Aquifer Storage Transfer and Recovery Demonstration Plant, City of Salisbury, Australia

Converting stormwater into drinkable water

The Aquifer Storage Transfer and Recovery (ASTR) technique is a process for converting stormwater into water of drinkable quality.

The technique involves injecting stormwater that has been treated by being passed through a reed bed or wetland into an aquifer. The water is stored in darkened conditions for a prolonged period and becomes potable by natural processes.

Located in City of Salisbury, South Australia, the first trial phase of the ASTR demonstration plant was carried out between 2006 and 2009.

Purpose of ASTR

The main purpose of the project was to carry forward a successful demonstration of the ASTR technology.

Research was also carried out to investigate alternative water sources such as stormwater and treated wastewater to fulfil growing demand. The research successfully demonstrated the natural treatment application of stormwater after storage in an aquifer.

"The water, stored in darkened conditions, becomes potable by natural processes."

The demonstration project was carried out to check if stormwater stored in aquifers can be recovered to produce drinking water. It was also designed to find out whether the multiple barrier methods applied for water quality management are economical, robust, and transferable within Adelaide and worldwide.

Aquifer characterisation, groundwater, and geochemical modelling; risk-based management; monitoring of water quality; microbial pathogen attenuation; and water quality improvement performance assessments were carried out during the course of the project.

ASTR plant design

The ASTR project consists of a limestone tertiary aquifer (T2 aquifer), which is approximately 60m thick. The aquifer is divided into units T2a, T2b, and T2c.

Out of the total six wells that the ASTR system uses, two inner wells are for water recovery and the four outer wells are for injecting water. A distance of 50m is maintained between each injection well, and between injection and recovery wells. The depth of the well varies between 165m and 182m below ground.

Water treatment

Water for the ASTR project comes from Parafield Stormwater Recycling Scheme operated by the City of Salisbury. The catchment region covers an area of 1,600ha, whereas the water harvesting scheme is spread over an area of 11.2ha.

"ASTR consists of a limestone tertiary aquifer."

The stormwater is first harvested using a reed bed and then stored after injecting it in the tertiary T2 aquifer located in the Port Willunga Formation.

Water is stored at a depth between 160m and 180m below the ground. The low-moderate porous limestone aquifer is naturally brackish in character.

The ASTR process consists of six production wells drilled at a space of 50m, which form a tetragonal shape. The wetland-treated stormwater is injected into the aquifer using the four outer wells, whereas the inner two wells are used for taking out the stored water from the aquifer.

Recharge and recovery wells are maintained separately to allow the aquifer ample storage time and travel distance, which act as a natural biofilter. The extra water treatment achieved through this process grants better control of chemical and microbial contaminant attenuation of the stored water within the aquifer. A time gap of approximately 12-15 months is maintained between water injection and recovery.

Recovered water from the ASTR site meet most of the Australian Water Recycling Guidelines, although further water treatment was needed to remove iron contaminants.

ASTR supporters

The ASTR project is supported by the Australian Department of Innovation, Industry, Science, and Research (DIISR); the South Australian Premier’s Science and Research Foundation; and the Australian Government National Water Commission.

Water quality facts and system operation regarding the Parafield stormwater harvesting system was provided by the City of Salisbury.

"Water is stored at a depth of 160-180m below the ground."

United Water was responsible for water quality sampling, down-hole profiling, and financial support for laboratory analysis. The company also provided logistical support and project management services.

Laboratory analysis was carried out by SA Water through the Australian Water Quality Centre.

Early aquifer characterisation probes were executed by the geological technical unit of the Department of Water, Land, Biodiversity, and Conservation. Research services were rendered by the Commonwealth Scientific and Industrial Research Organisation (CSIRO).