| Title | BIODEGRADATION OF PHENOLIC MIXTURES IN A SEQUENCING BATCH REACTOR: A KINETIC STUDY |
| Abstract | Goal, Scope and Background. In this study, attention was focused on substituted phenols because of their widespread presence in industrial effluents originating from many different sources: they are major constituents of wastewater from coal conversion processes, coke ovens, petroleum refineries and petrochemical industries, resin and fibreglass manufacturing and herbicide production. Moreover, for their characteristics of toxicity to humans and aquatic life (1mgl-1 is enough to detect the effects), they are included in the USEPA list of priority pollutants. Toxicity is higher in substituted phenols and is dependent on the nature and numbers of substituent groups. Objective of the present paper is to give a contribution to the modelling of phenolic mixture biodegradation by kinetic studies in which the different compounds are followed separately: this can be easily attained with an experimental apparatus such as the Sequencing Batch Reactor (SBR). Two substituted phenols, 4-nitrophenol (4NP) and 3,4-dimethylphenol (3,4DMP), were utilized as substrates and their degradation kinetics were investigated to evaluate the process parameters both in single compound and in mixture tests.
Methods. Single compound and mixture kinetic tests have been carried out during the reaction phase of the working cycle of the SBR reactor. The single substrates and their mixture were utilized as sole carbon and energy sources. Moreover, in order to verify data reproducibility, all kinetic tests have been carried out in at least two replicates under the same operating conditions.
Results and Discussion. Kinetic data showed the presence of substrate inhibition, to model this experimental evidence the Haldane equation, that is usually employed for substrate inhibited kinetics, was rearranged in a different form with parameters which have a precise meaning in relation to the process kinetics and, at the same time, make the integration procedure easier. The derivation of the equation is shown in an APPENDIX at the end of the paper. Kinetic parameters obtained are suitable for application. It was observed that the 4-nitrophenol removal rate in single compound tests is significantly higher than the 3,4-dimethylphenol removal rate in the whole range of investigated concentrations (up to 80 mg COD l-1). A faster 4-nitrophenol biodegradation was also observed in mixture tests. Moreover, it is worth noting that the two compounds were simultaneously degraded and no diauxic growth was observed. The comparison between single compound and mixture degradation kinetics showed that the 4-nitrophenol degradation rate was comparable in the two cases while a significantly beneficial effect (by increase by about 80% of the maximum removal rate) was detected for 3,4-dimethylphenol degradation in the mixture.
Conclusions. Results of this study showed that the biodegradation kinetics of substituted phenols in mixture can be significantly different from that observed in single compound tests: in fact, the presence of a faster degradable compound (the 4NP) seems to exert a positive effect on the removal of a slower degradable compound (the 3,4DMP). The higher removal rate detected for 4NP, both in single compound and mixture tests, confirmed the key role of the biomass acclimatization in determining the biodegradation kinetics of xenobiotic compounds. The experimental approach and the original method applied for data analysis are of general validity and can be extended to the investigation of different classes of compounds.
Recommendation and Outlook. A relevant aspect related to the process applicability is the demonstrated possibility of easily adapting an enriched culture grown on a specific xenobiotic (in our case the 4NP) for the removal of similar single compounds or in mixtures. When biological process are considered for xenobiotic removal, this suggests a possible strategy of developing enriched cultures on target compounds that can be efficiently utilized on more complex matrices with reduced start up and acclimatization periods. |
| Source | Environmental science and pollution research international 15, pp. 188–195 |
| Keywords | phenolic mixturesbiodegradation kineticsHaldane equation |
| Journal | Environmental science and pollution research international |
| Editor | Springer, Berlin, Germania |
| Year | 2008 |
| Type | Articolo in rivista |
| DOI | 10.1065/espr2007.12.470 |
| Authors | TOMEI M.C. (1); ANNESINI M.C. (2) |
| Text | 42198 2008 10.1065/espr2007.12.470 ISI Web of Science WOS 000256187500004 phenolic mixtures biodegradation kinetics Haldane equation BIODEGRADATION OF PHENOLIC MIXTURES IN A SEQUENCING BATCH REACTOR A KINETIC STUDY TOMEI M.C. 1 ; ANNESINI M.C. 2 1 Water Research Institute, C.N.R., Via Reno 1, 00198 Rome, Italy; 2 Chemical Engineering Department, La Sapienza University of Rome, Via Eudossiana 18, 00184 Rome, Italy Goal, Scope and Background. In this study, attention was focused on substituted phenols because of their widespread presence in industrial effluents originating from many different sources they are major constituents of wastewater from coal conversion processes, coke ovens, petroleum refineries and petrochemical industries, resin and fibreglass manufacturing and herbicide production. Moreover, for their characteristics of toxicity to humans and aquatic life 1mgl 1 is enough to detect the effects , they are included in the USEPA list of priority pollutants. Toxicity is higher in substituted phenols and is dependent on the nature and numbers of substituent groups. Objective of the present paper is to give a contribution to the modelling of phenolic mixture biodegradation by kinetic studies in which the different compounds are followed separately this can be easily attained with an experimental apparatus such as the Sequencing Batch Reactor SBR . Two substituted phenols, 4 nitrophenol 4NP and 3,4 dimethylphenol 3,4DMP , were utilized as substrates and their degradation kinetics were investigated to evaluate the process parameters both in single compound and in mixture tests. Methods. Single compound and mixture kinetic tests have been carried out during the reaction phase of the working cycle of the SBR reactor. The single substrates and their mixture were utilized as sole carbon and energy sources. Moreover, in order to verify data reproducibility, all kinetic tests have been carried out in at least two replicates under the same operating conditions. Results and Discussion. Kinetic data showed the presence of substrate inhibition, to model this experimental evidence the Haldane equation, that is usually employed for substrate inhibited kinetics, was rearranged in a different form with parameters which have a precise meaning in relation to the process kinetics and, at the same time, make the integration procedure easier. The derivation of the equation is shown in an APPENDIX at the end of the paper. Kinetic parameters obtained are suitable for application. It was observed that the 4 nitrophenol removal rate in single compound tests is significantly higher than the 3,4 dimethylphenol removal rate in the whole range of investigated concentrations up to 80 mg COD l 1 . A faster 4 nitrophenol biodegradation was also observed in mixture tests. Moreover, it is worth noting that the two compounds were simultaneously degraded and no diauxic growth was observed. The comparison between single compound and mixture degradation kinetics showed that the 4 nitrophenol degradation rate was comparable in the two cases while a significantly beneficial effect by increase by about 80% of the maximum removal rate was detected for 3,4 dimethylphenol degradation in the mixture. Conclusions. Results of this study showed that the biodegradation kinetics of substituted phenols in mixture can be significantly different from that observed in single compound tests in fact, the presence of a faster degradable compound the 4NP seems to exert a positive effect on the removal of a slower degradable compound the 3,4DMP . The higher removal rate detected for 4NP, both in single compound and mixture tests, confirmed the key role of the biomass acclimatization in determining the biodegradation kinetics of xenobiotic compounds. The experimental approach and the original method applied for data analysis are of general validity and can be extended to the investigation of different classes of compounds. Recommendation and Outlook. A relevant aspect related to the process applicability is the demonstrated possibility of easily adapting an enriched culture grown on a specific xenobiotic in our case the 4NP for the removal of similar single compounds or in mixtures. When biological process are considered for xenobiotic removal, this suggests a possible strategy of developing enriched cultures on target compounds that can be efficiently utilized on more complex matrices with reduced start up and acclimatization periods. 15 http //www.springerlink.com/content/270g3551l13p3860/ Articolo pubblicato su rivista ISI fulltext 0.pdf Articolo in rivista Springer 0944 1344 Environmental science and pollution research international Environmental science and pollution research international Environ. sci. pollut. res. int. Environmental science and pollution research international. Environmental science and pollution research international Print Environmental science and pollution research Print ESPR Print mariaconcetta.tomei TOMEI MARIA CONCETTA TA.P07.001.001 Sviluppo di tecnologie depurative a regime non stazionario |
