The amount of coagulant needed for coagulation of water increases with_______________?

A. 1) increase in turbidity of water
B. 2) decrease in turbidity of water
C. 3) increase in temperature of water
D. 4) decrease in temperature of water

The detention period in coagulation tanks is usually kept as_______________?

A. 1 to 2 minutes
B. 30 to 45 minutes
C. 2 to 6 hours
D. 2 to 6 days

The chemical most commonly used to increase speed of sedimentation of sewage is_______________?

A. Sulphuric acid
B. Copper sulphate
C. Lime
D. Sodium permanganate

The rate of filtration in slow sand filters in million litres per day per hectare is about_____________?

A. 50 to 60
B. 100 to 150
C. 500 to 600
D. 1400 to 1500

As compared to rapid sand filters, slow sand filters give______________?

A. 1) slower filtration rate
B. 2) higher filtration rate
C. 3) lesser efficiency in removal of bacteria
D. 4) higher efficiency in removal of bacteria

Air binding phenomena in rapid sand filters occur due to_________________?

A. Excessive negative head
B. Mud ball formation
C. Higher turbidity in the effluent
D. Low temperature

Cleaning is done by________________?

A. 1) scraping and removal in filters slow sand
B. 2) back washing in slow sand filters
C. 3) scraping and removal in filters rapid sand
D. 4) back washing in rapid sand filters

Period of cleaning of slow sand filters is about________________?

A. 24 – 48 hours
B. 10-12 days
C. 2-3 months
D. 1-2 year

Disinfection of water results in______________?

A. Removal of turbidity
B. Removal of hardness
C. Killing of disease bacteria
D. Complete sterilisation

Double filtration is used_______________?

A. To increase the filtration slow sand filters capacity of
B. To increase the filtration rapid sand filters capacity of
C. For isolated buildings like pools, hotels etc swimming
D. All of the above