The hunt for a potent solution for micropollutants

In a project with BIOFOS, Denmark’s largest water utility, Aquaporin demonstrates that forward osmosis can improve micropollutant removal from municipal wastewater while also opening up additional revenue opportunities for utilities.

Most municipal wastewater treatment plants simply don’t have the technology installed to remove all microplastics or micropollutants from wastewater. Even in Denmark – one of the most advanced countries in the world when it comes to water treatment – micropollutants and microplastics are released directly into the sea.

Removing micropollutants is possible, but it requires a significant amount of energy – and the issue will only increase as urban populations grow. The BONUS Cleanwater project brought together some of the most promising water-cleaning technologies to find a sustainable and cost-effective solution.

Meeting increasingly strict regulations

The EU’s water frame directive includes regulations on the release of micropollutants into receiving waters. The goal of the BONUS Cleanwater project was to assess water treatment solutions in order ensure future decision-makers are better informed about what’s possible, realistic and affordable.

The project brought together partners from across the Baltic Region, and pilot plants where set up in Denmark and Sweden. Hosting the project was BIOFOS, the largest wastewater treatment utility in Denmark, with three wastewater treatment plants and a total capacity of 1,400,000 PE.

“Today, BIOFOS is well within the EU’s water frame regulations. But we expect those regulations to tighten in the future. When that happens, we want to be ready,” says Dines Thornberg, Head of BIOFOS’ R&D department. “Our aim is to create a fully green water treatment cycle that removes all pollutants, is energy positive and re-uses valuable minerals – such as phosphorus. The project gave us a chance to build knowledge in the area of micropollutant removal and assess the best options in terms of water quality, energy consumption and sustainability.”

Exceptionally high rejection rates

As part of the project, the Aquaporin team set up a pilot-scale forward osmosis (FO) treatment plant, using membrane bioreactor (MBR) effluent as the feed stream and seawater as a draw solution. The results were impressive.

At constant operation, we achieved a 65% recovery rate and rejected a minimum of 95% of micropollutants. Performance was so good, in fact, that the recovered water was of a significantly higher quality than required for discharge into receiving waters. This opens up other possibilities for water reuse, as Dines explains.

“In terms of removing micropollutants, we saw the best results with Aquaporin. In fact, the quality was higher than we need here in Denmark,” he says. “The solution has great potential in countries where water scarcity is an issue. In these countries, I could imagine a scenario where the wastewater is upgraded and used for drinking water or sold to industry, for example as energy plant cooling water.”

Partnering with other technologies

Often, FO systems are combined with reverse osmosis (RO) systems to recover the draw solution. In this case, RO is not required because seawater is freely available and plentiful onsite. However, a hybrid solution is still required as the concentrated reject slurry needs to be treated.

“In most water treatment scenarios, there is no single silver bullet,” says Sylvie Braekevelt, who led the project from the Aquaporin side. “The future lies in hybrid solutions that combine different technologies to fulfill the water treatment needs. Often, the technologies enhance each other. In this case, for example, specialists expect higher micropollutant removal rates when treating the FO reject slurry biologically than when biologically treating wastewater directly.”

Proud to be part of a solution

We all know micropollutants and microplastics are a huge issue for our oceans. The BONUS Cleanwater project shows there is a way to remove micropollutants and microplastics from municipal wastewater that is both effective and affordable – and we’re proud to have been part of it.

If you’d like to know more about the project and results, please contact us here.

About Bonus Cleanwater

BONUS Cleanwater was funded by BONUS, the joint Baltic Sea research and development program for 2010-2017. Supported by the Baltic states and EU, BONUS initiates and funds ecosystem research to produce knowledge and solutions needed by policymakers and to engage end-users and society in the governance and protection of the Baltic Sea. Read more about BONUS here.

Published on May 20 in ,