Potential contaminants in rainwater after a bushfire

Area of Science:

• Environmental Chemistry
• Water Quality Management
• Bushfire Impact Assessment

Background:

• Domestic rainwater tanks are common in Australia, especially rural areas.
• Bushfires can contaminate harvested rainwater with ash and chemicals.
• Current advice to drain tanks causes distress to bushfire-affected landholders.

Purpose of the Study:

• To assess the contamination of domestic rainwater tanks after bushfires.
• To evaluate the effectiveness of common water filters.
• To provide evidence-based advice for rainwater tank use post-bushfire.

Main Methods:

• Artificially contaminated water was created using bushfire-related chemicals (e.g., treated timber ash, firefighting foam).
• Two commercially available water filter systems were tested for contaminant removal.
• Water quality was analyzed against nonpotable use guidelines.

Main Results:

• Artificially contaminated water met nonpotable guidelines for irrigation and stock watering.
• Tested filters removed some, but not all, contaminants.
• Bushfire-affected rainwater is likely safe for non-drinking purposes.

Conclusions:

• Landholders should be advised that tank water post-bushfire is generally safe for non-potable uses.
• Retaining rainwater for recovery purposes is encouraged, reducing distress.
• Potable use of bushfire-affected rainwater should be avoided without further treatment or testing.