| Title | Re-use of automobile tires as the sequestering phase in a solid-liquid partitioning bioreactor for the biodegradation of inhibitory compounds, |
| Abstract | Two phase partitioning bioreactors (TPPBs) have proved to be effective in reducing toxicity arising from high xenobiotic concentrations in biodegradation processes. The strategy utilized in TPPBs involves the use of an immiscible second phase (liquid solvent or polymer) within the bioreactor, whose function is to sequester, and gradually deliver, toxic substrate molecules to the microorganisms. In this way the microenvironment of cells is favourably influenced by the controlled partitioning of xenobiotic substrates resulting in significantly enhanced biotreatment performance. In the bioremediation of contaminated water and soils where mixed cultures are necessarily utilized, the use of polymers as the sequestering phase is extremely advantageous as polymers are completely biocompatible and inert with respect to the microbial biomass. A new opportunity for this technology in terms of environmental sustainability is to utilize waste polymeric materials as the partitioning phase. Waste polymers, in the form of automobile tires, provide an opportunity for not only reducing the initial polymer cost to near-zero, but also for utilizing a waste material for positive environmental purposes. Scrap automobile and truck tires are generated in very large quantities, on a continuous basis; for example, the estimate of used tires generated in Europe is 3.21·106 tonnes per year (European Tyre & Rubber Manufacturers' Association, http://www.etrma.org/tyres/ELTs) and in the US 2.97·106 tonnes per year (data of 2003 from US EPA http://www.epa.gov/osw/conserve/materials/tires/faq.htm). In this paper waste tires in small pieces (3-4 mm) were utilized as the sorption phase in a TPPB for the degradation of two substituted phenols 2,4 dichlorophenol (DCP) and 4-nitrophenol (4NP). These target compounds have been chosen as they are extensively used in the chemical industry (i.e. production of pesticides and herbicides) and are found in many industrial effluents. Both compounds are toxic, being characterized by EC50 values of 2.4 -40 mg/L and 64 mg/L for DCP and 4NP, respectively. The objectives of this work were to demonstrate the possibility of usefully employing and recycling a waste polymer as the partitioning phase in a TPPB, and, at the same time, to define suitable operating strategies to achieve high removal efficiencies with kinetics suitable for larger-scale treatment of the tested phenolic compounds. Sorption tests for DCP and 4NP were first performed to verify the related uptake rates. A mixed culture acclimatized to the two phenolic compounds over a 3 month period was then utilized in biodegradation tests in the TPPB reactor operated in semi-continuous mode. Biodegradation kinetics was investigated for DCP in single compound tests and for the binary mixture DCP-4NP. Experimental results demonstrate that the tires had a higher affinity for DCP, which is more toxic relative to 4NP. In single compound tests a significant reduction in DCP toxicity, and a concomitant enhancement in substrate removal efficiency (92%) is clearly seen for the TPPB case, with practically negligible biodegradation in the conventional single phase reactor. Finally, for the mixture we verified that the single phase system was not able to appreciably remove the DCP at a feed concentration of 150 mg/L for both compounds while a significant improvement is obtained in the TPPB operated with 10% v/v tires. |
| Source | ICRM 2014 Third International Conference on Recycling and Reuse of Materials, Kottayam, Kerala, India, 11 - 13/04/ 2014 |
| Keywords | used tirestwo-phase partitioning bioreactorsxenobiotic removal |
| Year | 2014 |
| Type | Contributo in atti di convegno |
| Authors | M. Concetta Tomei, Andrew J. Daugulis |
| Text | 372247 2014 used tires two phase partitioning bioreactors xenobiotic removal Re use of automobile tires as the sequestering phase in a solid liquid partitioning bioreactor for the biodegradation of inhibitory compounds, M. Concetta Tomei, Andrew J. Daugulis Water Research Institute, C.N.R., Via Salaria km 29,300 C.P. 10, 00015 Monterotondo Stazione Rome , Italy Department of Chemical Engineering, Queen s University Kingston Canada K7L 3N6 Two phase partitioning bioreactors TPPBs have proved to be effective in reducing toxicity arising from high xenobiotic concentrations in biodegradation processes. The strategy utilized in TPPBs involves the use of an immiscible second phase liquid solvent or polymer within the bioreactor, whose function is to sequester, and gradually deliver, toxic substrate molecules to the microorganisms. In this way the microenvironment of cells is favourably influenced by the controlled partitioning of xenobiotic substrates resulting in significantly enhanced biotreatment performance. In the bioremediation of contaminated water and soils where mixed cultures are necessarily utilized, the use of polymers as the sequestering phase is extremely advantageous as polymers are completely biocompatible and inert with respect to the microbial biomass. A new opportunity for this technology in terms of environmental sustainability is to utilize waste polymeric materials as the partitioning phase. Waste polymers, in the form of automobile tires, provide an opportunity for not only reducing the initial polymer cost to near zero, but also for utilizing a waste material for positive environmental purposes. Scrap automobile and truck tires are generated in very large quantities, on a continuous basis; for example, the estimate of used tires generated in Europe is 3.21·106 tonnes per year European Tyre Rubber Manufacturers Association, http //www.etrma.org/tyres/ELTs and in the US 2.97·106 tonnes per year data of 2003 from US EPA http //www.epa.gov/osw/conserve/materials/tires/faq.htm . In this paper waste tires in small pieces 3 4 mm were utilized as the sorption phase in a TPPB for the degradation of two substituted phenols 2,4 dichlorophenol DCP and 4 nitrophenol 4NP . These target compounds have been chosen as they are extensively used in the chemical industry i.e. production of pesticides and herbicides and are found in many industrial effluents. Both compounds are toxic, being characterized by EC50 values of 2.4 40 mg/L and 64 mg/L for DCP and 4NP, respectively. The objectives of this work were to demonstrate the possibility of usefully employing and recycling a waste polymer as the partitioning phase in a TPPB, and, at the same time, to define suitable operating strategies to achieve high removal efficiencies with kinetics suitable for larger scale treatment of the tested phenolic compounds. Sorption tests for DCP and 4NP were first performed to verify the related uptake rates. A mixed culture acclimatized to the two phenolic compounds over a 3 month period was then utilized in biodegradation tests in the TPPB reactor operated in semi continuous mode. Biodegradation kinetics was investigated for DCP in single compound tests and for the binary mixture DCP 4NP. Experimental results demonstrate that the tires had a higher affinity for DCP, which is more toxic relative to 4NP. In single compound tests a significant reduction in DCP toxicity, and a concomitant enhancement in substrate removal efficiency 92% is clearly seen for the TPPB case, with practically negligible biodegradation in the conventional single phase reactor. Finally, for the mixture we verified that the single phase system was not able to appreciably remove the DCP at a feed concentration of 150 mg/L for both compounds while a significant improvement is obtained in the TPPB operated with 10% v/v tires. Published version ICRM 2014 Third International Conference on Recycling and Reuse of Materials Kottayam, Kerala, India 11 13/04/ 2014 Internazionale Su invito Contributo in atti di convegno mariaconcetta.tomei TOMEI MARIA CONCETTA TA.P07.002.005 Rimozione di composti xenobiotici da acque di scarico |
