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— Photo: V. Sreenivasa Murthy

Check it out: It is better to know the mineral content of the water you drink.

Around 66 million people inhabit areas in India which are susceptible to excess fluoride in groundwater. Since groundwater is the predominant source of drinking water, this poses a problem.

When the deep tubewells, or borewells as we know them, came to India, they were a matter of preferred choice because unlike surface water bodies, deep groundwater was supposed to be pure. However, as time has chugged along, partly due to human reasons and partly due to natural reasons, groundwater too is showing high levels of quality problems.

These arise from five major reasons: excess salinity or salt in groundwater, excess iron, excess nitrates, excess arsenic and excess fluoride. In the case of fluoride the maximum permissible limit for it in water is 1.50 mg/litre. However, in many habitations, this limit has been crossed and in some places fluoride well above 10 mg/litre is also reported.

Since fluoride cannot be seen or smelt and indeed sometimes the water can be sparkling it requires a detailed analysis to detect its presence and measure its quantity in drinking water.

A little bit of fluoride is actually beneficial for teeth and bones. Only when it exceeds limits does it become a problem, causing dental fluorosis and skeletal fluorosis. Body pain and ache is reported and the pain in the joints can be excruciating.

A project run by the Government of Karnataka called Sachetana seeks to harvest rooftop rainwater and provide this to families as fluoride-free water. Approximately 20 litres per family per day is required for drinking and cooking purposes. In a year this translates to 7,300 litres of water.

A roof area of 30 square metres and a climatic zone with 300 mm of rain has 9,000 litres of rainwater falling on the roof. If this water can be collected, filtered in a good sand filter and stored in either an underground or overground tank it can be kept for a year without getting spoilt.

This is what the Sachetana project being implemented by the NGO BIRD-K does.

People in all the villages are happy with the result and report improvement in their physical condition even as early as three months of drinking this fluoride-free water. Other methods of defluoridation are also available at household and community level all over the country but rainwater harvesting from rooftops remains the easiest of all method and the permanent one too.

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