence of silicone oil. This study demonstrated that a BTF with 5% of silicone oil could be applied for the treatment of hydrophobic and refractory volatile organic compounds. It also provided valuable information for better understanding the relationship between microbial community and removal performance using two-phase partitioning bioreactors.

Toluene degradation by a water/silicone oil mixture for the design of Two Phase Partitioning Bioreactors

Abstract Toluene degradation performances were studied in a 10 L Two-Phase Partitioning Bioreactor (TPPB). The liquid phase consisted of a mixture of water and PDMS 50 (PolyDiMethylSiloxane, i.e. silicone oil, viscosity of 46 mPa·s) in the volume ratio of 75%/25%. Two series of experiments were carried out: in the first, the reactor was sequentially supplied with toluene whereas in the second, toluene was continuously supplied. Activated sludge from the wastewater treatment plant of Beaurade (Rennes, France) was used at an initial concentration of 0.5 gdry weight L− 1mixture. The elimination capacity (EC) was investigated as well as the change in biomass concentration over time. Toluene biodegradation was very efficient (removal efficiency, RE = 100%) for toluene flows ranging from 0.2 to 1.2 ml·h− 1, corresponding to elimination capacities of up to 104 g·m− 3·h− 1. For a toluene flow of 1.2 ml·h− 1, the biomass concentration measured at the end of the experiment was 4.7 gdry weight L− 1mixture. The oxygen concentration in the liquid phase was clearly not a limiting factor in these operating conditions. Based on these results, an extrapolation leading to the design of a large-scale pilot TPPB can now be considered to study toluene degradation performances in industrial conditions.

A novel continuous two-phase partitioning bioreactor operated with polymeric tubing: Performance validation for enhanced biological removal of toxic substrates

A continuous two-phase partitioning bioreactor (C-TPPB), operated with coiled tubing made of the DuPont polymer Hytrel 8206, was tested for the bioremediation of 4-chlorophenol, as a model toxic compound. The tubing was immersed in the aqueous phase, with the contaminated water flowing tube-side, and an adapted microbial culture suspended in the bioreactor itself, with the metabolic demand of the cells creating a concentration gradient to cause the substrate to diffuse into the bioreactor for biodegradation. The system was operated over a range of loadings (tubing influent concentration 750–1500 mg L−1), with near-complete substrate removal in all cases. Distribution of the contaminant at the end of the tests (96 h) highlighted biological removal in the range of 87–95%, while the amount retained in the polymer ranged from ∼1 to 8%. Mass transfer of the substrate across the tubing wall was not limiting, and the polymer demonstrated the capacity to buffer the substrate loadings and to adapt to microbial metabolism. The impact of C-TPPB operation on biomass activity was also investigated by a kinetic characterization of the microbial culture, which showed better resistance to substrate inhibition after C-TPPB operation, thereby confirming the beneficial effect of sub-inhibitory controlled conditions, characteristic of TPPB systems.

Toluene degradation in a two-phase partitioning bioreactor involving a hydrophobic ionic liquid as a non-aqueous phase liquid

An ionic liquid (IL), 1-octylisoquinolinium bis(trifluoromethyl-sulfonyl) imide also known as [OctIq][NTf2], was selected, since it complies with all the requested characteristics to be used as non-aqueous phase liquid (NAPL) in a two-phase partitioning bioreactor (TPPB) dedicated to the biological treatment of the hydrophobic volatile organic compound, toluene. Various operating parameters were investigated and the performances were compared to those recorded in the absence of NAPL. With an aeration flow rate of 0.2 L min−1 and in the presence of [OctIq][NTf2] as NAPL in a TPPB of 12 L, the system allowed to avoid toluene stripping and to totally remove toluene at different concentrations ranging from 0.55 to 1.13 g L−1. However, and even if the ionic liquid addition seemed to decrease the toluene biodegradation rate, higher toluene concentrations could be treated due to the high affinity of toluene for the selected IL. For high toluene concentrations, biodegradation rate might be limited by the oxygen supply because the dissolved oxygen concentration was almost zero. [OctIq][NTf2] appears to be a suitable NAPL for the biological treatment of toluene. To improve both toluene and oxygen availabilities, the NAPL-to-water ratio should be investigated in order to optimize the interfacial area due to the dispersion of [OctIq][NTf2] droplets in water, as well as the effect of aeration rate on toluene biodegradation rates.

Enhanced styrene removal in a two-phase partitioning bioreactor operated as a biotrickling filter: Towards full-scale applications

Styrene vapor abatement was investigated in a two-phase partitioning bioreactor operated as a biotrickling filter (TPPB-BTF). The removal performance of the TPPB-BTF was simultaneously compared with a conventional BTF, which served as a control. Industrial-grade silicone oil was used as the non-aqueous phase in the TPPB-BTF due to its high affinity for styrene. Both bioreactors were operated at styrene inlet concentrations ranging from 55 to 323mgCm−3 and empty bed residence times (EBRT) of 15–30s, corresponding to pollutant loading rates of 13–77gCm−3h−1. Both bioreactors exhibited styrene removal efficiencies (REs) higher than 90% at an EBRT of 30s. Nevertheless, the TPPB-BTF showed a superior removal performance than that recorded in the control BTF at EBRTs shorter than 30s. REs of 89%, 84% and 57% were recorded in the TPPB-BTF at EBRT of 15s and loading rates of 13, 22 and 77gCm−3h−1, respectively, while the control BTF supported removal efficiencies of 64%, 42% and 18–42% under the same experimental conditions. The resilience and robustness of the TPPB-BTF over styrene shock loadings and transient inlet concentration was also confirmed, the TPPB-BTF being able to recover a stable RE of 89% one day after such operation disturbances. The potential of the TPPB-BTF towards full scale applications was also critically discussed based on the experimental determination of silicone oil loses through aqueous phase renewal, which accounted for 0.4% of the initial volume of oil added to the TPPB-BTF after 87 days of operation.

Experimental and CFD-PBM Study of Oxygen Mass Transfer Coefficient in Different Impeller Configurations and Operational Conditions of a Two-Phase Partitioning Bioreactor.

In this work, gas dispersion in a two-phase partitioning bioreactor is analyzed by calculating volumetric oxygen mass transfer coefficient which is modeled using a commercial computational fluid dynamics (CFD), code FLUENT 6.2. Dispersed oxygen bubbles dynamics is based on standard "k-ε" Reynolds-averaged Navier-Stokes (RANS) model. This paper describes a three-dimensional CFD model coupled with population balance equations (PBE) in order to get more confirming results of experimental measurements. Values of k L a are obtained using dynamic gassing-out method. Using the CFD simulation, the volumetric mass transfer coefficient is calculated based on Higbie's penetration theory. Characteristics of mass transfer coefficient are investigated for five configurations of impeller and three different aeration flow rates. The pitched six blade type, due to the creation of downward flow direction, leads to higher dissolved oxygen (DO) concentrations, thereby, higher values of k L a compared with other impeller compositions. The magnitude of dissolved oxygen percentage in the aqueous phase has direct correlation with impeller speed and any increase of the aeration magnitude leads to faster saturation in shorter periods of time. Agitation speeds of 300 to 800rpm are found to be the most effective rotational speeds for the mass transfer of oxygen in two-phase partitioning bioreactors (TPPB).

Sequential anaerobic-aerobic decolourization of a real textile wastewater in a two-phase partitioning bioreactor

This work describes the application of a solid-liquid two-phase partitioning bioreactor (TPPB) for the removal of colour from a real textile wastewater containing reactive azo-dyes. Four polymers were tested over the pH range of 4–9 to select the most effective absorbant to be used as the partitioning phase in the TPPB. The best results were obtained with Hytrel 8206 at pH4 achieving ~70% colour removal, based on the dominant wavelength, in the first 5h of contact time, and 84% after 24h. Wastewater treatment was undertaken in a solid-liquid TPPB operated with Hytrel 8206 in sequential anaerobic-aerobic configuration. The reaction time of 23h was equally distributed between the anaerobic and aerobic phases and, to favour colour uptake, the pH was controlled at 4.5 in the first 4h of the anaerobic phase, and then increased to 7.5. Colour removal (for the dominant wavelength, 536nm) increased from 70 to 85% by modifying the bioreactor operation from single-phase to TPPB mode. Based on COD measurements nearly complete biodegradation of the intermediates produced in the anaerobic phase was obtained, both in the single-phase and two-phase mode, with better performance of the TPPB system reaching 75% CODDye removal.

Experimental and CFD–PBM approach coupled with a simplified dynamic analysis of mass transfer in phenol biodegradation in a three phase system of an aerated two-phase partitioning bioreactor for environmental applications

A three-dimensional transient modeling of a two-phase partitioning bioreactor, combining system hydrodynamics, two simultaneous mass transfer and microorganism growth is modeled using computational fluid dynamics code FLUENT 6.2. The simulation is based on standard “k–e” Reynolds-averaged Navier–Stokes model. Population balance model is implemented in order to describe gas bubble coalescence, breakage and species transport in the reaction medium and to predict oxygen volumetric mass transfer coefficient (kLa). Model results are verified against experimental data and show good agreement as 13 classes of bubble size is taking into account. Flow behavior in different operational conditions is studied. Almost at all impeller speeds and aeration intensities there were acceptable distributions of species caused by proper mixing. The magnitude of dissolved oxygen percentage in aqueous phase has a direct correlation with impeller speed and any increasing of the aeration magnitude leads to faster saturation in shorter periods of time.

Activated sludge acclimation for toluene and DEHP degradation in a two-phase partitioning bioreactor

The effect of activated sludge acclimation on the biodegradation of toluene in the presence of a biodegradable non-aqueous phase liquid, di (2-ethylhexyl) phthalate (DEHP), in a two-phase partitioning bioreactor was characterized. The influence of the presence of DEHP, at a ratio of 0.1 % (volume ratio), and of the acclimation of activated sludge (AS) on the biodegradation of hydrophobic VOC was studied. AS was acclimated to both toluene and DEHP simultaneously. Using acclimated cells, 73 and 96 % improvement of the mean biodegradation rates was recorded for toluene and the organic solvent (DEHP), respectively, if compared to the values recorded in the absence of acclimation, during tests performed in Erlenmeyer flasks. Degradation rates were further improved by the use of acclimated AS in a reactor with a large head space; degradation yields for toluene and DEHP were above 99 and 89 %, respectively.

Towards a continuous two-phase partitioning bioreactor for xenobiotic removal

The removal of a xenobiotic (4-chlorophenol) from contaminated water was investigated in a simulated continuous two-phase partitioning bioreactor (C-TPPB), fitted with coiled tubing comprised of a specifically-selected extruded polymer, Hytrel 8206. Wastewater flowed inside the tubing, the pollutant diffused through the tubing wall, and was removed in the aqueous bioreactor phase at typical biological removal rates in the C-TTPB simulated by varying aqueous phase throughput to the reactor. Operating over a range of influent substrate concentrations (500–1500mgL−1) and hydraulic retention times in the tubing (4–8h), overall mass transfer coefficients were 1.7–3.5×10−7ms−1, with the highest value corresponding to the highest tubing flow rate. Corresponding mass transfer rates are of the same order as biological removal rates, and thus do not limit the removal process. The C-TPPB showed good performance over all organic and hydraulic loading ranges, with removal efficiencies of 4CP in the tubing wastewater stream always ≥96%. Additionally, the presence of the Hytrel tubing was able to buffer increases in organic loading to the hybrid system, enhancing overall process stability. Biological testing of the C-TPPB confirmed the abiotic test results demonstrating even higher 4-chlorophenol removal efficiency (∼99%) in the tubing stream.