1. When huge amount of sewage is dumped in a river, the BOD will be
a) decrease
b) increase
c) remain unchanged
d) none of these
2. BOD values are always less than
a) DO value
b) MPN value
c) SPC value
d) COD value
3.The optimum DO in natural water is---
a) 3-5 ppm
b) 4-6 ppm
c) 5-7ppm
d) 6-8ppm
4. Very low BOD level of a water body indicates that the water is ---
a) less polluted
b) highly polluted
c) contain more organic matter
d) rich in heavy metals
5. If the depletion of oxygen is
found to be 2mg/l after incubating 3ml of sewage diluted to 300 ml, at 20ºC for 5 days, then
the BOD5 of the sewage would be:
a) 100mg/l
b) 200mg/l
c) 300mg/l
d) None of these
6. As per the Central Pollution
Control Board of India, Biological Oxygen Demand (BOD) of treated sewage should
be
a) less than 35 mg/l
b) less than 25 mg/l
c) less than 20 mg/l
d) less
than 10 mg/l
7. While testing for COD of sewage,
organic matter is oxidised by K2Cr2O7
a) HCl
b) H2SO4
c) HNO3
d) None of these
8. High COD to BOD ratio of an
organic pollutant represents:
a) High biodegradability of the
pollutant
b) Low
biodegradability of the pollutant
c) Presence of free oxygen for
aerobic decomposition
d) Presence of toxic material in
the pollutant
9. Standard 5-day BOD
at 20ºC, when compared to ultimate BOD is about:
a) 58%
b) 68%
c) 98%
d)None of these
10. The organic load of the water body can be expressed in terms of BOD, which refers to
a) The degree of microbially mediated oxygen consumption in water
b) The degree of chemically mediated oxygen consumption in water
c) The total organic carbon content in water
d)The total dissolved in water
11. The clean water should have BOD value
a) less than 5mg/L
b) 10mg/L
c) 20mg/L
d) 40mg/L
Answer:
1. b) increase
2. d) COD value
3. b) 4-6 ppm
4. a) less polluted
5. b) 200mg/l
6. d) less than 10 mg/l
7. b) H2SO4
8. b) Low biodegradability of the pollutant
9. b) 68%
10. a) The degree of microbially mediated oxygen consumption in water
11.a) less than 5mg/L
