The Southern Hemisphere’s largest ultraviolet (UV) drinking water disinfection system has shown significant promise, protecting the supply of clean drinking water for nearly half a million South Australians.  

Commissioned in December 2021, the Xylem-manufactured system was retrofitted to SA Water’s Happy Valley Water Treatment Plant as part of a $26 million upgrade to ensure the utility’s continued compliance with Australia’s world-leading drinking water standards, while enabling community access to green open spaces

Four reactors, with a combined 624 UV lamps, enable the system to treat up to 600ML of water each day instantaneously – designed with additional treatment capacity to maintain network flexibility and support demand changes.

SA Water’s Senior Manager of Capital Delivery, Peter Seltsikas, said secondary disinfection with ultraviolet light provides an additional layer of water quality protection against potentially harmful pathogens.

“Our new UV disinfection system at Happy Valley is another line of defence protecting the quality and safety of our largest drinking water supply to metropolitan Adelaide, while enabling kayaking and fishing at the adjoining reservoir,” Mr Seltsikas said.

“Pathogens come in a range of forms and can be found naturally in water sources. The catchment area that supplies Happy Valley Reservoir, via Mount Bold Reservoir, is significant and covers the Mount Lofty Ranges.

“From a water quality perspective, this particular catchment is challenging given the presence of agriculture, so there’s an ever-present risk of pathogens, such as cryptosporidium, finding their way into our reservoirs.” 

To manage this risk, the Happy Valley Water Treatment Plant uses a series of conventional treatment processes including coagulation, flocculation and filtration to trap and remove dissolved organic matter or other solid particles.

“Disinfection of the water with chlorine occurs after filtration, to destroy any microorganisms that may not have been captured, however cryptosporidium can be resistant to chlorine and evade treatment,” Mr Seltsikas said. 

“When pathogens like cryptosporidium and giardia are exposed to and absorb the high-powered ultraviolet light, it destroys their structures and inactivates the microorganisms’ cellular function.”

Each of the Plant’s reactors contains 13 rows of 12 UV lamps, which automatically  turn themselves on, or off, based on the instantaneous treated flow and incoming water quality.

Mr Seltsikas said these lamps are powered by cutting-edge and energy-efficient technology. 

“The lamps are powered by the latest electronic ballast technology – regulating the lamps’ output from 50 to 100 per cent – and harness a sophisticated UV intensity sensor that significantly reduces energy consumption,” Mr Seltsikas said. 

“These two features make it one of the most energy efficient UV systems, and when combined with our solar array at Happy Valley, capable of producing more than 17,000 megawatt hours of energy per year to help power the wider plant, ensures we’re meeting the system’s energy demands and operating it sustainably.”

More than 200 people worked on the project across SA Water and its construction partner, John Holland Guidera O’Connor joint venture, with 60 full-time employees working on site at the height of construction.

Mr Seltsikas said the team’s agility and innovation came to the fore amid global shipping delays last year.

“While the impact of last year’s Suez Canal incident sparked delays across the global supply chain, including with our UV system en route inside a shipping container, we initiated swift changes to our project design and condensed the construction schedule to maintain our delivery program,” Mr Seltsikas said.

“Our team reviewed the design of the inlet duct, which required a new weir to be cut into the existing wall, and the initial design included manual concrete demolition and a significant amount of structural steelwork.

“Harnessing creative thinking, we used a robotic cut saw to remove the concrete more efficiently and poured a large concrete beam, eliminating the need to install steel to structurally support the new weir.

“It was imperative we remained on schedule despite the delay in receiving the infrastructure, and these design variations removed six weeks of work from the program to ensure we could complete the project on budget and on time.”

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