Question: Which one of the following statements is correct ?

• 1. During the day, earth reflects solar radiation
• 2. During the day, earth reflects both solar radiations the emission from its surface
• 3. During the night, earth emits radiation from its surface
• 4. All of these

Question: Pick up the correct statement from the following?

• 1. Phytoplankton contains photosynthetically active pigment
• 2. An increase of phytoplankton increases the back scattering in the green region
• 3. An increase of phytoplankton absorbs the bule region rapidly
• 4. An increase of phytoplankton decreases the back scattering in the green region

Question: For the COD test of sewage, organic matter is oxidised by K2Cr2O7 in the presence of________________?

• 1. H2SO4
• 2. HNO3
• 3. HCl
• 4. None of these

Question: The reduced levels of the string at the consecutive sight rails A and B are 203.575 m, 203.475 m respectively. If the difference of their R.D.s is 10 m, the gradient of the sewer line is_________________?

• 1. 1 in 100 upward
• 2. 1 in 500 upward
• 3. 1 in 100 downward
• 4. 1 in 503 upward

Question: Dilution method of disposing of sewage, is not preferred to_______________?

• 1. When sewage is fresh
• 2. When diluting water has high dissolved oxygen content
• 3. When diluting water is used for water supply near the point of sewage disposed
• 4. When the diluting water is having flow currents

Question: Imhoff cone is used to measure________________?

• 1. Total organic solids
• 2. Total solids
• 3. Total in organic solids
• 4. Settleable solids

Question: The grit and silt of the grit chambers, may not be used for_________________?

• 1. Raising low lying areas by dumping
• 2. Concreting
• 3. Both A and B
• 4. Neither A nor B

Question: If the diameter of a sewer is 150 mm, the gradient required for generating self cleansing velocity, is________________?

• 1. 1 in 60
• 2. 1 in 100
• 3. 1 in 120
• 4. None of these

Question: The sewage treatment units in which anaerobic decomposition of organic matter is used, are called________________?

• 1. Imhoff tanks
• 2. Trickling filters
• 3. Sludge sedimentation tanks
• 4. None of these

Question: If the flame of a miner’s safety lamp in a manhole extinguishes within 5 minutes, the sewer certainly contains_______________?

• 1. Hydrogen sulphide
• 2. Carbon dioxide
• 3. Methane
• 4. Oxygen