I've been working with a similar problem on my land in upstate NY. My engineer has suggested a sand filter bed which allows for a smaller drainfield. Don't know if they're allowed in Florida.

They work by filtering the effluent through several feet of sand encased in large buried box. Once the water goes through the sand, it's much cleaner and then flows into a drainfield. Since the filtered effluent is so much cleaner, you can get away w/ a smaller gravel bed. It's more expensive though. I've been told to budget $15-20,000 for a 3 bedroom capable system.

An aerobic tank system will digest more of the ‘bad stuff’ and produce a cleaner effluent. This cleaner waste water requires a smaller drain field. You’ll spend more on the tanks (and maybe a pump), but you’ll save on excavation.

I think a system like this was described in Dwell for the Dwell House II project. Look in back issues and you will find it.

I have looked into a couple alternatives. One is the Eljen system (www.eljen.com) which I really thought would help get the drain field size reduced (as they are normally get up to 50% reduction) but based on the size and the normal quick perk of the sandy soil we have near the beach in NW Florida, they said there was little chance of reduction besides the fact the FL does not allow such a system (which is also crazy since they are so wetland concious). I have thought about an aerobic system and thank you for your suggestion. I will go back to my past Dwells. I do not know a lot about these and especially if they are used (or allowed) in the area. I hear they need more maintenance.

Here is a good reference with some case studies:

http://www.septicaeration.com/technical.htm