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Chapter 6
SLUDGE DISPOSAL, EFFLUENT DISCHARGE STANDARD
Sludge and its moisture content: The moisture content of sludge is defined as volume of water present in sludge to the volume of sludge.
Actually instead of volume we should use mass but the density of sludge is approximately 1gm/cc so we used volume.
Let volume of solids is 1. Initially moisture content is p_{1} % and it reduced to p_{2} . Let volume of water at initial stage is x and it reduced to y
100x = P_{1} + P_{1}x 100 y = P_{2} + P_{2}y
x[100  p_{1}]= P_{1}
y[100  p_{2}]= p_{2}
and
Dilution and dispersion: C_{s} = Sweage concentration
C_{R} = River concentration
Q_{S} = Sewage discharge
Q_{R} = river discharge
C = Combined concentration
Zones of pollution in a river stream :
1. Zone od degradation
2. Zone of active decomposition
3. Zone of recovery
4. Zone of clear water
Oxygen deficit: The oxygen deficit 'D' at any time in a polluted river stream is te difference between the actual DO content of water at that time and saturation DO content at the water temperature.
Oxygen deficit D = Saturation DO  Actual DO
DO
time
StreeterPhelps equation:
Integration factor
Separating variables and integrate
At t = 0, D = D_{0}
Critical time: the time at which critical deficit.
At critical time
Putting t_{c }value we get
Where
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