Experimental Study of Biodegradation of Ethanol and Toluene Vapors

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Biomass concentration (g/L), toluene gas outlet (mg/L) 1 0.8 0.6 0.4 0.2 0 biomass toluene, Cgout benzoic acid 45 55 65 75 Time, h 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 Benzoic acid concentration, g/L Figure 4-20. Biodegradation of benzyl alcohol and toluene in a continuous mode (dilution rate of 0.1 h -1 , benzene alcohol feed rate = 0.46 g/h; toluene inlet concentration of 4.5 mg/L) 4.5 Conclusions of Experimental Studies Ethanol and toluene contaminated air streams have been successfully bioremediated in a well-mixed bioreactor. Ethanol was completely absorbed into the growth media, while toluene was absorbed with mass transfer coefficients up to 1.0x10 -3 s -1 . Furthermore, it was observed that toluene was stripped from the fermentation media at rates approximately 1000 times higher than those observed for 78
ethanol. These results clearly indicate the volatile, hydrophobic nature of toluene, relative to that of ethanol. In this study, it was found that unless ethanol or benzyl alcohol was added to the reaction mixture, Pseudomonas putida could not oxidize toluene continuously. This agrees with the results of Gibson et al. (1968). They discovered that the crude cell extracts of Pseudomonas putida that grow on benzyl alcohol contained an active dehydrogenase which permits benzyl alcohol to produce NADH 2 . This reduced NAD is required in the initial reaction of toluene. Appreciable bioremediation rates of both ethanol and toluene from contaminated air streams using a traditional, well-mixed bioreactor were achieved. By operating the bioreactor in a continuous mode, ethanol removal efficiencies reached 100% with inlet loadings up to 304 mg/L-h. Using ethanol as co-substrate, the removal efficiency reached 100% for ethanol and 89% for toluene at ethanol inlet concentration of 15.9 mg/L and toluene inlet concentration of 4.5 mg/L. With the presence of benzyl alcohol as co-substrate at inlet toluene concentrations and total loadings up to 5.7 mg/L and 171 mg/L-h, toluene removal efficiencies were as high as 97 %. A summary of the bioremediation results for ethanol and toluene removal in this study is provided in Table 4-3. These results compare favorably to biofiltration units for the removal of either ethanol or toluene from contaminated air streams, and bode well for commercial implementation since well-mixed bioreactors are much easier to operate than biofilters. 79
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BIOREMEDIATION OF VOLATILE ORGANIC
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ABSTRACT The mass transfer of ethan
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effect on the growth of P. putida.
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ACKNOWLEDGMENT Of the countless peo
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TABLE OF CONTENTS PERMISSION TO USE
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4.3 Batch Growth on Ethanol and Ben
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LIST OF FIGURES Figure 3-1. Schemat
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Figure 5.3 (b) Simulation of ethano
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Figure 5-16. Continuous removal of
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NOMENCLATURE a - Interfacial area,
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CHAPTER ONE - INTRODUCTION 1.1 Air
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esults (van Groenestijn and Hesseli
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experimental results are presented
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Table 2.2 VOC Emissions in the U.S.
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(paint shop effluents, for instance
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combustion provides 70 to 90% air p
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used to degrade ethanol vapours and
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g m -3 . This would suggest that th
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treatment, This excessive biomass f
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The simultaneous degradation of tol
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emoves only water-soluble gases. Wa
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2.2.6 Pseudomonas It is well known
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2.3.2 Growth Models with Inhibition
Page 47 and 48: where µ is the total specific grow
Page 49 and 50: 2.4.1 Batch Reactor In a batch reac
Page 51 and 52: discharged from the other end. The
Page 53 and 54: element solution consisted of (gram
Page 55 and 56: growth on ethanol, 20-48 hours for
Page 57 and 58: Gas phase samples of toluene were c
Page 59 and 60: Inlet sampler Exit sampler To fume
Page 61 and 62: Once the oxygen meter indicated a s
Page 63 and 64: centrifuged and the supernatant was
Page 65 and 66: where k L a is the volumetric mass
Page 67 and 68: Figure 4-2a shows ethanol liquid co
Page 69 and 70: coefficient (k L a) in the well-mix
Page 71 and 72: calculated by dividing the gas volu
Page 73 and 74: Average bubble diameter, mm 8 7 6 5
Page 75 and 76: Bioflow III bioreactor. Equation (4
Page 77 and 78: 3.5 y=Ln(S0/S) 3 2.5 2 1.5 1 y = 12
Page 79 and 80: Ethanol and biomass concentration,
Page 81 and 82: 4.3.2 Batch Growth on Benzyl Alcoho
Page 83 and 84: Biomass and benzyl alcohol concentr
Page 85 and 86: ethanol loading was beyond the maxi
Page 87 and 88: Table 4-2. Comparison of bioremedia
Page 89 and 90: Biomass, benzyl alcohol and toluene
Page 91 and 92: 4.4.3 Toluene-ethanol Bioremediatio
Page 93 and 94: Substrate and biomass concentration
Page 95 and 96: Biomass and benzyl alcohol concentr
Page 97: Biomass and benzoic acid concentrat
Page 101 and 102: CHAPTER FIVE - MATHEMATICAL MODELIN
Page 103 and 104: The stoichiometry of the biomass sy
Page 105 and 106: synthesis and in the ethanol catabo
Page 107 and 108: 1 max Y ex = − 0.635 + 2δ + K 3
Page 109 and 110: Biomass Eq.5-18 Benzyl Alcohol Eq.5
Page 111 and 112: r x r N -1.27 -1 0 1 0 0 -0.2 0 0 2
Page 113 and 114: φ = −θ b ⋅ν (5-31) φ b = 1.
Page 115 and 116: The data sets used to evaluate the
Page 117 and 118: Figures 5.4a and 5.4b present 95% c
Page 119 and 120: Ethanol and biomass concentration (
Page 121 and 122: Ethanol measured (C-mol/L) 0.3 0.25
Page 123 and 124: Figures 5.5 (a-d) demonstrate the s
Page 125 and 126: Benzyl alcohol and biomass concentr
Page 127 and 128: Benzyl alcohol measured (C-mol/L) 0
Page 129 and 130: x = 5 ∑ i= 1 x N i (5-40) where x
Page 131 and 132: ethanol in a steady state mode is l
Page 133 and 134: where ν 1 , ν 2 , ν 3, ν 4 are
Page 135 and 136: Biomass concentration, g/L 1.5 1 0.
Page 137 and 138: φ T =ν 4 (5-53b) φx = −ν 1 (5
Page 139 and 140: In this study, a metabolic model ha
Page 141 and 142: Equations (5-34) and (5-35) and the
Page 143 and 144: ATP 1 = Y max ATP r x + m ATP ⋅ C
Page 145 and 146: Ethanol, biomass and ammonium conce
Page 147 and 148: Figure 5-13a shows that the lower t
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Biomass, substrate concentrations,
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C e DKe = (5-63) μ − D m Equatio
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corresponds with the value associat
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Biomass and ethanol concentrations
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than 4.0 mg/L at all dilution rates
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Biomass, benzyl alcohol and ammonia
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negligible ( y out , e = 0) , and e
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Figure 5-17 shows the results at a
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Biomass Concentrations, g/L 3.5 3 2
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C x ( 1 max Q max = ⋅{ D( Cb0 −
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1.2 g/L, the system could not be op
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The continuous models can capture a
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• Air stripping coefficients obta
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Toluene acts as an inhibitor on the
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Bruining, W. J., G. E. H. Joosten,
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Falatko, D. M., and J. T. Novak, 19
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Keuning, S., and D. Jager, 1994.
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Orshansky, F., and N. Narkis, 1997.
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Togna, A. P, M. Singh, 1994. “Bio
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APPENDIX A. Important Metabolic Pat
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III. Toluene Pathway (Adapted from
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Appendix B. Calibration Procedure a
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Figure B-2. Pseudomonas putida (ATC
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Appendix B-3. Calibration of Chemic
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Appendix B-4. Calibration of Toluen
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Appendix C. Experimental Results: A
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Probe response time, s 12 10 8 6 4
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Appendix C-2. Fed-batch Operation B
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Appendix D: Mathematical Solutions
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The microscopic model allows the fo
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13δ Y o , = 0.585 2 x = (D-24) (8K
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2 σ = −1.3E − 06 (E-11) Y xe Y
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Biomass, ethanol, and acetic acid c
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Experimental Study of Biodegradation of Ethanol and Toluene Vapors

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