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

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Environmental Engineering in CE
Aerobic biological oxidation ponds used for the purification of polluted water

Is not very effective for nonbiodegradable substances (e.g. ABS) containing effluents
All of these
Destroys/removes pathogen much more effectively if the sewage is chlorinated
Destroys/removes pathogen from the sewage

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