Modification of nitrifying microbial community via DC electrical field application

The performance and operational stability of nitrifying-based treatment processes are closely associated with microbial community structures and species-to-species interactions. In this work, we investigated the effect of intermittent direct current (DC) on the change of nitrifying community structure and process performance in a membrane electro-bioreactor (MEBR). Microbial populations and dynamics were characterized using a fluorescent in situ hybridization (FISH) technique. The outcomes demonstrated that the MEBR system achieved substantial nitrification rates compared to a conventional membrane bioreactor (MBR). The MEBR enhanced the removal of NH3+ -N to almost 99%. FISH analysis indicated a dominance of different nitrifying bacteria species in both reactors, leading to differences in nitrification and NH3+ N removal performance. In robust MEBR system, rapid nitrifiers, such as AOB (Nitrosomonas spp.) and NOB (Nitrobacter spp.) were dominat. In contrast, slower nitrifier consortiums like AOB (Nitrosospira spp.) and NOB (Nitrospira spp.) occupied the control MBR. Taken together, the development of fast and robust nitrifying community can lead to extra savings in capital and operational costs of the WWTPs, suggesting the adoption of MEBR oxic/anoxic process. Moreover, a better understanding of biological processes taking place in the new MEBR system and microbial environmental preferences would be valuable for process control and optimization, as well as beneficial for designing bioaugmentation processes, in order to avoid potential washout of target bacteria not adapted to real conditions in bioreactors. Such bio-electrically enhanced processes presented in this work can be used in a new WWTP design or retrofitting existing treatment plants.

Automated summary

The effect of intermittent direct current on the nitrifying community structure and performance in a membrane electro-bioreactor (MEBR) was investigated. The MEBR achieved substantial nitrification rates and enhanced NH3+ -N removal compared to a conventional membrane bioreactor (MBR). Different nitrifying bacteria species dominance in the MEBR and MBR led to differences in nitrification performance. Developing a fast and robust nitrifying community in MEBR can lead to cost savings in WWTPs.