Page 453 - Civil Engineering Formulas

STORMWATER, WASTEWATER, AND ENVIRONMENTAL PROTECTION 379

where P volatile solids produced, lb/d (kg/d)
x
Y yield coefficient (lb VSS/lb BOD )
L
–1
k endogenous coefficient (d )
d
mean cell residence time (d)
c
The volume of methane gas produced at standard conditions (32°F and 1 atm)
(0°C and 101.3 kPa) is calculated using
3
5.62 ft /lb[(BOD in , lb/d) (BOD out , lb/d) 1.42P x ] (13.72)
V CH 4
3
3
volume of methane gas produced at standard conditions (ft /d) (m /d).
where V CH 4
Percent stabilization is calculated using
[(BOD in , lb/d) (BOD out , lb/d) 1.42 P x ]
% Stabilization 100
BOD in , lb/d
(13.73)

DESIGN OF A CHLORINATION SYSTEM
FOR WASTEWATER DISINFECTION

The reduction of coliform organisms in treated effluent is defined by
N t 3
(1 0.23C t t) (13.74)
N 0
where N number of coliform organisms at time t
t
N number of coliform organisms at time t 0
0
C total chlorine residual at time t (mg/L)
t
t residence time (min)
The required residual, R is
R
R R C t t/t (13.75)
Codes often require a residence time, t, of 15 min. However, the local code
should be checked to determine the exact residence time currently required.
The capacity of the chlorinator at peak flow
Cl (lb/d) (Dosage, mg/L)(Avg flow, Mgd)(P.F.)(8.34) (13.76)
2
where Cl pounds of chlorine required per day (kg/d)
2
Dosage dosage used to obtain coliform reduction
Avg. Flow average flow
P.F. peaking factor for average flow
8.34 8.34 lb . L/Mgal . mg