The units claimed they were adding 'nannari', 'athimathuram' and some other herbs saying these were good for health.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/22-firms-found-marketing-unauthorised-herbal-drinking-water
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/financial-express-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/drinking-water
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-supply
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-quality
[6] http://admin.indiaenvironmentportal.org.in/thesaurus/national-green-tribunal-ngt
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/bottled-water-industry
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/tamil-nadu
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/state-pollution-control-board-spcb-0