After an initial screening procedure, silicone oil was selected as the non-aqueous phase fluid in the TPPB system. Md Residual content of pyrene in the gelling medium after encapsulation (mg) Mi Initial content of pyrene in the hydrogel mixture before encapsulation (mg) Mt Amount of pyrene released at time t.
Generalities
Pressurized hot water extraction (PHWE) has recently been widely used to extract hydrophobic PAHs from contaminated soils and sediments (Smith, 2002; Rivas et al., 2008). Ozone is a highly reactive and powerful oxidizing agent that has been used in the chemical industry as an oxidizing agent and is also widely used in the treatment of drinking water (Rositono et al., 2001).
Biological Methods
Surfactant aided biodegradation of PAHs
However, use of surfactants has resulted in contrasting effects ranging from enhancement to inhibition of PAH biodegradation. Therefore, it seems that the applicability of surfactants in the biodegradation of PAHs cannot be overgeneralized, rather, sufficient efforts should be made to understand the microbial system in the context of the PAHs under investigation.
Two liquid phase partitioning bioreactor system
- Critical design criteria for TPPB in biodegradation
The last two properties of organic phase are most crucial and must be considered in the context of microorganisms being used in the TPPB system. Another important design criterion is the increased surface area due to emulsion formation between the NAPL and the aqueous phase in the TPPB system.
Objective and Scope
Feasibility study to improve pyrene water solubility and biodegradation using an indigenous mixed culture capable of biosurfactant production. Development and evaluation of a two-phase distribution bioreactor system for the biodegradation of pyrene by M.
Organization of the Thesis
The emulsion stability was thus expressed as the decay constant (Kd) in the following equation (Kim et al. 2000). The results of pyrene degradation in the TPPB system are discussed in the next section.
LITERATURE REVIEW 13
Sources and distribution of PAHs in the environment. …
Anthropogenic sources of PAHs include the combustion of fossil fuels (coal and petroleum) or wood (pyrolytic) and crude/refined petroleum from accidental oil spills, discharges from routine tanker operations (petrogenic) (Zakaria et al., 2002; Kannan et al. , 2005). Perylene is known to be produced biologically in anaerobic environments in soils and sediments (Wilcke et al., 2002).
Toxicity of PAHs
Bladder production rates were significantly reduced compared to controls in the soil test at higher concentrations and completely ceased at 640 mg kg-1. Pyrene mainly affected genes involved in the maintenance of the genetic apparatus, immune response, glycolysis and iron homeostasis.
Analysis of PAH in environmental samples
The detection limits were found to be < 1 µg l-1. 2006) used SF method for the quantification of benzo[a]pyrene in solvent extract from spiked soil. The authors validated the SF method against HPLC and found a good correlation between the two with a detection limit of 1.6 µg l-1 for the SF method.
Remediation of PAHs Contaminated Environment
- Physical methods
- Chemical methods
- Biological methods for PAHs remediation
- Plant assisted PAHs biodegradation
- PAHs biodegradation by fungi and bacteria. …
- Biodegradation of PAHs mixture
- Biodegradation kinetics
Subsequent enzymatic reactions, including intradiol ring cleavage dioxygenation, result in the production of o-phthalate (Kim et al., 2007). In a study by Ye et al. 1996), the presence of PAHs, including benzo[a]anthracene, benzo[b]fluoranthene, chrysene, dibenzo[a,h]anthracene, and fluoranthene, did not affect the degradation of benzo[a]pyrene by Sphingomonas paucimobilis.
Surfactant Aided Biodegradation of PAHs
- Chemical surfactants
- Biosurfactants
In the case of pyrene, only slight improvement (32% degradation) was observed for 30% acetone compared to that in water (∼20% degradation). The combinations of PAH concentrations adopted in the experimental tests are shown in Table 3.4. All statistical analysis of the results in the study was done using MINITAB software (Version 15, PA, USA).
Simple Cost Benefit analysis of the three systems evaluated in the present work Current work.
Solvent Aided Biodegradation of PAHs
Two Phase Systems for PAH Biodegradation
- Choice of solvents in TPPB system
- Interfacial area in TPPB system
- Non-conventional two Phase system
Hydrophobic nature of PAHs makes them ideal candidates for degradation in TPPB systems, as high concentration and large surface area can be achieved by dissolving PAHs in. The main components of TPPBs are the substrate dissolved in the organic phase, inorganic nutrients dissolved in the aqueous phase, oxygen and microbial cells. Therefore, any variation in the interfacial area affects both the activity of suspended microorganisms in the aqueous phase and the activity of adherent microorganisms at the liquid–liquid interface.
The substrate concentration in the aqueous phase was independent of the size of the interfacial area at different stirrer speeds and decreased as the proportion of silicone oil phase increased.
Statistical Design of Experiments
Protein concentrations in the samples were thus determined from the following equation (Makkar et al., 1982). Furthermore, the biodegradation of pyrene by Mycobacterium does not result in the accumulation of any process intermediates (Giessing and Johnsen, 2005). The associated P values of the main effects of all factors indicate high significance in the model (>95% confidence level).
From these results, it can be seen that the PAH removal pattern was a function of the initial concentrations in the mixture.
MATERIALS AND METHODS 72
Microorganisms and Culture Conditions
- Mycobacterium frederiksbergense
- Mycobacterium vanbaalenii
- Indigenous biosurfactant producing soil microbial culture. …. 73
- Single substrate condition
- Mixed substrate conditions
Culture purity was ensured by plating a single colony from the previous culture on a nutrient agar plate. After evaporation of acetone, 100 ml of BH medium supplemented with a solution of trace elements was added and autoclaved. After autoclaving the media at 15 psi for 15 min and allowing them to cool to room temperature, naphthalene was added aseptically from its filter-sterilized stock solution (5 g l-1 in acetone) in such an amount to obtain the desired concentration of the compound as indicated in the experiment plan (Table 3.1).
For estimation of the PAHs, aqueous samples were extracted with ethyl acetate and analyzed by synchronous fluorescence spectroscopy.
Biodegradation Studies in Surfactant Aided System
- Pyrene degradation using Triton X 100 as the surfactant. …
- Evaluation of different chemical surfactants
- Determination of molar solubilization ratio of
- Pyrene degradation experiments
- Evaluation of a biosurfactant produced by indigenous soil
- Isolation and partial purification of the
- PAHs solubilisation assay
- Effects of environmental factors on emulsification
- Pyrene biodegradation using Tween 80 as the surfactant
- Single substrate condition
- Mixed substrate condition
After placing the cuvette in the holder of a spectrophotometer (SPEKOL 1200, Analytikjena®), 1 ml of pre-filtered (0.45 µm, Millipore®) test solution containing the desired concentrations of the biosurfactant was added. Similar experiments were conducted to observe the effect of temperature on emulsification activity and biosurfactant stability. The flasks containing varying concentrations of Tween 80 solubilized pyrene in the range of 0.1 to 10 mg l-1 were inoculated with 5 ml of the Mycobacterium culture and incubated for 48 hours.
The biodegradation of pyrene by Mycobacterium in the Tween 80-assisted system was also carried out in the presence of other PAHs, namely anthracene and naphthalene.
Biodegradation Study in Two Phase Partitioning Bioreactor Systems. 85
- Determination of volumetric oxygen mass transfer coefficient 86
- Mixed substrate condition
In the TPPB system containing silicone oil and water phase, the effect of the addition of the solvent on oxygen mass transfer coefficient (kLa) in the system was evaluated. The ranges of operating conditions adopted in the experiments were as follows: silicone oil volume. Both the aqueous and organic phases were loaded into the fermenter together and autoclaved.
The fermentor operating conditions were identical to those in the single substrate condition, as previously described.
Evaluation of a Non-Conventional TPPB System in Pyrene
- Standardization of pyrene encapsulation method
- Characterization of the bead type V
- Swelling behavior
- Optical and scanning electron microscopy
- Pyrene release kinetics
- Reusability test of the bead type V
- Pyrene biodegradation experiments using the bead type V…
The swollen beads were handled carefully to avoid breakage or erosion of the beads. To clearly distinguish silicone oil droplets in the encapsulated beads, cross-sections of the air-dried beads were observed under a stereozoom microscope (Nikon, USA). To investigate the effect of concentrations of surfactants in the release medium on pyrene release, the calculated amount of the encapsulated beads containing 500 μg of pyrene was taken in 250 mL Erlenmeyer flasks with different concentrations of Triton X CMC) in 100 mL of release medium.
To demonstrate the utility of the developed non-conventional TPPB method for pyrene biodegradation applications, experiments were carried out using M.
Analytical Techniques
- Pyrene analysis
- Naphthalene and anthracene analysis in mixtures containing
- Analysis of surfactants
- Cell growth measurements
Biodegradation of pyrene in such a slurry phase system essentially depends on the dissolution kinetics, which in turn is a function of operating conditions prevailing in the system. In the absence of the two organisms, total pyrene concentration remained the same, thus showing that pyrene removal was due to biological degradation in the experiments. The MSR values of pyrene obtained using the surfactants were also found to be close to the reported values in the literature (Mohamed and Mahfoodah, 2006; Prak and Pritchard, 2002).
In this study, the degradation rate of pyrene at all initial concentrations (except at 200 mg l−1) is much higher, indicating superior performance of M.
RESULTS AND DISCUSSIONS 103
Single substrate condition
In the batch operated fermenter, pyrene was completely degraded within 200 h to the same initial concentration of 50 mg l−1. Although no initial lag phase in degradation was observed in the slurry phase fermenter, the total degradation rate was only 6 mg l−1 d−1. The observed difference in pyrene biodegradation rate and pattern in shake flask and fermenter may well be attributed to the difference in operating conditions between the two.
Similarly, the negative effect of naphthalene on anthracene biodegradation in this study could be attributed to the same phenomenon.
Pyrene Biodegradation in Surfactant Aided System
- Pyrene biodegradation with Triton X 100 as the surfactant. … 113
- Evaluation using a biosurfactant producing indigenous soil
- Culture growth and biosurfactant production
- Isolation and partial purification of the
- Properties of the partially purified biosurfactant
- Pyrene biodegradation using Tween 80
- Single substrate condition
- Mixed substrate condition
The ANOVA also shows that error term in the model is less (MS = 1.05), which suggests a good accuracy of the results obtained from the experiments. Since the increase in the biosurfactant amount was synchronous with the growth of the soil culture, it is reasonable to say that the biosurfactant production was a growth-associated one (Mulligan, 2005). From the results of the calculated MSR values and pyrene degradation profile, Tween 80 showed good potential in the biodegradation of pyrene by M. frederiksbergense and therefore identified as the best among the five synthetic surfactants for further investigations.
Generally, Fischer's 'F' value with a low probability 'P' value in the ANOVA table showed high significance of the regression model (Montgomery, 2004).
Pyrene Biodegradation in TPPB System
- Selection of solvents
- Determination of volumetric oxygen mass transfer coefficient
- Pyrene biodegradation experiments in the TPPB system
- Single substrate condition
- Mixed substrate condition
Before actual biodegradation experiments in this system, the volumetric oxygen mass transfer coefficient in the two-phase system was determined to optimize the operating conditions, namely the silicone oil fraction, agitation, and aeration rate in the system. Determination of the volumetric oxygen mass transfer coefficient and enhancement factor in the two-phase system containing silicone oil, and the water enhancement factor in the two-phase system containing silicone oil and water. Similar results have been reported by Dumont et al. 2006), where the authors attribute inhibition of the rate of oxygen mass transfer in two phases due to the organic phase silicone oil in the system.
In general, the enhancement factor was found to decrease with higher silicone oil fraction in the two liquid phase system, especially at an aeration rate of 2.5.
Simple Cost Benefit Analysis of the Three Systems Evaluated in the
The cost analysis of the three biodegradation systems investigated in this work was carried out, taking into account the costs of preparing the inoculum, the media ingredients and its preparation (if any), the energy consumption while performing the batch experiments, either in a shake flask or in a fermenter. It can be mentioned here that the power requirement costs were independent of the volume of inoculum to be prepared, as it was always grown in a shaking incubator for 12 h. Costs were highly variable depending on the volume of media, regardless of the type of system used.
Although the TPPB system appears much more economical when compared to other biodegradation systems, it is evident from Table 4.16 that about 75% of the total cost is due to the high energy consumption of the system.
Performance Evaluation of a Non-Conventional TPPB System
- Standardization of pyrene encapsulation method
- Characterization of the bead type V
- Swelling behavior
- Optical and scanning electron microscopy
- Pyrene release kinetics
- Reusability test of bead type V
- Pyrene biodegradation experiments using the bead type V…
The encapsulation efficiency of pyrene was found to be over 99% for all five different types of beads. Type of beads I Type of beads II Type of beads III Type of beads IV Type of beads V. Figure 4.26: Cumulative release of pyrene as % of its total encapsulated amount from different types of beads in 10 solutions of CMC Triton X 100. A higher concentration of surfactant in the medium resulted in greater extent of pyrene release, probably due to increased solubility and equilibrium saturation of pyrene.
Moreover, the degree of pyrene release from bead type V was comparable to the test system where free silicone oil containing equivalent amount of pyrene was simply mixed with surfactant solution.
Schematic of soil vapor extraction system
Schematic of a super critical fluid extraction system
Fungal metabolism of pyrene …
Pyrene degradation pathway of Mycobacterium sp
Schematic representation of micelle and reverse micelle formation
SF concentration calibration curve used in pyrene analysis at
Interference to pyrene estimation by an equal concentration of
Selection of SF parameters for the identification of naphthalene,
Calibration curves used in the analysis of synthetic surfactants by
Calibration curve used in the colorimetric analysis of SDS
Pyrene degradation profiles in the slurry phase system
PAHs biodegradation profiles under mixed substrate conditions in
Pyrene degradation efficiency in the Triton X 100 aided system. …
