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Potential urban mining of gold in wastewaters (SUBLIMUS project): Distribution and fluxes of metals in Brussels domestic wastewaters and sludge

Thursday 3 December, 4 PM CET

Dr. Natacha Brion

ABSTRACT: SUBLIMUS’ general objective is to develop an efficient, integrated, low-cost, and green procedure/methodology to harvest the substantial quantities of gold and silver (and other associated precious metals) present in urban wastewater and wastewater treatment plant (WWTP) residues, such as sludges. The first step towards this objective is to characterize the potential PM reservoirs for their recovery all along the wastewater treatment line. For this, it is important to understand the (precious) metal dynamics during the whole procedure of wastewater and sludge treatment. Here we will present results from a 1-year monitoring that allowed to quantify at a yearly scale the mass budget of 23 elements – including precious metals – all along the wastewater and sludge treatment lines of the 2 Brussels WWTP. From the precious metals considered (Ru, Rh, Ir, Pd, Pt, Au and Ag), only Au and Ag are efficiently trapped in sludge during the wastewater treatment process – the others being mainly released to the Zenne river with treated waters. We also compared the precious metal content of Brussels sludge with other cities and found that concentrations in Brussels-North are in the high range, with only Antwerp having higher levels. Finally, we also showed that wet oxidation (WetOx) of digested sludge was an efficient and selective leaching technique for Au and Pt; and that incinerated sewage sludge ashes are enriched in Au and other metals – contrary to the wet oxidized sludges from Brussels. Finally, we identified two different types of precious metal reservoirs that could be used for urban mining.

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