title: Distributions and activities of ammonia oxidizing bacteria and polyphosphate accumulating organisms in a pumped-flow biofilm reactor.
abstract: The spatial distributions and activities of ammonia oxidizing bacteria (AOB) and polyphosphate accumulating organisms (PAOs) were investigated for a novel laboratory-scale sequencing batch pumped-flow biofilm reactor (PFBR) system that was operated for carbon, nitrogen and phosphorus removal. The PFBR comprised of two 16.5l tanks (Reactors 1 and 2), each with a biofilm module of 2m(2) surface area. To facilitate the growth of AOB and PAOs in the reactor biofilms, the influent wastewater was held in Reactor 1 under stagnant un-aerated conditions for 6 h after feeding, and was then pumped over and back between Reactors 1 and 2 for 12 h, creating aerobic conditions in the two reactors during this period; as a consequence, the biofilm in Reactor 2 was in an aerobic environment for almost all the 18.2 h operating cycle. A combination of micro-sensor measurements, molecular techniques, batch experiments and reactor studies were carried out to analyse the performance of the PFBR system. After 100 days operation at a filtered chemical oxygen demand (COD(f)) loading rate of 3.46 g/m(2) per day, the removal efficiencies were 95% COD(f), 87% TN(f) and 74% TP(f). While the PFBR microbial community structure and function were found to be highly diversified with substantial AOB and PAO populations, about 70% of the phosphorus release potential and almost 100% of the nitrification potential were located in Reactors 1 and 2, respectively. Co-enrichment of AOB and PAOs was realized in the Reactor 2 biofilm, where molecular analyses revealed unexpected microbial distributions at micro-scale, with population peaks of AOB in a 100-250 microm deep sub-surface zone and of PAOs in the 0-150 microm surface zone. The micro-distribution of AOB coincided with the position of the nitrification peak identified during micro-sensor analyses. The study demonstrates that enrichment of PAOs can be realized in a constant or near constant aerobic biofilm environment. Furthermore, the findings suggest that when successful co-enrichment of AOB and PAOs occur in biofilm environments, such as in the PFBR system, they do so at different zone depths in the biofilm.
authors: Department of Civil Engineering, National University of Ireland, Galway, Ireland.
authors: Guangxue
authors: G
authors: Wu
authors: Michael
authors: M
authors: Nielsen
authors: Ketil
authors: K
authors: Sorensen
authors: Xinmin
authors: X
authors: Zhan
authors: Michael
authors: M
authors: Rodgers
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D044822:Biodiversity; D018441:Biofilms / Q000254:growth & development*; D019149:Bioreactors / Q000382:microbiology*; D015374:Biosensing Techniques; D017753:Ecosystem; D017404:In Situ Hybridization, Fluorescence; D010084:Oxidation-Reduction; D011122:Polyphosphates / Q000378:metabolism*; D011157:Population Dynamics; D013997:Time Factors; D018508:Water Purification / Q000379:methods
chemical_list: D011122:Polyphosphates; D000641:Ammonia