Surfactant-enhanced Bioremediation Research Articles

Nonionic surfactant Tween 80-facilitated bacterial transport in porous media: A nonmonotonic concentration-dependent performance, mechanism, and machine learning prediction

The surfactant-enhanced bioremediation (SEBR) of organic-contaminated soil is a promising soil remediation technology, in which surfactants not only mobilize pollutants, but also alter the mobility of bacteria. However, the bacterial response and underlying mechanisms remain unclear. In this study, the effects and mechanisms of action of a selected nonionic surfactant (Tween 80) on Pseudomonas aeruginosa transport in soil and quartz sand were investigated. The results showed that bacterial migration in both quartz sand and soil was significantly enhanced with increasing Tween 80 concentration, and the greatest migration occurred at a critical micelle concentration (CMC) of 4 for quartz sand and 30 for soil, with increases of 185.2% and 27.3%, respectively. The experimental results and theoretical analysis indicated that Tween 80-facilitated bacterial migration could be mainly attributed to competition for soil/sand surface sorption sites between Tween 80 and bacteria. The prior sorption of Tween 80 onto sand/soil could diminish the available sorption sites for P. aeruginosa, resulting in significant decreases in deposition parameters (70.8% and 33.3% decrease in KD in sand and soil systems, respectively), thereby increasing bacterial transport. In the bacterial post-sorption scenario, the subsequent injection of Tween 80 washed out 69.8% of the bacteria retained in the quartz sand owing to the competition of Tween 80 with pre-sorbed bacteria, as compared with almost no bacteria being eluted by NaCl solution. Several machine learning models have been employed to predict Tween 80-faciliated bacterial transport. The results showed that back-propagation neural network (BPNN)-based machine learning could predict the transport of P. aeruginosa through quartz sand with Tween 80 in-sample (2 CMC) and out-of-sample (10 CMC) with errors of 0.79% and 3.77%, respectively. This study sheds light on the full understanding of SEBR from the viewpoint of degrader facilitation.

Surfactant-enhanced bioremediation of petroleum-contaminated soil and microbial community response: A field study

Surfactant-enhanced bioremediation (SEBR) is frequently employed to clean up soil polluted with petroleum hydrocarbons, but few studies have focused on how surfactants affect microbial communities and different fractions of petroleum hydrocarbons, particularly in the field. Here, the surfactants sodium dodecyl benzene sulfonate (SDBS), alpha olefin sulfonate (AOS), Triton X-100 (TX-100), Tween80, and rhamnolipid were combined with the oil-degrading bacterium Pseudomonas sp. SB to remediate oil-contaminated soil in the laboratory. AOS gave the highest removal efficiency (65.1%) of total petroleum hydrocarbons (TPHs). Therefore, AOS was used in a field experiment with Pseudomonas sp. SB and the removal efficiency of TPHs and long-chain hydrocarbons C21–C40 reached 57.4 and 53.0%, respectively, significantly higher than the other treatments. During bioremediation the addition of Pseudomonas sp. SB significantly stimulated the growth of bacterial genera such as Alcanivorax, Luteimonas, Parvibaculum, Stenotrophomonas, and Pseudomonas and AOS further stimulated the growth of Sphingobacterium, Pseudomonas and Alcanivorax. This study validates the feasibility of surfactant-enhanced bioremediation in the field and partly reveals the mechanism of surfactant-enhanced bioremediation from the perspective of changes in different fractions of petroleum and microbial community dynamics.

The impact of natural and synthetic surfactants on bacterial community during hydrocarbon biodegradation

The aim of this study was to analyse the basic mechanisms of the interaction of surfactants anionic rhamnolipids and non-ionic polysorbate-80 on a microbial consortium during the biodegradation of diesel oil under model conditions. The analysed surfactants significantly influenced the metapopulation changes of microorganisms and caused a decrease in metabolic activity; however, they did not decrease the biodiversity of the studied system. Polysorbate-80 was relatively resistant to biological decomposition, whereas rhamnolipids were subjected to biodegradation as well as microbial transformation, as confirmed by the activity of the RhlC gene. Determination of biodegradation kinetics confirmed the positive influence of polysorbate-80 on the degradation efficiency of diesel oil hydrocarbons. The addition of this surfactant in 2-fold and 4-fold critical micelle concentration revealed a positive influence on the total petroleum hydrocarbons biodegradation by 18% and 15% respectively. Rhamnolipids exhibited an inhibiting effect in all fractions, with the exception of n-alkanes. The biodegradation efficiency of total petroleum hydrocarbons was 47% and 40% lower in samples containing biosurfactants in 2-fold and 4-fold critical micelle concentration, compare to that of the control sample. The surfactant-enhanced bioremediation method is a promising alternative to traditional methods; however, the method's efficiency is associated with the proper selection of a surfactant and its concentration and consideration of the occurrence of toxic effects as well as changes in the local soil metapopulation.

Soil bacterial community dynamics following surfactant addition and bioaugmentation in pyrene-contaminated soils

Because of their toxic properties, polycyclic aromatic hydrocarbons (PAHs) are designated as priority pollutants. The low solubility and strong sorption of PAHs in soil often limits bioremediation. To increase PAH bioavailability and enhance microbial degradation, surfactants are often added to contaminated soils. However, the effects of surfactants on the PAH degradation capacities of soil microbes are generally neglected. In this study, 16S rRNA gene high-throughput sequencing was used to evaluate changes in the soil microbial community after the application of rhamnolipid biosurfactant or Brij-35 surfactant and Mycobacterium vanbaalenii PYR-1 bioaugmentation over a 50-d mineralization study in two soils contaminated with pyrene at 10 mg kg−1. The introduction of pyrene in both soils resulted in an increase in Firmicutes and a decrease in microbial richness and Shannon diversity index. Amendment of rhamnolipid at 1,400 μg g−1 to the native clay soil resulted in a decrease in Bacillus from 48% to 2%, which was accompanied with an increase in Mycoplana that accounted for 67% of the total genera relative abundance. Phylogenetic investigation of communities by reconstruction of unobserved states was used to predict the activity of functional genes involved in the PAH degradation KEGG pathway and determined that M. vanbaalenii PYR-1 bioaugmentation resulted in an increased number of functional genes utilized in PAH biodegradation. Results of this study provide a better understanding of the soil microbial dynamics in response to surfactant amendments in addition to bioaugmentation of a PAH-degrading microbe. This knowledge contributes to successful and efficient surfactant-enhanced bioremediation of PAH-contaminated soils.

Effect of surfactants on the solubilization, sorption and biodegradation of benzo (a) pyrene by Pseudomonas aeruginosa BT-1

Abstract In order to better understand in bioremediation of high molecular weight PAHs, the solubilization, sorption and biodegradation of benzo (a) pyrene (BaP) by Pseudomonas aeruginosa BT-1 in the presence of surfactants including Tween 80,DOSS (dioctyl sodium sulfosuccinate), rhamnolipid were evaluated. Periodically collected samples were detected by the technology of RP-HPLC (reverse phase high-performance liquid chromatograph) with FLD (Fluorescence Detector). The solubilization capacity of BaP by surfactants was followed the order: Tween 80 > Rhamnolipid > DOSS and the solubility enhancement degree ( S w * / S w ) of PAHs by Tween 80 was followed the order: BaP > Pyrene > Phenanthrene. Moreover, Tween 80 exhibited a higher sorption rate of BaP as comparison to DOSS or rhamnolipid at a low concentration ( CMC). When strain BT-1 was used for degrading BaP, Tween 80 also performed a higher biodegradation rate with 79.7% of BaP degraded while rhamnolipid exhibited a low level with only 16.96%. Besides, the growth of microorganism was inhibited in DOSS supplied system, resulting in very low biodegradation rate. However, the above experimental data were all fitted to the logistic kinetic model (R2≥ 0.97). Therefore, we concluded Tween 80 was the preferred surfactant in surfactant-enhanced bioremediation of BaP by strain BT-1.

Surfactant-enhanced Bioremediation of n-Hexadecane-contaminated Soil Using Halo-tolerant Bacteria Paenibacillus glucanolyticus sp. Strain T7-AHV Isolated from Marine Environment

A halo-tolerant bacterial strain Paenibacillus glucanolyticus sp. strain T7-AHV isolated from marine environment was used for bioremediation of n-hexadecane-contaminated soil. Soil/water ratio, initial inoculums volume, surfactant addition, n-hexadecane concentration, and salinity were investigated. The possibility of biosurfactant production by isolated strain was also studied, and the results demonstrated that it was not a biosurfactant producer, based on measurement of the surface tension of culture broth. Both tween 80 and rhamnolipid enhanced the biodegradation of n-hexadecane significantly up to 44 and 46 %, respectively. A biodegradation rate of 39.7 % was observed at salinity level of up to 2 %, and the biodegradation efficiency decreased significantly at higher salinity concentrations. A natural hydrocarbon-contaminated soil sample with total petroleum hydrocarbon (TPH) concentration of 1437 mg kg–1 was subjected to bioremediation using the selected conditions of operational parameters, and a biodegradation rate of 22.1 % was obtained.

Efficiency of surfactant-enhanced bioremediation of aged polycyclic aromatic hydrocarbon-contaminated soil: Link with bioavailability and the dynamics of the bacterial community

Shifts in the bacterial-community dynamics, bioavailability, and biodegradation of polycyclic aromatic hydrocarbons (PAHs) of chronically contaminated soil were analyzed in Triton X-100–treated microcosms at the critical micelle concentration (T-CMC) and at two sub-CMC doses. Only the sub-CMC-dose microcosms reached sorbed-PAH concentrations significantly lower than the control: 166±32 and 135±4mgkg−1 dry soil versus 266±51mgkg−1; consequently an increase in high- and low-molecular-weight PAHs biodegradation was observed. After 63days of incubation pyrosequencing data evidenced differences in diversity and composition between the surfactant-modified microcosms and the control, with those with sub-CMC doses containing a predominance of the orders Sphingomonadales, Acidobacteriales, and Gemmatimonadales (groups of known PAHs-degrading capability). The T-CMC microcosm exhibited a lower richness and diversity index with a marked predominance of the order Xanthomonadales, mainly represented by the Stenotrophomonas genus, a PAHs- and Triton X-100–degrading bacterium. In the T-CMC microcosm, whereas the initial surface tension was 35mNm−1, after 63days of incubation an increase up to 40mNm−1 was registered. The previous observation and the gas-chromatography data indicated that the surfactant may have been degraded at the CMC by a highly selective bacterial community with a consequent negative impact on PAHs biodegradation. This work obtained strong evidence for the involvement of physicochemical and biologic influences determining the different behaviors of the studied microcosms. The results reported here contribute significantly to an optimization of, surfactant-enhanced bioremediation strategies for chronically contaminated soil since the application of doses below the CMC would reduce the overall costs.

Surfactant-enhanced bioremediation of DDTs and PAHs in contaminated farmland soil

ABSTRACTField-scale bioremediation of dichlorodiphenyl trichloroethanes (DDTs) and polycyclic aromatic hydrocarbons (PAHs) contaminated farmland soil from the Shenyang North New Area of China was studied using the bacteria Arthrobacter globiformis. The additive effects of different concentrations of biosurfactant rhamnolipids (RLs) and anionic–nonionic mixed surfactant (SDBS–Tween 80) were evaluated. DDT and PAH removal rates by A. globiformis after 150 days of remediation were 52.1% and 21.9%, respectively. At the optimum RL concentration of 5 mg kg−1, DDTs and PAHs had removal rates of 64.3% and 35.6%, respectively, at 150 days. This was 60.7% and 29.3% higher than the control; 36.9% and 19.8% higher than soil with RL-5 alone; and 12.2% and 13.8% higher than the A. globiformis treatment alone. RL-5 can enhance soil enzyme activity and A. globiformis reproduction during the DDT and PAH biodegradation processes. This study illustrates a highly efficient, low-cost in situ soil bioremediation technology that could have practical utility.

Shifts in microbial community structure during in situ surfactant-enhanced bioremediation of polycyclic aromatic hydrocarbon-contaminated soil.

This study aims to reveal the microbial mechanism of in situ surfactant-enhanced bioremediation (SEBR). Various concentrations of rhamnolipids, Tween 80, and sodium dodecyl benzenesulfonate (SDBS) were separately sprayed onto soils contaminated with polycyclic aromatic hydrocarbons (PAHs) for years. Within 90days, the highest level of degradation (95%) was observed in the soil treated with rhamnolipids (10mg/kg), followed by 92% degradation with Tween 80 (50mg/kg) and 90% degradation with SDBS (50mg/kg). The results of the microbial phospholipid fatty acids (PLFAs) suggest that bacteria dominated the enhanced PAH biodegradation (94% of the maximum contribution). The shift of bacterial community structure during the surfactant treatment was analyzed by using the 16S rRNA gene high-throughput sequencing. In the presence of surfactants, the number of the operational taxonomic units (OTUs) associated with Bacillus, Pseudomonas, and Sphingomonas increased from 2-3 to 15-30% at the end of the experiment (two to three times of control). Gene prediction with phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) shows that the PAH-degrading genes, such as 1-hydroxy-2-naphthoate dioxygenase and PAH dioxygenase large subunit, significantly increased after the surfactant applications (p < 0.05). The findings of this study provide insights into the surfactant-induced shifts of microbial community, as well as critical factors for efficient bioremediation.

Effect of surfactant on phenanthrene metabolic kinetics by Citrobacter sp. SA01

To attain a better understanding of the effects of surfactants on the metabolic kinetics of hydrophobic organic compounds, the biodegradation of phenanthrene by Citrobacter sp. SA01 was investigated in a batch experiment containing Tween 80, sodium dodecyl benzene sulfonate and liquid mineral salt medium. The Monod model was modified to effectively describe the partition, phenanthrene biodegradation and biopolymer production. The results showed that Tween 80 and sodium dodecyl benzene sulfonate (each at 50mg/L) enhanced phenanthrene metabolism and poly-β-hydroxybutyrate production as indicated by the increasing amounts of intermediates (by 17.2% to 47.9%), and percentages of poly-β-hydroxybutyrate (by 107.3% and 33.1%) within the cell dry weight when compared to their absence. The modified Monod model was capable of predicting microbial growth, phenanthrene depletion and biopolymer production. Furthermore, the Monod kinetic coefficients were largely determined by the surfactant-enhanced partition, suggesting that partitioning is a critical process in surfactant-enhanced bioremediation of hydrophobic organic compounds.

Influences and mechanisms of surfactants on pyrene biodegradation based on interactions of surfactant with a Klebsiella oxytoca strain

Surfactant-enhanced bioremediation has been proposed as a promising technology for the treatment of organic polluted soils; however its application has been hindered by the controversial influences and mechanisms of surfactants on the biodegradation of hydrophobic organic compounds. To address this problem, effects of five surfactants on the sorption and biodegradation of pyrene by Klebsiella oxytoca PYR-1, as well as their interactions with bacterial cell surface and membrane lipids were investigated. We found that surfactants enhanced or inhibited pyrene biodegradation depending on their effects on the sorption of pyrene onto bacterial cell, which occurred mainly through modifying cell surface hydrophobicity (such as Tween series surfactants) or disrupting bacterial membrane (such as Triton X-100), respectively. A relatively high positive correlation (P<0.0001) was observed between biodegradation promotion (Bs/B0) and enhancement of sorption coefficients (Kd,s(∗)/Kd,0(∗)) for pyrene in the presence of surfactant, indicating that surfactant-induced sorption played the dominant role during pyrene biodegradation.

Partitioning of phenanthrene into surfactant hemi-micelles on the bacterial cell surface and implications for surfactant-enhanced biodegradation

Recent studies have suggested that the ability of a surfactant to enhance the bioavailability of hydrophobic organic compounds (HOC) requires the formation of surfactant hemi-micelles on the bacterial cell surface and subsequent partitioning of HOC into the hemi-micelles. However, the studies did not provide direct evidence of HOC partitioning into surfactant hemi-micelles on the bacterial cell surface. In this study, direct evidence is provided to demonstrate that the nonionic surfactant Brij 30 forms hemi-micelles on the bacterial cell surface and that phenanthrene sorption at the bacterial surface is enhanced by the surfactant. These results are in agreement with the current theory describing surfactant-enhanced HOC bioavailability. This enhanced bioavailability is put into context with microbial kinetics and system partitioning processes, and it is demonstrated that the addition of surfactant can enhance, have no effect, or inhibit HOC biodegradation depending upon surfactant concentration and microbial growth rate. Understanding these non-linear relationships between surfactant-enhanced HOC bioavailability, biodegradation kinetics, and system partitioning will assist in the design and implementation of surfactant-enhanced bioremediation programs.

Practical Considerations and Challenges Involved in Surfactant Enhanced Bioremediation of Oil

Surfactant enhanced bioremediation (SEB) of oil is an approach adopted to overcome the bioavailability constraints encountered in biotransformation of nonaqueous phase liquid (NAPL) pollutants. Fuel oils contain n-alkanes and other aliphatic hydrocarbons, monoaromatics, and polynuclear aromatic hydrocarbons (PAHs). Although hydrocarbon degrading cultures are abundant in nature, complete biodegradation of oil is rarely achieved even under favorable environmental conditions due to the structural complexity of oil and culture specificities. Moreover, the interaction among cultures in a consortium, substrate interaction effects during the degradation and ability of specific cultures to alter the bioavailability of oil invariably affect the process. Although SEB has the potential to increase the degradation rate of oil and its constituents, there are numerous challenges in the successful application of this technology. Success is dependent on the choice of appropriate surfactant type and dose since the surfactant-hydrocarbon-microorganism interaction may be unique to each scenario. Surfactants not only enhance the uptake of constituents through micellar solubilization and emulsification but can also alter microbial cell surface characteristics. Moreover, hydrocarbons partitioned in micelles may not be readily bioavailable depending on the microorganism-surfactant interactions. Surfactant toxicity and inherent biodegradability of surfactants may pose additional challenges as discussed in this review.

Effect of surfactant-induced cell surface modifications on electron transport system and catechol 1,2-dioxygenase activities and phenanthrene biodegradation by Citrobacter sp. SA01

In order to better understand how surfactants affect biodegradation of hydrophobic organic compounds (HOCs), Tween 80 and sodium dodecyl benzene sulfonate (SDBS), were selected to investigate effects on cell surface hydrophobicity (CSH), electron transport system (ETS) activities and phenanthrene biodegradation by Citrobacter sp. SA01. Tween 80 and SDBS increased CSH by 19.8–25.2%, ETS activities by 352.1–376.0μmol/gmin, catechol 1,2-dioxygenase (C12) activities by 50.8–52.7U/L, and phenanthrene biodegradation by 8.9–17.2% separately in the presence of 50mg/L of surfactants as compared to in their absence. Lipopolysaccharide (LPS) release was 334.7μg/mg in the presence of both surfactants whereas in their absence only 8.6–44.4μg/mg of LPS was released. Thus, enhanced LPS release probably increased ETS and C12 activities as well as phenanthrene biodegradation by increasing CSH. The results demonstrate that surfactant-enhanced CSH provides a simple, yet effective strategy for field applications of surfactant-enhanced bioremediation of HOCs.

Surfactant-Enhanced Desorption and Biodegradation of Polycyclic Aromatic Hydrocarbons in Contaminated Soil

We evaluated two nonionic surfactants, one hydrophobic (Brij 30) and one hydrophilic (C(12)E(8)), for their ability to enhance the biodegradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil after it had been treated in an aerobic bioreactor. The effects of each surfactant were evaluated at doses corresponding to equilibrium aqueous-phase concentrations well above the surfactant's critical micelle concentration (CMC), slightly above the CMC, and below the CMC. The concentrations of all 3- and 4-ring PAHs were significantly lower in the soil amended with Brij 30 at the two lower doses compared to controls, whereas removal of only the 3-ring PAHs was significantly enhanced at the highest Brij 30 dose. In contrast, C(12)E(8) did not enhance PAH removal at any dose. In the absence of surfactant, <5% of any PAH desorbed from the soil over an 18 day period. Brij 30 addition at the lowest dose significantly increased the desorption of most PAHs, whereas the addition of C(12)E(8) at the lowest dose actually decreased the desorption of all PAHs. These findings suggest that the effects of the two surfactants on PAH biodegradation could be explained by their effects on PAH bioavailability. Overall, this study demonstrates that the properties of the surfactant and its dose relative to the corresponding aqueous-phase concentration are important factors in designing systems for surfactant-enhanced bioremediation of PAH-contaminated soils in which PAH bioavailability is limited.

Effect of a commercial alcohol ethoxylate surfactant (C11-15E7) on

Biodegradation of poorly soluble polycyclic aromatic hydrocarbons (PAHs) has been a challenge in bioremediation. In recent years, surfactant-enhanced bioremediation of PAH contaminants has attracted great attention in research. In this study, biodegradation of phenanthrene as a model PAHs solubilized in saline micellar solutions of a biodegradable commercial alcohol ethoxylate nonionic surfactant was investigated. The critical micelle concentration (CMC) of the surfactant and its solubilization capacity for phenanthrene were examined in an artificial saline water medium, and a type of marine bacteria, Neptunomonas naphthovorans, was studied for the biodegradation of phenanthrene solubilized in the surfactant micellar solutions of the saline medium. It is found that the solubility of phenanthrene in the surfactant micellar solutions increased linearly with the surfactant concentrations, but, at a fixed phenanthrene concentration, the biodegradability of phenanthrene in the micellar solutions decreased with the increase of the surfactant concentrations. This was attributed to the reduced bioavailability of phenanthrene, due to its increased solubilization extent in the micellar phase and possibly lowered mass transfer rate from the micellar phase into the aqueous phase or into the bacterial cells. In addition, an inhibitory effect of the surfactant on the bacterial growth at high surfactant concentrations may also play a role. It is concluded that the surfactant largely enhanced the solubilization of phenanthrene in the saline water medium, but excess existence of the surfactant in the medium should be minimized or avoided for the biodegradation of phenanthrene by Neptunomonas naphthovorans.

Preferential surfactant utilization by a PAH-degrading strain: effects on micellar solubilization phenomena.

Biodegradable nonionic Tween series surfactants were employed to assess the effects of synthetic surfactants on the bioavailability of a target polycyclic aromatic hydrocarbon (PAH), phenanthrene, in soil/sediment-free micellar solutions. Dosages of surfactants in excess of their respective critical micelle concentrations (CMCs) dramatically enhanced solubilization of phenanthrene, but the micellar-solubilized phenanthrene was neither directly nor readily bioavailable to the PAH-degrading strain, Sphingomonas paucimobilis EPA 505, used in these bioavailability experiments. The microorganism preferred instead to utilize hydrophobic fractions of the Tween surfactants as a carbon source, resulting in an imbalance of amphiphilic moieties in surfactant molecules and associated destabilization of micelles. This effect was assessed by measurements of surface tension, CMCs, weight-based PAH solubilization ratios, and by characterizations of the surfactants via HPLC separation and emulsification behavior. The observations and analyses lead to a conclusion that preferential biological destabilization of surfactant micelles effects an associated release of phenanthrene to the aqueous phase. The phenanthrene so released then apparently reverts to a crystallized form that appears to be bioavailable only through normal re-dissolution to the aqueous phase. This is, to our knowledge, the first attempt to characterize and quantify changes in the properties and solubilization behaviors of surfactant micelles resulting from their partial and preferential biodegradation. The associated re-deposition of previously micellar-solubilized PAHs observed and the loss of solubilization capacity of recovered surfactants have significant implications for applications of surfactant-enhanced bioremediation of contaminated soils and sediments.

FEASIBILITY OF IN SITU NAPL-CONTAMINATED AQUIFER BIOREMEDIATION BY BIODEGRADABLE NUTRIENT–SURFACTANT MIX

Entrapped non-aqueous liquid phase (NAPL) pollutants (e.g., fuels) constitute one of the biggest current problems in the bioremediation efforts of contaminated soil and aquifers worldwide. On site, in situ surfactant-enhanced bioremediation, in the presence of sufficient nutrients and dissolved oxygen, has the potential of becoming the remediation method of choice in terms of both technological and economical feasibility. This approach was applied in our lab-scale column-based flow system with the aid of which an optimized, below CMC, of biodegradable surfactant-nutrient surfactant mix has been established for the best solubilization/mobilization of NAPL (hexane, toluene, kerosene and their mixtures as “representatives”) in sandy matrix. For kerosene, the highest f values (the enhancement factors) were obtained for the systems containing either the amphoteric cocoamphodiacetate or the anionic linear dodecylbenzene sulfonate (0.1–0.3 g/L) with one or both the nutrient-surfactants L and B (0.05 g/L).

Surfactant-Enhanced Biodegradation of a PAH in Soil Slurry Reactors

This study focuses on finding operational regimes for surfactant-enhanced biodegradation. Biodegradation of phenanthrene as a model poly cyclic aromatic hydrocarbon (PAH) was studied in soil slurry reactors in the presence and absence of a Triton N-101 surfactant solution. Results showed that the presence of surfactant slowed the initial biodegradation rate of phenanthrene, but increased the total mass of phenanthrene degraded over a four day period by 30%. A mathematical model was developed which simulates the biodegradation of low solubility hydrocarbons in the presence of soils and surfactants by accounting for the hydrocarbon bioavailability in different phases of the system. The model was able to simulate the experimental results using parameters and rate coefficients that were obtained through independent experiments.The model was used to investigate the effect of different operating conditions on the overall biodegradation of phenanthrene. Simulation results showed that there is a system-specific optimum surfactant concentration range, beyond which bioremediation is hindered. The results also indicate that for a given system, the optimal surfactant concentration can be determined from simple sorption and solubility equilibrium experiments. Finally, a metric is presented for determining the potential effectiveness of surfactant-enhanced bioremediation based on the Monod and bioavailability parameters for a given system.

Surfactant-enhanced bioremediation of polynuclear aromatic hydrocarbons in coke waste

Surfactant-enhanced bioremediation of polynuclear aromatic hydrocarbons in coke waste