Environmental Engineering Reference
In-Depth Information
Values for Monod Nutrient Uptake and Droop Equations for Phosphate a
TABLE 16.1
K s (mg liter 1 )
max (day 1 )
Algal type
Q 0
NO 3 -N or NH 4 -N
Phytoplankton
0.114 (0.0014-0.2)
0.039 (0.0024-0.15)
0.024 (0.015-0.04)
10 7
10 7 )
Diatoms
0.051 (0.001-0.13)
0.07 (0.015-0.125)
3
(0.5-6
10 6
10 7 )
Green algae
0.016 (0.0014-0.030)
0.0925 (0.06-0.125)
1.7
(0.5-34.2
10 7
10 7 )
Cyanobacteria
0.50 (0.03-0.98)
0.0825 (0.04-0.125)
1.93
(0.52-4.3
PO 4 3 -P
Phytoplankton
0.0357 (0.0028-0.07)
0.222 (0.0014-2.95)
0.0014 (0.001-0.003)
Benthic algae
0.125
0.045
0.0005
10 7
10 7 )
Diatoms
0.065 (0.0002-0.06)
0.262 (0.024-0.5)
5.06
(0.01-7
10 9
10 9 )
Green algae
0.28 (0.001-1.5)
0.317 (0.133-0.5)
1.7
(1.7-4.5
10 9
10 9 )
Cyanobacteria
0.5 (0.007-0.98)
0.585 (0.042-0.5)
2.91
(0.58-5.66
a After EPA (1985). Means are followed by ranges in parentheses. Units of Q 0 are in milligrams nutrient
(milligrams cell) 1 for phytoplankton and in micromoles cell 1 for benthic algae. Values from literature review
of one to five studies for each parameter.
[ S ]
K s
max
S
where
max is the maximum growth rate, [ S ] is the substrate
concentration, and K s is the concentration at which
is growth,
max (Fig. 16.2).
The equation is in the same form as the Michealis-Menten equation. This
equation works well for single species in culture and moderately well for
phytoplankton assemblages. The actual physiological bases for K s and
1 2
max are complex and can vary over time and with nutrients, even within
single cells (Ferenci, 1999). Typical values for these two constants for ni-
trate, ammonium, and phosphate are presented in Table 16.1.
Nutrient concentration is a prime determinant of uptake, but other
factors, such as light, temperature, and metabolic characteristics, control
uptake rate as well. For example, low temperature decreases affinity for
limiting substrates (Nedwell, 1999). The greater energy requirement for
utilization of nitrate than that of ammonium under oxic conditions pro-
vides another example and was discussed in Chapter 13. The energy re-
quirement translates into a greater effect of light on nitrate uptake rates by
phytoplankton than ammonium (Fig. 16.4).
Nutrients can also interact. For example, ammonium inhibits nitrate
uptake (Fig. 16.4). This adaptation is advantageous because using nitrate
takes more energy, so using ammonium when it is available is an efficient
strategy. Similarly, energetically expensive nitrogen fixation will not occur
at high rates when nitrate or ammonium are plentiful.
Macrophytes have the ability to obtain nutrients from the sediments
through their roots in addition to using nutrients from the water column
(White and Hendricks, 2000). Uptake kinetics are less clear because nutri-
ent uptake from the water column can be important for some submerged
macrophytes, and partitioning water column uptake from that of the sed-
iments can be difficult. The relative importance of nutrient supply from
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