Denitrification in a packed bed biofilm reactor (BIOFOR) — Experiments with different carbon sources

The objective of this laboratory study was to investigate the efficiency of hydrolysed sludge and solid organic waste as a carbon source for denitrification in a packed bed reactor compared to ethanol and acetic acid. An artificial wastewater with a temperature in the range of 9–11°C was used. The denitrification rate, the COD consumption and utilization efficiency and the pressure drop were response parameters. Under the experimental conditions, a maximum denitrification rate of about 2.5 kg NO 3-N/m 3·d was achieved with ethanol, whereas acetic acid gave a lower and more variable rate below 2 kg NO 3-N/m 3·d. The required COD/NO 3-N ratio with ethanol was close to 4.5 g COD/g NO 3-N. A reduced rate was found at effluent concentrations below 15 mg COD/l. Hydrolysate from sludge and solid organic waste gave the same maximum denitrification rate as ethanol, but a ratio of 8–10 g COD/g NO 3-N was required. The rate decreased at effluent concentrations below 75 mg COD/l. While close to 60% of the COD in the hydrolysate was removed, only 45% was utilized for denitrification. The removal of phosphorus was found to be three times higher than the theoretical consumption based on growth.