Contributions of CINVESTAV to the study of bioreactors with simultaneous electron acceptors
Removal of Trichlorophenol under partially-aerated methanogenic using a Fluidized Bed bioreactor
Removal of Perchloroethylene in partially-aerated methanogenic regime using a Fluidized Bed bioreactor
Removal of Perchloroethylene under M-D conditions
M-A and M-D bioreactors coupled to zero valent iron for PCE degradation
Removal of perchloroethylene in two methanogenic-denitrifying continuous systems Héctor M. Poggi-Varaldo CINVESTAV-IPN, Dept. Biotechnology and Bioengineering, Environmental Biotechnology R&D Group, México
PCE is recalcitranr (not biodegradable) in aerobic conditions (Vogel and McCarty 1985) . Its biological transformation is generally carried out in anaerobic environments (van Eekert, 1999).
Previous works on biological treament and bioremediation of PCE have used anaerobic consortia that mediated the sequential reductive dehalogenation of PCE, presumably by cometabolism (Vogel y McCarty, 1985; Prakash y Gupta, 2000; Cope et al., 2001; López-Navarrete et al., 2003).
In most of these studies, accumulation of dichloroethylene (DCE) and vinyl chloride (VC) has been observed. A few works have been able to show the full transformation of PCE to ethene, after a long enrichment of anoxic consortia or using pure cultures of dehalorespiring bacteria (Mayor et al., 2002).
Series reactors and Simultaneous Electron Acceptor (SEA) systems
High chlorine content Penta-, tetra-, tri- Anaerobic Low chlorine content di-, and monochloro- Aerobic A good alternative: Series Reactors Brief example with a chlorinated organic compound Accumulation of
Series Reactors Anaerobic Reactor Reactor with second electron acceptor Tetrechloroethene TCE, DCE, VC Further removal of chlorinated aliphatics Garibay Orijel et al . (2005a) J. Chem. Technol. Biotechnol . In press Campos-Velarde et al . (1997). Battelle Press. What’s the problem with series reactors? 2 Reactors Costs X 2 Better try Simultaneous Electron Acceptors in One reactor Salto a la albóndiga
Protection via diffusion barrier in biofilm CH 4 CO 2 NO 3 - + org. matter N 2 +H 2 O Anaerobic zone Denitriying zone Liqued dif- fusion leayer Denitrifying microorganisms Methanogens Bulk liquid (adapted from López-Navarrete, 2002). Pollutant NO 3 - Concentration Carrier
to evaluate and compare de performance of a fluidized bed bioreactor (FBBR) and complete mix reactors (CM) with suspended biomass, all of them fed with PCE as model chlorinated aliphatic and a low-moderate concentration of degradable organic matter as methanol
to assess the influence of the biochemical regime (full methanogenic versus M-D), and the effect of in the M-D regime (18 and 9) on performance
Reactor setup: A Anaerobic Fluidized Bed Bioreactor (AFBBR); B Complete Mix Bioreactor (CM). 1A fluidized bed of bioparticles; 2A reservoir and feed of influent with a partial content of methanol; 2´A feed of stock of PCE in methanol; 3A recirculation; 4A liquid trap; 5A effluent reservoir; 6A biogas exit; 7A biogas sampling port; 8A activated carbon trap; 9A biogas measurement by brine meters; 1B suspended biomass; 2B reservoir and feed of influent with a partial content of methanol; 2´B feed of stock of PCE in methanol; 3B effluent reservoir; 4B biogas exit; 5B biogas sampling port; 6B activated carbon trap; 7B biogas sampling port.
1000 mg COD-methanol/L in all periods; PCE: Perchloroethylene. a Anaerobic fluidized bed bioreactor at HRT= 1d, Vop= 2.8L, 35°C; b,c Complete mix reactor at HRT= 15 d, Vop= 2.5L, 35°C.; d Volumetric loading rate of organic matter in gCOD/(L.d), e Volumetric loading rate of PCE in mg PCE/(L.d); f Concentration of PCE in the influent, in mg/L; g Relation of volumetric loading and Nitrogen contend in Nitrate.
Operating conditions of bioreactors in the different periods of the experimental design Period 1 Period 2 Period 3 40
Average performance of reactors 2/2 Metabolites and dechlorination efficiencies
Poggi’s discrete divergence index n’ A = only green n’ B = only yellow n A = green plus white n B = yellow plus white Microbial community A Microbial community B Zárate-Segura et al. (2005). Battelle
Poggi’s discrete divergence index and dynamic divergence coefficient
Lanes 1 and 2, methanogenic period with no PCE; Lanes 3 to 5, methanogenic period with 20 mg/L PCE; Lanes 6 to 8 methanogenic period with 40 mg/L PCE. All lanes contain 5 g of 16S rDNA PCR product. Poliacrylamide gel at 8% (Acrylamide/N-N´methylenbisacrylamide 37.5:1) Buffer TBE 1X, Urea -Formamide 10-50% (8M of Urea and 40%v/v formamide equivalent to 100% denaturing agents); 30 V, 13-15 mA, 8 h, 60°C. DGGE profiles of major bacterial communities present in fluidized bed bioreactor
Variation of bacterial communities in methanogenic FBBR and CM reactors in a period of operation with no PCE in the influent: Diagonal: comparison between start and end of the period for a given bioreactor Other cells: comparison between bioreactors
Variation of bacterial communities in methanogenic FBBR and CM reactors in a period of operation with 40 mg PCE/L for FBBR and CM2 and 20 mg PCE/L in CM1: Diagonal: comparison between start and end of the period for a given bioreactor Other cells: comparison between bioreactors
Variation of bacterial communities in methanogenic FBBR and CM reactors between periods with no PCE and with PCE in the feed: Diagonal: comparison between periods for a given bioreactor Other cells: empty
Ref.: 1. Juteau, P., Tremblay, D., Villemur, R., Bisaillon, J.-G. and Beaudet R. (2004). Analysis of the bacterial community inhabiting an aerobic thermophilic sequencing batch reactor (AT-SBR) treating swine waste. Appl. Microbiol. Biotechnol . 66, 115-122. 2. Ghosh, S. and LaPara, T.M. (2004). Removal of carbonaceous and nitrogenous pollutants from a synthetic wastewater using a membrane-coupled bioreactor. J. Industrial Microbiol. Biotechnol . 31, 353 –361. 3. Tartakovsky, B., Manuel, M.F., Beaumier, D., Greer, C.W. and Guiot, S.R. (2001). Enhanced selection of an anaerobic pentachlorophenol-degrading consortium. Biotechnol. Bioeng . 73, 476-483. Dynamic divergence indices of bacterial communities of several bioreactors
- In Period 1 , methanogenic regime, AFBBR showed the best performance of the three reactors with higher values of both organic matter removal and PCE, in spite that volumetric loadings on AFBBR were 15-fold higher and some process stress would have been expected.
- During Period 2 , simultaneous M-D regime at =18 gCOD/gN-NO 3 - , an improvement in performance of CM2 was observed. The other two reactors displayed similar performances than the corresponding in Period 1 .
-In Period 3 , simultaneous M-D regime at = 9 gCOD/gN-NO 3 - , and concerning the two reactors fed with the highest PCE concentration 40 mg/L (FBBR and CM2), the FBBR outperformed CM2 in almost all the performance parameters and its metabolite profile was better than both of CM2 and CM1 (lower TCE, DCE, and VC in the effluent).
This pattern, along with highest dechlorination efficiency of FBBR strongly suggests that FBBR under M-D conditions may provide a more integral treatment to wastewaters polluted with significant concentrations of PCE.
The bacterial communities in the CMs were richer than those of FBBR during three operations periods
Generally, bacterial profiles in each reactor varied with time in a given period of operation. There was a relative higher stability of consortium in the FBBR as displayed by the lowest dynamic divergence coefficients values
The above described pattern was accompanied by a better biochemical peformance of FBBR (stable methanogenesis, high removal of PCE and lower concentrations of intermediate chlorinated aliphatics)