there are 2 low cost ...
Published by balbir singh, researcher on water for agricultural irrigation
there are 2 low cost methods of harvesting grey water for household use
1. by a ozonater which i have costing RS 5,000 connected by a pipe to a 20 liter plastic water jar which purifies this in 30 minutes-a bigger model could also be made
2. a better method is to attach a UV WATER FILTER connected to the kitchen tap the bulk purchase price of which is about US $ 10 EACH but may retail at about US $ 30 which gives water @ 1 liter per second with zero e-coli with a optional porus filter if there are particles in the water