New Delhi: The Central government has drawn up plans to ban the use of membrane-based water purification systems (MWPS) – primarily reverse osmosis (RO) systems – in areas where the source of water meets the Bureau of Indian Standards’ drinking water norms.

According to a report in The Hindu, the environment ministry has released a draft notification that effectively prohibits home users to install MPWS. “Installation or use of MWPS [Membrane based Water Purification System] shall be prohibited, at the point of use or at the point of entry for purification of supplied water which is subjected to conventional flocculation, filtration and disinfection process or is from any sources which are in compliance with acceptable limit for drinking water prescribed by Bureau of Indian Standard 10500:2012,” the notification, made public on Monday, reads.

Comments from stakeholder have been invited by the ministry for 30 days, after which it may issue an order on banning these water purification systems, incorporating any suggested changes before it becomes a law.

Jigmet Takpa, joint secretary to the Union environment ministry, told The Hindu that users will not be prosecuted for installing RO systems. “However, this is part of a significant change we are implementing to regulate RO manufacturers and inform consumers that RO systems aren’t needed always,” he added.

Supply boards in many cities, including the Delhi Jal Board, claim that the water they supply meets BIS norms. However, a November 2019 study by the BIS said among 20 cities surveyed, only Mumbai’s drinking water is compliant with its standards. Delhi chief minister Arvind Kejriwal dismissed the report as false and being politically motivated.

Draft notification follows NGT order

The environment ministry’s draft notification comes after the National Green Tribunal (NGT) prohibited the use of RO purifiers in places where total dissolved solids (TDS) in the supplied water are below 500 mg per litre.

In May 2019, the NGT, hearing a petition, directed the environment ministry to ensure that RO systems manufacturers lower the percentage of water that is wasted during treatment. At least 60% of the water should be recovered and not more than 40 per cent should be wasted, the tribunal said, saying that the recovery rate should eventually be enhanced to 75%.

The petition was filed by Sharad Tiwari, the general secretary of a Delhi-based non-profit. He argued that “indiscriminate use” of ROs is resulting in huge wastage of water.

The Water Quality Association of India, a consortium of RO systems manufacturers, then moved the Supreme Court requesting a stay on the NGT order. The SC declined to intervene, after which the NGT directed the environment ministry to issue a notification to restrict the use of water filters.

According to The Hindu, the NGT’s ordered sought a ban on RO filters because they waste water and in the process of removing salts, “they often deprived drinking water of essential salts”. “RO while useful in reducing salts does not tackle bacterial agents or trace chemicals and manufacturers often claim that additional filtration is required to deliver potable water,” the tribunal observed.

Current BIS regulations consider 500-1,200 mg/litre of total dissolved solids, which consists of salts and some organic matter, as acceptable though there is no lower limit.

Reports also said that the draft notification also puts regulations on commercial bottlers who use RO systems to purify water. Commercial units will be required to store water that is lost in the purification process in “safe, hygienic” conditions. They will also be required to maintain a record of water that is wasted.

To comply with the NGT’s order of recovering 75% of the water, by June 5, 2022, RO manufacturers can only supply home purification systems that waste no more than 25% of the water. These systems must be able to inform consumers of the TDS levels at the inlet and water outlet, the notification adds, according to The Hindu.

The notification also says that violations should be brought to the notice of the state and Central pollution control boards. The Central Pollution Control Board will be the nodal agency to implement the rules.