Metals in the water cycle: insight and opportunities

Is it possible to recover (scarce) metals in an economically responsible manner from the watercycle – from drinking water production through to wastewater and sludge ash? That is the key question to be addressed in a new TKI Water Technology research project. The Limburg, Vallei en Veluwe, Rijn en IJssel, Delfland, Rijnland District, Schieland en de Krimpenerwaard, Hollandse Delta, and Rivierenland waterboards, together with Oasen, HVC, GMB, and coordinator KWR, will be working together in trying to answer this question.

Useful reuse of residuals

The focus of water treatment is increasingly shifting to the recovery of raw materials. Water companies, waterboards, sludge final-processors and waste-to-energy plants are searching for ways of recovering raw materials and of making new use of them. For the time being, in the wastewater and sludge cycle the investment is being directed mainly at the recovery of phosphorus. But there are more residuals that can be reused.

Removing metals improves the quality of other residuals

The consortium sees opportunities, for instance, for the recovery of (scarce) heavy metals and rare earth metals, including copper, zinc, gold and palladium. Moreover, removing these metals improves the quality of the water, sludge and residual ash, and thereby opens disposal possibilities for these residuals as well. In the project’s first phase, different waste streams will be sampled to provide a clearer picture of the quantities and form of the scarce and rare-earth metals present in the waste streams. The knowledge obtained will permit the selection of appropriate removal technologies. In the project’s second phase, one promising technology will be tested on a small scale for the removal or recovery of one or several metals from water, sludge and/or fly ash.

Disposal routes for metals and other residuals

Attention will also be directed to: the identification of potential alternative disposal routes for domestic wastewater sludge with a lowered content of heavy metals like copper and zinc; the disposal possibilities of recovered (scarce) heavy metals and (rare) earth metals; and the sustainability of these options. The research project will run until 2019, with the initial results expected in early 2017. It is co-financed by the premium scheme of the Top Sector Alliance for Knowledge and Innovation (TKI) of the Ministry of Economic Affairs. Read more on the TKI Water Technology website.