Be Prepared for Life

Activity Kit Three:
"Water for Life"

Part 2. Cleaning water


In a dry country when the rains come and the streams and rivers fill with water, human and animals faeces are washed into the streams from the veld. The bacterial counts in streams rise and the water may become dangerous to drink. In the dry season humans and animals gather around watering points and disease is often spread through this contaminated water. You could get Cholera [severe diarrhoea leading to death] by drinking water in an area which has inadequate sewage facilities and contaminated water. It is risky to enter rivers and streams in the Transvaal low veld, Natal and the Transkei as the snail that hosts Bilharzia [a disease of the bladder and intestines] occurs in the vegetation alongside the banks. Unprotected water is at risk and needs to be cleaned and purified before drinking.

Project 4: How clean is your stream?

  1. Your patrol could start a water watchers programme. The more polluted water becomes, the less available oxygen it contains. Bacteria will multiply in this polluted water. Some bacteria may be dangerous! Keep a lookout for oxygen loving life forms and life forms that tolerate low levels of oxygen. A dominance of pollution tolerant forms can bethe first signs of a developing problem.
  2. Choose three sections of a nearby stream and monitor them once every season. Always start at the lowest point and work upstream. Wear rubber boots to protect your feet and gloves to protect your hands if working in water east of Port Elizabeth [Bilharzia]. Find a riffle of fast moving water.
  3. Using a homemade D-frame net or kick seine net move up stream through 1 meter of the riffle kicking the stones to loosen animals and collecting them in the net behind your feet. Place the specimens in a white dish and identify them.
    Are they the pollution sensitive or pollution tolerant organisms? Use these diagrams to identify your specimens, count the numbers in one square meter and record your data before retuning them to the stream. These animals help to clean the stream and keep it alive and healthy. Average your data from all three sites.

  4. Enter your data on a table like this...

    POLLUTION          SOMEWHAT           POLLUTION 
    Shrimp      .....  Beetle             Worms       .....
                       larvae      .....  Black fly
    Stone fly   .....  Crane fly          larvae      .....
                       larvae      .....  Midge fly
    May fly     .....  Damsel fly         larvae      .....
                       nymphs      .....
    Caddis Fly  .....  Dragon fly         Snails      .....
                       nymphs      .....
    Total numbers      Total numbers      Total numbers
    ..... x 3 = .....  ..... x 2 = .....  ..... x 1 = .....
    index value        index value        index value

    Add the 3 index values together to get a total index value = .....

    Interpretation of total index value
    More than 22  = Excellent water quality
    17 to 22      = Good water quality
    11 to 16      = Fair water quality
    Less than 11  = Poor water quality

    Good water quality is indicated by a variety of different kinds of organisms from all three groups. Over a year you will get a picture of seasonal fluctuations in water quality.

The really dangerous animals are microscopically small and need to be cultured before they can be seen.
Patrols wishing to get involved in a more complete monitoring of water quality are advised to write to Project W.A.T.E.R. Sharenet P.O.B. 394 Howick 3290.


Scarcely any water is pure today. Rain water is often contaminated with ash and acid, ground water may be contaminated with salts and bacteria. The water is likely to be cleanest in the mountains and dirtiest near the cities. A lot of the price of water is in the purification costs. Yet it can be done cheaply on a small scale.
Sunlight kills bacteria! Water in a capped 2 liter plastic bottle left lying on its side in strong sunlight for 4 hours will have very few live bacteria left in it.

Project 5: Filter your water

  1. Bacteria cannot grow in sand! They die off naturally without food and warmth. Water holes dug in the beds of rivers or in sand dunes yield reasonably safe water for this reason. A sand filter is used where the purity of the water supply is suspect.
  2. A family-sized sand filter can be built in a 200 liter drum. This will yield 50 litres of purified water per day. Traditional pots and cement jars [see Project 2] can also be used. The lid is cut off the drum, its cleaned and the inside painted with a lead free paint.
    A tap is brazed or fixed with quick set putty into the drum two thirds of the way up the side. Alternatively a longer hose is pushed through the drum [sealed with putty] and raised or lowered [as a siphon] to start the flow of water.
  3. A plastic pipe [hose pipe] is fitted to the tap and the free end forms a coil inside the base of the drum. The lower surface of the coil is cut at many points with a saw.
  4. The drum is packed to two thirds of its depth with clean river stones and pebbles, river gravel, coarse river sand [at least 60 -70 cm of sand]. A large flat stone is placed on top of the sand to minimise disturbance through pouring.
  5. Build a cover of some sort with a hole over the stone through which water can be poured each day. ]
  6. Flush the sand filter thoroughly until the water coming through is clear and clean. The sand filter will take a few weeks to "ripen" and become fully biologically active.
  7. If the flow rate diminishes due to a blocking of the pores in the upper sand layer, open the lid and replace the top 10 centimeters of sand to restore the filtering rate.
  8. Water should be drawn off slowly in small amounts and the filter be kept topped up at all times to ensure the slowest possible movement of water through the system and maximum purification.
    It should never be drained! It is not just a particle filter but an active, living biological system as well.

Project 6: The Water Boiler

  1. When larger quantities of water are needed than can be supplied in a hurry by a small family sand filter the community can build a larger sand filter [see Project 2 in a water tank] or boil water. This technique could be used on survival hikes when water quality is suspect.
  2. When there is more time available a water boiler can be constructed as part of a camp stove. The tap should be brazed in at low level.
  3. Pure hot water will be available once the drum has boiled. Don't forget to leave a vent for the steam to escape, or your boiler will be very dangerous!

Project 7: The chemical treatment of water

  1. A little chlorine in water kills bacteria safely. A teaspoon of "Jik", "Milton", or "Javel" bleach will purify 10 liters of water in an hour, and two teaspoons will purify 10 liters in 30 minutes.
  2. Chlorine releases oxygen from water which kills bacteria. The more bacteria present in the water the more chlorine is needed to destroy them.
    Swimming pool chlorine [preferably free of cyanuric acid] can be added to suspect water in a tank until sufficient free chlorine remains to indicate that all bacteria have been destroyed. A swimming pool test kit should show a pale yellow colour and until it does it is possible that bacteria are still active in the water.
    Rather use too much than too little. The excess chlorine soon disappears from the water. If you built a 5000 liter tank in Project 2 then 15 g or a quarter cup of chlorine should be sufficient to purify the tankful of water [5000 l]. Chlorinate water overnight for the best prolonged purifying action.

Project 8: Building a solar still

Where water is brackish or salty a pan with a transparent cover will heat up the water and distil it into a collecting dish.

Building a family-sized solar still

  1. The site needs to be level and exposed to full sun as much of the time as possible.
  2. Use the techniques described in the building of a water tank in Project 2.
  3. The floor of the evaporating basin should have a slight slope so that the impure water can be flushed out of the basin each morning. The walls can be made of bricks and the frame of wood, bamboo or piping.
    A transparent cover area of one square meter will produce about two liters of water a day.
    Calculate how much distilled water you need each day. If you need a minimum of 3 litres per person and are building the solar still for a family of four people, then...

    You need 3 x 4 = 12 litres / day

    Make your plastic sheeting surface at least 3 x 2 meters. 6 square meters will produce 12 liters of distilled water per day.

  1. The upper surface of the plastic can be used to collect rain water and the inner surface, distilled water.
  2. The pure water can be collected in a cement jar or tank [Project 2].
  3. Impure water can be added to the system each day.

Building a "survival" still.

  1. Choose a likely place to extract water from the soil such as a dry river bed, or deep rich soil at the bottom of a gully. Make sure the sun can reach your solar still.
  2. Dig a hole at least 1 meter deep and 1 meter across at the surface. Place a billy at the bottom of the pit with a 1,5 m polythene tube [fish tank tubing] weighted by a stone in the billy. Run the free end up to the surface.
  3. Place a sheet of clear plastic, about 2 x 2 meters over the hole. Place a stone on the centre and allow it to carry the plastic down to centre over the billy, about 5 cm above it.
  4. Seal the edges of the sheet with heaped soil, but leave the plastic tubing clear to suck water up from the billy.
  5. Under ideal conditions it can produce about a liter a day.
  6. This technique is only advised as a survival technique. In less than ideal conditions a single person might need two stills to survive any length of time.

Part Three: How to care for water

© Copyright 1991 - 1994
Dr Frank Opie for the South African Scout Association