A. Natural aeration of water stream
B. Photosynthetic action of algae
C. Both A. & B.
D. Neither A. nor B.
Related Mcqs:
- The amount of chemical coagulant added for treatment of polluted water ______________ with increase in temperature of the polluted water to be treated?
A. Decreases
B. Increases
C. Remain constant
D. May increase or decrease; depends on the chemical characteristics of polluted water - A butane isomerisation process produces 70 k.mole/hr of pure iso-butane. A purge stream removed continuously, contains 85% n-butane and 15% impurity (mole%). The feed stream is n-butane containing 1% impurity (mole%). The flow rate of the purge stream will be_________________?
A. 3 kmole/hr
B. 4 kmole/hr
C. 5 kmole/hr
D. 6 kmole/hr - Thermal pollution of water increases its toxicity and oxidation of oxygen demanding waste besides favouring bacterial growth. A rise in water temperature by 10°C, doubles the toxic effects of _____________ present in it?
A. Coal ash
B. Potassium cyanide
C. Ortho-xylene
D. None of these - Waste/polluted water discharged from electroplating, blast furnace and coal mining industries contain mainly _____________ substances?
A. Radioactive
B. Organic
C. Inorganic
D. None of these - Which of the following is the most efficient for removal of very finely divided suspended solids and colloidal matter from the polluted water stream ?
A. Sedimentation tank
B. Circular clarifier
C. Mechanical flocculation
D. Chemical coagulation - Pure oxygen is mixed with air to produce an enriched air containing 50 volume % of oxygen. The ratio of moles of air to oxygen used is_________________?
A. 1.72
B. 0.58
C. 0.5
D. 0.2 - Radioactive substances present in the polluted water stream can be removed by_________________?
A. Biological oxygen treatment
B. Coagulation and filtration
C. Adsorption in ion exchange materials
D. None of these - Dissolved oxygen content in river water is around _____________ ppm?
A. 5
B. 100
C. 250
D. 500 - For existence of aquatic life in water, the dissolved oxygen content in it, should not be less than ______________ ppm?
A. 10000
B. 5
C. 500
D. 1000 - What fraction of the total pressure is exerted by oxygen, if equal weights of oxygen and methane are mixed in an empty vessel at 25°C ?
A. 2/3
B. 1/3
C. 1/2
D. 1/3 × (298/273)
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