bioreactor sludge metagenome Metagenome

This paper aimed to determine the immigration effect of microorganisms incoming with the feedstock on sewage sludge anaerobic reactors and to identify if some incoming microorganisms were able to survive and grow in the AD microbiome. The experimental design consisted of two reactors: one fed with sewage sludge mix containing alive microorganisms and the other one fed with sterile sewage sludge mix (control) and the reactors were operated exactly alike. The hydraulic retention time (HRT) was 20 days and the experiment lasted 78 days (4 HRT, approximately). Both reactors had similar operational results since no differences were observed between feedstock characteristics. Also, no statistical differences were observed between the bacterial communities of both reactors; however, the archaeal community became different in the fourth HRT. The interaction among microorganisms was analysed and the archaeal community of the reactor fed with non-sterile sewage sludge showed more negative interactions than the sterile. Some immigrant microorganisms survived in the AD microbiome, but none was enriched. This study demonstrated that the continuous entrance of microorganisms into sewage sludge anaerobic reactors affects the interaction type in the archaeal community, and consequently, the diversity.