Cometabolic biodegradation processes are potentially useful for the bioremediation of hazardous waste sites. In this study the potential application of phenol-oxidizing and nitrifying bacteria as "priming biocatalysts" was examined in the degradation of polycyclic aromatic hydrocarbons (PAHs), aryl ethers, and aromatic ethers. We observed that a phenol-oxidizing Pseudomonas strain cometabolically degrades a range of 2- and 3-ringed PAHs. A sequencing batch reactor (SBR) was used to overcome the competitive effects between two substrates and the SBR was evaluated as a alternative technology to treat mixed contaminants including phenol and PAHs. We also have demonstrated that the nitrifying bacterium Nitrosomonas europaea can cometabolically degrade a wide range polycyclic aromatic hydrocarbons (PAHs), aryl ethers and aromatic ethers including naphthalene, acenaphthene, diphenyl ether, dibenzofuran, dibenzo-p-dioxin, and anisole. Our results indicated that all the compounds are transformed by N. europaea and that several unusual reactions are involved in these reactions. In the case of naphthalene oxidation, N. europaea generated predominantly 2-naphthol whereas other monooxygenases generate 1-naphthol as the major product. In the case of dibenzofuran oxidation, 3-hydroxydibenzofuran initially accumulated in the reaction medium and was then further transformed to 3-hydroxy nitrodibenzofuran in a pH- and nitrite-dependent abiotic reaction. A similar abiotic transformation reaction also was observed with other hydroxylated aryl ethers and PAHs. We also characterized the role of AMO in the degradation of aromatic ethers. Our results indicated that aromatic ethers including anisole were transformed by both 0-dealkylation or hydroxylation reactions. This research has led to the development of a rapid colorimetric assay to detect AMO activity. / Graduation date: 1998

Ex-situ bioremediation of saturated soil contaminated with pentachlorophenol and 2,3,5,6-TeCP is commonly accomplished by landfarming or by treatment in a bioreactor. Treating saturated, low-permeability soils in bioreactors, without pre-treatment requires a reactor capable of promoting anaerobic and/or aerobic removal of chlorophenols without transferring these contaminants to the aqueous phase. A pilot-scale bioreactor was designed to treat 3.7 cubic meters of contaminated soil with a saturated hydraulic conductivity of 0.12 cm/day. The bioreactor demonstrated significant removal of chlorophenols when soil was infused with a treatment mixture containing imitation vanilla flavoring as an electron donor for reductive dechlorination and primary substrate for aerobic cometabolism. Bench scale studies showed greater overall removal when feed mixtures included an inoculated biomass, or when treatment mixtures were maintained anaerobically prior to use. The combined results of these studies suggest that concentrations of pentachlorophenol and 2,3,5,6-TeCP in soil can be significantly reduced using fill and draw batch reactors, operated for three to five week long cycles, using a variety of treatment mixtures. / Graduation date: 1998

Graduation date: 1995

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Triclosan is incorporated in a wide array of medical and consumer products as an antimicrobial agent or preservative. Disposal of these products transport triclosan into wastewater and later into soils and surface waters. Due to incomplete removal of triclosan in wastewater treatment plants, contamination of triclosan in the environment has raised several concerns, including: (i) an aid to the development of cross-resistance to antibiotics, (ii) the toxicity to ecological health, (iii) the formation of chlorodioxins from triclosan and its metabolites. By using 14C-labeled triclosan, 14CO2 was observed in activated sludge samples, suggesting that triclosan was biodegraded. However, little is known about the microorganisms responsible for triclosan biodegradation in activated sludge. The goal of this study is to better understand biodegradation of triclosan in activated sludge. Two specific objectives are: (i) isolating and characterizing triclosan-degrading bacteria from activated sludge, (ii) characterizing the cometabolic degradation of triclosan through an ammonia-oxidizing bacterium Nitrosomonas europaea. A triclosan-degrading strain, KCY1, was successfully isolated from the activated sludge. The strain KCY1 completely degraded triclosan in three days when OD600 was 0.4. Based on 16S rRNA analysis, the strain KCY1 has 97% similarity with Phingomonas or Phingopyxis. Negative results of oxygenase activity assays suggested that other enzymes rather than oxygenases might be responsible for the triclosan biodegradation. Experiments using N. europaea showed that triclosan could be cometabolized. In the presence of inhibitor for ammonia monooxygenase (AMO), N. europaea was unable to degrade triclosan, suggesting that AMO might be responsible for triclosan degradation. Triclosan appeared to competitively inhibit ammonia oxidation by N. europaea. Results of this study showed that triclosan might be effectively biodegraded by triclosan-degrading cultures, strain KCY1 and N. europaea.

Perfluorooctanoate (PFOA) and Perfluorooctane sulfonate (PFOS) are two environmentally persistent perfluorinated compounds widely used for many industrial and consumer products due to their high thermal, oxidative resistance and surface repellence to water and oil. Their reproductive and developmental toxicity in lab animals and their persistence in environment have raised a serious concern for humans and animals. Trace amounts of these compounds have been found in water bodies, human blood, and wildlife samples. PFOA and PFOS are currently listed in Environmental Protection Agency's drinking water Contaminant Candidate List and in the list of Persistent Organic Pollutants in the Stockholm Convention. The strong covalent bond between carbon and fluorine present in PFOA and PFOS makes them stable and resistant to conventional treatment processes. Several advanced chemical processes can degrade PFOA and PFOS under high temperatures and pressures or other extreme conditions. However, the potential of biodegradation as a treatment technology for these compounds hasn't been developed successfully. This thesis focuses on evaluating the biodegradation potential of PFOA and PFOS. Fluoroacetate dehalogenase is an enzyme capable of defluorinating fluorinated aliphatic compounds. In this study, the potential of fluoroacetate dehalogenaseexpressing microorganisms to biodegrade PFOA and PFOS is examined. Two known fluoroacetate dehalogenase-expressing strains and fluoroacetate-degrading mixed cultures were used. The effect of ammonia in the enzyme activity was extended to study its effect on the biodegradation of PFOA and PFOS. Fluoride ions released during the mineralization of the PFOA and PFOS was used as a proof of biodegradation. The experiments with fluoroacetate dehalogenase-expressing strains and mixed culture consortia enriched from soil showed an increase in fluoride concentration in the solution thus indicating the possibility of successful biodegradation of PFOA and PFOS. Based on the fluoride ion content, it was also concluded that ammonia inhibits the enzyme activity in one of the two pure strains.

Triclosan is incorporated in a wide array of medical and consumer products as an antimicrobial agent or preservative. Disposal of these products transport triclosan into wastewater and later into soils and surface waters. Due to incomplete removal of triclosan in wastewater treatment plants, contamination of triclosan in the environment has raised several concerns, including: (i) an aid to the development of cross-resistance to antibiotics, (ii) the toxicity to ecological health, (iii) the formation of chlorodioxins from triclosan and its metabolites. By using 14C-labeled triclosan, 14CO2 was observed in activated sludge samples, suggesting that triclosan was biodegraded. However, little is known about the microorganisms responsible for triclosan biodegradation in activated sludge. The goal of this study is to better understand biodegradation of triclosan in activated sludge. Two specific objectives are: (i) isolating and characterizing triclosan-degrading bacteria from activated sludge, (ii) characterizing the cometabolic degradation of triclosan through an ammonia-oxidizing bacterium Nitrosomonas europaea. A triclosan-degrading strain, KCY1, was successfully isolated from the activated sludge. The strain KCY1 completely degraded triclosan in three days when OD600 was 0.4. Based on 16S rRNA analysis, the strain KCY1 has 97% similarity with Phingomonas or Phingopyxis. Negative results of oxygenase activity assays suggested that other enzymes rather than oxygenases might be responsible for the triclosan biodegradation. Experiments using N. europaea showed that triclosan could be cometabolized. In the presence of inhibitor for ammonia monooxygenase (AMO), N. europaea was unable to degrade triclosan, suggesting that AMO might be responsible for triclosan degradation. Triclosan appeared to competitively inhibit ammonia oxidation by N. europaea. Results of this study showed that triclosan might be effectively biodegraded by triclosan-degrading cultures, strain KCY1 and N. europaea.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Traditional remediation techniques in removing toxic metal contaminants using physical and chemical methods are expensive and may cause other forms of damage to the environment, comparing with these techniques bioremediation can serve as an inexpensive, effective and environmental friendly remediation method. This thesis mainly discusses different bioremediation techniques and identifies possible areas in Hong Kong for bioremediation and suggests bioremediation methods for each potential area. Bioremediation of toxic metals is the use of microorganisms, plants, or even larger sized organisms to decontaminate sites with toxic metals. Bioremediation includes phytoremediation, microremediation and vermiremediation which use plants, microorganisms and earthworms to remediate contaminated environments respectively. The 4 most common mechanisms in phytoremediation of toxic metals are phytoextraction, phytofiltration, phytovolatilization and phytostabilization. Phytoremediation are used frequently for remediation around the world and its development includes using well-understood technology and genetic engineering to increase its effectiveness. Microremediation is another promising technology in bioremediation of toxic metals and consists of 6 major mechanisms which are biosorption, bioaccumulation, biotransformation, bioleaching, biomineralization and microbially-enhanced chemisorption of metals. Microremediation is mainly in research phase and its development includes identifying new species, combining with phytoremediation and genetic engineering. Vermiremediation is another rapidly developing technique in bioremediation of toxic metals, assisting other bioremediation by burrowing actions of earthworms and its excretion, and accumulating toxic metals inside their bodies. Vermiremediation is also in research phase but it is rapidly developing. Generally, bioremediation is around 60% cheaper than traditional remediation methods and no pollutants are emitted during the process. However the remediation process is slow and generally takes longer than a year. Sources of toxic metals in contaminated areas in Hong Kong are mainly due to historic industrial discharge although present activities also contribute. Potential areas include sites for electronic waste activities, sediments of Kwun Tong typhoon shelter and sediments of Tolo Harbour. / published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

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