Thesis (M.S.)--Simon Fraser University, 1998. / Includes bibliographical references (leaves 141-149).

This study investigated the short-term inhibitory effects of 8 chlorinated compounds on aquatic microorganism heterotrophic activity. A technique involving the measurement of substrate uptake rates using radio-actively labeled glucose was employed. All compounds studied have been identified as foreign pollutants in aquatic environments and include the highly toxic ones DDT, dieldrin and a PCB (Aroclor 1254). The aquatic microorganisms were predominatly bacteria. On a short-term basis, the PCB and tetrachlorophenol were the most toxic pollutants, decreasing the maximum glucose uptake rate (Vmax) by 50 percent at 250 ppb concentrations. The remaining pollutants had little effect under 2500 ppb. In addition, tetrachlorophenol was the only compound to significantly increase glucose turnover time (Tt). Results from other experiments were: the toxicity of tetrachlorophenol varied according to the (environmental) water temperature; tetrachlorophenol affected the uptake of glucose more than that of two amino acids, alanine and glutamic acid; with respect to di-, tri-, and tetrachlorophenol, neither the chlorine percentage per pollutant molecule, nor the number of pollutant molecules per mole of water, varied linearly with the pollutant's ability to inhibit glucose uptake; the combined toxicities of various pollutants reduced uptake to only 9 percent below the average of their separate effects; and none of the 4 pollutants tested for long-term effects (DDT, PCB, dieldrin and tetrachorophenol) inhibited uptake after 4 days. It was concluded that the two tests (Type I and Type II as described in Section 2) were quick and reliable techniques for assessing the short and long-term effects of a concentration of a pollutant on heterotrophic activity. It was also determined that other pollutants should be tested for their long-term effects under a variety of conditions (for example, their effects on different substrates and on the sediment microbial community). / Science, Faculty of / Zoology, Department of / Graduate

Halogenated organic compounds have had widespread and massive applications in industry, agriculture, and private households, for example, as degreasing solvents, flame retardants and in polymer production. They are released to the environment through both anthropogenic and natural sources. The most common chlorinated solvents present as contaminants include tetrachloroethene (PCE, perchloroethene) and trichloroethene (TCE). These chlorinated solvents are problematic because of their health hazards and persistence in the environment, threatening human and environmental health. Microbial reductive dechlorination is emerging as a promising approach for the remediation of chlorinated solvents in aquifers. In microbial reductive dechlorination, specialized bacteria obtain energy for growth from metabolic dechlorination reactions that convert PCE to TCE, cis-1,2-dichloroethene (cDCE), vinyl chloride (VC), and finally to benign ethene. Field studies show incomplete dechlorination of PCE to ethene due to lack of electron donors or other populations competing for the electron donor. Mathematical models are good tools to integrate the processes affecting the fate and transport of chlorinated solvents in the subsurface. This thesis explores the use of modeling to provide a better understanding of the reductive dehalogenation process of chlorinated solvents and their competition with other microorganisms for available electron donors in continuous flow systems such as a continuous stirred tank reactor (CSTR) and a continuous flow column. The model is a coupled thermodynamic and kinetic model that includes inhibition kinetics for the dechlorination reactions, thermodynamic constraints on organic acids fermentation and has incorporated hydrogen competition among microorganisms such as homoacetogenesis, sulfate reducers and ferric iron reducers. The set of equations are coupled to those required for modeling a CSTR. The system of model equations was solved numerically using COMSOL 3.5 a, which employs finite-element methods. The kinetic model was verified by simulation results compared to previously published models and by electron balances. The simulation process progressed by simulating the anaerobic reductive dechlorination, coupled with thermodynamic limitation of electron donor fermentation in batch systems to the modeling of CSTR, and finally to simulate anaerobic reductive dechlorination in continuous flow column, aquifer column including the processes of advection, dispersion and sorption along with the microbial processes of dehalogenation, fermentation, iron and sulfate reduction. The simulations using the developed model captured the general trends of the chemical species, and a good job predicting the dynamics of microbial population responses either the CSTRs or continuous flow column. Although, the kinetic of anaerobic dechlorination processes of chlorinated solvents in those systems have been researched in the past, little progress has been made towards understanding the combined effects of the dechlorination and thermodynamic constraints in continuous flow systems. This work provides a rigorous mathematical model for describing the coupled effects of these processes. / Graduation date: 2012