Question 351. 1.  The process of aeration of treated water helps

Question 352. 4. Consider the following statements: Assertion A: The deposited sludge is removed from the bottom of settling tank Reason R: Due to decomposition of organic matter certain foul gases are evolved. Of these statements:

Question 353. 3. Consider the following statements:1. The average theoretical time required forthe water to flow through the settling tank is called detention period.2. The amount of raw water which passes through the settling tank without being detained forthe intended time is said to be short circuited.3. The flowing through period is always more than the detention period.4. Displacement efficiency is the ratio of detention time and flow through time. Of these statements:

Question 354. 2.  Consider the following statements regarding the sedimentation tanks.1. The detention time ranges between 4 to 8 hours for plain sedimentation2. The width of the tankis normally kept 10m to 12m.3. The horizontal flow velocity in sedimentation tank is generally kept 0.3 mJminute.4. The total flow from the tank in 24 hours is kept equal to maximum daily demand. Of these statements:

Question 355. 5.  Consider the following statements regarding sedimentation aided with coagualation.1. When certain chemical compounds called coagulants are added to thewater containing very fine suspended mud particles, a gelatenous precipitate called 'floc' is formed. 2. The very fine mud particles and colloidal matter get attracted to the flocs and form the bigger sized floculated particles. 3. The coagulation is done in sedimentation tank where floculated particles settle down. 4. Coagulants are used if water turbidity is more than 30 mg per litre. Of these statements:

Question 356. 7.  Consider the following statements regarding the working of coagulation sedimentation plant. 1. Mixing the chemical coagulant. 2. Agitating the mixture of chemical coagulant and raw water3. Consolidation of flocin fioculation tank4. Allowing the flocculated water to enter into sedimentation tank. The correct sequence of operation is

Question 357. 6.  Consider the following statemetns regarding coagulant (iron salt), 1. They remove much more suspended matter than the alum 2. They remove hydrogen sulphide and also its taste and odour 3. They have a limited range of pH values 4. They do not impart corrosiveness to water. Of these statements

Question 358. 9. Consider the following statements regarding mixing basins provided with mechanical device. 1. The inlet for raw water is kept at lower level than of outlet to fiocculator 2. Lower end ofdeflecting wallis kept at the level of the centre of impeller 3. The wetcoagulant is discharged just under the rotating impeller 4. Drain valve for sludge removal is provided in the mixing tank wall. Of these Statements:

Question 359. 8.  Consider the following statements regarding the coagulation sedimentation plant. 1, Chemical coagulant is fed into raw water in powdered form 2. Water from coagulation sedimentation plants fed into rapid gravity filters 3. Due to coagulation sedimenation lentadities are reduced to as low values as10-20 mg/F 4. Due to coagulation sedimentation the bacterias are removed and the B-coli index is reducedby 70%. Of these statements:

Question 360. 2.  Consider the following statements regarding the cleaning of the slow sand filters. Assertion A: The effluents obtained just after each cleaning of the slow sand filter is not fit for human consumption Reason R: There is no filter on the top of the sand layer to arrest in impurities around the sand grains.