Struvite, a so-called phosphate mineral, can be reclaimed from sludge from a sewage treatment plant. Phosphate is an important nutrient for crops. Phosphate mines are the primary source of this mineral, but this supply is finite. Alternative sources are therefore being investigated, for example recovering phosphate in the form of struvite from sewage sludge, which always contains a great deal of phosphate. The extraction of struvite also lowers maintenance costs in the sewage treatment plant, as it reduces the formation of crystals in the installation.
Because of the possible presence of pathogens, antibiotic resistant microorganisms and contamination such as pharmaceutical residues in the sludge, it cannot be stated in advance that the recovered struviet is clean and safe. According to RIVM, there are no indications that the utilization of struvite would lead to increased risks for public health or the environment. However, this conclusion is based on very few measurements. It is recommended to perform additional measurements.
Under present legal guidelines, struvite from waste water is labelled as 'waste'. This classification as waste makes it difficult for sewage treatment plant managers to utilise struvite as a raw material for introducing new products to the market. Water management authorities would therefore like the 'waste label' attached to this material to be removed. This would increase the value of products made from struvite, and parties other than waste processors would then be able to purchase the products. It would also make it easier to export the product. However, to remove the waste label, this struvite has to comply with certain safety criteria.
This study was carried out in close collaboration with the stakeholders (water management authorities, Rijkswaterstaat, and the Ministry of Infrastructure and Water Management). This resulted in increased mutual understanding for the interests of all sides and made it easier to make choices that can receive the support of all the parties concerned, in this case a choice for further research and corresponding research method.