Queries regarding demineralizing plant for a residential project in Mumbai, Maharashtra

My client is erecting a 50 stories building with LEED platinum rating in  central Mumbai, and we are planning a Demineralizing plant to minimize the reject. Since Demineralizing plant normally are used within the pharmaceutical industry, there's not much information about Demineralizing for residential potable use and therefore the following questions.
1) What type of Demineralizing plant can be used for potable use?
2) Which regulations are recommendable to follow for acid storage?
3) Brief calculations shows that we'll have around 1 ton of acid to be stored and injected into the purified water to re-establish an appropriate mineral content for drinking purpose. What guidelines to follow for the handling, storage & disposal of example acid next to the plant? We have tried to scan EPA but without luck.
4) Do you agree that a Demineralizing plant is an environmental and economic solution for water treatment for residential use?

Thanking you for your expertise and time,

Lars Kjeldsen
Director, Advanced Infrastructure and Environment