Capacity of denitrification by polyphosphate accumulating organism at different electron donors

SBR reactor was performed to incubate polyphosphate accumulating organism (PAO), and it was checked out of the system by fluorescence in situ hybridization. As PAO is a kind of ordinary heterotrophic bacteria, it was excluded the ability of phosphate release and uptake and it was considered only the capacity of denitrification of the target biomass. The results indicated that acetate and PHB can be the electron donors of PAO to denitrify. When fed with acetate, the denitrifying rate and PHB producing rate were independent of initial nitrate concentration. However, served as more nitrate in the reactor, it would be less PHB produced and fewer nitrate reducing when using same amount of acetate. In view of PHB stored as an internal carbon and energy source, it presented as a reaction of zero-order to the substrate by PAO to denitrify, such as nitrate, besides, the specific denitrifying rate was 0.9733 mg/(g x h) and the specific PHB consuming rate was 2.4626 mg/(g x h).
  • [Show abstract] [Hide abstract] ABSTRACT: The external nitrification (EN) biological nutrient removal (BNR) activated sludge (ENBNRAS) system shows considerable promise for full-scale implementation. As an aid for this implementation, a mathematical simulation model would be an invaluable tool. To develop such a model, a study was conducted to select the most suitable simulation model to serve as a starting point for further development. For this, the existing available simulation models for BNRAS systems are compared with one another and evaluated against experimental observations in the literature and on ENBNRAS systems. One process immediately apparent to be crucially important is the anoxic growth of phosphorus accumulating organisms (PAOs), with associated PAO denitrification and anoxic P uptake for polyP formation. These linked processes are lacking in the earlier kinetic simulation models for BNRAS systems, which were based on aerobic PAO growth and P uptake only, but have been incorporated into the more recent kinetic models. This provides a substantive body of information on modelling this aspect. Other processes of significance identified to require consideration are anaerobic slowly biodegradable COD (SBCOD) hydrolysis to readily biodegradable COD (RBCOD), and COD loss. Both processes have significant impact on the predicted BEPR performance. Due to the uncertainties associated with the mechanisms and quantification of these two processes, it is concluded that the most extensively validated kinetic simulation model should be selected for development, and that the omissions in this model should be addressed progressively, using the relevant information drawn from the existing models, the literature and observations on ENBNRAS systems.
    Full-text · Article · Sep 2003