Bangalore, March 19 2018: Summer is here -- and most of us  won't stir out without carrying a bottle of drinking water.  Bottled mineral water is a wasteful expenditure on a regular basis -- but what to do?   Few cities offer  safe drinking water from the tap.  A team of innovators in Seattle, Washington ( US)  -- Halosource -- recently crowd-sourced  a drinking water bottle with a purification unit that screws into the neck.  It is called Astreawater Mobi-Pure aqua  It consists of a  3-stage  purifier cartridge that   meets the USA National Sanitation Foundation Standards to  remove  heavy metals  like lead and arsenic;    chemicals like chlorine and benzene as well as  bacteria and viruses  like E-coli and Norovirus.  
You can fill the bottle from the tap and drink  straight:  the cartridge does the  purifying, in real time.   The bottle as sold in India is food grade  plastic, but a steel version appears to be under  crowdfunding  in the US.
Each cartridge is good for about 100 days or 375 litres. The Astreawater bottle  costs Rs 1099 on Amazon and replacement cartridges, around Rs 500.