Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Biology

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Arts

First Advisor

Dr. Robin Slawson

Advisor Role

Research Supervisor

Abstract

The need to understand how water treatment practices affect microbial biofilm communities is crucial for ensuring water quality and public health. Three distinct flow-through experiments using bench-scale drinking water distribution systems were conducted to explore the effects of orthophosphate (OP) under varying conditions. The first experiment examined the impact of residence time and OP addition on biofilm community dynamics. The second experiment investigated the influence of OP addition and substrate surface type (polycarbonate vs. polyvinyl chloride) on biofilm growth and community dynamics across different biofilm ages. The third experiment extended the findings to a different water source to assess the broader applicability of the results. In the first experiment, it was found that extended residence times and OP addition significantly influenced the genetic and functional profiles of biofilm communities, promoting higher biofilm reformation potential and increased heterotrophic plate counts (HPCs). The second experiment highlighted the critical role of substrate material in biofilm development. Biofilms formed on polyvinyl chloride (PVC) coupons exhibited higher HPCs and biofilm reformation potential compared to those on polycarbonate (PC) coupons, indicating that PVC materials facilitated more robust biofilm formation. Specifically, samples with added OP and PVC showed a CV assay absorbance of 2.313 OD at 590 nm, while samples with added OP and PC had a CV assay absorbance of 2.052 OD at 590 nm. The results from the third experiment, which compared biofilm formation in two different water sources, indicated that OP addition universally promoted biofilm growth and activity, although specific microbial community responses varied between the water sources. It was confirmed that OP addition led to higher biofilm HPCs, greater metabolic diversity, and distinct genetic clustering patterns, underscoring the fundamental impact of phosphorus availability on biofilm dynamics. In all three flow-through experiments, genetic analysis showed distinct shifts in microbial community structures, suggesting that OP addition created a more conducive environment for biofilm growth by providing essential nutrients like phosphorus. In summary, the study provided comprehensive insights into the effects of orthophosphate corrosion inhibitors on microbial biofilm communities in chloraminated Drinking Water Distribution Systems (DWDS). The findings emphasized the importance of considering both chemical additives and physical factors, such as substrate material and water source characteristics, in managing biofilm formation and maintaining water quality. These insights have practical implications for optimizing water treatment practices and ensuring the safety and reliability of DWDS.

Convocation Year

2024

Convocation Season

Fall

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Available for download on Sunday, August 22, 2027

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