NITRATE AND NITRITE REDUCTIONS WITH ANAEROBIC SLUDGE USING VARIOUS CARBON-SOURCES - GLUCOSE, GLYCEROL, ACETIC-ACID, LACTIC-ACID AND METHANOL

Batch-tests were used to determine the potentials of digested sludge t o reduce nitrate and nitrite in the presence of five different carbon sources: glucose, glycerol, acetic acid, lactic acid and methanol. Amm onium accumulation was found in glucose and glycerol media. Dissimilat ory reduction to ammonium accounted for up to 50% of reduced nitrate a nd nitrite. The rest were denitrified. In the media containing these c arbon substrates volatile fatty acids, particularly acetic acid, were produced and ammonification was higher than denitrification activities only when glucose and glycerol were still present in the media. Ammon ium production was higher in nitrite cultures than in nitrate cultures . In the culture media with acetic and lactic acids and methanol, ammo nium was not detected. Nitrate/nitrite reduction in acetic and lactic acids media was essentially denitrification activity. Up to 100% of re duced nitrate and nitrite in the culture media with these acids were d enitrified at average rates between 27 and 23 mg N-NO(x)/g MLVSSh, nit rite reduction rate being about 14% lower than total nitrate reduction rate. COD requirements for nitrate and nitrite reductions were genera lly lower in cultures with acetic and lactic acids than in glucose and glycerol cultures. Methanol culture media showed a very small reducti on rate for the N-NO(x) indicating the absence (or presence in very sm all quantity) of the bacteria capable of denitrifying with this substr ate.