Sparging System Research Articles

High-Titer Recombinant Adenovirus 26 Vector GMP Manufacturing in HEK 293 Cells with a Stirred Single-Use Bioreactor for COVID-19 Vaccination Purposes.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 virus) pandemic has shown the importance of pursuing various vaccine manufacturing strategies. In the present study, the HEK 293 cells were infected with recombinant adenovirus serotype 26 (rAd26), and the effects of critical process parameters (CPPs) including viable cell density (VCD) at infection time (0.5 × 106, 0.8 × 106, 1.4 × 106, 1.8 × 106, and 2.5 × 106 cells/mL), the multiplicity of infection (MOI) = 3, 6, 9, 12, and 15, and two aeration strategies (high-speed agitation with a sparging system and low-speed agitation with an overlay system) were investigated experimentally. The results of small-scale experiments in 2 L shake flasks (SF 2L) demonstrated that the initial VCD and MOI could affect the cell proliferation and viability. The results at these experiments showed that VCD = 1.4 × 106 cells/mL and MOI = 9 yielded TCID50 /mL = 108.9, at 72 h post-infection (hpi), while the virus titer at VCD = 0.5 × 106 and 0.8 × 106 cells/mL was lower compared to that of VCD = 1.4 × 106 cells/mL. Moreover, our findings showed that VCDs > 1.8 × 106 cells/m with MOI = 9 did not have a positive effect on TCID50 /mL and MOI = 3 and 6 were less efficient, whereas MOI > 12 decreased the viability drastically. In the next step, the optimized CPPs in a small scale were exploited in a 200 L single-use bioreactor (SUB), with good manufacturing practice (GMP) conditions, at RPM = 25 with an overlay system, yielding high-titer rAd26 manufacturing, i.e., TCID50/mL = 108.9, at 72 hpi.

Comparing and contrasting In-Vial and full-scale systems for sparging volatile analytes

In-vial sparging was demonstrated as an effective, practical alternative to a full-scale sparging system for supporting the analysis of volatile constituents. Using elemental mercury (Hg0) and toluene as representative purgeable analytes, the mass removal for various sparge configurations was measured and a reduced order model was developed and validated. In the primary experiments, Hg0 in the sparge gas was trapped on activated carbon or gold, thermally desorbed, and quantified using atomic absorption or atomic fluorescence spectroscopy. Toluene experiments using the same in-vial sparge apparatus and sparge parameters were performed to demonstrate the applicability of the reduced order model to a broad range of compounds. Toluene removal was tracked by measuring the remaining toluene in sparged aliquots using Ultraviolet-visible (UV–Vis) spectroscopy. For the sparging, flow rates varied from 25 to 75 mL/min for periods from 0 to 30 min. Sparge performance, mass removal as a function of time, and sparge gas volume were measured for both in-vial and full-scale systems. A model based on dimensionless Henry's Law coefficient, normalized sparge gas volume, and fractional extent of equilibrium matched the experimental data for both compounds and provides a practical tool for future applications. For the conditions tested in this study, the calibrated model indicated that the sparge gas in the in-vial system reached approximately 33% of its equilibrium value before exiting the water surface, while a full-scale system reached approximately 100%. The tests validated the quality, reproducibility, and predictability of sparging performance for both full scale and in-vial sparge systems. Related factors such as waste generation, worker risk, and labor were also assessed. Full scale sparge systems provide the advantage of lower detection levels due to larger sample volume, while the in-vial sparge systems provide advantages for most other factors; including automatability, reducing secondary wastes, lessening the need to clean and check the sparge apparatus, and lowering labor and costs. The data and associated reduced order model support continued development and deployment of in-vial sparge platforms as a practical option for analysis of purgeable analytes such as volatile organic compounds and volatile metals/organometallics.

Large-scale spatial characterization and liquefaction resistance of sand by hybrid bacteria induced biocementation

Microbially induced calcite precipitation (MICP) has received greater attention of geotechnical engineers recently as a potentially effective and sustainable approach for biocementation of sands. Present study investigates spatial variability and synergistic effects of bacterial hybrids of Sporosarcina (S.) pasteurii and Bacillus (B.) sphaericus for sand biocementation which is important to explore to stimulate real field conditions where multiple urease producing can be present in soil environment. Large-scale testing was conducted in rectangular tank (135 cm × 113 cm × 65 cm) filled with Narmada sand (1.21 Ton), treated using bio-chem distribution system consisting of bioreactor, chemical mixer, circulation tank, injection pipes, treatment tank, and drainage outlets. The design of bioreactor and slotted injection pipes are the major novel aspect of this study for on-site bacterial cultivation and uniform calcite precipitation throughout the treatment depth to increase liquefaction resistance of sand which was not investigated in previous large-scale testing studies. Bacterial hybrid was first cultivated, then inoculum of 10 L was prepared, and finally, 200 L of bacterial solution was cultivated in bioreactor. Sand was bioaugmented with hybrid bacteria in tank, subsequently injected 0.50 M urea and cementation solution periodically up to 8 days. Biosparging was also implemented for 10–12 h daily using air pumps to ensure aerobic conditions. During the treatment, pH, electrical conductivity (EC), and total dissolved solids (TDS) were measured periodically as indicators of biogeochemical reactions occurring during biotreatment. Dynamic cone penetration tests (DCPTs) were performed and DCPT-blows up to 30 cm depth were measured at 20 locations. Contours of dynamic cone penetration index (DCPI) and calcite precipitation were used to assess spatial variability of biocementation. Average DCPT blow count for untreated sand was 5, but it increased up to 50 with 10.6% calcite content, for 30 cm penetration. The DCPT results showed significant improvement in liquefaction resistance. Biocemented samples were collected from various locations to measure calcite content and conduct SEM. Overall, the large-scale testing showed effective and substantial biocementation of sand using the cultivated hybrid bacteria and bio-chem distribution/air sparging system developed in this study. The spacing of injection points and the amounts of injection biotreatment solutions can be optimized to achieve uniform, adequate, and cost-effective biotreatment under actual field applications.

Distribution of a Sulfolane-Metabolizing Rhodoferax sp. Throughout a Contaminated Subarctic Aquifer and Two Groundwater Treatment Systems.

An extensive plume of the emerging contaminant sulfolane has been found emanating from a refinery in Interior Alaska, raising questions about the microbial potential for natural attenuation and bioremediation in this subarctic aquifer. Previously, an aerobic sulfolane-assimilating Rhodoferax sp. was identified from the aquifer using stable isotope probing. Here, we assessed the distribution of known sulfolane-assimilating bacteria throughout the contaminated subarctic aquifer using 16S-rRNA-amplicon analyses of ~100 samples collected from groundwater monitoring wells and two groundwater treatment systems. One treatment system was an in situ air sparging system where air was injected directly into the aquifer. The other was an ex situ granular activated carbon (GAC) filtration system for the treatment of private well water. We found that the sulfolane-assimilating Rhodoferax sp. was present throughout the aquifer but was significantly more abundant in groundwater associated with the air sparge system. The reduction of sulfolane concentrations combined with the apparent enrichment of sulfolane degraders in the air sparging zone suggests that the addition of oxygen facilitated sulfolane biodegradation. To investigate other environmental controls on Rhodoferax populations, we also examined correlations between groundwater geochemical parameters and the relative abundance of the Rhodoferax sp. and found only manganese to be significantly positively correlated. The sulfolane-assimilating Rhodoferax sp. was not a major component of the GAC filtration system, suggesting that biodegradation is not an important contributor to sulfolane removal in these systems. We conclude that air sparging is a promising approach for enhancing the abundance and activity of aerobic sulfolane-degraders like Rhodoferax to locally stimulate sulfolane biodegradation in situ.

Effect of surfactants on mass transfer in a bubble column equipped with a horizontal tube bundles

Abstract The influence of sodium lauryl sulfate (anionic surfactant) on the solid- liquid mass transfer coefficient in a gas sparging system prepared with a tube bundles is considered. Diffusion - controlled dissolution approach of copper in acidified dichromate solution was employed. Parameters examined are the concentration of surfactant, superficial gas velocity and the number of actively exposed tube bundles (ranging from 1–5). The presence of surfactant decreased the mass transfer coefficient by an extent ranges from 13 to 46% contingent on the concentration of surfactant. The governing parameters are interrelated by a dimensionless correlation and an approach was suggested to use it in design, scale up and predicting the performance of the gas sparged tube bundle under various conditions. The benefits and shortcomings of using surfactants in bubble columns are discussed in terms of energy conservation and reduction in mass transfer, respectively.

The Limerick bubbly flow rig: Design, performance, hold-up and mixing pattern

As Euler-Euler CFD simulations of bubbly flows suffer from uncertainties due to the many underpinning models, there is an obvious need of accurate experimental data for validation. With this in mind, a new bubbly flow test rig was built to be operated with and without liquid co-flow, with bubble size as uniform as possible in the range 4–7mm, and with a very even horizontal bubble distribution. We designed the gas sparging system such that we can also produce an essentially bi-modal bubble size distribution. The column consists of two square sections to allow for studying the mixing of two originally separated bubbly flows with either the same or a different bubble size. The bubbles are produced from 2×196 needles, bubble sizes are determined with high-speed imaging and with a simple acoustical method, overall volume fractions in the column by means of air chamber pressure measurements. Overall volume fractions are presented as a function of gas and liquid flow rates, with slip velocity mostly increasing with increasing void fraction. First results are obtained on (a) producing bi-model bubble size distributions and the pertinent volume fractions in the column, and (b) flow patterns in the case of unequal aeration.

Concomitant production of fatty acid methyl ester (biodiesel) and exopolysaccharides using efficient harvesting technology in flat panel photobioreactor with special sparging system via Scenedesmus abundans

Current study focusses on the concomitant production of fatty acid methyl ester (FAME, biodiesel) and exopolysaccharides (EPS) from Scenedesmus abundans cell factory in flat panel photobioreactor using cost effective harvesting strategy. Parallel mini and medium scale flat panel photobioreactors (PBRs) with special gas sparging system enabling high gas to liquid mass transfer and efficient mixing were designed. Biomass titer of 6.9 g/l with overall biomass productivity of 1.2 g/l/day was achieved with constant high light intensity of 2162 µE/m2/s in growth phase (134 h) using optimum nutrient concentration. FAME concentration of 1.53 g/l was achieved after 15 days of nitrogen deprivation condition with productivity of 67 mg/l/day. The EPS production of 236 mg/l with a yield of 37 mg/g biomass was achieved. The strain proved its capability to produce multiproducts simultaneously in a single stage PBR by natural autoflocculation harvesting technology.

Enhancing Groundwater Remediation in Air Sparging by Changing the Pulse Duration

AbstractAn important operation parameter in the design of a pulsed air sparging (PAS) system is the pulse duration (PD). To study the effect of the PD on the remediation process, a series of laboratory experiments and numerical simulations were performed. The experimental apparatus was a cylindrical tank, packed with fine sand and partially filled by water contaminated with toluene. Toluene concentrations in water and in effluent air were measured over time during the application of PAS, which was applied with three different PD. Next, the T2VOC model, an extension of the TOUGH2 simulation program, was used to simulate the two‐phase flow and transport processes for these cases. The simulation model was calibrated to the experimental results, and then run with a range of PD values. Results showed that there exists an optimal PD which yields the highest remediation efficiency. Next, it was shown that this PD may be obtained by performing a PAS pilot test and measuring the groundwater pressure response in a monitoring well. The characteristic time which describes the exponential decay of the pressure response was shown to provide an adequate estimate for the optimal PD. The estimation improved by taking a number of injection cycles.

Biological Co-existence of the Microalgae – Bacteria System in Dairy Wastewater using photo-bioreactor

Aeration system in the cultivation of Chlorella Sp. Microalgae using dairy wastewater as culture media was addressed in the current study. This research aimed to study the effect of aeration in the bubble column bioreactor on the biological synergy between microalgae and bacteria if they are present in the same place. The results show that the sterilization stage is not the dominant step in the success of microalgae cultivation in water-rich organic waste. There is a clear convergence between the growth rate of Chlorella microalgae in the sterilized and non-sterilized culture media, which gives realism if the proposal is applied industrially. Through the information obtained the aerobic bacteria in the non-sterilized media, with free of algae, are able to consume all dissolved oxygen within a very short period of time. The aeration factor is, therefore, important in that case. However, the experiments show that co-existence of bacteria and microalgae can occur even if there is no aeration system. Consequently, the microalgae in the dairy wastewater are capable of preserving the environment of cultivation. The gases produced due to metabolic processes in bacteria or microalgae remain in solution for a certain period and are not easily removed, especially if the solution is exposed to intermittent sparging. Thus, this will give enough time for both microorganisms to consume those gases. However, the results show that the sparging system for 15 minutes and three times a day improves biomass production by 60%. Therefore, the cultivation of microalgae in addition to its desired goal can play an important role in the dairy wastewater treatment units by maintaining the appropriate environment for aerobic bacteria even in the absence of an aeration system.

Outdoor flat-panel membrane photobioreactor to treat the effluent of an anaerobic membrane bioreactor. Influence of operating, design, and environmental conditions.

As microalgae have the ability to simultaneously remove nutrients from wastewater streams while producing valuable biomass, microalgae-based wastewater treatment is a win-win strategy. Although recent advances have been made in this field in lab conditions, the transition to outdoor conditions on an industrial scale must be further investigated. In this work an outdoor pilot-scale membrane photobioreactor plant was operated for tertiary sewage treatment. The effects of different parameters on microalgae performance were studied including: temperature, light irradiance (solar and artificial irradiance), hydraulic retention time (HRT), biomass retention time (BRT), air sparging system and influent nutrient concentration. In addition the competition between microalgae and ammonium oxidising bacteria for ammonium was also evaluated. Maximum nitrogen and phosphorus removal rates of 12.5 ± 4.2 mgN·L-1·d-1 and 1.5 ± 0.4 mgP·L-1·d-1, respectively, were achieved at a BRT of 4.5 days and HRT of 2.5 days, while a maximum biomass productivity of 78 ± 13 mgVSS·L-1·d-1 (VSS: volatile suspended solids) was reached. While the results obtained so far are promising, they need to be improved to make the transition to industrial scale operations feasible.

Heat Transfer and Hydrodynamic in Internal Jacket Airlift Bioreactor with Microbubble Technology

Integration of laminar bubbling flow with heat transfer equations in a novel internal jacket airlift bioreactor using microbubbles technology was examined in the present study. The investigation was accomplished via Multiphysics modelling to calculate the gas holdup, velocity of liquid recirculation, mixing time and volume dead zone for hydrodynamic aspect. The temperature and internal energy were determined for heat transfer aspect.
 The results showed that the concentration of microbubbles in the unsparged area is greater than the chance of large bubbles with no dead zones being observed in the proposed design. In addition the pressure, due to the recirculation velocity of liquid around the draft tube, increased the retention time of microbubbles in the same area. 
 Thus it was expected that their effect on mass and heat transfer phenomena would be positive for biological applications. For example the gas fraction volume of microbubble in the downcomer region is 0.0063, while with fine bubble diameter of 1 mm, this region was free from any bubble. Furthermore, the velocity of liquid in the center of ring diffuser would be 0.175 m/s, if the sparging system operated with bubble diameter of 100 micrometer, whilst would be 0.035 m/s with fine bubble diameter of 1 mm.
 The study also proved the importance of bubble diameter on the heat transfer in gas and liquid phases in the proposed design. Microbubbles gave greater responsiveness to stability and homogeneity in all parts of the bioreactor. Finally, this study concluded the efficiency of the proposed design with the microbubbles technology thermally and hydrodynamically.

Applying short-duration pulses as a mean to enhance volatile organic compounds removal by air sparging

Application of short-duration pulses of high air pressure, to an air sparging system for groundwater remediation, was tested in a two-dimensional laboratory setup. It was hypothesized that this injection mode, termed boxcar, can enhance the remediation efficiency due to the larger ZOI and enhanced mixing which results from the pressure pulses. To test this hypothesis, flow and transport experiments were performed.Results confirm that cyclically applying short-duration pressure pulses may enhance contaminant cleanup. Comparing the boxcar to conventional continuous air-injection shows up to a three-fold increase in the single well radius of influence, dependent on the intensity of the short-duration pressure-pulses. The cleanup efficiency of Toluene from the water was 95% higher than that achieved under continuous injection with the same average conditions.This improvement was attributed to the larger zone of influence and higher average air permeability achieved in the boxcar mode, relative to continuous sparging. Mixing enhancement resultant from recurring pressure pulses was suggested as one of the mechanisms which enhance the contaminant cleanup.The application of a boxcar mode in an existing, multiwell, air sparging setup can be relatively straightforward: it requires the installation of an on-off valve in each of the injection-wells and a central control system. Then, turning off some of the wells, for a short-duration, result in a stepwise increase in injection pressure in the rest of the wells. It is hoped that this work will stimulate the additional required research and ultimately a field scale application of this new injection mode.

Cultivation of Chlorella Vulgaris Using Airlift Photobioreactor Sparged with 5%CO 2 -Air as a Biofixing Process

The present paper addresses cultivation of Chlorella vulgaris microalgae using airlift photobioreactor that sparged with 5% CO 2 /air. The experimental data were compared with that obtained from bioreactor aerated with air and unsparged bioreactor. The results showed that the concentration of biomass is 0.36 g l -1 in sparged bioreactor with CO2/air, while, the concentration of biomass reached to 0.069 g l -1 in the unsparged bioreactor. They showed also that aerated ioreactor.with CO2/air gives more biomass production even the bioreactor was aerated with air. This study proved that application of sparging system for ultivation of Chlorella vulgaris microalgae using either CO2/air mixture or air has a significant growth rate, since the bioreactors become more thermodynamically favorable and provide impetus for a higher level of production. biofixing process

An Air-well sparging minifermenter system for high-throughput protein production

Over the last few years High-Throughput Protein Production (HTPP) has played a crucial role for functional proteomics. High-quality, high yield and fast recombinant protein production are critical for new HTPP technologies. Escherichia coli is usually the expression system of choice in protein production thanks to its fast growth, ease of handling and high yields of protein produced. Even though shake-flask cultures are widely used, there is an increasing need for easy to handle, lab scale, high throughput systems. In this article we described a novel minifermenter system suitable for HTPP. The Air-Well minifermenter system is made by a homogeneous air sparging device that includes an air diffusion system, and a stainless steel 96 needle plate integrated with a 96 deep well plate where cultures take place. This system provides aeration to achieve higher optical density growth compared to classical shaking growth without the decrease in pH value and bacterial viability. Moreover the yield of recombinant protein is up to 3-fold higher with a considerable improvement in the amount of full length proteins. High throughput production of hundreds of proteins in parallel can be obtained sparging air in a continuous and controlled manner. The system used is modular and can be easily modified and scaled up to meet the demands for HTPP.

Bioavailability of slow-desorbable naphthalene in a biological air sparging system

The bioavailability of sorbed organic contaminants is one of the most important factors used to determine their fate in the environment. This study was conducted to evaluate the bioavailability of slow-desorbable naphthalene in soils. An air sparging system was utilized to remove dissolved (or desorbed) naphthalene continuously and to limit the bacterial utilization of dissolved naphthalene. A biological air sparging system (air sparging system with bacteria) was developed to evaluate the bioavailability of the slow-desorption fraction in soils. Three different strains (Pseudomonas putida G7, Pseudomonas sp. CZ6 and Burkholderia sp. KM1) and two soils were used. Slow-desorbable naphthalene continuously decreased under air sparging; however, a greater decrease was observed in response to the biological air sparging system. Enhanced bioavailability was not observed in the Jangseong soil. Overall, the results of this study suggests that the removal rate of slow-desorbable contaminants may be enhanced by inoculation of degrading bacteria into an air sparging system during the remediation of contaminated soils. However, the enhanced bioavailability was found to depend more on the soil properties than the bacterial characteristics.

Centrifuge Modeling and Numerical Simulation of Air Sparging Process

Air sparging (AS) is one of the in-situ groundwater remediation techniques for remediating volatile organic compounds (VOCs) contaminated soil, and the knowledge of air flow features is essential in designing air sparging system for soil remediation. The centrifuge modeling technique was employed to simulate the in-situ conditions and to investigate air follow characteristics during air sparging by using glass beads as soils. Several centrifugal modeling tests were performed under various g-levels. According to the test results, the zone of influence (ZOI) during air sparging is in a truncated-cone shape under various g-levels, which can be expressed by the lateral expansion around the air injection point and the cone angle between the vertical axis and the boundary of ZOI. A 2D numerical model is used to model the air movement during air sparging process. The ZOI and the water saturation distribution were obtained. The results agree well with the centrifuge test data, which indicates the two phase flow model is reasonable to simulate the air sparging process. It was also shown that air compressibility and buoyant force have a significant influence on the extent of ZOI and should be adequately considered. Hence centrifuge modeling and numerical simulation can be used as a design tool for in-situ air sparging system

Microscopic Modeling of Air Migration during Air Sparging

Air sparging is an emerging soil remediation method to decontaminate saturated granular soils and groundwater with volatile organic compounds (VOCs). The efficiency of an in situ sparging system is controlled by the extent of the contact between injected air and contaminated soil and pore fluid. Characterizing the mechanisms governing the movement of air through saturated porous media is therefore critical to the design of an effective cleanup treatment system. In this paper, an overview of the existing conceptual models and related microscopic research on air sparging is provided. Then, main issues associated with microscopic modeling of air sparging, including simulation of microstructure of porous medium, migration of fine particles along the air flow path, air flow pattern transition criteria, and critical size of air bubbles or clusters are discussed. Finally, three-dimensional (3D) networks of pore bodies connected by pore throats representing the main skeleton of the pore structure of porous media are recommended as the prototype of a pore-scale model to account for these irregularities in channel geometry. Methods used in constructing a 3D network are briefly summarized. According to the air-water two-phase flow theory, the transition criteria between two flow patterns observed during air sparging tests—bubbly flow and channelized flow—are discussed. The manuscript also discusses the critical size of a bubble or a bubble cluster during air sparging in a given soil. A method to estimate the critical size of a bubble or a bubble cluster in a 3D network model is suggested. Hence, this paper lays a basis for microscopic research on air spatial distribution, air saturation, air flow pattern transition, and air flow rate during the air sparging.

Multiphase Flow Fields in In-situ Air Sparging and its Effect on Remediation

In-situ air sparging (IAS) is used for the clean-up of soil and groundwater that are contaminated with volatile organic compounds in relatively permeable subsurface environments. In this study, we investigated the secondary groundwater and gas flow fields that develop in the vicinity of single and multiple air sparging wells. The purpose is to evaluate their effects on contaminant plume migration and thus, remediation. Governing equations describing multiphase flow and contaminant transport in a three-dimensional domain were formulated and solved using the Galerkin finite element technique. Trichloroethylene was selected as a target contaminant. The increase in air injection contributed to an increase in the size of the IAS cone of influence and the gas saturation levels within the cone. This reduced the groundwater velocity within the cone and increased the zone of detour of groundwater around the air sparging wells. This outcome was quantified and compared under several IAS operations. Different soil permeability characteristics also affected the groundwater and gas flow patterns, and this impacted the remedial performance of the IAS system. Under high ambient groundwater velocity, an air sparging system that uses a single injection well caused the detour of contaminant plumes around injection wells, regardless of air injection rates, and failed to meet the remedial goal specified here. This system was successful for relatively low ambient groundwater velocity environments used here. An IAS system with multiple injection wells was effective in capturing and remediating the detoured contaminant plume, and showed superior performance when compared to a single injection well IAS system. Using IAS simulation, we also analyzed the impact of injection rates on site remediation using single or multiple wells. Design criteria that are based on the results of this study would be useful in enhancing the performance of the IAS systems.

In-well air sparging efficiency in remediating the aquifer of a petroleum refinery site

Air sparging represents an innovative groundwater remediation technology, which has been proved to be capable of restoring aquifers that have been polluted by volatile and (or) biodegradable contaminants, such as petroleum hydrocarbons. This paper presents the design, the installation, and the pulsed operation of an in-well air sparging system at the site of a Greek petroleum refinery. The geographical position, the hydrologeoly, and the contamination features of the chosen study area develop special conditions that, along with the fact that the existing refinery is still active, greatly determine the applicability and the effectiveness of the specific technology. The area that was used for the application of the technology covered almost 600 m2 and included five air injection wells and four additional monitoring wells. The pulsed operation of the installed system lasted about 5 months and the results of frequent groundwater sampling and analysis indicate an important decline in total petroleum hydrocarbons (TPH) and benzene–toluene–ethylbenzene–xylene (BTEX) concentrations (up to 99%). However, prior to any attempt to expand the application of air sparging within the facilities of the refinery, special attention should be given to the eccentricities of the site and the ability of the technology to confront more persistent contaminants, such as methyl tertiary-butyl ether (MTBE).

Comparison of Two Methods for Assessment of In Situ Jet-fuel Remediation Efficiency

In 1997, total petroleum hydrocarbon (TPH) remediation started at a former Air Force Base, which operated from 1940 to 1991. TPH had been released to soil and groundwater at the site by military activities. The TPH was 70% jet fuel and the affected area covered 28 ha. Remediation involved a combination of technologies, including removal of volatile organic compounds using soil vapor extraction and air sparging, free product vacuum recovery and aerobic biodegradation of organics with oxygen supplied by the air sparging system, along with nutrient addition. The primary remedial method was found to be biodegradation, which has removed 93% of the contaminants from the site to date. A significant aspect of the remedial action was performance monitoring, including documentation of remediation efficiency. The goal of the research was to assess the relative accuracy of methods commonly used for monitoring in situ TPH remediation. Two such methods were selected for the research: monitoring change in soil TPH concentration (specified as non-polar extractable substances) and monitoring respiration activity in soil with a subsequent stoichiometric mass balance to estimate the mass of TPH destroyed. The study demonstrated that both of the methods provided comparable results regarding the effectiveness of in situ TPH remediation, despite the fact that their methodologies are very different.