Question

The effective size (ES) of sand and its uniformity coefficient (UC) are the usually specified parameters for sand filters. In slow sand filters, as compared to rapid sand filters,

• A. Both ES and UC are more
• B. ES is less but UC is more
• C. Both ES and UC are less
• D. ES is more but UC is less

Answer 1

The correct option is B ES is less but UC is more

(a)

	Slow sand filter	Rapid sand filter
Effective Size	0.2 mm to 0.4 mm	0.35 to 0.55 mm
Uniformity coefficient	1.8 to 2.5	1.2 to 1.8

Thus in slow sand filter, ES is less but UC is more than that in rapid sand filter.