Never heard of it. The only thing a search found was this: http://www.inspectapedia.com/septic/altwetland.htm
You need to hold the water somewhere -- whether it is a tank, a wetland, or a greenhouse just to settle stuff out. The classic system does anerobic treatment in the tank, so water needs to stay there for a while (therefore it is large). If you have a good disinfection system, you could probably get by with a small settling tank and have the disinfection system do all the work.
Even if such a system exists, you'll need your local health authority to approve it.