Remember Hema Malini's famous advertisement for Kent RO water purifier? Well, that ad made RO systems a household name and catapulted the system as a need for every house in urban India where the groundwater is considered to be contaminated.
The reverse-osmosis (RO) water purifier at home seems to be a benign invention, allowing people to drink clean, healthy water.
But now scientists are warning that rampant use of the RO technology could pose a serious threat to public health.
One of the most popular water purifying technologies in India, the RO process is efficient in terms of filtering out toxic substances like arsenic and fluoride, especially in areas where groundwater is heavily contaminated.
Simultaneously, though, RO systems, at both household and industrial levels plough back concentrated amounts of these substances back into the aquifers.
Experts suggest that regulations are needed to stop the unchecked use of RO, or at least the disposal of the stuff left behind after filtering.
"What we found with our survey is that industrial firms, like bottled-water ones, and households have no way out but to put it back into the soil and aquifers," said Saradindu Bhaduri, Assistant Professor, Centre for Studies in Science Policy, School of Social Sciences at Jawaharlal Nehru University (JNU).
The arsenic and fluoride-laden waste water generated by RO systems could have "adverse consequences" for human and animal health after it is dumped back into the groundwater aquifers, he told IANS. This could affect the population in the surrounding area which is dependent on this water source.
"The waste water contains high amount of total dissolved salts like sulphates, calcium, bicarbonates and organic matter and higher concentration of arsenic and fluoride in areas where originally these elements were reported in ground water," co-author of the study, Aviram Sharma of the JNU, said.
Published on April 25 in Current Science, the survey report titled 'Growth of water purification technologies in the era of regulatory vacuum in India' also questions the absence of proper methods to dispose of the contaminated waste water.
The research shows that bottled water firms of all sizes and classes, ranging from major multinationals to the vast majority of India's 2,700 small proprietory firms, use RO-based water purification technologies in their manufacturing plants.
The USP of RO-based system is that it can produce higher amount of filtered water with less supervision in comparison to methods like ion-exchange, explained Sharma.
However, there is a drawback. During industrial use, waste water amounts to between 30 and 40 percent of the total water used. At the household level too there is a huge wastage.
This can have a "disastrous impact" in water-starved areas due to over extraction of ground water, which is a major source of fresh water in most of the regions in India, said Sharma.
Originally invented to make seawater potable, RO technology is being used in India without regulation.
Most of the countries where the technology is used extensively, the feed water is primarily sea water or brackish water, according to the researchers.
Namit Bajoria, Director, Kutchina, which entered into the water purifier market with an RO-based system, conceded that wastage was a concern.
"It is like an equal and opposite reaction. 100 litres of water will give only 10 to 12 litres of pure water. So wastage is a big problem. But I don't agree that it can cause harm to the groundwater. You are taking from it and giving it back," Bajoria said.
Bhaduri, however, says that "We have regulations for water quality but we don't have regulations for the application of these processes."
He also said that more epidemiological studies were needed so that customers can make an informed choice.