Smart marketing by water purifier makers has led to widespread use of RO (Reverse Osmosis) filters across the country. A study conducted by the National Institute of Hydrology has found that RO filters do more harm than good by removing essential minerals such as calcium and magnesium from drinking water. The study led by NIH scientist Dr MK Sharma says expensive RO purifiers are not necessary for most surface water sources. A combination of candles, activated carbon filters and ultra violet filters is enough in most cases, says the study.
RO purifiers are needed in those areas where total dissolved solids level of water is more than 500mg per litre. Such filters are needed in case of specific water pollution problems such as fluoride, iron, arsenic, other metals or pesticides. By removing calcium and magnesium from drinking water, RO filters cause several health problems. Bureau of Indian Standards has prescribed acceptable limit of calcium as 75 mg per litre and maximum permissible limit is 200 mg/litre, while for magnesium these are 30 mg/litre and 100 mg/litre. Low levels of calcium and magnesium may cause tooth decay induced by acid producing bacteria. Deficiency of magnesium can cause high blood pressure, irregular heartbeat, diabetes and osteoporosis.
A study by World Economic Forum has estimated that around 70% of surface water in the country is unfit for consumption. Around 40 million litres of wastewater enter Indian rivers and water bodies without adequately treated. A World Bank study has estimated that release of pollution upstream reduces GDP growth in downstream regions by almost half in populous countries like India.
RO is a method of purifying water using membrane technology that removes germs, dissolved salts and other impurities. The semipermeable membrane used in RO filters separates dissolved chemicals and living organisms from water, making it potable. A major concern over RO filters is that it wastes three fourths of the water while treating it. If the reject water is disposed on the surface oil, the chemicals contained in it inters the ground water, causing pollution.
It is estimated that environmental degradation costs India at least Rs 3.75 lakh crore ($80 billion) every year. The impact of water pollution on health is estimated to be around Rs 47,000-61,000 crore ($6.7-8.7 billion) per year. The study says lack of water, sanitation and hygiene results in the loss of around 400,000 lives every year.
The national Green Tribunal had asked the central government to prohibit RO systems in areas where TDS level in water is less than 500 mg per litre. The NIH study was commissioned to create public awareness on technologies suitable for different areas.