My washing machine at home uses 2
pass washing:
1. detergent and water for cleaning
2. water for rinsing
Centrifugal force is used to spin
off the excess moisture in both
pass.
Using the great water pressure
created by the spinning, the
waste water generated in the
first pass may be
forced through
a membrane filtering system and
reused for the rinsing pass.
I know that reverse osmosis is
used to recycle waste water for
drinking, but I don't know if
some other cheaper filtering
system exists.
Hope that'll help save some water
bill and help a little in
conserving our environment.