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

Area of Science:

• Environmental Science
• Microbiology
• Nanotechnology

Background:

• Engineered nanoparticles (ENPs) are increasingly present in wastewater sludge.
• The impact of aged ENPs on anaerobic digestion (AD) performance is not well understood.

Purpose of the Study:

• To investigate the effects of aged ENPs (silver oxide, titanium dioxide, zinc oxide) on sludge digestion performance.
• To assess the impact on microbial community structure and function.

Main Methods:

• Pilot-scale anaerobic digesters (150L) were fed with sludge spiked with aged ENPs or metal salts at varying concentrations (250-2800 mg/kg dw).
• Analyzed volatile fatty acids (VFA), hydrogen sulfide, ether-linked isoprenoids, and microbial community composition using pyrosequencing.

Main Results:

• Volatile fatty acids (VFA) increased by 1.2 times in spiked digesters.
• Methanogen abundance and diversity decreased significantly (up to 80%) in ENP-spiked digesters.
• Specific methanogens (Methanosarcina acetivorans, M. barkeri) exhibited nano-tolerance, increasing in relative abundance.

Conclusions:

• Aged ENPs inhibit sludge digestion by reducing methanogen populations and altering microbial community structure.
• Certain bacteria, like Fusobacteria and Actinobacteria, showed resilience, while specific methanogens displayed nano-tolerance.
• ENPs can exert a 'Trojan horse' effect, favoring specific microbial groups.