The Supreme Court on Friday asked an association of RO manufacturers to approach the government on the National Green Tribunal's order prohibiting the use of reverse osmosis purifiers when total dissolved solids (TDS) in water are below 500 mg per litre.
The apex court was hearing a petition filed by the Water Quality India Association, representing RO manufacturers, challenging the NGT's order directing the government to regulate the use of purifiers and sensitise the public about the ill-effects of demineralised water.
A bench of Justices R F Nariman and S Ravindra Bhat said the association can approach the concerned ministry within 10 days with relevant material on the matter and the government will consider it before issuing a notification in accordance with the NGT's direction.
During the hearing, the counsel representing the association referred to a recent BIS report on standards of water in various cities across the country and said it points to the presence of heavy metals in Delhi's groundwater.
The NGT had in May directed the government to prohibit RO purifiers in places where TDS in water is below 500 mg per litre and sensitise the public.
The tribunal had also asked the government to make it mandatory to recover more than 60 per cent water wherever RO purifiers are permitted.
TDS is made up of inorganic salts as well as small amounts of organic matter. According to a WHO study, TDS levels below 300 mg per litre are considered excellent, while 900 mg per litre is said to be poor and above 1,200 mg is unacceptable.
Reverse osmosis is a water treatment process that removes contaminants from water by using pressure to force molecules through a semipermeable membrane.
NGT had 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 had said if TDS is less than 500 milligrams per litre, RO systems will not be useful, resulting in removing important minerals as well 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 had said.
The tribunal had also asked the ministry to issue directions and said the notification may also provide for a mechanism for public awareness about the ill-effects of demineralised water.
It ordered directions to be issued for the enforcement of 'extended producers responsibility' by the manufacturers for the 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.
The Water Quality Indian Association had told the NGT that RO water purifiers ensure availability of pure water. It is, however, not disputed that only 20 per cent water is recovered and 80 per cent goes waste.