Biochemical oxygen demand values of four water samples P, Q, R and S are respectively 100 ppm, 50 ppm, 150 ppm and 10 ppm. Arrange them in the descending order of their purity.

Biochemical oxygen demand values of four water samples P, Q, R and S a

1.	Biochemical oxygen demand values of four water samples P, Q, R and S are respectively 100 ppm, 50 ppm, 150 ppm and 10 ppm. Arrange them in the descending order of their purity.
Answer» Solution :More the BOD VALUE, more the extent of pollution and less the PURITY of water. Thus purity of water SAMPLES is in the order `S GT Q gt P gt R`.