Step 1: CLAY WATER FILTER DESIGN BY TONY FLYNN

Step 2: Design by Mr. Tony Flynn

Address:
Department of Engineering
Faculty of Engineering & Information Technology,
The Australian National University, Canberra
Telephone: +61 2 6125 0078

Step 3: Unlike other water filtering devices, the filters are simple and inexpensive to make.

Step 4: Make the clay mixture

Dig the red to brown coloured terracotta clay and dry it in the sun. Pound and crush the clay so that it is fine and powder. Mix one handful of dried and crushed clay with one
handful of dry organic material (used coffee grounds are ideal, rice hulls or tea leaves may also be used), ensuring it is well distributed through the clay. Add a little water at a time,
using just enough to produce a stiff mixture that is firm to handle, is not wet and will not lose its shape when moulded. 

Step 5: Shape into filter pots and place them in fire

Shape the clay mixture into a cylinder and leave it to dry in the sun. The walls of the finished pot should be about as thick as an adult’s index finger. Do not break up or crush the lumps of cow manure, the best heat will come from as-found lumps or pats. Put the dried filter forms onto a layer of dry manure, surround them with dry straw or leaves and add another two or three layers of manure. The pots should be
completely covered and not visible. Light the straw or leaves. 

Step 6: Fuel the fire with more manure.

The fire will reach a temperature of 700C in about half an hour and will reach 900-950C after another 20 to 30 minutes. It will be necessary to add manure — placing it over holes in the sides and top of the burning mound — to keep The fire at the required temperature. The temperature of The fire can be judged by its colour, when it is burning well the fire will be a bright orange-to-yellow colour. The filters should be in the fire at that colour for at least 30 minutes.

Step 7: Bake the filters in the fire

The firing process will take less than an hour to sinter the filters and burn away the organic material, leaving passages that are wide enough for water to pass through, but too small for contaminants such as e-coli. 

Step 8: Remove the filters from the fire

After firing for 45-60 minutes, remove the pots from the fire. The pots will be red hot so should not be touched. More unfired pots can be put into the fire at this point, and covered with more cow manure as before. You will need to repeat the process and wait until the fire is burning strongly
and to see the same colour again for at least 30 minutes before removing the next filter. 

Step 9: Filter water

Allow the filter to cool. Wash out any charcoal or rubbish and fill with water. Discard the first water to pass through the filter, water can then be filtered through them. For heavy contamination, two or more filters can be used in a series.