Environmental Engineering
The amount of residual chlorine left in public water supply for safety against pathogenic bacteria is about

1.0 to 5.0 ppm
0.01 to 0.05 ppm
0.05 to 0.5 ppm
0.5 to 1.0 ppm

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Environmental Engineering
Double filtration is used

All of these
To increase the filtration slow sand filters capacity of
For isolated buildings like pools, hotels etc swimming
To increase the filtration rapid sand filters capacity of

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