A shallow pond in which the sewage is retained and biologically treated is called__________________?
(A) Oxidation
(B) Imhoff tank
(C) Lagoon
(D) Skimming tank
Suspended solid present in the waste water generated in blast furnace gas cooling and cleaning plant is removed by__________________?
(A) Biological oxygen pond
(B) Radial settling tank (thickener) using coagulant (lime & ferrous sulphate)
(C) Lagoons
(D) Filtration
Inhalation of silica dust causes a disease called__________________?
(A) Bronchitis
(B) Silicosis
(C) Pneumoconiosis
(D) None of these
Particles having diameter greater than 75 μm (micrometer = 10-6 mm) are called__________________?
(A) Grit
(B) Dust
(C) Powder
(D) Smoke
World environment day is observed every year on the 5th of___________________?
(A) June
(B) December
(C) July
(D) September
Foul odour and bad taste of water is removed by treating with__________________?
(A) Alum
(B) Bleaching powder
(C) Activated carbon
(D) Copper sulphate
Presence of a certain minimum quantity of fluorine is desirable in potable water to prevent___________________?
(A) Dental cavities
(B) Scale formation
(C) Water-borne disease
(D) Corrosion
Bacterial aerobic oxidation of polluted water in biological oxidation ponds is done to purify it. Presence of bacteria helps in____________________?
(A) Coagulation and flocculation of colloids
(B) Oxidation of carbonaceous matter to CO2
(C) Nitrification or oxidation of ammonia derived from breakdown of nitrogenous organic matter to the nitrite and eventually to the nitrate
(D) All
TLV of mercury in potable (drinking) water is about ______________ ppm?
(A) 0.001
(B) 0.1
(C) 1
(D) 5
Presence of iron and manganese in water causes___________________?
(A) Reduction in its dissolved oxygen content
(B) Discoloration of bathroom fixtures
(C) Temporary hardness
(D) None of these