Water quality and physical impact of bushfire on HDPE & PVC-M reticulation pipes

In recent years severe bushfire events have damaged the distribution assets of some water operators and contaminated drinking water. To ensure clean and safe drinking water, preventing contamination and asset failure are key planning areas for water operators to achieve bushfire resilience. Most simulated bushfire research has focussed on small diameter plastic service-line and domestic water lines, while the analysis of larger diameter reticulation pipes and the physical impacts of bushfire on these assets remains largely unaddressed. To address this, experiments with HDPE and PVC reticulation and domestic pipe samples were conducted. Following four-hour thermal exposure at 200 °C, samples were stagnated in test-water from which aqueous contamination was determined. Aqueous benzene, which exceeded Australian health guideline levels for drinking water, was detected at 0.024 mg/L in test-water stagnated with all PVC reticulation samples, however, was not detected in HDPE reticulation samples. Differential scanning calorimetry was used to predict changes in pipe physical performance. For new HDPE reticulation pipe samples, significant antioxidant loss was evident, reducing the useful life of pipes and making them more prone to failure. This implied that older pipes with prior antioxidant loss may be more susceptible to reduced performance due to bushfire exposure. For new PVC reticulation pipe samples, simulated bushfire exposure resulted in significantly increased gelation, an indicator of pipe brittleness. These findings contribute to a deeper understanding for water operators, researchers, and private drinking water system users of the potential for severe bushfire to impact drinking water quality and the resilience of distribution assets.