7819

• UCREFRP Catalog Number: 7819
• Author: Many
• Title: Journal of Applied Aquaculture
• USFW Year: 1992
• USFW - Doc Type: 1‎(3)‎
• Copyright Material: YES

Pa!!er 11
Retention time is a function of flow rate, biofilter volume, and
voids fraction of the medium:
M = F (6)
where V =the empty bed biofilter volume (measured in liters) and
S =the voids fraction of the biofilter medium. Only that portion of
the biofilter bed that holds medium should be included in V. Note
that biofilter volume can be expressed as the product of the biofilter
cross-sectional area (X) and depth (D).
Because retention time is a function of biofilter dimensions and
flow rate, Equation 5 can be rewritten to accommodate changes in
biofilter depth, cross sectional area, and flow rate:
Z = C - C (1 - R)(xUSIF)NxrDrsr/Fr) (7)
where X =new biofilter cross-sectional area, Xr =original cross-
sectionalarea (i.e.,cross-sectional area at which R was determined),
D =new biofilter depth, Dr =original biofilter depth, S =new
voids fraction, Sr =the original voids fraction, F =new flow rate
through the biofilter (l/minute), and Fr =original flow rate through
the biofilter. Note that the exponent will be equal to unity if none of
these parameters is changed. Depth and cross-sectional area can be
measured in any units as long as these units are used consistently.
Combining equations 1 and 7 and solving for B (fish biomass)
yields:
F (C-C (1- R} «xns/Fu~xrDrsr/Fr)) }
~ _ (g)
A
If the nitrification rate at the temperature at which R was deter-
mined is Nr and the nitrification rate at a new temperature is N, the
difference in nitrification rate is proportional to N/Nr. Ammonia
removal (R) can be adjusted for a change in nitrification resulting
from a change in temperature by multiplying R times N/Nr. The
proportion N/Nr can be derived from the equation of Liao et al.
(1972) for temperatures of 1.7 to l2°C: