11.2 Vivianite formation and recovery from sewage sludge

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 and may provide operators with guidelines to better operate their sewage treatment plants.

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 probably 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 these interactions, the influence of microbiology, the resulting vivianite forms and their effect on the recoverability in order to optimize phosphate recovery from sewage sludge via vivianite. You will use advanced analytical techniques like Mossbauer spectroscopy to study the interaction between phosphate and iron.

We are looking for a candidate with an MSc degree in the field of biotechnology with an interest in inorganic chemistry, or a related field of study. We require you to use a thorough and critical understanding of the (bio)chemistry 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, VandCenter Syd

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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