The supply of safe drinking water continues to be a major hassle to overcome in flood-affected areas. Chlorine tablets have been cited as a possible quick-relief, but there are other ways of disinfecting drinking water if the chlorine tablets are not available. The three-pot water treatment is a simple method that may be of help.
On day one, put the raw water in pot one. Leave it for 24 hours. On day two, very slowly pour water from pot one to pot two, and, since pot one would be now empty, it should be refilled with raw water. On day three, slowly pour water from pot two to pot three, and use it from pot three after a few hours. The water, which has now been stored for more than two days, will kill schistosomes that cause bilharzia. Other bacteria will also die off the same way.
Disease-causing organisms, like pathogens, are ‘adsorbed’ to the suspended solids which will settle to the bottom of the tank, further improving the quality of water. The bottom sediments in all pots are to be discarded.
In another method, one pot is placed on top of the other pot. The bottom pot is empty, and should be clean. The other pot, placed on top of the clean pot, contains coarse sand, fine sand and gravel, in that order. Coarse sand is placed on top of the gravel, and the fine sand is placed over the coarse sand. The pot has a hole at the bottom. Raw water is poured over the fine sand, and the water gets filtered as it moves down from fine to coarse sand, and on to the gravel. The filtered water is collected in the bottom, cleaned pot.
Biosand filter is a simple household water treatment method which is an innovation on traditional filters. Biosand filter consists of a plastic or concrete container filled with specially selected sand and gravel. Downward flow of water in the filter removes turbidity, pathogens, colour, odour and iron from water. As in the case of slow sand filters, a biofilm (Schmutzdecke) develops on top of sand layer, and this biofilm is instrumental in removing the pathogens.
Once the flood victims are stabilised, the next level of water treatment will be required. The process consists of a two-stage filter system. In the first filter column, shredded coconut fibre is placed, while burnt rice husk is placed in the second column. Water flows from the first to the second column. The second filter unit is placed at a level lower than the first one to encourage gravitational flow of water.
The first-stage unit removes the initial turbidity, while the second unit polishes off the effluent. The filter media has the ability to entrap the particles through the process of ‘adsorption’ as against the sand filters, which simply filters out the turbidity. This means that the particles just need to be agglomerated enough to get trapped by the filter media, and not to the extent of getting settled.
Depending upon the operation of the system, the treated water quality would, in general, meet the World Health Organisation (WHO) guidelines for the drinking water quality, for taste, colour, turbidity and bacteriological content. Coliform removal in properly operated systems would be more than 90 per cent. In case of highly raw waters with bacteriological pollution, a re-run of such waters through the system is recommended.
The flood victims who have been relocated to their villages would need a third method of water treatment. Slow sand filtration is a promising water treatment method for rural areas. The basic principle of the process is simple. Raw water flows through a layer of sand and gravel. The system provides two-fold treatment: filtration and biological treatment. Slow sand filtration is effective in the removal of bacteria, protozoa, viruses and turbidity. Design and construction of slow sand filtration will require some official assistance. The Mehran University of Engineering and Technology, Jamshoro, may be a good option in this regard.
The benefits accrued from the improved quality of drinking water will become void if the excreta disposal is not managed properly. The flood victims also need to maintain a good personal hygiene, which will be a great barrier against diseases, like body lice, diarrhoea, tooth decay, pinworms, scabies, urinary tract infection and ringworms.
F H MUGHAL
KARACHI
