ity constant must first be adjusted for both the temperature of the wastewater and the
depth of the actual filter.
Adjustment for temperature. The treatability constant is first adjusted from the given
standard at 2O^0 C (68^0 F) to the actual wastewater temperature of 3O^0 C (86^0 F) using the
following equation:
^30/2O = £20/20 0 r~^2 °where ^ 30720 = Treatability constant at 3O
0
C (86
0
F) and 20 foot (6.1 m) filter depth
Ar 20720 = Treatability constant at 2O^0 C (68^0 F) and 20 foot (6.1 m) filter depth
6 = Temperature activity coefficient (assume 1.035)
T = Wastewater temperature
Using above values:
£30/20 = (0.075 (gal/min)^0 VfF)(1.035)^30 -^20 = 0.106 (gal/min)^0 5 /ft^2Adjustment for depth. The treatability constant is then adjusted from the standard depth of
20 feet (6.1 m) to the actual filter depth of 25 feet (7.6 m) using the following equation:
£30/25 = £30/20(^1/^2)*where & 30725 = Treatability constant at 3O^0 C (86^0 F) and 25 foot (7.6 m) filter depth
£30/20 = Treatability constant at 3O
0
C (86
0
F) and 20 foot (6.1 m) filter depth
D 1 = Depth of reference filter (20 feet) (6.1 m)
D 2 = Depth of actual filter (25 feet) (7.6 m)
jc = Empirical constant (0.3 for plastic medium filters)
Using above values:
£30/25 = (0.106 (gal/mm)^0 -^5 /ft^2 )(20/25)°-^3
= 0.099 (gal/min)^0 5 /ft^2 (0.099 (L/s)°^5 /m^2 )- Size the plastic media trickling filter
The empirical formula used for sizing plastic media trickling filters is
^=exphftD(a,n
^iwhere Se = BOD 5 of settled effluent from trickling filter (mg/L)
S 1 = BOD 5 of influent wastewater to trickling filter (mg/L)
& 20 = Treatability constant adjusted for wastewater temperature and filter depth =
(£30/25)
D= Depth of filter (ft)
Qv = Volumetric flowrate applied per unit of filter area (gal/min-ft^2 ) (L/s-m^2 ) =
QIA
Q = Flowrate applied to filter without recirculation (gal/min) (L/s)
A= Area of filter (ft^2 ) (m^2 )
n = Empirical constant (usually 0.5)Rearranging and solving for the trickling filter area (A):