ISSN:
1574-6968
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Abstract Microzonation of denitrification in trickling filter biofilms was studied using a combined microsensor for O2 and N2O. Denitrification was measured as a function of concentrations of O2, NO3−, organic matter and NH4+ and was found to occur only in part of the biofilm. At increased concentrations of NO3− the thickness of the denitrifying zone increased and thereby increased the total denitrification whereas addition of dissolved organic matter increased the rates of denitrification within the denitrifying part of the biofilm, expressed per volume biofilm. The presence of NH4+ decreased the rate of NO3− assimilation and thereby increased the availability of NO3− for denitrification. Denitrification was only found at O2 concentrations below approximately 20 μM. The toxic zone normally extended 0.2–0.3 mm below the biofilm surface, but when the biofilm was exposed to light photosynthetically produced O2 pushed the oxic-anoxic interface down to 1.3 mm. Denitrification stopped when O2 was introduced to the denitrifying zone, but even after exposure to O2 for 18 h denitrification began immediately after returning to anoxic conditions. Steady state in denitrification was then reached in only 30 min and the rate found then was identical to the rate before exposure to O2, as well as the rate 15 h after return to anoxia. The immediate onset of denitrification suggest that most of the denitrifiers in the biofilm possessed constitutive enzyme systems for denitrification.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1574-6968.1992.tb05771.x
