STUDENT SPACE · TOPIC 4

Water treatment and aquatic life

Explain what each water-treatment stage removes and how pollutants affect aquatic life.

The essentials

Dissolved oxygen supports aquatic life. Some dissolved metal compounds provide essential minerals.
Sedimentation and filtration remove solids. Carbon removes tastes and odours.
Fertilisers supply nutrients for plants, but nitrates and phosphates entering water can lead to oxygen depletion.

Try each question before opening its hint or answer. Use paper for calculations and diagrams.

Does chlorination remove dissolved toxic metal compounds? Explain.

Need a hint for Question 1?

Name the contaminant first. Choose a stage that acts on that contaminant.

Check Question 1

No. Its role is to kill microbes. Other contaminants need suitable treatment.

Explain the roles of filtration and chlorination in domestic water treatment.

Need a hint for Question 2?

Separate removal of particles from disinfection.

Check Question 2

Filtration removes solids; chlorination kills harmful microbes.

Name one beneficial substance in natural water and explain one harmful effect of nitrate pollution.

Need a hint for Question 3?

Think about respiration and oxygen use during decomposition.

Check Question 3

Dissolved oxygen supports aquatic life. Nitrates can cause deoxygenation, harming aquatic life.

Use Lesson 4 in your worksheet for written practice. Your teacher will discuss those answers in class.