MIL-HDBK-1005/16
for continuous year-round use should be restricted to areas where
the visible solar radiation is greater than 1.0 million calories
per square meter per day (cal/sq m/d) 90 percent of the time and
where freezing conditions never persist for an extended time.
7.5.1
Sizing Basis
7.5.1.1
Loading. BOD removal for settled sewage (primary
effluent) by an aerobic lagoon can be determined using
Equation 4. The equation appears first in English, then in
international system (SI) units.
EQUATION: ∆BOD
=
21.872
[ln (Io/24)]
(4)
d
∆BOD
=
6.66
[ln (Io/258)]
d
∆BOD
where
=
BOD removed by lagoon (mg/L)
lagoon mid-depth (≤1.5 feet [≤0.5 m])
d
=
Io
=
light intensity at lagoon surface
(footcandles [lux])
Term Io is determined by the method of Oswald and
Gotaas, Photosynthesis in Sewage Treatment, ASCE, 1957. In the
absence of necessary solar radiation data, determine the total
required lagoon volume based on a BOD surface loading rate of
60 (subtropical) to 120 (tropical) lb/day/acre (67 [subtropical]
to 134 [tropical] kg/day/ha). Proportion total required volume
equally among multiple lagoons in series or parallel operation.
7.5.1.2
Depth. Operating depth should be 1 to 2 feet (0.3 to
0.6 m) and should not exceed 3 feet (0.91 m) to ensure light
penetration and photosynthetic activity for the full depth of the
lagoon.
7.5.1.3
Applications. Refer to EPA-625/1-83-015 for further
discussion of aerobic and nondischarging lagoons and application
of design equations.
a)
Location.
Refer to par. 7.3.2.
b)
Exposure.
Refer to par. 7.3.3.
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