Bioremediation of PCBs from Composted PCB-Accumulating Plants
J. Scott Greenwood, Royal Military College of Canada, Kingston, Ontario, Canada
A. Barbara Zeeb, Royal Military College of Canada, Kingston, Ontario, Canada

Maintaining Neutral pH in Deep Soils and Ground Water with Insoluble Colloidal Buffers
James Piegat, Remediation and Natural Attenuation Services, Inc., Brooklyn Center, MN
William A. Newman, Remediation and Natural Attenuation Services, Inc., Brooklyn Center, MN

Changes in the Structure of the Microbial Community of a PAH-Contaminated Soil During Bench-Scale Bioremediation
Caroline G. Rose, Health Canada, Ottawa, Ontario, Canada
Paul A. White, Health Canada, Ottawa, Ontario, Canada
Iain Lambert, Carleton University, Ottawa, Ontario, Canada
Suzanne Paterson, Carleton University, Ottawa, Ontario, Canada

Biosurfactants from Acinetobacter calcoaceticus BU03 Enhance the Bioavailability and Biodegradation of Polycyclic Aromatic Hydrocarbons (PAHs)
Jonathan W.C. Wong, Hong Kong Baptist University, Hong Kong SAR, P.R. China
Z. Y. Zhao, Hong Kong Baptist University, Hong Kong SAR, P.R. China

Bioremediation of Organochlorine Pesticides Contaminated Soil with Microemulsion
GY Zheng, Hong Kong Baptist University, Hong Kong SAR, P.R. China
J.W.C Wong, Hong Kong Baptist University, Hong Kong SAR, P.R. China

Bioremediation of PCBs from Composted PCB-Accumulating Plants

Student Presenter

J. Scott Greenwood, Dept. Chem. & Chem. Eng., Royal Military College of Canada, PO Box 17000 Stn Forces, Kingston, Ontario K7K 7B4, Canada, Tel: 613-541-6000 ext. 6900, Fax: 613-542-9489, Email: scott.greenwood@rmc.ca
A. Barbara Zeeb, Dept. Chem. & Chem. Eng., Royal Military College of Canada, PO Box 17000 Stn Forces, Kingston, Ontario K7K 7B4, Canada, Tel: 613-541-6000 ext. 6713, Fax: 613-542-9489, Email: zeeb-b@rmc.ca

Polychlorinated biphenyls (PCBs) are ubiquitous organic xenobiotics posing significant environmental and health risks as a result of their toxicity and recalcitrance to remediation.  Until banned from North America in the 1970s, PCBs were sold as mixtures of congeners, possessing between one and nine chlorine atoms attached to a biphenyl ring.  Traditionally incineration has been used, at great environmental and monetary cost, to dispose of PCBs.  A significant market seeking alternative remediation technologies now exists. 

It has been demonstrated that Cucurbita pepo ssp pepo cv. Howden (pumpkin) can extract PCBs from contaminated soil and subsequently translocate PCBs from the plant roots to shoots (Zeeb et al., 2006, Whitfield Aslund et al., 2007).  My research will measure the congener profile of PCBs in pumpkin xylem, and hence develop a better understanding of PCB mobility within plants.  It is expected that knowledge on the mechanism of congener transport will lead to enhancements of contaminant uptake. 

Pumpkin biomass containing translocated PCBs will be harvested and analyzed for congener profile at the end of the 2009 growing season.  A controlled greenhouse study will document the effects of composting on congener biotransformation and biomass reduction.  It is expected that composting the contaminated biomass will greatly concentrate PCBs within humic matter, thus reducing the volume of material that may ultimately require storage or incineration.

Finally, a bench-scale bioremediation study using composted PCB phytoextractors (i.e. C. pepo plants) will be undertaken to document the dechlorination of highly chlorinated PCB congeners under anaerobic conditions.  Successful anaerobic dechlorination would prepare the humus for the possibility of subsequent aerobic PCB mineralization.  My research will seek to develop a better understanding of PCB congener movement and transformation from contaminated soil to plant to compost in an effort to ameliorate PCB remediation in an environmentally friendly and cost-effective manner.  Preliminary results of the three discussed studies will be presented.   

Maintaining Neutral pH in Deep Soils and Ground Water with Insoluble Colloidal Buffers

James Piegat, Remediation and Natural Attenuation Services, Inc., 6712 West River Road, Brooklyn Center, MN, 55430, USA, Tel:  763-585-6191, Fax:  763-585-6195, Email:  jpiegat@RNASinc.com
William A. Newman, Remediation and Natural Attenuation Services, Inc., 6712 West River Road, Brooklyn Center, MN, 55430, USA, Tel:  763-585-6191, Fax:  763-585-6195, Email:  bnewman@RNASinc.com

Optimal pH for most biodegradation processes falls between 6.5 and 8.5.  Enhanced bioremediation in poorly buffered soils and ground water may lower pH below 6.5 as the added electron donor produces carbon dioxide and organic acids.  Soluble buffers are commonly lost within a relatively short time by ground water flow.  Colloidal buffer systems can be transported significant distances in the subsurface, yet have substantial retention in the soil or aquifer.  The agricultural practice of liming soils adjusts soil pH by mixing finely divided calcium carbonate into the shallow subsurface.  Conversely, delivering an insoluble solid buffer into deeper soils and ground water presents a formidable challenge.  Principal challenges include:  1) keeping particles in suspension during storage and transportation; 2) moving particles a useful distance through the soil or aquifer; 3) retaining sufficient buffer that will not be washed out by ground water flow after injection; and 4) minimizing permeability changes. 

Suspensions of micro- and nano-scale buffer particles were explored in soil columns.  Subsurface mobility of diluted suspensions is enhanced by controlling particle size and treating with additives to produce a negative surface charge.  Stable suspensions of insoluble buffer solids containing more than 500,000 mg/Kg of total alkalinity (as CaCO₃ equivalents) were produced through the use of optimal particle size and proprietary additives (U.S. patent pending).  These suspensions have been stored for six to twelve months without detectable settling, agglomeration or cementing of buffer particles.  Concentrated suspensions can be easily diluted with water by gentle mixing for injection into deep soils or ground water.  Column studies using sandy soils indicate effective transport of a suspension containing more than 20,000 mg/L total alkalinity with significant alkalinity retained in the soils and less than 10% permeability loss.  The commercial product is being tested in field trials and is marketed under the trademark Neutral Zone^®.

Changes in the Structure of the Microbial Community of a PAH-Contaminated Soil During Bench-Scale Bioremediation

Student Presenter

Caroline G. Rose, Health Canada, 50 Columbine Drwy, Ottawa, Ontario, K1A 0K9, Canada, Tel: 613-957-3135, Fax: 613-941-8530, Email: caroline_rose@hc-sc.gc.ca
Paul A. White, Health Canada, 50 Columbine Drwy, Ottawa, Ontario, K1A 0K9, Canada, Tel: 613-957-3135, Fax: 613-941-8530, Email: paul_white@hc-sc.gc.ca
Iain Lambert, Carleton University, 314 Nesbitt Building Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, K1S 5B6, Canada, Tel: 613- 520-2600 ext. 3893, Fax: 613- 520-2569, Email: iain_lambert@carleton.ca
Suzanne Paterson, Carleton University, 313B Nesbitt Building Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, K1S 5B6, Canada, Tel: 613- 520-2600 ext. 3651, Fax: 613- 520-2569, Email: suzanne_paterson@carleton.ca

The contamination of soils with PAHs, substances that can pose serious environmental and human health risks, is a serious international problem.  Removal of risk requires effective and sustainable methods to decrease or eliminate toxicological hazard.  Bioremediation is a sustainable option that can be accomplished by a variety of means, including in situ treatment.  However, due the limitations of classical culturing methods, there is a paucity of information regarding the composition of soil microbial communities, and moreover, the identity of organisms involved in contaminant catabolism.  Newer, molecular techniques that directly examine metagenomic DNA or RNA provide opportunities to investigate the genetic constitution of soil samples without the need for culturing.  The 16S ribosomal RNA gene has proved to be a valuable tool in the identification of soil microbes due to its highly conserved nature throughout the bacterial kingdom, in addition to inclusion of variable regions that are unique to a particular organism, or closely related group of organisms.  Isolation of total soil microbial DNA, amplification of the 16S gene region, cloning the 16S rDNA into chemically competent E. coli cells, and subsequent sequencing the 16S rDNA insert permits relatively rapid identification of soil microorganisms.  This study used analysis of 16S rRNA gene sequences to examine changes in the structure of the soil microbial community in a PAH-contaminated soil during bioremediation. When compared with previously observed changes in the chemical composition and mutagenic activity of the soil, it was noted that certain groups of organisms follow the chemical and toxicological trends.  This type of approach can be employed to evaluate innovative bioremediation methods, and moreover, identify members of the microbial community that are critical for the catabolism of PAHs.

Biosurfactants from Acinetobacter calcoaceticus BU03 Enhance the Bioavailability and Biodegradation of Polycyclic Aromatic Hydrocarbons (PAHs)

Jonathan W.C. Wong, Sino-Forest Applied Research Centre for Pearl River Delta Environment, Department of Biology, Hong Kong Baptist University, Hong Kong SAR, P.R. China, Tel: +852 34117056, Fax: +852 34112355, Email: jwcwong@hkbu.edu.hk
Z. Y. Zhao, Sino-Forest Applied Research Centre for Pearl River Delta Environment, Department of Biology, Hong Kong Baptist University, Hong Kong SAR, P.R. China, Tel: +852 34115835, Fax: +852 34112355, Email: zhaozy@hkbu.edu.hk

A thermophilic strain of Acinetobacter calcoaceticus, designated as strain BU03 isolated from petroleum contaminated soil, has exhibited biosurfactant producing capability. Biosurfactant produced by A. calcoaceticus BU03 is more effective in enhancing the solubility and desorption of PAHs than the chemical surfactant Tween 80 as well as the biosurfactant produced by Pseudomonas aeruginosa ATCC 9027. At 25 times its critical micelle concentrations (CMC), biosurfactant from BU03 significantly increased the apparent solubility and desorption of phenanthrene by 28.3-fold and 3.9-fold, respectively. In aqueous system, the biosurfactant produced by BU03 at sub-CMC concentrations increased the bioavailability of phenanthrene by increasing both the solubilization rate and the affinity of degradative cells to phenanthrene. Therefore, biosurfactants enhanced the extent and rate of biodegradation of phenanthrene by an isolated PAHs degradative strain, Bacillus subtilis B-UM. After confirmation of their ability to enhance the bioavailability of phenanthrene, the isolated biosurfactant was applied to a PAH contaminated soil in a thermophilic composting system. Within a composting period of 42 days, the removal ratio of phenanthrene and benzo[a]pyrene in the absence of biosurfactants were 71.2 and 16.4%, respectively. Inoculation of A. calcoaceticus BU03 or biosurfactant produced by this strain significantly increased the emulsification of soil, and therefore enhanced the desorption of PAHs from soil to aqueous phase in which they can be degraded by an inoculated degradative strain B-UM. Therefore, inoculation of A. calcoaceticus BU03 or biosurfactant from BU03 together with inoculation of B. subtilis B-UM increased the removal of benzo[a]pyrene to 83.8 and 68.3%, respectively, while almost all of phenanthrene was removed in these two treatments. The results gave sufficient evidence to affirm that the application of biosurfactants produced by A. calcoaceticus is an effective means to enhance the biodegradation of PAHs in thermophilic composting, while inoculation of biosurfactants producing strain to PAHs contaminated soil is a more practical and cost-effective approach than direct addition of biosurfactants.

Bioremediation of Organochlorine Pesticides Contaminated Soil with Microemulsion

Student Presenter

GY Zheng, Sino-Forest Applied Research Centre for Pearl River Delta Environment, and Department of Biology, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR, Tel: 852-3411-7056, Email: 07466099@hkbu.edu.hk
J.W.C Wong, Sino-Forest Applied Research Centre for Pearl River Delta Environment, and Department of Biology, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR, Tel: 852- 3411-7056, Fax: 852 3411 2355, Email: jwcwong@hkbu.edu.hk

Organochlorine pesticides, e.g., 1,2,3,4,5,6-hexachlorocyclohexane (HCH) and 1,1,1,-trichloro-2,2-bis (p-chlorophenyl) ethane (DDT) are a group of ubiquitous contaminants in soil that are biologically accumulated through food chain into human tissues and are potential hazard to human health. Threfore, it is imperative to develop effective and cost-saving techniques to remediate organochlorine pesticides contaminated soil as they have been frequently detected in high concentrations in soils and some vegetables in many countries. Many researches have revealed that bioremediation may be a promising alternative for removing organochlorine pesticides from soil. However, the efficiency of bioremediation could be severely handicapped by the low bioavailability of organochlorine pesticides. This study focuses on the feasibility of combining the bioremediation technique with microemulsion - a system containing water, surfactants, co-surfactants and oil phase, and to ascertain their ability in enhancing the bioavailability of organochlorine pesticides and remediate contaminated soil. Many surfactants, alcohol, and oils have been screened for the possibility of forming microemulsions and their efficiency in enhancing the solubility of both p,p-DDT and γ-HCH were also evaluated. Results indicated that microemulsions formed could enhance the solubilization of both p,p-DDT and γ-HCH, and the enhancement by microemulsions was much higher than that by the respective surfactant solutions alone. Besides that, for a particular microemulsion system, the solubilization capacity was positively influenced by both co-surfactant and oil contents present in them. Moreover, microemulsion system is more effective than surfactant solution in desorbing organochlorine pesticides from soils. The results of the study on the effect of the selected microemulsions on the biotransformation of p,p-DDT and γ-HCH in both aqueous and soil matrix is presented. It is expected that these results would lead to the development of an innovative, effective and economical technique to remediate organochlorine pesticides contaminated soil. 

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