Recharged aquifers show how to create valuable water bank for community and industry use.
At the centre of the driest inhabited continent on earth, the city of Alice Springs continues to exhibit the Australian pioneering spirit with an astounding example of water conservation and re-use. This isolated Outback city of 25,000, located nearly 1000km from the nearest coastline, receives just 270mm of rainfall a year, or a fraction of that falling on coastal State and Territory capitals*.
So when the new $10.4 million Alice Springs Water Re-Use Project officially began operating this year, it was of considerable interest to conservationists, horticulturalists, farmers, industrialists, miners and urban planners alike.
“The project is outstanding in its own right socially, architecturally and technically. It will reveal valuable lessons for all big users of water,” says Steve Van Smaalen, Project Manager for technology provider Eimco Water Technologies-AJM Environmental Services (EWT-AJM).
“Increasingly, the future of major municipal, farm, factory and mine projects are bound up with community concerns to achieve the highest standards of water conservation and re-use and the best and most cost-efficient purification standards when recycling.”
The project – undertaken by the NT Power and Water Corporation with input from the CSIRO – will stop dry weather overflows from the Alice Springs wastewater stabilisation ponds into the Ilparpa swamp. Rather than letting precious water go to waste, the effluent will be recycled so it can be reused. Initially the project will recycle 600 megalitres of water a year — equivalent to 1200 average backyard swimming pools – and pump it more than 6km down to the region’s Arid Zone Research Institute. There it will be stored underground in aquifers before being used to irrigate horticulture projects, helping create employment and economic opportunities for the region.
AJM was awarded a contract by the Power and Water Corporation (PWC) to design, supply, install and commission a 6ML/D water reclamation plant in Alice Springs, NT. AJM supplied an ENVIRODAF 45000, a TOM1200 SUREBLEND polymer system, chemical dosing systems, pumps and reticulated services. This technology is widely used in municipal and industrial projects.
The AJM EnviroDAF system is designed with a unique Counter Current Dissolved Air Flotation (DAF) system to help overcome some of the problems encountered with traditional older-style Dissolved Air Flotation (DAF) systems. This counter current system eliminates the common problem of sludge carryover under high or irregular loadings, without the need for operator intervention.
AJM SureBlend is a fully automatic polymer blending and make-up system that has been designed for heavy-duty industrial applications. SureBlend is also designed to operate trouble-free without any need for regular operator attendance. SureBlend’s automatic operation does away with messy installations and continual cleaning and hosing associated with manual systems.
Alice Springs Process
The algae rich raw water is fed into the plant from existing waste stabilisation ponds. Neutralisation, coagulation, polymerisation and aeration results in flocculation below. Sludge is then removed at a rate of 2-5 m3/h. Sludge is then removed at a rate of 2-5 m3/h. Clarified water at a rate of 3-6ML/D is produced, followed by chlorination.
“The results achieved by the project were important for two main reasons,” says Mr van Smaalen.
“Firstly, it was important to eliminate local swamp land contamination from overflows of the existing evaporation lagoons. But equally important is the creation of quality non-potable water for water banking, or aquifer recharge.
“The main purpose of aquifer recharge is to store excess water for later use, while improving water quality by recharging the aquifer with high quality water. If groundwater is too salty for use, then the addition of a fresher, recycled water supply will displace the saltier groundwater.
“The method increases water storage in the aquifer, to make more water available for irrigation and other uses and also to preserve water levels in wetlands that are maintained by groundwater.
“Groundwater recharge may also be used to mitigate or control saltwater intrusion into coastal aquifers.
“The water withdrawn from the aquifer can be used to irrigate green open spaces, for example parks, ovals and golf courses, which generally use large quantities of water.
“It can also be used for other community, farming and industry uses, freeing up valuable supplies of potable water.
“These and other possible uses of the water will depend on public acceptance of such schemes, but it has to be a direction in which the community is heading,” he says.
Since the initial start up of the plant in Dec 2007, the process has operated trouble-free with excellent results.
The NT Minister for Essential Service, Kon Vatskalis, says the project represents the first major recycled water program undertaken in Alice Springs.
“This project will reduce discharges from the Alice Springs wastewater stabilisation ponds into Ilparpa swamp, ensuring better conditions for surrounding residents with fewer weeds and mosquitoes in the area,” said Mr Vatskalis, whose Government initiated the project in 2003 to discharge effluent in an environmentally friendly way.
“In a time when Australia is becoming increasingly environmentally conscious, this is a safe and logical practice to ensure a reliable supply of recycled water for the development of horticultural and other non-potable uses.”
Steve van Smaalen says it is striking that a small city in the middle of Australia’s desert country has not had to implement water restrictions at a time when they are commonplace in wetter regions.
“While some of the country’s bigger coatal centres have embarked on sophisticated larger desalination projects to address their water issues, this small community has drawn on its independent pioneering spirit to develop its own solution in tune with local resources and local needs.”
(* including Adelaide 500mm, Hobart 520, Canberra 630, Melbourne 660, Perth 790, Brisbane 1180, Sydney 1220 and Darwin 1690)
For further information, please contact Steve van Smaleen, AJM-EWT, at steve.vansmaleen@glv.com or visit www.glv.com