Teacher background information
What is groundwater?
Groundwater is made up from rain which percolates down through the rocks and soils and into aquifers. Aquifers are composed of sand, sandstone and limestone. In Perth there are 3 layers of aquifers:
- Superficial aquifer: The shallowest aquifer which stretches across the coastal plain. Superficial aquifers are located close to the surface and often express themselves as wetlands or lakes.
- Semi-confined Leederville aquifer: Below the superficial aquifer, and is separated by confining layers which minimises water movement. The Leederville aquifer is often several hundred metres thick, and in some areas it connects with the surface.
- Confined Yarragadee aquifer: The oldest aquifer that provides a robust supply of groundwater even in dry years because of its vast storage and limited connection to the surface environment. It extends from Geraldton in the north to Albany in the south.
What is groundwater replenishment?
Groundwater replenishment is an innovative concept where treated wastewater is further treated to drinking water standards and recharged into groundwater supplies. The water is then stored and taken out some time later for further treatment and supply to a drinking water system.
Before wastewater reaches the Advanced Water Recycling Plant, it has already undergone rigorous treatment at the Beenyup Wastewater Treatment Plant to remove chemicals and micro-organisms such as bacteria, nutrients, detergents, oils, pesticides and heavy metals.
At the Advanced Water Recycling Plant it undergoes further treatment processes which include ultrafiltration, reverse osmosis and ultraviolet disinfection before it is recharged into the ground. This removes chemicals and micro-organisms to meet World Health Organisation standards and Australian guidelines for drinking water.
There are several water quality checkpoints (known as critical control points) throughout the treatment process to ensure each stage of the plant is working at optimum levels.
If water does not meet the required standard when it reaches a check point, it triggers an alert for action to be taken. For example, we may need to divert the recycled water back to the Beenyup Wastewater Treatment Plant or temporarily shut down the plant.
As WA continues to experience a drying climate and an increasing population, demands on our water supplies are greater than ever. Groundwater replenishment could help Perth by:
- reducing our dependence on rainfall as a source of water
- ensuring ‘climate resilience’ by recycling water on a large scale
- potentially providing up to 20% of Perth’s drinking water supplies by 2060 (if expanded to our other major wastewater treatment plants).
We have a 4 part video that will help your students better understand why groundwater replenishment is important to WA.