Self-Assessment Questions (SAQs) for Study Session 14

Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering the following questions. Write your answers in your Study Diary and discuss them with your Tutor at the next Study Support Meeting. You can check your answers with the Notes on the Self-Assessment Questions at the end of this Module.

SAQ 14.1 (tests Learning Outcome 14.1)

Match the phrases with the corresponding words.

Using the following two lists, match each numbered item with the correct letter.

  1. Process of treating with chlorine

  2. Time required to wait to drink after chlorination

  3. Water not yet treated

  4. Free residual available chlorine in treated water

  • a.Chlorine contact time

  • b.Chlorine residual

  • c.Chlorination

  • d.Raw water

The correct answers are:
  • 1 = c
  • 2 = a
  • 3 = d
  • 4 = b

SAQ 14.2 (tests Learning Outcome 14.2)

Suppose you went to a village to promote household water treatment. Mr. Abebe, a local farmer, asks you why he needs to treat the water for drinking. What would you say to him as an explanation?


Nearly all river and stream water may be contaminated with at least one of the three types of potentially disease-causing microorganisms, namely protozoa, bacteria and viruses. These can be removed by treating the water.

If Mr. Abebe used one of the methods of household water treatment he would be protecting his family and himself from many unpleasant, debilitating and possibly life-threatening diseases.

SAQ 14.3 (tests Learning Outcome 14.3)

Suppose you have a group of women in your area who want to know about household water treatment by chlorine solution, particularly Wuha Agar. What are the key points you would explain to them?


Wuha Agar is a type of chlorine solution that is commonly available. To use it you add one capful of Wuha Agar to a 20 litre jerrycan of water, replace the lid and shake. After 30 minutes of contact time you can use the water for drinking and other domestic purposes. This will kill bacteria and help to reduce diarrhoeal diseases.

SAQ 14.4 (tests Learning Outcome 14.3)

A man comes to see you and explains that his family obtains water from a protected water source and that it has been treated with chlorine. He asks you how he can find out whether the chlorine still protects his family or not. How could you find out if his water was still safe to drink?


You should do the orthotolidine-arsenite test (OTA) to measure the residual chlorine. The residual chlorine helps to prevent recontamination of pathogenic bacteria if it is between 0.2–0.5 mg/l.

SAQ 14.5 (tests Learning Outcomes 14.1 and 14.4)

Filtration and disinfection are important water treatment processes. Briefly describe each of these processes and explain their role in making water safe to drink.


Filtration means passing water through a layer of sand, gravel, cloth or other barrier that allows the water to pass through, but holds back any small particles. The particles may be dirt, soil and other contaminants including many pathogenic microorganisms that make the water unsafe to drink. However, some bacteria can pass through filters, so filtered water is not completely safe to drink.

Disinfection is a process for removing contaminants from water and killing most of the harmful microorganisms that may be present. It usually involves treatment with chlorine or other chemicals.

Summary of Study Session 14