A. Chemical oxygen demand (COD) is a measure of chemically oxidisable organic matter present
in water
B. COD is determined by oxidising the organic matter present in water with potassium
dichromate in cone, sulphuric acid solution at boiling temperature for specified time
C. COD is related to BOD of a given waste in water but the relationship varies for different
wastes. Typically COD of potable water may be 1-2 mg/litre
D. All A., B. and C.
Related Mcqs:
- Pick out the wrong statement ?
A. The concentric layer in atmosphere which contains about 70% of the total mass of atmosphere
and characterised by a steady decrease in temperature is called stratosphere
B. Stratosphere is rich in ozone and is located just above the troposphere
C. Troposphere is a turbulent dusty zone containing much of water vapor and clouds
D. The earth’s atmosphere is an envelope of gases extending upto a height of about 200 kms - Pick out the wrong statement pertaining to ‘green house’ for the plants ?
A. ‘Green house’ (made of glass) allows visible sunlight (i.e., short wavelength solar radiation
like ultra-violet rays) to pass through the glass and heat up the soil thereby warming up plants
inside it
B. The emitted longer wavelength radiation (e.g., infrared) is partly reflected and partly absorbed
by the glass of the green house
C. ‘Green house effect’ in earth’s atmosphere is due to increasing CO2 level in atmosphere, where
CO2 acts like the glass of ‘green house’ thereby warming up the earth’s surface
D. ‘Green house’ is colder than the outside atmosphere - Pick out the wrong statement. A. Caustic embrittlement of boiler’s metallic parts is caused by high concentration of caustic soda in boiler feed water___________________?
B. Cooling and freezing of water kills the bacteria present in it
C. With increasing boiler operating pressure of steam, the maximum allowable concentration of
silica in feed water goes on decreasing
D. Dissolved oxygen content in high pressure boiler feed water should be nil - Pick out the one which is not a chemical coagulant ?
A. Aluminium sulphate
B. Ferrous sulphate
C. Hydrated lime
D. Chloramine - In water treatment plant, zeolite process is used to remove the _____________ of water?
A. Acidity
B. Alkalinity
C. Hardness
D. Iron & zinc - Which of the following is a manmade source of air pollution ?
A. Automobile exhaust
B. Forest fire
C. Bacterial action in soil and swamp areas
D. All A., B. and C. - Most efficient and suitable dust removal equipment for removal of fly-ash from flue gas in a thermal power plant is the__________________?
A. Gravity settling chamber
B. Cyclone separator
C. Electrostatic precipitator
D. Bag filter - Presence of a certain minimum quantity of fluorine is desirable in potable water to prevent___________________?
A. Dental cavities
B. Scale formation
C. Water-borne disease
D. Corrosion - Scale formation in boiler is controlled by____________________?
A. Preheating of feed water
B. Reduction in hardness, silica & alumina in feed water
C. Keeping the pH value of feed water just below 7
D. Eliminating H2S in feed water - In a sedimentation tank, the detention period for water ranges from _____________ hours?
A. 2 to 4
B. 8 to 12
C. 16 to 20
D. 24 to 32
