Trichloroethene (TCE) and tetrachloroethene (PCE) are among the most commonly detected groundwater contaminants, and are often difficult to remediate due to their presence as dense non-aqueous phase liquids (DNAPLs) in the subsurface. The objective of this study was to assess the potential of using a passive in situ carbon/hydrogen releasing barrier system to bioremediate TCE-contaminated groundwater. The slow carbon/hydrogen releasing material would cause the aerobic cometabolism and reductive dechlorination of TCE in aquifer. The carbon/hydrogen releasing materials would release carbon when contacts with groundwater and release hydrogen after the anaerobic biodegradation of released carbon, thus cause the reductive dechlorination of TCE. Results from the microcosm study indicate that the addition of emulsified substrate, cane molasses, Simple GreenTM (a biodegradable surfactant), or lecithin would enhance the biodegradation rate of TCE under anaerobic conditions. However, addition of multivitamin would increase the bacterial population in the media but would not be able to enhance the TCE degradation rate. Results show that a significant pH drop was observed due to the production of organic acids after the aerobic biodegradation process of cane molasses and lecithin. This also caused the inhibition of microbial growth in microcosms. Results reveal that higher TCE removal efficiency was observed in microcosms with Simple GreenTM addition followed by the addition of cane molasses, lecithin, multivitamin, emulsified substrate, groundwater (without substrate addition). Results from the microcosm study indicate that the addition of emulsified substrate would enhance the biodegradation rate of TCE under anaerobic conditions. However, appearance of high nitrate concentration would inhibit the TCE degradation process due to the occurrence of denitrification. Compared with nitrate, high sulfate concentration would not have significant impact on the reductive dechlorination of TCE. Results reveal that higher TCE removal efficiency was observed in microcosms with emulsified substrate addition followed by the addition of high sulfate concentration, high nitriate concentration, groundwater (without substrate addition). Results from the gene analysis show that phenol monooxygenase, toluene monooxygenase, and toluene dioxygenase were observed in the microcosms with lecithin, cane molasses, Simple GreenTM, and emulsified substrate. This indicates that the addition of substrates would induce the potential of TCE-degrading enzyme. Addition of emulsified substrate and emulsified substrate in nitrate or sulfate-rich media would stimulate Dehalococcoides sp. to induce tceA, bvcA, and vcrA, enzymes for TCE reductive dechlorination.

In Taiwan, more than 25% of all water uses comes from groundwater, and thus groundwater is a very valuable water resource for both domestic and industrial uses. However, groundwater at many existing former industrial sites and disposal areas was contaminated by halogenated organic compounds that were released into the environment. The chlorinated solvent trichloroethene (TCE) is one of the most ubiquitous of these compounds. In this laboratory-scale feasibility study, a hybrid two-stage process combining fiber filtration (FF) and nanofiltration (NF) was applied to remove to suspended solids (SS) and TCE from contaminated groundwater for water purification. In this study, a man-made kaolin solution was used to simulate groundwater purification using FF system. Then, microfiltration (MF), ultrafiltration (UF), and NF systems were applied for TCE removal. The hybrid membrane process using FF and NF units was used to evaluate the feasibility on TCE removal. The scanning electron microscope (SEM) and energy dispersive spectroscope (EDS) were used to investigate membrane morphology and structure after use. A 3-D excitation emission fluorescence matrix (EEFM) was used to evaluate the potential of membrane organic fouling. Results show that the optimization filtration velocity of FF was 15.3 m/hr, and the observed TCE and SS removal efficiencies were 80% and 60%, respectively. Removal mechanisms for MF and UF were mainly sieving, and the removal mechanism for NF was mainly electrostatic repulsion. Results indicate that NF had the highest TCE removal efficiency (98.2%). When initial TCE concentration was 1 mg/L, NF membrane pore might shrink caused increased TCE removal (rejection). When TCE concentration was higher 1 mg/L, membrane damage and pore enlargement was observed with decreased TCE removal efficiency. The observed SS, sulfate, and hardness removal efficiencies were 99.8%, 98.7%, and 98.7% respectively, when FF and NF hybrid process was used. Higher TCE concentration might enlarge membrane pore, which caused decreased membrane separation and increased flux. Approximately 46% of flux drop was observed when NF was used alone compared to the hybrid membrane process using FF as the first treatment stage. Membrane analyses show that residual TCE was adsorbed on the membrane. Low zeta potential of groundwater was observed due to the compressed electric double layer, which caused aggregation of particle. High zeta potential of permeate was due to the particle dispersive through hybrid process. Results from SEM analysis show that membrane morphology was damaged by TCE, and heavy metal in groundwater deposited on membrane. Results of EEFM analysis indicate that groundwater contained humic acid (HA) and soluble microbial by-product (SMP). HA and SMP might be adsorbed on fiber filter, and extracellular polymeric substances (EPS) that attached on fiber filter might be washed out. The organic powders on the surface of the fiber filter might be washed out causing the increased in NPDOC concentrations. Humic acid could be removed through NF process, and SMP might be adsorbed in membrane pore caused organic fouling, and SMP might be washed out after treatment by the FF+NF hybrid process. Results indicate that FF as pre-treatment can maintain higher flux. Higher TCE concentration caused membrane destruction and decreased membrane separation. TCE contaminated groundwater can be affectively treated by the hybrid membrane system to meet the groundwater standard and reclaimed water standard. Reclaimed water could be used for industrial cooling water and irrigation purposes.

<p>Soil bottles and soil slurry experiments were conducted to investigate the effect of some additives on the aerobic and anaerobic biodegradation of chlorinated aliphatic hydrocarbons; tetrachloroethylene (PCE), trichloroethylene (TCE) and dichloroethylene (DCE) in a contaminated soil from Startvätten AB Linköping Sweden. For the aerobic degradation study the soil sample was divided into two groups, one was fertilised. The two groups of soil in the experimental bottles were treated to varying amount of methane in pairs. DCE and TCE were added to all samples while PCE was found in the contaminated soil. Both aerobic and anaerobic experiments were conducted. For aerobic study air was added to all bottles to serve as electron acceptor (oxygen). It was observed that all the samples showed a very small amount of methane consumption while the fertilised soil samples showed more oxygen consumption. For the chlorinated compounds the expected degradation could not be ascertained since the control and experimental set up were more or less the same.</p><p>For the anaerobic biodegradation study soil slurry was made with different media i.e. basic mineral medium (BM), BM and an organic compound (lactate), water and sulphide, phosphate buffer and sulphide and phosphate buffer, sulphide and ammonia. To assure anaerobic conditions, the headspace in the experimental bottles was changed to N2/CO2. As for the aerobic study all the samples were added DCE and TCE while PCE was found in the contaminated soil. The sample without the soil i.e. the control was also given PCE. It was observed that there was no clear decrease in the GC peak area of the pollutants in the different media. The decrease in GC peak area of the pollutants could not be seen, this may be so because more susceptible microorganisms are required, stringent addition of nutrients and to lower the risk of the high concentration of PCE and petroleum products in the soil from Startvätten AB.</p>

Soil bottles and soil slurry experiments were conducted to investigate the effect of some additives on the aerobic and anaerobic biodegradation of chlorinated aliphatic hydrocarbons; tetrachloroethylene (PCE), trichloroethylene (TCE) and dichloroethylene (DCE) in a contaminated soil from Startvätten AB Linköping Sweden. For the aerobic degradation study the soil sample was divided into two groups, one was fertilised. The two groups of soil in the experimental bottles were treated to varying amount of methane in pairs. DCE and TCE were added to all samples while PCE was found in the contaminated soil. Both aerobic and anaerobic experiments were conducted. For aerobic study air was added to all bottles to serve as electron acceptor (oxygen). It was observed that all the samples showed a very small amount of methane consumption while the fertilised soil samples showed more oxygen consumption. For the chlorinated compounds the expected degradation could not be ascertained since the control and experimental set up were more or less the same. For the anaerobic biodegradation study soil slurry was made with different media i.e. basic mineral medium (BM), BM and an organic compound (lactate), water and sulphide, phosphate buffer and sulphide and phosphate buffer, sulphide and ammonia. To assure anaerobic conditions, the headspace in the experimental bottles was changed to N2/CO2. As for the aerobic study all the samples were added DCE and TCE while PCE was found in the contaminated soil. The sample without the soil i.e. the control was also given PCE. It was observed that there was no clear decrease in the GC peak area of the pollutants in the different media. The decrease in GC peak area of the pollutants could not be seen, this may be so because more susceptible microorganisms are required, stringent addition of nutrients and to lower the risk of the high concentration of PCE and petroleum products in the soil from Startvätten AB.