Combusted-diesel additives containing CeO2 nanomaterials shape methanogenic pathways during sludge digestion and enhance biogas production

This study addressed the impact of nanomaterials on anaerobic digestion and biogas production (methanogenesis pathways) when contaminating aerobic sludge is generated during wastewater treatment. Our experimental system was based on bioreactor operational parameters aligned with the operating conditions used in wastewater treatment plants (WWTP), a contamination scenario considering the treatment of nano-enabled products at the last stages of their life cycle, and nanomaterial concentrations close to those predicted in WWTP. The physico-chemical, microbiological and chemical engineering proxies studied all concluded that combusted nanoCeO(2)-enabled fuel additives transiently increased EPS production and specific hydrolytic enzymatic activities without altering the aerobic sludge microbial community structure nor the C, P, N removal capacity (spiked concentrations of 130 mu g L-1 during aerobic sludge production). However, the presence in the aerobic sludge biosolids of 99.9% of the total CeO2 injected (without any change in speciation) altered the production, structure, and activity of the anaerobic sludge during digestion (impacting the EPS, ATP, lipase and alpha-glucosidase activities). Interestingly, these modifications of the anaerobic sludge activity shaped the methanogenesis pathways from acetoclastic to hydrogenotrophic and enhanced the biogas production with a significant increase in generated H-2. In the context of developing a sustainable energy supply, we observed a continuous improvement of the biogas production in the contaminated bioreactor, which could increase the energy recovery potential of WWTPs.

Automated summary

This study investigated the effect of nanomaterials on anaerobic digestion and biogas production. The presence of nanomaterials was found to impact the activity and biogas production of anaerobic sludge.