5781. In water treatment, alum[Al2(SO₄)3] is used for the process of
Filtration
Coagulation
Sedimentation
Disinfection
✅ The correct answer is option B.
Chemical Engineering
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5782. Noise level during normal conversation among men is about __________ decibles.
10
45
90
115
✅ The correct answer is option B.
5783. Presence of nitrates in water in excess of 50 ppm causes
Mathenoglobenemia
Gastroentetitis
Asphyxiation
Tooth decay
✅ The correct answer is option A.
5784. Which of the following is a manmade source of air pollution?
Automobile exhaust
Forest fire
Bacterial action in soil and swamp areas
All of the above
✅ The correct answer is option A.
5785. Lagoons used for purification of polluted water
Are large shallow artificial lakes also known as clarification lakes, maturation ponds or oxidation ponds
Use micro-organisms/bacteria in presence of dissolved oxygen
Gives an excellent final effluent (with 3 to 4 lagoons arranged in series) having suspended solid < 1 mg/litre and BOD = 3.8 mg/litre
All of the above
✅ The correct answer is option D.
5786. Phenolic water generated in coke ovens & by-product plant attached to an integrated steel plant containing phenol in concentration of less than 100 mg/litre can be removed by
Chlorination
Treating in biological oxygen pond
Chemical coagulation
None of these
✅ The correct answer is option B.
5787. 80% less than 200 mesh size particles are called
Smoke
Powder
Grit
Aggregates
✅ The correct answer is option B.
5788. Dissolved oxygen content in river water is around __________ ppm.
5
100
250
500
✅ The correct answer is option A.
5789. Deaeration of high pressure boiler feed water is done to reduce
Foaming from boilers
Its dissolved oxygen content
Its silica content
Caustic embrittlement
✅ The correct answer is option B.
5790. Threshold limit value (TLV) i.e., the maximum permissible safe limit of phosgene gas which Hitler used to use to kill his enemies in ‘gas chamber’ is about __________ ppm.
<1
10-100
100-200
100-1000
✅ The correct answer is option A.