PhD - Magnetic vivianite recovery from sewage sludge

PhD - Magnetic vivianite recovery from sewage sludge

Netherlands 17 Jun 2021


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State University
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17 Jun 2021
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Research by Wetsus in cooperation with TU Delft has shown that magnetic recovery of vivianite (ferrousphosphate) from sewage sludge is a promising new approach to recover phosphate and iron. This so-called ViviMag approach has been successfully piloted using commercial wet magnetic separators and provides new perspectives for phosphorus recovery from wastewater treatment plant that rely on dosage of iron salts to remove phosphate from sewage water. A better understanding of the conditions that influence the formation of vivianite and its separation from sewage sludge will help to further improve this technology. We will also study upgrading of the vivianite into novel products.

Research Challenge

Vivianite is a ferrousphosphate that can only form in conditions with low redox potential. It typically forms during digestion of surplus sludge from sewage treatment plants that dose iron coagulants for phosphorus removal. However already considerable amounts of vivianite are also present before sludge digestion. This is possible because formation of vivianite is quick under anaerobic conditions and the formed vivianite is resistant to oxidation during aerobic conditions. The formation of vivianite is the result of a complex interaction between different components in the sludge matrix like sulphides, organic matter and conditions like redox potential. The objective of this PhD is to study how the properties of vivianite and its formation history influence the recoverability from sewage sludge via magnetic extraction. Furthermore, we intend to study different ways to find uses for the vivianite. Ideally the iron can be reused in a circular way to bind of phosphate in the sewage treatment plant and the phosphate can be used in high value applications. You will use advanced analytical techniques like Mossbauer spectroscopy to study the interactions between phosphate and iron and to characterize different iron minerals.


We are looking for a candidate with an MSc degree in the field of chemical engineering with an interest in biochemistry or a related field of study (for instance mineral processing). We require you to use a thorough and critical understanding of the (bio)chemistry and physical processes to propose practical approaches to the problem. Your social skills and curiosity make it possible for you to benefit from the multi-disciplinary environment to find creative, new approaches to the research challenge. You are able to work independently.


The research project will be part of the Wetsus research theme “Phosphate Recovery”. The following companies are part of the theme: Waterschap Brabantse Delta, Waterschapsbedrijf Limburg, Kemira, Aquacare, Aquaminerals and VandCenter Syd.

The PhD student will be based at Wetsus in Leeuwarden and co-supervised by TU Delft.

Promotor: Prof. Mark van Loosdrecht (Technical University Delft)

Wetsus supervisor: Dr. Leon Korving

For more information contact


Wetsus, Leeuwarden, The Netherlands

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