UV disinfection system protecting state water supply

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The largest ultraviolet (UV) drinking water disinfection system in the southern hemisphere has shown great promise, protecting the drinking water supply of nearly half a million South Australians.

Commissioned in December 2021, the Xylem-manufactured system was upgraded at SA Water’s Happy Valley water treatment plant as part of a $26 million upgrade to ensure continued compliance of the utility to Australia’s global drinking water standards, while allowing the community access to open green spaces

Four reactors, with 624 UV lamps combined, allow the system to instantly treat up to 600ml of water per day – designed with additional treatment capacity to maintain network flexibility and support changes in demand.

Senior Director of SA Water, 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 in Happy Valley is another line of defense protecting the quality and safety of our largest drinking water supply in metropolitan Adelaide, while enabling kayaking and fishing in the adjacent reservoir” , Mr. Seltsikas said.

“Pathogens come in a variety of forms and can be found naturally in water sources. The watershed that feeds Happy Valley Reservoir, via Mount Bold Reservoir, is large and covers the Mount Lofty Ranges.

“From a water quality perspective, this particular watershed is challenging given the presence of agriculture, so there is an ever-present risk of pathogens, such as cryptosporidium, entering our reservoirs. ”

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

“Chlorine water disinfection occurs after filtration, to destroy any microorganisms that may not have been captured, but cryptosporidium can be chlorine resistant and evade treatment,” Ms. Seltsikas.

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

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

Mr. Seltsikas said that these lights are powered by state-of-the-art, energy-efficient technology.

“The lamps are powered by the latest electronic ballast technology – regulating lamp power from 50 to 100% – and exploit a sophisticated UV intensity sensor which significantly reduces energy consumption,” Seltsikas said.

“These two features make it one of the most energy efficient UV systems, and when combined with our solar panel in Happy Valley, capable of producing over 17,000 megawatt hours of energy per year to help power the ‘larger plant, ensures that we meet the energy needs of the system and its sustainable operation.

Over 200 people worked on the project through SA Water and its construction partner, joint venture John Holland Guidera O’Connor, with 60 full-time staff working on the site at the peak of construction.

Mr Seltsikas said the team’s agility and innovation were at the forefront amid global shipping delays last year.

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

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

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

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

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