MIL-HDBK-1005/16
(n/KT)[(So/Se)1/n -1]
EQUATION: t
=
(1)
where
t
=
Total hydraulic detention time (d). Divide
T equally among number of aerated basins.
N
=
Number of aerated basins operated in series.
KT
=
First order reaction rate at operating lagoon
temperature (d-1)
So
=
Influent total BOD (mg/L).
Se
=
Effluent dissolved BOD (mg/L).
Determine rate constant from data for actual or similar
wastes and operating conditions. If this is not practical, use
K = 2.5/d for normal domestic wastewater at 20 C (K20). Adjust
K20 to expected operating lagoon temperature using Equations (2)
and (3).
Increasing the number of ponds in series (n) decreases
the required total detention time (t).
b) Lagoon Temperature. Lagoon temperature is affected
by the influent waste and ambient air temperature, basin
geometry, and mixing conditions. The equilibrium temperature can
be approximated by Equation 2.
A f Ta + Q Ti
EQUATION: Tw
=
--------------------------
(2)
Af+Q
Lagoon waste temperature, F (C)
where
Tw
=
A
=
Surface area, sq ft (sq m)
Ambient air temperature, F (C)
Ta
=
Influent waste temperature, F (C)
Ti
=
Q
=
Wastewater flow rate, gpd (Lpd)
f
=
Proportionality factor 12 (500)
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