1. The slow sand filter is able to remove ______ % of bacteria in water.
a) 90
b) 95
c) 98-99
d) 100
Explanation: The slow sand filters are highly efficient in the removal of bacteria and can remove around 98-99% of bacteria present in water.
2. The slow sand filter is efficient in removing turbidity of water.
a) True
b) False
Explanation: The slow sand filter is not efficient in removing turbidity of water and is not capable of removing turbidity over 50ppm.
3. The maximum daily demand of a city is 24*105 and the rate of filtration is 100 per litre per hour per m2. What is the area of the filter?
a) 10
b) 100
c) 1000
d) 1500
Explanation: Maximum daily demand = 24*105
Rate of filtration = 100
Area of filter=Maximum daily demand/Rate of filtration=24*105/(100*24)
=1000m2.
4. The slow sand filter is designed for _____________
a) Maximum daily demand
b) Maximum yearly demand
c) Average daily demand
d) Maximum weekly demand
Explanation: The slow sand filter is designed for maximum daily demand, which is 1.8 times the average daily demand.
5. What is the frequency of cleaning of a slow sand filter?
a) 1 week
b) 1-3 months
c) 2-3 days
d) 2-3 weeks
Explanation: The slow sand filter requires cleaning, depending upon the impurities present in water and normally it is done after 1-3 months.
6. What is the maximum filter head up to which slow sand filters are worked upon?
a) 25cm
b) 50cm
c) 75cm
d) 100cm
Explanation: Initially the filter head is only 10-15cm but it increases as suspended matter is arrested. When the filtration head reaches the maximum permissible value of 75cm, the filter requires cleaning.
7. The depth of an enclosed tank of a rapid sand filter lies in the range of ______
a) 1-2m
b) 2.5-3.5m
c) 2-5m
d) 3-5m
Explanation: The depth of an enclosed tank of a rapid sand filter lies in the range of 2.5-3.5m and its surface area lies between 20-50m2.
8. The effective size of a rapid sand filter is ______
a) 0.45mm
b) 0.7mm
c) 0.8mm
d) 0.9mm
Explanation: The effective size of a rapid sand filter lies in the range of 0.35-0.6mm and its common value is 0.45mm
9. The finer the suspended impurities to be removed ___________
a) Larger will be the sand size
b) Smaller will be the sand size
c) Smaller will be the surface area of sand grains
d) Narrow will be the sand depth of the bed
Explanation: The finer the suspended impurities to be removed, smaller will be the sand size in order to increase the surface area of sand grains in the sand bed
10. What is the value of the uniformity coefficient in a rapid sand filter?
a) 1
b) 1.5
c) 2
d) 2.5
Explanation: The value of uniformity coefficient in a rapid sand filter lies between 1.2 and 1.7 and its common value is 1.5.