This study conducts a quantitative risk analysis (QRA) of wastewater treatment processes and biofilm management at Melbourne’s Eastern Sewage Treatment Plant. Established in 1975, the plant has continuously upgraded its processes to meet evolving environmental and social needs. Using MATLAB, this study evaluates Chlorine concentration (Clc) and Escherichia coli (E. coli) counts, finding that while E. coli levels comply with standards, Clc often exceed limits, posing environmental and health risks. Proposed risk management strategies include enhancing coagulation and flocculation, using corrosion inhibitors, implementing pipeline heating, adjusting pH levels, and continuous monitoring. These strategies aim to mitigate identified risks, ensuring safe and compliant wastewater treatment. Despite limitations such as small sample sizes and the need for comprehensive data collection, the study provides valuable insights for improving treatment processes and ensuring high-quality water delivery. Future research should address these limitations to enhance the robustness of the analysis.