Using treated wastewater to save wetlands impacted by climate change and pumping

Area of Science:

• Environmental science
• Hydrology
• Water resource management

Background:

• Regional groundwater levels in Perth have declined since the 1970s due to reduced rainfall and increased extraction.
• This decline has led to a loss of environmental and social values in wetland ecosystems.
• Wetlands are crucial where the watertable intersects the land surface, supporting biodiversity and community well-being.

Purpose of the Study:

• To examine a proposed scheme for restoring wetlands by augmenting infiltration galleries with treated wastewater.
• To assess the potential of treated wastewater to raise groundwater levels and improve wetland health.
• To evaluate the economic benefits of wetland restoration for nearby land values.

Main Methods:

• Modelling was used to predict the impact of adding treated wastewater on groundwater levels.
• Treated wastewater was trialed in infiltration galleries to assess contaminant removal.
• Economic analysis was conducted to estimate the impact of wetlands on land prices.

Main Results:

• Modelling suggests the scheme would raise groundwater levels, benefiting lake levels and local water supplies.
• Treated wastewater showed significant reduction in phosphorus, pathogens, and organic carbon within 5-50m.
• Nitrogen levels in the treated wastewater were comparable to existing lake and aquifer levels.

Conclusions:

• The proposed scheme offers a viable solution for wetland restoration in Perth.
• Treated wastewater can be effectively managed to improve groundwater and wetland conditions.
• This approach could serve as a model for using treated wastewater to combat saltwater intrusion in coastal areas.