Look into theBRAC Systems line of products.
I currently have only specified and had installed their Grey Water system for residential homes.
In conjunction with their grey water system, they also manufacture Black Water Treatment and Rainwater Treatment systems.
For more information:
Read "I need suggestions for greywater systems and water-efficient toilets." a Q&A answered by Jason Kliwinski.
Also, read "I can't find anyone who can install a rainwater collection system. I have plumbed my house to use rainwater for flushing." a Q&A answered by Harold Remlinger.