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The impact of influent nutrient ratios and biochemical reactions on oxygen transfer in an EBPR process—A theoretical explanation

Authors

  • Venkatram Mahendraker,

    Corresponding author
    1. Sustainability Program, Pulp and Paper Research Institute of Canada, 570 Blvd. St-Jean, Pointe-Claire, Quebec H9R 3J9, Canada; telephone: 514-630-4100, ext. 2238; fax: 514-630-4134
    • Sustainability Program, Pulp and Paper Research Institute of Canada, 570 Blvd. St-Jean, Pointe-Claire, Quebec H9R 3J9, Canada; telephone: 514-630-4100, ext. 2238; fax: 514-630-4134.
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  • Donald S. Mavinic,

    1. Environmental Engineering Group, Department of Civil Engineering, 6250 Applied Science Lane, University of British Columbia, Vancouver BC V6T 1Z4, Canada
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  • Barry Rabinowitz,

    1. CH2M Hill Canada Limited, Metro Tower II, Suite 2100, 4720 Kingsway, Burnaby BC V5H 4N2 Canada
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  • Kenneth J. Hall

    1. Department of Civil Engineering, University of British Columbia, 2324 Main Mall, Vancouver BC V6T 1Z4, Canada
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Abstract

In this investigation, a laboratory-scale enhanced biological phosphorus removal (EBPR) process was operated under controlled conditions to study the impact of varying the influent ratio of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and total phosphorus (TP), and the consequential biochemical reactions on oxygen transfer parameters. The data showed that the experiment with high influent phosphorus relative to nitrogen (COD/TP = 51 and TKN/TP = 3.1) achieved higher α and oxygen transfer efficiency (OTEf). On the other hand, the experiment with high influent nitrogen relative to phosphorus (TKN/TP = 14.7 and COD/TP = 129) resulted in approximately 50% reduction in α and OTEf under similar organic loading. This suggested that the intracellular carbon storage and the enhanced biological P removal phenomenon associated with the phosphorus-accumulating organisms (PAOs) had a positive influence on OTEf in the high phosphorus experiment compared to an active population of nitrifying and denitrifying organisms in the high nitrogen experiment. The intracellular carbon storage by the glycogen-accumulating organisms also appeared to have had a positive effect on oxygen transfer efficiency, although to a lesser extent in comparison to the PAOs. It was also found that oxygen uptake rate (OUR) was not a good indicator of the measured α and OTEf, because it was a combined effect of several biochemical reactions, each having a varying degree of influence. It is difficult to underestimate the crucial role of flocs in mass transfer of oxygen, because microorganisms associated with flocs carry out the biochemical reactions. It seems that the combination of influent characteristics and biochemical reactions in each experiment produced a unique biomass quality (determined by the biomass N to P ratio), ultimately affecting the mass transfer of oxygen. A theoretical explanation for the observed oxygen transfer efficiency under the process conditions is also proposed in this article. © 2005 Wiley Periodicals, Inc.

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