Modeling of sorption, degradation and transport of bacteria and organic contaminant in saturated quartz sand

다국어 초록 (Multilingual Abstract)

Various reaction processes related to the fate of contaminant in the underground system are studied using modeling approach. First of all, sorption of organic contaminant on solid material was investigated. New method for determination of parameters for the equilibrium/kinetic sorption of organic contaminant was developed using analytical solution of two-site sorption model (TSPI) which assumes to occur fast sorption contaminant on type-1 site and slow rate-limiting sorption on type-2 site. Applying the new method to the experimental data, more parameters could be obtained than applying the solution of the existing three-stage sorption model. The two-site sorption model (TSPI) was compared with another type of two-site model (TSSI) which assumes that the slow rate limiting sorption occurs between Type-1 site and Type-2 site. Application of these two models to a batch system resulted in an identical type of C–t relationship. Model parameters such as distribution coefficient and retardation factor estimated by fitting the analytical solutions of the C–t relationship to the kinetic sorption data well coincided. However, due to differences in the definition of liquid concentration (C+0) at t = +0, some of the parameters deviated from each other. Therefore, care should be taken in the selection of the first-order sorption kinetics of the two site model when modeling reactive solute transport in a porous medium, since the fraction is closely related to the retardation phenomenon.
The bacterial sorption on solid matrix was also investigated especially on the effect of the variation of ionic strength. Effect of the perturbation of ionic strength on attachment of bacteria was investigated by imposing various leaching solutions with different ionic strengths after bacterial pulse in the column tests. By monitoring ionic strength of the effluent solution, effect of ionic strength on the dynamic bacterial attachment/detachment during transport was clearly shown. Results have shown that bacterial attachment could be categorized by two main mechanisms. One is the physical factor such as deposition caused by the interaction between sand surface and bacteria, and the second is chemical factor such as attachment onto quartz sand by DLVO interaction. The chemical attachment could be divided into the reversible fraction in secondary energy minimum and irreversible fraction in primary energy minimum by replacing leaching solution with that of lower ionic strength. The interaction energy between bacteria and sand surface calculated by classical DLVO model explains (1) that the chemical deposition in MSM condition was occurred in the primary energy minimum, (2) that the reversibility of the bacterial attachment is due to the separation of the secondary minimum from the primary minimum by lowering ionic strength, (3) and that part of the cells could be retained in the primary minimum in spite of leaching with low ionic strength solution.
Bacterial BTC test performed under low, high and perturbed ionic strength condition of leaching solution showed different degree of retardation, attenuation and tailing. These phenomena support the effect of ionic strength on bacterial sorption process. The sorption type of bacteria during transport through sand column was described with eight different types of sorption. The results showed that equilibrium, kinetic reversible and kinetic irreversible sorption processes were occurred in all conditions. Thus, transport model including all the three sorption type is the most appropriate. Depending on the given condition of ionic strength, the contributions of each process were different. Under low ionic strength condition, kinetic reversible and irreversible process had large contribution while equilibrium process had insignificant contribution. Under high ionic strength condition, the three processes contributed significantly. Under perturbed ionic strength condition, kinetic reversible process contributed dominantly and the others had small contribution. Therefore, care should be taken for selection of an appropriate bacterial transport model with regard to sorption types when modeling under various conditions of particle, bacteria, and leaching solution interactions.
In the presence of bacteria, the fate of contaminant is affected by more complex processes. To describe the fate of contaminant and bacteria, a model of bacteria associated transport for toluene was developed by accounting for kinetic reactions for biosorption and biodegradation as well as sorption on solid material. This model assumes fully kinetic processes for sorption, biosorption and degradation of contaminant, sorption, growth and decay of bacteria. The developed model could explain the attenuation and significant tailing of toluene BTC in the presence of bacteria reported by Chung et al.(2011). Analysis for the composition of the effluent solution exhibited that the microbial activity during the transport of toluene in the presence of bacteria was related to the processes of biodegradation and biosorption. The mass loss of toluene was mostly attributed by sorption process and followed by the biodegradation. The tailing of the BTC of toluene was attributed to the sorption of toluene onto bacterial cells and the retarded transport of bacteria.
At last, I proposed a new method for estimation of the first-order degradation rate coefficient q which is essential for determination of the first-order degradation kinetics q-S relation. The new method is based on the time segment method (TSM) where several q values are calculated from the q-S data for each measured time step. The q-S relation obtained from the TSM was compared with that obtained from straight-line method (SLM) where q is calculated from the slope of ln(S/S0) vs. time data. Three different inhibitory kinetic models (Haldane, Yano, Edward) were applied to the q-S relation for parameter estimation. TSM offered a better prediction of phenol degradation than SLM, and Edward model gave the best results compared to other models.

목차 (Table of Contents)

• 1 General introduction 1
• 1.1 Background 1
• 1.2 Objectives 4
• 2 New method for determination of equilibrium/kinetic sorption parameters 11
• 2.1 Introduction 12
• 2.2 Analytical solution of reversible two-site sorption kinetics 16
• 2.3 Kinetics adsorption experiments 17
• 2.4 Estimation of kinetic parameters 19
• 2.5 Conclusions 21
• 3 Comparison of first-order sorption kinetics using concept of two-site sorption model 24
• 3.1 Introduction 25
• 3.2 Comparison of Ct relationship 26
• 3.2.1 TSSI model 26
• 3.2.2 TSPI model 30
• 3.3 Comparison of analytical solutions 31
• 3.3.1 Solution of TSSI model 31
• 3.3.2 Solution of TSPI model 32
• 3.4 Estimation of model parameters and transport modeling 34
• 3.5 Comparison of model parameters and BTCs 38
• 3.6 Conclusion 41
• 4 Bacterial attachment and detachment during transport affected by variation of ionic strength after pulse injection 44
• 4.1 Introduction 45
• 4.2 Material and methods 47
• 4.2.1 Organisms and culture preparation 47
• 4.2.2 Porous media 48
• 4.2.3 Particle size and surface potential analysis 48
• 4.2.4 Column tests 49
• 4.2.5 Surface interaction energy 53
• 4.3 Results and Discussion 55
• 4.3.1 Effect of leaching solution type on bacterial transport 55
• 4.3.2 Effect of ionic strength on bacterial transport 59
• 4.3.3 Contributions of physical and chemical attachment 61
• 4.3.4 Interaction energy by classical DLVO model 63
• 4.3.5 Reversibility of cell attachment 64
• 4.3.6 Relationship of bacterial stability between measured IS and interaction energy 66
• 4.3.7 Attachment behavior of P. putida 67
• 4.3.8 Effect of non-DLVO interactions 67
• 4.4 Conclusions 68
• 5 Influence of sorption types on bacteria transport through sand column: Modeling approach 77
• 5.1 Introduction 78
• 5.2 Column experiment 79
• 5.3 Modeling of bacteria transport 80
• 5.3.1 Transport models 80
• 5.3.2 Numerical solution 82
• 5.3.3 Model validation procedure 83
• 5.4 Result and discussion 84
• 5.4.1 Experimental data of bacterial BTC 84
• 5.4.2 Evaluation of transport parameters 84
• 5.4.3 Comparison of sorption models 87
• 5.5 Conclusion 97
• 6 Transport and degradation of toluene in the presence of bacteria: Model development and verification 100
• 6.1 Introduction 101
• 6.2 Model development 103
• 6.2.1 Contaminated groundwater system in the presence of bacteria 103
• 6.2.2 Bacteria transport model 105
• 6.2.3 Bacteria associated transport model for organic contaminant 109
• 6.2.4 Solution of transport model 112
• 6.3 Model verification 113
• 6.3.1 Experimental data 113
• 6.3.2 Input parameters for model verification 114
• 6.3.3 Simulation of toluene transport in the presence of bacteria 118
• 6.4 Sensitivity analysis 118
• 6.5 Processes affecting transport of toluene 126
• 6.6 Conclusion 127
• 7 Novel method for determination of phenol degradation kinetics 134
• 7.1 Introduction 135
• 7.2 Material and methods 136
• 7.2.1 Phenol degradation experiment 136
• 7.2.2 Estimation of degradation rate 138
• 7.2.3 Degradation kinetics 139
• 7.2.4 Verification of q-S0 and q-S relations 140
• 7.3 Results and discussion 141
• 7.3.1 Observed phenol degradation 141
• 7.3.2 Degradation rates 142
• 7.3.3 Estimation of kinetic parameters 142
• 7.3.4 Simulation of degradation profile 144
• 7.4 Conclusion 147
• 8 General conclusion 153