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Algae bioreactors create cost-cutting benefits for wastewater treatment process

Queensland Urban Utilities, in partnership with global technology provision company KBR, have completed the early stages of an algae bioreactor pilot to test the process for possible wastewater treatment cost cutting.

Presenting on the pilot at the upcoming QWater Conference, KBR Principal Process Engineer Garry Henderson said the results of the pilot are promising, with the benefits of the process making the algae bioreactors a financially competitive solution to wastewater nutrient removal.

“The floating concept provides more flexibility in how you use the reactor. The main intent of the bioreactor is to pick up nutrients, predominantly nitrogen, and also to provide dissolved oxygen to the process,” he said.

“Using algae is one of the most energy-efficient ways of producing dissolved oxygen. Algae biomass can produce supersaturated oxygen to the water, which can then be directed to an appropriate part of the process to maximise the overall process train.”

Henderson said the high concentration of oxygen production makes the overall treatment system more productive, and therefore more cost-effective.

“The fact that it produces a very high concentration of oxygen that can then be directed to other parts of the system makes the effectiveness of the overall system cheaper in terms of operating cost compared to mechanical aeration,” he said.

Aside from oxygen production, the floating algae bioreactors provide more nutrient removal without the expenditure associated with expanding pond systems.

“Compared to the alternative options, like putting in activated sludge processes to produce the nutrient removal or expanding a pond system with civil works, the cost is much lower. Algae bioreactors are quite shallow and relatively inexpensive to produce,” Henderson said.

“One of the other advantages of using a floating algae bioreactor is that you can leave the operation on a pond system, which have a high residence time. You can put the flow you want to treat through the floating unit during daylight hours. They can also be powered using solar power.”

And although initial piloting has produced promising results, Henderson said there is still more testing to be done before moving the technology to demonstration stage.

“It’s looking very promising and Queensland Urban Utilities are quite excited about the prospects, but we still have a bit more work to do at the pilot stage before we contemplate moving to demonstration,” he said.