Oxygen Release Compound Research Articles

A bench-scale assessment for phosphorus release control of sediment by an oxygen-releasing compound (ORC)

The effects of oxygen-releasing compound (ORC) on the control of phosphorus (P) release as well as the spatial and temporal distribution of P fractions in sediment were studied through a bench-scale test. An ORC with an extended oxygen-releasing capacity was prepared. The results of the oxygen-releasing test showed that the ORC provided a prolonged period of oxygen release with a highly effective oxygen content of 60.6% when compared with powdery CaO2. In the bench-scale test, an ORC dose of 180 g·m−2 provided a higher inhibition efficiency for P release within 50 days. With the application of the ORC, the dissolved oxygen (DO) concentration and redox potential (ORP) of the overlying water were notably improved, and the dissolved total phosphorus (DTP) was maintained below 0.689 mg·L−1 compared to 2.906 mg·L−1 without the ORC treatment. According to the P fractions distribution, the summation of all detectable P fractions in each sediment layer exhibited an enhanced accumulation tendency with the application of ORC. Higher phosphorus retention efficiencies were observed in the second and third layers of sediment from days 10 to 20 with the ORC. Phosphorus was trapped mainly in the form of iron bound P (Fe-P) and organically bound P (O-P) in sediment with the ORC, whereas the effects of the ORC on exchangeable P (EX-P), apatite-associated P (A-P) and detrital P (De-P) in the sediment sample were not significant. The microbial activities of the sediment samples demonstrated that both the dehydrogenase activity (DHA) and alkaline phosphatase activity (APA) in the upper sediment layer increased with the ORC treatment, which indicated that the mineralization of P was accelerated and the microbial biomass was increased. As the accumulation of P suppressed the release of P, the sediment exhibited an increased P retention efficiency with the application of the ORC.

Small scale monitoring of a bioremediation barrier using miniature electrical resistivity tomography

The aim of this study was to assess, in the laboratory, the efficiency of a barrier of oxygen release compound (ORC) to block and divert a diesel plume migration in a scaled aquifer model using miniature electrical resistivity tomography (ERT) as the monitoring system. Two plumes of contaminant (diesel) were injected in a soil model made of local sand and clay. The diesel plumes migration was imaged and monitored using a miniature resistivity array system that has proved to be accurate in soil resistivity variations in small-scaled models of soil. ERT results reflected the lateral spreading and diversion of the diesel plumes in the unsaturated zone. One of the contaminant plumes was partially blocked by the ORC barrier and a diversion and reorganisation of the diesel in the soil matrix was observed. The technique of time-lapse ERT imaging showed that a dense non-aqueous phase liquid (DNAPL) contaminant like diesel can be monitored through a bioremediation barrier and the technique is well suited to monitor the efficiency of the barrier. Therefore, miniature ERT as a small-scale modelling tool could complement conventional techniques, which require more expensive and intrusive site investigation prior to remediation.

Ammonium removal from groundwater using a zeolite permeable reactive barrier: a pilot-scale demonstration.

In situ remediation of ammonium-contaminated groundwater is possible through a zeolite permeable reactive barrier (PRB); however, zeolite's finite sorption capacity limits the long-term field application of PRBs. In this paper, a pilot-scale PRB was designed to achieve sustainable use of zeolite in removing ammonium (NH(4)(+)-N) through sequential nitrification, adsorption, and denitrification. An oxygen-releasing compound was added to ensure aerobic conditions in the upper layers of the PRB where NH(4)(+)-N was microbially oxidized to nitrate. Any remaining NH(4)(+)-N was removed abiotically in the zeolite layer. Under lower redox conditions, nitrate formed during nitrification was removed by denitrifying bacteria colonizing the zeolite. During the long-term operation (328 days), more than 90% of NH(4)(+)-N was consistently removed, and approximately 40% of the influent NH(4)(+)-N was oxidized to nitrate. As much as 60% of the nitrate formed in the PRB was reduced in the zeolite layer after 300 days of operation. Removal of NH(4)(+)-N from groundwater using a zeolite PRB through bacterial nitrification and abiotic adsorption is a promising approach. The zeolite PRB has the advantage of achieving sustainable use of zeolite and immediate NH(4)(+)-N removal.

Ammonium-nitrogen-contaminated groundwater remediation by a sequential three-zone permeable reactive barrier (multibarrier) with oxygen-releasing compound (ORC)/clinoptilolite/spongy iron: column studies.

A novel sequential permeable reactive barrier (multibarrier), composed of oxygen-releasing compound (ORC)/clinoptilolite/spongy iron zones in series, was proposed for ammonium-nitrogen-contaminated groundwater remediation. Column experiments were performed to: (1) evaluate the overall NH4(+)-N removal performance of the proposed multibarrier, (2) investigate nitrogen transformation in the three zones, (3) determine the reaction front progress, and (4) explore cleanup mechanisms for inorganic nitrogens. The results showed that NH4 (+)-N percent removal by the multibarrier increased up to 90.43 % after 21 pore volumes (PVs) at the influent dissolved oxygen of 0.68∼2.45 mg/L and pH of 6.76∼7.42. NH4(+)-N of 4.06∼10.49 mg/L was depleted and NOx(-)-N (i.e., NO3 (-)-N + NO2(-)-N) of 4.26∼9.63 mg/L was formed before 98 PVs in the ORC zone. NH4(+)-N of ≤4.76 mg/L was eliminated in the clinoptilolite zone. NOx(-)-N of 10.44∼12.80 mg/L was lost before 21 PVs in the spongy iron zone. The clinoptilolite zone length should be reduced to 30 cm. Microbial nitrification played a dominant role in NH4(+)-N removal in the ORC zone. Ion exchange was majorly responsible for NH4(+)-N elimination in the clinoptilolite zone. Chemical reduction and hydrogenotrophic denitrification both contributed to NOx(-)-N transformation, but the chemical reduction capacity decreased after 21 PVs in the spongy iron.

Fabrication of novel oxygen-releasing alginate beads as an efficient oxygen carrier for the enhancement of aerobic bioremediation of 1,4-dioxane contaminated groundwater

Oxygen-releasing alginate beads (ORABs), a new concept of oxygen-releasing compounds (ORCs) designed to overcome some limitations regarding the fast oxygen release rate and the high pH equilibrium of ORCs, were fabricated to promote the stimulation of aerobic biodegradation in anaerobic groundwater. Slow oxygen-releasing rate and maintenance of constant pH were achieved by changing the parameters (ionic radius and valence) related to the cross-linking ions composing ORABs, and the best results were obtained for ORABs cross-linked with Al (Al-ORABs). Furthermore, the mechanism of the improved aerobic biodegradation using Al-ORABs under oxygen-limiting groundwater conditions was elucidated in batch and column studies with 1,4-dioxane and Mycrobacterium sp. PH-06 as a model contaminant and aerobic microbes, respectively. Maximum 1,4-dioxane degradations of 99% and 68.1% were achieved when Al-ORABs were applied in batch and column conditions, respectively, whereas 34.3% and 18% of 1,4-dioxane were degraded without Al-ORABs in batch and column conditions, respectively.

Biodegradation of Bitumen in Soil and Its Enhancement by Inorganic Fertilizer and Oxygen Release Compound: Experimental Analysis and Kinetic Modelling

The objective of this work was to investigate and evaluate the effect of inorganic nutrient (NPK fertilizer), hydrogen peroxide and their combinations on the kinetics of bitumen degradation by autochthonous microorganisms in the soil. The study was carried out by artificially contaminating an un-impacted tropical soil with 40 g/kg of bitumen in plastic bins and amended with various amount of NPK fertilizer (1.63 g, 2.10 g and 2.56 g), hydrogen peroxide (0.5 g and 1.0 g) and combinations of NPK fertilizer and hydrogen peroxide (2.13 g, 2.60 g and 3.06 g), respectively. The bioremediation was carried out for 21 days. Results showed that inorganic NPK fertilizer, hydrogen peroxide and their combinations stimulated microbial growth and enhanced bitumen biodegradation. The bacterial count and percentage total petroleum hydrocarbon degradation relatively increased with increase in the amount of inorganic nutrient and oxygen release compound used in this study. More than 50% of the hydrocarbons were degraded within each remediation period. The combined addition of inorganic NPK fertilizer and hydrogen peroxide provided the highest percentage biodegradation (>60%). Under abiotic conditions, no total petroleum hydrocarbon removal was observed while a maximum of 10.8% total petroleum hydrocarbons removal was obtained in unamended soil (natural attenuation) experiment. A first-order kinetic model successfully described the bitumen biodegradation. The model revealed that bitumen contaminated-soil microcosms amended with inorganic nutrient and oxygen release compound had higher biodegradation rate constants, as well as lower half-life times, than unamended soil (natural attenuation) remediation system. The biodegradation rate constant was higher with lower half life time as the amount of inorganic nutrient and oxygen release compound in soil increased.

Improvement of Oxygen Releasing Compounds Amended with Modified Oil Sludge

The effect of modified oil sludge (MOS), CaO2and bentonite amounts on the performance of oxygen releasing compounds (ORCs) has been investigated. Results showed that MOS was the primary factor to affect the ORCs performance. Increasing the amount of MOS resulted in extension of the lifetime of ORC; instead, decreasing it would obtain relatively large stable oxygen release rate. Moreover, addition of MOS made significant decrease in initial oxygen release rate. Compared with ORCs without MOS, ORCs with 5%, 10%, 15% and 20% MOS had initial oxygen release rates reduced by 15%, 40%, 65% and 65%, respectively. Another characteristic of the MOS was also found. It proved that precipitates generating from oxygen-releasing process, such as calcium and magnesium minerals, could hardly accumulate on the surface of ORC. Addition of MOS reduced the clogging of oxygen diffusion channels caused by the mineral deposition on the surface of ORC; thus, extended the lifetime. The ORC that replaced bentonite with MOS was economical and environment-friendly. One available ORC contained CaO2(30%), MOS (5%), cement (30%) and sand (35%); and its stable oxygen release rate was 0.146 g [O2]/(kg [OR·d) and the lifetime was 187 d.

Effect of Magnesium Peroxide Biostimulation of Fish Feed-Loaded Marine Sediments on Changes in the Bacterial Community

The effect of an oxygen-releasing compound (ORC) magnesium peroxide (MgO(2)) on the changes in the bacterial community in organically polluted sediment of aquaculture farms was tested in a microcosm experiment. The sediment, to which fish feed was added, was treated with 1% or 5% MgO(2). The addition of fish feed induced a highly reduced environment with low redox potential, high total sulfides, and abundance of sulfate-reducing bacteria (SRB) . Although the sediment remained highly reduced at 1% MgO(2), there was a significant reduction of total sulfides, increase of redox potential, and resultant reduction of SRB. The bacterial community clearly changed with the treatments according to denaturing gradient gel electrophoresis (DGGE) analysis of 16S ribosomal RNA gene (16S rDNA) . Aerobes disappeared in the fish feed-added sediment, and some SRB emerged in place of these aerobes. On the other hand, the SRB disappeared in the ORC-amended sediment due to its highly oxic condition. This study revealed the bacterial community in the sediments was affected mainly by the redox potential and resultant sulfides produced by SRB, but total organic carbon and nitrogen were not determinants of the microbial population.

Evaluation of Hydrogen/Oxygen Release Compounds for the Remediation of VOCs

Problem statement: Volatile Organic Compounds (VOCs) were widespread in groundwater of industrialized areas and in situ remediation intervents characterized by a high environmental compatibility were of main interest. The scope of this study was the evaluation of the potential of two innovative reagents (HRC and ORC from Regenesis) for the remediation of Volatile Organic Compounds (VOCs). The reagents respectively perform reduction and oxidation mechanisms, both effective in the degradation of VOCs. Approach: Hydrogen Release Compound (HRC) and Oxygen Release Compound (ORC) were tested about the degradation of Benzene, Toluene, Ethylbenzene and Xylene (BTEX) and some Chlorinated Aliphatic compounds (CAHs). Five series of batch tests were performed with an artificial polluted aqueous phase and some soil coming from a polluted site in which natural attenuation of VOCs occurs. Results: ORC exhibited a good efficiency in degradation of BTEX and zero order model was found as a reliable approximation of experimental data (with the exceptions of benzene and toluene, for which a first order kinetic model was trustworthy), while HRC showed a good efficiency in the degradation of CAHs and a first order model consistently estimated almost all experimental data. The experimental data were modeled by means of different mathematical equations, considering zero and first order kinetics and the results were discussed and compared. Conclusions: On the grounds of the performed tests, Oxygen Release Compound (ORC) is effective in BTEX degradation and Hydrogen Release Compound (HRC) in CAHs removal.

Development of Novel Oral Formulations Prepared via Hot Melt Extrusion for Targeted Delivery of Photosensitizer to the Colon

Colon-residing bacteria, such as vancomycin-resistant Enterococcus faecalis and Bacteroides fragilis, can cause a range of serious clinical infections. Photodynamic antimicrobial chemotherapy (PACT) may be a novel treatment option for these multidrug resistant organisms. The aim of this study was to formulate a Eudragit®-based drug delivery system, via hot melt extrusion (HME), for targeting colonic release of photosensitizer. The susceptibility of E. faecalis and B. fragilis to PACT mediated by methylene blue (MB), meso-tetra(N-methyl-4-pyridyl)porphine tetra-tosylate (TMP), or 5-aminolevulinic acid hexyl-ester (h-ALA) was determined, with tetrachlorodecaoxide (TCDO), an oxygen-releasing compound, added in some studies. Results show that, for MB, an average of 30% of the total drug load was released over a 6-h period. For TMP and h-ALA, these values were 50% and 16% respectively. No drug was released in the acidic media. Levels of E. faecalis and B. fragilis were reduced by up to 4.67 and 7.73 logs, respectively, on PACT exposure under anaerobic conditions, with increased kill associated with TCDO. With these formulations, photosensitizer release could potentially be targeted to the colon, and colon-residing pathogens killed by PACT. TCDO could be used in vivo to generate oxygen, which could significantly impact on the success of PACT in the clinic.

Microbial Biodegradation of Aromatic Compounds in a Soil Contaminated with Gasohol

The studies developed in this work aimed to find alternatives to biodegradation or bioremediation of soils contaminated with gasoline or gasohol. So, the biodegradation of benzene, toluene and o-xylene (BTX) in soil samples contaminated with gasoline or gasohol by a bacterial consortium was studied. Four bacterial strains were selected for the consortium based on their growth capacity in gasoline, gasohol and BTX as sole carbon sources, and on the production of biosurfactants in mineral medium containing gasohol as the sole carbon source. The reduction of TX concentrations in soil slurries in a multi-cell bioreactor system was used as the criterion to evaluate biodegradation efficiency. BTX removal was highly stimulated by air injection and mineral nutrients, and was significantly increased by the presence of the bacterial consortium. Addition of a proprietary oxygen release compound did not stimulate the biodegradation of BTX.

토착균주 활성화를 위한 산소발생제 MgO2투입에 의한 연안저질의 이화학적 성분 변화 관찰

Rapid industrialization has brought Nam-Hae area serious environmental problems associated with released oil and other hydrocarbons. In this work, in order to enhance the quality of the shoreline sediment we made enviro-chemical analyses of its substances, TPHs and microbial growth after treating with oxygen releasing compound(ORC) such as . Total organic compound(TOC) was reduced from 33.45% to 25.1~31.08% meanwhile COD decreased from 27.5~28.9mg/ to 19.9~26.1mg/ for input of 2~10% in 20days. For 10% input, TP and TN were reduced by 13.3% and 18.8%, respectively. Most of all TPH was decomposed by max. 42.4% in 21days, and the total viable count of microbes was found to be exponentially increased by 75.9%.

A permeable reactive barrier for the bioremediation of BTEX-contaminated groundwater: Microbial community distribution and removal efficiencies

This study was conducted with column experiments, batch experiments, and bench-scale permeable reactive barrier (PRB) for monitoring the PRB in the relation between BTEX (benzene, toluene, ethylbenzene, and p-xylene) decomposition efficiency and the distribution of a microbial community. To obtain the greatest amount of dissolved oxygen from oxygen-releasing compounds (ORCs), 20-d column tests were conducted, the results of which showed that the highest average amount of dissolved oxygen (DO) of 5.08 mg l(-1) (0.25 mg-O(2)d(-1)g(-1)-ORC) was achieved at a 40% level of CaO(2). In the batch experiments, the highest concentrations of benzene and toluene in which these compounds could be completely degraded were assumed to be 80 mg l(-1). Long-term monitoring for a PRB indicated that ORCs made with the oxygen-releasing rate of 0.25 mg-O(2)d(-1)g(-1)-ORC were applicable for use in the PRB because these ORCs have a long-term effect and adequately meet the oxygen demand of bacteria. The results from the DGGE of 16S rDNAs and real-time PCR of catechol 2,3-dioxygenase gene revealed the harmful effects of shock-loading on the microbial community and reduction in the removal efficiencies of BTEX. However, the efficiencies in the BTEX decomposition were improved and the microbial activities could be recovered thereafter as evidenced by the DGGE results.

Use of an oxygen-releasing compound to aerate eutrophic reservoir water

This study examined the use of an Oxygen Release Compound (ORC®) as a slow release chemical aeration agent within eutrophic surface water systems. Bench and pilot-scale experiments involving ORC® treatment of eutrophic reservoir water were conducted to determine operational properties of ORC® and examine its performance as an aeration agent within a surface water environment. The bench-scale study involved the application of 10, 25 and 50 g ORC® doses to 1 L Erlenmeyer flasks containing various water and sediment samples. The pilot-scale study involved a scaled up simulation of full-scale reservoir systems using large fiberglass tanks, where water quality parameters in an ORC®-treated tank were compared to an untreated tank over a 4 month period. The results of these experiments indicate that the application of ORC® can result in substantial increases in dissolved oxygen and pH when applied to deoxygenated water systems. Within the pilot scale study, a 300 g/m2 dose of ORC® at the sediment water interface prevented the onset of anoxic conditions over a 4 month growing season period, releasing approximately 20% of its mass as oxygen within this time frame.

Oxygen release compound as a chemical treatment for nutrient rich estuary sediments and water

The objectives of this work were: (i) to evaluate the efficacy of Oxygen Release Compound (ORC®), oxygen providing agent that enhance the oxidation of organic matter in fresh water, marine water, and sediment; and (ii) to explore the potential aquatic toxicity that might be generated due to its use. A bench scale laboratory experiments were conducted using five different water sources (2 freshwater, 2 marine water and a deionised water). During the assay, flasks of 1 L capacity were dosed with artificial sediment and ORC® and kept at room temperature for 10 days. Temperature, pH, DO, UV254, TOC and Mg were periodically measured. The potential aquatic toxicity that might be generated as a by-product of ORC® use was performed. The experimental results reveal that ORC® is indeed effective in releasing oxygen over a long period of time and it is also effective for the remediation of natural waters enriched with organic matter. The toxicity test shows that ORC® treatment did not create any biological toxicity in freshwater samples (IC50 < 1 Toxicity Unit – TU). However, marine water samples reveal a high toxicity and had IC50 > 1 TU. The study proves that ORC® was an appropriate technology that can safely be used to treat natural waters enriched with nutrient and natural organic matter.

Laboratory study on sequenced permeable reactive barrier remediation for landfill leachate-contaminated groundwater

Permeable reactive barrier (PRB) was a promising technology for groundwater remediation. Landfill leachate-polluted groundwater riches in various hazardous contaminants. Two lab-scale reactors (reactors A and B) were designed for studying the feasibility of PRB to remedy the landfill leachate-polluted groundwater. Zero valent iron (ZVI) and the mixture of ZVI and zeolites constitute the first section of the reactors A and B, respectively; the second section of two reactors consists of oxygen releasing compounds (ORCs). Experimental results indicated that BOD 5/COD increased from initial 0.32 up to average 0.61 and 0.6 through reactors A and B, respectively. Removal efficiency of mixed media for pollutants was higher than that of single media (ZVI only). Zeolites exhibited selective removal of Zn, Mn, Mg, Cd, Sr, and NH 4 +, and removal efficiency was 97.2%, 99.6%, 95.9%, 90.5% and 97.4%, respectively. The maximum DO concentration of reactors A and B were 7.64 and 6.78 mg/L, respectively, while the water flowed through the ORC. Therefore, sequenced PRB system was effective and was proposed as an alternative method to remedy polluted groundwater by landfill leachate.

In situ bioremediation of groundwater contaminated with petroleum constituents using oxygen release compounds (ORCs)

Over the past 5 years, the use of in situ biological remediation methods has gained acceptance for the biological degradation of petroleum hydrocarbons and chlorinated solvents in the groundwater. Application of slow-release compounds such as Oxygen Release Compound (ORC) and Hydrogen Releasing Compounds have been used routinely as remediation tools. This paper describes the implementation of an in situ bioremediation scheme to address the petroleum constituents in the groundwater at the site of a former gasoline station. Site investigations had indicated that groundwater beneath the site was contaminated with up to 34,300 μg/L benzene, toluene, ethylbenzene and xylenes (BTEX). The remedial scheme involved the installation of the four monitoring wells, monitoring and sampling of the wells and the application of ORCs into the Area of Concern (AOC). The results indicate that levels of petroleum constituents continue to be present in groundwater beneath the site after ORC injection. However, over time the levels of BTEX have significantly decreased. Kinetic study showed that the removal of BTEX fits a zero-order kinetic model for each monitoring well under enhanced oxidized conditions. The compound with the highest biodegradation rate constant was m,p-xylene in monitoring wells MW-2, MW-3 and MW-4.

Remediation of Trichloroethylene and Monochlorobenzene-Contaminated Aquifers Using the ORC-GAC-Fe 0CaCO 3 System: Volatilization, Precipitation, and Porosity Losses

The objectives of this study were to illustrate the reaction processes, to identify and quantify the precipitates formed, and to estimate the porosity losses in order to eliminate drawbacks during remediating monochlorobenzene (MCB) and trichloroethylene (TCE)-contaminated aquifers using the ORC-GAC-Fe 0-CaCO 3 system. The system consisted of four columns (112 cm long and 10 cm in diameter) with oxygen-releasing compound (ORC), granular activated carbon (GAC), zero-valent iron (Fe 0), and calcite used sequentially as the reactive media. The concentrations of MCB in the GAC column effluent and TCE in the Fe 0 column effluent were below the detection limit. However, the concentrations of MCB and TCE in the final calcite column exceeded the maximum contaminant level (MCL) under the Safe Drinking Water Act of the US Environmental Protection Agency (US EPA) that protects human health and environment. These results suggested that partitioning of MCB and TCE into the gas phase could occur, and also that transportation of volatile organic pollutants in the gas phase was important. Three main precipitates formed in the ORC-GAC-Fe 0-CaCO 3 system: CaCO 3 in the ORC column along with Fe(OH) 2 and FeCO 3 in the Fe 0 column. The total porosity losses caused by mineral precipitation corresponded to about 0.24% porosity in the ORC column, and 1% in the Fe 0 column. The most important cause of porosity losses was anaerobic corrosion of iron. The porosity losses caused by gas because of the production and entrapment of oxygen in the ORC column and hydrogen in the Fe 0 column should not be ignored. Volatilization, precipitation and porosity losses were considered to be the main drawbacks of the ORC-GAC-Fe 0-CaCO 3 system in remediating the MCB and TCE-contaminated aquifers. Thus, measurements such as using a suitable oxygen-releasing compound, weakening the increase in pH using a buffer material such as soil, stimulating biodegradation rates and minimizing the plugging caused by the relatively high dissolved oxygen levels should be taken to eliminate the drawbacks and to improve the efficiency of the ORC-GAC-Fe 0-CaCO 3 system.

A method for controlling hydrogen sulfide in water by adding solid phase oxygen

This work evaluates the addition of solid phase oxygen, a magnesium peroxide (MgO 2) formulation manufactured by Regenesis (oxygen-releasing compounds, ORC TM), to inhibit the production of hydrogen sulfide (H 2S) in an SRB-enriched environment. The initial rate of release of oxygen by the ORC was determined over a short period by adding sodium sulfite (Na 2SO 3), which was a novel approach developed for this study. The ability of ORCs to control H 2S by releasing oxygen was evaluated in a bench-scale column containing cultured sulfate reducing bacteria (SRB). After a series of batch tests, 0.4% ORC was found to be able to inhibit the formation of H 2S for more than 40 days. In comparison, the concentration of H 2S dropped from 20 mg S/L to 0.05 mg S/L immediately after 0.1% hydrogen peroxide (H 2O 2) was added, but began to recover just four days later. Thus, H 2O 2 does not seem to be able to inhibit the production of sulfide for an extended period of time. By providing long-term inhibition of the SRB population, ORC provides a good alternative means of controlling the production of H 2S in water.

Modeling and Comparison of Electrolytic Aeration and ORC® Aeration of Anoxic Groundwater in a Simulated Laboratory Aquifer

This study investigated the electrolytic method of aerating anoxic groundwater, where the goal for aeration is to enhance in situ bioremediation by indigenous microbes. Experiments in a simulated a...