The effect of volatile fatty acids on the nitrification of a saline effluent.
Anaerobically produced volatile fatty acids (VFA) may affect the nitrification yield. The effect of the type of VFA (acetic, propionic and butyric acid) on nitrification of a saline (24 g NaCl l(-1)) medium was studied. Nitritation (40 mg N-NH4+ l(-1)) and nitratation (100 mg N-NO2- l(-1) were assessed in batch cultures fed with different VFA (32 mg TOC l(-1)). The effect of increasing VFA concentrations on nitrification was studied in batch reactors fed with an initial concentration of 40 mg N-NH4+ l(-1) and C/N ratios of 0, 2, 4, 8 and 16 as well as in a continuous mixed flow reactor operated at 30 degrees C and pH 7.5 and fed with 500 mg N-NH4+ l(-1) and 500, 1000, 2000, and 4000 mg TOC l(-1). Nitritation and nitratation rates were decreased by organic matter; inhibition increased with the VFA size. A non-competitive inhibition model fitted the experimental data on nitrification rate reduction at increasing acetic add concentrations; inhibition constants were 685 mg acetic acid l(-1) for ammonia oxidation and 74.3 mg acetic acid l(-1) for nitrite oxidation. The continuous reactor's nitrifying ability decreased from 82% to 40% at C/N ratios 1 and 4, respectively. Loss of nitrification, but a 50% ammonia removal was found at a C/N of 8. It was concluded that the nitrification rate reduction is proportional to the VFA molecular weight and that an increase in VFA concentration diminishes the nitrifying ability due to kinetic limitations.
Delgado
A
A
Departamento de Ingeniería Química, Facultad de Ingeniería, Casilla 160-C, Fax (56)(41) 243750, Universidad de Concepción, Concepción, Chile.
Aspé
E
E
Martí
M C
MC
Roeckel
M
M
D000085:Acetates / Q000378:metabolism; D019149:Bioreactors; D002087:Butyrates / Q000378:metabolism; D002244:Carbon / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D006801:Humans; D009584:Nitrogen / Q000378:metabolism; D011422:Propionates / Q000378:metabolism; D012722:Sewage / Q000737:chemistry*; D014835:Volatilization
D000085:Acetates; D002087:Butyrates; D005227:Fatty Acids; D011422:Propionates; D012722:Sewage; D002244:Carbon; D009584:Nitrogen