2.4.3. Effect of oxygen profile in pond water column on nitrification
rates
The calculation of N-conversions for both the bulk water and
biofilm were based on the Monod model (Fig. 1), with a half saturation
constant for the bulk water of 0.4 g m_3 of oxygen (Henze
et al., 2000). For algal-bacterial biofilms, the apparent half saturation
constant is not known, but likely to be higher than 0.4 due to
limitation by diffusion of oxygen into the biofilm. Zero and first order
kinetics were used (Fig. 1) in calculating N-conversions in the
biofilm. This is because results from previous studies (Babu et al.,
2010) indicated that the biofilm nitrification rates were not significantly
affected by bulk water oxygen concentration above
3.2 g m_3, below this value, the nitrification rates significantly reduced.
Therefore, it was assumed that nitrification rates above
depths at which oxygen was above 3.2 g m_3 was constant and
similar to that measured at 5 cm depth (Rmax). More details of
the calculation of the N-conversions by bulk water and biofilm
are discussed separately in the following sections.
2.4.3. Effect of oxygen profile in pond water column on nitrification
rates
The calculation of N-conversions for both the bulk water and
biofilm were based on the Monod model (Fig. 1), with a half saturation
constant for the bulk water of 0.4 g m_3 of oxygen (Henze
et al., 2000). For algal-bacterial biofilms, the apparent half saturation
constant is not known, but likely to be higher than 0.4 due to
limitation by diffusion of oxygen into the biofilm. Zero and first order
kinetics were used (Fig. 1) in calculating N-conversions in the
biofilm. This is because results from previous studies (Babu et al.,
2010) indicated that the biofilm nitrification rates were not significantly
affected by bulk water oxygen concentration above
3.2 g m_3, below this value, the nitrification rates significantly reduced.
Therefore, it was assumed that nitrification rates above
depths at which oxygen was above 3.2 g m_3 was constant and
similar to that measured at 5 cm depth (Rmax). More details of
the calculation of the N-conversions by bulk water and biofilm
are discussed separately in the following sections.
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