Environmental Engineering in CE
The ratio of oxygen available to the oxygen required for stabilisation of sewage is called the

Oxygen ion concentration
Relative stability
Biological oxygen demand (BOD)
Bacterial stability factor

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Environmental Engineering in CE
Lagoons used for purification of polluted water

Use micro-organisms/bacteria in presence of dissolved oxygen
Gives an excellent final effluent (with 3 to 4 lagoons arranged in series) having suspended solid < 1 mg/litre and BOD = 3.8 mg/litre
All of these
Are large shallow artificial lakes also known as clarification lakes, maturation ponds or oxidation ponds

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