Energetics of enhanced biological phosphorus and nitrogen removal processes

Recent advances by researchers with in vivo NMR spectroscopy using labelled isotopes of carbon and phosphorus have elucidated some of the biochemical pathways involved in enhanced biological phosphorus and nitrogen removal processes. This has permitted a greater understanding of carbon and phosphorus cycling within cellular processes. All microbiological processes associated with energy transformations are dependent on enzyme induction. The enhanced phosphorus removal apparatus in certain organisms is dependent on the environmental conditions in order to induce the necessary enzymes. Enzyme expression has been linked to redox potential, which itself is a function of the culture medium and the bioenergetic condition of the cells. Redox balance is coupled to several pathways in the metabolic network of microorganisms. Changes to the redox potential result in shifts in the metabolic pathway utilisation. In the past, nitrification and denitrification have been thought to be strictly aerobic and anoxic processes respectively. Mounting evidence has demonstrated that this classical view of nitrification and denitrification is no longer valid and that other processes can occur such as simultaneous nitrification and denitrification and aerobic denitrification. Enzyme induction plays a very important role in these processes. Attempts have been made in this paper to elucidate the energetics of anaerobic phosphorus release based on cellular composition and various other plant operating parameters. Energetics of the denitrification process including anoxic dephosphatation, aerobic denitrification, with potential reduction in aerobic treatment requirements, are also explored. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.