A tale of two systems: water supply on KI

Although separate, Kangaroo Island’s two distinct water supply networks actually have much in common, with each using innovative techniques to treat raw water and produce the reliable supply of clean, safe drinking water for the Island’s residents.

As KI residents are invited to have their say on the supply options identified for SA Water’s refreshed long-term plan for water supply, the essential service has provided a look behind the scenes at the technology employed at its Middle River and Penneshaw operations to show how water is currently sourced and treated.

The larger of the two systems is Middle River, which supplies an average of 356 million litres of water across 1500 customer connections, through a network of more than 100 kilometres of water mains.

Middle River Reservoir has the capacity to store approximately 549 million litres of water, typically filling with early winter rains and spilling excess water until October or November each year.

SA Water’s Kangaroo Island long-term plan lead Erin Faehrmann said it takes around 90 minutes to turn raw water from Middle River Reservoir into the clean, safe drinking water that flows from taps from Parndana to Kingscote.

"Raw water from the reservoir contains high levels of dissolved organic carbon which comes from vegetation in the catchment area and causes its natural tea-like colour. There is also suspended dirt, organic material and microorganisms, so it goes through a number of processes to clean and treat it," Erin said.

A world-first process developed by SA Water, Orica Watercare and the CSIRO Division of Molecular Science, called Magnetic Ion Exchange (MIEX), passes a recyclable magnetic resin through the water to attract and remove the dissolved organic carbon, before further conventional treatment processes.

"Remaining impurities are clumped together, to settle and separate sediment before filters cleanse the water of any remaining fine particles. The final step is disinfection, where chlorine and ultraviolet light kill any pathogens."

Approximately 300 customers on the eastern end of the island receive their water from the Penneshaw Desalination Plant, which was originally built in 1999 and upgraded last year.

"Penneshaw is capable of producing up to120 million litres a year, and readily meets the area’s current average annual demand of 69 million litres.

"It takes Penneshaw around two hours to turn sea water into fresh water for drinking, before it’s distributed through around 15 kilometres of pipes."

Seawater drawn into the plant is filtered to remove fine particles. The filtered seawater is then forced under high pressure through reverse osmosis membranes that allow fresh water to pass through, with saline water channelled away. The desalinated water is re-mineralised with carbon dioxide and exposure to marble chips, to reduce its corrosive properties and improve taste, prior to final chlorine disinfection.

SA Water’s comprehensive water testing regime ensures quality is maintained throughout the production process and water provided to customers complies with the Australian Drinking Water Guidelines.

"Customers are at the heart of everything we do, and managing and monitoring the processes to deliver safe drinking water is a major focus of our work on Kangaroo Island and across the state," Erin said.

"Our expert employees collect and analyse more than 250,000 water samples each year from a variety of locations in South Australia, from catchment to tap."

Water samples are tested in the field and by scientists at SA Water’s world-leading laboratories in Adelaide.

Up-to-date water quality results are published at sawater.com.au where customers can find detailed information about what’s in their water by postcode or suburb.

The Middle River and Penneshaw facilities are among 43 water treatment facilities that SA Water operates around the state.

"The water treatment facilities and supply networks on KI have capacity to meet the current water needs of the population, but we also need to make sure they’re well positioned to enable population and economic growth over the long-term."

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