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Biological denitrifying phosphorus removal in SBR: effect of added nitrate concentration and sludge retention time
M Merzouki1, N Bernet, J P Delgenès
1INRA, Laboratoire de Biotechnologie de l'Environement (LBE), Avenue des Etangs, 11100 Narbonne, France.
Abstract:
Optimizing anoxic biological phosphorus removal in the anaerobic-anoxic sequencing batch reactor (A2 SBR) was observed to depend on two parameters: the amount of added nitrate and the sludge retention time (SRT). The concentration of 120 mg N-NO3.l-1 in the anoxic medium and the SRT of 15 days were determined as optimal for a complete phosphorus removal in the A2 SBR. The reactor was supplied with synthetic wastewater containing 800 mg COD.l-1 acetic acid, 240 mg N-NH4.l-1 and 30 mg P-PO4.l-1. This study was completed by microscopic observations which revealed three morphological types of phosphate-accumulating bacteria (PAB).