Assessment of microbial community structure and function in serially passaged wastewater electro-bioreactor sludge

Sludge recycling and settling are an important part of biological wastewater treatment systems, which influence the response and stability of the system. In this study, sludge from wastewater bioreactors subjected to current densities at 3 and 7 Am-2 was serially passaged for 15 days. Illumina MiSeq sequencing were used to assess sludge microbial community shifts over time. The removal efficiency of soluble chemical oxygen demand (sCOD) ranged from (91 – 97 %), while phosphorous (PO43--P) removal was approximately 99% in the different bioreactors tested. Phylogenetic analysis revealed that inductors of sludge bulking and foaming such as Comamonadaceae and Flavobacteriaceae evolved quite differently in all bioreactors tested. The results reported here are the first to describe the effects of current density on microbial community structures in serially passaged sludge. The application and validation of this technique at large scale should be assessed to optimize electro-bioreactors performance.