Browsing by Subject "fecal indicator bacteria"

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    From Shipping to Swimming: Bacterial Monitoring and Diversity in Ballast Treatment Systems and Recreational Waters
    (2021-08) DeGuire, Lisa
    The use of indicator organisms as a proxy for pathogenic bacteria significantly reduces the cost and complexity of monitoring aquatic systems. Fecal indicator bacteria, such as Escherichia coli and Enterococcus spp., are commonly used by governmental agencies in recreational beach monitoring, wastewater treatment, and more recently as a tool in ballast water management. This research utilized culture-based and molecular techniques (qPCR and DNA sequencing) to explore two different applications of indicator bacteria: (1) a bench-scale experiment to explore the effectiveness of ballast water treatment techniques in freshwater and (2) an investigation of the sources of fecal contamination in a small Lake Superior tributary and surrounding recreational beaches. The ballast experiment addressed whether indicator bacteria are truly representative of other potentially harmful microbes after treatment (UV light and chlorination), as well as the scale of post-treatment bacterial regrowth. Both treatment techniques resulted in 99% reductions in culturable indicator and heterotrophic bacteria immediately following treatment (68-99% reductions when measured by qPCR). After 5 days, however, both lab and field incubations showed considerable regrowth of total bacteria (not reflected in indicators) and a distinct shift in bacterial community composition, including the regrowth of multiple pathogen containing genera (particularly Acinetobacter, Flavobacterium, Pseudomonas). The microbial source tracking project used library-independent and library-dependent methods to identify the sources of elevated E. coli in the recreational waters of Two Harbors, MN. Culturable E. coli abundance was correlated with turbidity and storm events, while human fecal sources appeared to be site-specific and independent from weather conditions. Both projects highlight the benefits and limitations of indicator bacteria in water quality monitoring and reinforce the importance of layering multiple analysis techniques to provide a more comprehensive understanding of microbial communities in ballast treatment systems and recreational waterways.
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    Occurences and Temporal Dynamics of Pathogens and Antibiotic Resistance Genes in Different Stormwater Reuse Systems
    (2021-12) Walsky, Tamara
    Stormwater is increasingly considered as an alternative water source for both potable and non-potable uses. However, stormwater has not been widely used as an alternative water source, primarily due to a lack of knowledge about the presence and risks associated with pathogens and antibiotic resistance genes present in raw and treated stormwater and how these populations change with environmental conditions. In my thesis research, five different stormwater reuse systems (SRS) in the Twin Cities metro area were sampled from every three weeks from June to October 2019 to build a comprehensive data set for analysis of temporal dynamics of pathogens and metal and antibiotic resistance genes (MRG/ARG) in raw and treated stormwater samples. As a follow up, two sites were time intensively sampled (i.e., sampled every 20-40 minutes as the SRS ran and water flowed through to irrigate fields) twice in summer 2020, along with tap water and lake water control sites. Microfluidic qPCR, a high-throughput quantification tool provided microbial data for 23 bacterial pathogens, 11 viral pathogens and 48 MRG/ARGs along with physiochemical testing such as turbidity, free and total chlorine, and water temperature to evaluate environmental conditions. Correlations between pathogen and MRG/ARG levels and environmental parameters such as temperature and precipitation assess the impact of precipitation and other environmental variables on pathogen and MRG/ARG concentrations in stormwater both over the season (2019 research) and during an average run where hundreds to thousands of gallons of water may be used (2020 research.) Viral and bacterial pathogens were sporadically detected both years while MRG/ARGs were widely detected. Environmental variables loosely correlated along known patterns with Fecal Indicator Bacteria (FIB) but did not account for any variation and lack of distinguished patterns seen in the data. The system with UV treatment and the system with a ball and bag filter sufficiently eliminated E. coli and limited the concentrations of MRG/ARG/pathogen genes, whereas the chlorinated system did not. SRS without any microbial treatment had no effect on cultured FIB and concentrations of MRG/ARG/pathogen genes. These results will provide previously unknown information crucial to successful expansion of stormwater reuse, especially for uses with greater human exposure.