Project description:Membrane bioreactor (MBR) systems are typically known different from conventional activated sludge (CAS) systems in operational parameters, while current knowledge of their microbial differentiations is barely sufficient. To this end, the current study was launched to address the differences of the overall functional genes of an oxidation ditch (OD) and an MBR running parallelly at full-scale using a functional gene array-GeoChip 4.2. Two full-scale wastewater treatment systems applying the processes of oxidation ditch (OD) and membrane bioreactor (MBR) were investigated. They treated identical wastewater at the same scale. 12 mixed-liquor suspended sludge (MLSS) samples collected daily on 12 consecutive days from each system were analyzed by GeoChip 4.2.
Project description:To further explore the biotoxicity mechanisms of CeO2 nanoparticles (NPs) and the recovery strategies of the according impaired Nitrosomonas europaea (N. europaea, ATCC 19718) cells, a genome-sequenced model ammonia oxidizing bacterium (AOB) commonly detected in the activated sludge of biological wastewater treatment plants, the whole-genome microarray analysis was applied to retrieve the induced transcriptional responses, after their physiological and metabolic activities were evealed.
Project description:To further explore the biotoxicity mechanisms of zinc oxide nanoparticles (ZnO NPs) and the recovery strategies of the accordingly impaired Nitrosomonas europaea (N. europaea, ATCC 19718) cells, a genome-sequenced model ammonia-oxidizing bacterium (AOB) commonly detected in the activated sludge of biological wastewater treatment plants, whole-genome microarray analysis was applied to retrieve the induced transcriptional responses, after their physiological and metabolic activities were revealed.
Project description:To further explore the biotoxicity mechanisms of TiO2 nanoparticles (NPs) and the recovery potentials of the impaired Nitrosomonas europaea (N. europaea, ATCC 19718) cells, a genome-sequenced model ammonia oxidizing bacterium (AOB) commonly detected in the activated sludge of biological wastewater treatment plants, the whole-genome microarray analysis was applied to retrieve the induced transcriptional responses during the long-term exposure, after the toxicity effects and the recovery potentials were assessed at both physiological and metabolic levels.
Project description:To further explore the biotoxicity mechanisms of zinc oxide nanoparticles (ZnO NPs) and the recovery strategies of the accordingly impaired Nitrosomonas europaea (N. europaea, ATCC 19718) cells, a genome-sequenced model ammonia-oxidizing bacterium (AOB) commonly detected in the activated sludge of biological wastewater treatment plants, whole-genome microarray analysis was applied to retrieve the induced transcriptional responses, after their physiological and metabolic activities were revealed. The whole-genome expressions were measured after exposure to 50 ppm ZnO NPs and 12-hrs recovery incubation when the ammonia removal rate (ARA) declined by 10% in the chemostat bioreactor. Three independent experiments were performed for each experiment.
Project description:Wastewater treatment plants use a variety of bioreactor types and configurations to remove organic matter and nutrients. Little is known regarding the effects of different configurations and within-plant immigration on microbial community dynamics. Previously, we found that the structure of ammonia-oxidizing bacterial (AOB) communities in a full-scale dispersed growth activated sludge bioreactor correlated strongly with levels of NO2- entering the reactor from an upstream trickling filter (Wells et al 2009). Here, to further examine this puzzling association, we profile within-plant microbial biogeography (spatial variation) and test the hypothesis that substantial microbial immigration occurs along a transect (raw influent, trickling filter biofilm, trickling filter effluent, and activated sludge) at the same full-scale wastewater treatment plant. AOB amoA gene abundance increased >30-fold between influent and trickling filter effluent concomitant with NO2- production, indicating unexpected growth and activity of AOB within the trickling filter. Nitrosomonas europaea was the dominant AOB phylotype in trickling filter biofilm and effluent, while a distinct ‘Nitrosomonas-like’ lineage dominated in activated sludge. Prior time series indicated that this ‘Nitrosomonas-like’ lineage was dominant when NO2- levels in the trickling filter effluent (i.e., activated sludge influent) were low, while N. europaea became dominant in the activated sludge when NO2- levels were high. This is consistent with the hypothesis that NO2- production may co-occur with biofilm sloughing, releasing N. europaea from the trickling filter into the activated sludge bioreactor. Phylogenetic microarray (PhyloChip) analyses revealed significant spatial variation in taxonomic diversity, including a large excess of methanogens in the trickling filter relative to activated sludge and attenuation of Enterobacteriaceae across the transect, and demonstrated transport of a highly diverse microbial community via the trickling filter effluent to the activated sludge bioreactor. Our results provide compelling evidence that substantial immigration between coupled process units occurs and may exert significant influence over microbial community dynamics within staged bioreactors.
Project description:To further explore and differentiate the biotoxicity mechanisms of individual nanoparticles (NPs) and NP mixture on Nitrosomonas europaea (N. europaea, ATCC 19718) at genetic level, a genome-sequenced model ammonia oxidizing bacterium (AOB) commonly detected in the activated sludge of biological wastewater treatment plants, the induced whole-genome expressions were analyzed with the high throughput Microarray technique, after the dose-dependent changes of N. europaea’s physiological, metabolic and AMO enzyme activities in single and dual component NP systems was evaluated.
