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Environmental Engineering MCQs | Environmental Engineering MCQS and Answers for competitive exams | set 6

101 The settling velocity of a particle in a sedimentation tank increases if
[A] Particle Size Is Decreased
[B] The Surface Area Of Tank Is Increased
[C] The Depth Of Tank Is Decreased
[D] None Of The Above
Answer: None Of The Above
102 The detention period in coagulation tanks is usually kept as
[A] 1 to 2 minutes
[B] 30 to 45 minutes
[C] 2 to 6 hours
[D] 2 to 6 days
Answer: 2 to 6 hours

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103 The alum, when added as a coagulant in water
[A] does not require alkalinity in water for flocculation
[B] does not affect pH value of water
[C] increases pH value of water
[D] decreases pH value of water
Answer: decreases pH value of water
104 In water treatment, rapid gravity filters are adopted to remove
[A] dissolved organic substances
[B] dissolved solids and dissolved gases
[C] floating solids and dissolved inorganic solids
[D] bacteria and colloidal solids
Answer: bacteria and colloidal solids
105 The rate of filtration in slow sand filters in million litres per day per hectare is about
[A] 50 to 60
[B] 100 to 150
[C] 500 to 600
[D] 1400 to 1500
Answer: 50 to 60
106 Assertion A: Slow sand filters are more efficient in removal of bacteria than rapid sand filters. Reason R : The sand used in slow sand filters is finer than that in rapid sand filters. Select your answer based on the coding system given below:
[A] Both A and R are true and R is the correct explanation of A
[B] Both A and R are true but R is not the correct explanation of A
[C] A is true but R is false
[D] A is false but R is true
Answer: Both A and R are true and R is the correct explanation of A
107 Air binding phenomena in rapid sand filters occur due to
[A] excessive negative head
[B] mud ball formation
[C] higher turbidity in the effluent
[D] low temperature
Answer: excessive negative head
108 The percentage of filtered water, which is used for backwashing in rapid sand filters, is about
[A] 0.2 to 0.4
[B] 0.4 to 1.0
[C] 2 to 4
[D] 5 to 7
Answer: 2 to 4
109 The rate of Alteration of pressure filters is
[A] less than that of slow sand filters
[B] in between the filtration rate of slow sand filters and rapid sand filters
[C] greater than that of rapid sand filters
[D] equal to that of slow sand filters
Answer: greater than that of rapid sand filters
110 The process in which the chlorination is done beyond the break point is known as
[A] Prechlorination
[B] Post Chlorination
[C] Super Chlorination
[D] Break Point Chlorination
Answer: Super Chlorination
111 The treatment of water with bleaching powder is known as
[A] prechlorination
[B] super chlorination
[C] dechlorination
[D] hypochlorination
Answer: hypochlorination
112 The suitable method for disinfection of swimming pool water is
[A] ultra violet rays treatment
[B] lime treatment
[C] by using potassium permanganate
[D] chlorination
Answer: ultra violet rays treatment
113 Which of the following chemical compounds can be used for dechlorination of water ?
[A] Carbon Dioxide
[B] Bleaching Powder
[C] Sulphur Dioxide
[D] Chloramines
Answer: Sulphur Dioxide
114 In lime-soda process
[A] only carbonate hardness is removed
[B] only non-carbonate hardness is re-moved
[C] lime reduces the carbonate hardness and soda-ash removes the non-carbo¬nate hardness
[D] lime reduces the non-carbonate hard-ness and soda-ash removes the carbo¬nate hardness
Answer: lime reduces the carbonate hardness and soda-ash removes the non-carbo¬nate hardness

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