Environmental Engineering in CE
Cleaning is done by(i) Scraping and removal in filters slow sand(ii) Back washing in slow sand filters(iii) Scraping and removal in filters rapid sand(iv) Back washing in rapid sand filtersThe correct answer is

(ii) and (iii)
(i) and (iv)
(i) and (ii)
(ii) and (iv)

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Environmental Engineering in CE
Bacterial aerobic oxidation of polluted water in biological oxidation ponds is done to purify it. Presence of bacteria helps in

Nitrification or oxidation of ammonia derived from breakdown of nitrogeneous organic matter to the nitrite and eventually to the nitrate
All of these
Coagulation and flocculation of colloids
Oxidation of carbonaceous matter to CO₂

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Environmental Engineering in CE
On prolonged exposure to high concentration of carbon monoxide (> 5000 ppm), man dies because

Of clotting of blood
It forms carboxyhaemoglobin by combining with haemoglobin of blood, thereby making it incapable of absorbing oxygen
It forms CO₂ by combining with oxygen present in the blood
Of jamming of respiratory tract

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