Question 361. 1.  Consider the correct statements regarding the quantities of sand used for filtration.1. Free from dirt and other impurities 2. Uniform size 3. Soft and collective 4. It looses at least 10 % of its weight when immersed in hydrochloric acid for 24 hours. Of these statements:

Question 362. 0. Consider the following statements regarding sedimentation tank. 1. Raw water is screened for removal oflarge organic impurities 2. Raw water is passed through coagulation-sedimentation plant 3. Raw water is passed through rapid gravity filters 4. Cleaned water is disinfected for killing of germs and colour removal. The correct sequence of operation is:

Question 363. 4. Considere the following statements regarding rapid gravity filters.1. It was developed by G.W. Fuller2. It makes use of very fine sand3. Its yield is 30 times more than slow sand filters4. The fuktered water is treated with disinfectant. Of these statements:

Question 364. 3. Consider the following statements regarding the efficiency of the slow sand filters.1. These are not efficient in removing bacterias.2. These are highly efficent in removing suspended solids3. These remove the odours and tastes causedby the organic impurities4. These are more suitable forsedimented waters haviing turbidities greater than 50 to 60 mg/l.Of these statements:

Question 365. 5. Consider the following statements regarding double filtration.1. The rate of filtration of slow sand filters can be considerably increased by using a roughening filter2. The raw water is first of all passed through slow sand filters3. The roughening filter is rapid gravity filter in which finer sands is used compared to ordinary rapid gravity filters.4. The roughening filter reduces the loadon the slow sand filter and thus increases the filtration rate. Of these statements:

Question 366. 2. Consider the following statements regarding double filtration.1. The rate of filtration of slow sand filters can be considerably increased by using a roughening filter2. The raw water is first of all passed through slow sand filters3. The roughening filter is rapid gravity filter in which finer sands is used compared to ordinary rapid gravity filters.4. The roughening filter reduces the loadon the slow sand filter and thus increases the filtration rate. Of these statements: