Award-winning publication outlines circular future for aquafer

The background to the paper was the fact that aquafer (iron sludge) is almost always formed during drinking water treatment. With circularity in mind, a range of parties began to wonder whether the iron from this process could be re-used as a flocculant in water treatment. This question resulted in the successful HerCauWer TKI project, with KWR, the Brabantse Delta water authority, Feralco and Aquaminerals as partners. The paper ‘Reuse of aquafer from drinking water treatment for phosphate removal’ (Hergebruik van waterijzer uit drinkwaterzuivering voor fosfaatverwijdering) on this project was published in the journal H2O, winning the 2022 H2O award.

Cherry on the cake

‘This was a nice cherry on the cake of almost 35 years of working in the world of water,’ says co-author Wolter Siegers. ‘The great thing about professional papers of this kind is that they focus on practical issues. I think the impact delivers added value by comparison with scientific publications in English.’ This publication won’t be the last we hear from Siegers. ‘For example, we are currently working on pilot research into the removal of organic micropollutants from effluent. As soon as there is anything to report, we will be sure to publish in H2O.’

Re-using aquafer as a coagulant

The research described in the award-winning paper will certainly have a positive impact in the literature. Siegers explains: ‘Dutch drinking water companies produce some 90,000 tonnes of aquafer annually. We looked at which aquafer is most suitable for dissolving the iron again by adding an acid. It can then be used a coagulant. Because of the strict requirements, an experimentally reused flocculant of this kind can’t be used for drinking water production, but it can be used to treat waste water. Almost every WWTP doses iron coagulant to remove phosphorus. Now we know that iron sludge has excellent properties in terms of re-using it for this purpose, opportunities are opening up.’

Cheaper and effective alternative

For the water sector, the results of the study mean there is a feasible alternative for the usual commercial coagulant. It works just as well and, on top of that, the circular product costs less. On the basis of the study we conducted, it looks like there is a good chance of marketing the ferrous flocculant made from aquafer from the drinking water companies as a flocculant for wastewater treatment. The response from the water sector has been positive, Siegers knows. ‘A number of companies, including Aquaminerals and Feralco, are keen to continue developing this product. The Brabantse Delta water authority is also enthusiastic. The next step is to determine where the circular coagulant should be produced. KWR is happy to play a role in this follow-up process in order to contribute to a more circular economy and reduce environmental impact.’

Wolter Siegers (2nd from left) and Roberta Hofman of KWR accept their H2O Award.