Environmental Engineering
In a BOD test, 1.0 ml of raw sewage was diluted to 100 ml and the dissolved oxygen concentration of diluted sample at the beginning was 6 ppm and it was 4 ppm at the end of 5 day incubation at 20°C. The BOD of raw sewage will be

300 ppm
100 ppm
200 ppm
400 ppm

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Environmental Engineering
Assertion A: Slow sand filters are more efficient in removal of bacteria than rapid sand filters.Reason R: The sand used in slow sand filters is finer than that in rapid sand filtersSelect your answer based on the coding system given below:

Both A and R is true and R is the correct explanation of A
A is true but R is false
Both A and R is true but R is not the correct explanation of A
A is false but R is true

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