Companies involved in water and sanitation services in India

I am interested in learning about companies that are playing a constructive role in improving the clean drinking and sanitary water supplies in India.  I read a lot about the criticism of Coca Cola, Veolia and other multi-nationals, but am interested in Indian companies that are profiting from providing the products and services needed by Indians.  I have been actively investing in companies that do this in China, but have found it much more difficult to support Indian companies.  Any suggestions you can provide me will be greatly appreciated.

David Ladensohn
The Water Fund, LLC