Carbon source in aerobic denitrification

The objective of this study was to demonstrate denitrification by activated sludge under aerobic conditions. Activated sludge was cultivated in a sequencing batch reactor (SBR) with municipal wastewater enriched by acetate. Poly- beta-hydroxybutyrate was accumulated in activated sludge to 0.35 g PHB/g VSS (f(PHB) = 0.27 Cmol/Cmol). Microorganisms had the opportunity to preserve reducing power from poly-beta-hydroxybutyrate (PHB) stored in microbial cells. Activated sludge, cultivated in such conditions, was used in further experimental series. The duration of each series was 24 h. Two types of synthetic wastewater were used in the presented studies: wastewater without organic compounds, and wastewater with acetate as the main carbon source. Ammonium was the only nitrogen source. Since, ammonium oxidation by activated sludge had to go before denitrification. It was shown that under aerobic, autotrophic conditions, the amount of nitrogen reduced by activated sludge was 4.54 mg N-red/l using intracellular PHB stored in microbial cells, as the only carbon source for denitrification. In wastewater with acetate, the amount of reduced nitrogen due to aerobic denitrification increased to 22.5 mg N-red/l. The results indicted that PHB, stored in activated sludge, can be served as electron donor for aerobic denitrification. Denitritication under aerobic conditions using internal substrate is not as effective as in presence of the internal and external carbon sources but during denitrification, supported by endogenous substrates, the amount of organic compounds in wastewater required for the process can be limited. (c) 2007 Elsevier B.V. All rights reserved.