In May 2019, in a case initiated by an NGO called Friends against the Union Ministry of Environment, Forests and Climate Change, the NGT instructed the ministry to issue appropriate notifications prohibiting the use of RO systems where TDS in water is less than 500 mg/l. Wherever RO is permitted, the order said, a requirement is laid down for the recovery of water to be more than 60 per cent. Further provisions were laid down for the recovery of water up to 75 per cent.