Geoscience Reference
In-Depth Information
QS
o
-
QS
-
kSV
= 0
(24.83)
Rearranged:
S
S
1
1(
Effluent BOD
Influent BOD
=
=
(24.84)
+
k VIQ
)
o
1
=
(24.85)
1
+
k
θ
where
Q
= Wastewater flow (m
3
/day, MGD).
S
o
= Influent BOD concentration (mg/L).
S
= Effluent BOD concentration (mg/L).
k
= Overall first-order BOD removal rate (per day).
θ = Hydrauslic retention time.
The temperature in the aerated pond resulting from the influent wastewater temperature, air
temperature, surface area, and flow can be computed using the following equation (Mancini and
Barnhart, 1968):
(
)
−=
−
TTfA
Q
wa
TT
(24.86)
i
w
where
T
i
= Influent wastewater temperature (°C, °F).
T
w
= Lagoon water temperature (°C, °F).
T
a
= Ambient air temperature (°C, °F).
f
= Proportionality factor = 12 × 10
-6
(British system) or 0.5 (SI units).
A
= Surface area of lagoon (m
2
, ft
2
).
Q
= Wastewater flow (m
3
/day, MGD).
Using Equation 24.86 rearranged, the pond water temperature is
AfTQT
Af
+
+
a
i
T
=
(24.87)
w
Q
24.10 CHEMICAL DOSAGE
*
Chemicals are used extensively in wastewater and water treatment operations. Plant operators add
chemicals to various unit processes for slime-growth control, corrosion control, odor control, grease
removal, BOD reduction, pH control, sludge-bulking control, ammonia oxidation, and bacterial
reduction, among other reasons. To apply any chemical dose correctly it is important to be able
to make certain dosage calculations. One of the most frequently used calculations in wastewater
mathematics is the dosage or loading. The general types of mg/L to lb/day or lb calculations are for
chemical dosage, BOD, chemical oxygen demand (COD), suspended solids (SS) loading/removal,
pounds of solids under aeration, and waste activated sludge (WAS) pumping rate. These calcula-
tions are usually made using either of the following equations:
*
In Chapter 23, we discussed calculations relative to the chlorination process used to treat potable water. Similar
information appears here.
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