1. At what temperature the bottles for the BOD test are incubated?
a) 25 degree Celsius
b) 35 degree Celsius
c) 20 degree Celsius
d) 30 degree Celsius
Explanation: The bottles to be tested in order to calculate the amount of BOD present is kept at 20 degree Celsius. This is incubated for 5 days. This is done to estimate the ultimate BOD
2. What is the mathematical expression of BOD?
a) BOD = [(D1-D2)-(B1-B2)f]/P
b) BOD = [(D1-D2)-(B1-B2)f].
c) BOD = [(D1-D2) f]/P
d) BOD = [(D1-D2)-(B1-B2)]/P
Explanation: BOD = [(D1-D2)-(B1-B2) f]/P. Where D1 is the dissolved oxygen of the diluted sample right after the preparation. D2 is the Dissolved Oxygen of the sample after incubation.B1 is the Dissolved oxygen of the control before incubation. B2 is the dissolved oxygen of the control after incubation. F is the fraction of diluted water in the sample to the dilution of water in the control. P is the fraction of waste water sample volume to the total combined volume.
3. In terms of percentage how much BOD is oxidised in 5 days?
a) 90%
b) 70-90%
c) 60-70%
d) 50%
Explanation: In 5 days 60-70% BOD is oxidised. It takes around 20 days to oxidise the carbonaceous organic matter to 90-95%. The rate of oxidation is proportional to the amount of organic matter present in the water.
4. How is COD calculated?
a) Waste water is oxidised chemically using sodium in acid solutions
b) Waste water is oxidised chemically using dichromate in acid solutions
c) Waste water is oxidised chemically using bromine in acid solutions
d) Waste water is oxidised chemically using strontium in acid solutions
Explanation: Waste water is oxidised chemically using dichromate in acid solutions. High COD value indicates that the presence of inorganic compounds is high. Inorganic compounds get chemically oxidised and this results in the increase of organic compounds in the sample.
5. What is the ratio of BOD/COD in untreated waste?
a) 1-3
b) 0.3-0.8
c) 0.1-0.2
d) 3-5
Explanation: The ratio of BOD/COD is 0.3-0.8 in untreated waste. The ratio of BOD/TOC in untreated waste is 1.2-2. The ratio of BOD/COD after primary settling is 0.4-0.6.
6. What is the ratio of BOD/COD in the final effluent?
a) 0 8-1.2
b) 0.2-0.5
c) 0.1-0.3
d) 0.4-0.6
Explanation: The ratio of BOD/COD is 0.1-0.3 in the final effluent. The ratio of BOD/TOC in the final effluent is 0.2-0.5. The ratio of BOD/TOC from the primary settling tank is 0.8-1.2.
7. How is TSS calculated?
a) MPN
b) HPLC
c) Filtration
d) Mass spectrometer
Explanation: TSS is calculated by the filtration method. A filter paper is used to filter the water sample and the filtrate is then weighed. The amount of filtrate obtained is considered as the amount of TSS present.
8. Which of these is the used as the indicator when the titration is carried out to determine the amount of COD present in a sample.
a) Methyl Orange
b) Methyl blue
c) Ferroin
d) Phenolphthalein
Explanation: Ferroin is the indicator used while titration is carried out to determine the COD present in a water sample. The sample is titrated against ferrous ammonium sulphate. Titration is carried out until the solution turns to reddish brown.
9. Which of these is not a method to determine the number of colonies of bacteria present in a sample?
a) Multiple Tube fermentation
b) Pour and spread plate method
c) Membrane filter technique
d) Toxicity test
Explanation: Toxicity test is used to assess the environmental conditions of aquatic life. This is used to assess the effects of wastewater treatment methods. This is not used to determine the number of colonies of bacteria present in a water sample.
10. Which type of pump is used when the effluent should be pumped back into the plant for use as service water?
a) True
b) False
Explanation: Wastewater is the liquid end-product, or by-product, of municipal, agricultural, and industrial activity. As such, the chemical composition of wastewater naturally reflects the origin from which it came.