THE FLORIDA STATE UNIVERSITY ARTS AND SCIENCES ...

Of the variety of factors that control denitrification, this is perhaps the simplest to
understand, yet it is much more complicated than simply excluding the occurrence of
denitrification based on pore size. While it may be true that in fine grain aquitards
denitrification may be ruled out, in dual porosity aquifers it is entirely feasible for
denitrification to occur in favorable conditions (Rivett, 2008).
1.2.9. Microbial acclimation
Acclimation is the lead time before a microbial population can adapt to new conditions.
(Korom, 2008). This may have an effect on the reported amounts of nitrate removed due
to denitrification. If sampling was conducted in a short period of time without allowing
the bacteria to adapt to their new conditions, it may result in an underestimation of the
importance of denitrification within a system.
1.2.10. Hydraulic Retention Time
A limiting factor to bacterial denitrification capacities/ rates is the fluid velocity, which
can transport
−
NO 3 through the system more rapidly than the bacteria can degrade the
- -4 -2
NO3 (Kolpin, 1997; Puckett et al., 2008). A hydraulic conductivity range of 10 to 10
m/s is considered ideal for enhancement of denitrification (Sanchez-Perez et al., 2003).
Hydraulic retention times of 1.5 days or less require a large excess of carbon to obtain
complete denitrification (Martienssen & Schops, 1999).
In order for complete denitrification to occur, a low denitrification rate would require a
high hydraulic retention time, while higher denitrification rates may be effective in lower
hydraulic retention times.
1.3. Methods to test for the occurrence of denitrification
Confirming the occurrence of denitrification is not a trivial matter (Rivett et al., 2007,
2008) as it usually requires several mutually supportive evidential lines. There are several
different methods to verify the occurrence of denitrification. Three commonly used
methods are outlined below; for a comprehensive list the reader is referred to Groffman
(1995) and Groffman et al. (2006).
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