Waste water treatment systems in apartments

Many apartments in cities are setting up waste water treatment plants to recycle  waste water and use it for non-potable purpose.

What are the various systems available in India?
What is the average cost of treated waste water per kilo-litre in each of these systems?

Vishwanath Srikantaiah
The Rainwater Club, www.rainwaterclub.org
Arghyam, www.arghyam.org