THE EFFECT OF DIFFERENT CARBON-SOURCES ON RESPIRATORY DENITRIFICATIONIN BIOLOGICAL WASTE-WATER TREATMENT

The respiratory denitrification activity of activated sludge bacteria with different carbon sources (acetic acid, crude syrup, hydrolyzed st arch, methanol-with and without a small amount of yeast extract) was s tudied in long-term continuous cultivations and batch tests. Mass bala nce calculations showed that the main product in long-term cultivation s with all carbon sources was molecular nitrogen. However, the type of carbon source had a significant influence on the denitrification rate , denitrification yield, sludge yield and the composition of the micro flora. With acetate and methanol higher denitrification yields, lower sludge yields and more true (end product N-2) denitrifying bacteria we re obtained than with crude syrup and hydrolyzed starch. Furthermore, with acetate a higher growth rate and a higher denitrification rate wa s obtained than with methanol.