Disposal of Sewage Effluent | Environmental Engineering - Civil Engineering (CE) PDF Download

Introduction

Standards of Dilution for Discharge of Wastewaters into Rivers

• Standards of Dilution based on Royal Commission Report
  
• BIS Standards for Discharge of Sewage and Industrial Effluents in Surface Water Sources and Pub
  
• General standards for Discharge of Environment Pollutants from effluents into Surface Water Sources, Public Sewers, and Marine Coasts Under Environment (Protection) Rules, 1986
  

Dilution and Dispersion

Where,
C_s = The concentration of sewage in mg/lit.
Q_s = A flow rate of sewage in m3/sec or lit/sec.
C_R = The concentration of the river in mg/lit.
Q_R = Flow rate (discharge in m3/sec or lit/sec.
C_mix = The concentration of the mixture.

Zone of Pollution in River Stream

Saturation D.O at 20^oC → 9.2 mg/lit.
Saturation D.O at 30^oC → 7.6 mg/lit.
Saturation D.O at 0^oC → 14.6 mg/lit.

ab = cd

Where,
TOD = Theoretical oxygen demand
BOD = Biological oxygen demand
COD = Chemical oxygen demand
(BOD)_u = Ultimate BOD (Y_u)

Stretcher-Phelps Equation

Where,
D_t = D.O deficit in mg/lit after t days.
L = Ultimate first stage BOD of the mix at a point of waste discharge in mg/lit.
D_o = Initial oxygen deficit of the mix at the mixing point in mg/lit.
k_R = Reoxygenation constant
k_D = Deoxygenation constant
f = Self-purification constant
t_C = Critical time at which minimum dissolved oxygen occurs i.e.

D_C = Critical maximum oxygen deficit.