Effect Of Bioaugmentation Research Articles

Effect of long-term bioaugmentation on nitrogen removal and microbial ecology for an A2O pilot-scale plant operated in low SRT

The effect of long-term bioaugmentation on nitrogen removal, nitrification activity, and microbial ecology for an anaerobic/anoxic/aerobic (A2O) pilot-scale plant operated in low sludge retention time (SRT) to treat municipal wastewater was investigated. Reject water from sludge treatment was used as a feed to cultivate the nitrifier contained in activated sludge for bioaugmentation. Under the conditions of 10 h hydraulic retention time, 8 d of SRT, and 14°C water temperature ammonia removal efficiency increased by 25%, and specific ammonia utilizing rate and specific nitrite utilizing rate increased by 1.86 and 1.90 times, respectively. The percentages of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in the total number of bacteria increased from 2.4 and 2.1% to 6.8 and 7.8%, respectively. The dominant AOB and NOB were transformed from Nitrosospira and Nitrospira to Nitrosomonas europaea and Nitrobacter.

염료 분해균 증대를 통한 Pilot Plant에서의 담체 내 미생물 생태와 색도처리에 미치는 영향

In a pilot-scale dyeing wastewater treatment using two-type fluidizing media, each thickness of biofilm was 15 and 30 <TEX>${\mu}m$</TEX>, respectively. The numbers of protozoa inhabited in small-size (PEMT A) and big-size (PEMT B) media were <TEX>$7.5{\times}10^4$</TEX> and <TEX>$1.25{\times}10^5$</TEX> cells/ml, respectively, and dominant species were Entosiphon sulcatus var sulcatus in PEMT A and Chlamydomonas reinhardtii in PEMT B, respectively. Flask experiments using the two media revealed that the percentages of color removal were 25.8% in PEMT A and 27.1% in PEMT B after 72-h cultivation, indicating the necessity of bioaugmentation. Experiments for bioaugmentation effect on color removal were carried out in the pilot-scale treatment for 75 d by three-step operation under the control of wastewater loading rate and microbial input rate. Dye degradation occurred mainly in the second reaction tank, and the attachment of augmented dye-degrading microorganisms to media took at least 35 d. Final value of chromaticity in effluent was 227, meeting the required standard. Therefore bioaugmentation onto media was good for color treatment. In summary, thickness of biofilm formed on the media depended upon the size of media, resulting in different ecosystem inside the media. Hence, this affected microbial community and color treatment further. Accordingly, the reduction of operation cost is expected by efficient color-treatment process using bioaugmented media.

E Ffectiveness of Intrinsic Biodegradation Enhancement in Oil Hydrocarbons Contaminated Soil

Abstract Studies were conducted using a 10-chamber Micro-Oxymax (Columbus, OH, USA) respirometer to determine the effect of bioaugmentation, biostimulation and combination of them on enhancing intrinsic biodegradation of oil hydrocarbons in soil. Contaminated soil was collected from a former military airport in Kluczewo, Poland. Bioaugmentation was realized by addition of indigenous or exogenous bacteria to soil. Biostimulation was done by aerated water supply and surfactant addition. Bioaugmentation + addition of a surfactant was applied as the combined treatment. The intrinsic and enhanced hydrocarbons biodegradation rates were estimated from the slopes of linear regressions of cumulative curves of O2 uptake. Pertinent biodegradation rates were recalculated on the basis of the stoichiometric reaction (mass balance equation) and conversion equation. The results showed that combined treatment (indigenous bacteria bioaugmentation + addition of a surfactant) was the most effective method of biodegradation enhancement as the 20-fold increase of biodegradation rate was observed.

Support vector regression model of wastewater bioreactor performance using microbial community diversity indices: Effect of stress and bioaugmentation

The relationship between microbial community structure and function has been examined in detail in natural and engineered environments, but little work has been done on using microbial community information to predict function. We processed microbial community and operational data from controlled experiments with bench-scale bioreactor systems to predict reactor process performance. Four membrane-operated sequencing batch reactors treating synthetic wastewater were operated in two experiments to test the effects of (i) the toxic compound 3-chloroaniline (3-CA) and (ii) bioaugmentation targeting 3-CA degradation, on the sludge microbial community in the reactors. In the first experiment, two reactors were treated with 3-CA and two reactors were operated as controls without 3-CA input. In the second experiment, all four reactors were additionally bioaugmented with a Pseudomonas putida strain carrying a plasmid with a portion of the pathway for 3-CA degradation. Molecular data were generated from terminal restriction fragment length polymorphism (T-RFLP) analysis targeting the 16S rRNA and amoA genes from the sludge community. The electropherograms resulting from these T-RFs were used to calculate diversity indices – community richness, dynamics and evenness – for the domain Bacteria as well as for ammonia-oxidizing bacteria in each reactor over time. These diversity indices were then used to train and test a support vector regression (SVR) model to predict reactor performance based on input microbial community indices and operational data. Considering the diversity indices over time and across replicate reactors as discrete values, it was found that, although bioaugmentation with a bacterial strain harboring a subset of genes involved in the degradation of 3-CA did not bring about 3-CA degradation, it significantly affected the community as measured through all three diversity indices in both the general bacterial community and the ammonia-oxidizer community (α = 0.5). The impact of bioaugmentation was also seen qualitatively in the variation of community richness and evenness over time in each reactor, with overall community richness falling in the case of bioaugmented reactors subjected to 3-CA and community evenness remaining lower and more stable in the bioaugmented reactors as opposed to the unbioaugmented reactors. Using diversity indices, 3-CA input, bioaugmentation and time as input variables, the SVR model successfully predicted reactor performance in terms of the removal of broad-range contaminants like COD, ammonia and nitrate as well as specific contaminants like 3-CA. This work was the first to demonstrate that (i) bioaugmentation, even when unsuccessful, can produce a change in community structure and (ii) microbial community information can be used to reliably predict process performance. However, T-RFLP may not result in the most accurate representation of the microbial community itself, and a much more powerful prediction tool can potentially be developed using more sophisticated molecular methods.

Effect of bioaugmentation to enhance phytoremediation for removal of phenanthrene and pyrene from soil with Sorghum and Onobrychis sativa.

The use of plants to remove Poly-aromatic-hydrocarbons (PAHs) from soil (phytoremediation) is emerging as a cost-effective method. Phytoremediation of contaminated soils can be promoted by the use of adding microorganisms with the potential of pollution biodegradation (bioaugmentation). In the present work, the effect of bacterial consortium was studied on the capability of Sorghum and Onobrychis sativa for the phytoremediation of soils contaminated with phenanthrene and pyrene. 1.5 kg of the contaminated soil in the ratio of 100 and 300 mg phenanthrene and/or pyrene per kg of dry soil was then transferred into each pot (nine modes). The removal efficiency of natural, phytoremediation and bioaugmentation, separately and combined, were evaluated. The samples were kept under field conditions, and the remaining concentrations of pyrene and phenanthrene were determined after 120 days. The rhizosphere as well as the microbial population of the soil was also determined. Results indicated that both plants were able to significantly remove pyrene and phenanthrene from the contaminated soil samples. Phytoremediation alone had the removal efficiency of about 63% and 74.5% for pyrene and phenanthrene respectively. In the combined mode, the removal efficiency dramatically increased, leading to pyrene and phenanthrene removal efficiencies of 74.1% and 85.02% for Onobrychis sativa and 73.84% and 85.2% for sorghum, respectively. According to the results from the present work, it can be concluded that Onobrychis sativa and sorghum are both efficient in removing pyrene and phenanthrene from contamination and bioaugmentation can significantly enhance the phytoremediation of soils contaminated with pyrene and phenanthrene by 22% and 16% respectively.

Biodegradation of Spilled Diesel Fuel in Agricultural Soil: Effect of Humates, Zeolite, and Bioaugmentation

Possible enhancement of biodegradation of petroleum hydrocarbons in agricultural soil after tank truck accident (~5000 mg/kg dry soil initial concentration) by bioaugmentation of diesel degrading Pseudomonas fluorescens strain and addition of abiotic additives (humates, zeolite) was studied in a 9-month pot experiment. The biodegradation process was followed by means of analytical parameters (hydrocarbon index expressed as content of C10–C40 aliphatic hydrocarbons, ratio pristane/C17, and total organic carbon content) and characterization of soil microbial community (content of phospholipid fatty acids (PLFA) as an indicator of living microbial biomass, respiration, and dehydrogenase activity). The concentration of petroleum hydrocarbons (C10–C40) was successfully reduced by ~60% in all 15 experiment variants. The bioaugmentation resulted in faster hydrocarbon elimination. On the contrary, the addition of humates and zeolite caused only a negligible increase in the degradation rate. These factors, however, affected significantly the amount of PLFA. The humates caused significantly faster increase of the total PLFA suggesting improvement of the soil microenvironment. Zeolite caused significantly slower increase of the total PLFA; nevertheless it aided in homogenization of the soil. Comparison of microbial activities and total PLFA revealed that only a small fraction of autochthonous microbes took part in the biodegradation which confirms that bioaugmentation was the most important treatment.

Effects of bioaugmentation on enhanced reductive dechlorination of 1,1,1-trichloroethane in groundwater: a comparison of three sites

Microcosm studies investigated the effects of bioaugmentation with a mixed Dehalococcoides (Dhc)/Dehalobacter (Dhb) culture on biological enhanced reductive dechlorination for treatment of 1,1,1-trichloroethane (TCA) and chloroethenes in groundwater at three Danish sites. Microcosms were amended with lactate as electron donor and monitored over 600 days. Experimental variables included bioaugmentation, TCA concentration, and presence/absence of chloroethenes. Bioaugmented microcosms received a mixture of the Dhc culture KB-1 and Dhb culture ACT-3. To investigate effects of substrate concentration, microcosms were amended with various concentrations of chloroethanes (TCA or monochloroethane [CA]) and/or chloroethenes (tetrachloroethene [PCE], trichloroethene [TCE], or 1,1-dichloroethene [1,1-DCE]). Results showed that combined electron donor addition and bioaugmentation stimulated dechlorination of TCA and 1,1-dichloroethane (1,1-DCA) to CA, and dechlorination of PCE, TCE, 1,1-DCE and cDCE to ethane. Dechlorination of CA was not observed. Bioaugmentation improved the rate and extent of TCA and 1,1-DCA dechlorination at two sites, but did not accelerate dechlorination at a third site where geochemical conditions were reducing and Dhc and Dhb were indigenous. TCA at initial concentrations of 5 mg/L inhibited (i.e., slowed the rate of) TCA dechlorination, TCE dechlorination, donor fermentation, and methanogenesis. 1 mg/L TCA did not inhibit dechlorination of TCA, TCE or cDCE. Moreover, complete dechlorination of PCE to ethene was observed in the presence of 3.2 mg/L TCA. In contrast to some prior reports, these studies indicate that low part-per million levels of TCA (< 3 mg/L) in aquifer systems do not inhibit dechlorination of PCE or TCE to ethene. In addition, the results show that co-bioaugmentation with Dhc and Dhb cultures can be an effective strategy for accelerating treatment of chloroethane/chloroethene mixtures in groundwater, with the exception that all currently known Dhc and Dhb cultures cannot treat CA.

Bioremediation assessment of diesel–biodiesel-contaminated soil using an alternative bioaugmentation strategy

This study investigated the effectiveness of successive bioaugmentation, conventional bioaugmentation, and biostimulation of biodegradation of B10 in soil. In addition, the structure of the soil microbial community was assessed by polymerase chain reaction-denaturing gradient gel electrophoresis. The consortium was inoculated on the initial and the 11th day of incubation for successive bioaugmentation and only on the initial day for bioaugmentation and conventional bioaugmentation. The experiment was conducted for 32 days. The microbial consortium was identified based on sequencing of 16S rRNA gene and consisted as Pseudomonas aeruginosa, Achromobacter xylosoxidans, and Ochrobactrum intermedium. Nutrient introduction (biostimulation) promoted a positive effect on microbial populations. The results indicate that the edaphic community structure and dynamics were different according to the treatments employed. CO2 evolution demonstrated no significant difference in soil microbial activity between biostimulation and bioaugmentation treatments. The total petroleum hydrocarbon (TPH) analysis indicated a biodegradation level of 35.7 and 32.2 % for the biostimulation and successive bioaugmentation treatments, respectively. Successive bioaugmentation displayed positive effects on biodegradation, with a substantial reduction in TPH levels.

Bioremediation of highly contaminated oilfield soil: Bioaugmentation for enhancing aromatic compounds removal

This study evaluated the effectiveness of different amendments—including a commercial NPK fertilizer, a humic substance (HS), an organic industrial waste (NovoGro), and a yeast-bacteria consortium—in the remediation of highly contaminated (up to 6% of total petroleum hydrocarbons) oilfield soils. The concentrations of hydrocarbon, soil toxicity, physicochemical properties of the soil, microbial population numbers, enzyme activities and microbial community structures were examined during the 90-d incubation. The results showed that the greatest degradation of total petroleum hydrocarbons (TPH) was observed with the biostimulation using mixture of NPK, HS and NovoGro, a treatment scheme that enhanced both dehydrogenase and lipase activities in soil. Introduction of exogenous hydrocarbon-degrading bacteria (in addition to biostimulation with NPK, HS and NovoGro) had negligible effect on the removal of TPH, which was likely due to the competition between exogenous and autochthonous microorganisms. Nonetheless, the addition of exogenous yeast-bacteria consortium significantly enhanced the removal of the aromatic fraction of the petroleum hydrocarbons, thus detoxifying the soil. The effect of bioaugmentation on the removal of more recalcitrant petroleum hydrocarbon fraction was likely due to the synergistic effect of bacteria and fungi.

Relative effect of bioaugmentation with electrochemically active and non-active bacteria on bioelectrogenesis in microbial fuel cell

Bioelectrogenic activity of microbial fuel cells (MFC) augmented with electrochemically active bacteria (EAB, Pseudomonas aeruginosa) and non-EAB (Escherichia coli) as biocatalysts was investigated. Anodic microflora augmented with P. aeruginosa (AMFCP) yielded higher electrogenic activity (418 mV; 3.87 mA) than E. coli (AMFCE; 254 mV; 1.67 mA) and non-augmented native microflora (MFCC; 235 mV; 1.37 mA). Higher redox currents along with lower Tafel-slopes were observed with AMFCP operation compared to AMFCE and MFCC due to manifestation of bioaugmentation thereby minimizing the losses. A fourfold and twofold increase in capacitance and exchange current was observed with AMFCP and AMFCE operation respectively, when compared to MFCC. Tracking of augmented biocatalyst by fluorescent in situ hybridization (FISH) with defined probes documented the survivability of Pseudomonas sp. in higher numbers than Enterobacteriaceae. Study corroborated enhanced electron transfer capability of mixed consortia owing to the synergistic interaction with EAB due to augmentation.

The effect of soil bioaugmentation with strains of Pseudomonas on Cd, Zn and Cu uptake by Sinapis alba L.

The aim of this study was to assess the ability of selected metal resistant strains of the Pseudomonas genus to increase Zn, Cd and Cu uptake by the metalophyte Sinapis alba L. under laboratory conditions. Moreover, the mechanisms of the plant growth promotion in the tested strains and their impact on the shoots and roots of white mustard biomass were examined. Soil inoculation with the tested strains resulted in higher concentrations of Zn, Cd and Cu in the shoots and roots of the plants in comparison with those grown in non-inoculated soil. The highest phytoextraction enhancement was caused by Pseudomonas fluorescens MH15 which increased Zn, Cd and Cu accumulation in shoot tissue by 60%, 96% and 31%, respectively, in comparison with control plants. Moreover, all the tested strains also exhibited a significant increase of Cd translocation from roots to shoots of the white mustard. Three Pseudomonas putida (MH3, MH6, MH7) and two P. fluorescens biotype G and C (MH9 and MH15, respectively) strains had the ability to produce siderophore, 1-amino-cyclopropane-1-carboxylic acid deaminase, indole 3-acetic acid as well as hydrocyanic acid. Additionally, P. putida strains were also capable of solubilizing inorganic phosphate. The ability of the tested strains to increase the metal uptake in white mustard and their plant growth-promoting properties make them good candidates for supporting heavy metal phytoextraction as well as for plant growth promoting.

Research for Biodegradation and Bioaugmentation of Drilling Wastewater

The paper studied the degradation rate of single strain, the microorganisms agent compatibility and the bioaugmentation effects of the activated sludge system. The results showed that 10 strains screened from drilling site were able to degrade drilling wastewater. Confirm the optimal ratio of strains’ compatibility through orthogonal experiment. In augmented experiments, it showed that in the control SBR system with the COD of the effluent was in three different average levels (with two load shock), the COD degradation rates were 21.4%, 22.8% and 6.9%. In the augmented system treated with the same effluent, the degradation rates of augmented system were 64.8%, 62.78% and 66.9% respectively. It showed that the activated sludge was augmented by the mixed cultures which made the system to be more stable and improve impact resistance.

Comparative assessment of bioremediation approaches to highly recalcitrant PAH degradation in a real industrial polluted soil

High recalcitrant characteristics and low bioavailability rates due to aging processes can hinder high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) bioremediation in real industrial polluted soils. With the aim of reducing the residual fraction of total petroleum hydrocarbons (TPH) and (HMW-PAHs) in creosote-contaminated soil remaining after a 180-d treatment in a pilot-scale biopile, either biostimulation (BS) of indigenous microbial populations with a lignocellulosic substrate (LS) or fungal bioaugmentation with two strains of white-rot fungi (WRF) (i.e., Trametes versicolor and Lentinus tigrinus) were comparatively tested. The impact of bivalent manganese ions and two mobilizing agents (MAs) (i.e., Soybean Oil and Brij 30) on the degradation performances of biostimulated and bioaugmented microcosms was also compared. The results reveal soil colonization by both WRF strains was clearly hampered by an active native soil microbiota. In fact, a proper enhancement of native microbiota by means of LS amendment promoted the highest biodegradation of HMW-PAHs, even of those with five aromatic rings after 60 days of treatment, but HMW-PAH-degrading bacteria were specifically inhibited when non-ionic surfactant Brij 30 was amended. Effects of bioaugmentation and other additives such as non-ionic surfactants on the degrading capability of autochthonous soil microbiota should be evaluated in polluted soils before scaling up the remediation process at field scale.

Effects of Biostimulation and Bioaugmentation on The Degradation of Pyrene in Soil

Petroleum based products have been widely used as a source of energy for centuries. One of the main petroleum hydrocarbons of concern is Polycyclic Aromatic Hydrocarbon (PAHs) which include pyrene. Pyrene is a four ring PAHs commonly found in soils contaminated with petroleum based products. The effectiveness of the addition of nutrient (biostimulation) and Mycobacterium sp. (bioaugmentation) on biodegradation of pyrene in soil was evaluated. The addition of nutrients (biosimulation) and microorganisms (bioaugmentation) increased the number of viable cells over the control during the bioremediation process. The cell number increased by 40, 70, 59 and 132 fold for the control, biosimulation, bioaugmentation and combined bioaugmentation, respectively. A lag period of 0.5 d and a specific growth rate of 0.896 d-1 were observed with the combined biosimulation-bioaumentation treatment. The temperature results showed that the temperature of the combined biostimulation-bioaugmentation reached 41°C after two days of treatment while the maximum temperature of the control, biostimulation and bioaugmentation were within the range of 28-32°C. The moisture content decreased for all treatments reaching 45-57% but remained within the optimum range of 40-60% for bioremediation process. This was due to the fact that the moisture lost in the exhaust gas was not compensated by the water produced as a by-product of the organic matter degradation. The level of pyrene degradation was indicated by the decline in O2 concentration and the increase in CO2 concentration in the exhaust gas. The control, biostimulation and bioaugmentation treatments showed similar patterns of decreasing O2 and increasing CO2. However, the combined biostimulation-bioaugmentation treatment recorded a declining trend in O2 concentration and increasing trend in CO2 concentration in the exhaust gas at the beginning of experiment (first 7 days) followed by increasing trend in O2 concentration and decreasing trend in CO2concentration in the next 8 days of the experiment. The highest pyrene reduction in percentage (84.29%) was obtained through the combined bioaugmentation-biostimulation process followed by bioaugmentation (57.86%), biostimulation (50%) and control (37%) processes. Different pyrene degradation rates were observed during the various phases of microbial growth (lag, exponential and stationary) of combined bioaugmentation-biostimulation treatment.

Vermicomposting of Vegetable and Fruit Wastes—Effects of Bioaugmentation on Process Parameters and Manural Value of Composts

Vermicomposting of Vegetable and Fruit Wastes—Effects of Bioaugmentation on Process Parameters and Manural Value of Composts

Field demonstration of bioaugmentation in trichloroethene-contaminated groundwater

A pilot test was conducted to evaluate the effectiveness of bioaugmentation. Dechlorinating consortium in which the dominant microorganisms were Dehalococcoides species (DHC) possessing the vinyl chloride reductase gene (vcrA). The pilot test consisted of a direct injection system, including 2 injection wells. One injection well was for bioaugmentation, and the other, located approximately 20 m away, was for biostimulation. TCE was rapidly dechlorinated to cis-DCE in both wells. The first indication of reduction beyond cis-DCE and VC was the occurrence of ethene 63 days after bioaugmentation in the augmented injection well (AIW). In conjunction with the ethene production, the concentrations of the DHC-16S rRNA gene and the vcrA increased to approximately 106 copies/mL. By day 119, the number of copies of those genes remained high in the AIW, and all chloroethenes declined to levels below the Environmental Quality Standards for Groundwater Pollution in Japan. Though the concentration of indigenous DHC also increased to approximately 106 copies/mL 182 days after injection of nutrients in stimulated injection well, the concentration of cis-DCE and VC remained high until 371 days. These results confirmed that bioaugmentation contributed to shortening the clean-up time better than biostimulation by increasing the initial DHC population in the groundwater.

Rhizodegradation of petroleum hydrocarbons by Sesbania cannabina in bioaugmented soil with free and immobilized consortium

The present study reports the effect of bioaugmentation by free and immobilized bacterial culture on the rhizodegradation of petroleum-polluted soil using Sesbania cannabina plant. Total petroleum hydrocarbon (TPH), hydrocarbon-degrading bacterial counts, microbial activity and root morphology were assessed during 120 days of plant growth. TPH concentration analyzed by GC–MS showed that bioaugmentation did not improve the TPH degradation. TPH concentration decreased from 2541mgkg−1 to 673mgkg−1 and 867mgkg−1 in the rhizosphere of free (FR) and immobilized bacterial inoculated (IR) soil, respectively at the 120th day while in the rhizosphere of uninoculated soil (CR) concentration decreased to 679mgkg−1 only at the 90th day, showing higher and rapid rhizodegradation with indigenous bacteria than bioaugmented bacterial cultures. Various predominant bacterial groups responsible for higher TPH degradation in the rhizosphere of S. cannabina were identified by PCR–DGGE analysis. It is concluded that natural plant-microbe interaction in the rhizosphere of S. cannabina was efficient enough to degrade TPH and plant rhizosphere keeps bacterial community in its surrounding therefore immobilized culture had no obvious effect on petroleum degradation.

Effect of fertilizer formulation and bioaugmentation on biodegradation and leaching of crude oils and refined products in soils

The effects of soil characteristics and oil types as well as the efficacy of two fertilizer formulations and three bioaugmentation packages in improving the bioremediation of oil-contaminated soils were assessed as a means of ex situ treatment selection and optimization through seven laboratory microcosm studies. The influence of bioremediation on leaching of oil from the soil was also investigated. The studies demonstrated the benefits of biostimulation to overcome nutrient limitation, as most of the soils were nutrient depleted. The application of both liquid and pelleted slow-release N and P fertilizers increased both the hydrocarbon biodegradation rates (by a factor of 1.4 to 2.9) and the percentage of hydrocarbon mass degraded (by>30% after 12 weeks and 80% after 37 weeks), when compared with the unamended soils. Slow-release fertilizers can be particularly useful when multiple liquid applications are not practical or cost-effective. Bioaugmentation products containing inoculum plus fertilizer also increased biodegradation by 20% to 37% compared with unamended biotic controls; however, there was no clear evidence of additional benefits due to the inocula, compared with fertilizer alone. Therefore biostimulation is seen as the most cost-effective bioremediation strategy for contaminated soils with the levels of crude oil and refined products used in this study. However, site-specific considerations remain essential for establishing the treatability of oil-contaminated soils.

유류오염지역 정화를 위한 슬러핑과 미생물증진법의 효율평가에 관한 현장 적용성 연구

This study was conducted to evaluate the slurping process affecting the variation of free product and VOCs concentration and the bioaugmentation effect on bioremediation process. Free products and soil gas were extracted from 30 extraction wells installed in a petroleum contaminated area. The extraction system was operated for 10 hours per day with 1 hour on-and-off mode. The thickness of free product in extraction well was decreased from 11.7 cm to 4.5 cm and the VOCs concentration was increased from 10.37 ppm to 30.78 ppm during the operation period. After the slurping process for 2 months, contaminated soil was treated with bioremediation process in 2 cells, <TEX>$15{\times}40$</TEX> m, biologically enhanced with adjusting oxygen, moisture and nutrients concentration. Total 1,400 L of microbial inoculant, Naturesys. (Dong Myung Ent. Co.) was added to the pile B, which has an outstanding ability for degrading petroleum hydrocarbons. The results showed that bioremediaton effect in soil with the microorganisms solution is 33% higher than that in soil with only residual bacteria.

Impacts of organic carbon availability and recipient bacteria characteristics on the potential for TOL plasmid genetic bioaugmentation in soil slurries

The effectiveness of genetic bioaugmentation relies on efficient plasmid transfer between donor and recipient cells as well as the plasmid’s phenotype in the recipient cell. In the present study, the effects of varying organic carbon substrates, initial recipient-to-donor cell density ratios, and mixtures of known recipient bacterial strains on the conjugation and function of a TOL plasmid were tested in sterile soil slurry batch reactors. The presence of soil organic carbon was sufficient in ensuring TOL plasmid transconjugant occurrence (up to 2.1±0.5%) for most recipient strains in soil slurry batch mating experiments. The addition of glucose had limited effects on transconjugant occurrence; however, glucose amendment increased the specific toluene degradation rates of some Enterobacteriaceae transconjugants in soil slurry. Initial cell density ratios and mixtures of recipient strains had smaller impacts on plasmid conjugation and resulting phenotype functionality. These observations suggest that genetic bioaugmentation may be improved by minimal altering of environmental conditions.