title: Reactor performance in terms of COD and nitrogen removal and bacterial community structure of a three-stage rotating bioelectrochemical contactor.
abstract: Integrating microbial fuel cell (MFC) into rotating biological contactor (RBC) creates an opportunity for enhanced removal of COD and nitrogen coupled with energy generation from wastewater. In this study, a three-stage rotating bioelectrochemical contactor (referred to as RBC-MFC unit) integrating MFC with RBC technology was constructed for simultaneous removal of carbonaceous and nitrogenous compounds and electricity generation from a synthetic medium containing acetate and ammonium. The performance of the RBC-MFC unit was compared to a control reactor (referred to as RBC unit) that was operated under the same conditions but without current generation (i.e. open-circuit mode). The effect of hydraulic loading rate (HLR) and COD/N ratio on the performance of the two units was investigated. At low (3.05 gCOD g⁻¹N) and high COD/N ratio (6.64 gCOD g⁻¹N), both units achieved almost similar COD and ammonia-nitrogen removal. However, the RBC-MFC unit achieved significantly higher denitrification and nitrogen removal compared to the RBC unit indicating improved denitrification at the cathode due to current flow. The average voltage under 1000 Ω external resistance ranged between 0.03 and 0.30 V and between 0.02 and 0.21 V for stages 1 and 2 of the RBC-MFC unit. Pyrosequencing analysis of bacterial 16S rRNA gene revealed high bacterial diversity at the anode and cathode of both units. Genera that play a role in nitrification (Nitrospira; Nitrosomonas), denitrification (Comamonas; Thauera) and electricity generation (Geobacter) were identified at the electrodes. Geobacter was only detected on the anode of the RBC-MFC unit. Nitrifiers and denitrifiers were more abundant in the RBC-MFC unit compared to the RBC unit and were largely present on the cathode of both units suggesting that most of the nitrogen removal occurred at the cathode.
authors.affiliation: Department of Civil and Environmental Engineering, American University of Beirut, Beirut, Lebanon.
authors.forename: Rassil R
authors.initials: RR
authors.lastname: Sayess
authors.forename: Pascal E
authors.initials: PE
authors.lastname: Saikaly
authors.forename: Mutasem
authors.initials: M
authors.lastname: El-Fadel
authors.forename: Dong
authors.initials: D
authors.lastname: Li
authors.forename: Lucy
authors.initials: L
authors.lastname: Semerjian
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D019149:Bioreactors / Q000382:microbiology*; D020585:Comamonas / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D058440:Denitrification; D055664:Electrochemical Techniques; D045302:Geobacter / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D062070:Hydrology / Q000379:methods; D058889:Molecular Typing; D058465:Nitrification; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D009606:Nitrosomonas / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D010100:Oxygen / Q000032:analysis / Q000378:metabolism*; D010802:Phylogeny; D020560:Proteobacteria / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012329:RNA, Bacterial / Q000737:chemistry / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000378:metabolism; D020628:Thauera / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism; D062065:Wastewater / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000378:metabolism; D018508:Water Purification / Q000295:instrumentation*
chemical_list: D019342:Acetic Acid; D009584:Nitrogen; D010100:Oxygen; D000644:Quaternary Ammonium Compounds; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D062065:Wastewater; D014874:Water Pollutants, Chemical