With support from the Ontario Water Consortium’s Water Industry Growth Program, Aquicon Water is demonstrating how their de Hoxar Spiral separator saves dollars, as well as space.
Across Canada, population growth and urbanization are putting pressure on municipal wastewater treatment plants. And that leaves many cities that have maxed out their available land in a tight spot.
Aquicon Water has a solution.
At various stages in the activated sludge process, conventional treatment plants use large tanks to settle solids to the bottom using gravity. Aquicon Water’s de Hoxar Spiral Separator can achieve the same results using just a fraction of the space.
“Picture a massive screw slowly turning inside a cylinder,” says Clyde Fernandes, the company’s business manager. “Like conventional treatment, it uses gravity to settle the solids from the incoming flows. But there are two key differences; one is that the angled plates within the cylindrical tank create more surface area. As a result, the solids settle out faster and form a thicker sludge. Secondly, because that surface area is stacked vertically, its footprint is radically smaller. That’s the magic,” explains Fernandes. “When treating primary flows, the spiral tank can take the same flows as a conventional tank in under five per cent of the footprint. In a secondary settlement application, you can get similar results to a conventional tank in just 12.5% of the footprint.”
Proving spiral technology to North Americans
The patented technology has been used for more than a quarter century in the U.K., where it was first developed by Plantwork Systems’ David de Hoxar. When Brampton-based Aquicon saw it in action, they recognized it could benefit municipal clients in the region and beyond. So, in 2021, they established a subsidiary — Aquicon Water — to bring the spiral separator to North America.
Treatment plant operators listened eagerly to the progress made at UK treatment sites. But the conversation always ended with potential customers telling Fernandes the same thing, “I love what you’re saying, but I need to see it.” To successfully market the spiral separator here, Aquicon Water needed a demonstration unit on this side of the Atlantic to prove how well it could perform.
According to Fernandes, that’s where OWC’s Water Industry Growth (WIG) program was crucial. WIG is designed to support the development and adoption of innovative water technologies. In the case of Aquicon Water, that meant providing funding to design and fabricate a scaled-down 1.5-metre-diameter demonstration model.
OWC also connected the company to the Pottersburg Pollution Control Plant in London, Ontario and helped fund the pilot project there. “The Consortium has been really vital,” says Fernandes. “Not only with their support for our project, but also in the intangibles, which has been the connections to the City and guiding us throughout this process.”
The scaled-down system allows Aquicon Water to test how well the spiral separator handles different types of wastewater duties including primary and secondary settlement, and potentially sludge thickening. They installed the unit late in 2022 and expect to wrap up trials in early spring 2024, proving that the separator can work through more than a full year of Canadian weather.
Testing on primary effluent is now underway, while testing on secondary effluent is slated to begin in the coming months. Based on U.K. results, Fernandes anticipates the system will remove 50–60 per cent of suspended solids and 25–30 per cent of biochemical oxygen demand during the primary trial while achieving a higher sludge density than the City’s existing tanks.
Trialing the potential for delivering thicker sludge
The Pottersburg trials also offer the opportunity to test a new application: thickening the solids that separate out during primary and secondary settling.
In conventional wastewater treatment plants, this sludge is typically 1 to 1.5 per cent solid. Most plants then take steps to remove some of the water content. Thicker sludge cuts transportation costs if the sludge is trucked off site, and it also makes subsequent treatment or disposal more efficient. However, it’s also expensive, requiring the addition of polymers and the use of energy-intensive equipment like gravity belt thickeners or rotating drum thickeners.
Through the Pottersburg trials, Aquicon Water aims to demonstrate that their spiral system can match — or even surpass — the amount of water extracted by current technologies without using polymers.
The challenge is that sludge quality varies from site to site based on how the plant is being managed. In the case of Pottersburg PCP, they’ve occasionally encountered filamentous sludge, where an overgrowth of certain bacteria causes sludge to become very light. At other times, a lack of oxygen encouraged the growth of different microorganisms that also impede settling by gravity.
Back in the U.K., Plantworks Systems is tweaking the technology, using the Pottersburg data to address these issues. If they succeed, the payoff could be big.
Saving dollars, as well as space
First, the compact footprint of the spiral separators allows for the expansion of plant capacity without the need for extensive infrastructure modifications or replacement plants. This flexibility in capacity management can support population growth and urban development without requiring costly upgrades. Additionally, for plants like Pottersburg that haul sludge off-site for treatment, thicker sludge also means fewer truckloads – and thus lower fuel costs and fewer greenhouse gas emissions.
At the end of trial, Aquicon Water will have a spiral separator fully optimized for Canadian conditions, as well as a case study demonstrating its performance to interested municipalities and consultants. “Ultimately, we’re trying to show that there’s a better way to do gravity settlement,” says Fernandes. “The potential is immense.”
WIG supports industry innovations that accelerate growth, create jobs and strengthen Ontario’s water sector. For more information, click here.