SAQs

Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions.

This SAQ is based on key words you have come across in earlier study sessions as well as this one.

Kedir Seid, a Senior Environmental Health Officer, has been informed that there has been an emergency regarding the water supply in his town. The main pipeline has been breached by an excavator at a construction site and mud has been drawn into the water supply. The muddy water is now reaching 2000 homes. Kedir puts together a leaflet to tell people what to do with the muddy water to make it safe to use. Help him in this task by inserting the correct words (from the selection given below) into the gaps in his message:

a cloth, Bishan Gari, boiling the water, ceramic filtration, clear plastic bottles, coagulants, contact time, disinfected, filtration, five, household sand filter, Moringa fruit, pathogenic, sedimentation, settle out the mud, six, solar disinfection, three-pot method, two, Wuha Agar.

Dear Householders,

The water supply is presently muddy due to an accidental breakage of the main water line. Do not worry. We have ways of making the water safe. The first thing to do is to ……………… This can be done by a process called ……………… To encourage this, we can use ……………… The crushed seeds of the ……………… can be used as a natural coagulant. If many containers are available in your household, the ……………… is an option. In this method, the water is settled for at least ……………… days before consumption. Another way to get rid of the mud is by ……………… The simplest way is to use ……………… If you have time, you can make your own ……………… using a pot and a container, sand and gravel. A third option is to use ……………… but this involves setting up a new system that is more costly than the two mentioned just now.

Now, after sedimentation or filtration the water will look clean – but it probably isn’t, because of micro-organisms that may be present. To get rid of any ……………… micro-organisms, the water has to be ……………… Perhaps the easiest, most effective and fastest way of doing this is by ……………… In a city like Addis Ababa, which is at high altitude, we need to boil the water for ……………… minutes. If we do not have fuel at hand, or want to save fuel, we can use ……………… For this we need to put the water into ………………, with their labels removed, and expose it to sunlight for ……………… hours. Another way is to use Aquatabs, which require a ……………… of 30 minutes.

We will do our best to repair the pipe as soon as possible but if we can’t, we will deliver water treatment chemicals like ……………… and sachets of ……………… to you. With these we will send technicians to give guidance on how they are to be used.

With best wishes,

Yours sincerely,

Kedir Seid

(Senior Environmental Health Officer)

Show answer

Here is Kedir’s completed message.

Dear Householders,

The water supply is presently muddy due to an accidental breakage of the main water line. Do not worry. We have ways of making the water safe. The first thing to do is to settle out the mud. This can be done by a process called sedimentation. To encourage this, we can use coagulants. The crushed seeds of the Moringa fruit can be used as a natural coagulant. If many containers are available in your household, the three-pot method is an option. In this method, the water is settled for at least twodays before consumption. Another way to get rid of the mud is by filtration. The simplest way is to use a cloth. If you have time, you can make your own household sand filter using a pot and a container, sand and gravel. A third option is to use ceramic filtration but this involves setting up a new system that is more costly than the two mentioned just now.

Now, after sedimentation or filtration the water will look clean – but it probably isn’t, because of micro-organisms that may be present. To get rid of any pathogenic micro-organisms, the water has to be disinfected. Perhaps the easiest, most effective and fastest way of doing this is by boiling the water for five minutes. If we do not have fuel at hand, or want to save fuel, we can use solar disinfection. For this we need to put the water into clear plastic bottles, with their labels removed, and expose it to sunlight for six hours. Another way is to use Aquatabs, which require a contact time of 30 minutes.

We will do our best to repair the pipe as soon as possible but if we can’t, we will deliver water treatment chemicals like Wuha Agar and sachets of Bishan Gari to you. With these we will send technicians to give guidance on how they are to be used.

With best wishes,

Yours sincerely,

Kedir Seid

(Senior Environmental Health Officer)

An emergency has occurred with the water supply and a tanker is coming to your area to distribute water to the residents. If you were an Environmental Health Officer, what advice would you give the residents as to the best type of container to use to collect the water?

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The water collection container should be clean, have handles and not have contained anything toxic before. The mouth of the container should be narrow and have a lid.

Which of the following statements are false? In each case, explain your answer.

  1. Any opaque plastic container will be satisfactory for storing water at home because, unlike metal, it will not rust.
  2. It is best to have a container that holds a maximum of 25 litres, as that can be easily carried.
  3. The water storage container should have a very narrow opening so that no contaminants can get in.
  4. A tap is an ideal way of keeping stored water safe from contamination.
  5. If the water is stored in a wide-necked container without a tap, and a long-handled ladle is not available, a mug can be used to take the water out.

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1 is false. The plastic should be resistant to oxidation so that it lasts a long time.

3 is false. The opening should be 6–9 cm wide to facilitate cleaning of the container.

5 is false. This method of taking the water out is likely to lead to the transfer of contamination from hands to the water within the container.

Last modified: Monday, 3 October 2016, 5:21 AM