1. What is the temperature at which MPN test is performed?
a) 35oC
b) 37 oC
c) 40oC
d) 45 oC
Explanation: MPN test is performed at 37oC where different samples of water are mixed with lactose broth and incubated in test tubes for 48 hours.
2. Which of the following statement is/are correct regarding coliform bacteria?
i. It is gram negative
ii. It is rod shaped bacteria
iii. It is a harmless aerobic microorganism
a) i, ii, iii
b) ii, iii
c) i, iii
d) i, ii
Explanation: Coliform bacteria is a gram negative, rod shaped and harmless aerobic microorganism which is found in the intestine of warm blooded animals including human beings.
3. Which of the following is the disease caused by bacterial infections?
a) Amoebic dysentery
b) Infectious hepatitis
c) Typhoid fever
d) Poliomyelitis
Explanation: Amoebic dysentery is caused by protozoan infection, Infectious hepatitis and Poliomyelitis are caused by a viral infection and Typhoid fever is caused by a bacterial infection
4. The number of bacterial colonies by Agar plate count test should not exceed ____ per ml for potable water.
a) 1
b) 10
c) 100
d) 1000
Explanation: Agar plate count test is a test to count the number of bacterial colonies growing on a specified medium and the permissible limit for the number of bacterial colonies is 100 per ml
5. If the acid and gas are formed in the multiple tube fermentation technique, the test is _____
a) Positive
b) Continued
c) Negative
d) Discarded
Explanation: The acid and gas formation in the Multiple tube fermentation technique indicates that the test is positive and there are coliform bacteria in the sample
6. Which bacteria cause the reddish brown deposits in the tank?
a) Escherichia coli bacteria
b) Bacterium coli bacteria
c) Iron bacteria
d) Sulphur bacteria
Explanation: The growth of Iron bacteria causes the discoloration of tank due to reddish brown deposits and turbidity in water
7. Which bacteria results in the corrosion of iron and steel pipes embedded in soil?
a) Escherichia coli bacteria
b) Bacterium coli bacteria
c) Iron bacteria
d) Sulphur bacteria
Explanation: Sulphur bacteria cause the corrosion of iron and steel pipes embedded in soil. They are both aerobic and anaerobic and are more destructive in marshy or clay soils where anaerobic conditions prevails.
8. Gelatin liquefying bacteria are helpful in the manufacturing of photographic films.
a) True
b) False
Explanation: These bacteria are capable of producing proteolytic ferments that digest and liquefy gelatin. So, their presence in water is helpful in photographic films and glue industries
9. Which process of water treatment is done to avoid floating debris, branches, trees or other large particles suspended in water?
a) Screening
b) Aeration
c) Primary sedimentation
d) Secondary sedimentation
Explanation: Screens are used as a pretreatment process for purification of water to avoid large size suspended materials from water.
10. What is the size of the coarse screen used in pretreatment of water?
a) 25mm
b) 50mm
c) 75mm
d) 100mm
Explanation: Coarse screens are used in the form of bars of 25mm diameter size and are spaced at 75 to 100mm centers.