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Impact of rare earth elements on wastewater microbial communities, The
Aurelius, Stephanie
Aurelius, Stephanie
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2021
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Abstract
Rare earth elements (REEs) are essential in the manufacture and development of modern technologies. REEs reach water resource reclamation facilities (WRRFs) from hospital and industrial wastewater effluents. The increasing prevalence of REEs motivates the need to understand how they affect the activities and community structure of wastewater microorganisms. Additionally, REEs exhibit antimicrobial properties comparable to heavy metals, which have been shown to co-select for antibiotic resistance.
Plate assays were performed to determine the effect of REE recycling waste on microbial growth. Culturing of REE-resistant cells evaluated the potential for REEs to co-select for antibiotic resistance in wastewater microorganisms. Growth of REE-resistant cells in the presence of antibiotics was explored, and predominant taxa and resistance genes were investigated. The acute effect of REEs and metals on biological nitrification was tested in batch experiments. Additionally, the microbial community was characterized before, during, and after REE-induced inhibition of nitrification in long-term aerobic bioreactor experiments.
Activated sludge growth was inhibited in plates amended with REE recycling waste, though acidity was the main contributor to toxicity. Growth of REE-resistant cultures was similar to, or greater than, unamended sludge growth in the presence of antibiotics. Predominant resistance genes differed between samples exposed to different forms of lanthanum. Compared to the control, lanthanum-resistant samples had higher abundances of kasugamycin resistance genes, with the lanthanum nanoparticle-resistant sample also showing increased fosmidomycin resistance. In batch reactors, lanthanum nanoparticle additions did not affect nitrification, but 1000 $\upmu$M of aqueous lanthanum, dysprosium, and copper reduced ammonia oxidation. Inhibition of nitrification was associated with diminished abundance of nitrifying microbes in aerobic bioreactors amended with high concentrations of yttrium or gadolinium. Abundance of nitrifying microbes returned to pre-treatment levels once additions were stopped in the yttrium-amended reactor, but not in the gadolinium-amended reactor. Our results indicate that high concentrations of REEs may impact community composition and nitrification in wastewater communities.
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