In a bid to regulate the use of RO purifiers, NGT has directed the government to prohibit them where total dissolved solids (TDS) in water are below 500 mg per litre and sensitise public about the ill effects of demineralised water.

The tribunal has also asked the government to make it mandatory to recover more than 60 per cent water wherever RO is permitted across the country.

TDS is made up of inorganic salts as well as small amounts of organic matter. As per a WHO study TDS levels below 300 mg per litre are considered to be excellent, while 900 mg per litre is said to be poor and above 1200 mg is unacceptable.

Reverse Osmosis (RO) is a water treatment process that removes contaminants from water by using pressure to force molecules through a semipermeable membrane.

A bench headed by NGT Chairperson Justice Adarsh Kumar Goel passed the order after perusing a report of a committee formed by it, and gave the directions to the Ministry of Environment and Forests (MoEF).

The committee said that if TDS is less than 500 milligrams per litre, RO system will not be useful but result in removing important minerals as well as cause undue wastage of water.

"MoEF may issue appropriate notification prohibiting use of RO where TDS in water is less than 500 mg/l and wherever RO is permitted, a requirement is laid down for recovery of water be more than 60 per cent. Further provision be laid down for recovery of water up to 75 per cent and use of such RO reject water for purposes such as utensil washing, flushing, gardening, cleaning of vehicles and floor mopping," the NGT said.

The tribunal asked the ministry to issue directions and said the notification may also provide for a mechanism for public awareness about ill effects of demineralised water.

It may also "provide for a mechanism for public awareness about ill effects of demineralised water on public health and for effective enforcement requiring the concerned local bodies...and institutions like Public Health Engineering Department (PHED)/ Jal Nigam/ Jal Boards be required to display water quality at regular intervals, particularly TDS concentration component by an appropriate mechanism".

It also ordered that directions be issued for enforcement of Extended Producers Responsibility by the manufacturers for disposal of cartridges and membranes and directing manufacturers to provide proper labelling on the purifier specifying that the unit should be used if TDS is more than 500 mg per litre.

MoEF may file an affidavit of compliance by e-mail within a month, the tribunal said.

It also directed the expert committee constituted by it along with Central Ground Water Authority to collect and provide data with regard to availability of ground water and its usage in 21 cities mentioned in the report of NITI Aayog and furnish a report to this tribunal within a month.

The NGT said that remedial measures are necessary for preventing unnecessary wastage of potable water on account of use of RO systems and there is also need for directing the concerned local bodies to display water quality regarding TDS concentration component.

Water Quality Indian Association (WQIA), representing the RO manufacturers, told the bench that RO water purifiers ensures availability of pure water. It is, however, not disputed that only 20 per cent water is recovered and 80 per cent goes waste.

They also said that in 98 districts in 13 states, there is high TDS which can be purified only by RO systems.

The Tribunal was hearing a plea filed by NGO Friends seeking conservation of potable water by preventing its wastage on account of unnecessary use of Reverse Osmosis (RO) systems.

It had sought directions to the ministry to conduct research work about the "quality" of water produced by reverse osmosis water purifier called RO filter as compared to natural water.

The NGT Expert Committee comprised of representatives of MoEF, Central Pollution Control Board (CPCB), Bureau of Indian Standard (BIS), IIT (Delhi) and the National Environmental Engineering Research Institute, Delhi (NEERI, Delhi).

Also read: NGT forms committee to assess fine from thermal power stations in Singrauli, Sonbhadra

Also read: New PHNIX Commercial Heat Pump Water Heater with High Cost-effectiveness to Launch in India