Lighting up water treatment in Happy Valley

Operating for more than six months, Xylem’s ultraviolet disinfection system has kept pathogens at bay to protect the supply of safe, clean drinking water for nearly half a million South Australians.

Commissioned in December 2021, the 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 ultraviolet (UV) lamps enable the system to treat up to 600 ML 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,” 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 these risks, our Happy Valley Water Treatment Plant adopts 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.

“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 reactor has 13 independent rows of 12 UV lamps, which are automatically operated and are capable of turning themselves off based on the instantaneous treated flow and incoming water quality.

“The lamps are powered by the latest electronic ballast technology — regulating the lamps’ output from 50 to 100% — and harness a sophisticated UV intensity sensor that significantly reduces energy consumption.

“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 onsite at the height of construction.