The disposal of infectious medical waste has become a major environmental concern. New disposal methods are currently being investigated; one of these is a bioremediation process which utilizes enzymes in a batch reactor to render the waste noninfectious. The success of this biological process depends on (among other things) two mechanisms: the diffusion of the disinfecting enzymes into small crevices within the waste stream and the breakdown of cellulose-derived material by cellulase enzymes. It was found that the waste stream contained a variety of small crevices which could possibly contain pathogens. Circulation in these crevices was restricted by their small openings and one must rely on diffusion of enzymes to disinfect their interiors. Numerical models for the diffusion of enzymes within one-dimensional and re-entrant crevices were developed and a method for comparing various re-entrant crevices was presented. From these models a conservative method for determining approximate disinfection times for the crevices was described. It was determined from this conservative method that most crevices within the waste will either be disinfected during the process or shortly thereafter. This biological process also utilizes cellulases to breakdown the paper within the waste stream. Small-scale simulated waste experiments were conducted with cellulases to determine the increase in maximum mixable solids concentration and the mass reduction of the waste due to cellulase activity. The addition of cellulases to the slurry more than doubled the waste concentration which could be agitated and reduced the agitator shaft power by as much as 50% when compared to the simulated waste tests with no cellulase. Significant mass reduction was also observed with the addition of cellulases to the slurries. Small-scale breakdown experiments were conducted with and without cellulases using newsprint as the substrate. These experiments were performed to determine the influence of cellulose hydrolysis by cellulases on agitator power. A simple mathematical model was developed and presented which described this phenomenon. / Master of Science

"Anaerobic Stabilization" (AnS) is a phenomenon previously observed in biological nutrient removal (BNR) systems that use anaerobic-aerobic sequencing for phosphorus and/or nitrogen removal. AnS manifests itself in the form of less-than-theoretical oxygen requirements for the extent of organics stabilization observed. The objectives of this study were to develop an improved methodology for the quantitative determination of AnS, verify the occurrence and validate the statistical significance of AnS, identify components of the AnS-related redox balance, and investigate possible explanations for AnS. A lab-scale continuous-flow A/O¹ system was operated with chemical inhibition of nitrification at a 12-hour nominal HRT, 10-day BSRT (Biological Solids Retention Time), 1Q RAS flow, and varying synthetic feed compositions. Data from this system were used to demonstrate that, by eliminating the need to quantify the clarifier OUR, the Boundary Exchange AnS determination method developed in this study afforded a major advantage over earlier methods. Non-zero AnS was shown to be a statistically significant, reproducible phenomenon. Carbon, oxygen, and sulfur were identified as the three main elements affecting AnS in the A/O system studied. A second lab-scale A2/O system operating at a 6-hour nominal HRT, 5-day BSRT, 1Q RAS flow, and 2Q RNX flow, and receiving raw municipal wastewater feed spiked with acetate, was uSed in conjunction with the A/O system to study possible AnS explanations. A combination of processes accounted for varying percentages of observed AnS. Hydrogen production explained 0.1 percent or less, while methane production explained almost 19 percent with formate in the feed but no more than 0.8 percent without it. Aeration-induced Stripping of reduced volatiles explained up to 6 percent. Attempts to identify the reduced volatiles revealed traces of ethanol but no n-butanol in the A2/O system. Limitations of the COD test were identified as a possible explanation for AnS that warrants further investigation. A unified speculative biochemical model consistent with all results of this study and with established theory, and capable of partially explaining observed AnS, is proposed in this study. ¹A/O and A2/O are trademarks of Air Products and Chemicals, Inc., Allentown, PA, U.S.A. / Ph. D.

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