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Aged-engineered nanoparticles effect on sludge anaerobic digestion performance and associated microbial communities

Eduok, Samuel, Ferguson, Robert, Jefferson, Bruce, Villa, Raffaella, Coulon, Frédéric
The Science of the total environment 2017 v.609 pp. 232-241
Actinobacteria, Fusobacteria, Methanosarcina acetivorans, Methanosarcina barkeri, activated sludge, anaerobic digesters, anaerobic digestion, digesters, hydrogen sulfide, isoprenoids, methanogens, microbial communities, nanoparticles, sequence analysis, silver oxide, sulfates, titanium dioxide, volatile fatty acids, waste treatment, zinc oxide
To investigate the potential effect of aged engineered nanoparticles (a-ENPs) on sludge digestion performance, 150L pilot anaerobic digesters (AD) were fed with a blend of primary and waste activated sludge spiked either with a mixture of silver oxide, titanium dioxide and zinc oxide or a mixture of their equivalent bulk metal salts to achieve a target concentration of 250, 2000, and 2800mgkg⁻¹ dry weight, respectively. Volatile fatty acids (VFA) were 1.2 times higher in the spiked digesters and significantly different (p=0.05) from the control conditions. Specifically, isovaleric acid concentration was 2 times lower in the control digester compared to the spiked digesters, whereas hydrogen sulfide was 2 times lower in the ENPs spiked digester indicating inhibitory effect on sulfate reducing microorganisms. Based on the ether-linked isoprenoids concentration, the total abundance of methanogens was 1.4 times lower in the ENPs spiked digester than in the control and metal salt spiked digesters. Pyrosequencing indicated 80% decrease in abundance and diversity of methanogens in ENPs spiked digester compared to the control digester. Methanosarcina acetivorans and Methanosarcina barkeri were identified as nano-tolerant as their relative abundance increased by a factor of 6 and 11, respectively, compared to the other digesters. The results further provide compelling evidence on the resilience of Fusobacteria, Actinobacteria and the Trojan horse-like effect of ENPs which offered a competitive advantage to some organisms while reducing microbial abundance and diversity.