CIVIL ENGINEERING FORMULAS

STORMWATER, WASTEWATER, AND ENVIRONMENTAL PROTECTION 379

wherePxvolatile solids produced, lb/d (kg/d)
Yyield coefficient (lb VSS/lb BODL)
kdendogenous coefficient (d–1)

(^) cmean cell residence time (d)
The volume of methane gas produced at standard conditions (32°F and 1 atm)
(0°C and 101.3 kPa) is calculated using

(13.72)

where volume of methane gas produced at standard conditions (ft^3 /d) (m^3 /d).

Percent stabilization is calculated using

(13.73)

DESIGN OF A CHLORINATION SYSTEM
FOR WASTEWATER DISINFECTION

The reduction of coliform organisms in treated effluent is defined by

(13.74)

whereNtnumber of coliform organisms at time t
N 0 number of coliform organisms at time t 0
Cttotal chlorine residual at time t(mg/L)
tresidence time (min)

The required residual, RRis

(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 2 (lb/d)(Dosage, mg/L)(Avg flow, Mgd)(P.F.)(8.34) (13.76)

where Cl 2 pounds of chlorine required per day (kg/d)
Dosagedosage used to obtain coliform reduction
Avg. Flow average flow
P.F.peaking factor for average flow
8.348.34 lb.L/Mgal.mg

RRCtt/t

Nt

N 0

(10.23Ctt)^3

% Stabilization

[(BODin, lb/d)(BODout, lb/d)1.42Px]

BODin, lb/d

 100

VCH 4

VCH 4 5.62 ft^3 /lb[(BODin, lb/d)(BODout, lb/d)1.42Px]