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How TRILITY managed the SA blackwater event within the River Murray

With flooding becoming more prevalent in many Australian states, treatment plants are being pushed to their limits to innovate with established processes and solve blackwater issues.

Blackwater issues are water quality problems associated with flood waters.

The 2016 South Australian blackwater event is a case in point, one which was preceded by two other major blackwater events in 2010 and 2012.

Presenting at the upcoming Ozwater’18 on TRILITY’s approach to managing the 2016/17 South Australian blackwater event within the River Murray, TRILITY Operations Manager Adam Medlock (Australian Water Association SA 2017 Young Water Professional of the Year) said the treatment plants were initially designed for the very worst of water conditions on record at the time of their construction.

However, with climate change, these conditions have since worsened and therefore, demand a different approach to deal with occasions such as a blackwater event.

“This blackwater event was supposedly a one in 100-year event. Yet, we had three of them come through, so they can’t be considered to be once-off events anymore. This sort of thing is going to happen,” Medlock said.

“During the first blackwater event in 2010, we’d previously had 14 years of drought conditions and the water quality conditions were very stable and consistent. The plants were set up to manage that. But when you get a blackwater event, some of the key process and treatment variables flip on their head. The treatment plant hadn’t been designed to deal with it.”

Aside from design limitations being exceeded, the utility also had tightened water quality guidelines to contend with, which demanded more of the treatment process.

“It’s like you’ve been driving in your car at 60km/h and suddenly you want to go 200km/h. It is something that you can do, but it needs to be properly planned out and approached systematically. You can’t just turn a dial on the plant and expect it to treat whatever comes in,” Medlock said.

“We had tightening guidelines and Department of Health requirements. These were much tighter by the time the blackwater event hit than what they were when the plants were first built. We were exceeding the design limitations.

“If we were to design a plant now, it would be completely different. We would design it to a tighter spec around what we are expected to achieve now.”

Medlock said during the 2016 event, operations had to also come up with an approach that utilised available processes to mediate the level of organics in the water.

“The plant was not designed to get rid of the level of organics coming down the river during the blackwater event, aside from the fact that it affects other processes like the UV disinfection, which is a big health risk,” he said.

“We decided to look at the key processes we were trying to manage, the key areas we needed to keep in control and how we would do that. We did a number of tests and our optimum aluminium sulfate dose was far higher than what our pumps could put out.”

Medlock said it decided on an approach that utilised activated carbon to mediate the level of organics in the water, lowering them to a manageable treatment level.

“To get the required alum dose down, we decided to use activated carbon, which we don't normally use for organic removal. But we decided to use it to reduce the organics in place of adding more alum and it worked,” he said.

“The approach we made for these events could, on paper, be considered a process risk, but at the same time it was backed up by solid theory. We don't want to take risks because we think it might work; we want to take risks because the calculations say that it has a very good chance of working.”

Medlock said while instances of treatment process innovation are on the rise due to increasing demands on systems, it’s nothing the expertise of Australia’s water industry can’t manage, which is what makes the job so compelling.

“When you are talking about potable water for the public, you can’t call the water authority and say, ‘sorry, we don’t know what to do because its not in the manual’,” he said.

“We have the expertise and whilst we might not need to use it all the time, we shouldn’t hesitate to apply our skill set when the time comes.”

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