GATE Exam Questions - Engineering

Q1:

Presence of excess nitrates in river water indicates :

A recent pollution of water with sewage

B past pollution of water with sewage

C immediate pollution of water with sewage

D no pollution of water with sewage

ANS:B - past pollution of water with sewage

Presence of Nitrates in sewage indicates that the decompostion of organic nitrogenous matter has come to an end i.e. nitrates are the end products of bacterial decomposition of nitrogenous matter in sewage. Hence their presence means that the water has been polluted in the past.