The Bureau of Indian Standards (BIS) will rank state capitals and 100 smart cities in the next three months for quality tap water, Consumer Affairs Minister Ram Vilas Paswan said on Monday.

The BIS will also test quality of tap water at district level in the next six months, he said adding that his ministry has written to state governments to make BIS standard mandatory on drinking water.

At present, the BIS standards for drinking water are voluntary in nature.

"The BIS has begun the process of collecting the samples of tap water from state capitals and smart cities," Paswan said at an event organised to commemorate the World Standards Day.

After testing the samples, the BIS will rank state capitals and 100 smart cities for quality water in the next three months, he said and added that this initiative will be taken to district level in next six months.

BIS -- the national body that frames quality norms for products and services and works under the Ministry of Consumer Affairs -- has been asked to test tap water in other parts of the country after a preliminary investigation showed that samples collected randomly from 11 areas in the national capital do not comply with the BIS standard and are not safe for drinking, he added.

The final report of samples collected from Delhi will be made public next month, Paswan said.

Speaking about video standards, the minister said that it plays a key role in areas like smart cities and smart manufacturing as huge amount of video streaming data is transferred from sources such as surveillance cameras across the cities and virtual reality system in various industries.

The BIS is actively involved in the international standardisation work of video standards through a technical committee which is responsible for video compression, he said.

BIS has prepared indigenous standards for Set Top Boxes for cable TV, Direct-to-Home terrestial TV and IP-TV. The BIS panel has also prepared indigenous standards for 'optical fibres network' for allowing high speed data transmission. It is also preparing standards for next generation LEDs and advanced TV standards.

The Minister also mentioned that the BIS is working towards 'One Nation, One standard' to remove multiplicity, duplicacy of efforts and to bring more clarity among consumer, manufacturers and to facilitate trade.

Minister of State for Consumer Affairs Ministry Raosaheb Patil Danve, Consumer Affairs Secretary Avinash Kumar Srivastva, BIS Director General Rohit Kumar Parmar were also present at the event.