Compared to normal water,the $BOD$ of sewage-polluted water is . . . . . . .

Eutrophication includes all,except

The presence of large amounts of nutrients in water causes excessive growth of planktonic algae,called.........

$CNG$ is considered a more efficient fuel. Which of the following statements is incorrect regarding it?

Consider the following statements:
$I.$ Algal blooms are formed by free-floating algae.
$II.$ Algal blooms cause fish mortality and deterioration of water quality.
$III.$ Water hyacinth, the world's most problematic aquatic weed, is also called 'Terror of Bengal'.
Which of the statements given above are correct about algal blooms?

Which one of the following is the heavy toxic metal present in waste water from industries?