Sustained effect of zero-valent iron nanoparticles under semi-continuous anaerobic digestion of sewage sludge: Evolution of nanoparticles and microbial community dynamics

The effects of adding zero-valent iron nanoparticles (nZVI) on the physicochemical, biological and biochemical responses a semi-continuous anaerobic digestion sewage sludge have been assessed. Two sets consecutive experiments 103 116 days, respectively, were carried out in triplicate. nZVI magnetically retained reactors, effect punctual doses (from 0.27 to 4.33 g L?1) over time was studied. Among different parameters monitored, only methane content biogas significantly higher when added. However, this progressively lost after addition, 5–7 returned initial values. increase oxidation state seems be related loss time. Higher dose (4.33 sustained positive for longer along with content, but fact microbiome acclimation. Changes microbial community structure could also play role mechanisms involved enhancement. In sense, consortium analysis reported shift balance among acetogenic eubacterial communities, marked relative abundance members assigned Methanothrix genus, recognized as acetoclastic species showing high affinity acetate, which explain rise biogas. This research demonstrates that enrichment semicontinuous digesters can achieved by using nanoparticles, thus increasing energy production or reducing costs later upgrading process.