Treated stormwater will be used to irrigate the field, ensuring the community can enjoy a well-watered sports reserve. Image: Dmytro Larin/shutterstock.com
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Australia is a dry climate and dealing with water scarcity has always been part of the country’s history, making water sustainability a key priority for governments and councils across the country.

Projected population growth in Australia, coupled with the potential temperature increases that could be part of the nation’s climate future have made it more critical than ever to develop innovative ways to recycle water and further secure drinking water supply.

This has led to a recent uptick in projects and facilities that recycle and treat raw water, both for non-drinking purposes and to reduce the country’s use of drinking water for these applications.

A method of securing additional water supply that is emerging as a priority is stormwater harvesting, which involves the collection, treatment, storage and subsequent usage of stormwater runoff from urban areas. The key difference between stormwater harvesting and rainwater harvesting is that stormwater harvesting includes water runoff from driveways, carparks and roads, as opposed to the cleaner rainwater runoff from roofs only.

Once rainwater touches the ground, it becomes known as stormwater, which, if treated, can be collected and reused for several applications that would ordinarily use potable water. These include watering parks, golf courses and other irrigation of public recreation areas.

As well as potential contamination, the additional volume of water can lead to scouring and erosion in streams and creeks. Image: Tamara Iva/shutterstock.com

As well as potential contamination, the additional volume of water can lead to scouring and erosion in streams and creeks. Image: Tamara Iva/shutterstock.com

As well as limiting the usage of drinking water, stormwater harvesting can reduce the billions of litres of stormwater that enters Australia’s creeks, rivers and bays, as often this stormwater contains litter and other pollutants.

There are three main types of stormwater pollution and each comes with its own impacts on the environment:

  • Litter – food wrappers, cans, cigarette butts and plastic bags
  • Natural pollution – leaves, animal waste and garden clippings
  • Chemical pollution – oils, detergents and fertilisers

As well as potential contamination, the additional volume of water can lead to scouring and erosion in streams and creeks.

With Australia’s population growing, urban areas continue to expand, meaning an increase in hard, impenetrable surfaces – such as concrete, roads and roofs – and less water being soaked into the earth when it rains via natural, undeveloped surfaces like grass and dirt. Unmanaged stormwater runoff can cause flooding and can impact or damage properties, even potentially jeopardising the safety of the public in extreme cases.

As such, collecting this stormwater and developing systems for mitigating stormwater pollution, as well as reducing drinking water usage for non-drinking applications, is a key priority in Australia.

Securing water supply

In a bid to develop alternative water supplies and improve the health of waterways, the Victorian Government, Melbourne Water and councils across the state are working together to improve stormwater management.

The State Government has co-funded several stormwater harvesting projects in the Yarra Catchment through the Integrated Water Management (IWM) Forums. The IWM Forums identify, prioritise and supervise the execution of water opportunities across the state of Victoria.

A key priority project for the Yarra IWM Forum was the Monbulk stormwater harvesting project, which saw the installation of a new stormwater harvesting system at Monbulk Recreation Reserve.

As well as the Monbulk stormwater harvesting system, multiple similar projects have been identified for the Yarra IWM Forum Catchment, including the detailed design of the Curtain Square stormwater harvesting system, re-purposing old rubber tyres as permeable pavers to filter stormwater at Ramsden St Reserve in Clifton Hill and a Coburg stormwater harvesting system for irrigation of Coburg City Oval.

The Monbulk system

The Monbulk stormwater harvesting system was delivered by Melbourne Water, in partnership with Yarra Ranges Council and the State Government, in March 2024.

The Monbulk stormwater harvesting system captures, treats and uses stormwater collected from a council drain in McAlister Road, next to Monbulk Recreation Reserve, draining a 17ha catchment including Mt Pleasant Road, Moores Road, Main Road and David Hill Road in Monbulk.

It is expected to harvest approximately four million litres of stormwater every year and is anticipated to mitigate reliance on drinking water supplies and reduce stormwater pollution in Woori Yallock Creek, Emerald Creek, the Yarra River and Port Phillip Bay.

Stormwater harvested by the system is stored in underground tanks in close proximity to the field. Once treated, the water will be used to irrigate the field, contributing to waterway health and boosting potable water supply while ensuring the community can enjoy a well-watered sports reserve.

Understanding the process

Optimal Stormwater was contracted by Melbourne Water for the construction and installation of the Monbulk stormwater harvesting system.

The pumps and treatment specs of the equipment involved in the project are as follows:

  • Two Grundfos SE1.80.100.40.4.50B.B pumps
  • One Grundfos SE1.50.65.30.EX.2.50B.B
  • One Grundfos type irrigation pump – vertical multi-stage pump, capacity 5L/s at 70m
  • One Davey type irrigation pump – vertical multi-stage pump
  • Screen filter SAF3000, capacity 50μ
  • UV disinfection DUV-3A500-N-M MST

As a prerequisite to safeguarding the stormwater harvesting system further down the treatment line, pretreatment is conducted by the system installed by Optimal Stormwater. This pretreatment comprises of a high performing CDS technology (continuous deflection separation) gross pollutant trap and was developed in Mornington, Victoria.

Connected to the CDS is a pump-well that delivers stormwater to the underground storage located by the Monbulk oval. Facilitating this water delivery is two Grundfos pumps, each delivering 25L/s capacity.

The underground storage near Monbulk oval is a 300KL Invisible Structures tank that is manufactured from recycled plastic. The tank has access from both ends which allows for easier cleaning every two to five years. Another pump-well is also attached to the underground tank – this one housing one Grundfos 5L/s pump – and, upon request, pumps the stored water to the 100KL header tank next to the stormwater harvesting system (SWH) shed.

Common across all Optimal Stormwater’s SWH systems – and in accordance with Phase 2 of the Australian guidelines of water recycling – the harvested water will pass through a treatment train consisting of a filtration unit and a disinfection unit before being utilised for irrigation.

Natural pollution build-up around stormwater drain during heavy rainfall events. mage: Lost_in_the_Midwest/shutterstock.com

Natural pollution build-up around stormwater drain during heavy rainfall events. mage: Lost_in_the_Midwest/shutterstock.com

The whole system is completely automated and can be operated offsite and was designed, constructed and installed
by Optimal Stormwater. Throughout the construction and installation of the system, Optimal Stormwater strove to use the highest quality local and international componentry. Additionally, following the installation of the system, the company carried out all required checks.

For the ongoing managing of the system, Optimal Stormwater carried out an extensive training period, operating the SWH system alongside Yarra Ranges Council staff to adequately train them on operational matters in anticipation of the scheme being handed over to the Yarra Ranges Council.

Melbourne Water’s Incentives Coordinator for Waterways and Catchment Services North West, Micah Pendergast, said, “This is a great step forward for the Monbulk community. Making use of alternative water sources – like recycled water and stormwater – reduces pressure on our drinking water supplies while improving the liveability of our communities.

“Stormwater harvesting systems, like this one in Monbulk, reduce pressure on drinking water supplies while improving liveability for our communities.

“The Monbulk community benefits from an alternative local water source for the sports field that does not impact drinking water supplies and improves the health of Emerald Creek by reducing stormwater levels and using it more effectively.”

Featured image: Treated stormwater will be used to irrigate the field, ensuring the community can enjoy a well-watered sports reserve. Image: Dmytro Larin/shutterstock.com

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