Biodegradation and effect of formaldehyde and phenol on the denitrification process

Formaldehyde and phenol biodegradation during the denitrification process was studied at lab-scale, first in anoxic batch assays and then in a continuous anoxic reactor. The biodegradation of formaldehyde (260 mg 1(-1)) as single carbon source and Lit phenol concentrations ranging from 30 to 580 mg 1(-1) was investigated in batch assays, obtaining an initial biodegradation rate around 0.5 g CH2O g VSS-1 d(-1). With regard to phenol, its complete biodegradation was only observed at initial concentrations of 30 and 180 mg 1(-1). The denitrification process was inhibited at phenol concentrations higher than 360 mg 1(-1). Studies were also done using a continuous anoxic upflow sludge blanket reactor in which formaldehyde removal efficiencies above 99.5% were obtained at all the applied formaldehyde loading rates, between 0.89 and 0.14g COD (CH2O)1(-1) d(-1). The phenol loading rate was increased from 0.03 to 1.3 g COD (C6H6O)1(-1) d(-1). Phenol removal efficiencies above 90.6% were obtained at phenol concentrations in the influent between 27 and 755 mg 1(-1). However, when the phenol concentration was increased to 1010 mg 1(-1), its removal efficiency decreased. Denitrification percentages around 98.4% were obtained with phenol concentrations in the influent up to 755 mg 1(-1). After increasing phenol concentration to 1010 mg 1(-1), the denitrification percentage decreased because of the inhibition caused by phenol. (C) 2004 Elsevier Ltd. All rights reserved.