Effects of different carbon sources on denitrification efficiency associated with culture adaptation and C/N ratio

Abstract

Stringent effluent limitations for nitrogen necessitate an accurate interpretation of the design and operation conditions of biological nitrogen removal systems. In this study, the effects of the nature of the organic substrate on biomass adaptation and response to different C/N ratios in terms of denitrification efficiency were investigated. A relatively high chemical oxygen demand (COD)utilized/NOx-Nreduced ratio of 8.1 was obtained when an excess amount of readily biodegradable carbon was supplied, which is suggested as the conversion of substrate surplus into storage polymers. An anoxic yield of 0.64 g cell COD/g COD for a four-compound substrate mixture (acetate, propionate, ethanol and glucose), 0.63 g cell COD/g COD for a two-compound substrate mixture (acetate and propionate), and 0.5 g cell COD/g COD for methanol were calculated. Fluorescence in situ hybridization analysis showed that the b-subclass of proteobacteria was dominant in the seed and in cultures adapted to both the fourcompound and the two-compound substrate mixture, whereas in the methanoladapted culture significant amounts of β-proteobacteria were detected. The biocommunity composition, the type of organic compound and the COD/NO3-N ratio strongly influence the nitrate reduction and carbon utilization profiles. Methanol has been shown to select for a denitrifying population consisting of Paracoccus and Hyphomicrobium vulgare genera, when used as only external carbon source. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.