A COMPARISON BETWEEN ETHANOL AND METHANOL AS CARBON-SOURCES FOR DENITRIFICATION

Ethanol and methanol were compared for their performance as carbon sou rces for denitrification. The study was carried out in two chemostats, operated in parallel on synthetic media containing ethanol and methan ol respectively as carbon sources, In addition, pure culture studies w ere performed on one ethanol- and one methanol-utilizing denitrifier. Ethanol was found to be considerably more readily available as a carbo n source for denitrification than was methanol. An efficient denitrifi cation with ethanol was established in a short time, while denitrifica tion with methanol required a substantial adaptation time and never sh owed the same stability as denitrification with ethanol. The growth ra te of denitrifiers with ethanol as carbon source was 2-3 times higher than with methanol. The amount of COD required to denitrify a certain amount of nitrate was somewhat lower for ethanol (3.85 g/gN) than for methanol (4.45 g/gN) in the continuous experiments, while it was consi derably higher for ethanol (6.1 g/gN) than for methanol (4.1 g/gN) in pure culture batch cultivations.