The major objective of this project was to assess the application of atmospheric pressure microwave induced plasmas to the control of trichloroethene vapour emissions from industrial cleaning processes. Laboratory experiments, chemical modelling and chemical analysis were the three major elements of the project. A typical stream to be treated, as measured at the project test site, was 60 lmin-1 of air contaminated with 2 % trichloroethene vapour. The practical experiments carried out were trichloroethene dissociation by microwave plasma, propane-assisted microwave plasma and conventional propane combustion. Flow rates of 4 � 12 lmin-1, trichloroethene concentrations of 0 � 6 % in air and plasma powers of up to 3 kW were investigated. The processes were simulated using both equilibrium and kinetic modelling in CHEMKIN. Chemical analysis was done using gas chromatography with an electron capture detector, with gas chromatography/mass spectrometry to identify eluted compounds. The destruction and removal efficiencies, by-products, temperature and robustness of each process were investigated. A simple economic and environmental analysis was done, and the results were compared with currently available processes.

Dated 1983. Bibliography: leaves 174-181.

This thesis focused on using microcosms to better understand the aerobic cometabolic processes of TCE and cis-DCE transformation that occurred during a Cometabolic Air Sparging (CAS) demonstration at McClellan Air Force Base. The microcosms were created with groundwater and aquifer materials from the demonstration site. Concentrations of compounds in the microcosms were maintained to mimic conditions where the demonstration was performed. Propane was used as the primary substrate to stimulate indigenous propane-utilizers present in the McClellan subsurface. The microcosms were used to test the potential of the propane-utilizers to transform the CAHs of interest, and determine their nutrient requirements while transforming these compounds. Vadose zone microcosms were also created and used to compare the cometabolic processes and nutrient requirements of the propane-utilizers under these different conditions. After the addition of propane a ten-day lag period was observed before the propane-utilizers were stimulated in all the microcosms. The presence of CAHs and excess nitrogen did not have any effect on the lag period required to stimulate these microorganisms. Microcosms that received nitrogen amendments maintained effective transformation of TCE and c-DCE with successive additions. The rate of c-DCE transformation was observed to be faster than TCE transformation. Complete removal of the CAHs occurred in these microcosms. No other nutrients, such as phosphorous, were observed to cause any nutrient limitations. However, the microcosms that only had limited amounts of nitrogen present were only able to maintain transformation ability for a short time. Propane utilization rates gradually decreased with each addition, and CAH transformation eventually ceased. This was also observed during the CAS field demonstration after successive additions of propane. Ammonia gas was added to the sparge gas in the field and propane utilization and CAH transformation resumed. Ammonia gas was added to the nitrogen-limited microcosms, and like the field demonstration, propane utilization and CAH transformation resumed. Nitrogen was found to be a critical nutrient for effective cometabolism of CAHs. Nitrogen supplied either as ammonia or nitrate was required for the propane-utilizers to maintain effective rates of propane utilization and CAH transformation ability. By comparing different sets of microcosms under different conditions, estimates were made to the amount of nitrogen required by the propane-utilizers with and without CAHs transformed. The transformation of CAHs significantly increased the propane-utilizers requirements for nitrogen. A 2.0-3.8-fold increase in was observed for nitrogen consumption when CAHs were transformed, possibly resulting from toxic effects caused by the transformations. The sparge gas used at the CAS demonstration also contained ethylene at a low concentration (1% vol/vol). The microcosm experiments with this concentration of ethylene were found not to have any negative effects on CAH transformation. The propane-utilizers were also able to maintain propane utilization and CAH transformation at high CAH concentrations. The vadose zone microcosms showed that propane utilization in the vadose zone was an order of magnitude lower than what was observed in the saturated microcosms. Also bioavailable nitrogen was required to maintain propane utilization rates. However, higher CAH concentrations were found to inhibit the stimulation of the propane-utilizers under these conditions. / Graduation date: 2002

The objective of this research was to evaluate the treatment efficiency of a trichloroethylene(TCE)-contaminated aqueous solution and soil by combined technologies of the emulsified nanoscale zero-valent iron slurry (ENZVIS) and electrokinetic remediation process. Nanoiron was synthesized using the chemical reduction method by industrial grade chemicals. The synthesized nanoparticles contained elemental iron and iron oxide as determined by X-ray diffractmetry(XRD). Micrographs of FE-SEM have shown that a majority of nanoiron were in the size range of 30~50 nm. The stability study of food-grade soybean oil emulsion was conducted using six non-ionic surfactants and soybean oil. The results have shown that the emulsion prepared by mixed surfactants (Span 80 and Tween 40) and soybean oil yielded a better emulsion stability. Based on the above finding, the nanoiron slurry, soybean oil and aforementioned, mixed surfactants were used to prepare ENZVIS. Degradation of TCE by ENZVIS under various operating parameters was carried out in batch experiments. The experimental results have indicated that emulsified nanoiron outperformed nanoiron in TCE dechlorination rate. ENZVIS (0.75 g-Fe0/L) degradated TCE (initial conc.= 10 mg/L) down to 45 %. An increase of the oil dosage could improve the stability of the emulsion, but yielding a negative influence on degradation of TCE. Experimental results also showed that ENZVIS could remove TCE up to 94 % when pH=6. It was also formed that a higher TCE initial concentration would result in a higher TCE removal efficiency. In addition, using ENZVIS to degraded TCE-contaminated artificial groundwater has indicated that nitrate and carbonate of groundwater will suppress nanoiron reaction with TCE. Especially, a high concentration of carbonate in the reaction system might form a passive film or precipitates on nanoiron surface. This study further evaluated the treatment efficiency of combining ENZVIS and electrokinetic technology in treating a TCE-contaminated soil. Experimental conditions were given as follows:(1) initial TCE concentration in the range of 98~118 mg/kg; (2) an electric potential gradient of 1 V/cm; (3) a daily addition of 20 mL ENZVIS; and (4) a reaction time of 10 days. Experimental results have shown that an addition of ENZVIS to the anode reservoir of strongly acidic and oxidative environment would cause nanoiron to corrode rapidly and decrease TCE removal efficiency. On the other hand, an addition of ENZVIS to the cathode reservoir would enhance the degradation of TCE therein. In summary, an addition of ENZVIS to the cathod reservoir would yield the best TCE removal efficiency.

The purpose of this study was to use controlled release technology combining with in situ chemical oxidation (ISCO) and permeable reactive barrier (PRB) to remediate TCE-contaminated groundwater. In this study, potassium permanganate (KMnO4) releasing material was designed for potassium permanganate release in groundwater. The components of potassium permanganate releasing material included poly (£`-caprolactone) (PCL), potassium permanganate, and starch with a weight ratio of 2:1:0.5. Approximately 63.8% (w/w) of potassium permanganate was released from the material after 76 days of operation. The released was able to oxidize contaminant in groundwater. Results from the solid oxidation demand (SOD) experiment show that the consumption rate increased with increased contaminant concentration. TCE removal efficiency increased with the increased TCE concentration. The second-order rate law can be used to simulate the TCE degradation trend. In the column experiment, results show that the released MnO4- could oxidize TCE and TCE degradation byproducts when 95.6 pore volume (PV) of contaminated groundwater was treated. More than 95% of TCE removal can be observed in the column study. Although the concentration of manganese dioxide (MnO2) began to rise after 8.8 PV of operation, TCE removal was not affected. Results also show that low level of hexavalent chromium was detected (< 0.05 mg/L). Results from the scanning electron microscope (SEM) and energy-dispersive spectroscope (EDX) analyses show that the amounts of manganese and potassium in the materials decreased after the releasing experiment. Results indicate that the concentration of TCE and SOD need to be analyzed before the releasing materials are applied in situ. In the practical application, the releasing materials will not become solid wastes because they are decomposed after use. If this slow-releasing technology can be combined with a permeable reactive barrier system, this technology will become a more economic and environmentally-friendly green remedial system.

Soil and groundwater at many existing and former industrial areas and disposal sites is contaminated by organic solvent compounds that were released into the environment. Organic solvent compounds are heavier than water. When they are released into the subsurface, they tend to adsorb onto the soils and cause the appearance of LNAPL (light nonaqueous phase liquid) and DNAPL (dense nonaqueous phase liquid) pool. The industrial petroleum hydrocarbons (e.g., methyl tertiary-butyl ether, MTBE and benzene) and chlorinated solvent (e.g., trichloroethylene, TCE) are among the most ubiquitous organic compounds found in subsurface contaminated environment. One cost-effective approach for the remediation of the chlorinated solvent and petroleum products contaminated aquifers is the installation of permeable reactive zones or barriers within aquifers. As contaminated groundwater moves through the emplaced reactive zones, the contaminants are removed, and uncontaminated groundwater emerges from the downgradient side of the reactive zones. The objectives of this study were developed to evaluate the feasibility of applying in-situ chemical oxidation (ISCO) barrier and in-situ slow polycolloid-releasing substrate (SPRS) biobarrier system on the control of petroleum hydrocarbons and chlorinated solvent plume in aquifer. In the ISCO barrier system, it contained oxidant-releasing materials, to release oxidants (e.g., persulfate) contacting with water for oxidating contaminants existed in groundwater. In this study, laboratory-scale fill-and-draw experiments were conducted to determine the compositions ratios of the oxidant-releasing materials and evaluate the persulfate release rates. Results indicate that the average persulfate-releasing rate of 7.26 mg S2O82-/d/g was obtained when the mass ratio of sodium persulfate/cement/sand/water was 1/1.4/0.24/0.7. The column study was conducted to evaluate the efficiency of in situ application of the developed ISCO barrier system on MTBE and benzene oxidation. Results from the column study indicate that approximately 86-92% of MTBE and 95-99% of benzene could be removed during the early persulfate-releasing stage (before 48 pore volumes of groundwater pumping). The removal efficiencies for MTBE and benzene dropped to approximately 40-56% and 85-93%, respectively, during the latter part of the releasing period due to the decreased persulfate-releasing rate. Results reveal that acetone, byproduct of MTBE, was observed and then further oxidized completely. Results suggest that the addition of ferrous ion would activate the persulfate oxidation. However, excess ferrous ion would compete with organic contaminants for persulfate, causing the decrease in contaminant oxidation rates. In the SPRS biobarrier system, the food preparation industry has tremendous experiences in producing stable oil-in-water (W/O, 50/50) emulsions with a uniformly small droplet size. Surfactant mixture (71 mg/L of SL and 72 /L of SG) blending with water could yield a stable and the optimal emulsion was considered the best. The small absolute value of the emulsion zeta potential reduces inter-particle repulsion, causing the emulsion droplets to stick to each other when they collided. Overtime, large masses of flocculated droplets can form which then clog the sediment pores. The results can be used to predict abiotic interactions and distribution of contaminant mass expected after SPRS injection, and thus provides a more accurate estimate of the mass of TCE removed due to enhanced biodegradation. The effect of TCE partitioning to the vegetable oil on contaminant migration rates can be approximated using a retardation factor approach, where 0.28 years through a 3 m barrier. In anaerobic microcosm experiments, result show that SPRS can be fermented to hydrogen and acetate could be used as a substrate to simulate reductive dehalorination. The apparent complete removal of nitrate and sulfate by SPRS addition was likely a major factor that promoted the complete reduction of TCE at later stages of this study. Results from the column experiment indicate that occurrence of anaerobic reductive dechlorination in the biobarrier system can be verified by: (1) the oil: water partition coefficients of dissolved TCE into vegetable oil were be used to predict abiotic interactions and distribution of contaminant mass expected after SPRS injection. (2) The SPRS can ferment to hydrogen and acetate could be used as a substrate to simulate reductive dechlorination. The proposed treatment scheme would be expected to provide a more cost-effective alternative to remediate other petroleum hydrocarbons and chlorinated solvents-contaminated aquifers. Experiments and operational parameters obtained from this study provide an example to design a passive barriers system for in-site remediation.

In this study, potassium permanganate was used as the oxidant to remediate TCE¡Vcontaminated groundwater. The objectives of this bench-scale oxidation study include the following: (1) evaluate the overall TCE oxidation rate with the presence of KMnO4, (2) assess the consumption rate of KMnO4, (3) evaluate the effect of the oxidation by-product, manganese dioxide (MnO2), on the TCE oxidation rate. The control factors in this study include (1) four different molar ratios of KMnO4 to TCE [designated as P, (KMnO4/TCE) = 2, 5, 10, and 20]; (2) four different TCE concentration (0.5, 5, 20, and 100 ppm); (3) three different initial pH values (2.1, 6.3, and 12.5); (4) three different oscillator mix rate (0, 50, and 200 rpm); (5) four different molar ratios of dibasic sodium phosphate (Na2HPO4) to Mn2+ [designated as D, (Na2HPO4/Mn2+) = 0, 50, 100, and 300D], and (6) two different medium solutions [deionized (DI) water and groundwater]. Moreover, the effects of D values on TCE oxidation rate and KMnO4 consumption rate were also evaluated. Experimental results indicate that a second-order reaction model could be applied to express the oxidation reaction of TCE by KMnO4, and the calculated rate constant equals 0.8 M-1s-1. Results also show that the higher the P value, the higher the TCE oxidation rate. Moreover, TCE oxidation rate was not affected under low pH conditions (pH = 2.10 and 6.3). However, TCE oxidation rate dropped under high pH condition (pH 12.5) due to the transformation of KMnO4 to manganese dioxide. The following three pathways would cause the production of manganese dioxide: (1) direct oxidation of TCE by KMnO4, (2) production of Mn2+ after the oxidation of TCE by KMnO4, and Mn2+ was further oxidized by KMnO4 to form manganese dioxide, and (3) transformation of KMnO4 to manganese dioxide under high pH condition. Results also show that more manganese dioxide was produced while groundwater was used as the medium solution. Results show that the produced manganese dioxide was 47.2% - 81.5% less with the addition of dibasic sodium phosphate. Moreover, the variations in D values would not affect the TCE oxidation rate. However, the increase in D value would decrease the consumption of KMnO4. Results also reveal that significant inhibition of manganese dioxide production was observed under low pH condition. Furthermore, no TCE oxidation byproducts were detected after the oxidation reaction. Key words: KMnO4, TCE, manganese dioxide and dibasic sodium phosphate

The objective of this research was to evaluate the treatment efficiency of a trichloroethylene (TCE) contaminated soil by combined technologies of the suspension of palladized nanoiron and electrokinetic remediation process. First, nanoiron and palladized nanoiron were prepared using the chemical reduction method. Then they were characterized by various methods. Micrographs of scanning electron microscopy have shown that a majority of these nanoparticles were in the range of 50-80 nm. Specific surface areas were determined to be 76.88 m2/g and 100.61 m2/g for the former and latter, respectively. Results of X-ray diffractometry have shown that both types of nanoiron were poor in crystallinity. Three anionic dispersants were employed for evaluating their performance in stabilizing various nanoiron. Results have demonstrated that an addition of 1 wt% of Dispersant E during nanoiron preparation would result in a good stabilization of nanoiron. If the system pH was adjusted to 2.99, nanoparticles would settle rapidly. Batch tests were carried out to investigate the effects of various operating parameters on degradation of TCE in aqueous solutions. Experimental results have indicated that palladized nanoiron outperformed nanoiron in treatment of TCE in this study. The employment of Dispersant E would enhance the treatment efficiency further. Test results also showed that a linear increase of reaction rate constant was found with an increasing dose of palladium from 0.05 wt% to 1 wt% based on the mass of nanoiron. Further, an exponential increase of reaction rate constant would be obtained with an increasing pH. As for mixing intensity, it was found to be insignificant to the treatment efficiency of TCE in aqueous solutions. The final stage of this study was to evaluate the treatment efficiency of combined technologies of the suspension of palladized nanoiron and electrokinetic remediation process in treating a TCE-contaminated soil. Test conditions used were given as follows: (1) initial TCE concentration: 160-181 mg/kg; (2) electric potential gradient: 1 V/cm; (3) daily addition of 20 mL of suspension of palladized nanoiron (2.5 g/L) to the electrode reservoir; and (4) reaction time: 6 days. Test results have shown that addition of palladized iron suspension to the cathode reservoir yielded the lowest residual TCE concentration in soil. Namely, about 92.5% removal of TCE from soil. On the other hand, addition of palladized iron suspension to the anode reservoir would enhance the degradation of TCE therein. Based on the above findings, the treatment method employed in this work was proven to be a novel and efficient one in treating TCE-contaminated soil.

In this research, nanoscale zero-valent iron (NZVI) was synthesized using the chemical reduction method. Experimental results have revealed that nanoiron synthesized by the reagent-grade chemicals had a size range of 50-80 nm, as determined by FE SEM. BET specific surface area of thus synthesized nanoparticles was 66.34 m2/g. NZVI prepared by the industrial-grade chemicals had a broader particle size distribution (30-80 nm) and its BET specific surface area was 61.50 m2/g. Results of XRD showed that both types of NZVI were composed of iron with a poor crystallinity. Additional test results further showed that both types of NZVI had similar characteristics. NZVI prepared by the chemical reduction method tends to aggregate resulting in a significant loss in reactivity. To overcome this disadvantage, four water-soluble dispersants were used in different stages of the NZVI preparation process. Of these, Dispersant A (an anionic surfactant) has shown its superior stabilizing capability to others. An addition of 0.5 vol % Dispersant A during the nanoiron preparation process would result in a good stability of NZVI slurry (NZVIS). Degradation of trichloroethylene (TCE) by NZVIS under different atmospheres was carried out in batch experiments. Experimental results have shown that the TCE dechlorination rate increased markedly when the reaction proceeded under hydrogen gas atmosphere as compared with that of air. Methane was the primary end product with a trace amount of ethane and ethylene when the reaction was conducted under the atmosphere of H2. It was suggested that an addition of H2 to the reaction system could promote the hydrogenolysis reaction for better degradation. On the other hand, ethane was the main product when the reaction system consisted of nanoscale palladized iron and H2 atmosphere. It demonstrated that Pd-catalyzed TCE dechlorination has resulted in a direct conversion of TCE to ethane in the study. The greatest dechlorination rate was obtained when 2 g/L nanoscale palladized iron and 50 mL H2 was employed in the reaction system. Under the circumstances, the TCE (10 mg/L) removal efficiency was up to 99 % in 3 minutes. Experimental results have demonstrated that the reaction system with both nanoscale palladized iron and H2 atmosphere would promote TCE degradation rate. The culture of microorganism in soil showed minor changes to microbial community structures between the pre- and post-injection conditions. The number of microorganism colony was found to be increased after adding 1 mL NZVIS to 1 g soil. Experimental results revealed that NZVIS would not cause the inhibition or reduction of microorganism activity. Surface modification of NZVI slurry by Dispersant A could enhance its transport in saturated porous media. Sticking coefficients were determined to be 0.56 and 0.11, respectively, for bare and Dispersant A-modified NZVIS transporting in quartz sand columns. The sticking coefficient for modified NZVIS transport in soil (loamy sand) column was determined to be 0.0061. Apparently, NZVIS modified by Dispersant A would enhance the transport of NZVI in saturated porous media. The results of combining electrokinetic technology and NZVIS injection tests in horizontal soil column illustrated that the sticking coefficient was 0.00034 and the total content of iron reduced 10 wt. %. Experimental results revealed that the transport distance of NZVIS in saturated horizontal soil column would be greatly increased under electronkinetic conditions.

Contamination by dense non aqueous phase liquids (DNAPLs) [e.g., trichloroethylene (TCE)] in soil and groundwater has become an issue of great concern in many industrialized counties. In this study, a chlorinated-compound spill site was selected as the case study site to evaluate the possible risk to site workers and local residents caused by the contaminated soil and groundwater. The contaminants of concern at this site were TCE and 1,1-Dichloroethylene (1,1-DCE). The detected concentrations for TCE and 1,1-DCE exceeded the control standards of 0.05 and 0.07 mg/L, respectively. In this study, the Risk-based Corrective Action (RBCA) protocol developed by American Society for Testing and Materials (ASTM), health and risk assessment methods for soil and groundwater contaminated sites developed by Taiwan Environmental Protection Administration were applied for risk calculation and quantification. Monte Carlo analysis using @RISK software was applied for uncertainty analysis to calculate the cumulative risk at 95% probability distribution. Moreover, a natural attenuation model (BIOCHLOR) was used to evaluate the effectiveness of natural attenuation mechanisms on the chlorinated compounds. Results from this study show that the occurrence of natural attenuation for the chlorinated compounds was confirmed through the anaerobic biodegradation processes. The calculated cumulative risk at 95% cumulative probability via ingestion route was 2.61¡Ñ10-5 through the Monte Carlo analysis. The calculated cumulative risk at 95% cumulative probability via inhalation route and ambient (outdoor) vapor inhalation diffusion channels were 1.461¡Ñ10-5 and 2.17¡Ñ10-6, respectively. Because the calculated risk levels were higher than the target cancer risk is 1¡Ñ10-6 described in Taiwan¡¦s ¡§Soil and Groundwater Remediation Act¡¨, appropriate remedial actions are required to lower the risk to below the target level. Results also show that the calculated hazard index (HI) values of the contaminated site are lower than the acceptable level (HI < 1) described in the ¡§Soil and Groundwater Remediation Act.¡¨ To meet the target level of cancer risk of 1¡Ñ10-6, TCE contaminated groundwater needs to be remediated to below the site specific target level (SSTL) for inhalation exposure routes in a confined space volume, which is 6.91 ¡Ñ 10-2 mg/L. Based on the results of risk assessment, it is very important for the decision makers to incorporate remedial activities including institutional controls, engineering controls, and remediation programs from RBCA results. This study provides a streamlined process and guidelines of developing the risk-based decision-making strategy for contaminated sites in Taiwan.