Self contained dish water grey water system

I have a very specific problem.  I need to treat dish water in an above ground system ie. something I can fit in a box or tub.  The water would then go onto the garden.  There would seldom be more than 2 sinks worth a day say 6 gallons, 25 litres.  It needs to be cheap, cheap, cheap

Are there any free plans or general approaches that would suit this situation.

Thanks

Abe has a nice system,check it out here:
http://velacreations.com/blog/gray-water-filter/

thanks for that