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Due to environmental health and nutrient impact concerns, the conventional on-site sewage collection, treatment, and disposal systems are no longer able to meet the nutrient reduction requirements for wastewater effluent and may represent a large fraction of pollutant loads. The loads include not only nitrogen (N) and phosphorus (P), but also pathogens such as fecal coliform and E. coli which indicate the presence of other disease-causing bacteria flowing into aquatic system that adversely affect public health. A subsurface upflow wetland, which is an effective small-scale wastewater treatment system with low energy and maintenance requirements and operational costs, fits the current nutrient and pathogen removal situation having received wide attention throughout the world. Within this research study, a subsurface upflow wetland system (SUW), including four parallel SUW (three planted versus one unplanted), were constructed as a key component of the septic tank system receiving 454 liters per day (120 GPD) influent using the green sorption media along with selected plant species. It was proved effective in removing both nutrients and pathogens. During a one month test run, the planted wetlands achieved a removal efficiency of 84.2%, 97.3 %, 98.93 % and 99.92%, compared to the control wetland, 10.5%, 85.7 %, 99.74 % and 100.0 %, in total nitrogen (TN), total phosphorus (TP), fecal coli and E.Coli, respectively. Denitrification was proved to be the dominant pathway for removing N as evidenced by the mass balance and real-time PCR analyses. A simplified compartmental dynamics simulation model of constructed subsurface upflow wetlands was also developed to provide a dependable reference and tool for design of constructed subsurface upflow wetland.

Flavobacterium psychrophilum, the causative agent of bacterial cold water disease (BCWD), is tolerant of recommended ultraviolet (UV) doses used in recirculation aquaculture systems (RAS). Membrane filtration (MF) is used to remove pathogens from wastewater in many industries, but has not been thoroughly tested in RAS. In this study, bacterial removal efficiencies were assessed between MF and UV treatments over 30 days in an RAS. Bacterial removal efficiencies were not significantly different (p > 0.05) between MF and UV treatments, which removed 98.5 ± 0.4 % and 99.6 ± 0.1 % of total bacteria and 93.2 ± 5.2 % and 92.5 ± 4.1 % of heterotrophic bacteria, respectively. Under laboratory conditions, a MF system was challenged with concentrated doses of F. psychrophilum and achieved 5.8 ± 0.2 log reductions of the pathogen. Therefore, MF represents a potential alternative to UV irradiation and could be used to reduce the prevalence of F. psychrophilum in RAS, potentially reducing the incidence of BCWD and its impact on the aquaculture industry. / Environment Canada and Ontario Ministry of Agriculture, Food and Rural Affairs.

Doctor of Philosophy / Food Science Program / Daniel Y.C. Fung / Curtis L. Kastner / This dissertation was designed to evaluate antimicrobial, quality, and shelf life effects of controlled phase carbon dioxide (CPCO2) on beef trimmings destined for ground beef. Critical parameters included pressure, temperature, exposure times, modified atmosphere conditions, and days of simulated retail display. 1500 psi CPCO2 for 15 min achieved 0.83, 0.96, 1.00, and 1.06 log reductions for Total Plate Count (TPC), Generic E. coli (GEC), E. coli O157:H7 (O157), and Salmonella spp. (SS), respectively. Bacterial reductions in ground beef and beef trimmings were similar (P≥0.05). CIE L*, a*, and b* values in raw patties showed no differences (P≥0.05) immediately after CPCO2 application on beef trimmings. Nevertheless, significant (P<0.05) interactions were found in pressure by packaging for L*, in pressure by packaging by days of simulated retail display for a*, and in packaging by days of simulated retail display for b* scores. Nevertheless, after 5 days of simulated retail display, L*, a*, and reflectance (630/580nm) ratios were similar for all treatments (P≥0.05), and b* scores were most acceptable with 1500 CPCO2 (P≥0.05), regardless of the packaging conditions. After 5 days of display, cooked patties showed similar (P≥0.05) values for crude protein (%CP) and crude fat (%CF), the extent of lipid oxidation (TBARS), was higher (P0.05) in aerobic trays than flushed packages with 100% CO2. Ground beef patties manufactured from beef trimmings treated with CPCO2scored higher values for tenderness (P0.05) than other treatments. In addition, no differences (P0.05) for juiciness, beef flavor intensity, or off flavor intensity were found between non-treated and the 1500 psi CPCO2 treated patties. Microbial control of spoilage organisms and foodborne pathogens in ground beef patties with CPCO2 application in beef trimmings was effective (0.6 to 1.2 logs). Lethality levels are comparable to other intervention strategies. Discoloration of beef trimmings after CPCO2 application may not be a concern for grinding purposes. Further packaging with 100% CO2 is viable for controlling spoilage and pathogenic microorganisms after packaging and during refrigerated storage, although discoloration of raw ground beef patties packaged with 100% CO2 may be a concern for product marketing.

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