IngentaConnect Effect of AnaerobicAerobic Contact Time on the Change of Internal...

Abstract:

Laboratory-scale sequential batch reactors were operated by feeding acetate and glucose as a single carbon source under the anaerobic-aerobic hydraulic retention times (HRTs) of 40:140 minutes and 120:560 minutes to assess the effect of anaerobic-aerobic HRTs on changes in internal storage energy of two different phosphorus-accumulating organisms (PAOs). The PAOs grown on acetate accumulated poly-Beta-hydroxybutyrate in cells with a phosphorus content (phosphorus per volatile suspended solids, P/VSS) of 20 to 23%, whereas PAOs grown on glucose accumulated glycogen in cells with a phosphorus content of 10 to 15%. A longer anaerobic HRT resulted in a secondary phosphorus release that was not associated with internal cellular energy synthesis. A longer aerobic HRT resulted in a depletion of cellular energy. The PAOs with lower cellular energy may lose their competitive edge against other nonPAOs in biological phosphorus removal (BPR) systems. The danger in oversizing the anaerobic and aerobic zones in a BPR system was demonstrated. Optimal anaerobic HRT should be based on the volatile fatty acid uptake rate or the fermentation rate and optimal aerobic HRT should be determined based on the amount of internal energy synthesized during the anaerobic stage and the target effluent phosphorus concentration. From the analysis of cellular fatty acid composition and a metabolic study, PAOs grown on acetate were found to differ from those grown on glucose. Any PAO biochemical models proposed so far could not explain the metabolism of PAOs grown on glucose.

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Effect of Anaerobic-Aerobic Contact Time on the Change of Internal Storage Energy in Two Different Phosphorus-Accumulating Organisms