Question

Read the following statements and find out the incorrect statement

• A. Solids are relatively easy to remove from domestic sewage.
• B. None of the above.
• C. Dissolved salts such as nitrates and phosphates, and toxic metal ions and organic compounds are most difficult to remove.
• D. Presence of large amounts of nutrients in waters causes excessive growth of fishes and other aquatic creatures.

Answer 1

The correct option is D Presence of large amounts of nutrients in waters causes excessive growth of fishes and other aquatic creatures.

Statement A
About $0.1\%$ of impurities are present in the form of suspended solids, colloids, and dissolved material in domestic sewage.
This impurity is much difficult to remove.

Statement B
Dissolved salts such as nitrates and phosphates, and toxic metal ions and organic compounds can be removed easily by using techniques like precipitation, microbial activity etc.

Statement C
Presence of large amounts of nutrients in waters will cause algal bloom. Which results in rapid growth of algae. These algae deprive the aquatic life from oxygen and nutrients. Thus there will be a decline in growth of fishes and other aquatic creatures.