Ozonation is an integral process in ozone-biofiltration treatment systems and is beginning to be widely adopted worldwide for water reuse applications. Ozone is effective for pathogenic inactivation and organics oxidation: both increasing assimilable organic carbon for biofiltration and eliminating trace organic contaminants which may pose a threat to human health. However, ozone can also form disinfection byproducts such as bromate from the oxidation of naturally occurring anion bromide. Bromate is a known human carcinogen and is regulated by the EU, WHO, and USEPA to a maximum limit of 10µg/L. In waters high in bromide, especially above 100µg/L, bromate formation becomes a major concern. In the secondary wastewater effluent studied, bromide concentration may exceed 500µg/L. Several bromate suppression techniques have been devised in previous work, including free ammonia addition, monochloramination, and the chlorine-ammonia process. While free ammonia addition was not found to adequately reduce bromate formation below the required MCL, monochloramine addition and the chlorine-ammonia process were found to be effective. However, the impact of these chemical suppression techniques on organics oxidation and disinfection has not been fully studied. This study explored the impact of these bromate suppression techniques at a wide range of ozone doses on bromate formation, pathogenic inactivation, ozone-refractory organics oxidation through the surrogate 1,4-dioxane, and N-nitrosodimethylamine (NDMA) formation. Additionally, bromate suppression mechanisms of monochloramine were explored further through a variety of different water quality parameters, such as through hydroxyl radical exposure and ultraviolet absorption spectrum measurements, which were correlated and utilized to develop a hydroxyl radical exposure predictive model. / Master of Science / Ozone is a powerful oxidant used in water treatment in order to degrade contaminants of emerging concern into less harmful moieties and to inactivate pathogens. Upon application to process water, ozone quickly reacts with constituents in the water to form hydroxyl radicals: the most powerful oxidant in water treatment. These hydroxyl radicals, though with extremely short half-lives, are able to degrade ozone-recalcitrant organics, such as 1,4-dioxane through a process called advanced oxidation. Ozone itself also has the capability of inactivating a multitude of pathogenic organisms, including viruses Giardia and Cryptosporidium parvum when specific contacts times are met. However, ozone does have the potential to form disinfection byproducts such as Nnitrosodimethylamine (NDMA) and bromate. NDMA, though not currently regulated by the United States’ Environmental Protection Agency (USEPA), has a drinking water health advisory limit of 10ng/L in the State of California. Bromate, on the other hand, is a known human carcinogen regulated to 10µg/L by the USEPA. Formed within the ozone system from the naturally occurring ion bromide, bromate can be limited through various chemical treatments such as ammonia addition, pH adjustment, monochloramination, and the chlorine-ammonia process. To date, these methods of bromate suppression have not been comprehensively studied in terms of bromate suppression as well as disinfection and organics oxidation in water reuse systems. The purpose of this research was to minimize bromate formation while ensuring NDMA formation was minimized, and disinfection and organics oxidation were maximized. Through this study, system efficiencies were improved and water quality for future generations will be improved.

In many drinking water systems in the United States, disinfectant is added to water as it leaves the plant to maintain a residual concentration in the distribution system. The disinfectant residual is maintained to inactivate contamination that enters the distribution system, to control biofilms, and to act as a sentinel for contamination in the distribution system. A model was developed to evaluate the potential effectiveness of the disinfectant residual at inactivating contamination. The model was used to examine contamination of a hypothetical distribution system through backpressure at a cross-connection under different operating conditions. The dilution and pathway of the hypothetical contaminant were examined as the contaminant moved through the system. Disinfection and inactivation kinetic relationships were used to model the inactivation of the contaminant in the system by the amount of disinfectant present. The model showed that both chlorine and chloramines in each decay and inactivation condition considered provided some benefit over no disinfectant at all when examining susceptible organisms. Chlorine, under medium and low decay conditions, provided the best inactivation. Where 29.8% of total node time steps received a contamination of concern in the absence of disinfectant residual, as low as 4.8% of total node time steps received a contamination of concern in the presence of disinfectant residual. Chloramines was found to persist longer in the distribution system, but resulted in much lower inactivation compared to chlorine. Disinfectant doses typical of common distribution system operation were able to reduce the impact of contamination once it entered the distribution system but, except for four cases, were unable to prevent contamination from spreading within the distribution system. Therefore, it was concluded that presence of a disinfectant residual will reduce the total number of exposure opportunities from a contamination event, but cannot be relied upon to eliminate the chance of exposure resulting from contamination. / Master of Science

The kinetics, products, and reaction pathways of triclosan/free chlorine reactions were investigated for the pH range 3.5-11. Although pH dependent speciation occurs in both triclosan and free chlorine, only the reaction between HOCl and the phenolate-triclosan was found to play a significant role in the kinetics. The second order rate constant for the reaction between phenolate-triclosan and HOCl was found to be 5.40 (±1.82) Ã 103 M⁻¹s⁻¹. Three chlorinated triclosan intermediates were tentatively identified based on mass spectral analysis. Additionally, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and chloroform formed under excess free chlorine conditions. The majority of the chloroform formed during the reactions does not form via 2,4-dichlorophenol and 2,4,6-trichlorophenol oxidation. Therefore, the majority of chloroform is likely formed via the oxidation of triclosan's phenolic ring. Based on the identified products, a reaction pathway was proposed for the oxidation of triclosan in the presence of free chlorine. / Master of Science

Toxic shock events can be detrimental to wastewater treatment systems and can result in long-term losses of system performance. If warned of an impending toxic shock, operators would have the opportunity to implement process controls that could help mitigate the effects of the shock event. The objective of this project was to evaluate the effectiveness of a developed corrective action strategy (involving aerobic endogenous respiration) on an enhanced biological phosphorus removal (EBPR) wastewater treatment plant (WWTP) shocked with chlorine. Three identical, laboratory-scale systems were designed to mimic one train of the Long Creek Water Resources Reclamation Facility (WRRF, Gastonia, NC). The basis of this study is a comparative performance analysis among the three trains; a negative control (unshocked and operated normally), a positive control (shocked with hypochlorite and operated normally), and the corrective action (shocked with hypochlorite and process controls implemented). Comparative performance analysis among the three trains was based on effluent quality, performance stability, and biomass kinetics as indicated by rates of respiration and phosphate release and uptake. The shock event and corrective action strategy both inhibited EBPR. After an initial perturbation, the positive control matched the performance of the negative control. The corrective action, however, exhibited significant instability in EBPR performance. Regardless of whether aerobic or anaerobic sludge storage conditions are selected, endogenous respiration will still result in system instability. It is recommended, therefore, that measures be taken to avoid imposing endogenous conditions on isolated sludge during a short-term toxic shock event. / Master of Science

The concentrations of chlorine dioxide (CI02), chlorine, chlorite (CIO2), and chlorate (CI03) were evaluated following pretreatment of raw water by CI02 at water treatment plants in New Castle, Pennsylvania; Charleston, West Virginia; Skagit, Washington; and Columbus, Georgia. Chlorite and chlorate concentrations were unaffected by any of the water treatment processes and did not vary as a function of time of travel in the distribution system. Chlorine dioxide, which was analyzed on-site at two water treatment plants, reformed in the clear well and in the distribution system following post chlorination. The chlorite-removal capability of powdered activated carbon (PAC) was evaluated in both laboratory- and pilot-scale studies. Chlorite removal by PAC in laboratory studies decreased with increasing pH over a range from pH 5.5 to 7.5 and varied with the type of PAC. Chlorite was reduced to chloride at pHs ranging from 5.5 to 7.5, but CI03- formed at the pH 5.5 through 6.0. The pilot plant study; which was conducted at Newport News, Virginia; evaluated CI02 removal by PAC enmeshed in a floc blanket in a pulsed-bed, solids-contact clarifier. An average of 27 percent of the CI02 was removed when the PAC dose was 10 mg/L PAC and 57 percent when it was 20 mg/L PAC. Chlorate was not removed by PAC, but the concentrations could be reduced if the CIOz generator was properly operated. / Master of Science

In an effort to provide wastewater treatment operators with the capability to be proactive in assessing and solving deflocculation events, this study has tested the components of a biosensor to predict deflocculation and investigated the mechanistic cause of deflocculation relating to chlorination of activated sludge cultures. In order to effectively manage upset events, it is necessary to know the source of an upset and the causative mechanism that the source initiates. The Glutathione-gated potassium efflux (GGKE)induced activated sludge deflocculation biosensor incorporates novel microtechnology with a whole cell biological element to predict deflocculation from electrophilic sources. This sensor utilizes microfluidic channels to conduct influent wastewater across a biofilm of Eschericia coli K 12 and monitors the bacterial response to the influent. The bacterial response, which is efflux of K+ ion from the cytoplasm, is monitored with a fluorescence-based sensor called an optode. The components of the system satisfy the project requirements, which include minimal expense (both operation and manufacture), on-line capability and minimal maintenance. The research conducted to date demonstrates the ability of the components of the biosensor to fulfill the design requirements. The optode K+ detector successfully measured an increase in soluble K+ following the exposure of E. coli K-12 to the electrophile N ethyl malemide. The manufacture of the microfluidic device has been completed and the device has demonstrated the ability to conduct influent under negative pressure across an established biofilm with the optode in place. The establishment of a biofilm under expected hydrodynamic conditions has also been completed. Future research efforts will include integrating the components of the biosensor into a working prototype that will be capable monitoring the reaction of bacteria to the presence of electrophilic compounds in wastewater. Sensors of this nature will provide operators with the early warning necessary to be proactive against toxic upsets rather than reactive. The knowledge needed to create a biosensor resides in the identification of bacterial response mechanisms that cause upset events in wastewater treatment facilities. The biosensor that has been developed relies on the discovery of the link between electrophile-induced GGKE and activated sludge deflocculation. Research has been concluded, which expands the role of GGKE and activated sludge deflocculation to include chlorine-induced GGKE. Through a series of laboratory-scale reactors, a relationship has been established between chlorine addition to control filamentous bulking, increased soluble K+ levels and an increase in effluent suspended solids . The results demonstrate that the addition of chlorine to control filamentous bulking may elicit the GGKE mechanism, initiating activated sludge deflocculation, similar to observations of chlorination at full-scale activated sludge wastewater treatment facilities. Establishing a mechanistic cause of deflocculation related to chlorination will permit operators to apply chlorine in a manner that may avoid deflocculation, rather than reacting to deflocculation after it has occurred. / Master of Science

M. S.

Carbamazepine (CBZ) is an antiepileptic drug widely detected in drinking water supplies and wastewater effluent. It has been previously found that CBZ is recalcitrant to biological removal processes. Therefore, active CBZ will be exposed to wastewater effluent disinfection processes, which for most treatment plants in the United States involves the addition of free chlorine. However, the chlorination mechanisms of CBZ have not been fully investigated and are currently poorly understood. Our experimental studies were conducted to examine the chlorination of CBZ under controlled conditions. The kinetics, products, and reactivity of CBZ/free chlorine reactions were investigated over the pH range of 5.5-10. Results show that free chlorine reacts with CBZ and the reactivity is pH dependent. Furthermore, the results indicate that temperature affects the reactivity of CBZ with free chlorine. The temperature experiment results were fitted with the Arrhenius equation. The calculated Ea and A values are 48.8 kJ/mol and 1.41x104 s-1, respectively. Four common intermediates were detected based on both UV and mass spectral analysis proposed structures were developed based on m/z from mass spectra. / Master of Science

Mycobacterium avium and Mycobacterium intracellulare are environmental opportunistic pathogens whose source for human infection is water and soil. M. avium and M. intracellulare cause pulmonary infections (tuberculosis) in immunocompetent individuals and bacteremia in immunodeficient individuals (e.g. AIDS). One factor likely influencing the lack of success of antibiotic therapy in patients would be their ability to form biofilms. Growth in biofilms might result in antimicrobial resistance because (1) cells are protected by layers of other cells and extracellular material (2) and differences in physiologic state of cells as a consequence of growing on surfaces. The objectives of the work were to (1) establish methods for reproducible growth of mycobacterial biofilms (2) measure the formation of biofilms on surfaces by cells of M. avium and M. intracellulare (3) measure the antibiotic- and chlorine- susceptibility of M. avium and M. intracellulare strain TMC1406T in cell grown in suspension, cells grown in biofilms and suspended and of cells grown in biofilms (4) measure the hydrophobicity of M. avium and M. intracellulare grown in suspension and in biofilms. Methods were developed for growing mycobacteria in biofilms in polystyrene flasks and on glass beads. Although both strains formed biofilms, M. intracellulare strain TMC 1406T more readily formed biofilms than M. avium strain A5 in polystyrene flasks. The majority of M. intracellulare strain TMC 1406T cells grew on the walls of the flasks rather than in suspension like M. avium strain A5. The susceptibility of M7H9 medium-grown cells of M. avium strain A5 and M. intracellulare strain TMC 1406T cells grown in suspension, cells grown in biofilms and suspended and cells grown in biofilms was measured against clarithromycin, ethambutol, kanamycin, rifampicin and streptomycin. Cells grown in biofilms and exposed to antibiotics in biofilms were five-fold resistant to antibiotics than were cells grown in biofilms and exposed in suspension. Cells grown and exposed in suspension were ten-fold more sensitive to antibiotics than were cells grown in biofilms and exposed in suspension. The chlorine susceptibility of cells grown in medium and water was also measured. Cells grown in biofilms were more resistant to chlorine than cells grown in biofilms and suspended. Cells grown in suspension were more sensitive to chlorine than cells grown in biofilms and suspended. The hydrophobicity data (i.e., hexadecane adherence and contact angle measurements) showed that cells grown in biofilms are more hydrophobic than cells grown in biofilms and suspended and cells grown in suspension. It is clear that there are physiological changes between cells grown in suspension, cells grown in biofilms and suspended and cells in biofilms. / Master of Science

In this problem, an attempt was made to determine the fate of various species of bacteria which had previously been isolated from other sources when inoculated into Denton tap water.