Organic Waste Recycling

Land treatment of wastewater 429

Example 8.6

A wastewater has the same characteristics as in Example 8.5. Design an OF
system to treat this wastewater so that the treated effluent contains BOD 5 and
fecal coliforms less than 50 mg/L and 100 no./100 mL, respectively. The
application rate is 0.1 m^3 /(hr-m width).

The following information are given

C - 5 0.02 z

For BOD 5 removal = 0.72 exp (- )

Co q0.5

N

For fecal coliform removal = exp ( - Kf.t)

No

Where:

N and No= effluent and influent fecal coliform concentration, no./100 mL

Kf = fecal coliform removal rate in OF, 0.2/min

t = time of wastewater flow in OF

1

v = R2/3S1/2

n

Where:

v = flow velocity of wastewater during OF treatment, m/sec

R = hydraulic radius of flow, m

S = slope of soil = 0.02

n = coefficient of roughness = 0.38

For BOD 5 removal

50 - 5 0.02 z

( ) = 0.72 exp (- )

250 0.10.5

Slope length, z = 22 m for BOD 5 removal