title: Modes of operation and pH control as enhancement factors for partial nitrification with oxygen transport limitation.
abstract: Sequencing batch (SBR) and continuous operation modes were applied using different pH control strategies to enhance partial nitrification in a biofilm rotating disk reactor. The pH control strategies were supervisory control in the range of 7.5-8.6 and fixed pH at 7.5 and 8.5, at dissolved oxygen (DO) concentrations in the range of 0.6-5.0 mg O(2)/L. Supervisory pH control enabled operation at a free ammonia concentration inhibitory to the nitrite-oxidizing bacteria (NOB) and an optimum for the ammonia-oxidizing bacteria (AOB). The results indicate that both operation modes were simultaneously controlled by oxygen transport and micro-kinetics (influenced by pH and NH(3)). The SBR mode with supervisory pH control presented more stable partial nitrification-nitrite accumulation >80% for 249 days than continuous operation. Molecular analyses showed that the SBR operation with supervisory pH control at low DO concentrations contributed to the enrichment of the AOB (>95%) over the NOB (<5%) populations. Therefore, it can be stated that a suitable pH control strategy can act as an enhancement factor of partial nitrification even under oxygen-transport-limiting conditions.
authors.affiliation: Universidad de La Frontera, Cas. 54-D, Temuco-Chile. gciudad@ufro.cl
authors.forename: G
authors.initials: G
authors.lastname: Ciudad
authors.forename: R
authors.initials: R
authors.lastname: González
authors.forename: C
authors.initials: C
authors.lastname: Bornhardt
authors.forename: C
authors.initials: C
authors.lastname: Antileo
mesh_terms: D000641:Ammonia / Q000378:metabolism; D001419:Bacteria / Q000235:genetics / Q000378:metabolism; D019149:Bioreactors; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D010100:Oxygen / Q000032:analysis; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D009566:Nitrates; D009573:Nitrites; D000644:Quaternary Ammonium Compounds; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D014874:Water Pollutants, Chemical; D000641:Ammonia; D009584:Nitrogen; D010100:Oxygen