Around 100 years ago, Brisbane’s Municipal Council began removing human waste through an underground network of sewers. It was a revolution for public health and a big mark of progress for modern society. As awareness for environmental stewardship grew, local authorities moved onto both removing and treating that waste. Now, modern utility companies have embarked on a new frontier, not only removing and treating human waste, but turning that waste into a useful product. In effect – they’re taking the waste out of wastewater.
Queensland Urban Utilities (QUU) is embracing this innovative new approach; from the latest cogeneration machines – supercharged by beverage by-product – to floating wetlands and solar panels.
Utility spoke to QUU Executive Leader of Planning, Paul Belz, about how its sewage treatment plants are becoming more like resource recovery centres, harnessing the power of poo.
Supercharging cogeneration
“Cogeneration is an exciting technology, that’s why we’ve just installed three new state-of-the-art units at our two biggest sewage treatment plants – Luggage Point and Oxley Creek,” Mr Belz said.
“They work by capturing the biogas produced from sewage sludge to drive an engine and generate electricity. We’re producing enough energy to provide up to 40 per cent of the plants’ electricity needs, which is the equivalent of powering 1,250 homes each year.
“It’s a win-win for the environment and the business, as we’re not only reducing our carbon footprint but keeping operating costs down. In fact, we’ve estimated we’ll save up to $1.45million a year.”
These cogeneration units are getting an extra supercharge, with QUU experimenting with by-products from soft drink, juice, honey and even alcohol.
“We recognise the potential for this high-sugar waste to be used productively in our treatment process,” Mr Belz said.
“By pumping the sugary by-product straight into the digesters we increase the amount of biogas produced, which in turn bumps up energy yields from the cogeneration units even further.
“After a successful trial, we’re planning to take in more than 100,000 litres of beverage waste every week from our commercial customers. It’s a successful partnership – they’re happy to have a low cost, environmentally friendly alternative for their trade waste, and we’re happy to give our cogeneration units an effective sugar hit!”
Floating wetlands
Another way QUU is reducing its reliance on the electricity grid is by making the sewage treatment process less energy intensive. A new trial has been launched at a small treatment plant at Forest Hill in the Lockyer Valley, where floating wetlands are being used to purify the wastewater. The Queensland-first project involves growing wetlands on specially engineered plastic mattresses, which are then floated on purpose-built lagoons.
“It’s a natural, cost-effective and energy efficient solution to purifying wastewater,” Mr Belz said.
“The roots of the plants dangle beneath the mattress drawing out unwanted nutrients such as carbon, nitrogen and phosphorus.
“The floating wetland is like nature’s kidney, cleansing the water by trapping sediment and removing toxins. It’s a great example of green engineering and also has the potential to reduce operational costs at the plant.”
Solar panels
It’s not only the treatment process or the wastewater itself which offers utility companies an opportunity to operate smarter. The physical land on which sewage treatment plants lie offers another area of potential to unlock a value stream, while adopting more sustainable sewage treatment practices.
“Harnessing the power of poo is one thing, but in Queensland it makes sense to also harness our abundance of sunshine,” Mr Belz said. “We’ve done this by installing more than 500 solar panels at the Laidley, Gatton, Forest Hill, Kalbar, Boonah, Kooralbyn, Beaudesert and Kilcoy sewage treatment plants, cutting power use at the facilities by more than 20 per cent.
“The solar systems will deliver operational savings of around $45,000 a year and reduce the annual carbon dioxide emissions to the equivalent of taking 57 cars of the road for a year.”
The initiatives are part of QUU’s Renewable Energy Plan which aims to make its sewage treatment plants cleaner and greener.
“QUU is always exploring innovative ways to become more sustainable, both environmentally and economically,” Mr Belz said.
“In fact, as the population increases, our reliance on the electricity grid is decreasing. Despite this great outcome, we recognise there is more work to be done on the journey of turning waste streams into value streams and fulfill our vision to be a utility of the future.”
