Quantification of individual Rare Earth Elements from industrial sources in sewage sludge

Abstract

Rare Earth Elements (REEs) are used in increasing amounts in technical applications and consumer products. However, to date, the contribution of industrial sources to the loads of individual REEs in wastewater streams have not been quantified. Here, we determine the REE contents in sludge collected from 63 wastewater treatment plants (WWTPs) across Switzerland. To quantify the industrial fraction of individual REEs in the sewage sludge, we develop two complementary approaches, based on REE ratios and REE pattern fitting. Unspecific (background) inputs, with REE patterns similar to the averaged REE pattern of soils collected across Switzerland, dominate the REE budget of most WWTPs. A few WWTPs receive significant REE inputs from specific industrial sources. Based on population equivalents of Switzerland, we estimate a total annual load of 4200 kg Cerium (Ce, 0.5 g Ce year -1 capita -1 ), with an industrial contribution of 2000 kg year -1 . The latter agrees with estimates of probabilistic mass flow models for engineered nanoscale CeO 2 particles discharged to the sewer network. About 7 kg year -1 of Samarium (Sm,total for Switzerland: 184 kg year -1 or 0.02 g Sm year -1 capita -1 ) and 3 kg year -1 of Europium (Eu,total for Switzerland: 44 kg year -1 or 0.005 g Eu year -1 capita -1 ) are assigned to industrial inputs from single WWTPs. Gadolinium (Gd) is used in the form of a stable complex as contrast agent in magnetic resonance imaging. Assuming 10% removal of Gd during wastewater treatment, we calculate an annual discharge of 90 kg of Gd from one individual WWTP to surface waters. WWTPs with exceptionally high industrial inputs of specific REEs warrant detailed investigations to identify the respective sources and to assess whether REE concentrations in effluents are elevated to the same degree.

Emerging investigator series: automated single-nanoparticle quantification and classification: a holistic study of particles into and out of wastewater treatment plants in Switzerland

“…S11. † Our results are consistent with those of a recent study, 54 which reports the measurement of high industrial contribution of Ce to the sludge of W1 based on REE ratios of the sludge compared to that of local soils. Additionally, recent X-ray absorption spectroscopy analysis of Ce–La NPs from W1, 23 also suggest that Ce–La association is not a definitive marker for naturally sourced Ce-containing NPs.…”

Scandium, yttrium, and lanthanide occurrence in Cantharellus cibarius and C. minor mushrooms

“…Coal fly ash contains a certain amount of REE (Franus et al 2015 ) and as an anthropogenic waste it can be considered a diffusive source of REE deposition in the ground, although it may generally be a poor source. Sewage sludge from wastewater treatment plants can contain REE and especially if such a facility receives input from specific industrial sources that could contain REE (Kaegi et al 2021 ). Treated municipal sewage sludge can possibly be used in forested lands (Zabowski et al 1990 ) and/or in agricultural soils (under certain circumstances and regulations as seen in Poland) and this could be a source of REE for forest and field mushrooms.…”

Urban geochemistry and human-impacted imprint of dissolved trace and rare earth elements in a high-tech industrial city, Suzhou

“…The growing industrial demands for Li are as the key materials of the secondary Li-ion battery. Compared to the traditional heavy metal pollutants (e.g., Fe and Cu), Gd and Li are widely used in recent years, especially in high-tech industrial and medical applications rather than conventional industrial (Ne ´grel et al, 2020;Kaegi et al, 2021). Meanwhile, due to the ecotoxicity, adverse ecological and human health effects of Gd and Li remain unclear, these high-tech elements have not been monitored in policy or reduced in sewage system.…”