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Given below are two statements :
Statement $I$ : If $BOD$ is $4\,ppm$ and dissolved oxygen is $8\,ppm$, then it is a good quality water.
Statement $II$ : If the concentration of zinc and nitrate salts are $5 ppm$ each, then it can be a good quality water.
In the light of the above statements, choose the most appropriate answer from the options given below :
Both the statements $I$ and $II$ are incorrect
Statement $I$ is incorrect but Statement $II$ is correct
Both the statements $I$ and $II$ are correct
Statement $I$ is correct but Statement $II$ is incorrect
Solution
Clean water would have $BOD$ value of less than $5\,ppm$.
Maximum limit of $Zn$ in clean water $=5.0\,ppm$ or $mg\,dm ^{-3}$
Maximum limit of $NO _3^{-}$in clean water $=50\,ppm$ or $mg \, dm ^{-3}$
