METABOLIC PROPERTIES OF DENITRIFYING BACTERIA ADAPTING TO METHANOL AND ETHANOL IN ACTIVATED SLUDGE

The effect of external carbon sources on metabolic properties of the denitrifying community in single-sludge systems with predenitrification was investigated. Sludge samples were collected from full-scale and pilot-scale experimental lines during microbial adaption to methanol and ethanol, respectively. Changes in functional properties were studied by measuring denitrification capacity with different electron donors in batch tests using the acetylene inhibition technique. Substrate-use profiles were analysed with principal component analysis. Adaptation to methanol was slow, and the capacity to denitrify with acetate decreased continuously. Short-chain fatty acids were less popular for denitrifiers in the methanol-adapted sludge than they were in the reference sludge, while the capacity to denitrify with methanol and ethanol was higher. Denitrification capacity with ethanol and acetate in the ethanol adapting sludge increased rapidly. The ethanol-adapted sludge also had a higher capacity to denitrify with butyrate, glycerol, and methanol. Neither methanol nor ethanol as external carbon affected denitrification capacity with aromatic compounds or glucose. A reduced ability to denitrify with a vast number of electron donors can be regarded as a negative characteristic, since it reflects a lower capacity to make use of substances in the sewage. © 1998 Elsevier Science Ltd. All rights reserved