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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, P ps , 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  cm 2  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 (R 2  > 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 g 4NP kg ds -1 vs. 1.69 g 4NP kg ds -1 obtained with single extraction unit, for a soil contaminated with 10 g 4NP kg ds -1 . Corresponding extraction efficiencies were 96 and 83%, respectively., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

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% COD Dye removal., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Solid phase extraction performed with commercial polymer beads to treat soil contaminated by chlorophenols (4-chlorophenol, 2,4-dichlorophenol and pentachlorophenol) as single compounds and in a mixture has been investigated in this study. Soil-water-polymer partition tests were conducted to determine the relative affinities of single compounds in soil-water and polymer-water pairs. Subsequent soil extraction tests were performed with Hytrel 8206, the polymer showing the highest affinity for the tested chlorophenols. Factors that were examined were polymer type, moisture content, and contamination level. Increased moisture content (up to 100%) improved the extraction efficiency for all three compounds. Extraction tests at this upper level of moisture content showed removal efficiencies ≥70% for all the compounds and their ternary mixture, for 24 h of contact time, which is in contrast to the weeks and months, normally required for conventional ex situ remediation processes. A dynamic model characterizing the rate and extent of decontamination was also formulated, calibrated and validated with the experimental data. The proposed model, based on the simplified approach of "lumped parameters" for the mass transfer coefficients, provided very good predictions of the experimental data for the absorptive removal of contaminants from soil at different individual solute levels. Parameters evaluated from calibration by fitting of single compound data, have been successfully applied to predict mixture data, with differences between experimental and predicted data in all cases being ≤3%., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The present study has provided a comparison between a conventional ex situ method for the treatment of contaminated soil, a soil slurry bioreactor, with a novel technology in which a contaminant is rapidly and effectively removed from the soil by means of absorptive polymer beads, which are then added to a two-phase partitioning bioreactor (TPPB) for biodegradation of the target molecule. 4-nitrophenol (4NP) was selected as a model contaminant, being representative of a large class of xenobiotics, and the DuPont thermoplastic Hytrel™ 8206 was utilized for its extraction from soil over ranges of soil contamination level, soil moisture content, and polymer:soil ratios. Since the polymers were able to rapidly (up to 77% and 85% in 4 and 24h respectively) and selectively remove the contaminant, the soil retained its nutrient and microflora content, which is in contrast to soil washing which can remove these valuable soil resources. After 4h of reaction time, the TPPB system demonstrated removal efficiency four times higher (77% vs 20%) than the slurry system, with expected concomitant savings in time and energy. A volumetric removal rate of 75 mg4NPh(-1) L(-1) was obtained in the TPPB, significantly greater than the value of 1.7 obtained in the slurry bioreactor. The polymers were readily regenerated for subsequent reuse, demonstrating the versatility of the polymer-based soil treatment technology., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Used automobile tire pieces were tested for their suitability as the sequestering phase in a two-phase partitioning bioreactor to treat 2,4-dichlorophenol (DCP). Abiotic sorption tests and equilibrium partitioning tests confirmed that tire "crumble" possesses very favourable properties for this application with DCP diffusivity (4.8 × 10(-8) cm(2)/s) and partition coefficient (31) values comparable to those of commercially available polymers. Biodegradation tests further validated the effectiveness of using waste tires to detoxify a DCP solution, and allow for enhanced biodegradation compared to conventional single-phase operation. These results establish the potential of using a low-cost waste material to assist in the bioremediation of a toxic aqueous contaminant.

Significant improvement in biodegradation performance has been demonstrated arising from the reduction of cytotoxicity provided by the sequestering of 4-nitrophenol (4NP) within Hytrel polymer beads added to a two-phase partitioning bioreactor (TPPB) operating in sequencing batch reactor (SBR) mode. This reduced toxicity is particularly apparent as the feed substrate concentration is increased; in fact it was shown that at a feed of 1000 mg/L 4NP, the inhibitory effect of the substrate completely prevents degradation from occurring in a single-phase system, whereas at only a 5% polymer loading, rapid and compete biodegradation is achieved. Different polymer/aqueous phase ratios were used to detoxify varying feed concentrations, and degradation rates were enhanced through the use of increased polymer loadings. As demonstrated in oxygen uptake experiments, the addition of polymers also reduces the maximum demand for oxygen, relative to single-phase operation, and smoothes the demand for oxygen throughout the degradation process. Polymer regeneration has also been further characterized by quantifying the number of methanol washes required to achieve satisfactory 4NP residuals, and the addition of a small amount of cosolvent has been shown to dramatically increase the rate of bioregeneration to produce beads ready for reuse.

The present study has demonstrated the enhanced performance of a two-phase bioreactor, operating with polymers as a partitioning phase, as an alternative to both single phase biotreatment and to the use of an immiscible organic solvent partitioning phase, to deliver a toxic substrate (4-nitrophenol, or 4NP) to a microbial consortium in batch and repeated batch mode. Three commercial polymers were tested, Hytrel, Tone, and Elvax, and were shown to have superior properties related to the use of a consortium, including complete biocompatibility with the biomass and nonbiodegradability. Repeated kinetic tests performed with short reaction times demonstrated the accumulation of 4NP within the polymers in the range of 6-8 mg/g polymer, which reduced polymer performance in subsequent batch operations. Hytrel gave the best performance with residuals of up to 4 mg/g polymer showing no reduction in subsequent use, while for the other polymers a 4NP value lower than 2 mg/g polymer was required to have acceptable performance during repeated polymer use. Polymer reuse without affecting the process efficiency was confirmed with regeneration tests. A conventional methanol extraction method, as well as biological regeneration of the polymers by prolonged contact with the biomass, were assessed for their ability to remove the residual 4NP. Parallel kinetic tests performed with newand regenerated polymers showed a complete overlap of the 4NP concentration profiles indicating that a simple biological regeneration method provides a means of completely restoring polymer performance for repeated batch operation.

BACKGROUND An innovative approach for ex situ soil bioremediation, based on absorptive polymers extraction combined with biological regeneration of the polymer in a two-phase partitioning bioreactor ( TPPB), was tested to remediate soil contaminated by chlorophenols. The objective of the study was to evaluate the performance of the proposed technology in comparison with conventional technologies, such as slurry bioreactors and solid-phase bioreactors. RESULTS A soil highly contaminated (∼4 g kg−1 for each compound) by a mixture of 4-chlorophenol ( 4CP) and pentachlorophenol ( PCP), was treated with different bioremediation systems. Removal efficiencies achieved with polymer extraction were >70% for a contact time of 24 h; the contaminated polymer was then regenerated in a TPPB (∼100 and 85% biodegradation efficiencies for 4CP and PCP, respectively). No degradation of PCP occurred in conventional bioreactors, while, for 4CP, 40 days were required for its biodegradation in the slurry bioreactor, and 80 days to reach 67% removal in the solid-phase bioreactor. CONCLUSION Advantages of the two-step polymer-based soil treatment in comparison with conventional technologies have been demonstrated for chlorophenols contaminated soils: efficiencies in the range 70-80% for soil decontamination and almost complete mineralization of the two compounds were achieved with reaction times suitable for application (<20 days). © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In this study we evaluated the feasibility of two regeneration strategies of contaminated polymers employed for ex-situ soil remediation in a two-step process. Soil decontamination is achieved by sorption of the pollutants on the polymer beads, which are regenerated in a subsequent step. Tested soil was contaminated with a mixture of 4-chlorophenol and pentachlorophenol, and a commercial polymer, Hytrel, has been employed for extraction. Removal efficiencies of the polymer-soil extraction are in the range of 51–97% for a contact time ≤ 24 h. Two polymer regeneration strategies, solvent extraction and biological regeneration (realized in a two-phase partitioning bioreactor), were tested and compared. Performance was assessed in terms of removal rates and efficiencies and an economic analysis based on the operating costs has been performed. Results demonstrated the feasibility of both regeneration strategies, but the bioregeneration was advantageous in that provided the biodegradation of the contaminants desorbed from the polymer. Practically complete removal for 4-chlorophenol and up to 85% biodegradation efficiency for pentachlorophenol were achieved. Instead, in the solvent extraction, a relevant production (184–831 L kg pol −1 ) of a highly polluted stream to be treated or disposed of is observed. The cost analysis of the two strategies showed that the bioregeneration is much more convenient with operating costs of ∼12 €/kg pol i.e. more than one order of magnitude lower in comparison to ∼233 €/kg pol of the solvent extraction. [ABSTRACT FROM AUTHOR]

Abstract: Finding new uses for waste or discarded material is an important environmental goal; being able to use a waste material to treat another waste is an even more attractive objective, and this was the purpose of the present work. We previously showed that used automobile tires have an affinity for a toxic contaminant, dichlorophenol (DCP), absorbing and releasing it based on concentration driving forces. Here we have exploited this phenomenon by using used tires as the sequestering phase in a Two-Phase Partitioning Bioreactor (TPPB) to treat otherwise-toxic levels of DCP, far out-performing single phase operation in a sequencing batch bioreactor. A comprehensive examination of substrate loading, reactor exchange ratio, and tire fraction used, demonstrated that the tire-TPPB system could handle a 40% higher influent substrate loading and an increase of the exchange ratio value from 0.5 (prohibitive for single phase operation) to 0.7. Such improvement was obtained with a tire fraction ≤9%, comparable to that for commercial polymers previously employed in TPPBs. This study has opened the door to the identification of other waste plastics suitable for use in TPPBs for the treatment of recalcitrant organic contaminants. [Copyright &y& Elsevier]

Abstract: The biological treatment of phenolics is constrained by the inherent cytotoxicity of these compounds. One method to alleviate such toxicity is to add a sequestering phase to absorb, and subsequently release, the substrate(s) to the micro-organisms; such a system is termed a Two Phase Partitioning Bioreactor. Here we have compared the performance of a TPPB, relative to single phase operation, in which a small volume (5%, v/v) of beads of the polymer Hytrel 8206 was used to treat aqueous mixtures of 2,4-dimethylphenol and 4-nitrophenol. Hytrel 8206 was selected from a range of polymers that were tested for their partition coefficients (PCs) for the target molecules, with the more hydrophobic compound (2,4-dimethylphenol) having a higher PC value (201) than 4-nitrophenol (143). Significantly increased removal rates for both substrates were demonstrated in TPPB mode relative to single phase operation. Additionally, the differential release of the compounds to the aqueous phase and their distinct PC values changed the kinetic pattern of the biotreatment system, smoothing out the cellular oxygen demand. Release of the substrates by the polymer over 60 operating cycles was virtually complete (>97%) demonstrating the reusability and robustness of the use of polymers in overcoming cytotoxicity of phenolic substrates. [Copyright &y& Elsevier]

The biodegradation of pentachlorophenol (PCP), the most toxic among chlorophenols, was extensively investigated in solid-liquid two-phase bioreactors (according to Box-Behnken experimental design) to demonstrate the feasibility of this technological platform. Process performance optimization for the subsequent scale up was also performed. The process was catalysed by an acclimated microbial consortium and the partitioning phase consisted of Hytrel 8206 polymer. The virtuous combination of polymer uptake/release and microbial biodegradation allowed achieving practically complete biodegradation efficiencies and rates in the range of 4.0-7.8mg/(L h) for PCP concentrations up to lOOmg/L far above those previously tested. Detected biodegradation rates are one order of magnitude higher than the ones reported for suspended biomass reactors. A regression model based on 3 independent variables (initial PCP and biomass concentration and polymer-to-water ratio) was formulated to predict the volumetric biodegradation rate. The significance of independent variables and their interactions was tested by the analysis of variance (ANOVA) with 95% confidence limit. The model resulted adequate and the polymerto-water ratio was identified as the most significant factor affecting the system response. Maximization of the biodegradation rate has been achieved for PCP concentration of lOOmg/L, biomass concentration of 1 gVSS/L and polymer-to-water ratio of 9%. [ABSTRACT FROM AUTHOR]